LiFeP 2011

Journal of Power Sources 196 (2011) 28412847

Contents lists available at ScienceDirect

Journal of Power Sources

journa l homepage: www.e lsev ier .com

A nove tostructu

Wenxiu WaHongmeInstitute of New (MOE)

a r t i c l

Article history:Received 2 AuReceived in reAccepted 21 OAvailable onlin

Keywords:Solgel methoLithium iron pCathode mateLithium-ion ba

ateriaorusPO42r struormlyts higth cyrate

romest in

1. Introduction

Since the pioneering work of Goodenough and co-workers in1997 [1], olivine structured lithium iron phosphate, LiFePO4, hasbeen recogbatteries. Cothe advantcost, nontorepeatabilition conductnal ideas haconductiveoxide [5] on[8] into theticle size [9methods cotion [11], so[14], hydrotsion dryingtechnology

Among ttive, becausat an atomproducts an

CorresponE-mail add

methods, water-soluble iron (II)/(III) salts were usually chosenas iron sources such as FeCl2 [22], Fe(CH3COO)2 [23], Fe(NO3)3[24], Fe(III)-citrate [25,26] and so on, but they brought on highsynthesis cost, especially for iron (II) salts. There were seldom

0378-7753/$ doi:10.1016/j.nized as a promising cathode material for lithium ionmparedwith other cathodematerials, LiFePO4 exhibits

ages of high theoretical capacity (170mAhg1), lowxicity, excellent thermal safety, high reversibility andy and so on. But its intrinsic low electronic and lithiumivities hold back the practical application. Many origi-ve been tried to solve these problems, such as coatingmaterials-carbon [2], metal [3], polymer [4] or metalthe particles, doping supervalent cations [6,7] or anionolivine structure and, especially, minimizing the par-] with different synthesis methods. These synthesisntain solid-state reaction [10], carbon thermal reduc-lgel [12], co-precipitation [13], microwave processeshermal route [15], solvothermalmethod [16,17], emul-synthesis [18], vapor deposition [19], spray solution[20] and pulsed laser deposition [21] and so on.hese synthesis methods, solgel is particularly attrac-e all reactants could be homogeneously mixed evenic level, which is favorable to synthesize small pured well-distributed particles. In the reported solgel

ding author. Tel.: +86 22 23498089; fax: +86 22 23502604.ress: [email protected] (L. Jiao).

reports using cheap water-insoluble iron (II)/(III) salts as ironsources with solgel methods but being introduced in othersynthesismethods. KangandCeder1 [27] obtainedLiFePO4/Cmate-rial with the size of about 50nm by solid-state reaction usingFeC2O42H2Oas iron sourceand it showedgoodhigh-ratedischargeperformances, about 140mAhg1 at 20C rate.Wang et al. [28] syn-thesized LiFePO4/C with the size ranging from 100 to 300nm fromFePO44H2O througha solidliquidphase reactionusing (NH4)2SO3as reducing agent, followed by thermal conversion of intermedi-ate NH4FePO4 in LiCOOCH32H2O. Huang et al. [29] synthesizedLiFePO4/C composite with 100200nm in size by a soluble starchsol assisted rheological phasemethod using nano-FePO4 as the ironsource. It also indicated good high-rate discharge performances,about 72mAhg1 at 30C rate. Zheng et al. [30] obtained nanoLiFePO4/C by heating amorphous LiFePO4/C, which was synthe-sized through lithiation of FePO4xH2O by using oxalic acid asreducing agent. It exhibited a discharge capacity of 166mAhg1

at 0.1C rate. Sinha et al. [31] prepared LiFePO4/C nanoplates fromFePO4 and LiOH by a simple polyol route, and obtained dischargecapacities of 160 and 100mAhg1 at 0.15 and 3.45C, respectively.

