Journal of Solid State Chemistry 196 (2012) 326–331

Contents lists available at SciVerse ScienceDirect

Journal of Solid State Chemistry

0022-45

http://d

n Corr

PINSTECnn Als

scopy, T

of Adva

Materia

Fax: þ8

E-m

jzhu@m

journal homepage: www.elsevier.com/locate/jssc

SnO2/ZnO composite structure for the lithium-ion battery electrode

Mashkoor Ahmad a,c,n, Shi Yingying b, Hongyu Sun a, Wanci Shen b, Jing Zhu a,nn

a Beijing National Center for Electron Microscopy, The State Key Laboratory of New Ceramics and Fine Processing, Laboratory of Advanced Material, China Iron & Steel Research

Institute Group, Department of Material Science and Engineering, Tsinghua University, Beijing 100084, Chinab Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, Chinac Nanomaterial Research Group, Physics Division, PINSTECH, P.O. Nilore, Islamabad, Pakistan

a r t i c l e i n f o

Article history:

Received 29 March 2012

Received in revised form

5 June 2012

Accepted 24 June 2012Available online 30 June 2012

Keywords:

SnO2/ZnO composite

Hydrothermal

Lithium storage

96/$ - see front matter & 2012 Elsevier Inc. A

x.doi.org/10.1016/j.jssc.2012.06.032

esponding author at: Nanomaterial Resear

H, P.O. Nilore, Islamabad, Pakistan. Fax: þ92

o corresponding author at: Beijing National

he state key Laboratory of New Ceramics and

nced Material, China Iron & Steel Research In

l Science and Engineering, Tsinghua Univer

6 62771160.

ail addresses: mashkoorahmad2003@yahoo.co

ail.tsinghua.edu.cn (J. Zhu).

a b s t r a c t

In this article, SnO2/ZnO composite structures have been synthesized by two steps hydrothermal

method and investigated their lithium storage capacity as compared with pure ZnO. It has been found

that these composite structures combining the large specific surface area, stability and catalytic activity

of SnO2 micro-crystals, demonstrate the higher initial discharge capacity of 1540 mA h g�1 with a

Coulombic efficiency of 68% at a rate of 120 mA h g�1 between 0.02 and 2 V and found much better

than that of any previously reported ZnO based composite anodes. In addition, a significantly enhanced

cycling performance, i.e., a reversible capacity of 497 mA h g�1 is retained after 40 cycles. The improved

lithium storage capacity and cycle life is attributed to the addition of SnO2 structure, which act as good

electronic conductors and better accommodation of the large volume change during lithiation/

delithiation process.

& 2012 Elsevier Inc. All rights reserved.

1. Introduction

Rechargeable lithium-ion batteries (LIBs) are promising powersources for a wide range of applications, such as portableelectronic devices, electric vehicles and implantable medicaldevices because of their high energy level, long cycle life andlow environment impact etc. Due to increasing demand for highenergy density LIBs, a lot of research efforts are conducted toexplore new materials and reaction mechanisms as an alternativeto graphite as anode material [1–3]. Li-alloys based on alloyingde-alloying reaction of elements Sn, Si, Sb and Al are wellinvestigated as anode materials because of their large Li-storagecapacities [4–6]. Among these Sn is considered as the mostpromising element because of its much higher theoretical capa-city (991 mA h g�1) than graphite 372 mA h g�1 and it formsalloys with Li up to Li17Sn4. Sn-based intermetallics, oxides, andcomposites are also well studied as possible alternatives tographite anode presently employed in the LIBs.

ll rights reserved.

ch Group, Physics Division,

51 9248808.

Center for Electron Micro-

Fine Processing, Laboratory

stitute Group, Department of

sity, Beijing 100084, China.

m (M. Ahmad),

Recently, Sn-based binary and ternary oxides such as SnO [7],SnO2 [8,9], CaO SnO2 [10], CoSnO3 [11] have also been investi-gated as anode materials due to their crystallinity, particle size,and morphological features. Among all Sn-–based oxides, SnO2 isone of the attractive alternative anode materials for LIBs becauseof its high specific capacity relative to graphite [12,13]. However,its application is still hindered by poor cyclability originatingfrom the large volume change during Li–Sn alloying/dealloyingcycle [14–16]. Therefore, researchers have made many efforts toovercome these limitations and improve the performance such as(i) increase the specific surface area by preparing nanomaterialswith various morphology and dimensions (ii) addition of one ormore electrochemically active counter atoms/ions (iii) properchoice of the starting crystal structure (iv) restricting the voltagerange of cycling vs. Li and (v) developing composite structures[17–23].

