High energy emission from IGR J16320-4751

A review of advanced and practical lithium battery materialsRotem Marom,*S.Francis Amalraj,Nicole Leifer,David Jacob and Doron AurbachReceived 3rd December 2010,Accepted 31st January 2011DOI:10.1039/c0jm04225kPresented herein is a discussion of the forefront in research and development of advanced electrode materials and electrolyte solutions for the next generation of lithium ion batteries.The main challenge of the field today is in meeting the demands necessary to make the electric vehicle fully commercially viable.This requires high energy and power densities with no compromise in safety.Three families of advanced cathode materials (the limiting factor for energy density in the Li battery systems)are discussed in detail:LiMn 1.5Ni 0.5O 4high voltage spinel compounds,Li 2MnO 3–LiMO 2high capacity composite layered compounds,and LiMPO 4,where M ¼Fe,Mn.Graphite,Si,Li x TO y ,and MO (conversion reactions)are discussed as anode materials.The electrolyte is a key component that determines the ability to use high voltage cathodes and low voltage anodes in the same system.Electrode–solution interactions and passivation phenomena on both electrodes in Li-ion batteries also play significant roles in determining stability,cycle life and safety features.This presentation is aimed at providing an overall picture of the road map necessary for the future development of advanced high energy density Li-ion batteries for EV applications.IntroductionOne of the greatest challenges of modern society is to stabilize a consistent energy supply that will meet our growing energy demands.A consideration of the facts at hand related to the energy sources on earth reveals that we are not encountering an energy crisis related to a shortage in total resources.For instancethe earth’s crust contains enough coal for the production of electricity for hundreds of years.1However the continued unbridled usage of this resource as it is currently employed may potentially bring about catastrophic climatological effects.As far as the availability of crude oil,however,it in fact appears that we are already beyond ‘peak’production.2As a result,increasing oil shortages in the near future seem inevitable.Therefore it is of critical importance to considerably decrease our use of oil for propulsion by developing effective electric vehicles (EVs).EV applications require high energy density energy storage devices that can enable a reasonable driving range betweenDepartment of Chemistry,Bar-Ilan University,Ramat-Gan,52900,Israel;Web:http://www.ch.biu.ac.il/people/aurbach.E-mail:rotem.marom@live.biu.ac.il;aurbach@mail.biu.ac.ilRotem MaromRotem Marom received her BS degree in organic chemistry (2005)and MS degree in poly-mer chemistry (2007)from Bar-Ilan University,Ramat Gan,Israel.She started a PhD in electrochemistry under the supervision of Prof.D.Aurbach in 2010.She is currently con-ducting research on a variety of lithium ion battery materials for electric vehicles,with a focus on electrolyte solutions,salts andadditives.S :Francis AmalrajFrancis Amalraj hails from Tamil Nadu,India.He received his MSc in Applied Chemistry from Anna University.He then carried out his doctoral studies at National Chemical Laboratory,Pune and obtained his PhD in Chemistry from Pune University (2008).He is currently a postdoctoral fellow in Prof.Doron Aurbach’s group at Bar-Ilan University,Israel.His current research interest focuses on the synthesis,electrochemical and transport properties of high ener-getic electrode materials for energy conversion and storage systems.Dynamic Article Links CJournal ofMaterials ChemistryCite this:DOI:10.1039/c0jm04225k /materialsFEATURE ARTICLED o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 24 F e b r u a r y 2011P u b l i s h e d o n 23 F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0J M 04225KView Onlinecharges and maintain acceptable speeds.3Other important requirements are high power density and acceptable safety features.The energy storage field faces a second critical chal-lenge:namely,the development of rechargeable systems for load leveling applications (e.g.storing solar and wind energy,and reducing the massive wasted electricity from conventional fossil fuel combustion plants).4Here the main requirements are a very prolonged cycle life,components (i.e.,relevant elements)abun-dant in high quantities in the earth’s crust,and environmentally friendly systems.Since it is not clear whether Li-ion battery technology can contribute significantly to this application,battery-centered solutions for this application are not discussedherein.In fact,even for electrical propulsion,the non-petroleum power source with the highest energy density is the H 2/O 2fuel cell (FC).5However,despite impressive developments in recent years in the field,there are intrinsic problems related to electrocatalysis in the FCs and the storage of hydrogen 6that will need many years of R&D to solve.Hence,for the foreseeable future,rechargeable batteries appear to be the most practically viable power source for EVs.Among the available battery technologies to date,only Li-ion batteries may possess the power and energy densities necessary for EV applications.The commonly used Li-ion batteries that power almost all portable electronic equipment today are comprised of a graphite anode and a LiCoO 2cathode (3.6V system)and can reach a practical energy density of 150W h kg À1in single cells.This battery technology is not very useful for EV application due to its limited cycle life (especially at elevated temperatures)and prob-lematic safety features (especially for large,multi-cell modules).7While there are ongoing developments in the hybrid EV field,including practical ones in which only part of the propulsion of the car is driven by an electrical motor and batteries,8the main goal of the battery community is to be able to develop full EV applications.This necessitates the development of Li-ion batteries with much higher energy densities compared to the practical state-of-the-art.The biggest challenge is that Li-ion batteries are complicated devices whose components never reach thermodynamic stability.The surface chemistry that occurs within these systems is very complicated,as described briefly below,and