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Available online at Journal of Power Sources180(2008)553–560Synthesis and characterization of Carbon Nano Fiber/LiFePO4composites for Li-ion batteriesM.S.Bhuvaneswari a,∗,N.N.Bramnik a,D.Ensling a,H.Ehrenberg a,b,W.Jaegermann aa Darmstadt University of Technology,Institute of Materials Science,Petersenstrasse23,64287Darmstadt,Germanyb IFW Dresden,Institute for Complex Materials,Helmholtzstr,20,01069Dresden,GermanyReceived22September2007;received in revised form17January2008;accepted26January2008Available online16February2008AbstractCarbon Nano Fibers(CNFs)coated with LiFePO4particles have been prepared by a non-aqueous sol–gel technique.The functionalization of the CNFs by HNO3acid treatment has been confirmed by Raman and XPS analyses.The samples pure LiFePO4and LiFePO4–CNF have been characterized by XRD,SEM,RAMAN,XPS and electrochemical analysis.The LiFePO4–CNF sample shows better electrochemical performance compared to as-prepared LiFePO4.LiFePO4–CNF(10wt.%)delivers a higher specific capacity(∼140mAh g−1)than LiFePO4with carbon black (25wt.%)added after synthesis(∼120mAh g−1)at0.1C.©2008Elsevier B.V.All rights reserved.Keywords:Carbon Nano Fiber;LiFePO4;Raman analysis;X-ray photo electron spectroscopy;Electrochemical analysis1.IntroductionThe commercially used cathode material LiCoO2in lithium-ion batteries is associated with problems such as high cost, toxicity,and safety risks in large scale applications which cre-ated a paramount need for an alternative cathode candidate[1]. Recently lithium3d-metal orthophosphates have gained a sub-stantial interest as positive cathode materials[2–5].Among the orthophosphates LiFePO4exhibits several properties such as environmental friendliness,low price,non-toxicity,and excep-tional stability,which perfectly matches with the needs to replace LiCoO2[6,7].However,a major limitation of this material is its poor rate performance,because of its low electronic con-ductivity[8–11].Current research on LiFePO4-based materials aims towards improving the rate performance by reducing its particle size and by effective carbon coating[8–11].Various synthesis methods such as sol–gel,co-precipitation,carbother-mal reduction,etc.have been utilized to optimize the particle size of LiFePO4,and positive results have been reported[8–13].∗Corresponding author.Tel.:+496151166353;fax:+496151166308.E-mail address:bhuvana.siva@(M.S.Bhuvaneswari).Different organic additives for carbon coating around LiFePO4 particles and cation doping into the olivine structure have also been tried to enhance the intrinsic electronic conductiv-ity of LiFePO4[14,15].Hu et al.reported that the structure of the residual carbon on the LiFePO4particles is important for the electrochemical performance[14].Zaghib et al.reported that a critical factor towards improving the performance is the carbon content in the electrode,which is related to elec-trical conductivity and networking between particles[16].A new approach to enhance the effects of carbon content and coating of LiFePO4particles is reported here,based on the addi-tion of functionalized Carbon Nano Fibers(CNFs)during the sol–gel synthesis of LiFePO4.It has been reported in litera-ture[17]that carbon is found efficient to reduce the resistivity of LiFePO4if sp3bonding in carbon is very small hence in the present study Carbon Nano Fiber has been used instead of amorphous carbon.It has been found that the functional-ized CNFs can be coated with LiFePO4.For comparison,pure LiFePO4has also been prepared by a non-aqueous sol–gel method.LiFePO4-coated CNF electrodes without additional carbon black show excellent electrochemical performance and are compared to electrodes,prepared from pure LiFePO4with additional carbon black.The samples have been characterized0378-7753/$–see front matter©2008Elsevier B.V.All rights reserved. doi:10.1016/j.jpowsour.2008.01.090554M.S.Bhuvaneswari et al./Journal of Power Sources180(2008)553–560by thermogravimetric–differential thermal analysis(TG–DTA), XRD,SEM,Raman spectroscopy,XPS and electrochemical analyses.2.ExperimentalLiFePO4has been prepared from a mixture of Li(CH3 COO)·2H2O(lithium acetate),Fe(CH3COO)2(iron acetate), H3PO4(phosphoric acid)and ethylene glycol.The synthesis conditions reported by Yang et al.with slight modifications have been adopted[13].The precursors were dissolved in ethy-lene glycol at a molar ratio of1:1:1.After rigorous stirring the resulting gel has been heat treated at700◦C with a heating rate of10◦C min−1in argon atmosphere for12h(here after to be named as pure LiFePO4).The functionalization of pyrolytically stripped Carbon Nano Fibers(commercial grade from Electrovac AG,Austria,with a diameter and length of100–200nm and>20␮m,respec-tively)was achieved by treating the Carbon Nano Fiber with conc.HNO3at70◦C for24h.After treatment the suspension of C-Fibers in HNO3was diluted with deionized water,filtered, washed with water and dried at110◦C in open air atmosphere (here after the acid treated Carbon Nano Fiber to be named simply as CNF).10wt.%of CNF has been added with the same precursors used for preparing pure LiFePO4during sol–gel preparation, and the sol–gel has been stirred for one week in order to get better contact of LiFePO4particles with CNF.The gel has been heat treated at600◦C with a heating rate of10◦C min−1 in argon atmosphere for12h(here after will be named as LiFePO4–CNF).TG–DTA measurements have been performed(TGA92-Setaram)from0to1000◦C at a heating rate of10◦C min−1 under argon atmosphere.The samples were tested by X-ray powder diffraction using a STOE STADI/P powder diffrac-tometer(Mo K␣1radiation).A scanning electron microscope Philips XL30FEG has been used to observe the parti-cles morphology.To determine the carbon content elemental analysis has been performed using VarioEL III CHN elemen-tal analyzer.Raman measurements have been carried out by Labram800HR open microscope from Horiba Jobin Yvon with a laser wavelength of488nm.The XPS studies have been performed using an Escalab250Spectrometer with a monochro-matized Al anode.Electrochemical studies were carried out with a multichannel potentiostatic–galvanostatic system VMP (PerkinElmer Instruments,USA).Swagelok-type cells were assembled in an argon-filled dry box with water and oxygen contents less than1ppm.A pure LiFePO4cathode compos-ite has been fabricated as follows:60%active material,25% acetylene carbon black and15%PTFE as binder were inti-mately mixed,ground in an agate mortar and pressed onto an Al-mesh(resulting electrodes contain about3mg of active com-pound).The LiFePO4–CNF cathode consists of90%LiFePO4 (10wt.%CNF)and10%PTFE.2.31wt.%and12.29wt.