As there is already evidence that composite structures repre-sent a significant role in the electrochemical properties of anodematerial. In terms of integration of the above possible improvingroutes, in our approach we synthesized SnO2/ZnO compositestructure by employing two steps hydrothermal method andinvestigated their electrochemical performances. It has beenreported that ZnO follows the same mechanism as that of tinoxide and the composite structure of both oxides induces an extrainitial charge capacity in LIBs [24]. Both oxides exhibit differentelectrochemical performances and complicated reaction mechan-isms with Li ion. For example, the reversible reaction of SnO withLi ion is proposed to be the classical alloying and dealloying

M. Ahmad et al. / Journal of Solid State Chemistry 196 (2012) 326–331 327

processes [25] whereas the reaction mechanism of Li ion withZnO involves the formation and decomposition of Li2O accom-panying the reduction and oxidation of metal nanoparticles [26].Recently, Liu et al. synthesized SnO2/carbon composites andreported improved reverse-capacity and Li-cyclability to someextent [27]. Reddy et al. synthesized rutile structure of vanadiumantimony tin oxide and found that the presence of vanadiumoxide (VOx) in the composite can act as a good matrix and helpsin suppressing the capacity fading of Sb and tin oxide upon longterm cycling [28]. Mohd et al. reported carbon coated SnO2/NiOnanocomposite with high discharge capacity and cycling perfor-mance [29]. Lee et al. prepared Si-coated SnO2 nanotubes andshowed that such structures demonstrate much better ratecapability than either SnO2 nanotubes [30]. Chen et al. synthe-sized SnO2 hollow nanospherse and rattle-type hollow structuresof a-Fe2O3@SnO2 and investigated the electrochemical lithiumstorage properties. They found that a-Fe2O3@SnO2 nanorattlesmanifest a much lower initial irreversible loss and higher rever-sible capacity compared to SnO2 hollow spheres [31]. Changa etal. prepared SnS2/SnO2 composites by the microwave assistedmethod using SnCl4 �2 H2O and L-cysteine as starting materials.The electrochemical performance demonstrates that SnS2/SnO2

composites with layered structure exhibited high reversiblecapacity and good cycling performances [32]. To the best of ourknowledge, up till now there have been no reports on theSnO2/ZnO unique system which combine the advantages ofSnO2 and ZnO in LIB anode. Our results demonstrate thatSnO2/ZnO composite structure exhibit an excellent improvementin lithium storage capacity as compared with pure ZnO synthesizedwith the same experimental conditions.

Fig. 1. XRD pattern of pure ZnO and SnO2/ZnO composite samples.

2. Experimental section

The synthesis of SnO2/ZnO composite structure on the Znsubstrate is carried out in two steps.

2.1. Synthesis of ZnO nanowires

In the first step, the ZnO nanowire arrays are grown on the Znsubstrate via the hydrothermal method. In a typical procedure,10 mL NaOH (2 M) and 5 mL 30% H2O2 are first mixed and stirredbefore the solution being transferred to a 20 mL stainless steelTeflon-lined autoclave. A piece of zinc foil with dimension(3 cm�5 cm) is then added to the above solution before theautoclave is sealed. The autoclave is then maintained at 180 1C for12 h before being cooled down to room temperature. The zinc foilis taken out from the solution and rinsed with distilled water andethanol, followed by air-drying for 2 h.

2.2. Synthesis of SnO2/ZnO composite structure

In the second step, 0.22 g of SnCl4 5H2O, 5 mL of ethanol, and5 mL of distilled water are mixed and stirred. The pH value ofabove solution is adjusted to 12 by adding 2 M NaOH drop bydrop. The above solution is then transferred into the 20 mLstainless steel Teflon-lined autoclave, and the product from thefirst-step-synthesis (a piece of Zn substrate with ZnO nanowiresarray) is added into the autoclave before sealing. The reactor ismaintained at 150 1C for 24 h before being cooled down to roomtemperature. After that, the zinc foil is taken out from thesolution and rinsed with distilled water and ethanol and air-dried. The product in the composite (arrays of ZnO NWs alongwith SnO2 microcrystals) about 1 g was obtained after scratchingthe Zinc foil.

