Recent progress in the development of Li2MnSiO4 cathode materials---1-s2.0-S0378775313019253-main
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中国5g发展对世界的影响英语作文In recent years, China has made significant progress in the development and deployment of 5G technology. This has not only transformed the country's digital landscape but also had a profound impact on the global telecommunications industry.Firstly, China's rapid advancements in 5G technology have positioned the country as a global leader in this field. Chinese companies such as Huawei, ZTE, and China Mobile have been at the forefront of 5G innovation, making substantial contributions to the development of standards and technologies. This has allowed China to gain a competitive edge in the global market and expand its influence in the telecommunications sector.Secondly, the widespread adoption of 5G technology in China has had a ripple effect on the global economy. The deployment of 5G networks has created new opportunities for industries such as autonomous vehicles, smart cities, and the Internet of Things. This has led to increased productivity, efficiency, and connectivity, drivingeconomic growth not only in China but also in othercountries that have adopted 5G technology.Furthermore, China's leadership in 5G development has raised concerns among some countries about security and privacy issues. The U.S. government, in particular, has raised national security concerns about Chinese companies like Huawei, citing potential risks of espionage and cyberattacks. This has led to tensions between China andthe U.S. and has sparked debates about the role of Chinese technology companies in the global marketplace.Overall, China's 5G development has had a significant impact on the world, shaping the future of telecommunications and digital innovation. As China continues to expand its 5G network and invest in new technologies, its influence on the global economy and technological landscape is only expected to grow.近年来,中国在5G技术的发展和部署方面取得了显著进展。
科技兴国英文作文1. Technology has played a crucial role in the development of many countries, including China. In recent years, China has made tremendous progress in the field of technology, and this has contributed significantly to the country's economic growth. The government has invested heavily in research and development, and this has led to the creation of innovative products and services that have helped to boost the country's economy.2. One of the key areas where technology has had a significant impact is in the manufacturing sector. China has become a global manufacturing hub, thanks to its advanced technology and skilled workforce. The country has been able to produce high-quality products at a lower cost, making it an attractive destination for businesses looking to outsource their manufacturing operations.3. Another area where technology has been instrumental in China's growth is in the field of e-commerce. Thecountry has the world's largest online population, and this has created a huge market for e-commerce platforms. Companies like Alibaba and have emerged as global leaders in this space, and they have been able to leverage technology to provide consumers with a seamless online shopping experience.4. In addition to manufacturing and e-commerce, technology has also played a significant role in the development of China's transportation infrastructure. The country has built an extensive network of high-speed railways, which has helped to connect different parts ofthe country and facilitate the movement of goods and people. This has had a positive impact on the country's economy, as it has made it easier for businesses to transport their products and for people to travel for work or leisure.5. Finally, technology has also had a significantimpact on China's education system. The government has invested heavily in digital education, and this has led to the creation of innovative educational tools and platforms. Students are now able to access high-quality educationalresources online, and this has helped to improve the overall quality of education in the country.In conclusion, technology has been instrumental in China's growth and development over the past few decades. From manufacturing to e-commerce, transportation to education, technology has helped to create innovative products and services that have contributed significantly to the country's economic growth. As China continues to invest in research and development, we can expect to see even more exciting technological advancements in the years to come.。
介绍中国的科技成果的英语作文China has made remarkable achievements in science and technology in recent years. From space exploration to artificial intelligence, China has made significant contributions to the global technological advancements.In the field of space exploration, China has successfully landed a rover on the far side of the moon, becoming the first country to do so. This demonstrates China's capability in space exploration and its commitment to advancing space technology. Furthermore, China has also launched its own space station and has plans for future manned missions to the moon and Mars.In the area of artificial intelligence, China has made substantial progress in developing AI technologies. Chinese companies are leading the way in AI research and development, and the country is investing heavily in AI education and infrastructure. China's AI advancements have the potential to revolutionize various industries, from healthcare to transportation.In addition, China is also a pioneer in the development of renewable energy technologies. The country is theworld's largest producer of solar panels and is making significant investments in wind and hydroelectric power. China's efforts in renewable energy have not only helped to reduce carbon emissions but also have positioned the country as a global leader in sustainable energy solutions.Moreover, China has also made significant strides in the field of biotechnology, with breakthroughs in gene editing and pharmaceutical research. Chinese scientists have made significant contributions to the understanding of genetic diseases and have developed innovative treatments for various medical conditions.Overall, China's achievements in science and technology are a testament to the country's commitment to innovation and progress. The advancements made by Chinese scientists and engineers have not only benefited the country but have also made significant contributions to the globalscientific community.中国近年来在科技领域取得了显著的成就。
关于中国铁路发展的英语作文80词初中全文共3篇示例,供读者参考篇1China's railway development has been extraordinary in recent years. With the high-speed rail network expanding rapidly, China now boasts the world's largest high-speed rail system. The construction of the railway network has not only facilitated transportation within the country but also promoted economic development and social integration.One of the key reasons behind the success of China's railway development is the government's strong commitment to investing in infrastructure. The high-speed rail network, in particular, has been a major focus of investment, with billions of dollars being poured into building new lines and upgrading existing ones.Another important factor driving the growth of China's railway system is technological innovation. Chinese engineers have been at the forefront of developing cutting-edge technologies for high-speed rail, such as maglev trains and advanced signalling systems. These innovations have enabledtrains to travel at speeds of up to 350 km/h, making travel between major cities quick and convenient.The benefits of China's railway development are undeniable. Not only has it improved the efficiency and convenience of transportation, but it has also created numerous jobs and driven economic growth in the regions through which the railways pass. In addition, the environmental benefits of high-speed rail, such as reducing carbon emissions from cars and planes, are significant.In conclusion, China's railway development is a shining example of how investment in infrastructure and technology can drive economic growth and social progress. As the country continues to expand its high-speed rail network, it is poised to become a global leader in railway technology and transportation.篇2The development of China's railway system has been remarkable in recent years. With the government's strategic investment and continuous modernization efforts, the country now boasts one of the world's most extensive and efficient rail networks.The rapid expansion of China's high-speed rail network has been a key highlight of its railway development. The introduction of high-speed trains has significantly reduced travel times between major cities, providing a convenient and fast mode of transportation for passengers. The advanced technology used in these trains ensures both safety and comfort for commuters.In addition to high-speed rail, China has also been focusing on improving its traditional railway infrastructure. The construction of new rail lines, upgrading of existing tracks, and modernization of stations have all contributed to the overall efficiency and reliability of the railway system.The development of China's railway system has not only benefited the country's domestic transportation needs but has also played a crucial role in promoting economic growth and regional connectivity. By connecting remote areas with major cities, the railway network has facilitated the movement of goods and people, supporting trade and tourism in the region.Looking ahead, China continues to invest in railway development, with plans for further expansion of its high-speed rail network and improvement of its overall railway infrastructure. As the country continues to grow and modernize, the railwaysystem will undoubtedly play a key role in supporting its development goals.篇3With the rapid economic development in China, the railway system has also seen significant growth and improvement over the years. The development of China's railway system has been a key factor in the country's economic growth and social progress.In recent years, China has invested heavily in the development of high-speed rail networks, making it one of the most advanced in the world. The high-speed rail network connects major cities across the country, reducing travel time and increasing efficiency for both passengers and freight transportation. This has not only facilitated economic development in China but also promoted regional integration and social cohesion.China's railway system has not only improved connectivity within the country but also enhanced connections with neighboring countries through international railway networks such as the Belt and Road Initiative. This has not only boosted trade and economic cooperation but has also promoted cultural exchanges and people-to-people connectivity.Furthermore, the development of China's railway system has also contributed to environmental sustainability by reducing carbon emissions and promoting green transportation. With investments in new technologies and renewable energy sources, China's railway system is becoming more energy-efficient and environmentally friendly.In conclusion, the development of China's railway system has played a crucial role in the country's economic growth, social progress, and environment sustainability. As China continues to invest in the expansion and improvement of its railway network, the benefits are expected to be even greater in the future.。