continues to be the main factor that determines their performance.9Nicole Leifer Nicole Leifer received a BS degree in chemistry from MIT in 1998.After teaching high school chemistry and physics for several years at Stuyvesant High School in New York City,she began work towards her PhD in solid state physics from the City University of New York Grad-uate Center.Her research con-sisted primarily of employing solid state NMR in the study of lithium ion electrode materialsand electrode surfacephenomena with Prof.Green-baum at Hunter College andProf.Grey at Stony Brook University.After completing her PhD she joined Prof.Doron Aurbach for a postdoctorate at Bar-Ilan University to continue work in lithium ion battery research.There she continues her work in using NMR to study lithium materials in addition to new forays into carbon materials’research for super-capacitor applications with a focus on enhancement of electro-chemical performance through the incorporation of carbonnanotubes.David Jacob David Jacob earned a BSc from Amravati University in 1998,an MSc from Pune University in 2000,and completed his PhD at Bar-Ilan University in 2007under the tutelage of Professor Aharon Gedanken.As part of his PhD research,he developed novel methods of synthesizing metal fluoride nano-material structures in ionic liquids.Upon finishing his PhD he joined Prof.Doron Aurbach’s lithium ionbattery group at Bar-Ilan in2007as a post-doctorate and during that time developed newformulations of electrolyte solutions for Li-ion batteries.He has a great interest in nanotechnology and as of 2011,has become the CEO of IsraZion Ltd.,a company dedicated to the manufacturing of novelnano-materials.Doron Aurbach Dr Doron Aurbach is a full Professor in the Department of Chemistry at Bar-Ilan Univer-sity (BIU)in Ramat Gan,Israel and a senate member at BIU since 1996.He chaired the chemistry department there during the years 2001–2005.He is also the chairman of the Israeli Labs Accreditation Authority.He founded the elec-trochemistry group at BIU at the end of 1985.His groupconducts research in thefollowing fields:Li ion batteries for electric vehicles and for otherportable uses (new cathodes,anodes,electrolyte solutions,elec-trodes–solution interactions,practical systems),rechargeable magnesium batteries,electronically conducting polymers,super-capacitors,engineering of new carbonaceous materials,develop-ment of devices for storage and conversion of sustainable energy (solar,wind)sensors and water desalination.The group currently collaborates with several prominent research groups in Europe and the US and with several commercial companies in Israel and abroad.He is also a fellow of the ECS and ISE as well as an associate editor of Electrochemical and Solid State Letters and the Journal of Solid State Electrochemistry.Prof.Aurbach has more than 350journals publications.D o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 24 F e b r u a r y 2011P u b l i s h e d o n 23 F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0J M 04225KAll electrodes,excluding 1.5V systems such as LiTiO x anodes,are surface-film controlled (SFC)systems.At the anode side,all conventional electrolyte systems can be reduced in the presence of Li ions below 1.5V,thus forming insoluble Li-ion salts that comprise a passivating surface layer of particles referred to as the solid electrolyte interphase (SEI).10The cathode side is less trivial.Alkyl carbonates can be oxidized at potentials below 4V.11These reactions are inhibited on the passivated aluminium current collectors (Al CC)and on the composite cathodes.There is a rich surface chemistry on the cathode surface as well.In their lithiated state,nucleophilic oxygen anions in the surface layer of the cathode particles attack electrophilic RO(CO)OR solvents,forming different combinations of surface components (e.g.ROCO 2Li,ROCO 2M,ROLi,ROM etc.)depending on the electrolytes used.12The polymerization of solvent molecules such as EC by cationic stimulation results in the formation of poly-carbonates.13The dissolution of transition metal cations forms surface inactive Li x MO y phases.14Their precipitation on the anode side destroys the passivation of the negative electrodes.15Red-ox reactions with solution species form inactive LiMO y with the transition metal M at a lower oxidation state.14LiMO y compounds are spontaneously delithiated in air due to reactions with CO 2.16Acid–base reactions occur in the LiPF 6solutions (trace HF,water)that are commonly used in Li-ion batteries.Finally,LiCoO 2itself has a rich surface chemistry that influences its performance:4LiCo III O 2 !Co IV O 2þCo II Co III 2O 4þ2Li 2O !4HF4LiF þ2H 2O Co III compounds oxidize alkyl carbonates;CO 2is one of the products,Co III /Co II /Co 2+dissolution.14Interestingly,this process seems to be self-limiting,as the presence of Co 2+ions in solution itself stabilizes the LiCoO 2electrodes,17However,Co metal in turn appears to deposit on the negative electrodes,destroying their passivation.Hence the performance of many types of electrodes depends on their surface chemistry.Unfortunately surface studies provide more ambiguous results than bulk studies,therefore there are still many open questions related to the surface chemistry of Li-ion battery systems.It is for these reasons that proper R&D of advanced materials for Li-ion batteries has to include bulk structural and perfor-mance studies,electrode–solution interactions,and possible reflections between the anode and cathode.These studies require the use of the most advanced electrochemical,18structural (XRD,HR microscopy),spectroscopic and surface sensitive analytical techniques (SS NMR,19FTIR,20XPS,21Raman,22X-ray based spectroscopies 23).This presentation provides a review of the forefront of the study of advanced materials—electrolyte systems,current collectors,anode materials,and finally advanced cathodes materials used in Li-ion batteries,with the emphasis on contributions from the authors’group.ExperimentalMany of the materials reviewed were studied in this laboratory,therefore the experimental details have been provided as follows.The LiMO 2compounds studied were prepared via self-combus-tion reactions (SCRs).24Li[MnNiCo]O 2and Li 2MnO 3$Li/MnNiCo]O 2materials were produced in