Facile Preparation of Mn2O3 Nanowires by Thermal Decomposition of MnCO3

Facile preparation of nanocrystalline Li 4Ti 5O 12and its high electrochemical performance as anode material for lithium-ion batteriesNaiqing Zhang a ,b ,⁎,Zhimin Liu c ,Tongyong Yang c ,Chenglong Liao c ,Zhijun Wang c ,Kening Sun a ,b ,⁎a Academy of Fundamental and Interdisciplinary Sciences,Harbin Institute of Technology,Harbin,150001,PR Chinab State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology,Harbin,150090,PR China cDepartment of Chemistry,Harbin Institute of Technology,Harbin 150001,PR Chinaa b s t r a c ta r t i c l e i n f o Article history:Received 21March 2011Received in revised form 31March 2011Accepted 31March 2011Available online 6April 2011Keywords:Lithium-ion battery AnodeSpinel Li 4Ti 5O 12Nanocrystalline Sol –gel processWe report a facile approach for synthesizing nanocrystalline Li 4Ti 5O 12via sol –gel process by employing a nonionic surfactant (EO)20(PO)70(EO)20tri-block copolymer (pluronic P123)as the chelating agent.Pure-phase Li 4Ti 5O 12(~100nm)with high crystallinity is obtained at a sintering temperature of 700°C.The cell assembled with this nanocrystalline Li 4Ti 5O 12presents high-rate capacity of 108mAh g −1at 40C .Furthermore,the cell exhibits excellent cycling stability,retaining over 97%of its initial capacity after 250charge/discharge cycles at varying rates.©2011Elsevier B.V.All rights reserved.1.IntroductionLithium-ion batteries (LIBs)are the most promising energy storage devices for both portable electronics and electric vehicles (EVs).One of the key safety issues in LIBs for EVs is the dendritic lithium growth on the conventional graphite anode surface at high charging current,owing to the relatively low Li +insertion potential of carbonous materials [1].Therefore,much attention has been paid on the development of new anode materials [2–4].Among them,spinel Li 4Ti 5O 12is regarded as a promising candidate due to its unique properties,such as its flat Li +insertion potential at about 1.55V versus Li +/Li,and near-zero structural change upon the intercalation/deintercalation of Li +[3,5].However,the low conductivity (10−9S cm −1)of Li 4Ti 5O 12results in poor rate capability [6].Many efforts have been taken to ameliorate its rate capability,including reducing particle size,doping Li 4Ti 5O 12with other metals or metal oxides,and coating Li 4Ti 5O 12with conductive materials [7–13].Among these methods,reducing particle size is an effective way to increase the electrode/electrolyte contact area and shorten the diffusion length of lithium ions and electrons,thus signi ficantly improving the rate capability [3,8].Sol –gel procedure is widely applied for nanoparticle synthesis,since it offers the possibility to control the reaction pathways on a molecular level,thus enabling the resulting nanoparticles with superior homoge-neity [14].Although there have been a few reports on preparing Li 4Ti 5O 12through sol-gel process [15–18],pure-phase and well-crystallized Li 4Ti 5O 12could only be obtained at sintering temperatures over 750°C,which would induce larger particle size (200–1000nm).Considering that the larger particle size can adversely affect the rate capability of Li 4Ti 5O 12,developing an effective sol-gel process to synthesize nanocrystalline Li 4Ti 5O 12at lower temperature is of great signi ficance.Nonionic surfactant (EO)20(PO)70(EO)20tri-block copolymer (P123)usually acts as a structure-directing agent to synthesize ordered mesoporous materials owing to the PEO –metal complexation interactions [19].To the best of our knowledge,there have been no reports on the use of P123as chelating agent to prepare spinel Li 4Ti 5O 12.In this paper,pure-phase and well-crystallized Li 4Ti 5O 12with an average particle size of 100nm was obtained via a sol-gel route by employing P123as the chelating agent.The as-prepared nanocrystalline Li 4Ti 5O 12was tested as an anode material for lithium ion battery,exhibiting high reversible capacity and good cycling performance even at high current densities.2.ExperimentalThe Li 4Ti 5O 12powder was synthesized via a sol –gel route using P123as the chelating agent.In a typical procedure,3.0g P123and 6mL HNO 3(65wt.