中国航天事业发言稿英文Ladies and gentlemen,Good morning. I am honored to stand here today to speak about the remarkable achievements and future prospects of China's aerospace industry.China's aerospace industry has experienced rapid development in recent years, driven by the government's strong support and the hard work of talented individuals within the sector. Through our continuous efforts, we have achieved great breakthroughs in various fields and made significant contributions to the scientific and technological progress of the country.Space exploration is an essential part of our aerospace industry. In 2003, China sent its first astronaut into space, marking a significant milestone in the history of our nation's space endeavor. Since then, we have made steady progress, with multiple manned space missions successfully completed, including the historic Chang'e lunar exploration program.In 2019, China became the first country to successfully land a spacecraft, Chang'e-4, on the far side of the moon. This achievement not only demonstrated China's advanced space exploration capabilities but also expanded our understanding of the moon's geology and provided valuable data for future lunar missions.Looking ahead, China is committed to further exploring the mysteries of outer space. We are working on the development ofthe Chang'e-5 lunar mission, which aims to bring back samples from the moon for analysis. Additionally, we are planning for a manned mission to Mars in the future, which will undoubtedly be a challenging but exciting endeavor for our astronauts.The aerospace industry not only plays a crucial role in space exploration but also has a significant impact on our daily lives. Satellites have become an essential part of our communication, navigation, and weather forecasting systems. China has successfully launched a series of satellites, including the Beidou Navigation System, which provides high-precision positioning and timing services not only to China but also to the world. This achievement demonstrates our commitment to international cooperation and technological innovation.Moreover, China's aerospace industry has made remarkable achievements in the development of commercial space ventures. We have seen the emergence of private space companies in recent years, aiming to provide satellite launches, space tourism, and other related services. This not only promotes the growth of our domestic space industry but also opens up new opportunities for international cooperation and economic development.In addition to space exploration, China's aerospace industry is also actively engaged in the development of advanced aviation technologies. We are committed to creating a safe, efficient, and environmentally friendly aviation system. The development of the C919, China's first domestically built commercial aircraft, is a testament to our efforts in this direction. It represents a significant milestone for China's aviation industry and showcases our abilityto compete globally in aircraft manufacturing.China has also made significant progress in the development of hypersonic aircraft and reusable space vehicles. These technologies have the potential to revolutionize the future of aviation and space travel, making it faster, more efficient, and more sustainable. We believe that these advancements will not only benefit China but also contribute to the progress of the global aerospace industry.Furthermore, China's aerospace industry is committed to international cooperation and communication. We have actively participated in various international space conferences, forums, and exhibitions, exchanging our experiences, knowledge, and best practices with our international counterparts. We are willing to work together with other countries to promote the peaceful and sustainable development of space exploration and utilization, for the benefit of all humanity.In conclusion, China's aerospace industry has achieved remarkable progress and made significant contributions to space exploration, technological innovation, economic development, and international cooperation. We are confident that with our continuous efforts, determination, and support from all sectors, we will achieve even greater success in the future. Let us join hands and work together for a brighter future in the field of aerospace.Thank you.。
作文中国的高科技英语China's high-tech industry has been booming in recent years. From artificial intelligence to 5G technology, China has made significant advancements in various fields. The rapid development of high-tech industries has greatly contributed to China's economic growth and global influence.In the field of artificial intelligence, China has emerged as a major player. Chinese companies like Baidu and Tencent have developed advanced AI technologies that are used in various applications, such as facial recognitionand voice assistants. These technologies have greatly improved efficiency and convenience in people's daily lives.China has also made significant progress in the development of 5G technology. With the launch of 5G networks, China has become one of the leading countries in terms of network speed and connectivity. This has opened up new possibilities for various industries, such as autonomous driving and Internet of Things.In addition to AI and 5G, China has also made breakthroughs in other high-tech fields. For example, Chinese companies have developed advanced drones that are used in agriculture and delivery services. These droneshave improved efficiency and reduced costs in various industries.Furthermore, China has made significant advancements in the field of biotechnology. Chinese scientists have made breakthroughs in gene editing technology, which has the potential to revolutionize healthcare and agriculture. This technology has the potential to cure genetic diseases and increase crop yields.China's high-tech industry has not only benefited the country itself but also the world. Chinese companies have become major players in the global market, providing innovative products and services. This has increased competition and driven technological advancements worldwide.In conclusion, China's high-tech industry hasexperienced rapid growth and made significant advancements in various fields. From artificial intelligence to 5G technology, China has become a global leader in high-tech innovation. These advancements have not only benefited China's economy but also contributed to global technological progress.。
我国科研取得进步的英语作文英文回答:In recent years, China has made significant progress in scientific research. One example of this progress is the development of quantum communication technology. Scientists in China have successfully launched the world's first quantum satellite, Micius, which has enabled secure communication over long distances using quantum principles.Another area where China has excelled in scientific research is artificial intelligence. Chinese researchers have made breakthroughs in machine learning and deep learning algorithms, leading to advancements in areas such as facial recognition technology and autonomous vehicles.Furthermore, China has also made remarkable progress in space exploration. The successful landing of the Chang'e-4 lunar rover on the far side of the moon was a major achievement for the Chinese space program.Overall, these examples demonstrate the impressive strides that China has made in scientific research in recent years.中文回答:近年来,中国在科学研究方面取得了显著进步。
新视野大学英语第三版Book2课后翻译中国书法(calligraphy)是一门独特的艺术、是世界上独一无二的艺术瑰宝。
Chinese calligraphy is a unique art and the unique art treasure in the world.中国书法艺术的形成,发展与汉文字的产生与演进存在着密不可分的关系。
The formation and development of the Chinese calligraphy is closely related to the emergence and evolution of Chinese characters.汉字在漫长的演变发展过程中,一方面起着交流思想、继承文化的重要作用,另一方面它本身又形成了一种独特的艺术。
In this long evolutionary process, Chinese characters have not only played an important role in exchanging ideas and transmitting culture but also developed into a unique art form.书法能够通过作品把书法家个人的生活感受、学识、修养、个性等折射出来,所以,通常有“字如其人”的说法。
Calligraphic works well reflect calligraphers' personal feelings, knowledge, self-cultivation, personality, and so forth, thus there is an expression that "seeing the calligrapher's handwriting is like seeing the person".中国书法不仅是中华民族的文化瑰宝,而且在世界文化艺术宝库中独放异彩。
Oxygen Reduction Reaction on CathodeCatalystsThe development of clean energy has become an important global issue in recent years, and the fuel cells have been considered as one of the most promising candidates to replace traditional fossil fuels due to their high energy efficiency and low environmental impact. The cathode catalyst, which plays a key role in the oxygen reduction reaction (ORR), is one of the most important components of fuel cells. In this article, we will discuss the recent progress in the development of cathode catalysts for ORR.Overview of Oxygen Reduction ReactionORR is a crucial reaction in fuel cells, as it determines the electricity production efficiency and the durability of the fuel cells. The overall reaction equation of ORR is:O2 + 4e- + 4H+ → 2H2OAs shown in the equation, the ORR involves the reduction of the oxygen molecule (O2) into water (H2O) with the consumption of four electrons and four protons. The ORR process is kinetically slow, and requires a catalyst to reduce the activation energy barrier and increase the reaction rate.Cathode Catalysts for ORRThe cathode catalysts for ORR should possess high activity, selectivity, and durability. However, the currently used catalysts, such as platinum (Pt), suffer from several problems, including high cost, scarcity, and instability under harsh working conditions. Therefore, developing alternative catalysts with low cost, high activity, and excellent durability is urgently needed for the commercialization of fuel cells.One of the most promising alternatives for Pt-based catalysts is non-precious metal catalysts, which are usually composed of transition metals, such as Fe, Ni, Co, and their oxides. These catalysts have several advantages, such as low cost, high stability, andabundant resources. However, the overall catalytic activity and durability of these catalysts are still far from the requirements of commercial fuel cells.Another promising approach is to use composite catalysts, which combine the advantages of different types of catalysts and exhibit superior performance. For example, Pt-based composite catalysts, such as Pt-based alloys, PtCo/C, and PtNi/C, have been reported to show enhanced ORR activity and durability compared with single-component catalysts. In addition, nanostructured catalysts, such as core-shell nanoparticles and nanowires, have emerged as a new class of ORR catalysts with high surface area, low resistant, and improved mass transport.ConclusionIn summary, ORR is a crucial reaction in fuel cells, and the development of high-performance cathode catalysts for ORR is critical for the commercialization of fuel cells. Non-precious metal catalysts and composite catalysts are considered to be promising alternatives to traditional Pt-based catalysts. However, further research is still needed to optimize the catalyst design, improve the activity and durability, and reduce the cost of the fuel cells.。
