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View Article OnlineView Journal | View Issue

Industrialization

aState Key Laboratory of Electroanalytical C

Modern Analytical Techniques, CAS C

Changchun, 130022, P. R. ChinabUniversity of Chinese Academy of Sciences,cSchool of Chemistry & Chemical Engineeri

ChinadDepartment of Chemistry, Hebei Norma

067000, P. R. China. E-mail: lniu@ciac.ac.c

† Electronic supplementary informa10.1039/c6ra22040a

Cite this: RSC Adv., 2016, 6, 97818

Received 2nd September 2016Accepted 29th September 2016

DOI: 10.1039/c6ra22040a

www.rsc.org/advances

97818 | RSC Adv., 2016, 6, 97818–9782

of tailoring spherical cathodematerial towards high-capacity, cycling-stable andsuperior low temperature performance for lithium-ion batteries†

Zhonghui Sun,ab Liansheng Jiao,abd Yingying Fan,ab Fenghua Li,ab Dandan Wang,ab

Dongxue Hanab and Li Niu*abc

Three different types of spherical cathodes (Li[Ni0.6Co0.2Mn0.2]O2) were synthesized via hydroxide

co-precipitation method coupled with high temperature lithiation process. The particle size,

nanostructure, specific surface area and pore distributions can be controlled as expected. X-ray

diffraction patterns revealed that the as-obtained cathode materials had a typical hexagonal a-NaFeO2

layered structure with a space group R�3m. The electrochemical measurements demonstrate that Li

[Ni0.6Co0.2Mn0.2]O2 with 3 mm-size in diameter exhibited higher initial coulombic efficiency (94.9%), rate

capacity (156 mA h g�1 at 900 mA g�1), and low-temperature property (157 mA h g�1 at 180 mA g�1, 0 �C)in comparison with the larger one (12 mm). Most impressively, an ultra-stable capacity of 156 mA h g�1 can

be retained at 180 mA g�1 even after 300 cycles at 0 �C. As is known, Li[Ni0.6Co0.2Mn0.2]O2 with 3 mm-size

has the best result among the reported Li[Ni0.6Co0.2Mn0.2]O2-based cathode materials. The excellent

electrochemical performance of the smaller size cathode results from the advantageous hierarchical

nanorods architecture, porous characteristics, and reduced ions/electrons transport path.

1. Introduction

Lithium-ion battery, by virtue of its higher operating voltage,higher energy efficiency, and longer cycle life, represents thestate-of-the-art technology among the rechargeable batteries,which has attracted considerable attention of researchers.1–10

The Ni-rich layered oxide cathode materials Li[NixCoyMn1�x�y]O2 (0 # x # 1, 0 # y # 1, LNCM) are promising candidates forhigh energy density battery applications in electric vehicles(EVs) or hybrid electric vehicles (HEVs) because of their highcapacity of about 200 mA h g�1.11–13 However, the currentcommercial LNCMs (e.g., Li[Ni0.6Co0.2Mn0.2]O2) are known tohave spherical morphologies with 10–15 mm diameter consist-ing of primary nanoparticles. Although these cathode materialscan provide a high energy density, properties of quick chargeand low temperature of the current lithium battery are severely

hemistry, c/o Engineering Laboratory for

enter for Excellence in Nanoscience,

Beijing, 100049, P. R. China

ng, Linyi University, Linyi 276005, P. R.

l University for Nationalities, Chengde

n; Fax: +86-431-526-2800

tion (ESI) available. See DOI:

4

hindered by the sluggish ions and electron diffusion kineticsproblems.14–17 To address these issues, great efforts have beenmade, including surface coating lithium ion conductiveoxide,18–20 anion/cation substitution,21,22 reducing particle size(micro/nano level) and constructing special particle morphol-ogies.23–27 Among these approaches, nanostructured cathodeshave been intensively investigated, and they indeed exhibitexcellent electrochemical performances in half cell tests. Itappears that nanosized electrodes might be perfect candidatesamong various electrode materials. However, consideringpractical battery application, nanosized electrodes have too lowtap and packing density to yield enough volumetric and massenergy density, but they possess very high specic surface areaand high surface energy, whichmay give rise to security issues.28

According to the previous literature reports, cathodes withmicro/nano hierarchical structures may be the most appro-priate candidates because they can possess both the advantagesof nanometer-sized building blocks and microsized assemblies,in which the former provide shorter ions/electrons transportpath and the latter guarantee good structural stability.29,30

Despite the laudable works in constructing micro/nano hierar-chical structured electrode materials, the large-scale industrialproduction of LNCM cathode materials with smaller size (3 mm)remains a great challenge.