%)were dissolved in 30mL anhydrous ethanol,subsequently 8.8ml titanate isopropoxide was added under vigorous stirring to obtain the solution A.2.45g Li(AC)2·2H 2O was dissolved into 25ml anhydrous ethanol to obtain the solution B,which was graduallyElectrochemistry Communications 13(2011)654–656⁎Corresponding authors at:Academy of Fundamental and Interdisciplinary Sciences,Harbin Institute of Technology,Harbin,150001,PR China.Tel./fax:+8645186412153.E-mail addresses:znqmww@ (N.Zhang),keningsun@ (K.Sun).1388-2481/$–see front matter ©2011Elsevier B.V.All rights reserved.doi:10.1016/j.elecom.2011.03.038Contents lists available at ScienceDirectElectrochemistry Communicationsj o u r n a l h o m e p a g e :w ww.e l s ev i e r.c o m /l o c a t e /e l e c o mdropped into solution A to get a clear solution.After continuous stirring for 5h,the mixed solution was aged at 60°C for 4days under static condition to form a gel.The gel was calcined at different temperatures (650°C,700°C,750°C)for 5h with a heating rate of 1°C min −1in air and then cooled to room temperature naturally in the furnace.The resulting samples were characterized by means of X-ray diffraction (XRD,Rigaku D/max-γB)with monochromated Cu K αradiation at a scanning rate of 2°min −1in the range of 10–70°.The morphology of the synthesized materials was examined using a scanning electron microscopy (SEM,Hitachi S4800)and the micro-structure of the powders was observed by a high resolution transmis-sion electron microscopy (HRTEM,Hitachi 7650)operating at 300kV.The anode film studied here was prepared by mixing the Li 4Ti 5O 12powder,carbon black and polyvinylidene fluoride with a weight ratio of 8:1:1in N-methyl pyrrolidinone.The slurry was coated onto an aluminum foil by the “doctor blade ”technique [20].The weight of active material was ~2mg cm −2.Coin type (CR2025)test cells were assembled in an argon-filled glove box (Mbraun)using two porous polypropylene films as a separator,1M LiPF 6in ethylene carbonate,diethyl carbonate and ethylmethyl carbonate (EC/DMC/EMC,1:1:1vol)as electrolyte,and Li foil as the counter and reference electrodes.Constant current charge/discharge was performed at various rates within a voltage window of 1–2.5V (versus Li +/Li).Electrical impedance spectroscopy (EIS)experiments were carried out on a Parstat 2273advanced electrochemical system in the frequency range mainly from1MHz to 50mHz at an amplitude of 10mV.Before EIS measurements,all samples were charged to the same voltage of 1V.3.Results and discussionFig.1shows XRD patterns of Li 4Ti 5O 12calcined at different temperatures.For the sample calcined at 650°C,the rutile TiO 2phase is detected in the XRD pattern besides the main spinel structure of lithium titanate (JCPDS Card No.49–0207),while for the samples calcined at 700°C and 750°C,the pattern can be absolutely indexed to the spinel structure.By using the Scherrer's equation,the mean crystalline size is estimated to be 71,98and 151nm for the samples prepared at 650,700,and 750°C,respectively,implying the gradually growth of the particle size along with increasing temperature.In the strong acid condition of our experiment,the alkylene oxide segments of P123could form crown-ether-type complexes with Ti 4+and Li +through coordination bonds [19],bringing the reaction partners suf ficiently close together.Therefore,a pure-phase Li 4Ti 5O 12could be obtained at a relative low temperature of 700°C.Representative microstructures of the Li 4Ti 5O 12powder calcined at 700°C are presented in Fig.2.A typical SEM image in Fig.2a shows that the sample has a cubic morphology and a uniform particle size distribution.The TEM image in the inset of Fig.2a indicates that the particle size of Li 4Ti 5O 12ranges from 90to 110nm,which is in agreement with the XRD result.As depicted in the HRTEM image (Fig.2b),the crystalline region with clear lattice fringes has a inter-planar spacing of about 0.48nm,consistent with (111)atomic planes of the spinel structure.The SAED pattern taken along the (111)zone axis (inset of Fig.2b)further indicates the formation of a highly crystallized spinel phase,which can greatly improve the crystallographic-structure stability and charge/discharge cycling ability of the Li 4Ti 5O 12anode [21].To evaluate the high-rate performance of the nanocrystalline Li 4Ti 5O 12calcined at 700°C,we firstly measured the speci fic capacities at different charge/discharge rates (i.e.,from 1C to 60C ).As shown in Fig.3a,although the speci fic capacity drops along with increasing the charge/discharge rate,the Li 4Ti 5O 12anode exhibits relatively high speci fic capacity at all charge/discharge rates (1C :180mAh g −1;5C :165mAh g −1;10C :150mAh g −1;20C :141mAh g −1;40C :108mAh g −1;60C :84mAh g −1,respectively).These values are much higher than those exhibited by bulk samples prepared by solid state reaction as shown in Fig.3b.We further carried out cycle testing,in which the cell was progressively charged and discharged in series stages with the charge/discharge rate from 5C to 30C .For each stage,the process was taken with 50cycles.As shown in Fig.4,the discharge capacity stays very stable in each stage.After 250varying charge/discharge cycles,the10203040506070750 oC700 oC650 oC2θ (degree)**I n t e n s i t y (a .u .)