最近这几年家乡的发展英文作文In recent years, the development of my hometown has been remarkable. With the implementation of various policies and the advancement of technology, my hometown has undergone significant changes in various aspects.Firstly, in terms of infrastructure, there have been massive improvements. New highways, bridges, and roads have been constructed, connecting different areas andfacilitating transportation. This has not only made it easier for locals to travel but has also attracted more tourists to visit our hometown.Secondly, the economy of my hometown has been growing steadily. With the support of the government, many new industries and businesses have emerged, providing job opportunities for the locals and boosting the overall income level. In addition, the agricultural sector has also seen advancements in technology and techniques, leading to increased productivity and better quality of produce.Furthermore, the education and healthcare systems have been upgraded. New schools, colleges, and training centershave been built, providing better educational resources for the residents. As for healthcare, new hospitals, clinics, and medical facilities have been established, ensuring that the locals have access to quality medical services.In terms of environmental protection, my hometown has also made great progress. Efforts have been made to reduce pollution and protect natural resources. More green spaces and parks have been created, making the environment cleaner and more pleasant for everyone.Overall, the development of my hometown in recent years has been remarkable, with improvements in infrastructure, economy, education, healthcare, and environmental protection.近年来,我的家乡的发展取得了显著成就。
中国科技现状英语作文China's Current Status of Science and Technology。
As one of the world's oldest civilizations, China has made remarkable achievements in science and technology. In recent years, China has been catching up with developed countries in terms of technological innovation and has become a major player in the global market.China's scientific research and developmentcapabilities have been greatly enhanced in recent years, thanks to the government's investment in science and technology. The country has established a number of world-class research institutions, such as the Chinese Academy of Sciences and the Chinese Academy of Engineering, which have made significant contributions to the development of science and technology.China has made great strides in high-tech fields such as artificial intelligence, quantum computing, and 5Gtechnology. In 2019, China launched its first 5G network, which is the largest in the world. Moreover, China has made significant progress in the development of electric vehicles, renewable energy, and biotechnology.In addition, China has made significant strides in space exploration. In 2019, China became the first country to land a spacecraft on the far side of the moon. The country is also planning to launch its own space station by 2022.However, China still faces many challenges in the field of science and technology. The country's innovation system is still in its infancy, and it lacks a strong culture of innovation. Moreover, China still lags behind developed countries in terms of basic research and the development of core technologies.To address these challenges, the Chinese government has launched a number of initiatives aimed at promoting innovation and technological development. For example, the government has established a number of innovation centersand high-tech industrial parks to encourage the development of new technologies. The government has also increased funding for research and development and has provided tax incentives for companies engaged in research and development.In conclusion, China has made remarkable progress in science and technology in recent years, but there is still a long way to go. The country needs to continue to investin research and development and create a more favorable environment for innovation. With the government's support and the efforts of its people, China is well-positioned to become a world leader in science and technology.。
中国新能源汽车英语作文China has made significant progress in the development and promotion of new energy vehicles (NEVs) in recent years. As the world's largest automobile market, China has been actively promoting the use of NEVs as part of its efforts to reduce air pollution and greenhouse gas emissions. In this essay, I will discuss the current status of China's NEV industry, the policies and incentives driving its growth, and the challenges it faces.The Chinese government has been a major driving force behind the development of NEVs in the country. In 2009, China launched a pilot program to promote the use of NEVs in 13 cities, providing subsidies to buyers and exempting them from certain taxes and fees. In 2010, the government introduced a subsidy program for NEV manufacturers to encourage the development and production of electric vehicles. These policies have helped China become the largest NEV market in the world, with over 1.3 million NEVs sold in 2020.In addition to government support, China's NEV industry has also benefited from technological advancements and a growing consumer demand for eco-friendly vehicles. Chinese NEVmanufacturers such as BYD, NIO, and Xpeng have made significant strides in developing high-quality electric vehicles with competitive prices, driving the adoption of NEVs in the country.Despite the rapid growth of China's NEV industry, it still faces several challenges. One of the biggest challenges is the lack of adequate charging infrastructure. While the Chinese government has been investing heavily in building charging stations, the number of stations still lags behind the increasing number of NEVs on the road. This has led to concerns about "range anxiety" among NEV owners, which could hinder the widespread adoption of electric vehicles.Another challenge facing China's NEV industry is the reliance on government subsidies. While subsidies have been instrumental in driving the growth of the NEV market, they have also led to concerns about overcapacity and market distortions. In 2019, the Chinese government announced plans to phase out subsidies for NEV manufacturers, prompting fears of a slowdown in the industry.In conclusion, China's NEV industry has made significant progress in recent years, driven by government support, technological advancements, and growing consumer demand.However, the industry still faces challenges such as inadequate charging infrastructure and overreliance on government subsidies. Addressing these challenges will be crucial for the sustainable growth of China's NEV industry.中国新能源汽车在近年取得了显著进展。
中国创新情况英语作文高一China's Innovation Situation。
In recent years, China's innovation capability has been greatly improved, and the number of patents and scientific papers has increased rapidly. China has become the world's second-largest spender on research and development, and its innovation-driven development strategy has been widely recognized.Firstly, China has made significant progress in the field of science and technology. China has established a number of world-class research institutions, such as the Chinese Academy of Sciences and the Chinese Academy of Engineering, which have made outstanding contributions to scientific research and technological innovation. The number of scientific papers published by Chinese researchers has ranked first in the world for several consecutive years, and the number of patents granted has also increased rapidly.Secondly, China has vigorously promoted the development of high-tech industries. In recent years, China hasinvested heavily in the development of high-tech industries, such as artificial intelligence, 5G, and new energy vehicles. Many Chinese companies, such as Huawei, Xiaomi, and BYD, have become world leaders in their respective fields, and have made significant contributions to the development of the global economy.Thirdly, China has actively promoted international cooperation in innovation. China has established a numberof international science and technology cooperation platforms, such as the Belt and Road Initiative Science, Technology and Innovation Cooperation Action Plan, to promote international cooperation in innovation. China has also actively participated in international scientific research programs, such as the International Thermonuclear Experimental Reactor project, and has made significant contributions to the development of global science and technology.However, China's innovation capability still faces many challenges. The quality of innovation needs to be improved, and the innovation environment needs to be optimized. In addition, China still lags behind developed countries in some key areas, such as basic research and core technologies. Therefore, China needs to continue to increase investment in innovation, deepen institutional reform, and enhance talent training to improve its innovation capability.In conclusion, China's innovation capability has made great progress in recent years, and has become an important driving force for China's economic and social development. With the continuous improvement of innovation capability, China will play a more important role in the global innovation system and make greater contributions to the development of human civilization.。