Herein, we report a general size-controlled strategy to fabri-cate cathode material Li[Ni0.6Co0.2Mn0.2]O2 with 3 mm in

This journal is © The Royal Society of Chemistry 2016

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diameter by a hydroxide co-precipitation and high temperaturelithiation process. For comparison, we also prepared cathodematerials Li[Ni0.6Co0.2Mn0.2]O2 with 6 mm and 12 mm diameter.The obtained results indicate that Li[Ni0.6Co0.2Mn0.2]O2 havingsmaller size (3 mm) showed more outstanding performancescompared with that of the larger Li[Ni0.6Co0.2Mn0.2]O2 (12 mm)in terms of rate capacity, low temperature characteristics andcycling life. The proposed smaller size cathodes strategy canalso be extended to design and prepare other cathodes towardssuperior performances for LIBs.

2. Experimental2.1 Materials

Nickel sulfate hexahydrate (NiSO4$6H2O), manganesesulphate monohydrate (MnSO4$H2O), cobalt sulphate hep-tahydrate (CoSO4$7H2O), sodium hydroxide (NaOH), andammonium hydroxide (NH4OH) are of analytical grade andused as received without any further purication.

2.2 Preparation of precursors and lithiated layered oxides

Spherical precursors [Ni0.6Co0.2Mn0.2](OH)2 with different sizeswere synthesized via hydroxide co-precipitation method, asshown in Fig. 1.

Synthesis of spherical precursors [Ni0.6Co0.2Mn0.2](OH)2(NCM-3, NCM-6, NCM-12). Taking NCM-3 as an example, rstly,4 M NH4OH solution was added into the continuously stirredtank reactor (CSTR) as the base solution. Then, 2.5 L of 2 Mmetal sulfates (Ni : Co : Mn ¼ 6 : 2 : 2, molar ratio) was dis-solved in deoxidized water and pumped into the CSTR undera nitrogen atmosphere. Moreover, 2.5 L of 4 M NaOH solutionand 2 M NH4OH solution were pumped into the reactor undera constant specic pH value (11.8). During the reaction, thetemperature was kept at 60 �C, stirring speed was controlled at1000 rpmmin�1, feeding time was 4 h and ageing time was 10 h.Aer the reaction, the hydroxide precursor (NCM-3) was ob-tained aer washing with distilled water and nally dried at110 �C for 24 h. The other two precursors (NCM-6 and NCM-12)were prepared via a similar co-precipitation route except that

Fig. 1 Schematic of the synthesis procedure for cathode material Li[Ni0

This journal is © The Royal Society of Chemistry 2016

different amounts of base solution (3 M NH4OH, 2 M NH4OH,respectively), chelating agent (1.5 M NH4OH, 1 M NH4OH,respectively), pH values (11.4, 11.0, respectively), stirring speed(700 rpmmin�1, 500 rpmmin�1, respectively), and feeding time(10 h, 26 h, respectively) were employed.

Synthesis of spherical precursors Li[Ni0.6Co0.2Mn0.2]O2

(LNCM-3, LNCM-6, LNCM-12). The obtained [Ni0.6Co0.2-Mn0.2](OH)2 precursors (NCM-3, NCM-6, NCM-12) were thor-oughly mixed with LiOH$H2O with a molar ratio of 1 : 1.05 andwere calcined at 800 �C for 15 h in air to obtain sphericallithiated layered oxides (LNCM-3, LNCM-6, LNCM-12).