In this paper, we describe a novel solgel method using cheapwater-insoluble FePO42H2O as both iron and phosphorus sourcesand oxalic acid as both complexant and reductant to form trans-parent sols without controlling the pH value, which has not been

see front matter 2010 Elsevier B.V. All rights reserved.jpowsour.2010.10.065l solgel method based on FePO42H2Ored LiFePO4/C cathode material

Peng, Lifang Jiao , Haiyan Gao, Zhan Qi, Qinghongi Du, Yuchang Si, Yijing Wang, Huatang YuanEnergy Material Chemistry, Key Laboratory of Advanced Energy Materials Chemistry

e i n f o

gust 2010vised form 7 October 2010ctober 2010e 29 October 2010

dhosphaterialttery

a b s t r a c t

Carbon coated LiFePO4/C cathode mFePO42H2O as both iron and phosphand reductant. In H2C2O4 solution, Feling the pH value. Pure submicrometefrom100 to 500nm,which is also unifsynthesized LiFePO4/C sample exhibia capacity retention of 98.7% after 50formances, about 106mAhg1 at 10CLiFePO4/C are ascribed to its submicsolgel method may be of great intere/ locate / jpowsour

synthesize submicrometer

ng,

, MOE (IRT-0927), Nankai University, Tianjin 300071, PR China

l is synthesized with a novel solgel method, using cheapsources and oxalic acid (H2C2O42H2O) as both complexantH2O is very simple to form transparent sols without control-ctured LiFePO4 crystal is obtained with a particle size rangingcoatedwith a carbon layer, about 2.6nm in thickness. The as-h initial discharge capacity 160.5mAhg1 at 0.1C rate, withcle. The material also shows good high-rate discharge per-. The improved electrochemical properties of as-synthesizedter scale particles and low electrochemical impedance. Thethe practical application of LiFePO4/C cathode material.

2010 Elsevier B.V. All rights reserved.

2842 W. Peng et al. / Journal of Power Sources 196 (2011) 28412847

reported in the previous paper. The reacting mechanism andelectrochemical performances were also investigated. The solgelmethod would be attractive in the commercial application ofLiFePO4 cathode material.

2. Experim

2.1. Prepara

LiFePO4/method froand oxalicThese reactstirred at 9were placecursors. Aftpreheatedto room temlet again anLiFePO4/C s

2.2. Charac

Thermogtigated onroom temp5 Cmin1.RigakuD/MThe morphelectron mwith aTecnbon contenelemental a

2.3. Cell ass

ElectrocLi test cell.as separatoin ethylenedimethyl caodemateriapolytetrautest cells w

2.4. Electro

Galvanoon a Land Csities in a vo(CV) was reworkstation(0.12mVswas alsomefrequency rthe electrocwith the sa

3. Results

Oxalic aLiFePO4/C swhich acts ais described

FePO4 + 3H

2H3PO4 + 2H3Fe(C2O4) + 2LiOH 2LiFePO4 + 7CO2+5CO + 7H2O (2)

over

4+6Hhe reutions toasibilatio

4

4]

[(C2

O4)]+

O4)2]

Feur syreationed cd readecrein rethelso b

O4)3

Ka1 (nstapwisubiliof Hing4]0coule sud waparre sothatransC2O4sis cbeingvery

acide ina mid durestrnd w

ateri

1 is t5 C. Theisplallyental

tion of LiFePO4/C

C material was synthesized with a novel solgelm a stoichiometric mixture of FePO42H2O, LiOHH2Oacid (H2C2O42H2O), with glucose as carbon source.ants were dissolved into distilled water and strongly0 C until a light green clear sol was formed. Then theyd into an oven and kept at 90 C to form xerogel pre-er being ground, they were pressed into a pellet andat 300 C for 6h under Ar atmosphere. After cooledperature, the pellet was ground, pressed into a pel-

d calcined at 600 C for 6h in Ar atmosphere. Finally,ubmicrometer-crystal was obtained.

terization of LiFePO4

ravimetric (TG) analysis of the precursor was inves-a STA904 apparatus in the temperature range fromerature to 700 C under Ar ow with a heating rate ofX-ray diffraction (XRD) pattern was recorded using aax III diffractometerwithCuK radiation (=1.5418 A).ology was observed using a Hitachi S-3500N scanningicroscope (SEM). The inner microstructure was testedai 20 transmission electronmicroscrope (TEM). TheCar-t was analyzed by a Perkin-Elmer 2400 Series II CHNS/Onalyzer.