nano-andsubmicrometric particles both produced by SCR with different annealing stages (700 C for 1hour in air,900 C or 1000 C for 22hours in air,respectively).LiMn 1.5Ni 0.5O 4spinel particles were also synthesized using SCR.Li 4T 5O 12nanoparticles were obtained from NEI Inc.,USA.Graphitic material was obtained from Superior Graphite (USA),Timcal (Switzerland),and Conoco-Philips.LiMn 0.8Fe 0.2PO 4was obtained from HPL Switzerland.Standard electrolyte solutions (alkyl carbonates/LiPF 6),ready to use,were obtained from UBE,Japan.Ionic liquids were obtained from Merck KGaA (Germany and Toyo Gosie Ltd.,(Japan)).The surface chemistry of the various electrodes was charac-terized by the following techniques:Fourier transform infrared (FTIR)spectroscopy using a Magna 860Spectrometer from Nicolet Inc.,placed in a homemade glove box purged with H 2O and CO 2(Balson Inc.air purification system)and carried out in diffuse reflectance mode;high-resolution transmission electron microscopy (HR-TEM)and scanning electron microscopy (SEM),using a JEOL-JEM-2011(200kV)and JEOL-JSM-7000F electron microscopes,respectively,both equipped with an energy dispersive X-ray microanalysis system from Oxford Inc.;X-ray photoelectron spectroscopy (XPS)using an HX Axis spectrom-eter from Kratos,Inc.(England)with monochromic Al K a (1486.6eV)X-ray beam radiation;solid state 7Li magic angle spinning (MAS)NMR performed at 194.34MHz on a Bruker Avance 500MHz spectrometer in 3.2mm rotors at spinning speeds of 18–22kHz;single pulse and rotor synchronized Hahn echo sequences were used,and the spectra were referenced to 1M LiCl at 0ppm;MicroRaman spectroscopy with a spectrometerfrom Jobin-Yvon Inc.,France.We also used M €ossbauer spec-troscopy for studying the stability of LiMPO 4compounds (conventional constant-acceleration spectrometer,room temperature,50mC:57Co:Rh source,the absorbers were put in Perspex holders.In situ AFM measurements were carried out using the system described in ref.25.The following electrochemical measurements were posite electrodes were prepared by spreading slurries comprising the active mass,carbon powder and poly-vinylidene difluoride (PVdF)binder (ratio of 75%:15%:10%by weight,mixed into N -methyl pyrrolidone (NMP),and deposited onto aluminium foil current collectors,followed by drying in a vacuum oven.The average load was around 2.5mg active mass per cm 2.These electrodes were tested in two-electrode,coin-type cells (Model 2032from NRC Canada)with Li foil serving as the counter electrode,and various electrolyte puter-ized multi-channel battery analyzers from Maccor Inc.(USA)and Arbin Inc.were used for galvanostatic measurements (voltage vs.time/capacity,measured at constant currents).Results and discussionOur road map for materials developmentFig.1indicates a suggested road map for the direction of Li-ion research.The axes are voltage and capacity,and a variety of electrode materials are marked therein according to their respective values.As is clear,the main limiting factor is the cathode material (in voltage and capacity).The electrode mate-rials currently used in today’s practical batteries allow forD o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 24 F e b r u a r y 2011P u b l i s h e d o n 23 F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0J M 04225Ka nominal voltage of below 4V.The lower limit of the electro-chemical window of the currently used electrolyte solutions (alkyl carbonates/LiPF 6)is approximately 1.5V vs.Li 26(see later discussion about the passivation phenomena that allow for the operation of lower voltage electrodes,such as Li and Li–graphite).The anodic limit of the electrochemical window of the alkyl carbonate/LiPF 6solutions has not been specifically determined but practical accepted values are between 4.2and 5V vs.Li 26(see further discussion).With some systems which will be discussed later,meta-stability up to 4.9V can be achieved in these standard electrolyte solutions.Electrolyte solutionsThe anodic stability limits of electrolyte solutions for Li-ion batteries (and those of polar aprotic solutions in general)demand ongoing research in this subfield as well.It is hard to define the onset of oxidation reactions of nonaqueous electrolyte solutions because these strongly depend on the level of purity,the presence of contaminants,and the types of electrodes used.Alkyl carbonates are still the solutions of choice with little competition (except by ionic liquids,as discussed below)because of the high oxidation state of their central carbon (+4).Within this class of compounds EC and DMC have the highest anodic stability,due to their small alkyl groups.An additional benefit is that,as discussed above,all kinds of negative electrodes,Li,Li–graphite,Li–Si,etc.,develop excellent passivation in these solutions at low potentials.The potentiodynamic behavior of polar aprotic solutions based on alkyl carbonates and inert electrodes (Pt,glassy carbon,Au)shows an impressive anodic stability and an irreversible cathodic wave whose onset is $1.5vs.Li,which does not appear in consequent cycles due to passivation of the anode surface bythe SEI.The onset of these oxidation reactions is not well defined (>4/5V vs.Li).An important discovery was the fact that in the presence of Li salts,EC,one of the most reactive alkyl carbonates (in terms of reduction),forms a variety of semi-organic Li-con-taining salts that serve as passivation agents on Li,Li–carbon,Li–Si,and inert metal electrodes polarized to low potentials.Fig.2and Scheme 1indicates the most significant reduction schemes for EC,as elucidated through spectroscopic measure-ments (FTIR,XPS,NMR,Raman).27–29It is important to note (as reflected in Scheme 1)that the nature of the Li salts present greatly affects the electrode surface chemistry.When the pres-ence of the salt does not induce the formation of acidic species in solutions (e.g.,LiClO 4,LiN(SO 2CF 3)2),alkyl carbonates are reduced to ROCO 2Li and ROLi compounds,as presented in Fig. 2.In LiPF 6solutions acidic species are formed:LiPF 6decomposes thermally to LiF and PF 5.The latter moiety is a Lewis acid which further reacts with any protic contaminants (e.g.unavoidably present traces of water)to form HF.The presence of such acidic species in solution strongly affects the surface chemistry in