中国新能源汽车的发展前景英语作文全文共3篇示例,供读者参考篇1The Development Prospect of New Energy Vehicles in ChinaWith the increasing awareness of environmental protection and the government's push for clean energy vehicles, the development of new energy vehicles in China has been growing rapidly in recent years. New energy vehicles, including electric vehicles, plug-in hybrid vehicles, and fuel cell vehicles, are considered as an important solution to reduce greenhouse gas emissions and alleviate air pollution caused by traditional gasoline-powered vehicles.In terms of market growth, China has become the world's largest market for new energy vehicles. According to data from the China Association of Automobile Manufacturers, the sales of new energy vehicles in China reached 1.206 million units in 2020, accounting for more than half of the global new energy vehicle market. The Chinese government has also implemented various policies to promote the development of new energy vehicles,such as subsidies, tax incentives, and purchase restrictions on traditional vehicles in major cities.In terms of technology innovation, Chinese new energy vehicle manufacturers have made significant progress in recent years. Companies like BYD, NIO, and Xpeng Motors have emerged as strong players in the electric vehicle market and have gained recognition for their advanced technologies and sustainable practices. In addition, Chinese battery manufacturers such as CATL and BYD have also made breakthroughs in battery technology, reducing costs and improving the performance and range of electric vehicles.In terms of infrastructure, China has been investing heavily in building charging stations and expanding the network of charging facilities. As of 2021, China has the largest number of public charging stations in the world, with more than 1.3 million charging piles installed across the country. The government has also introduced policies to encourage the construction of charging infrastructure, such as mandating that residential and commercial buildings must install charging facilities.Despite the rapid growth of the new energy vehicle industry in China, there are still challenges that need to be addressed. One of the main challenges is the high upfront cost of newenergy vehicles compared to traditional gasoline-powered vehicles. Although the government offers subsidies to reduce the cost of new energy vehicles, the price gap still remains a barrier for many consumers. In addition, concerns about the limited driving range of electric vehicles and the availability of charging facilities also need to be addressed to further promote the adoption of new energy vehicles.In conclusion, the development prospect of new energy vehicles in China is promising. With strong government support, technological innovation, and infrastructure investment, the new energy vehicle industry in China is expected to continue growing rapidly in the coming years. As the world's largest market for new energy vehicles, China has the potential to become a global leader in sustainable transportation and contribute to the reduction of greenhouse gas emissions and air pollution.篇2The Development Prospects of China's New Energy Vehicles1. IntroductionWith the increasing global concern about environmental protection and sustainable development, the development of new energy vehicles has become a global trend. As the world'slargest automobile market, China has attached great importance to the development of new energy vehicles in recent years. This essay intends to discuss the development prospects of China's new energy vehicles.2. Current situation of China's new energy vehiclesChina has made significant progress in the development of new energy vehicles in recent years. According to data released by the China Association of Automobile Manufacturers (CAAM), the sales of new energy vehicles in China in 2020 reached 1.367 million units, accounting for 41.6% of the global market share. In addition, China has built the world's largest new energy vehicle charging infrastructure and has made substantial investments in research and development in this area. The Chinese government has also implemented various policies to promote the development of new energy vehicles, such as subsidies, tax incentives, and restrictions on traditional fuel vehicles in some cities.3. Development prospects of China's new energy vehiclesThere are several factors that contribute to the bright prospects of China's new energy vehicles. Firstly, the Chinese government is committed to promoting the development of new energy vehicles as part of its efforts to combat air pollution andreduce greenhouse gas emissions. With the growing awareness of environmental protection among Chinese consumers, the demand for new energy vehicles is expected to increase significantly in the coming years. Secondly, advancements in technology have made new energy vehicles more affordable, efficient, and convenient. The development of battery technology, charging infrastructure, and autonomous driving technology has made new energy vehicles more competitive with traditional fuel vehicles. Thirdly, the increasing competition in the new energy vehicle market has led to greater innovation and diversity in product offerings, which is expected to further drive the growth of the market.4. Challenges facing the development of China's new energy vehiclesDespite the promising prospects, there are still challenges facing the development of China's new energy vehicles. Firstly, the high cost of new energy vehicles remains a major barrier to widespread adoption. Although the cost of new energy vehicles has been decreasing in recent years, they are still more expensive than traditional fuel vehicles. The lack of consumer awareness and incentives to switch to new energy vehicles is also a challenge. Secondly, the limited range and charginginfrastructure for new energy vehicles are still a concern for consumers. While China has made significant investments in building charging stations, there is still a need for further expansion and improvement of the charging infrastructure. Finally, the competition from international automakers in the new energy vehicle market poses a challenge for domestic manufacturers. Foreign companies, such as Tesla, have been expanding their presence in China and have introduced competitive products, which could pose a threat to domestic manufacturers.5. ConclusionIn conclusion, the development prospects of China's new energy vehicles are promising, driven by government support, technological advancements, increasing consumer demand, and market competition. However, there are still challenges that need to be addressed, such as high costs, limited infrastructure, and foreign competition. With concerted efforts from the government, industry, and consumers, China's new energy vehicle market is expected to continue growing and contribute to a cleaner and more sustainable transportation system in the future.篇3The Development Prospect of China's New Energy Vehicles1. IntroductionWith the increasing demand for energy conservation and environmental protection, new energy vehicles (NEVs) have gained popularity in recent years. China, as the world's largest automobile market, has been actively promoting the development and adoption of NEVs. This essay aims to explore the development prospect of China's new energy vehicles.2. Current Situation of China's NEV MarketIn recent years, China has made significant progress in promoting NEVs. The government has issued a series of policies to support the development of NEVs, such as subsidies for buyers, tax incentives, and investment in charging infrastructure. As a result, the sales of NEVs in China have been growing rapidly. In 2020, the sales of pure electric vehicles (EVs) in China reached 1.2 million units, accounting for 41% of the global market share.3. Opportunities for DevelopmentThere are several reasons why China's NEV market has great potential for development. First, the Chinese government has set ambitious targets for NEV sales. China aims to have NEVs account for 20% of new car sales by 2025 and 50% by 2035. Toachieve these targets, the government will continue to provide policy support and invest in research and development. Second, China has a strong manufacturing base and a large market for automobiles. The presence of leading NEV manufacturers such as BYD, NIO, and Xpeng will further boost the development of the NEV industry in China.4. Challenges Facing China's NEV MarketDespite the promising prospects, China's NEV market also faces challenges. One of the biggest challenges is the lack of charging infrastructure. Although the government has invested heavily in building charging stations, there are still not enough charging facilities to meet the growing demand for NEVs. In addition, the high cost of NEVs is another barrier to mass adoption. Although the cost of NEVs has been declining in recent years, it is still higher than that of traditional vehicles. Moreover, the technology for NEVs is still not mature enough, with issues such as limited driving range and battery degradation.5. Strategies for Future DevelopmentTo overcome these challenges and promote the development of NEVs in China, several strategies can be considered. First, the government should continue to providepolicy support, such as subsidies, tax incentives, and regulations to encourage the adoption of NEVs. Second, more efforts should be made to improve charging infrastructure, including building more charging stations and standardizing charging protocols. Third, manufacturers should focus on R&D to improve the performance and reduce the cost of NEVs, such as developing better batteries and increasing the driving range.6. ConclusionIn conclusion, China's NEV market has great potential for development, given the strong government support, a large market for automobiles, and technological advancements. However, there are still challenges to be addressed, such as the lack of charging infrastructure and high cost. By implementing the right strategies and policies, China can further promote the development of NEVs and become a global leader in the NEV industry.。
noteably 例句
“notably”是一个副词,通常用来强调某事物是特别显著或重要的。
以下是一些使用“notably”的例句:
1.The company has made significant progress in recent years, notably in the development of new products.
近年来,该公司取得了显著进步,尤其是在新产品开发方面。
1.This region has a rich cultural heritage, notably its traditional music and dance.
这个地区拥有丰富的文化遗产,尤其是它的传统音乐和舞蹈。
1.Several factors contributed to the team's success, notably their excellent coaching and strong leadership.
几个因素促成了团队的成功,尤其是他们出色的教练和强大的领导力。
1.The book received positive reviews from critics, notably for its innovative approach to the subject matter.
这本书获得了评论家的积极评价,尤其是因为它对主题的创新性处理。
1.The scientist's research has had a profound impact on the field, notably in the area of genetic engineering.