2.3 Characterization

The chemical compositions of as-obtained precursors weredetermined by inductively coupled plasmas spectrometer (ICP,6000 Series, Thermo SCIENTIFIC). Powder X-ray diffraction(BRUKER D8 Focus Diffractometer) with Cu Ka radiation wasused to identify the crystalline phase of the prepared materialsin the range of 10–80� (2q) with a step size of 0.03�. Themorphology of the precursors and lithiated oxides was observedby means of scanning electron microscope (SEM, Philips XL30)at an accelerating voltage of 10.0 kV. BET surface area and poresize measurements were carried out by N2 adsorption at 77 K onan Autosorb iQ Station 2. Tap densities were determined usinga tap-density tester (ZS-201, Liaoning Instrument ResearchInstitute Co. Ltd.).

2.4 Electrochemical measurements

The positive electrode was prepared by blending the cathode Li[Ni0.6Co0.2Mn0.2]O2, acetylene black, and PVDF (80 : 10 : 10 inweight ratio) in NMP. The slurry was cast on Al foil with theareal mass loading of 5.5� 0.5 mg cm�2, and dried at 120 �C for12 h under vacuum, followed by roll-pressing. Pure lithium foilwas used as the anode. The electrolyte consisted of 1 M LiPF6 inethylene carbonate (EC) and diethyl carbonate (DEC) (1 : 1 involume). A glass microber lter (934-AH, Whatman, UK) wasused as the separator. The half-cells were assembled in anAr-lled glove-box with CR2032 coin half cells. Charge anddischarge measurements were carried out at different current

.6Co0.2Mn0.2]O2.

RSC Adv., 2016, 6, 97818–97824 | 97819

Table 1 Intensity ratio of I003/I104 of the Li[Ni0.6Co0.2Mn0.2]O2 beforeand after cycles

Sample

Before cycle Aer cycle

I003/I104 I003/I104

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densities in the voltage range of 3.0–4.4 V (vs. Li+/Li) usinga NEWARE battery test system (CT-3008) at 25 �C and 0 �C.Electrochemical impedance measurements were carried outusing a Solartron 1255 B frequency response analyzer (Solar-tronInc., UK) in the frequency range of 100 kHz to 10 mHz,applying an AC signal of 10 mV amplitude voltage.

LNCM-3 1.4423 1.4368LNCM-6 1.3246 —LNCM-12 1.3389 0.8289

3. Results and discussion

3.1 Material characterization

Atomic ratios of Ni, Co, Mn in as-prepared precursors areanalyzed by ICP, and the values are listed in Table S1, ESI.†From the ICP results, we can conrm that the chemicalcompositions of the measured samples are approximately[Ni0.6Co0.2Mn0.2](OH)2. Fig. 2 exhibits the XRD patterns of theas-prepared precursors and cathode materials with differentsizes. It can be clearly seen that the XRD pattern of theprecursors is in accordance with the typical M(OH)2 (M ¼ Ni,Co, Mn) structure. The absence of impurity phases indicatesthat Ni, Co andMn have been homogeneously distributed in theprecursor particles.32 Moreover, it is also found that all thepeaks of the three cathode samples can be indexed witha typical layered structure based on the hexagonal a-NaFeO2

structure with space group R�3m without any impurity phases, asshown in Fig. 2b. In addition, it is observed that the clearsplitting of the (006)/(102) and (108)/(110) pairs is an indicationof the formation of a well-crystallized layered structure for thethree samples.31,32 The intensity ratio of I003/I104 is indicative ofundesirable cation mixing and the ratio lower than 1.2 indicatesthe migration of some Ni2+ ions to Li+ sites, blocking thechannel for Li+ ion transport.33 As expected, the ratio of I003/I104of these cathodes are higher than 1.2 (Table 1). From theseresults, we can conclude that the difference in the particle sizedoes not signicantly change crystal structure.