two ways.One way is that PF 5interactswithFig.1The road map for R&D of new electrode materials,compared to today’s state-of-the-art.The y and x axes are voltage and specific capacity,respectively.Fig.2A schematic presentation of the CV behavior of inert (Pt)elec-trodes in various families of polar aprotic solvents with Li salts.26D o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 24 F e b r u a r y 2011P u b l i s h e d o n 23 F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0J M 04225Kthe carbonyl group and channels the reduction process of EC to form ethylene di-alkoxide species along with more complicated alkoxy compounds such as binary and tertiary ethers,rather than Li-ethylene dicarbonates (see schemes in Fig.2);the other way is that HF reacts with ROLi and ROCO 2Li to form ROH,ROCO 2H (which further decomposes to ROH and CO 2),and surface LiF.Other species formed from the reduction of EC are Li-oxalate and moieties with Li–C and C–F bonds (see Scheme 1).27–31Efforts have been made to enhance the formation of the passivation layer (on graphite electrodes in particular)in the presence of these solutions through the use of surface-active additives such as vinylene carbonate (VC)and lithium bi-oxalato borate (LiBOB).27At this point there are hundreds of publica-tions and patents on various passivating agents,particularly for graphite electrodes;their further discussion is beyond the scope of this paper.Readers may instead be referred to the excellent review by Xu 32on this subject.Ionic liquids (ILs)have excellent qualities that could render them very relevant for use in advanced Li-ion batteries,including high anodic stability,low volatility and low flammability.Their main drawbacks are their high viscosities,problems in wetting particle pores in composite structures,and low ionic conductivity at low temperatures.Recent years have seen increasing efforts to test ILs as solvents or additives in Li-ion battery systems.33Fig.3shows the cyclic voltammetric response (Pt working electrodes)of imidazolium-,piperidinium-,and pyrrolidinium-based ILs with N(SO 2CF 3)2Àanions containing LiN(SO 2CF 3)2salt.34This figure reflects the very wide electrochemical window and impressive anodic stability (>5V)of piperidium-and pyr-rolidium-based ILs.Imidazolium-based IL solutions have a much lower cathodic stability than the above cyclic quaternary ammonium cation-based IL solutions,as demonstrated in Fig.3.The cyclic voltammograms of several common electrode mate-rials measured in IL-based solutions are also included in the figure.It is clearly demonstrated that the Li,Li–Si,LiCoO 2,andLiMn 1.5Ni 0.5O 4electrodes behave reversibly in piperidium-and pyrrolidium-based ILs with N(SO 2CF 3)2Àand LiN(SO 2CF 3)2salts.This figure demonstrates the main advantage of the above IL systems:namely,the wide electrochemical window with exceptionally high anodic stability.It was demonstrated that aluminium electrodes are fully passivated in solutions based on derivatives of pyrrolidium with a N(SO 2CF 3)2Àanion and LiN(SO 2CF 3)2.35Hence,in contrast to alkyl carbonate-based solutions in which LiN(SO 2CF 3)2has limited usefulness as a salt due to the poor passivation of aluminium in its solutions in the above IL-based systems,the use of N(SO 2CF 3)2Àas the anion doesn’t limit their anodic stability at all.In fact it was possible to demonstrate prototype graphite/LiMn 1.5Ni 0.5O 4and Li/L-iMn 1.5Ni 0.5O 4cells operating even at 60 C insolutionsScheme 1A reaction scheme for all possible reduction paths of EC that form passivating surface species (detected by FTIR,XPS,Raman,and SSNMR 28–31,49).Fig.3Steady-state CV response of a Pt electrode in three IL solutions,as indicated.(See structure formulae presented therein.)The CV presentations include insets of steady-state CVs of four electrodes,as indicated:Li,Li–Si,LiCoO 2,and LiMn 1.5Ni 0.5O 4.34D o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 24 F e b r u a r y 2011P u b l i s h e d o n 23 F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0J M 04225Kcomprising alkyl piperidium-N(SO2CF3)2as the IL solvent and Li(SO2CF3)2as the electrolyte.34Challenges remain in as far as the use of these IL-based solutions with graphite electrodes.22Fig.4shows the typical steady state of the CV of graphite electrodes in the IL without Li salts.The response in this graph reflects the reversible behavior of these electrodes which involves the insertion of the IL cations into the graphite lattice and their subsequent reduction at very low potentials.However when the IL contains Li salt,the nature of the reduction processes drastically changes.It was recently found that in the presence of Li ions the N(SO2CF3)2Àanion is reduced to insoluble ionic compounds such as LiF,LiCF3, LiSO2CF3,Li2S2O4etc.,which passivate graphite electrodes to different extents,depending on their morphology(Fig.4).22 Fig.4b shows a typical SEM image of a natural graphite(NG) particle with a schematic view of its edge planes.Fig.4c shows thefirst CVs of composite electrodes comprising NG particles in the Li(SO2CF3)2/IL solution.These voltammograms reflect an irreversible cathodic wave at thefirst cycle that belongs to the reduction and passivation processes and their highly reversible repeated Li insertion into the electrodes comprising NG. Reversible capacities close to the theoretical ones have been measured.Fig.4d and e reflect the structure and behavior of synthetic graphiteflakes.The edge planes of these particles are assumed to be much rougher than those of the NG particles,and so their passivation in the same IL solutions is not reached easily. Their voltammetric response reflects the co-insertion of the IL cations(peaks at0.5V vs.Li)together with Li insertion at the lower potentials(<0.3V vs.Li).Passivation of this type of graphite is obtained gradually upon repeated cycling(Fig.4e), and the steady-state capacity that can be obtained is much lower than the theoretical one(372mA h gÀ1).Hence it seems that using graphite particles with suitable morphologies can enable their highly reversible and stable operation in cyclic ammonium-based ILs.This would make it possible to operate high voltage Li-ion batteries even at elevated temperatures(e.g. 4.7–4.8V graphite/LiMn1.5Ni0.5O4cells).34 The main challenge in thisfield is to demonstrate the reasonable performance of cells with IL-based electrolytes at high rates and low temperatures.To this end,the use of different blends of ILs may lead to future breakthroughs.Current collectorsThe current collectors used in Li-ion systems for the cathodes can also affect the anodic stability of the electrolyte solutions.Many common metals will dissolve in aprotic solutions in the potential ranges used with advanced cathode materials(up to5V vs.Li). Inert metals such as Pt and Au are also irrelevant due to cost considerations.Aluminium,however,is both abundantand Fig.4A collection of data related to the behavior of graphite electrodes in butyl,methyl piperidinium IL solutions.22(a)The behavior of natural graphite electrodes in pure IL without Li salt(steady-state CV is presented).