这位科学家的研究对该领域产生了深远影响,尤其是在基因工程领域。
世界上最长的高速铁路网英语作文The World's Longest High-Speed Railway NetworkIn recent years, China has made remarkable progress in the development of its high-speed railway network. With the completion of numerous new lines and upgrades to existing ones, China now boasts the world's longest high-speed railway network, covering over 35,000 kilometers.The development of China's high-speed railway network can be traced back to the early 2000s when the government made it a priority to improve the country's transportation infrastructure. Since then, significant investments have been made in the construction of new lines, the purchase of high-speed trains, and the modernization of existing tracks. These efforts have paid off, as China now has the most extensive and advanced high-speed railway network in the world.One of the key features of China's high-speed railway network is its speed. With trains reaching speeds of up to 350 kilometers per hour, passengers can travel long distances in a fraction of the time it would take on conventional trains or by car. This has made high-speed rail an attractive option for bothbusiness and leisure travelers, contributing to the popularity of the network.In addition to its speed, China's high-speed railway network is known for its efficiency and reliability. Trains run on time, and delays are rare, thanks to the advanced signaling and control systems in place. This has helped to establish high-speed rail as a dependable mode of transportation for millions of people across the country.Furthermore, the network's extensive coverage has made it possible for travelers to reach virtually every corner of China by high-speed train. From major cities like Beijing and Shanghai to more remote areas in the west, passengers can easily access a wide range of destinations, making travel more convenient and accessible for all.The development of China's high-speed railway network has also had a positive impact on the economy. The construction and operation of the network have created jobs, stimulated growth in related industries, and improved connectivity between regions. This has led to increased trade and tourism, boosting local economies and promoting overall development in the country.Looking ahead, China continues to invest in the expansion and improvement of its high-speed railway network. Plans areunderway to add new lines, increase speeds, and enhance capacity to meet the growing demand for high-speed rail travel. With these efforts, China is set to maintain its position as the world leader in high-speed rail technology and infrastructure.In conclusion, China's high-speed railway network is a testament to the country's commitment to innovation, progress, and connectivity. With its impressive speed, efficiency, and coverage, the network has revolutionized travel in China and set a new standard for high-speed rail around the world. As the network continues to expand and evolve, it will undoubtedly shape the future of transportation and contribute to the country's ongoing development and success.。
中国在科技方面取得的成就英语作文China has made remarkable achievements in the field of technology in recent years. With strong government support, a growing number of innovative startups, and a large pool of talented engineers, China has become a global leader in areas such as artificial intelligence, biotechnology, clean energy, and space exploration.One of the key areas where China has made significant progress is in the development of artificial intelligence (AI). Chinese companies such as Baidu, Alibaba, and Tencent are at the forefront of AI research and have made breakthroughs in areas such as natural language processing, computer vision, and autonomous driving. In fact, China is now home to some of the world's most advanced AI research institutes, attracting top talent from around the world.In the field of biotechnology, China has also made significant strides in recent years. Chinese scientists have made breakthroughs in areas such as gene editing, stem cell research, and precision medicine. Chinese biotech companies are now leading the way in developing innovative treatments for a wide range of diseases, including cancer, Alzheimer's, and diabetes.China has also emerged as a global leader in clean energy technology. The country is investing heavily in renewable energy sources such as solar and wind power, and is now the world's largest producer of solar panels and wind turbines. China's investments in clean energy have not only helped to reduce the country's carbon emissions, but have also made clean energy more affordable and accessible to people around the world.In the field of space exploration, China has made significant progress in recent years. The country has successfully launched a series of manned and unmanned missions to space, including a mission to the moon and plans for a mission to Mars. China is also developing its own space station and has ambitions to send astronauts to the moon and beyond in the coming years.Overall, China's achievements in technology are a testament to the country's commitment to innovation and development. With a strong and vibrant tech sector, China is well positioned to continue to make significant contributions to the global technology landscape in the years to come.。
ReviewRecent progress in the development of Li2MnSiO4cathode materials R.J.Gummow*,Y.HeSchool of Engineering and Physical Sciences,James Cook University,Townsville4811,Australiah i g h l i g h t sWe review the published data on Li2MnSiO4as a lithium-ion battery cathode.The various synthesis methods used for Li2MnSiO4are examined.The structural form of the Li2MnSiO4products is highlighted.The electrochemical performance of various Li2MnSiO4samples is compared.Opportunities for future work are identified.a r t i c l e i n f oArticle history:Received9October2013 Received in revised form17November2013Accepted18November2013 Available online5January2014Keywords:Lithium-ion batteryCathodeLithium manganese silicate CapacityCell-cycling a b s t r a c tLithium ion batteries are under intense development to meet the performance specifications for con-sumer applications in portable electronic devices,electric vehicle batteries and stationary storage as back-up for intermittent renewable energy generation technologies.The most expensive and capacity-limiting component in these battery systems is the cathode material.Research has been directed to the development of novel cathode materials with high capacity and energy density and the lithium transition metal orthosilicates have been identified as possible high performance cathodes.In this review we focus on recent developments in the study of Li2MnSiO4and its derivatives as a lithium-ion battery cathode material.Preparation techniques,structural issues,conductivity enhancement and complex morphologies are discussed,to show the recent improvements and limitations in synthesis and elec-trochemical performance.Ó2013Elsevier B.V.All rights reserved.1.IntroductionSony released thefirst commercial lithium-ion battery in1990 containing a carbon anode and a lithium cobalt oxide(LiCoO2) cathode[1].Since then research has been conducted to modify the cell components to improve both safety and electrochemical ca-pacity,and to reduce cost.Much of the attention has focussed on the development of alternative cathode technologies,as the cath-ode capacity typically limits the cell capacity,and up to40%of the cell cost is derived from the cost of cathode raw materials[2].Due to market acceptance,lithium-ion batteries now dominate the portable electronics market.Concern for environmental protection, requiring reduction of green-house gas emissions,has led to new market opportunities for lithium-ion rge-scale appli-cations,for instance,in electric vehicles to replace internal combustion engines,and as stand-by storage for intermittent renewable energy technologies like solar and wind power,have become the focus of lithium-ion battery developers.These appli-cations place even more stringent performance requirements on batteries,and demand constant innovation in electrode materials [3,4].The continuous development of Li-ion battery cathodes since the1990’s has been driven by the need to1)maintain a high discharge voltage to maximize the energy density,2)extend the useful range of lithium insertion and extraction to maximize ca-pacity,and3)improve safety by reducing the reactivity of cathodes in the charged state,while striving to use non-toxic and cheap materials to minimize environmental impact and cost.The draw-back of lithium transition metal oxide cathodes,such as LiCoO2,in lithium ion batteries is two-fold;firstly,the range of reversible lithium extraction and insertion is limited by safety and stability issues,leading to only moderate practical capacities[5]and sec-ondly,the oxides are highly reactive and prone to O2release and potential thermal events when overcharged[6].Considerable im-provements in performance and safety have been achieved by*Corresponding