Polyacrylonitrile-polyvinylidene fluoride as high-performance composite binder for layered Li-rich oxides

Polyacrylonitrile-polyvinylidene fluoride as high-performance composite binder for layered Li-rich oxides

Journal of Power Sources 359 (2017) 226e233 Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/lo...

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Journal of Power Sources 359 (2017) 226e233

Contents lists available at ScienceDirect

Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour

Polyacrylonitrile-polyvinylidene fluoride as high-performance composite binder for layered Li-rich oxides Feng Wu a, b, c, 1, Weikang Li a, 1, Lai Chen a, Yun Lu a, b, c, *, Yuefeng Su a, b, c, **, Wurigumula Bao a, Jing Wang a, b, c, Shi Chen a, b, c, Liying Bao a, b, c a

Beijing Key Laboratory of Environmental Science and Engineering, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, PR China Collaborative Innovation Center for Electric Vehicles in Beijing, Beijing 100081, PR China c National Development Center of High Technology Green Materials, Beijing 100081, PR China b

h i g h l i g h t s

g r a p h i c a l a b s t r a c t

 PAN is investigated as binder for Li1.2Mn0.6Ni0.2O2 (LMNO) electrodes.  LMNO with PAN-PVDF composite binder show better electrochemical performance.  Composite binder averts voids and cracks of LMNO electrodes.

a r t i c l e i n f o

a b s t r a c t

Article history: Received 27 March 2017 Received in revised form 10 May 2017 Accepted 19 May 2017

Layered lithium-rich Oxides (LLROs) suffer from serious capacity fading during the cycling especially when the size is in sub-micron or nanoscale. Here we report the polyacrylonitrile (PAN) as a binder to maintain the capacity of LLROs sized ~200 nm, the combined PAN with polyvinylidene fluoride (PVDF) achieve excellent cycle and rate performance as the composite binder taking advantages from both PAN and PVDF. The capacity retention of PAN-PVDF electrode after 40 cycles is 89.6%, comparing to the 77.5% of PVDF electrode and 85.1% of PAN electrode. The SEM images pronouncedly illustrates that PAN-PVDF as composite binder holds the active material on the laminates firmly, resulting few cracks and voids. The electrochemical impedance spectra indicate that averting those voids and cracks lead to lower resistance. The composite binder has played a significant role in improving the cycling and rate performance of LLROs. © 2017 Elsevier B.V. All rights reserved.

Keywords: Polyacrylonitrile Polyvinylidene fluoride Layered lithium-rich oxide material Composite binder

1. Introductions

* Corresponding author. Beijing Key Laboratory of Environmental Science and Engineering, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, PR China. ** Corresponding author. Beijing Key Laboratory of Environmental Science and Engineering, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, PR China. E-mail addresses: [email protected] (Y. Lu), [email protected] (Y. Su). 1 F. Wu and W. Li contribute equally to this work. http://dx.doi.org/10.1016/j.jpowsour.2017.05.063 0378-7753/© 2017 Elsevier B.V. All rights reserved.

Rechargeable Li-ion batteries (LIBs) are now in a boom age [1,2]. Cathode materials possess the most significant role in development of high power and high energy density LIBs. In recent years, layered lithium-rich oxides with the formula xLi2MnO3$(1-x)LiMO2 (M ¼ Ni, Co, Mn, etc.) have been considered a cathode candidate for advanced LIBs because of their remarkably high capacity (over 300 mAh g1) with fairly low price [3e7]. However, several