embly

hemical performances of LiFePO4/C were evaluated inLithium metal was used as anode and Celgard 2320r. The electrolyte was composed of 1M LiPF6 dissolvedcarbonate (EC), ethylene methyl carbonate (EMC) andrbonate (DMC) with a volume ratio of 1:1:1. The cath-l containedLiFePO4 activematerial, acetyleneblackandoroethylene (PTFE) with a weight ratio of 80:15:5. Theere assembled in an argon-lled dry glove box.

chemical tests

static charge/discharge measurements were operatedT2001 automatic battery tester at different current den-ltage range of 2.54.2V at 25 C. Cyclic voltammogramcorded with a Zahner-Elektrik IM6e electrochemicalin the potential range of 2.54.2V at various scan rates

1) at 25 C. Electrochemical impedance spectrum (EIS)asuredwith the same electrochemical workstation in aange of 10kHz10mHz. It is necessary to point out thathemical tests were carried out using active materialsme weight.

and discussion

cid plays an important role in the preparation ofubmicrometermaterial with this novel solgelmethod,s both complexant and reductant. The reaction processaccording to the following steps:

2C2O4 H3Fe(C2O4)3 + H3PO4 (1)

The

2FePO

As tthe solchangeThe fesix equ

H2C2O

[HC2O

Fe3+ +[Fe(C2

[Fe(C2

FePO4

In olibriumdissoluincreasforwarto theFePO4

Andcould a

{[Fe(C2wheretion coare stethe soltrationAccord[H2C2Owhichods: thdistille

Comthere atant isform tity of (syntheneedsFe3+ isweakdissolvacid isreleasewouldsmall a

3.1. M

Fig.rate ofspherecurve dphysicall reaction could be expressed as:

2C2O4+2LiOH 2LiFePO4+7CO2+5CO+7H2O (3)actants gradually dissolved, reaction (1) takes place andgradually becomes yellow. At last, the yellow solutionclear aqua, indicating Fe3+ coordinated by oxalic acid.ity of reaction (1) could be explained according to thens from (4) to (9).

H+ + [HC2O4] Ka1 (4)H+ + [C2O4]2 Ka2 (5)

O4)]2 [Fe(C2O4)]+ K1 (6)

+ [(C2O4)]2 [Fe(C2O4)2] K2 (7) + [(C2O4)]2 [Fe(C2O4)3]3 K3 (8)3+ + (PO4)3 Ksp (9)nthesis process, H2C2O4 contains the ionization equi-ctions (4) and (5) in aqueous solution. With the gradualof H2C2O4 and the evaporation of distilled water, theoncentration of [C2O4]2 results in the occurrence of thection of reversible reactions from (6) to (8), which leadsase in the concentration of Fe3+ and the dissolution ofversible equation (9).expression of the nal concentration of [Fe(C2O4)3]3

e calculated based on the reversible reactions (4)(9):

]3} = Ka1Ka2K1K2K3Ksp[H2C2O4]03[H+]06 (I)102) and Ka2 (105) are the rst and second ioniza-nt of oxalic acid; K1 (109.4), K2 (106.8) and K3 (104)e stability constants of [Fe(C2O4)3]3; Ksp (1022) isty-product constant of FePO4; [H]0+ is the initial concen-+; and [H2C2O4]0 is the initial oxalic acid concentration.to (I), it is clearly showed that the concentration ofand [H+]0 is crucial to the formation of [Fe(C2O4)3]3,d be realized in our synthesis route with two meth-fcient mol quantity of H2C2O4 and the evaporation ofter.ed with the previous reported solgel methods [32,33],me advantages in our synthesis route. Themost impor-FePO42H2O powders are very cheap and simple to

parent sols because of the strong complexation abil-)2, which reduces the kinds of the reactants and theost. But in other solgel methods [12,33], the pH valuecarefully controlled in order to form clear sols, becauseinclined to form Fe(OH)3 or FePO4 precipitations in

and strong basic conditions and LiFePO4 could partlystrong acid. Also, the decomposition product of oxalicxture of CO, CO2 and H2O, with no contaminated gasesring calcination process. At last, the produced gasesain the particles from congregating, which would formell-distributed particles.

al characterization

he TG/DTA curve of the xerogel precursors, at a heatingmin1 from room temperature to 700 C in Ar atmo-TG curve presents three steps of weight loss and DTA

ays several corresponding exothermic peaks. Release ofabsorbed and crystallized water occurs below 160 C,

W. Peng et al. / Journal of Power Sources 196 (2011) 28412847 2843

Fig. 1. The TG/DTA curve for the precursor recorded from room temperature to700 C at a heating rate of 5 Cmin1 in Ar atmosphere.