author.Tel.:þ61747816223;fax:þ61747816788.E-mail addresses:Rosalind.gummow@.au(R.J.Gummow),yinghe.he@ .au(Y.He).Contents lists available at ScienceDirectJournal of Power Sourcesjournal h omepage:www.elsevier.co m/lo cate/jp owsour0378-7753/$e see front matterÓ2013Elsevier B.V.All rights reserved./10.1016/j.jpowsour.2013.11.082Journal of Power Sources253(2014)315e331using mixed transition-metal oxides e.g.Co,Ni and Mn in the1:1:1 atomic ratio to replace Co in LiCoO2,but practical capacities re-mains limited to approximately190mAh gÀ1[7,8].Polyanionic compounds such as phosphates and silicates were proposed in2002as possible alternatives to lithium transition metal oxide cathodes[9].This focus was motivated by the potential increased safety of these compounds compared to oxides,and the possibility of using cheaper,non-toxic metals such as Fe to replace Co and Ni.In the polyanionic units,the oxygen atoms are bound by strong,covalent bonds,reducing the risk of oxygen release in the charged state,and thus resulting in improved safety characteristics [10].Polyanionic compounds also offer the advantage that the electrochemical properties can be adjusted by altering the nature of the X atom in the XO4polyanions[11].LiFePO4is the most commercially successful polyanionic cath-ode material and was initially developed by Padhi and Goodenough in the1990’s[10,12].LiFePO4has excellent rechargeability and safety characteristics and is made from cheap,non-toxic pre-cursors.LiFePO4discharges through the Fe2þ/3þredox couple on a flat voltage plateau at w3.4V with95%of the theoretical capacity of 170mAh gÀ1[13].The gravimetric energy density of LiFePO4 (560Wh kgÀ1)is higher than that of LiCoO2(500Wh kgÀ1)but,due to the lower specific density of the material,the volumetric energy density is lower for LiFePO4(2000Wh lÀ1)compared to LiCoO2 (2600Wh lÀ1)[13].The drawback of the material is its poor intrinsic electronic conductivity,resulting in poor high current rate performance[14].This limitation has been overcome by coating nanoparticles of active material with electrically conductive layers, for example carbon[15,16].Excellent high rate performance of LiFePO4has also been reported by coating with amorphous Li4P2O7 e like phases with enhanced ionic conductivity[17].The lithium transition metal orthosilicates(Li2MSiO4,where M is a transition metal,for example,Fe,Co or Mn)were proposed as possible lithium-ion battery cathodes at the same time as the lithium transition metal phosphates[9].In the orthosilicates,the lithium and transition metal cations are situated in tetrahedral sites in a distorted hexagonal-close-packed oxygen array.A detailed general review of the silicate family of cathode materials was published by Islam et al.in2010[18].Li2MnSiO4is the material in this family that offers the greatest promise to deliver high capacity,high energy density cathode materials.In this review we focus on Li2MnSiO4and its derivatives with particular emphasis on the recent,advances that have been reported in the practical perfor-mance of these materials.2.Lithium manganese orthosilicate(Li2MnSiO4)Li2MnSiO4first attracted the attention of cathode developers when it was suggested that both lithium ions in each formula unit could potentially be extracted at moderate voltages,resulting in a high theoretical capacity of333mAh gÀ1[19,20].This process potentially utilizes both the Mn2þ/3þand Mn3þ/4þelectrochemical couples for the extraction of the1st and2nd lithium ions respec-tively.Although this is also theoretically possible for the Fe and Co analogues,in the case of Fe and Co,the Fe3þ/4þand Co3þ/4þcouples are predicted to be outside the voltage stability window of common electrolytes[11].The Ni analogue has not been synthesized experimentally but theory predicts prohibitively high voltages for lithium extraction from Li2NiSiO4.2.1.Polymorphism and structural considerationsThe transition metal orthosilicates are well-known to exhibit a wide variety of structural forms and Li2MnSiO4is no exception.All four known ambient temperature polymorphs have Li,Mn and Si cations in tetrahedral co-ordination in a distorted hexagonally close-packed oxygen array and differ only in the arrangement of the tetrahedra.The structures can all be related to either the a or b-Li3PO4structures[21].The orthorhombic forms(Pmn21and Pmnb) have two-dimensional pathways for Li-ion diffusion while the monoclinic forms(P21/n and Pn)are framework structures with Li-ion positions interconnected in three dimensions(Fig.1).Other framework structures,such as the spinel structure of Li4Ti5O12are dimensionally stable when Li is inserted and extracted,which permits excellent reversibility,and makes it possible to utilize most of the theoretical capacity in practice[22].Two-dimensional, layered structures such as the lithium transition metal oxides, however,tend to be destabilized when lithium is fully extracted and large dimensional changes result,leading to a limited range of lithium extraction in application and a reduction in thepracticalFig.1.Crystal structures of the four known ambient pressure polymorphs of Li2MnSiO4(a)Pmn21[19],(b)Pmnb[28],(c)P21/n[29]and(d)Pn[32].Li tetrahedra are shown in green, Mn tetrahedra in purple and Si tetrahedra in blue,red spheres represent oxygen atoms.(For interpretation of the references to colour in thisfigure legend,the reader is referred to the web version of this article.)R.J.Gummow,Y.He/Journal of Power Sources253(2014)315e331316capacity.It is clear,therefore,that various structural forms of Li2MnSiO4will potentially have different electrochemical perfor-mance due to the variety of the pathways for lithium-ion diffusion through the crystal lattice[18]and the different interconnections of the Mn and Si tetrahedra.In the analogous case of Li2FeSiO4,clear differences in electrochemical properties have been demonstrated for three different structural forms prepared under different con-ditions[23].The Pmn21structural form of Li2MnSiO4,first reported by Dominko et al.[19],has a distorted orthorhombic crystal structure analogous to the Li2FeSiO4structure reported by Nyten[24,25]. Synthesized products typically contain minor impurity phases of MnO and Li2SiO3.Initial Rietveld refinement of this structureshowed that it has a high degree of disorder which includes both partial exchange of Li and Mn cations as well as partial migration of the Li,Mn and Si atoms into vicinal tetrahedral sites across the basal plane of the tetrahedra in the hexagonally close packed oxygen lattice[19].This disorder is expected to be a disadvantage for Li-ion migration,as Mn ions in Li sites would block Li-ion diffusion pathways.More recent Rietveld refinement of high-quality single crystal XRD data for this polymorph,produced by hydrothermal synthesis,has shown that it gives a perfectly site-ordered structure for both Li and Mn[26].An idealized crystal structure diagram of this polymorph of Li2MnSiO4is shown in Fig.1(a).A second orthorhombic form with Pmnb symmetry was found, by theoretical calculations,to have very similar thermodynamic stability to the Pmn21form,making it difficult to prepare in phase-pure form[27].Recently,however,phase-pure Pmnb form Li2Mn-SiO4has been prepared[28].Rietveld refinement showed that this form showed no Li/Mn site/anti-site disorder potentially leading to good Li-ion diffusion properties.The high temperature form of Li2MnSiO4with monoclinic P21/n symmetry wasfirst prepared by Politaev et al.at1150 C[29]. Subsequently other synthesis routes to this structural form were reported by Arroyo-de Dompablo et al.(sol e gel synthesis)[27]and Mali et al.(hydrothermal synthesis)[30].Gummow et al.demon-strated that the P21/n polymorph could be stabilized by the partial substitution of Mn by Mg enabling synthesis of this form at tem-peratures of700 C[31].Recently a novel fourth structural form of Li2MnSiO4,with monoclinic P n symmetry,was prepared by ion-exchange from Na2MnSiO4[32].This polymorph was,however, unstable at elevated temperature and transformed to the ortho-rhombic Pmn21form at300 C.Table1gives the space group and lattice constants for the known,ambient pressure,polymorphs of Li2MnSiO4reported in the literature to date.Simulated reference XRD patterns(Cu K a radiation)for the three polymorphs of Li2MnSiO4that can be synthesized directly are given in Fig.2.The XRD pattern of the P n form was not included as the sample reported in Ref.