F. Wu et al. / Journal of Power Sources 359 (2017) 226e233

problems hinder the commercialization of these materials including low initial columbic efficiency due to the irreversible reaction of the Li2MnO3 component, the poor rate capability because of the low conductivity and Li-ion diffusion coefficient, let alone voltage fade and the poor cycling performance. Owing to efforts from researchers, varieties of methods have been introduced. Lithium-lacking metal oxides such as Al2O3 [8,9] and ZrO2 [10] coating outside LLROs could significantly increase the initial coulombic efficiency. Doping other cations such as Ti4þ/Mg2þ into the lattice [11,12] or introducing spinel compound [13,14] as coating layer helps improve LLROs rate performance. Designing the structure/size of the particles [15,16] or tuning the planes [17,18] could be other operative ways to achieve high rate performance. In view of the cyclability of LLROs, it is generally considered that smaller particle size leads to higher specific capacity because of the more exposed active sites for Li-ion intercalating/deintercalating [19], while the stability is far more worse since the smaller sized materials are more likely to undergo side reactions with the electrolyte. More particularly, the formation of hydrofluoric acid can rapidly corrode the structure of material, causing severe capacity fade [20e22]. Coating metal fluoride such as AlF3 on sub-micron particles of LLROs has been carefully investigated by Sun et al. [23], they believed that AlF3 coating layer induced LLROs changed from layer to spinel-like structure, and this transforming could stabilize LLROs and consequently enhance the cycle performances. All these methods and techniques are restricted to the material. Only focusing on this may severely limit the practical application of LLROs. Other contents of the electrode such as current collector, conductive additive(s) and binder have a great influence as well. It has been reported that binders could significantly influence the electrochemical performance of LIBs [24e30]. As for LLROs, usually their operating electrochemical window ranges in 2e4.8 V, in this case binder is encountering more rigorous requirements, including outstanding stability in high voltage, minimal resistance to accelerate the electron transfer and even be as a shield to protect the surface of LLROs particles. In the past two decades, Poly(vinylidene fluoride) (PVDF) was the mainly used binder due to its electrochemical stability, binding capability and electrolyte absorbing ability. However, PVDF hinders Li-ion migration, resulting in poor rate performance. Other characteristics of PVDF such as easy to be swollen, gelled, or dissolved in non-aqueous electrolytes may also lead to cycling and safe issues [31,32]. Thus, finding the alternatives to match well with the active materials becomes a hotspot. The application of guar gum (GG) as a binder for LLROs could strengthen the inflexibility of laminates while significantly suppress voltage and capacity fading of the LLROs. Guar gum functions as both a binder and a coating agent in this case [33]. Sodium carboxymethyl cellulose (CMC) and sodium alginate (SA) have been applied to LLROs as well [34]. It has been reported that Polyacrylonitrile (PAN) is a candidate binder for many other materials [35e37], because the nitrile groups in PAN can form strong interactions with their environments by hydrogen bonding and dipoleedipole interactions, thus made PAN a proper binder for sorts of electrode materials [35]. Furthermore, coherent use of different binders has become a new thought [38e40]. Herein, we applied PAN as a binder to the LLROs, the results show that when combining PAN with PVDF as composite binder for sub-micron LLROs particles can help to achieve better cycle and rate performance than separately using PAN or PVDF. For PAN, its good stability under high voltage and swelling-resistance in the electrolyte make it suitable for LLROs. For PVDF, its wettability in the electrolyte guarantee the good contact between the active material and electrolyte. The composite binder take the advantage of PAN and PVDF, so the better electrochemical performance of the material can be achieved. This may provide a new strategy to relieve the defect of LLROs, and we believe this research