%car-bon(calculated from elemental analysis)contents for the pure LiFePO4and the LiFePO4–CNF samples,respectively,have been included for the cathode active mass calculation,lithium metal was used as anode and the electrolyte was1M LiPF6in2:1EC/DMC.3.Results and discussion3.1.Functionalization of CNFsCarbon Nano Fibers have been functionalized by concen-trated HNO3before they were added to the gel,to get betteradhesion to the LiFePO4particles by introducing compatiblefunctional groups on the Carbon Nano Fiber surface[18].Thistreatment with acid leads to a partial oxidation of the surfaceand the formation of oxidized groups like C OH–or C O.The functionalization has been confirmed by Raman and XPSanalyses.3.1.1.Raman analysisThe Raman spectra of pristine CNF and HNO3treated CNFare shown in Fig.1.The band in the region of2500–2900cm−1is the second order D-band(D*-band),which depends on the3-dimensional packing scheme.The group of peaks observed in therange of1550–1660cm−1is called the graphite band(G-band),which is most pronounced for a high degree of symmetry andordered structure in a carbon material.The bands observed from1250to1450cm−1corresponds to a disorder-induced phononmode(D-band)with a high intensity for disordered carbon mate-rials.The relative intensities I D/I G and I D∗/I G can be used qualitatively to characterize the order of carbon materials and arealso a measure for the amount of carbon defects in the nanofibersdue to the presence of functional groups[19,20].Higher ratiosof I D/I G or I D∗/I G correspond to a lower degree of order in the CNFs[19].The characteristic Raman bands observed for pris-tine and HNO3treated CNF are tabulated in Table1.The I D/I G ratio for HNO3treated CNFs is high compared to the pristine CNFs which confirms the functionalization of the Carbon Nano Fibers,an important factor for networking LiFePO4particles with the surface of Carbon NanoFibers.Fig.1.Raman spectra for pristine and functionalized CNFs.M.S.Bhuvaneswari et al./Journal of Power Sources180(2008)553–560555 Table1Raman wave numbers and corresponding band assignments for pristine and functionalized CNFsSample D line(cm−1)G peak(cm−1)D*peak(cm−1)D/G value(cm−1)D*/G value(cm−1) Pristine CNF1349.21570.32698.90.3940.116 Functionalized CNF1358.11575.02703.90.4900.179LiFePO4–CNF1336.41578.82651.90.4000.1463.1.2.XPS analysisThe XPS survey spectra of pristine CNF and functional-ized CNF(not shown)indicates that carbon and oxygen are the dominant species comprising the carbonfiber surfaces. The corresponding high resolution carbon C1s and oxygen O1s XPS spectra are shown in Fig.2a and b,respectively. The C1s spectrum of pristine CNFs shows the graphitic car-bon peak at284.6eV.The C1s spectrum of pristine CNF is asymmetric in nature and the O1s peak has been decon-voluted into two main peaks,corresponding to C O groups (∼531.1eV)and C OH groups(∼532.7eV)[21].This indi-cates that the pristine CNFs have already been oxidized to an appreciable extent,a normal behavior of Carbon Nano Fibers[21].The HNO3treated CNFs indicate a significant change in the XPS spectra of carbon C1s and oxygen O1s compared to pristine CNFs.Considering the C1s profile,the main emission(284.6eV)broadens towards higher binding energy(B.E.)and there is clearly enhanced emission of a fea-ture near288eV.The former observation is consistent with an increased presence of hydroxyl groups,whereas the latter trend is consistent with an increase in the relative amount of car-boxyl functional groups[21].The O1s spectra become more asymmetric and broader towards lower binding energy,consis-tent with an increase in the relative proportion of C O and C OH groups[21].The O/C atomic ratio of pristine CNFs and HNO3treated CNFs are∼0.02and∼0.234,respectively. The increase in the O/C atomic ratio confirms the function-alization of Carbon Nano Fibers by HNO3acid treatment [22].3.2.Synthesis and characterization of pure LiFePO4and LiFePO4–CNF3.2.1.TG–DTA analysisFig.3shows the thermogravimetric–differential thermal analysis curves for the sol–gel precursors of pure LiFePO4. The TG curves indicate one sharp mass-loss peak between 129and245◦C( m/m=83.18wt.%).This mass-loss process is related to exothermic and endothermic peaks in the DTA curve.The exothermic peaks at96.6,218.6,330.4and422.3◦C are due to the thermal decomposition of ethylene glycol and acetate precursors.The endothermic peaks observed at325.9and 368.5◦C correspond to the elemental carbon formation[23–25]. An endothermic peak has been observed at422.3◦C for pure LiFePO4,but no appreciable weight loss is observed in the TG curve above245◦C,suggesting that the crystallization of LiFePO4takes place at this temperature.A single phase with an ordered olivine structure will be realized even at550◦C,but the effective amorphous carbon coating from the precursors(with-out the addition of CNF)will be obtained when the samples were heat treated at700◦C,hence the synthesis temperature for pure LiFePO4has been chosen as700◦C[4,13].The synthesistem-Fig.2.XPS spectra(a)in the region of C1s for pristine and HNO3treated CNF;(b)in the region of O1s for pristine and HNO3treated CNF.556M.S.Bhuvaneswari et al./Journal of Power Sources180(2008)553–560Fig.3.TG/DTA curves of LiFePO4obtained under argon atmosphere at a heating rate of10◦C min−1.perature for LiFePO4–CNF has been chosen as600◦C as we are not interested in amorphous carbon coating for LiFePO4–CNF samples.3.2.2.XRD analysisThe XRD patterns for pure LiFePO4(Fig.4a)and LiFePO4–CNF(Fig.4b)indicate the good crystalinity of samples.All reflections can be indexed based on the orthorhom-bic LiFePO4crystallizing in the space group Pnma.A slight contribution from the amorphous part can be identi-fied in the diffraction pattern of LiFePO4–CNF composite, which can be attributed to the presence of amorphous C-Fibers in the sample.The olivine-like structure was confirmed by Rietveld analysis performed with the structural model taken from Ref.[26].The unit cell parameters obtained for LiFePO4(a=10.3281(3)˚A,b=6.0080(2)˚A,c=4.6947(1)˚A) and for LiFePO4–CNF(a=10.3314(7)˚A,b=6.0064(4)˚A, c=4.6996(4)˚A)are in a good agreement with the ones reported in literature[26].3.2.3.SEMThe scanning electron micrographs of pure LiFePO4are shown in Fig.5a and b.The SEM pictures indicate the agglom-eration of particles and grain dimensions of about500nm Fig.4.Rietveld refinement of(a)LiFePO4and(b)LiFePO4–CNF samples prepared by a non-aqueous sol–gel method.to1␮m.The SEM pictures of LiFePO4–CNF are shown in Fig.6a and b,which indicate a non-homogeneous coating of LiFePO4particles smaller than200nm over Carbon Nano Fibers.The reduction in particle size in comparison withpure Fig.5.(a and b)SEM images of CNF free LiFePO4.M.S.Bhuvaneswari et al./Journal of Power Sources 180(2008)553–560557Fig.6.(a and b)SEM images of CNF added LiFePO 4.LiFePO 4is mainly due to the lower synthesis temperature for LiFePO 4–CNF.3.2.4.Raman analysisThe Raman spectra of LiFePO 4and LiFePO 4–CNF are shown in Fig.7.The carbon lines at 1339.3and at 1579.7cm −1are significantly screened by the characteristic Raman lines for both the pure LiFePO 4and the LiFePO 4–CNF samples.The weak carbon lines,which appear for “pure”LiFePO 4are due to the presence of residual carbon from the organic precursors.The intramolecular stretching modes of PO 43−are recorded at 581,987.5and 1051cm −1.Only a slight difference in the characteris-tic Raman wave numbers (shifted by 4–6cm −1)of LiFePO 4has been observed between pure LiFePO 4and LiFePO 4–CNF sam-ples due to interactions with the CNFs.LiFePO 4–CNF shows a second order D-band (D *).The intensity ratios D/G and D */G have been calculated and are also tabulated in Table 1.The D/G and D */G values of LiFePO 4with 10wt.%CNF are higher when compared to pristine CNFs but lower than for the HNO 3treated CNFs.An intermediate value for LiFePO 4–CNF is expected,because in addition to the 10wt.%CNFs amorphous carbon is also present from the organic precursors.These intensity ratios are not reliable to evaluate the sp 3and sp 2content in samples with amorphous carbon in it [17].Fig.7.Raman spectra of pure LiFePO 4and LiFePO 4–CNF samples. 