Fig. 3 shows the comparison of the SEM images of theprecursors and cathodes Li[Ni0.6Co0.2Mn0.2]O2 with differentsizes. Every kind of precursor and cathode shows homogeneousspherical secondary particles assembled with densely aggre-gated nanorods (Fig. 3a and d), nanoneedles (Fig. 3b and e) andnanoparticles (Fig. 3c and f), and average sizes are 3 mm(Fig. 3g), 6 mm (Fig. 3h) and 12 mm (Fig. 3i), respectively. Theformation mechanism of the different nanostructures might beattributed to different amounts of NH4OH and stirring speed.

Fig. 2 Powder XRD patterns of (a) the precursors [Ni0.6Co0.2Mn0.2](OH)

97820 | RSC Adv., 2016, 6, 97818–97824

Adding large amounts of NH4OH and high stirring speed are infavor to formation of the primary grain nanorods and assem-bling into the secondary particles (NCM-3). In contrast, lowconcentration of NH4OH and low stirring speed are prone toform secondary particles composed of primary nanoparticles(NCM-12). However, NCM-6 is in between NCM-3 and NCM-12,which is in accordance with the previous relevant literature.34

The size statistic results are based on the analysis of SEMimages in Fig. S1, ESI.† The tap densities of the three cathodes(LNCM-3, LNCM-6, LNCM-12) are 1.9, 2.3 and 2.6 g cm�3,respectively. The specic surface area and pore size of LNCM-3and LNCM-12 are measured to be 139.8 m2 g�1, 4.0 nm and85.9 m2 g�1, 3.8 nm, respectively (Fig. 4). These resultsdemonstrate that the particle size and microstructure of thehydroxide precursors can be easily controlled via hydroxide co-precipitation method.

3.2 Electrochemical properties

To study the size and microstructure effects of the cathodeson electrochemical performances, we take two typical sizecathodes (3 mm and 12 mm) as example to evaluate theirelectrochemical performances via 2032 coin half cells atroom temperature (25 �C) and low temperature (0 �C). Fig. 5aand c show the initial charge–discharge curves of both Li[Ni0.6Co0.2Mn0.2]O2 cathodes from 18 mA g�1 (0.1C) to 900mA g�1 (5C) between 3.0 and 4.4 V at 25 �C. Notably, bothcathodes have almost the same initial charge capacity ofabout 208 mA h g�1, the cathode with smaller size (3 mm) hada higher discharge capacity of 196 mA h g�1 accompaniedwith higher initial coulombic efficiency (94.4%) as shown inFig. 5a. However, LNCM-12 has a relatively lower discharge

2, and (b) the cathodes Li[Ni0.6Co0.2Mn0.2]O2 with different sizes.

This journal is © The Royal Society of Chemistry 2016

Fig. 3 SEM images of low- and high-magnification of [Ni0.6Co0.2Mn0.2](OH)2 (a–c) and Li[Ni0.6Co0.2Mn0.2]O2 (d–f); (a and d) 3 mm; (b and e) 6mm; (c and f) 12 mm, and the corresponding size distribution of Li[Ni0.6Co0.2Mn0.2]O2 (g–i).

Fig. 4 (a) N2 adsorption/desorption isotherms of LNCM-3 and LNCM-12; (b) pore size distribution of LNCM-3 and LNCM-12.

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capacity of 189 mA h g�1 with relatively lower coulombicefficiency of 90.4% (Fig. 5c). The same phenomenon can alsobe observed under the low temperature environment test, asshown in Fig. 5b and d. Furthermore, the rate capacity of bothcathodes is also evaluated at varying current rates rangingfrom 0.1C to 5C (Fig. 5e and f) at 25 �C and 0 �C. As expected,LNCM-3 delivers a much higher capacity than LNCM-12 ateach current rate. At 25 �C, the average specic capacities forLNCM-3 were 196, 185, 178, 170, 165, and 156 mA h g�1 at

This journal is © The Royal Society of Chemistry 2016

current rates of 0.1C, 0.2C, 0.5C, 1C, 2C and 5C, respectively.Surprisingly, the initial discharge capacity of LNCM-3 is157 mA h g�1 at a rate of 1C at 0 �C, which is much higherthan that of LNCM-12 at the same rate (123 mA h g�1). Thisexcellent low-temperature capacity can be comparable withthat of commercially available LiCoO2 and LiFePO4 under thecondition of the room temperature.