2.3. Apparatus

Both products are examined by scanning electron microscopy(SEM FE6301), X-ray diffraction (XRD), X-ray photospectroscopy(XPS) and transmission electron microscopy TEM (JEM-2011).Electrochemical tests were performed using CR2032 coin cellsassembled in an argon-filled glove box. The working electrodecomposed of 80 wt% active material (SnO2/ZnO composite andpure ZnO NWs), 10 wt% poly(vinylidene fluoride) (PVDF), and10 wt% carbon black was fabricated by casting a slurry onto acopper file. The electrolyte was 1 M LiPF6 dissolved in a 1:1(volume ratio) mixture of ethylene carbonate (EC) and diethylcarbonate (DMC). A lithium metal foil was used as the counterelectrode. A glass fiber was used as a separator. For the compara-tive study, CR2032 coin cell was also assembled using the pureZnO structure as the working electrode.

3. Results and discussions

3.1. Morphology and structure characterization

The structures of the as-prepared products are characterizedusing XRD. Fig. 1 shows the XRD pattern of the ZnO sample inwhich all the peaks can be well assigned to those of wurtzite(hexagonal) ZnO with lattice constants of a¼3.25 A1 andc¼5.21 A1 (JCPDS: 36-1451). The existence of Zn peaks in thepattern is due to the Zn substrate. X-ray diffraction taken fromSnO2/ZnO sample suggests the existence of another material thanZnO, i.e., SnO2 with orthorhombic structure (JCPDS: 78 1063).

Fig. 2(a) presents a low-magnification SEM image of pure ZnOsample and shows that the synthesized product mainly consistsof oriented arrays of NWs distributed on the Zn substrate. Thelengths of the NWs are in tens of micrometers, while theirdiameters vary within 100–200 nm. The morphology of theSnCl4 solution treated ZnO sample consists of ZnO NWs alongwith the addition of SnO2 micro-crystals as shown in Fig. 2(b). Aclose view of magnified SEM image of SnO2/ZnO compositestructure is shown in the inset and reveals that NWs maintainthe morphology after the addition of SnO2 structure. It can beclearly seen that some NWs are buried in the SnO2 structurewith the tip of NW being exposed. The surface of theSnO2/ZnO composite appears to be rough as compared to thatof the as-grown ZnO NWs. Fig. 2(c) and (d) is the EDS spectrumof pure SnO2/ZnO composite. In comparison with ZnO, thespectrum taken from the SnO2 capped portion suggests the

Fig. 2. FESEM images of (a) pure ZnO NWs (b) SnCl4 treated ZnO sample (c, d) EDS spectra of pure SnO2/ZnO composite samples; inset is the SEM image of single SnO2

micro-crystal wrapping the ZnO NW at lower position.

Fig. 3. Low magnification TEM images showing (a) single ZnO NW along with SnO2 micro-crystal with the ZnO tip buried inside the SnO2, (b) SnO2 micro-crystal wrapping

the ZnO NW at lower positions with the NW tip exposed, and HRTEM images taken from the (c) interface part of two materials (d) SnO2 micro-crystal.

M. Ahmad et al. / Journal of Solid State Chemistry 196 (2012) 326–331328

existence of mainly Sn and O together with a small percentage ofZn. The quantitative analysis reveals that the average amounts ofSn and Zn in the composite are 32% and 46% respectively. The low

magnification TEM image of a single SnO2/ZnO compositestructure is shown in Fig. 3(a). It can be seen that mostly SnO2

structure forms cap on the tip of the ZnO NW. The TEM

M. Ahmad et al. / Journal of Solid State Chemistry 196 (2012) 326–331 329

observation of some of the SnO2 micro-crystals wrapping the ZnONW at slightly lower position below the tip of the NW is shown inFig. 3(b). The wire-like contrast in the center part of the SnO2

structure can be seen, indicating that the SnO2 wraps the NW,leaving the tip being exposed. Fig. 3(c) is the HRTEM image takenfrom the interface part of the SnO2/ZnO composite and clearlydisplays the ZnO and SnO2 structure of different contrasts. BothSnO2 and ZnO are found to be single crystals as also suggested bythe electron diffraction pattern (SAED) taken from the wire andcap portions. Fig. 3(d) shows the magnified HRTEM image of aSnO2 structure in the composite. The corresponding SAED of theSnO2 shown in the inset reveals the single crystal nature of themicro-crystal.