3.2.5.XPS analysisThe XPS spectra of pure LiFePO 4and LiFePO 4–CNF sam-ples in the binding energy range of O1s,C1s and P2p are shown in Figs.8and 9respectively.Their corresponding binding ener-gies are tabulated in Table 2.The LiFePO 4–CNF sample shows the appearance of a shoulder at higher binding energies of O1s spectra which is absent for the pure sample.We therefore assign this emission to the oxidation modified CNT containing C O and C OH surface moieties [22].The main emission represents the LiFePO 4oxide ions in LiFePO 4.The carbon C1s line is deconvoluted into three contributions for both the CNFfreeFig.8.XPS spectrum in the region of P2p,C1s,O1s for pure LiFePO 4.558M.S.Bhuvaneswari et al./Journal of Power Sources180(2008)553–560Fig.9.XPS spectrum in the region of P2p,C1s,O1s for LiFePO4–CNF. and CNF added samples.The graphitic carbon emission for LiFePO4–CNF sample is observed at284.7eV.The asymmetric behavior of the C1s line for pure LiFePO4is due to the pres-ence of amorphous carbon,as observed in Raman analysis.The P2p emission corresponds to the PO43−group and the Fe/P ratio (1.06)is consistent with the compound stoichiometry for both pure LiFePO4and LiFePO4–CNF samples[27].The XPS spectra in the region of Fe2p for pure LiFePO4 and LiFePO4–CNF samples are shown in Fig.10.Thebinding Fig.10.XPS spectrum in the region of Fe2p for pure LiFePO4and LiFePO4–CNF.energy scale is presented as measured.A single low intensity peak on the low binding energy side of the envelope is due to the formation of Fe ions with a lower than normal oxidation state by the production of defects in neighboring sites[28].For transition metal ions with partiallyfilled d-states the appearance of satellite peaks(mentioned as shoulder peaks in literature)is a character-istic feature,and for our samples we observe this satellite peaks along with the main Fe2p peaks at higher binding energies of Fe2p(Table2).The Fe2p emission is consistent to previously published spectra of LiFePO4.The main and the satellite binding energy positions of the Fe2p peaks perfectly match with the B.E. positions reported in literature and are characteristic for Fe2+ cations.Normally the B.E.separation between the Fe2p main peak and satellite peak indicates the Fe2+and Fe3+contribution in the sample.In comparison to spectra obtained for oxides the feature of the2p3/2emission can be assigned to a dominant con-tribution of Fe in its normal2+oxidation state[29–31].For our samples the B.E.separation between the Fe2p main peak and the satellite peak for pure LiFePO4and LiFePO4–CNF samples is nearly6eV,which confirms that only Fe2+contributions are present in the sample.For Fe3+contributions the energy sep-aration between main and satellite peaks would be8eV[31]. We were not able to deconvolute the main emission line as reported in[30]further due to limited resolution of the spec-Table2XPS binding energies of various atoms for pure LiFePO4and LiFePO4–CNFElements Pure LiFePO4(eV)LiFePO4–CNF(eV)AssignmentsOxygen (O1s)531.3531.5LiFePO4533.0CNT(C OH,C O)Carbon (C1s)284.2284.2CNT 286.1285.6CNT–OH 288.2289.3CNT–COPhosphorus(P2p)133.4133.5PO4 Iron(Fe2p)709.6707.6Defects Fe2p3/2712.6710.5Fe2+718.3716.7Satellite Fe2p1/2726.0724.1Fe2+732.7730.2SatelliteM.S.Bhuvaneswari et al./Journal of Power Sources 180(2008)553–560559tra;despite the principle resolution power of our setup is below 0.4eV .This is probably due to some inhomogeneity effects in slight charging and/or crystalline quality of our samples.A more detailed analysis of the photoemission feature will be performed in future experiments also considering the charges in oxidation states during charging (Li deintercalation).3.2.6.Electrochemical measurementsElectrochemical measurements have been performed for pure LiFePO 4and LiFePO 4–CNF samples.The elemental anal-ysis for pure LiFePO 4indicates the presence of 2.3wt.%of carbon content in the sample and has been included in the calculation of the active mass.12.3wt.%of carbon con-tent for the LiFePO 4–CNF sample has two origins,10wt.%from the functionalized CNFs (known amount)and around 2.3wt.%from amorphous carbon,as calculated from elemen-tal analysis.Hence 12.3wt.%carbon has been included for active mass calculation for the LiFePO 4–CNF cathode sample.Fig.11a and b shows the potential versus composition curves of LiFePO 4and LiFePO 4–CNF electrode at 0.5C rate respectively.Fig.12represents the cycling performance of pure LiFePO 4and LiFePO 4–CNF samples.The results indicate that thehighlyFig.11.Potential–composition curves of (a)LiFePO 4at 0.5C and (b)LiFePO 4–CNF at0.5C.Fig.12.Cycling performance of pure LiFePO 4and LiFePO 4–CNF.ordered pyrolytically stripped Carbon Nano Fibers improve the electrochemical performance of LiFePO 4–CNF cathodes with low carbon content (∼10wt.%)in comparison with amorphous carbon black (∼25wt.%)added to pure LiFePO 4.The specific structure of the carbon additives plays a dominant role for the resulting electrochemical performance [14].Currently interface studies on the electrochemical behavior of LiFePO 4–CNF by in situ XPS and investigations of the rate capability are in progress.4.ConclusionLiFePO 4particles coated over CNF fibers have been synthe-sized by a sol–gel method.An oxidative wet functionalization of Carbon Nano Fibers by concentrated HNO 3gives bet-ter adhesion of LiFePO 4particles on the CNF surfaces.The functionalized Carbon Nano Fiber added LiFePO 4shows bet-ter electrochemical performance compared to acetylene black added LiFePO 4even though the coating is not homogeneous.The results indicate that the specific structure of the compos-ite electrode induced by the CNT plays a significant role in enhancing the electrochemical performance of LiFePO 4–CNF with simultaneously reduced carbon content,which is important for their practical use.The improved performance is probably due to the high electronic conductivity of the cathode material due to the CNF addition and the efficient contact between elec-trochemical active particles and the electronic conducting CNFs.The nanosized composite shortens the diffusion paths for lithium ions,increases the diffusion rate and results in better kinetic conditions in the electrode material.A more uniform coating of LiFePO 4over the CNF layers is the next step to approach the theoretical capacity over large cycle numbers at high charging rates and with low carbon content.AcknowledgementFinancial support from the Deutsche Forschungsgemein-schaft under grant nos.DFG JA859/14and EH183/3within the Priority Programme SPP 1181“Nanoscaled Inorganic Materials by Molecular Design:New Materials for Advanced Technolo-gies”is gratefully acknowledged.560M.S.Bhuvaneswari et al./Journal of Power 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Preparation and characterization of carbon-coated LiFePO 4cathode materials for lithium-ion batteries with resorcinol –formaldehyde polymer as carbon precursorYachao Lan,Xiaodong Wang ⁎,Jingwei Zhang,Jiwei Zhang,Zhishen Wu,Zhijun Zhang ⁎Key Laboratory for Special Functional Materials,Henan University,Kaifeng 475004,Chinaa b s t r a c ta r t i c l e i n f o Article history:Received 8February 2011Received in revised form 26May 2011Accepted 3June 2011Available online 12June 2011Keywords:Lithium iron phosphateResorcinol –formaldehyde polymer Lithium-ion batteryLiFePO 4/C composites were synthesized by two methods using home-made amorphous nano-FePO 4as the iron precursor and soluble starch,sucrose,citric acid,and resorcinol –formaldehyde (RF)polymer as four carbon precursors,respectively.The crystalline structures,morphologies,compositions,electrochemical performances of the prepared powders were investigated with XRD,TEM,Raman,and cyclic voltammogram method.The results showed that employing soluble starch and sucrose as the carbon precursors resulted in a de ficient carbon coating on the surface of LiFePO 4particle,but employing citric acid and RF polymer as the carbon precursors realized a uniform carbon coating on the surface of LiFePO 4particle,and the corresponding thicknesses of the uniform carbon films are 2.5nm and 4.5nm,respectively.When RF polymer was used as the carbon precursor,the material showed the highest initial discharge capacity (138.4mAh g −1at 0.2C at room temperature)and the best rate performance among the four materials.