may benefit other high-voltage or nanoscale cathode materials. 2. Experiment 2.1. Synthesis & preparation Two kinds of commercial polymers were applied here: Polyvinylidene fluoride (MTI Corporation, HSV900), Polyacrylonitrile (J&K Corporation, M.w. 150,000). The LLRO material with a chemical formula of Li1.2Ni0.2Mn0.6O2 was synthesized by a facile SolGel method as reported before [41e43]. The cathode laminate was fabricated by controlling the ratio of pristine powder, acetylene black and binder to 8:1:1 by doctor blade method. The content of the binder for different electrodes was PVDF, PVDF (50%) with PAN (50%) and PAN. The pristine material and acetylene black were first ground together for 20 mins, and then the prepared polymer dissolving in N-Methyl pyrrolidone (NMP) solution was added, another 10 mins grinding was applied before depositing the slurry on Al foil. The electrolyte was 1 M LiPF6 dissolved in a mixture of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate (1:1:1 vol ratio). The 2025 coin-type half cells were assembled in a glovebox filled with argon, lithium metal was the counter electrode and Celgard 2400 membrane was the separator. The electrode loadings were maintained at ~2.0 mg cm2. 2.2. Electrode characterization The as-prepared electrodes, binder powder and pristine LLROs material were directly tested by X-ray diffraction (XRD) (Rigaku, Model Ultima IV-185) with a Cu Ka radiation source, scanned from 2q ¼ 10 e90 at a scan rate of 2 per minute. A field-emission scanning electron microscopy (FESEM) system (FEI QUANTA 250) was used to analyze the morphology of the polymers and electrodes. Three kinds of laminates were soaked in the electrolyte (Vol. 2 mL) as well as the powder of PVDF and PAN (Vol. 4 mL) for seven days in the glove-box (Ar) to obtain the photos. The inductively coupled plasma mass spectrometry (ICP-MS) was tested by Agilent 7500ce (Agilent Technologies, U.S.A). 2.3. Electrochemical test Galvanostatic tests were performed on CT2001A Land instruments (Wuhan, China) ranging potential from 2 V to 4.8 V at 30  C in thermostatic chamber. The current density of 250 mA g1 was defined as 1C rate during the test. Electrochemical impedance spectra (EIS) of the cells were conducted on the CHI660D (Shanghai, China) electrochemical workstation at frequencies from 105 Hz to 1 Hz. Cyclic Voltammetry of PAN cells were test on the same device. 3. Results and discussions 3.1. Morphologies characterizations The morphologies of various powders and electrodes are presented in Fig. 1. As shown in Fig. 1(a), the pristine material of LLROs consists of sub-micron particles, with uniform size as well as polyhedron shape. Fig. 1(b) and (c), and the insets display the images of PVDF and PAN before and after using as the binder. Interestingly, PVDF and PAN differs in morphology. PVDF is roe-like shape and unfolded in NMP solvent to form a chain-like binder while PAN changes from cobblestone-like shape to compacted thin film. To test whether the composite binder dissolved in NMP react with each other, Fourier transform infrared spectroscopy (FTIR) was


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Fig. 1. Microstructure images of the (a) pristine LLROs material (b) PVDF powder, (c) PAN powder; the inset graphs in (b) and (c) are the polymers dissolved in the NMP (solvent) and then deposited on the Al foil.

conducted. The results are shown in Fig. S1. It can be seen that the curve of the binder after dissolved show no obvious change, which means no chemical reactions happen during the process. The structures of the as-synthesized pristine LLROs material and electrodes is characterized by X-ray diffraction (XRD), shown in Fig. S2. Most of the XRD diffractions show Bragg lines that correspond to the layered a-NaFeO2 structure (R-3m space group) except the weak peaks between 20 and 25 (2q) caused by Liþ/Mn4þ cation ordering in the transition-metal layers of Li2MnO3 (C2/m) component. The c/a ratio and the I(003)/I(104) are 4.98 and 1.44 separately, combining that the apparently split of (006)/(012) and (018)/ (110), all these clues suggest a well layered structure with low Liþ/ Ni2þ cation mixing [44e46]. The absolute peak intensity of three electrodes are declined due to the partial coverage of amorphous acetylene black and semi-crystalline binders on the surface. However, the shape of patterns remains to be the same except for the peaks from Al foil. Obviously, PAN or PAN-PVDF composite binder would not affect the structure of LLROs.

3.2. Stability characterizations The structural information of PAN and PVDF is shown in Fig. 2(a) and (b). It can be seen from the XRD patterns that both PAN and PVDF are semicrystalline powders with a distinct peak position at low diffraction angles, the crystallinity of PVDF is higher than that of PAN. The crystallinity of polymer powder influences the morphologies of polymer films [47] so that the morphology of the electrode might be different. The stability of PAN binder itself and the prepared laminates were measured by soaking them in electrolyte for 7 days. As can be seen in Fig. 2(c), the negligible swelling and solubility of PAN is presented, while PVDF became semitransparent after 7 days. This phenomenon is consistent with other reports [29] that PVDF is easy to swell and with a better rate of electrolyte uptake. In contrast, PAN is not obviously swelling in the electrolyte and the uptake rate is less. The laminates soaking in the electrolyte remains unchanged for seven days, and the electrolyte has maintained a colorless and transparent state (see Fig. 2(d)), which also shows the stability of PAN in the electrolyte. To compare the stability of PAN with PVDF in the electrolyte furtherly, we soak three different laminates in the electrolyte seven days, and then detect the Manganese and Nickel content in the electrolyte with ICP-MS, the results are shown in Table 1. It is found that the content of Mn and Ni in the electrolyte were 1893.75 mg L1 and 525.75 mg L1 respectively for PVDF sample. However, for the added-PAN samples, the content of Mn and Ni is remarkably low, especially for pure PAN samples, only 278.05 mg L1 and 135.325 mg L1 were detected. Through this test, the stability of PAN in the electrolyte is further confirmed.