Fig. 2. XRD pa(e) 700 C.

and there iThe main wcomplicatedand glucoseis a main exthe correspto 520 C m

Fig. 4. SEM image of LiFePO4/C material.

very small exothermic peaks appear in DTA curve. Above 520 C,there is nearly no weight loss in TG curve and no exothermic

in DTPO4.to osions poh.XRDpeaksof LiFe520 Cconverrial wafor 12

Thetterns of LiFePO4/C calcined at (a) 500, (b) 550, (c) 600, (d) 650 and

s a small exothermic peak in this temperature range.eight loss between 160 and 400 C can be ascribed to aprocess including the decomposition of the reactants, the iron-related redox reaction and so on. So thereothermic peak and several small exothermic peaks inonding DTA curve. The nal small weight loss from 400ay correspond to the crystallization of phosphate, and

to 700 C apeaks of thaccordanceolivine struare foundedthe crystal520 C analsized at 600nal calcinaon theXRDthe cell paring a highlyb=6.010 A,10%, the Riewhen the teimpurity phdiffractiondecomposit

Fig. 3. Rietveld renement of LiFePO4/C synthesA curve, which indicates the complete crystallizationTherefore, it is possible to calcine the precursor abovebtain well-crystallized LiFePO4. In this study, thermaland subsequent crystalline growth of LiFePO4/C mate-st-treated by heating at 500, 550, 600, 650 and 700 C

patterns of LiFePO4/C materials synthesized from 500re shown in Fig. 2. On one hand, the main diffractione LiFePO4/C samples from 550 to 650 C are all in goodwith the standard LiFePO4 crystal (JCPDS 81-1173) cture indexed by orthorhombic Pnmb. Few differencesin XRD response among these samples which suggests

growth of LiFePO4 can be achieved at 550 C (as low asyzed in TG/DTA curve). But the diffraction peaks synthe-

C are the highest and sharpest, so we choose it as thetion temperature. Andwe performRietveld renementpattern (Fig. 3) synthesizedat this temperature toobtainameters (a=10.333 A, b=6.011 A, c=4.698 A), indicat-crystalline LiFePO4 phase (JCPDS 81-1173, a=10.330 A,c=4.692 A). Because the Rwp and Rp values are less thantveld renement results are reliable. On the other hand,mperature is lower than 500 C or higher than 700 C,ases such as Li3PO4 [6] and Fe2P [34] appear. No typicalpeaks of carbon are found, so carbon yielded from theion of glucose should exist in amorphous form.ized at 600 C.


material.

Fig. 6. In

Fig. 4 shcomposite.observed. Timage (Fig.uniformly cness. The caanalyzer.

3.2. Galvan

The initishown in Fat room teare 166.9 acapacity (10.064V, whrms an exdensity inccharge capa(Fig. 7), whperformanc[25].

3.3. Cyclic c

Fig. 8 dat 0.1C ratFig. 5. TEM images of LiFePO4/Citial chargedischarge curves of LiFePO4/C material at 0.1C rate.

ows the SEM image of the as-synthesized LiFePO4/CWell-distributed submicrometer-size particles arehe particle size ranges from 100 to 500nm. The TEM5) indicates that the inner LiFePO4 material (black) isoated with a carbon layer (grey), about 2.6nm in thick-rboncontent is about5.9wt%, revealedby theelemental

ostatic charge/discharge measurements

al charge/discharge curves of the LiFePO4/C sample areig. 6, at 0.1C rate in the voltage range of 2.54.2Vmperature. The rst charge and discharge capacitiesnd 160.5mAhg1, which is close to the theoretical70mAhg1). The plateau potential difference is aboutich accords well with the previous paper [35] and con-cellent electrochemical reversibility. When the currentreases to 1, 2, 3, 5 and 10C rates, the initial dis-cities are about 150, 133.7, 128.1, 118.3, 106mAhg1

ich indicates good high-rate performances. The ratees are a little superior to the reported sol gel method

harge/discharge measurements

isplays the cyclic performances of LiFePO4/C samplee. After 50 cycles, the discharge capacity maintains