©2011Elsevier B.V.All rights reserved.1.IntroductionLiFePO 4is an attractive cathode material for lithium-ion batteries because of its high theoretical capacity of 170mAh g −1,environ-mental benign,and high thermal stability.However,its poor electric conductivity of less than 10−13S cm −1limits its battery performance [1],such as the dramatic decrease in power at a high current density,which is the main drawback to commercial use.To overcome the low electric conductivity of LiFePO 4,many effective approaches have been introduced,including metal substitution [2–5],metal powder com-pounding [6],and conductive carbon coating [7–15].Among them,the preparation of LiFePO 4/carbon composite (LiFePO 4/C)is one of the attractive ways to improve the electric conductivity of the final product by forming a good conduction path.Furthermore,carbon can be also used as a reductant,which can reduce Fe 3+ions to Fe 2+ions.It should be noted that many studies involving the synthesis of nano-sized LiFePO 4employ Fe 2+salts as precursors [3,16–20],such as FeC 2O 4·2H 2O and (CH 3COO)2Fe,which are expensive.Therefore,it is necessary to use cheap materials and a convenient method.Here,we report the synthesis,characterization and electrochemical test of LiFePO 4/C composites prepared by two methods using home-made amorphous nano-FePO 4as the iron precursor and various organics as carbon precursors.The two methods using FePO 4as starting material are cheap and environmentally benign for the production of LiFePO 4material.Particularly,we present a novel method to synthesize a uniformcarbon film coated LiFePO 4cathode materials.This method involved an in situ reaction of resorcinol and formaldehyde on the surface of amorphous FePO 4.At room temperature,electrochemical tests showed that this material exhibited an initial discharge capacity of 138.4mAh g −1at 0.2C and a good cycling property at 0.5and 1.0C rate,respectively.2.Experimental2.1.Preparation of amorphous nano-FePO 4Amorphous nano-FePO 4was prepared by spontaneous precipita-tion from aqueous solutions.An equimolar solution of H 3PO 4was added to a solution of Fe(NO 3)3·9H 2O at 60°C under stirring and given amounts of PEG-400as surfactant.Then ammonia water (NH 3·H 2O)was slowly added to the mixed solution under vigorous stirring and a milk-white precipitate formed immediately.The pH of the solution was kept at 2.0.The precipitate was filtered and washed several times with distilled water.After drying in vacuum oven at 120°C for 12h,yellowish-white amorphous FePO 4was obtained.2.2.Preparation of LiFePO 4/CTwo methods were used to prepare the LiFePO 4/C composites in this study.2.2.1.Method oneA rheological phase method [21]was employed to synthesize LiFePO 4/C composite.Stoichiometric amount of amorphous FePO 4,LiOH·H 2O were used as the starting materials.The carbon precursorsPowder Technology 212(2011)327–331⁎Corresponding authors.Tel./fax:+863783881358.E-mail address:donguser@ (X.Wang).0032-5910/$–see front matter ©2011Elsevier B.V.All rights reserved.doi:10.1016/j.powtec.2011.06.005Contents lists available at ScienceDirectPowder Technologyj o u r n a l h o me p a g e :w w w.e l sev i e r.c o m /l oc a t e /pow t e care soluble starch(50.0g/1mol LiOH·H2O),sucrose(35.0g/1mol LiOH·H2O),citric acid monohydrate(21.0g/1mol LiOH·H2O),respec-tively.These carbon precursors were respectively solved in an appropri-ate amount of distilled water under stirring and heating.Then the amorphous FePO4and LiOH·H2O were added under vigorous stirring. Subsequently,the mixtures were respectively dried in an oven at120°C for6h,heated at350°C for1h in argonflow,treated at750°C for12h in argonflow,and ground.Finally,the LiFePO4/C composites were obtained and were denoted as sample A,sample B and sample C,respectively. 2.2.2.Method twoIn a typical synthesis,0.10g of CTAB was solved in30ml of distilled water solution under continuous stirring.Subsequently,1.52g FePO4·3H2O,0.055g resorcinol(R)and0.10ml formaldehyde(F)were successively added.When the temperature of water bath was up to85°C,LiOH·H2O was added.The mixture was kept stirred up in the dark for2h,dried in an oven at120°C for6h,heated at 350°C for1h in argonflow,treated at750°C for12h in argonflow, andfinally ground to obtain the LiFePO4/C composites(denoted as sample D).These four samples and their corresponding parameters are listed in Table1.The carbon contents of the samples were calculated by the loss on ignition of the four LiFePO4/C composites in air.2.3.CharacterizationThermogravimetric(TG)and differential thermal analysis(DTA) analyses were conducted with an EXSTAR6000thermal analysis system at a heating rate of10°C min−1.The powder X-ray diffraction (XRD,X'Pert Pro MPD,Philips)using Cu Ka radiation was employed to identify the crystalline phase of the prepared materials.Raman spectrum was recorded on a Renishaw RM-1000Microscopic Raman spectrometer with457.5nm excitation requiring a10mW power at room temperature.Low-magnification and high-magnification TEM images were taken on a JEM-2010transmission electron microscope (using an accelerating voltage of200kV).Electrodes were fabricated from a mixture of prepared carbon-coated LiFePO4powders(80wt.%),carbon black(12wt.%),and polyvinylidenefluoride in N-methylpyrrolidinon(8wt.%).The slurry was spread onto Al foil and dried in vacuum at120°C for12h.The carbon-coated LiFePO4loading was2mg cm−2in the experimental cells.The cells were assembled in an argon-atmosphere-filled glove box.The electrolyte was1M LiPF6in a mixture of ethylene carbonate (EC)and dimethyl carbonate(DMC)(1:1volume).The cells were galvanostatically charged and discharged at a voltage range of2.5–4.2V with LAND battery testing system at room temperature.Cyclic voltammograms were run on an IM6impedance and electrochemicalmeasurement system(Zahner,Germany)at a scan rate of0.1mV s−1 between2.5and4.0V.3.Results and discussionThe TEM images of the amorphous nano-FePO4were shown in Fig.1.The morphology of the as-prepared FePO4is an irregular particle with an average diameter of30nm.Most of the particles connected to each other because of their high surface energy which results from their small sizes.Fig.2a shows the TG/DTA curves of the FePO4·3H2O powder with a heating rate of10°C/min from room temperature to850°C in air.On the DTA curve near150°C,there is a very strong endothermic peak, associating with the sharp weight loss on the TG curve,which is related to the quick dehydration of FePO4·3H2O.During150–550°C, 26.3%weight loss on the TG curve indicates the slow elimination of residual H2O in FePO4·3H2O,exactly corresponding to the loss of crystalline water of FePO4·3H2O.And one exothermic peak is displayed at a higher temperature of590°C,which is not accompa-nied by appreciable weight loss in the TG curve,indicating the transformation of the amorphous FePO4to hexagonal FePO4crystal. The XRD patterns of FePO4·3H2O before and after calcination have been investigated in Fig.2b.As illustrated in pattern A,it can be seen that there is no evidence of diffraction peaks before calcination, indicating the synthesized FePO4·3H2O is just amorphous.While for the calcinated FePO4·3H2O at600°C for6h in air,it exhibits strong and narrow peaks revealing a well-crystallized material in pattern B. All of the diffraction peaks of the prepared FePO4are indexed to a single-phase hexagonal structure with a P3121space group and without any impurities,which is in good agreement with the standard card(JCPDS card no:72–2124).Table1Carbon precursors and residual carbon content of samples A,B,C and D.Samples A B C DCarbon precursor Starch Sucrose Citric acid RF polymer Final carbon content(wt.