3.3. Electrochemical performances The first two cycles of PVDF, PAN and PAN-PVDF electrodes are illustrated in Fig. S3; all of three electrodes demonstrate the typical platform when charged to ~4.5 V at the initial cycle, which is caused by the activation of Li2MnO3 component [44,48e50]. The PANPVDF electrode delivers the highest initial charge capacity reaching 380.4 mAh g1. According to Kim's work [51], PAN showed sufficient electrochemical stability over 5.0 V (vs. Liþ/Li). Galvanostatic test (1C ¼ 250 mA g1, 2e4.8 V) using PAN as active material demonstrate that PAN provides insignificant capacity. The recognizable current detected in cyclic voltammetry (CV) test (see in Fig. S4 and its inset) may due to the negligible decomposition of electrolyte, therefore the high initial charge capacity should not because of side reaction from PAN. The first two discharge capacities of PAN-PVDF is higher than that of PVDF or PAN electrode. The cycle performance of PVDF, PAN and PAN-PVDF electrodes at 0.1C are displayed in Fig. 3(a), after 40 cycles the capacity of them are 240.8, 228.2, 202.7 mAh g1, the related retentions are 89.6%, 85.1% and 77.5% respectively. More proportions of composite binders for the active materials are provided in Fig. S5, all the data suggest that PAN helps to maintain the capacity. The rate performance of three electrodes at discharge rate of 1C, 2C, and 5C are shown in Fig. 3(b), the capacity retentions of PAN-PVDF electrode at 1, 2, and 5C are 86.3%, 80.2% and 70.2% respectively, comparing to the 82.6%,74.3% and 59.5% of PAN electrode and 80.0%, 68.6% and 35.4% of PVDF electrode. The PAN-PVDF electrode exhibits enhanced rate capability. Fig. 3(c) demonstrates the cycling performance of three different electrodes at 1C rate, all of them are firstly activated at 0.1C in 2e4.8 V for one cycle. It is clearly that the PAN-PVDF is more stable than the other two, the remaining capacity of PAN-PVDF after 100 cycle is 178.3 mAh g1, the compared PVDF sample and PAN sample are 149.4 mAh g1 and 171.8 mAh g1 respectively. The PAN-PVDF composite binder improves cycle and rate performance of LLROs. Fig. 4 illustrates the differential capacity curves of PVDF (a), PAN (b) and PAN-PVDF (c) electrodes. As can be seen from the shift of the peak position, three electrodes have almost the same degree of voltage fade; the DV of all electrodes is 0.17 V from the 2nd cycle to the 40th cycle. We separated the capacity of selected cycles and figure out the pattern in Fig. 4(e) and (f), as the layered component usually deliver capacity above 3.5 V (vs. Liþ/Li) while spinel-like component below 3.5 V (vs. Liþ/Li) [52]. The capacities above 3.5 V of all three electrodes are monotonically decreasing with the similar slope except the very beginning of the cycles. The PVDF sample decreases more severely at the first few cycles. The capacities below 3.5 V of different electrodes exhibit more differences. For PAN-PVDF and PAN electrodes, the capacities below 3.5 V

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Fig. 2. Sketch map of PAN and PVDF (a); the XRD patterns of different binder powder (b); pictures of different binders (c) and laminates (d) soaked in the electrolyte in the 1st day and 7th day.

Table 1 The concentration of manganese and nickel in the electrolyte after the laminates were soaked for 7 days. Sample