The oxidation state of the Sn on ZnO structure is determinedby XPS analysis. The high resolution XPS spectra of Sn3d and Zn3pare shown in Fig. 4(a) and (b) respectively. The spectrum inFig. 4(a) shows two significant binding energy peaks at 486.73and 495.5 eV corresponding to the electronic states of Sn3d5/2 andSn3d3/2 respectively. These values suggest unambiguously thatSnO2 micro-crystals remain as a rutile structure. On the otherhand, two peaks at 1020.91 and 1043.94 eV corresponding toZn2p3/2 and Zn2p1/2 respectively are shown in Fig. 4(b). Theenergy difference between these two peaks is 23.03 eV, whichagrees well with the standard value of 22.97 eV. Therefore, XPSanalysis again confirms the successful addition of SnO2 micro-crystals in the composite structure.

Fig. 4. XPS spectra corresponding to Sn3d and Zn3p peaks.

3.2. Electrochemical applications

The electrochemical performance of the SnO2/ZnO compositestructure as an anode material for lithium-ion battery is investi-gated. Cyclic voltammetry (CV) is commonly used to establish thereversibility of electrode material vs. Li and to evaluate thepotential at which the discharge–charge reactions take place.Fig. 5(a) shows the CV curves of SnO2/ZnO composite electrode forthe first 5 cycles at a scan rate of 0.5 mV s�1 in the potential rangeof 0.02–2 V and presents similar electrochemical reaction asdiscussed in the literature [33]. During the first cathodic (lithiuminsertion) scan, the composite electrode shows a well resolvedintense peak at 0.8 V and on further insertion of lithium a broadpeak is observed at a low voltage of �0.61 V. The first peakcorresponds to the structure destruction and generation ofamorphous Li2O matrix. The second peak can be assigned to thereduction of SnO2 into Sn and the formation of LixSn alloys.During the first anodic scan (lithium deintercalation), peaksaround �0.75 V and �1.4 V are clearly seen, which correspondsto multistep de-alloying reaction. In subsequent cycles, thecathodic scan is similar to the first while anodic peaks slightlyshifted towards lower potential, which indicates that the de-alloying reaction occurs at lower potential due to nano-sizeeffect. In the subsequent cycles, the CV curves exhibit almost nochange in the peak shape, suggesting high reversibility ofthe SnO2/ZnO composite electrode. The addition of SnO2

micro-crystals clearly enhances the reaction rate upon the rever-sible conversion reaction between ZnOþ2Liþþ2e�2ZnþLi2O,ZnþLiþþe�2LiZn [26] and SnO2þ4Liþþ4e�12Snþ2Li2O,SnþxLiþþxe�2LixSn (0r �r 4.4) [34] as evident by theincreased anodic peaks current (at 0.76 V) with cycling becausemore materials are activated to react with lithium in each scan.Thus CV behavior of SnO2/ZnO composite structure confirms thatthis is an electrochemically active material for lithium storage.Variation of CV curves of SnO2/ZnO electrode with scan rates of0.3 and 0.1 mVs�1 is also performed as shown in Fig. S1. It isobserved that at low scan rate the peaks are well resolved. As thescan rate increased the height of the peaks current varies and ashift in the peaks towards higher potential are observed duringoxidation.