%) 5.48.5 4.35.1Fig.1.TEM images of the prepared amorphous nano-FePO4.n et al./Powder Technology212(2011)327–331The XRD diffraction patterns of LiFePO 4/C powders prepared with different carbon precursors were shown in Fig.3.All peaks can be indexed as a single phase with an ordered olivine structure indexed to the orthorhombic space group,Pnmb (JCPDS card no.83–2092).The obtained lattice parameters are sample A:a=10.2956Å,b=6.0367Å,and c =4.7001Å,sample B:a =10.1992Å,b =6.0483Å,andc=4.6971Å,sample C:a=10.2472Å,b=6.0208Å,and c=4.6882Åand sample D:a=10.3372Å,b=5.9993Å,and c=4.6932Å,respec-tively.There is no evidence of diffraction peaks for carbon,though some amorphous masses and films attached to the LiFePO 4particles were observed from TEM images (see Fig.4).This indicates the carbon contents are very low.Morphologies of these LiFePO 4/C composites were shown in Fig.4.It is obvious that the samples show different carbon distribution on LiFePO 4particle surface.From Fig.4a,c,e and g,we observed that the samples were composed of agglomerated particles whose sizes range from 50to 300nm.From Fig.4b and d,there is not enough carbon coating to spread throughout the substrate particles.In contrast to sample A and sample B,there are uniform carbon thin films on the grain surfaces of sample C and sample D,and the thickness of the carbon films are about 2.5nm (Fig.4f)and 4.5nm (Fig.4h),respectively.The reason may lie in that different carbon precursors have different adsorbabilities on the surface of FePO 4·3H 2O particles,resulting in different carbon distribution on the surface of LiFePO 4particle after the post treatment.Soluble starch and sucrose possess plentiful hydroxyl groups,by which soluble starch and sucrose molecules could probably weakly adsorb on the surface of FePO 4·3-H 2O particles in the hydrogen bonding.In the post treatment process,part of soluble starch and sucrose molecules desorbed from the surface of FePO 4·3H 2O particles,resulting in the de ficient carbon coating.But citric acid possesses carboxyl groups,which may be partially esteri fied by hydroxyl groups on the FePO 4·3H 2O particles,forming a tight connection.This results in more complete carbon coating after the post treatment.For sample D,we suppose that,in the present synthetic system,the surfactant CTAB may con fine the resorcinol –formaldehyde (RF)polymer molecules and FePO 4·3H 2O particles in plenty of tiny spaces,so the RF polymer molecules were tightly attached to FePO 4·3H 2O particles.After the post treatment,the RF polymer was transformed into the carbon film which tightly stuck on the surface of LiFePO 4particle.In addition,from the HRTEM image of sample D (shown in Fig.4h),the d-spacing of 0.294nm corresponds to the (211)plane of LiFePO 4.As an important aid investigating the structure of the carbon,the Raman measurement was adopted,and the results were shown in Fig.5.Every Raman spectrum consists of a small band at 940cm −1,which corresponds to the symmetric PO 4stretching vibration in LiFePO 4.The intense broad bands at 1350and 1590cm −1can be attributed to the characteristic Raman spectra of carbon.The bands at 1590cm −1mainly correspond to graphitized structured carbon of G band,while that at 1350cm −1corresponds to disordered structured carbon of D band [22,23].The graphitized carbon contains sp 2hybrid bonding,which is positively correlated with the electronic conduc-tivity of carbon,and the disordered carbon mainly corresponds to sp 3hybrid bonding.As shown in Fig.5,the integrated intensity ratios of sp 2/sp 3of the LiFePO 4/C composites synthesized with different carbon precursors are 0.865(curve A),0.857(curve B),0.856(curve C)and 0.860(curve D),respectively.So the similar sp 2/sp 3ratios of the four samples give us few clues to explain the difference in their electrochemical performances.Fig.6shows the cycling performance curves of all the samples at different rates.As shown in Fig.6,the initial discharge capacities of sample A,sample B,sample C and sample D at room temperature at 0.2C rate are 110.4,118.8,137.7and 138.4mAh g −1,respectively.The capacity of sample D gradually increases in the initial cycles.This may be due to the incomplete dispersion of the electrolyte into the electrode material at the beginning.Moreover,the capacity of sample D is highest among the four samples at 0.5C and 1.0C,indicating that method two is better than method one.The lower capacities of sample A and sample B must be due to the incomplete carbon coating on the LiFePO 4particles.The higher capacity of sample D than that of sample C may be attributed to the thicker carbon film of sample D keeping the crystal structure of LiFePO 4morestable.Fig.2.(a)TG/DTA curves of the FePO 4·3H 2O.(b)XRD patterns of the FePO 4samples before (A)and after (B)calcination inair.Fig. 3.XRD patterns of LiFePO 4/C composites synthesized with different carbon precursors.329n et al./Powder Technology 212(2011)327–331In order to further understand the electrochemical properties of the four samples,the cyclic voltammogram (CV)curves were performed at a scan rate of 0.1mV s −1at room temperature (as shown in Fig.7).Each of the CV curves consists of an oxidation peak and a reduction peak,corresponding to the charge reaction and discharge reaction of the Fe 2+/Fe 3+redox couple.In the CV pro files of the LiFePO 4cathode material,the smaller voltage difference between the charge and discharge plateaus and the higher peak current means better electrode reaction kinetics,and consequently better rate performance.Sample A and sample B electrodes have broad peaks in CV curves.In contrast,sample C and sample D electrodes demonstrate sharp redox peaks,which indicate an improvement in the kinetics of the lithium intercalation/de-intercalation at the electrode/electrolyte interface.The voltage difference of sample D is smaller than that of sample C,so sample D demonstrates a better rate performance.4.ConclusionsLiFePO 4/C composites were synthesized by two methods using home-made amorphous nano-FePO 4as the iron precursor and various organics as carbon precursors.It was found that employing soluble starch and sucrose as the carbon precursors resulted in a de ficient carbon coating on the surface of LiFePO 4particle,but employing citric acid and RF polymer as the carbon precursors realized a uniform carbon coating on the surface of LiFePO 4particle.Particularly,when RF polymer was used as the carbon precursor,the carbon film is thicker,and the material showed the highest initial discharge capacity (138.4mAh g −1at 0.2C at room temperature)and the best rate performance among the four materials.The intensities of redox peak and the voltage differences in the CV curves of the four samples are consistent with their rateperformance.Fig.4.TEM images of synthesized LiFePO 4/C composite synthesized with different carbon precursors.(a)and (b)sample A,(c)and (d)sample B,(e)and (f)sample C,(g)and (h)sampleD.Fig. 5.Raman shift of LiFePO 4/C composites synthesized with different carbonprecursors.Fig.6.The cycling performance curves of the samples with different carbon precursors at various discharge rates.n et al./Powder Technology 212(2011)327–331References[1] A.K.Padhi,K.S.Nanjundaswamy,J.B.Goodenough,Phospho-olivines as positive-electrode materials for rechargeable lithium batteries,J.Electrochem.Soc.144(1997)1188–1194.[2]T.Nakamura,Y.Miwa,M.Tabuchi,Y.Yamada,Structural and surfacemodi fications of LiFePO 4olivine particles and their electrochemical 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Ｐｏｗｅｒｇｒｅｅｎｖｉｓｉｏｎ驱动绿色未来磷酸铁锂电池产品介绍ＴｈｅＰｒｅｓｅｎｔａｔｉｏｎｏｆＶＩＳＩＯＮＬＦＰＢａｔｔｅｒｙ深圳市雄韬电源科技有限公司ＳＨＥＮＺＨＥＮＣＥＮＴＥＲＰＯＷＥＲＴＥＣＨ．ＣＯ．，ＬＴＤｗｗｗ．ｖｉｓｉｏｎ－ｂａｔｔ．ｃｏｍＰｏｗｅｒＧｒｅｅｎＶｉｓｉｏｎ目录概述？产品系列？安全认证？ＶＩＳＩＯＮ铁锂电池优势？电池研制环境？客户案例ＰｏｗｅｒＧｒｅｅｎＶｉｓｉｏｎ一概述雄韬电源是全球最大的蓄电池生产企业之一，产品涵盖铅酸、锂电两大品类，是一个以中国深圳为管理中心，在中国大陆、欧洲、香港、东南亚拥有制造基地或营销中心、分销网络遍布全球１００多个国家和地区的企业集团。