Mn/mg L1

Ni/mg L1


1893.75 278.05 338.87

525.75 135.325 166.9

increase as the cycle progresses. For PVDF electrode, the capacity remain unchanged, this can be explained by “equilibrium effect”, that is the active material transfer from layered to spinel-like to lead the capacity below 3.5 V increase while some of them fell off from the laminate to make the capacity below 3.5 V decrease, so the capacity remains unchanged. This offers another evidence that the PAN helps hold the sub-micron LLROs material. Thus, the capacity fade caused by structure changing from layered structure to spinellike [53e55] can be eliminate. PVDF or PAN as conventional polymeric binders could not act to alleviate voltage fade. To better elucidate the impact of the binders on the cycle and rate performance, the LLROs electrodes with different binders before and after 40 charge-discharge cycles at 0.1C (2e4.8 V) were

investigated by SEM. It can be seen from Fig. 5(a), (b) and (c) that the morphologies of the electrodes before cycles are almost the same, no obvious cracks or voids can be seen from the SEM images. Nevertheless, the images after cycles (Fig. 5(d), (e) and (f)) have changed, some voids and cracks appear in PVDF samples, which is due to the fall of active material, and the crack indicates that PVDF has dissolved or decomposed during the high voltage cycles. Some cracks also can be found on PAN sample, and the inset of Fig. 5 shows part of the material is covered by a layer of electrolyte decomposition products [56]. From the image of PAN-PVDF electrode, the connection between particles is better preserved. These images prove that the active material in PAN-PVDF sample is less dissolved out so that the capacity retention is improved. The electrochemical impedance spectroscopy (EIS) tests were arranged during certain cycles. The results are presented in Fig. 6; all three electrodes show similar features: two depressed semicircles. A possible equivalent circuit is proposed in the inset of Fig. 6(a). Rs corresponds to the solution resistance, Rf is supposed to be the surface film resistance including the CEI (cathode electrolyte interface) formed by the decomposition of the electrolyte in the high voltage range [56,57], while Rct is on behalf of the chargetransfer resistance [58], Ws is the Warburg impedance associated


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Fig. 3. Electrochemical performances of different electrodes at (a) 0.1C charge/discharge (b) rate of 1C, 2C and 5C discharge and (c) 1C charge/discharge.

Fig. 4. Differential capacity curves of PAN-PVDF(a), PAN(b) and PVDF(c) electrodes, divided capacity above 3.5 V(e) and below 3.5 V(f).

with lithium diffusion in electrodes. In our point of view, the effect of binder on the electrode impendence mainly influences on Rf and Rct. Therefore, Rf and Rct values of three different electrodes is simulated by the equivalent circuit calculation. The specific values are shown in Table 2, the values of Rf and Rct keep well at the

beginning of the cycle and after 40 cycles for PAN-PVDF electrode, whereas the value of PVDF electrode increases significantly, proving that the loss of the material resulted in impedance increase. For PAN electrode, it is interesting that Rf and Rct values at the 1st cycle are larger than those at 10th cycle, different electrolyte

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Fig. 5. SEM images of LLROs electrodes with (a and e) PVDF, (b and f) PAN, (c and g) PAN-PVDF; (a), (b) and (c) are pristine electrodes. (e), (f) and (g) are electrodes after 40 cycles, the inset graphs are affiliated enlarged views.

Fig. 6. Nyquist plots of different electrodes in 1st, 10th, 40th at the state of DOD(depth of discharge)z50%: (a) Summary graph of all electrodes, the inset shows the equivalent circuit, (b) (c) (d) represented the detailed views of PVDF electrode, PAN electrode, PAN-PVDF electrode respectively.


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Table 2 Rf and Rct of different electrodes in different cycles. Electrode









Cycle 1st 10th 40th

65.03 59.58 54.84

148.2 282.9 381.5

36.09 28.38 33.55

121.2 173.7 173.6

35.1 30.25 68.1

219.2 146.7 574.2

uptake rates of PAN and PVDF may contribute to this phenomenon [29]. The electrolyte may not completely infiltrate the electrode at the beginning, resulting in high impedance. Rf and Rct values of 40th cycle increases, probably due to fragility of PAN which lead to formation of scattered areas with broken conductive network. Fig. 7 presents the schematic view of our standpoint. We agree that other scholars have evolved the PVDF binder into a ribbon binder [59], and if the size of material particles is at microscale, PVDF is able to stick each active particle well on the laminates. However, if the size of the particles is significantly reduced, for example, to submicroscale or even the nanoscale, then a ribbon binder as PVDF may be difficult to construct a good bond to all particles. Under this circumstance, some of the particles may fall apart when the laminate is soaked in electrolyte, which is barely noticeable. The electrochemical properties of material and even the