The capacity–voltage profiles of SnO2/ZnO composite structureas compared with pure ZnO NWs electrodes are evaluated bygalvanostatic charge–discharge measurements in the voltagerange of 2–0.02 V at a current density of 120 mAg�1. Fig. 5(band c) summarizes the discharge–charge capacity data for boththe electrodes. Fig. 5(b) shows the voltage profiles of the SnO2/ZnO composite electrode which start from �2.5 V, drops rapidly,reaches a plateau at �0.6 V during the first discharge and thenfollowed by slop down to 0.01 V. The voltage plateaus at �0.6 Vand �0.42 V may correspond to the structure destruction of SnO2

and the formation of Sn metal, while the plateau at �0.021 Vcorresponds to the alloy formation Li4.4 Sn. It can be found thatthe SnO2/ZnO electrode exhibits a very high initial dischargecapacity of about �1540 mA h g�1 with a Coulombic efficiencyof 68%. During the first charge cycle, a broad voltage plateau at�1.1 V is observed which can be considered to be due to the de-alloying reaction of Li4.4 Sn. The first charge capacity of thecomposite is �620 mA h g�1. The charge profiles for the 10 cyclesare similar, establishing the same reaction mechanism i.e. de-alloying of Li4.4 Sn formed during the discharge reaction. To thebest of our knowledge, this discharge–charge capacity values arefound to be much higher than the values recently reported byother groups as shown in Table1 [36–40]. Such a superiorreversible capacity can be attributed to the synergistic effectbetween the SnO2 micro-crystals and ZnO NWs. In comparison,the initial discharge capacity of ZnO electrode is 1080 mAhg�1

Fig. 5. (a) Cyclic voltammogram of SnO2/ZnO electrode at a scan rate of 0.5 mV s�1; Galvanostatic charge–discharge curves of (b) SnO2/ZnO electrode after 1, 2, 5 and

7 cycles (c) ZnO electrode after 1, 2, 5, 7 and 9 cycles in the voltage range of 0.02–2.0 V (vs. Li) at a current density of 120 mA g�1 and (d) plot of capacity and Coulombic

efficiency of the cell vs cycle number for the SnO2/ZnO and ZnO electrode, which is shown as a comparison to display the improvement when using the SnO2/ZnO

electrode.

M. Ahmad et al. / Journal of Solid State Chemistry 196 (2012) 326–331330

as shown in Fig. 5(c). The initial Coulombic efficiency is 47%(not shown here), which is 21% lower than that of the SnO2/ZnOelectrode. Because the first step reaction of ZnO with Liþ invol-ving the formation of Li2O is irreversible, the Coulombic efficiencyis low for ZnO [26]. When the ZnO is functioned with SnO2, Snfacilitates Li2O decomposition. The decomposition of Li2O pro-duced in the first step will be more complete as there is enoughactive Sn as a catalyst for the reverse reaction. The significantimproved lithium storage capacity of the SnO2/ZnO structure cellresults from the Li activity of Sn–ZnO phase. Recently, it has beenreported that SnO2 significantly enhanced the reversible capa-cities of metal oxide anode due to the catalytic effects of the Sn onthe reaction Li2OþM-MOþLiþ [35]. We believe this superiorlithium storage capacity is largely associated with the compositestructure of SnO2/ZnO because Sn can alloy with a very highpercentage of Li (Li4.4Sn). The initial irreversible capacity lossshould mainly originate from the reduction in the electrolyteresulting in the formation of a solid electrolyte interface (SEI) onthe surface of the active material and/or irreversible lithiuminsertion into the host materials.

The comparison of the cycling performance of SnO2/ZnO and ZnOcells at a current density of 120 mA h g�1 is shown in Fig. 5(d). Itcan be seen that the charge capacity of the SnO2/ZnO cell decreasesto 813 mA h g�1 after second cycle and 600 mA h g�1 after seventhcycle. The degradation is slower in subsequent cycles and a stablecapacity of 505 mA h g�1 reaches after 10 cycles. A stable reversiblecapacity of 497 mA h g�1 is obtained after the cell is cycled for 40cycles which is still much higher than the theoretical capacity ofgraphite. In contrast, the capacity of the ZnO electrode decaysrapidly to 312 mA h g�1 after 10 cycles between 2 and 0.02 V asshown in Fig. 5(d). The improved capacity and cycle life of the SnO2/ZnO electrode can be attributed to the SnO2 structure, which acts asa good electronic conductor and better accommodation of the largevolume change during lithiation/delithiation process. The SnO2

micro-crystals facilitate the diffusion of lithium ions and providegreater accessibility to the active sites for subsequent alloy anddealloy processes.

The morphological changes on both the structures are alsomonitored by recording SEM and TEM images after 40 cyclesof cells operation. It can be seen that even after 40 cycles, the

Table 1Performance comparisons of some Li-ion battery electrodes constructed based on different ZnO nanostructure materials.

