-
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,
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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.
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2844 W. Peng et al. / Journal of Power Sources 196 (2011)
28412847
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.
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W. Peng et al. / Journal of Power Sources 196 (2011) 28412847
2845
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.
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2846 W. Peng et al. / Journal of Power Sources 196 (2011)
28412847
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).
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W. Peng et al. / Journal of Power Sources 196 (2011) 28412847
2847
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