safety of battery may deteriorate. On the other hand, the submicron LLROs particles bond by PVDF may encounter notable material peeling while during the 2e4.8 V cycling, causing distinct capacity fade. PAN as binder can help to alleviate undesirable exfoliation, but increase the resistance of the laminate because of the embrittlement of the electrode and some cracks may appear. PAN-PVDF composite binder exerts a synergistic effect, collaborating to reduce the dissolving of active materials and prevent enlargement of the impedance, which is beneficial for the electrochemical performance of LLROs. 4. Conclusion PAN-PVDF as a composite binder enhances the electrochemical properties of sub-micron size LLROs particles. Soaking tests illustrated that adding PAN would not influence the matured research system (LLROs with acetylene black and binder); SEM and EIS tests showed that the PAN-PVDF/PAN hold the active material well on the laminates, contributing to alleviating polarization of the LLROs electrodes with better cycle and rate performance. The retentions after 40 cycles at 0.1C of PAN-PVDF samples is 89.6%, better than that of PAN (85.1%) or PVDF (77.5%). The rate performance of PANPVDF samples has also been significantly improved, the specific capacity in 1C-charge/discharge of PAN-PVDF sample reaches 178.3 mAh g1. We believe that the research of matching active material with proper binder is definitely significant, and special

Fig. 7. Schematic view of electrodes with different binders.

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attentions should be payed to the high-voltage/nano-sized materials. Acknowledgements This work was supported by National Natural Science Foundation of China (51472032, 21573017, U1664255), National Key Research and Development Program (2016YFB0100400), Program for New Century Excellent Talents in University (NCET-13e0044) and Major Achievements Transformation Project for Central University in Beijing. Appendix A. Supplementary data Supplementary data related to this chapter can be found at http://dx.doi.org/10.1016/j.jpowsour.2017.05.063. References [1] M. Armand, J.M. Tarascon, Nature 451 (2008) 652e657. [2] A. Manthiram, J.C. Knight, S.-T. Myung, S.-M. Oh, Y.-K. Sun, Adv. Energy Mater. 6 (2016) 1501010. [3] N. Yabuuchi, K. Yoshii, S.T. Myung, I. Nakai, S. Komaba, J. Am. Chem. Soc. 133 (2011) 4404e4419. [4] M.M. Thackeray, C. Wolverton, E.D. Isaacs, Energy Environ. Sci. 5 (2012) 7854. [5] S. Muhammad, H. Kim, Y. Kim, D. Kim, J.H. Song, J. Yoon, J.-H. Park, S.-J. Ahn, S.H. Kang, M.M. Thackeray, W.-S. Yoon, Nano Energy 21 (2016) 172e184. [6] S. Hy, H. Liu, M. Zhang, D. Qian, B.-J. Hwang, Y.S. Meng, Energy Environ. Sci. 9 (2016) 1931e1954. [7] B. Qiu, M. Zhang, L. Wu, J. Wang, Y. Xia, D. Qian, H. Liu, S. Hy, Y. Chen, K. An, Y. Zhu, Z. Liu, Y.S. Meng, Nat. Commun. 7 (2016) 12108. [8] Y. Seok Jung, A.S. Cavanagh, Y. Yan, S.M. George, A. Manthiram, J. Electrochem Soc. 158 (2011) A1298. [9] Y.S. Lee, W.K. Shin, A.G. Kannan, S.M. Koo, D.W. Kim, ACS Appl. Mater. Interfaces 7 (2015) 13944e13951. [10] G.-H. Lee, I.H. Choi, M.Y. Oh, S.H. Park, K.S. Nahm, V. Aravindan, Y.-S. Lee, Electrochim. Acta 194 (2016) 454e460. [11] S. Wang, Y. Li, J. Wu, B. Zheng, M.J. McDonald, Y. Yang, Phys. Chem. Chem. Phys. 17 (2015) 10151e10159. [12] Y.X. Wang, K.H. Shang, W. He, X.P. Ai, Y.L. Cao, H.X. Yang, ACS Appl. Mater. Interfaces 7 (2015) 13014e13021. [13] F. Wu, N. Li, Y. Su, H. Lu, L. Zhang, R. An, Z. Wang, L. Bao, S. Chen, J. Mater. Chem. 22 (2012) 1489e1497. [14] F. Wu, N. Li, Y. Su, L. Zhang, L. Bao, J. Wang, L. Chen, Y. Zheng, L. Dai, J. Peng, S. Chen, Nano Lett. 14 (2014) 3550e3555. [15] F. Wu, Z. Wang, Y. Su, Y. Guan, Y. Jin, N. Yan, J. Tian, L. Bao, S. Chen, J. Power Sources 267 (2014) 337e346. [16] J. Yang, F. Cheng, X. Zhang, H. Gao, Z. Tao, J. Chen, J. Mater. Chem. A 2 (2014) 1636e1640. [17] G.Z. Wei, X. Lu, F.S. Ke, L. Huang, J.T. Li, Z.X. Wang, Z.Y. Zhou, S.G. Sun, Adv. Mater. 22 (2010) 4364e4367. [18] L. Chen, Y. Su, S. Chen, N. Li, L. Bao, W. Li, Z. Wang, M. Wang, F. Wu, Adv. Mater. 26 (2014) 6756e6760. [19] J.M. Zheng, X.B. Wu, Y. Yang, Electrochim. Acta 56 (2011) 3071e3078. , P. Bruce, B. Scrosati, J.-M. Tarascon, W. van Schalkwijk, Nat. Mater. 4 [20] A.S. Arico (2005) 366e377. [21] P.G. Bruce, B. Scrosati, J.M. Tarascon, Angew. Chem. Int. Ed. Engl. 47 (2008) 2930e2946. [22] K. Zhang, X. Han, Z. Hu, X. Zhang, Z. Tao, J. Chen, Chem. Soc. Rev. 44 (2015) 699e728. [23] Y.K. Sun, M.J. Lee, C.S. Yoon, J. Hassoun, K. Amine, B. Scrosati, Adv. Mater. 24 (2012) 1192e1196.