Electrode materials 1 cycle charge–discharge

Capacity (mA h g�1)

Current density

(mA g�1)

Applied potential

range (V)

Ref.

Ni-coated ZnO powder 1132–560 80 0 02–3.0 [36]

Mg-doped ZnO thin film 1210–560 120 0.05–2.5 [37]

ZnO/ZnAl2O4 porous film 1275–590 200 0.05–2.5 [38]

Au–ZnO flowers 1280–660 120 0.02–3.0 [40]

C–ZnO nanorods arrays 1150–640 – 0.05–2.5 [39]

SnO2/ZnO composite 1540–620 120 0.02–2.0 Present work

M. Ahmad et al. / Journal of Solid State Chemistry 196 (2012) 326–331 331

SnO2/ZnO composite structure preserve the morphology as shownin Fig. S2. However the pure ZnO structure can only maintainmorphology for less than 15 cycles. The preservation of SnO2/ZnOstructure during the Liþ insertion/extraction process helps tokeep the strong electrical interaction between SnO2 and ZnOwhich results in a better cycling stability. Thus it is concluded thatboth structures SnO2 and ZnO mutually help each other to bufferthe unit cell volume variations and help in better Li cycling.

4. Conclusions

In summary, SnO2/ZnO composite structure has been success-fully synthesized by two steps hydrothermal method. It has beenfound that SnO2/ZnO composite structure is a promising anodematerial for rechargeable lithium-ion battery, as it exhibits asuperior lithium storage capacity, good cycling performance andhigh Coulombic efficiency. The improved performance is ascribedto the addition of SnO2 structure, which acts as a good electronicconductor and better accommodation of the large volume changeduring lithiation/delithiation process. Our findings open thepossibility of producing efficient anode materials with a highreversible capacity for lithium ion battery. We suggest that thismethod can be extended to synthesize metal oxide compositestructures to explore more applications.

Acknowledgment

This work is financially supported by National 973 Project ofChina and Chinese National Nature Science Foundation. This workmade use of the resources of the Beijing National Center forElectron Microscopy. The authors are also grateful to HigherEducation Commission of Pakistan (HEC) for the financial supportto Mashkoor Ahmad.

Appendix A. Supporting information

Supplementary data associated with this article can be foundin the online version at http://dx.doi.org/10.1016/j.jssc.2012.06.032.

References

[1] B. Das, M.V. Reddy, G.V. Subba Rao, B.V.R. Chowdari, J Solid State Electro-chem. 15 (2011) 259.

[2] M.-S. Park, G.-X. Wang, Y.-M. Kang, D. Wexler, S.-X. Dou, H.-K. Liu, Angew.Chem. Int. Ed. 46 (2007) 750.

[3] X.W. Lou, Y. Wang, C. Yuan, J.Y. Lee, L.A. Archer, Adv. Mater. 18 (2006) 2325.[4] G.A. Nazri, G. Pistoia (Eds.), Kluwer Academic, New York, 2003.[5] M. Armand, J.-M. Tarascon, Nature 451 (2008) 652.[6] M.V. Reddy, G.V. Subba Rao, B.V.R., Chowdari, Chem. Rev., in press.[7] D. Aurbach, A. Nimberger, B. Markovsky, E. Levi, E. Sominski, A. Gedanken,

Chem. Mater. 14 (2002) 4155.[8] C. Kim, M. Noh, M. Choi, J. Cho, B. Park, Chem. Mater. 17 (2005) 3297.[9] M.-S. Park, Y.-M. Kang, G.-X. Wang, S.-X. Dou, H.-K. Liu, Adv. Funct. Mater. 18

(2008) 455.[10] Y. Sharma, N. Sharma, G.V. Subba Rao, B.V.R. Chowdari, Chem. Mater. 20

(2008) 6829.[11] F. Huang, Z. Yuan, H. Zhan, Y. Zhou, J. Sun, Mater. Lett. 57 (2003) 3341.[12] X. Yu, S. Yang, B. Zhang, D. Shao, X. Dong, Y. Fang, Z. Li, H. Wang, J. Mater.