Fig. 7. F

158.2mAhgood cyclicat 0.110Care 99.1%, 9recoveringcapacities dwhich indicirst discharge curves of LiFePO4/C at different current densities.

g1 with a capacity retention of 98.7%, which displaysstability. And the cyclic curves in every rst 20 cyclesrates are displayed in Fig. 9. The capacity retentions8.8%, 99.6%, 99.4%, 99.7% and 99.2%, respectively.Whenthe former testing current densities, the dischargeecrease by no more than 2mAhg1 in all situations,ates good cyclic reversibility.

Fig. 8. Cyclic curve of LiFePO4/C material at 0.1C rate.


Fig. 9. Cyclic performances of LiFePO4/C at different current densities.

Table 1Anodic peak potential locations (Ep,a) and corresponding cathodic ones (Ep,c) andpotential differences (E) for the CV curve in Fig. 10.

Cycle Ep,a, V Ep,c, V E, V

First 3.596 3.340 0.256Second 3.542 3.348 0.194Third 3.524 3.356 0.168

3.4. CV measurements

The CV care shownrate of 0.1mcorrespondthe bulk. Tpotential beelectrochempeak curren

Fig. 10. Cyclic voltammograms of LiFePO4/C at the rst three cycles at a scan rateof 0.1mVs1.

TheCVcurves atdifferent scan rates0.1, 0.2, 0.5, 1 and2mVs1

are also studied in this paper, shown in Fig. 11. The peak currentdensity signicantly increases with the scan rate increasing. Theanodic peaks shift to higher potentials and the cathodic ones tolowerpotentials,which indicates increasedkineticpolarizationandincreased internal resistance [36]. And it is found that the redoxpeak current density is in direct ratio to 1/2 (Fig. 12), so the nalapparent lithium ion diffusivity could be obtained according to the

tional computing formula [37]:

4463

(II)transl convity,m2 sareurves of LiFePO4/C sample during the rst three cyclesin Fig. 10, in the potential range of 2.54.2V at a scanV s1. There is a pair of redox peaks during each circle,ing to the extraction/insertion of lithium ions from/intohe difference between oxidation and reduction peakcomes smaller during cycling (Table 1), indicating goodical reversibility. And the high oxidation/reductiont indicates fast lithium-ion diffusion.

conven

Ip = 0.

Amongis thethe modiffusi1014 cresultsFig. 11. CV curves of LiFePO4/C at different s 103F3/2n3/2ADLi+1/2C1/2(CR)1/2 (II)

, Ip is the redox peak current, F is Faraday content, nition number of electrons, A is the contact area, C iscentration of Li+, DLi+ is the nal apparent lithium ion is the scan rate. The obtained DLi+ is at an order of1 for both charging and discharging electrodes. The4 orders of magnitude as fast as the pure LiFePO4can rates.


Fig. 13. The Nplateau.

material (vious reporconstants-2charging LiF

3.5. EIS me

EIS is a vcal resistanctrolyte/elecsion resistaLiFePO4/C mThe curve isinclined linresponds torelated to tFig. 12. Variation of redox peak current to scan rate 1/2

yquist plot of LiFePO4/C tested at the rst discharging potential

1.81018 cm2 s1) and are consistent with the pre-t of Yu et al. [35], who obtained apparent Li+ diffusion.21014 and 1.41014 cm2 s1 for charging and dis-ePO4 electrodes.

asurements

ery important method to investigate the electrochemi-es, suchas the solidelectrolyte interface (SEI)lm, elec-trode interface, charge transfer and lithium-ion diffu-nces. Fig. 13 shows theNyquist plot of theas synthesizedaterial during the rst discharging potential plateau.comprised of one semicircle in high frequency and an

e in low frequency. The high-frequency semicircle cor-the charge-transfer resistance and the inclined line is

he diffusion resistance of lithium ion in the bulk. After

tting theresistancesing fast eleThe resultsreported bynique [10],loweredeleticles whichconductive