[24] G. Liu, H. Zheng, A.S. Simens, A.M. Minor, X. Song, V.S. Battaglia, J. Electrochem. Soc. 154 (2007) A1129. [25] G. Liu, H. Zheng, S. Kim, Y. Deng, A.M. Minor, X. Song, V.S. Battaglia, J. Electrochem. Soc. 155 (2008) A887. [26] G. Liu, H. Zheng, X. Song, V.S. Battaglia, J. Electrochem. Soc. 159 (2012) A214eA221. [27] Y.-H. Huang, J.B. Goodenough, Chem. Mater. 20 (2008) 7237e7241. [28] N. Loeffler, J. von Zamory, N. Laszczynski, I. Doberdo, G.-T. Kim, S. Passerini, J. Power Sources 248 (2014) 915e922. [29] S. Lee, E.-Y. Kim, H. Lee, E.-S. Oh, J. Power Sources 269 (2014) 418e423. [30] S. Gao, Y. Su, L. Bao, N. Li, L. Chen, Y. Zheng, J. Tian, J. Li, S. Chen, F. Wu, J. Power Sources 298 (2015) 292e298. re s, A. de Guibert, M. Broussely, J.M. Bodet, [31] P. Biensan, B. Simon, J.P. Pe F. Perton, J. Power Sources 81e82 (1999) 906e912. [32] S. Pejovnik, R. Dominko, M. Bele, M. Gaberscek, J. Jamnik, J. Power Sources 184 (2008) 593e597. [33] T. Zhang, J.T. Li, J. Liu, Y.P. Deng, Z.G. Wu, Z.W. Yin, D. Guo, L. Huang, S.G. Sun, Chem. Commun. (Camb) 52 (2016) 4683e4686. [34] Z. Han, H. Zhan, Y. Zhou, Mater Lett. 114 (2014) 48e51. [35] L. Gong, M.H.T. Nguyen, E.-S. Oh, Electrochem. Commun. 29 (2013) 45e47. [36] D.M. Piper, T.A. Yersak, S.-B. Son, S.C. Kim, C.S. Kang, K.H. Oh, C. Ban, A.C. Dillon, S.-H. Lee, Adv. Energy Mater. 3 (2013) 697e702. [37] J. Wang, M. Zhou, G. Tan, S. Chen, F. Wu, J. Lu, K. Amine, Nanoscale 7 (2015) 8023e8034. [38] Y. Wang, H. Zheng, Q. Qu, L. Zhang, V.S. Battaglia, H. Zheng, Carbon 92 (2015) 318e326. [39] Y. Wang, L. Zhang, Q. Qu, J. Zhang, H. Zheng, Electrochim. Acta 191 (2016) 70e80. [40] L. Wei, C. Chen, Z. Hou, H. Wei, Sci. Rep. 6 (2016) 19583. [41] J. Kou, L. Chen, Y. Su, L. Bao, J. Wang, N. Li, W. Li, M. Wang, S. Chen, F. Wu, ACS Appl. Mater. Interfaces 7 (2015) 17910e17918. [42] S. Chen, L. Chen, Y. Li, Y. Su, Y. Lu, L. Bao, J. Wang, M. Wang, F. Wu, ACS Appl. Mater. Interfaces 9 (10) (2017) 8641e8648. [43] S. Chen, Y. Zheng, Y. Lu, Y. Su, L. Bao, N. Li, Y. Li, J. Wang, R. Chen, F. Wu, ACS