* Rutile TiO 2*SFig.1.X-ray diffraction patterns of standard spinel Li 4Ti 5O 12(JCPDS Card No.49–0207,noted as S)and the samples calcined at differenttemperatures.Fig.2.Morphology of nanocrystalline Li 4Ti 5O 12:(a)representative scanning electron micrographs (SEM)image of Li 4Ti 5O 12(the inset shows HRTEM image);(b)high-resolution transmission electron microscopy (HRTEM)image of Li 4Ti 5O 12(the inset shows the SAED pattern for Li 4Ti 5O 12).655N.Zhang et al./Electrochemistry Communications 13(2011)654–656discharge capacity was 160mAh g −1,which was less than 3%discharge capacity loss (165mAh g −1in the first cycle).Meanwhile,the coulombic ef ficiencies approach 100%even at the identical charge and discharge rates (right ordinate of Fig.4).As compared to the literature results [7–13,15–17],both rate capability and cycling performance of our pure-phase Li 4Ti 5O 12are signi ficantly improved,owing not only to the nano-sized particles increasing effective interfacial reactivity and shortening the diffusion length of lithium ions and electrons,but also to the highly crystallized spinel phase keeping the structure integrity during the Li +intercalation and deintercalation process and accelerat-ing the lithium ions and electrons diffusion in solid bulk phase.In addition,impedance analysis was further carried out after various numbers of cycles (including the 1st,50th,200th,and 250th).As shown in the inset of Fig.4,the EIS spectra consist of a semicircle and a straight line,referring to the charge transfer reaction (R ct )and the diffusion of Li +in the bulk electrode [12],respectively.During our experiment,the values of R ct are all lower than 40Ω,which is in agreement with the excellent electrochemical performance of nanocrystalline Li 4Ti 5O 12.4.ConclusionsTo summarize,nanocrystalline spinel Li 4Ti 5O 12was prepared via a novel sol-gel process by employing P123as the chelating agent.Pure-phase and high-crystallinity Li 4Ti 5O 12with an average particle size of 100nm is obtained at a sintering temperature of 700°C.The Li 4Ti 5O 12anode shows a capacity of 108mAh g −1at the charge/discharge rate of 40C ,and retains over 97%of its initial capacity after 250charge/discharge cycles at varying rates.The excellent rate capability and cycling performance of Li 4Ti 5O 12anode is mainly attributed to the merits of nanosized particles and the high crystallinity of spinel Li 4Ti 5O 12.Thus,the nanocrystalline Li 4Ti 5O 12derived from this preparation will be an attractive anode material for high-power lithium-ion batteries.AcknowledgementsThis work was financially supported by the Funds for Creative Research Groups of China (No.50821002).References[1]S.S.Zhang,J.Power Sources 161(2006)1385.[2]P.Poizot,ruelle,S.Grugeon,L.Dupont,J.M.Tarascon,Nature 407(2000)496.[3] A.S.Arico,P.Bruce,B.Scrosati,J.M.Tarascon,W.Van Schalkwijk,Nat.Mater.4(2005)366.[4] C.K.Chan,H.L.Peng,G.Liu,K.McIlwrath,X.F.Zhang,R.A.Huggins,Y.Cui,Nat.Nanotech.3(2008)31.[5]T.Ohzuku,A.Ueda,N.Yamamoto,J.Electrochem.Soc.142(1995)1431.[6]S.Scharner,W.Weppner,P.Schmid-Beurmann,J.Electrochem.Soc.146(1999)857.[7]Y.F.Tang,L.Yang,Z.Qiu,J.S.Huang,mun.10(2008)1513.[8] A.S.Prakash,P.Manikandan,K.Ramesha,M.Sathiya,J.-M.Tarascon,A.K.Shukla,Chem.Mater.22(2010)2857.[9]H.Ge,N.Li,D.Li,C.Dai,D.Wang,mun.10(2008)1031.[10] D.Capsoni,M.Bini,V.Massarotti,P.Mustarelli,S.Ferrari,G.Chiodelli,M.C.Mozzati,P.Galinetto,J.Phys.Chem.C.113(2009)19664.[11]S.Huang,Z.Wen,X.Zhu,Z.Gu,mun.6(2004)1093.[12]H.Liu,Y.Feng,K.Wang,J.Xie,J.Phys.Chem.Solids 69(2008)2037.[13]H.-K.Kim,S.-M.Bak,K.-B.Kim,mun.12(2010)1768.[14]I.Bilecka,M.Niederberger,Electrochim.Acta 55(2010)7717.[15]Y.Hao,i,Z.Xu,X.Liu,X.Ji,Solid State Ionics 176(2005)1201.[16]M.Venkateswarlu,C.H.Chen,J.S.Do,C.W.Lin,T.C.Chou,B.J.Hwang,J.PowerSources 146(2005)204.[17]J.Wang,X.Liu,H.Yang,X.Shen,J.Alloys Compd.509(2011)712.[18]K.Dokko,J.Sugaya,H.Nakano,T.Yasukawa,T.Matsue,K.Kanamura,Electrochem.Commun.9(2007)857.[19]P.Yang,D.Zhao,D.I.Margolese,B.F.Chmelka,G.D.Stucky,Nature 396(1998)152.[20]T.Y.Yang,K.N.Sun,Z.Y.Lei,N.Q.Zhang,ng,J.Alloys Compd.502(2010)215.[21]J.C.Arrebola,A.Caballero,M.Cruz,L.Hernán,J.Morales,E.R.Castellón,Adv.Funct.Mater.16(2006)1904.02550751001251501751.001.251.501.7502550751001251501751.001.251.501.7560C 40C 20C 1Cnanocrystal LTOab10C 5C 20C 10C 5C 1CSpecific capacity (mAh g -1)bulk LTOP o t e n t i a l (V v s . L i +/L i )Fig.3.Capacity –voltage pro files between 1V and 2.5V at different current rates for a)nanocrystalline Li 4Ti 5O 12synthesized by the sol –gel approach and b)bulk Li 4Ti 5O 12synthesized by solid-state method.Cycle numberD i s c h a r g e c a p a c i t y (m A h g -1)E f f i c i e n c y (%)Fig.4.Discharge capacity and coulombic ef ficiency versus cycle number plot of Li/Li 4Ti 5O 12at different current rates (5C –30C ),the inset shows EIS data at different stages.656N.Zhang et al./Electrochemistry Communications 13(2011)654–656。