4. Conclus

LiFePO4solgel mephosphorusH2C2O4 wawas able tcalcinationvent the pahelpful toand SEM dwell-distribLiFePO4 maabout 2.6nobtained L118 and 1tively, in thwere good-with a capatrochemicaconductivitcoated subm

Acknowled

This woprogram (2for LiFePO4/C material.

experimental data, the charge-transfer and Warburgare as low as 39.05 and 4.79, respectively, indicat-ctrochemical reaction and lithium diffusion processes.are very similar to ferric citrate based solgel methodDupre et al. [38], but much lower than solid state tech-co-precipitation [39] or hydrothermalmethod [40]. Thectrochemical resistances areattributed to the small par-results in short lithium-ion diffusion distance and the

carbon layer which results in fast electron transfer rate.

ions

/C cathode material was synthesized with a novel

thod-cheap FePO42H2O was chosen as both iron andsources which could reduce the synthesis cost; cheaps chosen as both reductant and complexant whicho form transparent and homogeneous sols; in theprocess, the produced CO and CO2 gases could pre-rticles from aggregating and growing up which wassynthesize small and well-distributed particles. XRDemonstrated well-crystallized LiFePO4 material anduted submicrometer-size particles. TEM showed thatterial was uniformly coated with a carbon layer, withm in thickness. The initial discharge capacity of theiFePO4 material was as high as 160, 150, 134, 128,06mAhg1 at 0.1, 1, 2, 3, 5 and 10C rates, respec-e potential range of 2.54.2V. The cyclic performancesonly 2.4mAhg1 decreased after 50 cycles at 0.1C rate,city retention of 98.7%. The improvement of the elec-l performances could be attributed to fast electronicy and lithium-ion diffusivity resulting from the carbon-icrometer-size particles.

gements

rk was supported by NSFC (20801059, 21073100), 973010CB631303) and TSTC (10JCYBJC08000).


References

[1] A.K. Padhi, K.S. Nanjundaswamy, J.B. Goodenough, J. Electrochem. Soc. 144(1997) 1188.

[2] Y. Hu, M.M. Doeff, R. Kostecki, R. Finones, J. Electrochem. Soc. 1518 (2004)A1279.

[3] F. Croce, A.D. Epifanio, J. Hassoun, A. Deptula, T. Olczac, B. Scrosati, Electrochem.Solid-State Lett. 5 (2002) A47.

[4] Y.H. Huang, J.B. Goodenough, Chem. Mater. 20 (2008) 7237.[5] Y.-S. Hu, Y.-G. Guo, R. Dominko, M. Gaberscek, J. Jamnik, J. Maier, Adv. Mater.

19 (2007) 1963.[6] P.S. Herle, B. Ellis, N. Coombs, L.F. Nazar, Nat. Mater. 3 (2004) 147.[7] M.R. Yang, W.H. Ke, J. Electrochem. Soc. 155 (2008) A729.[8] R. Amin, C.T. Lin, J.B. Peng, K. Weichert, T. Acarturk, U. Starke, J. Maier, Adv.

Funct. Mater. 19 (2009) 1697.[9] K.S. Park, K.T. Kang, S.B. Lee, G.Y. Kim, Y.J. Park, H.G. Kim, Mater. Res. Bull. 39

(2004) 1803.[10] H. Liu, C. Li, H.P. Zhang, L.J. Fu, Y.P. Wu, H.Q. Wu, J. Power Sources 159 (2006)

717.[11] J. Barker, M.Y. Saidi, J.L. Sowyer, Electrochem. Solid-State Lett. 6 (2003) A53.[12] Y.Q. Hu, M.M. Doeff, R. Kostecki, R. Finonesa, J. Electrochem. Soc. 151 (2004)

A1279.[13] Y. Ding, Y. Jiang, F. Xu, J. Yin, H. Ren, Q. Zhuo, Z. Long, P. Zhang, Electrochem.

Commun. 12 (2010) 10.[14] K.S. Park, J.T. Son,H.T. Chung, S.J. Kim,C.H. Lee,H.G.Kim, Electrochem.Commun.