ＶＩＳＩＯＮ磷酸铁锂电池由雄韬电源集团与香港理工大学、清华大学、湖南大学合作开发，是国家火炬计划重点项目和深圳市科技资助项目。

ＶＩＳＩＯＮ铁锂电池着眼环保与高效的绿色未来，项目自２００６年启动，成立之初即定位实用性能最好的锂离子电池；经集团研发中心与各科研院所的艰苦攻关，目前已开发出圆柱、软包、钢壳、ＰＰ四大产品系列，针对不同电流、不同容量、不同尺寸等复杂要求，满足电动汽车、电动自行车、电动工具以及其它大电流启动或高能备用市场。

我集团研发中心现有磷酸铁锂专职科研人员近５０名，并已形成从磷酸铁锂正极材料生产到成品铁锂电池制造、检测的批量供应能力。

“一站式”产品资源保证、稳定的供货能力，加上遍布全球的销售服务网络，ＶＩＳＩＯＮ磷酸铁锂电池以最佳供应成本控制模式服务全球客户。

ＰｏｗｅｒＧｒｅｅｎＶｉｓｉｏｎ磷酸铁锂电池工作原理ＬｉＦｅＰＯ４－ｘＬｉ＋－ｘｅＦｅＰＯ４＋ｘＬｉ＋＋ｘｅ－（１－ｘ）ＬｉＦｅＰＯ４＋ｘＦｅＰＯ４ｘＬｉＦｅＰＯ４＋（１－ｘ）ＦｅＰＯ４ＰｏｗｅｒＧｒｅｅｎＶｉｓｉｏｎ磷酸铁锂材料与传统电池材料的差异ＬｉＣｏＯ２ＳｔｒｕｃｔｕｒｅＯｐｅｒａｔｉｎｇｖｏｌｔａｇｅＴｈｅｏｒｅｔｉｃａｌｃａｐａｃｉｔｙＰｒａｃｔｉｃａｌｃａｐａｃｉｔｙＥｌｅｃｔｒｉｃａｌｃｏｎｄｕｃｔｉｖｉｔｙＤｉｆｆｕｓｉｖｉｔｙＴｈｅｒｍａｌｓｔａｂｉｌｉｔｙＴｏｘｉｃｉｔｙＰｒｉｃｅＬａｙｅｒｅｄ４Ｖ２７３ｍＡｈ／ｇ１６０ｍＡｈ／ｇ￣１０－３Ｓ／ｃｍ￣１０－９ｃｍ２／ｓＵｎｓｔａｂｌｅＨｉｇｈＥｘｐｅｎｓｉｖｅＬｉＭｎ２Ｏ４Ｓｐｉｎｅｌ４Ｖ１４８ｍＡｈ／ｇ１２０ｍＡｈ／ｇ￣１０－４Ｓ／ｃｍ￣１０－７ｃｍ２／ｓＵｎｓｔａｂｌｅＬｏｗＣｈｅａｐＬｉＦｅＰＯ４Ｏｌｉｖｉｎｅ３．５Ｖ１７０ｍＡｈ／ｇ１５０ｍＡｈ／ｇ￣１０－７Ｓ／ｃｍ￣１０－１６ｃｍ２／ｓＳｔａｂｌｅＬｏｗＣｈｅａｐＰｏｗｅｒＧｒｅｅｎＶｉｓｉｏｎＨｅｔｅｒｏｓｉｔｅＳｔｒｕｃｔｕｒｅ钴酸锂充放体积变化率＋３～４％锰酸锂－１～３％ＯｌｉｖｉｎｅＳｔｒｕｃｔｕｒｅ石墨＋６～７％磷酸铁锂－６～７％ＰｏｗｅｒＧｒｅｅｎＶｉｓｉｏｎｌＦｅＰＯ４分子中含有强化学键，Ｐ－Ｏ（键长Ｐ－Ｏ／Ｃｏ－Ｏ：０．１５３ｎｍ／０．１９１ｎｍ）在高于５００ｏＣ的高温下也不会释放出活性Ｏ２。

磷酸铁锂，缩写为LFP（Lithium Iron Phosphate），是一种广泛应用于锂离子电池的正极材料。

因其高安全性、长循环寿命和相对较低的成本，LFP电池在电动汽车、储能系统以及众多便携式电子设备中得到了广泛应用。

### 一、磷酸铁锂简介磷酸铁锂（LiFePO₄）是一种无机化合物，属于正交晶系。

其结构中，磷酸根离子（PO₄³⁻）与铁离子（Fe²⁺）和锂离子（Li⁺）相互作用，形成稳定的三维网络。

这种结构使得LFP具有较高的热稳定性和结构稳定性，从而在高温甚至600°C下仍能保持稳定，大大提高了电池的安全性。

### 二、性能特点1. **高安全性**：LFP电池在高温甚至600°C下仍能保持稳定，且不易燃、不爆炸，相比于其他类型的锂离子电池具有更高的安全性。

2. **长循环寿命**：由于LFP材料的结构稳定性，其电池具有非常长的循环寿命，通常可达到2000次以上充放电循环。

3. **环保**：磷酸铁锂材料中不含对人体有害的重金属元素，对环境友好。

4. **良好的电化学性能**：LFP电池具有平坦的放电平台和较高的能量密度。

### 三、应用领域1. **电动汽车**：随着电动汽车市场的快速发展，LFP电池因其高安全性和长寿命成为电动汽车动力电池的理想选择。

特别是在公交车、出租车等高频使用场景中，LFP电池的高安全性和低成本优势尤为突出。

2. **储能系统**：在可再生能源发电系统（如太阳能、风能）中，储能系统对于平衡电网负荷至关重要。

LFP电池因其长寿命、高安全性和相对较低的成本成为大规模储能系统的优选方案。

3. **便携式电子设备**：从手机、笔记本电脑到电动工具等便携式电子设备，LFP电池也因其安全性和稳定性得到了广泛应用。

4. **其他领域**：除了上述领域外，LFP电池还可应用于无人机、航空航天、军事等领域。

### 四、发展前景随着科技的不断进步和环保意识的日益增强，对电池的性能要求也越来越高。

锂离子电池正极材料覆碳LiFePO4的制备和表征摘要：用两种方法合成纳米LiFePO4/C复合材料，用国产的非晶体纳米FePO4作离子前驱体，可溶性淀粉、蔗糖、柠檬酸和间苯二酚甲醛聚合物四种物质分别作碳的前驱体。

其中可溶性淀粉、蔗糖、柠檬酸作碳前驱体时用第一种方法合成，间苯二酚甲醛聚合物作碳前驱体时用第二种方法合成。

得到样品后用XRD,TEM ,拉曼波谱和循环伏安法对制得样品的晶体结构，形貌，相成分以及电化学特性进行测试研究。

研究结果显示用可溶性淀粉和蔗糖作碳的前驱体制得的LiFePO4颗粒表面的碳的包覆层不充分,而用柠檬酸和间苯二酚甲醛聚合物作前驱体所得的样品实现了在LiFePO4颗粒表面得到均匀一致的碳包覆层的目的，并且相应的碳包覆层的厚度分别为2.5 nm和4.5 nm。

在制得的四种样品中，使用间二苯酚甲醛聚合物作碳的前驱体时，样品的首次放电比容量最高（室温下0.2 C 时放电比容量为138.4 mAh/ g）,倍率性能最好。

第一章引言LiFePO4作为锂离子电池正极材料由于其理论比容量高（170mAh/g），环保，热稳定性好而受到广泛关注。

然而其低于10−13Scm−1的电导率限制了其电池性能【1】，例如在高电流密度下功率的显著减小是其商业化发展的主要障碍。

目前人们已经引进了很多有效的方法克服LiFePO4电导率低的缺点，诸如金属替换法【2-5】，金属粉末混合法【6】，以及传导性碳包覆法【7-15】，通过形成良好的导电通路来提高最终产物的电导率。

在这些方法中，制备LiFePO4/C 复合材料是最受关注的。

此外，碳还可以用作还原剂使Fe3+降价为Fe2+。

值得提及的是包括纳米尺寸的磷酸铁锂的合成在内的很多研究用昂贵的Fe2+盐作前驱体【3.16-20】，例如FeC2O4·2H2O 和(CH 3COO)2Fe。

因此，研究新的制备方法和应用廉价的材料对磷酸铁锂作为锂离子电池正极材料的产业发展至关重要。

磷酸铁锂磷酸铁锂全文共四篇示例，供读者参考第一篇示例：磷酸铁锂（Lithium Iron Phosphate，简称为LiFePO4）是一种新型的锂离子电池正极材料，具有理论容量高、循环寿命长、安全性高等优点，被广泛应用于电动汽车、电动自行车、储能系统等领域。