Appl. Mater. Interfaces 9 (10) (2017) 8669e8678. [44] N. Li, R. An, Y. Su, F. Wu, L. Bao, L. Chen, Y. Zheng, H. Shou, S. Chen, J. Mater. Chem. A 1 (2013) 9760. [45] B. Song, H. Liu, Z. Liu, P. Xiao, M.O. Lai, L. Lu, Sci. Rep. 3 (2013) 3094. [46] Y. Li, Y. Bai, C. Wu, J. Qian, G. Chen, L. Liu, H. Wang, X. Zhou, F. Wu, J. Mater. Chem. A 4 (2016) 5942e5951. [47] N. Yabuuchi, K. Shimomura, Y. Shimbe, T. Ozeki, J.-Y. Son, H. Oji, Y. Katayama, T. Miura, S. Komaba, Adv. Energy Mater. 1 (2011) 759e765. [48] A. Ito, K. Shoda, Y. Sato, M. Hatano, H. Horie, Y. Ohsawa, J Power Sources 196 (2011) 4785e4790. [49] S. Hy, F. Felix, J. Rick, W.N. Su, B.J. Hwang, J. Am. Chem. Soc. 136 (2014) 999e1007. [50] D. Ye, G. Zeng, K. Nogita, K. Ozawa, M. Hankel, D.J. Searles, L. Wang, Adv. Funct. Mater. 25 (2015) 7488e7496. [51] H.-S. Min, J.-M. Ko, D.-W. Kim, J. Power Sources 119e121 (2003) 469e472. [52] J. Zheng, M. Gu, A. Genc, J. Xiao, P. Xu, X. Chen, Z. Zhu, W. Zhao, L. Pullan, C. Wang, J.G. Zhang, Nano Lett. 14 (2014) 2628e2635. [53] W. Liu, P. Oh, X. Liu, S. Myeong, W. Cho, J. Cho, Adv. Energy Mater. 5 (2015) 1500274. [54] M. Sathiya, A.M. Abakumov, D. Foix, G. Rousse, K. Ramesha, M. Saubanere, M.L. Doublet, H. Vezin, C.P. Laisa, A.S. Prakash, D. Gonbeau, G. VanTendeloo, J.M. Tarascon, Nat. Mater. 14 (2015) 230e238. [55] Y. Xu, E. Hu, F. Yang, J. Corbett, Z. Sun, Y. Lyu, X. Yu, Y. Liu, X.-Q. Yang, H. Li, Nano Energy 28 (2016) 164e171. € rner, M. Grützke, X. Mo €nnighoff, P. Behrends, [56] Y. Qian, P. Niehoff, M. Bo S. Nowak, M. Winter, F.M. Schappacher, J. Power Sources 329 (2016) 31e40. [57] R. Chen, F. Liu, Y. Chen, Y. Ye, Y. Huang, F. Wu, L. Li, J. Power Sources 306 (2016) 70e77. [58] X. Zhu, Y. Wang, K. Shang, W. He, X. Ai, H. Yang, Y. Cao, J. Mater. Chem. A 3 (2015) 17113e17119. [59] W.-J. Song, S.H. Joo, D.H. Kim, C. Hwang, G.Y. Jung, S. Bae, Y. Son, J. Cho, H.K. Song, S.K. Kwak, S. Park, S.J. Kang, Nano Energy 32 (2017) 255e262.