(b)The schematic morphology and a SEM image of natural graphite(NG)flakes.(c)The CV response(3first consecutive cycles)of NG electrodes in IL/0.5lithium trifluoromethanesulfonimide(LiTFSI)solution.(d and e)Same as(b and c)but for synthetic graphiteflakes.DownloadedbyBeijingUniversityofChemicalTechnologyon24February211Publishedon23February211onhttp://pubs.rsc.org|doi:1.139/CJM4225Kcheap and functions very well as a current collector due to its excellent passivation properties which allow it a high anodic stability.The question remains as to what extent Al surfaces can maintain the stability required for advanced cathode materials (up to 5V vs.Li),especially at elevated temperatures.Fig.5presents the potentiodynamic response of Al electrodes in various EC–DMC solutions,considered the alkyl carbonate solvent mixture with the highest anodic stability,at 30and 60 C.37The inset to this picture shows several images in which it is demonstrated that Al surfaces are indeed active and develop unique morphologies in the various solutions due to their obvious anodic processes in solutions,some of which lead to their effective passivation.The electrolyte used has a critical impact on the anodic stability of the Al.In general,LiPF 6solutions demonstrate the highest stability even at elevated temperatures due to the formation of surface AlF 3and even Al(PF 6)3.Al CCs in EC–DMC/LiPF 6solutions provide the highest anodic stability possible for conventional electrode/solution systems.This was demonstrated for Li/LiMn 1.5Ni 0.5O 4spinel (4.8V)cells,even at 60 C.36This was also confirmed using bare Al electrodes polarized up to 5V at 60 C;the anodic currents were seen to decay to negligible values due to passivation,mostly by surface AlF 3.37Passivation can also be reached in Li(SO 2CF 3),LiClO 4and LiBOB solutions (Fig.5).Above 4V (vs.Li),the formation of a successful passivation layer on Al CCs is highly dependent on the electrolyte formula used.The anodic stability of EC–DMC/LiPF 6solutions and Al current collectors may be further enhanced by the use of additives,but a review of additives in itself deserves an article of its own and for this readers are again referred to the review by Xu.32When discussing the topic of current collectors for Li ion battery electrodes,it is important to note the highly innovative work on (particularly anodic)current collectors by Taberna et al.on nano-architectured Cu CCs 47and Hu et al.who assembled CCs based on carbon nano-tubes for flexible paper-like batteries,38both of whom demonstrated suberb rate capabilities.39AnodesThe anode section in Fig.1indicates four of the most promising groups of materials whose Li-ion chemistry is elaborated as follows:1.Carbonaceous materials/graphite:Li ++e À+C 6#LiC 62.Sn and Si-based alloys and composites:40,41Si(Sn)+x Li ++x e À#Li x Si(Sn),X max ¼4.4.3.Metal oxides (i.e.conversion reactions):nano-MO +2Li ++2e À#nano-MO +Li 2O(in a composite structure).424.Li x TiO y electrodes (most importantly,the Li 4Ti 5O 12spinel structure).43Li 4Ti 5O 12+x Li ++x e À#Li 4+x Ti 5O 12(where x is between 2and 3).Conversion reactions,while they demonstrate capacities much higher than that of graphite,are,practically speaking,not very well-suited for use as anodes in Li-ion batteries as they generally take place below the thermodynamic limit of most developed electrolyte solutions.42In addition,as the reactions require a nanostructuring of the materials,their stability at elevated temperatures will necessarily be an issue because of the higher reactivity (due to the 1000-fold increase in surface area).As per the published research on this topic,only a limited meta-stability has been demonstrated.Practically speaking,it does not seem likely that Li batteries comprising nano-MO anodes will ever reach the prolonged cycle life and stability required for EV applications.Tin and silicon behave similarly upon alloying with Li,with similar stoichiometries and >300%volume changes upon lith-iation,44but the latter remain more popular,as Si is much more abundant than Sn,and Li–Si electrodes indicate a 4-fold higher capacity.The main approaches for attaining a workable revers-ibility in the Si(Sn)–Li alloying reactions have been through the use of both nanoparticles (e.g.,a Si–C nanocomposites 45)and composite structures (Si/Sn–M1–M2inter-metalliccompounds 44),both of which can better accommodate these huge volume changes.The type of binder used in composite electrodes containing Si particles is very important.Extensive work has been conducted to determine suitable binders for these systems that can improve the stability and cycle life of composite silicon electrodes.46As the practical usage of these systems for EV applications is far from maturity,these electrodes are not dis-cussed in depth in this paper.However it is important to note that there have been several recent demonstrations of how silica wires and carpets of Si nano-rods can act as much improved anode materials for Li battery systems in that they can serveasFig.5The potentiodynamic behavior of Al electrodes (current density measured vs.E during linear potential scanning)in various solutions at 30and 60 C,as indicated.The inset shows SEM micrographs of passivated Al surfaces by the anodic polarization to 5V in the solutions indicated therein.37D o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 24 F e b r u a r y 2011P u b l i s h e d o n 23 F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0J M 04225K。