磷酸铁锂电池的发展历程可以追溯到上世纪90年代初，当时由美国的约翰·戴巴特（John Goodenough）和其团队发明了这种材料。

磷酸铁锂之所以备受关注和广泛应用，主要还是因为它的优点远远超过其他传统的锂电池材料。

磷酸铁锂的理论容量相对较高，可以达到170mAh/g左右。

这意味着相同体积下，能够存储更多的电荷，使得电池具有更高的能量密度。

电动汽车和储能系统所使用的磷酸铁锂电池，可以实现更长的续航里程和更持久的储能效果。

磷酸铁锂电池的循环寿命也非常长，可以达到2000次以上，比传统的锂电池材料要高出许多。

这意味着使用磷酸铁锂电池的设备可以更加稳定和持久地工作，减少更换电池的频率，降低维护成本。

磷酸铁锂电池具有较高的安全性。

由于其结构稳定，即使在高温、短路等极端条件下，也不容易发生热失控、爆炸等危险情况。

这使得磷酸铁锂电池成为电动汽车等领域的首选材料，因为安全性对于这些设备来说至关重要。

除了上述优点之外，磷酸铁锂电池还具有低自放电率、较低的成本等特点。

低自放电率意味着即使长时间不使用，电池也不会快速失去电荷，保持较长的续航时间。

而相对于其他高容量材料如钴酸锂等，磷酸铁锂的成本较低，使得其在大规模应用中具有一定的优势。

第二篇示例：磷酸铁锂（LiFePO4）是一种新型的锂离子电池正极材料，具有高容量、高循环寿命、高安全性等优点，在锂离子电池领域有着广泛的应用。

磷酸铁锂作为目前电动车、储能设备等领域中最为热门的正极材料之一，被誉为“锂电池之王”。

磷酸铁锂电池具有许多优点。

磷酸铁锂电池的循环寿命长，可以循环充放电数千次而不损坏电池性能，通常寿命可以达到2000次以上，远高于其他类型的锂离子电池。

The design of the lithium battery charger IntroductionLi-Ion rechargeable batteries are finding their way into many applications due to their size, weight and energy storage advantages.These batteries are already considered the preferred battery in portable computer applications, displacing NiMH and NiCad batteries, and cellular phones are quickly becoming the second major marketplace for Li-Ion. The reason is clear. Li-Ion batteries offer many advantages to the end consumer. In portable computers,Li-Ion battery packs offer longer run times over NiCad and NiMH packs for the same form factor and size, while reducing weight. The same advantages are true for cellular phones. A phone can be made smaller and lighter using Li-Ion batteries without sacrificing run time. As Li-Ion battery costs come down, even more applications will switch to this lighter and smaller technology. Market trends show a continual growth in all rechargeable battery types as consumers continue to demand the convenience of portability. Market data for 1997 shows that approximately 200 million cells of Li-Ion will be shipped, compared to 600 million cells of NiMH. However, it is important to note that three cells of NiMH are equivalent to one Li-Ion cell when packaged into a battery pack. Thus, the actual volume is very close to the same for both. 1997 also marked the first year Li-Ion was the battery type used in the majority of portable computers, displacing NiMH for the top spot. Data for the cellular market showed a shift to Li-Ion in the majority of phones sold in 1997 in Europe and Japan.Li-Ion batteries are an exciting battery technology that must be watched. To make sense of these new batteries, this design guide explains the fundamentals, the charging requirements andthe circuits to meet these requirements.Along with more and more the emergence of the handheld electric appliances, to the high performance, baby size, weight need of the light battery charger also more Come more big.The battery is technical to progress to also request continuously to refresh the calculate way more complicatedly is fast with the realization, safety of refresh.Therefore need Want to carry on the more accurate supervision towards refreshing the process, to shorten to refresh time and attain the biggest battery capacity, and prevent°from the batteryBad.The AVR has already led the one step in the competition, is prove is perfect control chip of the next generation charger. The microprocessor of Atmel AVR is current and can provide Flash, EEPROM and 10 ADCses by single slice on the market Of 8 RISC microprocessors of the tallest effect.Because the saving machine of procedure is a Flash, therefore can need not elephant MASK ROM Similar, have a few software editions a few model numbers of stock.The Flash can carry on again to weave the distance before deliver goods, or in the PCB Stick after pack carry on weaving the distance throughan ISP again, thus allow to carry on the software renewal in the last one minute.The EEPROM can used for conservancy mark certainly coefficient and the battery characteristic parameter, such as the conservancy refreshes record with the battery that raise the actual usage Capacity.10 A/ Ds conversion machine can provide the enough diagraph accuracy, making the capacity of the good empress even near to its biggest capacity. And other project for attaining this purpose, possible demand the ADC of the exterior, not only take up the space of PCB, but also raised the system Cost.The AVR is thus deluxe language but 8 microprocessors of the designs of unique needle object" C" currently.The AT90S4433 reference The design is with" C" to write, the elucidation carries on the software design's is what and simple with the deluxe language.Code of C this design is very Carry on adjust easily to suit current and future battery.But the ATtiny15 reference design then use edit collected materials the language to write of, with Acquire the biggest code density.An electric appliances of the modern consumption mainly uses as follows four kinds of batteries:1.Seal completely the sour battery of lead( SLA)2.The battery of NiCd3.The NiMHhydrogen battery( NiMH)4.Lithium battery( Li- Ion)At right choice battery and refresh the calculate way need to understand the background knowledge of these batteries. Seal completely the sour battery( SLA) of lead seals completely the sour battery of lead to mainly used for the more important situation of the cost ratio space and weights, such as the UPS and report to the police the backup battery of the system. The battery of SLA settles the electric voltage to carry on , assist limits to avoid with the electric current at refresh the process of early battery lead the heat.Want ～only the electricity .The pond unit electric voltage does not exceed the provision( the typical model is worth for the 2.2 Vs) of produce the company, the battery of SLA can refresh without limit. The battery of NiCd battery of NiCd use very widespread currently.Its advantage is an opposite cheapness, being easy to the usage;Weakness is from turn on electricity the rate higher.The battery of NiCd of the typical model can refresh 1,000 times.The expired mechanism mainly is a pole to turn over.The first in the battery pack drive over.The unit that all turn on electricity will take place the reversal.For prevent°froming damage the battery wrap, needing to supervise and control the electric voltage without a break.Once unit electric voltage Descend the 1.0 Vs must shut down.The battery of NiCd carries on refresh in settling the electric current by forever . The NiMH hydrogen battery( NiMH) holds to shoot the elephant machine such as the cellular phone, hand in the hand that the importance measure hold equipments, the etc. NiMHhydrogen battery is anusage the most wide.This kind of battery permit.The quantity is bigger than NiCd's.Because lead to refresh and will result in battery of NiMH lose efficacy, carry on measuring by the square in refresh process with.Stop is count for much in fit time.Similar to battery of NiCd, the pole turn over the battery also will damage.Battery of NiMH of from turn on electricity the rate and is probably 20%/ month.Similar to battery of NiCd, the battery of NiMH also settles the electric current to refresh .Other batteries says compare in lithium battery( Li- Ion) and this texts, the lithium battery has the tallest energy/ weight to compare to compare with energy/ physical volume.Lithium batterySettle the electric voltage to carry on refresh with , want to have the electric current restrict to lead the heat in the early battery of refresh the process by avoid at the same time.When refresh the electric current Descend to produce the minimum electric current of the enactment of company will stop refresh.Leading to refresh will result in battery damage, even exploding.The safety of the battery refreshes the fast charge machine( namely battery can at small be filled with the electricity in 3 hours, is usually a hour) demand of the modern.Can to the unit electric voltage, refresh the electric current and the battery temperatures to carry on to measure by the square, avoid at the time of being filled with the electricity because of leading to refresh.Result in of damage.Refresh the method SLA battery and lithium batteries refreshes the method to settle the electric voltage method to want to limit to flow for the ever ; The battery of NiCd and battery of NiMHs refresh the method.Settle the electric current method for the ever , and have severals to stop the judgment method for refresh differently. Biggest refresh the electric current biggest refresh the electric current to have relation with battery capacity( C).Biggest usually refresh the electric current to mean with the number of the battery capacity.For example,The capacity of the battery for 750 mAhs, refresh the electric current as 750 mAs, then refresh the electric current as 1 C(1 times battery capacity).IfThe electric current to flow refresh is a C/40, then refreshing the electric current for the battery capacity in addition to with 40.Lead the hot battery refresh is the process that the electric power delivers the battery.Energy by chemical reaction conservancy come down.But is not all.The electric powers all convert for the sake of the chemistry in the battery ability.Some electric power conversions became the thermal energy, having the function of the heating to the battery.When electricity.After pond be filled with, if continue to refresh, then all electric powers conversion is the thermal energy of the battery.At fast charge this will make the battery.Heat quickly, if the hour of can not compare with stop refresh and then willresult in battery damage.Therefore, while design the battery charger, to the temperature.It is count for much that carry on the supervision combine to stop refresh in time.The discretion method battery stopped refresh of different and applied situation and work environment limitted to the choice of the method that the judgment stop refresh.The sometimes temperature allow of no.Measure easily, but can measure electric voltage, or is other circumstances.This text takes the electric voltage variety rate(- dV/ dt) as the basic judgment to stopThe method for refresh, but with the temperature and absolute electric voltage be worth for assistance and backup.But the hardware support that this text describe speaks as follows.The method of the havings of say. Time of t – this method that is the decision when stop refresh most in ually used for spare project of the hour of fast charge.Sometimes also be .Refresh(14- 16 Hour) basic project of the method.Be applicable to various battery.Stop refresh when the electric voltage of V – be the electric voltage to outrun the upper ually with the forever settle the electric current refreshes the match usage.The biggest electric current is decide by the battery, usually For the 1 C.For prevent°froming refresh the electric current leads to causes battery lead greatly hot, the restrict of the electric current at this time very key.This method Is a lithium battery basic to refresh and stop project. The actual lithium battery charger usually still continues into after attain biggest electric voltage Go the second stage refresh, to attain 100% battery capacity. For battery of NiCd and battery of NiMHs are originally method can Be the spare judgment stops refreshing the project. - The method exploitation that this judgment of the dV/ dt – electric voltage variety rate stops refresh negative electric voltage variety rate.For the battery of some types, be the battery to be filled with the subsequence Refreshing continuously will cause electric voltage descend. At this time this project was very fit.This method usually useds for the ever to settle the electric current to refresh, Be applicable to to the fast charge of the battery of NiCd and battery of NiMH. The electric current of I –is to refresh the electric current small in a certain the number that set in advance stop refresh. Usually used for the ever to settle the electric voltage to refresh the method.Be applicable to the SLA Battery and lithium battery.The T – temperature absolute zero can be the basis that battery of NiCd and battery of NiMHs stop refresh, but even suited for to be the backup project.Any battery for temperature to outrun initial value have to stop refresh.The basis that the dT/ dt –temperature rising velocity fast charge variety rate of the temperature of hour can be to stop refresh.Please consult the norm that the battery produces the company( battery of NiCdOf typical model be worth for the 1 oC/ min) the –be applicable to the battery of NiCd and battery of NiMHs.Need to stop refresh when the DT – outrun the temperature value of theenvironment temperature to be the bad battery temperature and the environment temperature to exceed the certain threshold.This method can be the battery of NiCd and The project that battery of SLA stops refresh.While refreshing in the cold environment this method compares the absolute zero to judge the method better.Because bigMost systems usually only have a temperature to stretch forward, have to will refresh the previous temperature to be the environment temperature. DV/ dt=0 –s zero electric voltages differ this method with- the method of dV/ dt is very and similar, and more accurate under the condition that electric voltage will not go up again. Be applicable to the NiCd Battery and battery of NiMH.This reference design completely carried out the battery charger design of latest technique, can carry on to various popular battery type quicklyRefresh but need not to modify the hardware soon, a hardware terrace carries out a charger product line of integrity.Need only Want to will refresh the calculate way to pass lately the ISP downloads the processor of FLASH saving machine can get the new model number.Show very muchHowever, this kind of method can shorten time that new product appear on market consumedly, and need a kind of hardware of stock only.This design provide The in keeping with SLA, NiCd, NiMH of the integrity and the database function of the battery of Li- Ion.锂电池充电器的设计介绍根据其尺寸，重量和能量储存优点，锂- 离子可再充电电池正在被用于许多的应用领域。