5 (2003) 839.[15] J.F. Qian, M. Zhou, Y.L. Cao, X.P. Ai, H.X. Yang, J. Phys. Chem. C 114 (2010) 3477.[16] Y.H. Huang, K.S. Park, J.B. Goodenough, J. Electrochem. Soc. 153 (2006) A2282.[17] D. Rangappa, K. Sone, T. Kudo, I. Honma, J. Powder Sources 195 (2010) 6167.[18] T.-H. Cho, H.-T. Chung, J. Power Sources 133 (2004) 272.[19] I. Belharouak, C. Johnson, K. Amine, Electrochem. Commun. 7 (2005) 983.

[20] K. Konstantinov, S. Bewlay, G.X.Wang, M. Lindsay, J.Z. Wang, Electrochim. Acta50 (2004) 421.

[21] V. Palomares, I.R. de Larramendi, J. Alonso, M. Bengoechea, A. Goni, O. Miguel,T. Rojo, Appl. Surf. Sci. 256 (2010) 2563.

[22] D. Choi, P.N. Kumta, J. Power Sources 163 (2007) 1064.[23] S.B. Lee, S.H. Cho, S.J. Cho, G.J. Park, S.H. Park, Y.S. Lee, Electrochem. Commun.

10 (2008) 1219.[24] Y.Y. Liu, C.B. Cao, J. Li, Electrochim. Acta 55 (2010) 3921.[25] S. Beninati, L. Damen, M. Mastragostino, J. Power Sources 194 (2009) 1094.[26] C. Arbizzani, S. Beninati, M. Mastragostino, J. Appl. Electrochem. 40 (2010) 7.[27] B. Kang, G. Ceder1, Nature 458 (2009) 190.[28] Y.Q. Wang, J.L. Wang, J. Yang, Y. Nuli, Adv. Funct. Mater. 16 (2006) 2135.[29] Y.H. Huang, H.B. Ren, S.Y. Yin, Y.H.Wang, Z.H. Peng, Y.H. Zhou, J. Power Sources

195 (2010) 610.[30] J.C. Zheng, X.H. Li, Z.X. Wang, H.J. Guo, S.Y. Zhou, J. Power Sources 184 (2008)

574.[31] N.N. Sinha, N. Munichandraiah, J. Electrochem. Soc. 157 (7) (2010) A824.[32] D. Choi, P.N. Kumt, J. Power Sources 163 (2007) 1064.[33] Z.H. Xu, L. Xu, Q.Y. Lai, X.Y. Ji, Mater. Res. Bull. 42 (2007) 883.[34] S. Franger, F. Cras, C. Bourbon,H.Rouault, Electrochem.Solid-State Lett. 5 (2002)

231.[35] D.Y.W. Yu, C. Fietzek,W.Weydanz, K. Donoue, T. Inoue,H. Kurokawa, S. Fujitani,

J. Electrochem. Soc. 154 (4) (2007) A253.[36] K.-L. Lee, J.-Y. Jung, S.-W. Lee,H.-S.Moon, J.-W.Park, J. PowerSources130 (2004)

241.[37] A.J. Bard, L.R. Faulkner, Electrochemical Methods, John Wiley & Sons Inc., New

York, 1980, p. 213.[38] N.Dupre, J.-F.Martin, J. Degryse, V. Fernandez, P. Soudan,D.Guyomard, J. Power

Sources 195 (2010) 7415.[39] Y.Y. Liu, C.B. Cao, Electrochim. Acta 55 (2010) 4694.[40] J.L. Liu, R.R. Jiang, X.Y.Wang, T. Huang, A.S. Yu, J. Power Sources 194 (2009) 536.

A novel solgel method based on FePO42H2O to synthesize submicrometer structured LiFePO4/C cathode materialIntroductionExperimentalPreparation of LiFePO4/CCharacterization of LiFePO4Cell assemblyElectrochemical tests

Results and discussionMaterial characterizationGalvanostatic charge/discharge measurementsCyclic charge/discharge measurementsCV measurementsEIS measurements

ConclusionsAcknowledgementsReferences

Documents

LiFeP 2011