异常高温高盐油藏液流转向提高采收率技术朱秀雨，毛小倩，张 祎，扈福堂，党杨斌，李柳逸（中国石油 青海油田分公司，甘肃 敦煌 736202）［摘要］以丙烯酰胺、2-丙烯酰胺基-2-甲基丙磺酸等为单体，合成了耐温抗盐聚合物（KTPAM ），并将其与耐高温交联剂（RHTC ）、热稳定剂（TSA ）混合形成聚合物凝胶转向剂体系（ORHTHS ），同时自制了新型阴-非离子驱油表面活性剂。

利用FTIR ，SEM 等方法优化了ORHTHS 的配方，研究了ORHTHS 和表面活性剂的性能。

实验结果表明，优选的ORHTHS 配方为：0.5%～0.6%（w ）KTPAM+0.3%～0.5%（w ）RHTC+0.3%～0.4%（w ）TSA 。

ORHTHS 能满足高温高矿化度油藏深部封堵的要求。

将0.12 PV ORHTHS+0.3 PV 表面活性剂复合用于尕斯深层油藏，采收率可提高17百分点以上。

3口井的现场应用结果显示，井组有效率100%，累计阶段增油2 000 t ，降水增油效果显著。

［关键词］高温高盐；弹性模量；提高采收率；热稳定性；界面活性［文章编号］1000-8144（2020）12-1208-07 ［中图分类号］TE 355 ［文献标志码］AFluid flow diversion in abnormally high temperature and high salt reservoirs toenhance oil recovery technologyZhu Xiuyu ，Mao Xiaoqian ，Zhang Yi ，Hu Futang ，Dang Yangbin ，Li Liuyi（Qinghai Oilfield Company ，PetroChina ，Dunhuang Gansu 736202，China ）［Abstract ］With acrylamide and 2-acrylamido-2-methylpropanesulfonic acid as monomers ，a temperature-resistant salt-resistant polymer(KTPAM) was synthesized ，and it was combined with high-temperature crosslinking agent(RHTC) and heat stabilizer(TSA) to form an polymer gel steering agent system(ORHTHS). A new anion and non-ion flooding surfactant was prepared. The formulation of ORHTHS was optimized by FTIR ，SEM ，and the performance of ORHTHS and surfactants were studied. The results show that the optimum ORHTHS formula is ：0.5%-0.6%(w )KTPAM+0.3%-0.5%(w )RHTC+0.3%-0.4%(w )TSA. ORHTHS can meet the requirements of deep plugging in high temperature and high salinity reservoirs. The combination 0.12 PV ORHTHS+0.3 PV surfactants in Ga Si deep reservoirs improves the recovery efficiency by more than 17 percent point. The field application results of the three wells showed that the efficiency of the well group was 100%，the cumulative phase increase of oil was 2 000 t ，and the effect of precipitation and oil increase was significant.［Keywords ］high temperature and high salt ；elastic modulus ；enhanced oil recovery ；thermal stability ；interfacial activityDOI ：10.3969/j.issn.1000-8144.2020.12.009［收稿日期］2020-05-19；［修改稿日期］2020-09-18。

原子发射光谱法测定测定食品中铅的含量Determination of Pb in food by AES张廷红1周智勇2ZHANG Ting-hong 1ZHOU Zhi-yong 2（1.西南科技大学材料科学与工程学院化学系，四川绵阳621000；2.绵阳市自来水公司，四川绵阳621000）(1.College of Material Science and Engineering ，SouthwestUniversity of Science and Technology，Mianyang，Sichuan 621000,China；2.Mianyang Running Water Company,Mianyang，Sichuan 621000,China)摘要：电感耦合等离子体原子发射光谱法(ICP-AES)以其检出限低、精密度高、选择性好、基体效应小、线性范围宽和多元素同时测定等特点，在痕量元素分析领域得到了广泛应用。

采用湿法HNO 3-H 2O 2对试样进行消解，测定食品中铅的含量，其检出限为0.0102mg/L，元素回收率在88.9%～109%，RSD 在1.8%～2.5%。

所建立的用于测定食品中铅含量的分析方法其准确度和精密度都符合要求，应用本方法测定实际样品，结果令人满意。

关键词：电感耦合等离子体原子发射光谱法；铅；食品Abstract：The detect of Pb in food was studied by Inductively Coupled PlasmaAtomicEmissionSpectrometry(ICP-AES)afterHN03-H 2O 2digestion.The detection limit of Pb is 0.0102mg·L -1.The average recoveries of the method for Pb in food were found to be 88.9%～109.0%,while RSD(n =10)was found to be 1.8%～2.5%.The detection method was applied to the analysis of practical samples and the results obtained were satisfactory.Keywords:ICP-AES；Pb ；Food ——————————作者简介：张廷红（1969-），男，西南科技大学材料科学与工程学院化学系,讲师。