ISSN 1674-8484CN 11-5904/U 汽车安全与节能学报, 2011年, 第2卷第1期J Automotive Safety and Energy, 2011, Vol. 2 No. 1Manufacture and Performance Tests of Lithium Iron PhosphateBatteries Used as Electric Vehicle PowerZHANG Guoqing, ZHANG Lei, RAO Zhonghao, LI Yong(Faculty of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, ChinaAbstract: Owing to the outstanding electrochemical performance, the LiFePO 4 power batteries could be used on electric vehicles and hybrid electric vehicles. A kind of LiFePO 4 power batteries, Cylindrical 26650, was manufactured fromcommercialized LiFePO 4, graphite and electrolyte. To get batteries with good high-current performance, the optimal content of conductive agent was studied and determined at 8% of mass fraction. The electrochemical properties of the batteries were investigated. The batteries had high discharging voltage platform and capacity even at high discharge current. When discharged at 30 C current, they could give out 91.1% of rated capacity. Moreover, they could be fast charged to 80% of rated capacity in ten minutes. The capacity retention rate after 2 000 cycles at 1 C current was 79.9%. Discharge tests at -20 ℃ and 45 ℃ also showed impressive performance. The battery voltage, resistance and capaci ty varied little after vibration test. Through the safety tests of nail, no in fl ammation or explosion occurred.Key words: hybrid and electric vehicles; power batteries; lithium iron phosphate; lithium ion batteries;电动汽车用磷酸铁锂动力电池的制作及性能测试张国庆、张磊、饶忠浩、李雍( 广东工业大学材料与能源学院,广州 510006, 中国摘要: 磷酸铁锂电池的优异性能使其可以应用在电动汽车和混合动力汽车上。

磷酸铁锂磷酸铁锂（分子式：LiMPO4，英文：Lithium iron phosphate，又称磷酸铁锂、锂铁磷，简称LFP），是一种锂离子电池（可另外参见锂电池）的正极材料，也称为锂铁磷电池，特色是不含钴等贵重元素，原料价格低且磷、锂、铁存在于地球的资源含量丰富，不会有供料问题。

其工作电压适中（3.2V）、电容量大（170mAh/g）、高放电功率、可快速充电且循环寿命长，在高温与高热环境下的稳定性高。

这个看似不起眼却引发锂电池革命的新材料，为橄榄石结构分类中的一种，矿物学中的学名称为triphyllite，是从希腊字的tri-以及fylon两个字根而来，在矿石中的颜色可为灰色，红麻灰色，棕色或黑色。

化学式LiFePO4正确的化学式应该是LiMPO4，物理结构则为橄榄石结构，而其中的M 可以是任何金属，包括Fe、Co、Mn、Ti等等，由于最早将LiMPO4商业化的公司所制造的材料是C/LiFePO4，因此大家就这么习惯地把Lithium iron phosphate其中的一种材料LiFePO4当成是磷酸铁锂。

然而从橄榄石结构的化合物而言，可以用在锂离子电池的正极材料并非只有LiMPO4一种，据目前所知，与LiMPO4相同皆为橄榄石结构的Lithium iron phosphate 正极材料还有A y MPO4、Li1-x MFePO4、LiFePO4･MO 等三种与LiMPO4不同的橄榄石化合物（均可简称为LFP）。

发现自1996年日本的NTT首次揭露A y MPO4（A为碱金属，M 为Co Fe 两者之组合：LiFeCoPO4）的橄榄石结构的锂电池正极材料之后，1997年美国得克萨斯州立大学John. B. Goodenough 等研究群，也接着报道了LiFePO4的可逆性地迁入脱出锂的特性[1]，美国与日本不约而同地发表橄榄石结构（LiMPO4），使得该材料受到了极大的重视，并引起广泛的研究和迅速的发展。