Inspired by the smaller size cathode performance, longcycling performances of 3 mm- and 12 mm-size cathode

RSC Adv., 2016, 6, 97818–97824 | 97821

Fig. 5 Typical charge–discharge profiles of LNCM-3 (a) at 25 �C and (b) 0 �C; and LNCM-12 (c) at 25 �C and (d) 0 �C with different rates. Ratecapacity of LNCM-3 and LNCM-12 (e) at 25 �C and (f) 0 �C; cycling performance of LNCM-3 and LNCM-12 (g) at 25 �C and (h) at 0 �C between 3.0and 4.4 V.

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materials at current density of 1C were studied and the resultsare shown in Fig. 5g and h. LNCM-3 shows excellent cyclingperformance over the LNCM-12 with capacity retention of 96%and 98% aer 300 cycles at 25 �C and 0 �C, respectively. Incontrast, LNCM-12 shows a rapid capacity loss especially at lowtemperature, resulting in capacity retention of 88% and 50% at25 �C and 0 �C, respectively. The properties of LNCM-3 in termsof cycle, rate capacity, and low-temperature are much superiorto those of the reported Li[Ni0.6Co0.2Mn0.2]O2-based cathodes(Table S2, ESI†), suggesting the effectiveness of our strategy inimproving the electrochemical performance. Moreover, post-mortem SEM images show that the spherical morphologies ofLNCM-3 can still be well maintained even aer 300 cycles(Fig. 6a and b).

97822 | RSC Adv., 2016, 6, 97818–97824

Such excellent electrochemical performance is mainlyattributed to its advantageous structural stability of hierarchicalnanorods assembled with 3 mm spherical secondary particlesand the faster kinetics of ions and electrons transport comparedto that of the 12 mm-size particles. In addition, the largerspecic surface area and pore size of LNCM-3 might alsocontribute to the high capacity of reversibility via providingsufficient contact between electrolyte and inner particles.35,36

XRD tests are also carried out with the sample aer 300 cycles tofurther study the structural stability of LNCM-3 and LNCM-12.As shown in Fig. 6c, the lattice parameters of LNCM-3 cathodeare almost identical to the pristine electrode, the clear peaksplitting of the (006)/(102) and (108)/(110) pairs indicates thatthe well layered structure is maintained aer 300 cycles.

This journal is © The Royal Society of Chemistry 2016

Fig. 7 EIS spectra of (a) LNCM-3 and (b) LNCM-12 cathodes before and after 300 cycles.

Fig. 6 SEM images of (a) LNCM-3 and (b) LNCM-12 after 300 cycles. (c) XRD patterns of LNCM-3 and LNCM-12 after 300 cycles.

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However, the LNCM-12 cathode has a severely weak peakintensity of I(003)/I(104) compared to that of the LNCM-3 cathode,as shown in Table 1, owing to the changes of crystal structurefrom Li+/Ni2+ mixing. The occupation of Ni2+ in the Li layerleads to the gradual declination of the capacity upon cycling.

To further understand the electrode reaction kinetics of boththe samples, the EIS spectra is given in Fig. 7. The solid dotswere the experimental results and the solid lines were tted byZSimpWin soware with the proposed equivalent circuit model(inset of Fig. 7). Rs is the solution resistance. Rsf and Csf are theresistance and the associated constant phase element of thesurface lm, respectively. Rct and Cdl are the charge transferresistance and constant phase element at the electrode/electrolyte interface, respectively. Zw is Warburg impedance.Apparently, the EIS spectra of both electrodes are almost over-lapped before the cycle. However, aer 300 cycles, the Rsf and Rct

of the LNCM-3 cathode are much smaller than that of theLNCM-12 cathode, indicating a lower lm resistance and chargetransfer resistance for the LNCM-3, which is benecial to itselectrochemical performances.