R454BIntroductionR454B is a next-generation refrigerant that is gaining popularity in the HVAC (Heating, Ventilation, and Air Conditioning) industry. It is an alternative to traditional refrigerants such as R410A and R134a, which are known to contribute to climate change. In this document, we will explore the properties and benefits of R454B as well as its impact on the environment.Properties of R454BR454B, also known as Opteon™ XL41, is a non-flammable and low-global warming potential (GWP) refrigerant. It is classified as an HFO (Hydrofluoroolefin) and is a blend of several other refrigerants. One of its key properties is its high energy efficiency, providing the same cooling capacity as other refrigerants but with a lower environmental impact.Environmental ImpactAs mentioned earlier, R454B has a low GWP compared to traditional refrigerants. GWP measures the greenhouse gas emissions over a specific time horizon, with carbon dioxide (CO2) as the base reference. R454B has a GWP of around 466, which is significantly lower than R410A’s GWP of 2088 andR134a’s GWP of 1430. By using R454B, HVAC systems can help reduce their carbon footprint and contribute to global efforts in combating climate change.Energy EfficiencyR454B is not only environmentally friendly but also highly energy-efficient. It has been proven to have similar or even higher energy efficiency compared to traditional refrigerants. This means that HVAC systems using R454B can achieve the same cooling capacity while consuming less energy, resulting in lower electricity bills and reduced overall energy consumption.Safety ConsiderationsR454B is classified as non-flammable, which means it does not pose a significant fire risk compared to some other refrigerants. However, it is always essential to handle any refrigerant with care and follow proper safety guidelines. HVAC professionals should ensure proper training and adhere to the necessary safety protocols when working with R454B.Regulatory ComplianceWith increasing global concerns about climate change, regulations regarding refrigerants’ environmental impacts have become more stringent. R454B complies with various international regulations, such as the European Union’s F-Gas Regulation and the Kigali Amendment to the Montreal Protocol. These regulations aim to phase out high-GWP refrigerants by implementing specific restrictions and encouraging the use of low-GWP alternatives like R454B.ApplicationsR454B can be used in a wide range of HVAC applications, including commercial and residential air conditioning systems, heat pumps, and refrigeration units. It is compatible with many existing HVAC equipment, making it a suitable replacement for older refrigerants without the need for significant system modifications.ConclusionR454B is a next-generation refrigerant that offers a range of benefits for the HVAC industry. With its low GWP, high energy efficiency, and compliance with environmental regulations, it is an excellent option for transitioning away from high-GWP refrigerants. HVAC professionals and system owners can contribute to sustainability efforts by adopting R454B in their cooling systems. The adoption of R454B can help reduce greenhouse gas emissions, lower energy consumption, and mitigate the impacts of climate change.。

jgs1太赫兹光谱-回复什么是太赫兹光谱？太赫兹光谱，即介于红外光和微波之间的电磁辐射波段，频率范围为300 GHz到30 THz。

太赫兹光谱技术是研究和应用这一波段的光谱学和光学方法。

太赫兹光谱在化学、物理、生物、医学、安全检测、材料科学等领域具有广泛的研究和应用价值。

1. 太赫兹光谱的起源和发展太赫兹光谱的研究起源于二十世纪六七十年代初，当时科学家们开始意识到红外光和微波之间存在一个未被充分研究的光谱区域。

随着技术的进步，太赫兹光谱逐渐成为一个新兴的研究领域，并在二十一世纪蓬勃发展。

2. 太赫兹光谱的特点太赫兹光谱有一些独特的特点，使其在许多研究领域中备受关注。

首先，太赫兹光谱具有较强的穿透能力，能够通过大多数非金属材料，包括纸张、布料、塑料等。

其次，太赫兹光谱对许多物质具有较高的选择性，能够通过分子的振动和转动状态来检测物质的结构和成分。

此外，太赫兹光谱还具有非侵入性和非破坏性的特点，能够在不破坏样品的情况下进行分析。

3. 太赫兹光谱的应用领域太赫兹光谱在许多领域中具有广泛的应用价值。

在化学领域，太赫兹光谱可以用于物质的结构表征和分析，例如研究分子间的相互作用、分析化学反应等。

在物理领域，太赫兹光谱可用于研究凝聚态物理、超导、半导体器件等。

在生物和医学领域，太赫兹光谱可以用于生物分子的结构和动力学研究，以及肿瘤检测、药物分析等。

在安全检测领域，太赫兹光谱可以用于检测爆炸物、毒品、化学品等危险物质。

在材料科学领域，太赫兹光谱可用于材料表征、缺陷分析、非破坏检测等。

4. 太赫兹光谱的技术和仪器实现太赫兹光谱的研究和应用需借助于一系列技术和仪器。

目前常用的太赫兹光谱技术主要包括时域光谱和频域光谱。

时域光谱技术基于飞秒激光脉冲的相干检测，能够提供高时间和频率分辨率的信息。

频域光谱技术则基于快速扫描的光谱仪，能够提供更高的信噪比和光谱分辨率。

此外，太赫兹成像技术、太赫兹光纤技术等也是太赫兹光谱研究中重要的技术手段。

成都理工大学学生毕业设计（论文）外文译文极，（b）光电子是后来ηNph，（c）这些∝ηNph电子在第一倍增极和到达（d）倍增极的k（k = 1，2…）放大后为δk 并且我们假设δ1=δ2=δ3=δk=δ的，并且δ/δ1≈1的。

我们可以得出：R2=Rlid2=5.56δ/[∝ηNph（δ-1）] ≈5.56/Nel （3）Nel表示第一次到达光电倍增管的数目。

在试验中，δ1≈10＞δ2=δ3=δk，因此，在实际情况下，我们可以通过（3）看出R2的值比实际测得大。

请注意，对于一个半导体二极管（不倍增极结构）（3）也适用。

那么Nel就是是在二极管产生电子空穴对的数目。

在物质不均匀，光收集不完整，不相称和偏差的影响从光电子生产过程中的二项式分布及电子收集在第一倍增极不理想的情况下，例如由于阴极不均匀性和不完善的重点，我们有：R2=Rsci2+Rlid2≈5.56[(νN-1/Nel)+1/Nel] (4)νN光子的产生包括所有非理想情况下的收集和1/Nel的理想情况。

为了说明，我们在图上显示，如图1所示。

ΔE/E的作为伽玛射线能量E的函数，为碘化钠：铊闪烁耦合到光电倍增管图。

1。

对ΔE/E的示意图（全曲线）作为伽玛射线能量E功能的碘化钠：铊晶体耦合到光电倍增管。

虚线/虚线代表了主要贡献。

例如见[9,10]。

对于Rsci除了1/（Nel）1/2的组成部分，我们看到有两个组成部分，代表在0-4％的不均匀性，不完整的光收集水平线，等等，并与在0-400代表非相称keV的最大曲线。