Chem. 21 (2011) 12295.[13] P.G. Bruce, B. Scrosati, J.-M. Tarascon, Angew. Chem. Int. Ed. 47 (2008) 2930.[14] D. Larcher, S. Beattie, M. Morcrette, K. Edstroem, J.C. Jumas, J.M. Tarascon, J.

Mater. Chem. 17 (2007) 3759.[15] Y. Zhao, J. Li, Y. Ding, L. Guan, RSC Adv. 1 (2011) 852.[16] L. Noerochima, J.Z. Wang, S. Chou, H.J. Li, H.K. Liu, Electrochim. Acta 56 (2010)

314.[17] I.A. Courtney, J.R. Dahn, J. Electrochem. Soc. 144 (1997) 2045.[18] H. Li, X. Huang, L. Chen, Solid State Ionics 123 (1999) 189.[19] H. Uchiyama, E. Hosono, I. Honma, H. Zhou, H. Imai, Electrochem. Commun.

10 (2008) 52.[20] Z.P. Guo, G.D. Du, Y. Nuli, M.F. Hassan, H.K. Liu, J. Mater. Chem. 19 (2009)

3253.[21] B. Liu, Z.P. Guo, G.D. Du, et al., Electrochim. Acta 54 (2009) 5782.[22] X.W. Lou, J.S. Chen, P. Chen, L.A. Archer, Chem. Mater. 21 (2009) 2868.[23] Z. Chen, Y. Cao, J. Qian, X. Aia, H. Yang, J. Mater. Chem. 20 (2010) 7266.[24] F. Bellaiard, P.A. Connor, J.T.S. Irvine, Ionics 5 (1999) 450.[25] Y. Idota, T. Kubota, A. Matsufuji, Y. Maekawa, T. Miyasaka, Science 276 (1997)

1395.[26] Z.W. Fu, F. Huang, Y. Zhang, Y. Chu, Q.Z. Qin, J. Electrochem. Soc. 150 (2003)

A714.[27] J. Liu, W. Li, A. Manthiram, Chem. Commun. 46 (2010) 1437.[28] M.V. Reddy, G.V. Subba Rao, B.V.R. Chowdari in: B.V.R Chowdari et al. (eds.),

Solid State Ionics: New Materials for Pollution Free Energy Devices, Proceed-ings of the 11th Asian Conference on Solid State Ionics, MacMillan, India,New Delhi, 2008, pp. 187–193.

[29] M.F. Hassan, M.M. Rahman, Z. Guo, Z. Chen, H. Liu, J. Mater. Chem. 20 (2010)9707.

[30] W.J. Lee, M.-H. Park, Y. Wang, J.Y. Leed, J. Cho, Chem. Commun. 46 (2010)622.

[31] J.S. Chen, C.M. Li, W.W. Zhou, Q.Y. Yan, L.A. Archerc, X.W. Lou, Nanoscale 1(2009) 280.

[32] K. Changa, W.-X. Chen, H.L. Li, Electrochim. Acta 56 (2011) 2856.[33] J. Cai, Z. Li, S. Yao, H. Meng, P.K. Shen, Z. Wei, Electrochim. Acta (2012).[34] K. Chang, W.X. Chen, H. Li, H. Li, Electrochim. Acta 56 (2011) 2856.[35] K.T. Nam, D.W. Kim, P.J. Yoo, C.Y. Chiang, N. Meethong, P.T. Hammon,

Y.M. Chiang, A.M. Belcher, Science 312 (2006) 885.[36] C.Q. Zhang, J.P. Tu, Y.F. Yuan, X.H. Huang, X.T. Chen, F. Mao, J. Electrochem.

Soc. 154 (2007) A65.[37] G.F. Yan, H.S. Fang, G.S. Li, L.P. Li, H.J. Zhao, Y. Yang, Chin. J. Struct. Chem. 28

(2009) 409.[38] J. Liu, Y. Li, X. Huang, L.Z. Guangyun, Adv. Func. Mater. 18 (2008) 1448.[39] J. Liu, Y. Li, R. Ding, J. Jiang, Y. Hu, X. Ji, Q. Chi, Z. Zhu, X. Huang, J. Phys. Chem.

B 113 (2009) 5336.[40] M. Ahmad, S. Yingying, A. Nisar, H. Sun, W. Shen, M. Wei, J. Zhu, J. Mater.

Chem. 21 (2011) 7723.