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纳米抗微生物喷雾敷料用于预防Tenckhoff导管出口部位感染有效性的初步报告对于大多数接受腹膜透析（PD）的患者而言，有证据显示，患者满意度和生活质量得到持续提高（1）。

然而，Tenckhoff导管（TC）可成为感染和腹膜炎的一个潜在来源。

如没有处理好出口部位感染（ESI），可导致腹膜炎或者需要拔除TC管（2）。

腹膜炎是腹膜透析患者死亡的一个众所周知的原因（3）。

因此，因透析通路失败而导致的治疗暂停可能会影响患者的整体健康状况。

出口部位常规护理的目的是为了预防出口部位感染。

针对出口部位感染的预防有大量的资料，推荐了多种不同的方法。

各机构的实践指南和治疗方案各有不同，且没有得到充分评估。

然而已有大量关于出口部位感染预防的资料出版。

（4）。

最近几项试验研究证明了应用JUC物理抗微生物喷雾敷料（南京神奇科技开发有限公司，江苏南京）的疗效：喷洒在导管表面和尿道口可以有效预防患者下尿路感染（5，6），治疗口腔癌术后感染（7）、急诊科开放性伤口（8）、以及处理放射性急性皮肤损伤（9）。

它也可替代抗生素治疗耐甲氧西林金黄色葡萄球菌感染患者的伤口（10）。

JUC于2002年在中国发明，2006年被美国食品和药物管理局注册为敷料产品。

该喷雾剂由2％的有机硅季铵盐和98％蒸馏水构成，即使在与眼睛和粘膜接触的时候也可以安全应用。

其成分使用了纳米制造技术，但其抗菌机理尚未完全弄清楚，一些提出的机理涉及纳米粒子的物理结构，而其他机理涉及到抗菌金属离子从纳米粒子表面增强释放，与细菌产生相互作用并渗透(11)正确的出口部位护理对于降低TC管相关感染和后续导管破损是至关重要的。

在目前的实践中，通常建议患者在出口部位护理时使用传统的抗菌剂，0.05％洗必泰。

之前的研究显示，0.05%的洗必泰能减少伤口中的细菌量，并促进细胞生长（12）。

在这项研究中，将JUC喷雾剂应用于TC管出口部位，和常规护理的出口部位感染的发生率进行比较。

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