表1给出了E=662Kev时的数值（137Cs）在传统的闪烁体资料可见。

从图一我们可以清楚的看到在低能量E＜100Kev，如果Nel，也就是Nph增大的话，是可以提高能量分辨率的。

这是很难达到的，因为光额产量已经很高了（见表1）在能量E＞300Kev时，Rsci主要由能量支配其能量分辨率，这是没办法减小Rsci 的。

然而，在下一节我们将会讲到，可以用闪烁体在高能量一样有高的分辨率。

文章编号:025827025(2005)0921217204可调谐二极管激光吸收光谱法监测环境空气中甲烷的浓度变化阚瑞峰,刘文清,张玉钧,刘建国,董凤忠,王　敏,高山虎,陈　军,王晓梅(中国科学院环境光学与技术重点实验室,中国科学院安徽光学精密机械研究所,安徽合肥230031)摘要　可调谐二极管激光吸收光谱(TDL AS )技术是利用二极管激光器波长调谐特性,获得被测气体在特征吸收光谱范围内的吸收光谱,从而对污染气体进行定性或定量分析。

通过该方法对环境空气中甲烷(CH 4)的含量进行了长时间的监测。

以室温下工作的近红外可调谐半导体激光器作为光源;使用多次反射池增加吸收光程来提高检测灵敏度;并且使用了二次谐波检测技术进一步降低了检测限,使检测限低于01087mg/m 3,满足了对环境空气中甲烷进行监测的需要。

关键词　光谱学;痕量气体监测仪;可调谐二极管激光吸收光谱;谐波探测中图分类号　O 433.5+1 文献标识码　ATunable Diode Laser Absorption Spectrometer Monitors the AmbientMethane with High SensitivityKAN Rui 2feng ,L IU Wen 2qing ,ZHAN G Yu 2jun ,L IU Jian 2guoDON G Feng 2zhong ,WAN G Min ,GAO Shan 2hu ,C H EN J un ,WAN G Xiao 2mei(Key L aboratory of Envi ronmental O ptics &Technology ,A nhui I nstitute ofO ptics and Fine Mechanics ,T he Chinese A cadem y of Sciences ,Hef ei ,A nhui 230031,China )Abstract Tunable diode laser absorption spectroscopy (TDL AS )technique is a new method to detect trace 2gas qualitatively or quantificationally based on the scan characteristic of the diode laser to obtain the absorption spectra in the characteristic absorption region.It needs to combine with a long absorption path in the ambient trace 2gas measurements.It has a significant advantage not only in sensitivity but also in rapidity of response.The experimental results of monitoring of methane of the ambient air in a long time with a ground 2based portable TDL AS system are described ;it works with a room 2temperature near infrared tunable diode laser to measure methane in the ambient air ,the path length is lengthened by the multiple 2reflection cell to lower the detection limit ;and the second harmonic detection is used to lower the detection limit farther ;the detection limit is below 01087mg/m 3,that is enough to the monitoring of ambient methane.K ey w ords spectroscopy ;trace 2gas monitor ;tunable diode laser absorption spectroscopy ;harmonic detection 收稿日期:2004211217;收到修改稿日期:2005204229 基金项目:国家自然科学基金(10274080)和国家863计划(2003AA641010)资助项目。

1 外文资料翻译译文具有高灵敏度的甲醛气体传感器的制备及其气敏特性相对甲醛混有氧化铬的氧化铟气体传感器特性已经研究过了。

间接加热式气体传感器是用敏感材料进行制备的。

最终的材料的状态和传感层的形态通过x射线衍射和扫描电子显微镜分别在焙烧前后观察到其特点。

操作温度对传感器响应的影响氧化铬和氧化铟传感器的气体浓度特性的对比已经研究过了。

结果表明，在低操作温度该传感器对于甲醛具有良好的反应性能，使他们成为甲醛气体检测最有希望的候选材料。

1介绍作为一个重要的工业化学品，甲醛被应用于制造业，建筑板，胶合板和漆这样的材料。

此外，它还是消费产品中一个中间添加物，如洗涤剂和肥皂。

由于其杀菌性能也可用于药理学和药物中。

然而，调查结果表明，因为它是挥发性有害化合物，所以甲醛会对人体造成许多损害。

因此，需要一种有效的方法来监测甲醛进而进行气体环境测量与控制。

制造气体传感器被认为是一个理想的监测气体的手段。

我们目前的调查主要涉及与甲醛的检测。

虽然半导体金属氧化物气体传感器提供了对有毒气体或可燃性气体的安全检测，但是他们仍然有一定的局限性，如灵敏度，选择性，长期稳定性等等。

为了克服半导体金属氧化物气体传感器的缺点，半导体金属氧化物的制备与掺杂的研究已经做过了。

氧化铟是一个有希望的具有宽禁带的半导体材料（3.70电子伏特），其电子浓度主要取决于计量缺陷的浓度（如氧空位）就像其他金属氧化物半导体。

就传感机制来说，颗粒的大小，缺陷，表面与界面的性能和化学计量学直接影响了传感器表面的氧化物种类的状态和数量，最后影响了金属氧化物传感器的性能。

因此，为了提高并改善气体传感性能（敏感性，选择性，较好的热稳定性和较低的操作温度），氧化铟通常用于纳米结构形式或掺杂合适的贵金属和金属氧化物。

作为一个单组分氧化物，由于其良好的灵敏度，氧化铟是一种很有前途的氧化性气体检测的候选者。

因此，当其他金属氧化物掺杂氧化铟，对于不同的气体可调谐的气体灵敏度也不同。