[32]had a complex bimodal particle size distribution.2.2.Electronic conductivityThe drawback of the lithium transition metal orthosilicate cathodes is their very low electronic conductivity since the MO4 tetrahedra(where M¼Fe,Mn or Co)are surrounded by insulating XO4tetrahedra(where X¼Si in the case of the silicates)[27].This feature is common to all polyanionic compounds including LiFePO4, but the intrinsic conductivities of the silicates are significantly lower than the intrinsic conductivity of LiFePO4[33].The electronic conductivities of Li2FeSiO4and Li2MnSiO4are of the order of10À14 and10À16S cmÀ1at room temperature[33,34],respectively.They both increase by two orders of magnitude at60 C.No significant difference in electronic conductivity of Li2MnSiO4is anticipated for different structural forms,since isolated MnO4tetrahedra are pre-sent in all forms,and this is confirmed by thefinding that calculated band gaps are very similar for different polymorphs[27].Electronic conductivity can be enhanced by coating nanoparticles of active material with conductive layers,typically carbon.This strategy has been applied very successfully to LiFePO4and has also been used for Li2MnSiO4(see Section3).2.3.Ionic conductivityAlthough the electronic properties of the different polymorphs of Li2MnSiO4are similar,the ionic conduction properties are ex-pected to be significantly different due to the differences in the interconnection of lithium sites in different structural forms. Kuganathan et al.[35]calculated Li-ion diffusion pathways for the orthorhombic Pmn21and monoclinic P21/n forms of Li2MnSiO4and found that the barriers to Li-ion diffusion were lower in the P21/n form.Kuganathan et al.also demonstrated the curved,anisotropic pathways for lithium ion diffusion in Li2MnSiO4polymorphs.Cal-culations by Fisher et al.[36]for all four ambient pressure poly-morphs of Li2MnSiO4confirm that all are poor conductors of Li-ions with strong anisotropy in conduction.Poor ionic conductivity is likely to limit high rate performance of Li2MnSiO4cathodes.3.Synthesis techniques and electrochemical performanceIn this section the published studies of Li2MnSiO4cathodes are reviewed.Table2gives a summary of the synthesis conditions, particle size,and carbon content and emphasizes the crystallo-graphic structural forms of the Li2MnSiO4samples reported in the literature.The phase purity and the degree to which the structure has been investigated are also highlighted to indicate areas where Table1The space group and lattice constants of the known ambient pressure polymorphs of Li2MnSiO4cathodes.Space group a(A)b(A)c(A)b( )Pmn21[19] 6.3109(9) 5.3800(9) 4.9662(8)/Pmn21[30] 6.2762(9) 5.3355(8) 4.9614(9)/Pmnb[30] 6.3148(1)10.7742(5) 5.0138(2)/Pmnb[27] 6.30814(13)10.75946(22) 5.00909(10)/Pmnb[28] 6.30694(3)10.75355(4) 5.00863(2)/P21/n[29] 6.3368(1)10.9146(2) 5.0730(1)90.990P21/n[31] 6.3435(4)10.9208(7) 5.0818(5)90.982(2) P n[32] 6.3368(1)10.9146(2) 5.0730(1)90.987(1)Fig. 2.Simulated XRD patterns(Cu K a radiation)for the three polymorphs of Li2MnSiO4that can be prepared directly.Crystallographic data for the simulations were taken from Refs.(a)[19],(b)[28]and(c)[29].R.J.Gummow,Y.He/Journal of Power Sources253(2014)315e331317further structural studies are needed to clarify the nature of the electrochemically active species.Table 3summarizes the electro-chemical testing parameters recorded,to enable direct comparison of the performance of samples prepared and tested under various conditions.Figures that show the electrochemical charge/discharge pro files have been included in the text to illustrate,not only the capacities achieved,but also the voltage pro files and polarization.Practical application of cathode materials requires high energy density determined by both high capacity and high voltage over the discharge cycle.In the comparison of the electrochemical perfor-mance of various Li 2MnSiO 4samples,the capacity recorded above 2.5V has been quoted to illustrate that,in several cases,although very high discharge capacities are reported,much of this capacity is at a low voltage resulting in cathodes with a low overall energy density.3.1.Sol e gel synthesis and the Pmn21structural formIn early studies,Dominko and co-workers aimed to optimize the performance of Li 2MnSiO 4by minimizing the particle size and coating the particles with a conductive carbon layer [19,20,33],following the success of this strategy in optimizing the electro-chemical performance of LiFePO 4.Dominko et al.[19]used a modi fied Pechini sol e gel synthesis route to form the Pmn 21orthorhombic form of Li 2MnSiO 4(94.42wt.%)with minor impu-rities of MnO (5.13wt.%)and Li 2SiO 3(0.46wt.%).Primary particles were approximately 70nm in diameter with islands of amorphous carbon particles between them,but no clearly de fined nano-layer of carbon on the particle surface.When these materials were tested as cathodes in lithium cells only 0.6of the Li ions in the material were utilized reversibly on the first cycle and the revers-ible capacity faded rapidly to only 0.3Li ions on the 3rd cycle (Fig.3).The poor performance was attributed to both imperfect electronic wiring due to the lack of a discrete carbon coating,and also to the need for electrolytes stable well above 4.5V to allow full extraction of Li on charge.In a subsequent study by the same authors [20],an increase in the amount of the complexing agent resulted in smaller particles (20e 50nm)with a uniformly distributed carbon content of w 5wt.%.Electrochemical evaluation was performed using cath-odes of active material and an electrolyte based on LIBOB salt with an upper voltage cut-off of 4.2V to minimize the risk of electrolyte decomposition on charge.Room temperature cycling results were,however,comparable to those of the earlier study [19].To explore the performance at elevated temperature,cells were cycled at 60 C and gave an initial lithium extraction plateau near 4V with a capacity corresponding to the extraction of 1.5Li ions per formula unit,but this capacity was not reversible on discharge or on subsequent cycles.It was stated that it was not clear if the large capacity was due only to lithium extraction,or if there was some degree of irreversible electrolyte interaction with the active material that contributed to the observed capacity.Even after ball-milling to improve the distribution of compo-nents,and the contact between them,the improvement in ca-pacity was small and the polarization was only reduced by about 20mV.All samples showed a rapid loss of capacity with charge e discharge cycling corresponding to a 40mAh g À1loss after 10cycles.The authors stated that despite adopting the same strategy of particle size reduction and carbon coating used successfully to activate LiFePO 4,the performance of Li 2MnSiO 4cathodes remained surprisingly poor and cells showed rapid capacity fade with cycling.In order to understand this,ex-situ XRD studies of partially charged cathode samples were performed.The results showed no signi fi-cant change in peak position with changes in Li content,but aT a b l e 2(c o n t i n u e d )R e f .M e t h o d C o m m e n t o n m e t h o d P r e c u r s o r s C a l c i n a t i o n c o n d i t i o n s P r i m a r y p a r t i c l e s i z e (n m )C a r b o n c o n t e n t (w t %)F o r m a n d i m p u r i t i e s S h a o e t a l .[56]S p r a y p y r o l y s i s a n d w e t b a l l m i l l i n gL o w s y n t h e s i s t e m p e r a t u r e ,fin e p a r t i c l e s .L i N O 3,M n (N O 3)2$6H 2O ,F e (N O 3)3$9H 2O a n d T E O S i n d i s t i l l e d w a t e r +d r o p l e t s o f H N O 3t o h y d r o l y s e T E O S .A t o m i z e d a t .7M H z i n a n u l t r a s o n i c n e b u l i z e r .S p r a y p y r o l y s i s w i t h N 2c a r r i e r g a s (2d m 3m i n À1),he a t e d 400 C .W e t b a l l m i l l 8h w i t h 20w t %A B .600 C i n N 26520P m n 21R.J.Gummow,Y.He /Journal of Power Sources 253(2014)315e 331320Table3Summary of electrochemical performance of Li2MnSiO4.Reference Method Electrodeformulation Electrolyte Voltagelimits(V)Current rates Capacity(mAh gÀ1)CommentsDominkoet al.[19,20]Sol-gel Active material:Teflon binder:carbon black85:7:81M LiPF6inEC:DEC1:12e4.5C/30D1:100D5:50Dominkoet al.[20]Active material:carbon:PVDF80:10:100.8M LiBOB inEC:DEC(1:1byvolume)2e4.2C/20RT:D1:1660 C:D1:100Li’sDominkoet al.[33]Active materialþ10%AB,no binder0.8M LiBOB inEC:DEC(1:1byvolume)2e4.2C/20C1:232D1:140Large charge capacitynot recovered ondischarge2e4.5C/20C1:310D1:1502e4.2C/100C1:299D1:132Deng et al.[38]Active material:carbon black:PVDF80:10:101M LiPF6inEC:DMC1.5e4.810mAh gÀ1(w C/16)C1:200D1:140<1e capacityC5:120D5:100C10:100D10:85Belharouaket al.[39]Active:AB:PVDF75:15:101.2M LiPF6in3:7v/v EC:EMC1.5e4.810mAh gÀ1(w C/16)Coated:C1:190D1:135C5:140D5:130C10:125D10:120Milled:C1:175D1:115C5:125D5:120C10:105D10:100Liu et al.[55]Active:C:PVdF80:10:101M LiPF6in1:1v/v EC:DMC1.5e4.8C/30C1:219D1:132D10:1080.1C D1:126D10:870.5C D1:105D10:72Duncanet al.[32]Active:SuperS:graphite:PVDF80:5:5:101M LiPF6in3:7EC:DEC1.8e4.6Not given P n:Very similarperformance for twodifferent polymorphs.C1:100D1:120D5:110D10:100Pmn21:C1:120D1:105D5:100D10:97Li et al.[37]Solution Active:C:PVDF80:10:101M LiPF6/EC-DMC1:1wt%1.5e4.85mA gÀ1D1:2101st report of>1ecapacity on dischargeD5:170D10:14030mA gÀ1D1:180Capacity loss due toamorphization150mA gÀ1D1:135Aravindanet al.[42]Solid state Active:ketjenblack:TAB12:11:31M LiPF6inEC:DMC1:1v/v1.5e4.8C/20As-prepared:Steep discharge curveswith no plateau regionC1:97D1:45C5:50D5:30Heat treated:Very high carboncontentC1:110D1:100C5:105D5:100C10:105D10:100Kojimaet al.