4. Conclusions

In summary, three cathodes (Li[Ni0.6Co0.2Mn0.2]O2) weresuccessfully synthesized via a co-precipitation method followedby a high temperature lithiation process. The size and micro-structure of the precursors can be easily tailored by controllingfeeding time, ammonium hydroxide concentration, pH value,

This journal is © The Royal Society of Chemistry 2016

and stirring rate during the reaction process. The smaller sizeparticle, unique microstructure, and porous characteristicscontribute to the excellent electrochemical performances.Impressively, when evaluated as cathode materials for LIBs, Li[Ni0.6Co0.2Mn0.2]O2 with 3 mm-size exhibits a high reversiblecapacity (194 mA h g�1 at 18 mA g�1), excellent rate capacity(156 mA h g�1 at 900 mA g�1), remarkable low-temperatureproperty (157 mA h g�1 at 180 mA g�1), and ultralong lowtemperature cycling life (300 cycles, capacity retention of 99% ata current density of 180 mA g�1). The proposed smaller sizecathodes strategy can be extended to design and prepare othercathodes for superior power LIBs.

Acknowledgements

The authors are most grateful to the NSFC, China (21225524,21505127 and 21501169), the Department of Science andTechniques of Jilin Province (20150203002YY, 20150201001GXand 20150204065GX) and special funds for the Construction ofTaishan Scholars (No. ts201511058).

References

1 J. B. Goodenough and K. S. Park, J. Am. Chem. Soc., 2013, 135,1167–1176.

2 Z. Z. Wu, X. G. Han, J. X. Zheng, Y. Wei, R. M. Qiao, F. Shen,J. Q. Dai, L. B. Hu, K. Xu, Y. Lin, W. L. Yang and F. Pan, NanoLett., 2014, 14, 4700–4706.

RSC Adv., 2016, 6, 97818–97824 | 97823

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ishe

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30

Sept

embe

r 20

16. D

ownl

oade

d by

Cha

ngch

un I

nstit

ute

of A

pplie

d C

hem

istr

y, C

AS

on 0

4/01

/201

7 01

:44:

09.

View Article Online

3 P. Y. Hou, X. Q. Wang, D. G. Wang, D. W. Song, X. X. Shi,L. Q. Zhang, J. Guo and J. Zhang, RSC Adv., 2014, 4, 15923–15929.

4 B. Scrosati and J. Garche, J. Power Sources, 2010, 195, 2419–2430.

5 Y. K. Sun, B. R. Lee, H. J. Noh, H. Wu, S. T. Myung andK. Amine, J. Mater. Chem., 2011, 21, 10108–10112.

6 J. Z. Guo, X. L. Wu, F. Wan, J. Wang, X. H. Zhang andR. S. Wang, Chem.–Eur. J., 2015, 21, 17371–17378.

7 X. L. Wu, Y. G. Guo, J. Su, J. W. Xiong, Y. L. Zhang andL. J. Wan, Adv. Energy Mater., 2013, 3, 1155–1160.

8 X. H. Zhang, W. L. Pang, F. Wan, J. Z. Guo, H. Y. Lu, J. Y. Li,Y. M. Xing, J. P. Zhang and X. L. Wu, ACS Appl. Mater.Interfaces, 2016, 8, 20650–20659.

9 J. Y. Li, X. L. Wu, X. H. Zhang, H. Y. Lu, G. Wang, J. Z. Guo,F. Wan and R. S. Wang, Chem. Commun., 2015, 51, 14848–14851.

10 P. Mei, X. L. Wu, H. M. Xie, L. Q. Sun, Y. P. Zeng, J. P. Zhang,L. H. Tai, X. Guo, L. N. Cong, S. C. Ma, C. Yao and R. S. Wang,RSC Adv., 2014, 4, 25494–25501.

11 K. J. Kim, Y. N. Jo, W. J. Lee, T. Subburaj, K. Prasanna andC. W. Lee, J. Power Sources, 2014, 268, 349–355.

12 B. B. Lim, S. J. Yoon, K. J. Park, C. S. Yoon, S. J. Kim, J. J. Leeand Y. K. Sun, Adv. Funct. Mater., 2015, 25, 4673–4680.

13 J. M. Zheng, W. H. Kan and A. Manthiram, ACS Appl. Mater.Interfaces, 2015, 7, 6926–6934.

14 L. W. Liang, G. R. Hu, Y. B. Cao, K. Du and Z. D. Peng, J.Alloys Compd., 2015, 635, 92–100.

15 S. H. Ju, L. S. Kang, Y. S. Lee, W. K. Shin, S. Kim, K. Shin andD. W. Kim, ACS Appl. Mater. Interfaces, 2014, 6, 2546–2552.

16 C. C. Fu, G. S. Li, D. Luo, Q. Li, J. M. Fan and L. P. Li, ACSAppl. Mater. Interfaces, 2014, 6, 15822–15831.

17 S. Jouanneau, K. W. Eberman, L. J. Krause and J. R. Dahn, J.Electrochem. Soc., 2003, 150, A1637–A1642.

18 H. Kim, M. G. Kim, H. Y. Jeong, H. Nam and J. Cho, NanoLett., 2015, 15, 2111–2119.

97824 | RSC Adv., 2016, 6, 97818–97824

19 S. Y. Tan, L. Wang, L. Bian, J. B. Xu, W. Ren, P. F. Hu andA. M. Chang, J. Power Sources, 2015, 277, 139–146.

20 J. R. Ying, C. R. Wan and C. Y. Jiang, J. Power Sources, 2001,102, 162–166.

21 J. Cho, Chem. Mater., 2000, 12, 3089–3094.22 K. H. Jeong, H. W. Ha, N. J. Yun, M. Z. Hong and K. Kim,

Electrochim. Acta, 2005, 50, 5349–5353.23 D. Luo, S. H. Fang, Q. H. Tian, L. Qu, S. M. Shen, L. Yang and

S. Hdirano, J. Mater. Chem. A, 2015, 3, 22026–22030.24 F. F. Yang, Y. J. Liu, S. K. Martha, Z. Y. Wu, J. C. Andrews,

G. E. Ice, P. Pianetta and J. Nanda, Nano Lett., 2014, 14,4334–4341.

25 D. Luo, G. S. Li, C. C. Fu, J. Zheng, J. M. Fan, Q. Li andL. P. Li, J. Power Sources, 2015, 276, 238–246.

26 F. Wan, X. L. Wu, J. Z. Guo, J. Y. Li, J. P. Zhang, L. Niu andR. S. Wang, Nano Energy, 2015, 13, 450–457.

27 L. Zhou, D. Y. Zhao and X. W. Lou, Angew. Chem., Int. Ed.,2012, 1, 239–241.

28 Y. G. Guo, J. S. Hu and L. J. Wan, Adv. Mater., 2008, 20, 2878–2887.

29 A. M. Cao, J. S. Hu, H. P. Liang and L. J. Wan, Angew. Chem.,Int. Ed., 2005, 44, 4391–4395.

30 P. Remitha and N. Kalaiselvi, Nanoscale, 2014, 6, 14724–14732.

31 M. H. Lee, Y. J. Kang, S. T. Myung and Y. K. Sun, Electrochim.Acta, 2004, 50, 939–948.

32 K. J. Park, B. B. Lim, M. H. Choi, H. G. Jung, Y. K. Sun,M. Haro, N. Vicente, J. Bisquert and G. G. Belmonte, J.Mater. Chem. A, 2015, 3, 22183–22190.

33 K. M. Nam, H. J. Kim, D. H. Kang, Y. S. Kim and S. W. Song,Green Chem., 2015, 17, 1127–1135.

34 S. J. Yoon, S. T. Myung, H. J. Noh, J. Lu, K. Amine andY. K. Sun, ChemSusChem, 2014, 7, 3295–3303.

35 P. Y. Hou, L. Q. Zhang and X. P. Gao, J. Mater. Chem. A, 2014,2, 17130–17138.

36 P. Yue, Z. X. Wang, X. H. Li, X. H. Xiong, J. X. Wang, X. W.Wuand H. J. Guo, Electrochim. Acta, 2013, 95, 112–118.

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