[47]MoltencarbonatefluxActive/C mixture:AB:PTFE80:13:71M LiPF6in EC/DMC1:1v/v1.5e4.510mA gÀ1Samples from hydroxides:Good plateau,lowpolarization,40%C insampleC1:170D1:155C2:160D1:150C5:145D5:135D10:120Manthiramet al.[44]Hydrothermal Active:C:PTFE75:20:51M LiPF6/EC-DMC1:11.5e4.7C/20a Room temperature:>1e capacityC1:280b D1:210150mAh gÀ1above2.5V at roomtemperature for D1C2:250D2:200D10:15055 C:Very rapid decay ofcapacity at55 CC1:340D1:245C2:260D2:220D10:65Aravindanet al.[46]Active:ketjenblack:TAB12:11:31M LiPF6inEC:DMC1:1v/v1.5e4.8C/20As-prepared:Steep discharge curveswith no plateau region.C1:97D1:45C5:50D5:30Heat treated:Very high carboncontent.C1:110D1:100C5:105D5:100C10:105D10:100Kuezmaet al.[45]Active:AB:PVDF75:15:101M LiBOB inEC:DEC1:1v/v2.0e4.5C/10Room temp:Rapid capacity loss at50 C after3cyclesC1:75D1:130C3:200D3:170(continued on next page) R.J.Gummow,Y.He/Journal of Power Sources253(2014)315e331321gradual loss of X-ray peak intensity was observed as the degree of Li extraction increased,with virtually no peaks visible for x >1in Li 2Àx MnSiO 4and no recovery of peaks after the 1st discharge cycle (Fig.4)[20].This indicated signi ficant,irreversible structural change when Li was extracted on the 1st charge cycle but it was noted that,even after the loss of crystallinity,the product continued to cycle with a capacity greater than 100mAh g À1.These results were con firmed by the parallel study of Li et al.[37]and subsequent in-situ studies by Dominko et al.[33].The tendency for the structure of Li 2Àx MnSiO 4to collapse when Li was extracted was investigated using DFT simulations by Kokalj et al.[34].It was found that the volume of the crystal lattice varied very little for 0 x 1(less than 2%)but dropped dramatically for x >1with a D V of À17and À27%for Li 0.5MnSiO 4and MnSiO 4,respectively.This finding was taken as a clear indication of struc-tural collapse for x >1,in agreement with the findings of Dominko et al.[20]and Li et al.[37].TEM observations of partially charged cathodes indicated some particles that were crystalline and some particles that were amorphous and this was interpreted as evi-dence for a phase separation mechanism for Li extraction as found in LiFePO 4[34].Table 3(continued )ReferenceMethodElectrode formulationElectrolyteVoltage limits (V)Current ratesCapacity (mAh g À1)Comments50 C C1:250D1:250C3:250D3:250D5:65Kempaiah et al.[48]PEDOT coated active:AB:PTFE 83:10:71M LiClO 4EC:DEC 1/1v/v1.5e 4.5C/20Room temp:Steep discharge curves.No plateau region.Most capacity below 2.5VC1:280D1:280D2:200D5:180D20:14040 C C1:300D1:300C2:290D2:280D5:275D20:230Rangappa et al.[50]PEDOT coated active:AB:PTFE 85:10:51M LiClO 4EC:DEC 1/1v/v1.5e 4.8C/50Room temp:Only 75mAh g À1above 2.5V at room temp.C1:150D1:130C2:190D2:21045 C Rapid decay in capacity after 20cyclesC1:350D1:350C2:350D2:350D10:300D20:300Devaraju et al.[51]PEDOT coated active material (10wt.%):carbon:PTFE1M LiClO 4in EC/DEC 1/1v/v1.5e 4.80.05C 2-step dischargea)Monodisperse nanoparticles 75:18:7a)C1:300D1:300w 140mAh g À1above 2.5V on D1C3:200D3:200C5:190D5:190b)30e 50nm sized particles 73:20:7b)C1:300D1:225w 125mAh g À1above 2.5V on D1C3:300D3:175C5:300D5:170c)Hierarchical nanostructures 69:24:7c)C1:300D1:280w 75mAh g À1above 2.5V on D1C3:300D3:250C5:300D5:240Shao et al.[56]Spray pyrolysis and wet ball-millingActive:PVDF:AB 70:10:201M LiPF 6in 1:1:v/v EC:DMC1.5e 4.80.05C ¼C/20C1:325D1:200Amorphizationcon firmed on the 1st charge to 4.8V.0.1C ¼C/10C1:275D1:185Poor capacity retention with cycling.D5:140D10:1201CC1:175D1:125D5:100D10:80a For C-rate calculations 1C ¼167mA g À1.bC1¼capacity on the 1st charge cycle,D1¼capacity on 1st dischargecycle.Fig.3.Voltage pro files of Li 2MnSiO 4cycled at room temperature and at a rate of C/30.Reprinted from Ref.[19]copyright (2006),with permission from Elsevier.R.J.Gummow,Y.He /Journal of Power Sources 253(2014)315e 331322Deng et al.[38]published a study of Li 2MnSiO 4prepared by sol e gel synthesis using TEOS as the SiO 2source and calcined in flowing Ar at 700 C.The product was indexed with the orthorhombic Pmn 21space group;although no detailed structural analysis was undertaken.The grain size was approximately 50nm.The initial discharge capacity was approximately 145mAh g À1and dropped off rapidly with cycling.The cycling results con firmed the earlier findings of Dominko et al.[20]despite the signi ficantly higher charge cut-off voltage of 4.8V.Belharouak et al.[39]prepared Li 2MnSiO 4by a sol e gel route using Li,Mn and Si acetates in acetic acid to form a gel product.After drying at 100 C,the gel was heated to 600,700and 800 C for 24h under He/H 2(3.5vol.%)gas flow.Cellulose was added to the reaction mixture as a carbon source leading to a final carbon con-tent of 7wt.%in the products.The optimum synthesis temperature to minimize impurities and produce Pmn 21form Li 2MnSiO 4was found to be 700 C.Samples consisted of micron sized aggregates of 100e 200nm primary particles after preparation and samples were milled for 4h in a ball-mill to reduce the size of the particles and improve electrochemical activity.While the as-prepared sample showed very poor electrochemical performance,the carbon-coated and ball-milled samples showed improved performance of 190and 135mAh g À1and 172and 155mAh g À1for the first charge and discharge capacities respectively (Fig.5).Once again rapid capacity fade with cycling was observed and,after 15cycles,only 98and 79mAh g À1discharge capacity was retained for the carbon-coated and ball-milled samples respectively.A similar study using adipic acid as the carbon source was published by Aravindan et al.[40]with dispersed 25e 30nm par-ticles of Li 2MnSiO 4and residual carbon from the synthesis.The initial discharge capacities reported were 161mAh g À1,dropping to 120mAh g À1after 50cycles,with steeply sloping discharge curves over the entire voltage range of 1.5e 4.8V.In 2009Dominko et al.[41]performed an in-situ XAS study to examine the oxidation state of Mn as a function of state of charge (orthorhombic Pmn 21structural form 83wt.%,15wt.%MnO and 1.9wt.%Li 2SiO 3).In-situ XANES measurements showed that,at 4.5V,only 60%of the Mn 2þhad been oxidized to Mn 3þ,that is,only 0.6Li ’s had been extracted from the structure.After discharging,all the Mn was found to be in the 2þstate,as found for the starting material,but XAFS measurements indicated that the localenvironment around the Mn cations was not completely reversible with cycling implying some irreversible structural change.The authors therefore found no evidence for >1Li extraction on charge and con firmed that some alteration in the crystal structure occurred when the sample was charged.In summary,results from this series of studies show that,despite the high theoretical capacities predicted,orthorhombic Li 2MnSiO 4with the Pmn 21structural form,did not perform as hoped.Initially this was believed to be due to the very low elec-tronic conductivity of the material.This explanation was soon dismissed,however,as,even after reduction of particle sizes to the range of 20e 30nm,and coating with carbon,the electrochemical performance remained disappointing.In fact,XAS results indicated that <1Li was extracted from Li 2MnSiO 4on charge,and the in-tensities of X-ray diffraction peaks dropped off rapidly when samples were delithiated electrochemically.This evidence of dra-matic structural change was con firmed by evidence of a change in crystallographic environment around the metal cations after cycling given by both NMR and EXAFS data.3.2.Ion exchange and the P n structural formIn 2011Duncan et al.[32]used an ion-exchange route to prepare the novel monoclinic P n form of Li 2MnSiO 4.The motivation for this study was the hope that the monoclinic form,with its three-dimensional framework structure,would be more stable to lithium extraction than the two-dimensional orthorhombic Pmn 21structure examined in earlier studies.The P n form of Li 2MnSiO 4was found to be metastable,transforming to the Pmn 21form when heated at 300 C,preventing conventional carbon-coating.The electrochemical cycling results for the P n form were very similar to those of the well-known Pmn 21form (Fig.6).Capacity fade was comparable for both forms,with 65and 70mAh g À1for the Pn and Pmn 21forms respectively after 50cycles.This was contrary to the expectation that,when Li is extracted,the framework structure of the delithiated P n form would be more stable than the delithiated,layered Pmn 21form.Fig. 4.X-ray diffraction patterns of compositions obtained with electrochemical oxidation of Li 2MnSiO 4-based composites.The value of x corresponds to expected chemical composition of the electrode that is based on the amount of charge passed through the cell.The remaining diffraction peak marked with asterisk denotes MnO impurity.Reprinted from Ref.[20]copyright (2007),with permission fromElsevier.Fig.5.Voltage pro files of (a)as-prepared Li 2MnSiO 4,(b)carbon-coated Li 2MnSiO 4,and (c)high-energy ball-milled Li 2MnSiO 4.Reprinted with permission from Ref.[39]copyright (2009)American Chemical Society.R.J.Gummow,Y.He /Journal of Power Sources 253(2014)315e 331323。