A Journal of Accepted Article Title: Recent development of all-solid-state lithium secondary batteries with sulfide inorganic electrolytes Authors: Ruochen Xu, Shengzhao Zhang, Xiuli Wang, Yan Xia, Xinhui Xia, Jianbo Wu, Changdong Gu, and Jiangping Tu This manuscript has been accepted after peer review and appears as an Accepted Article online prior to editing, proofing, and formal publication of the final Version of Record (VoR). This work is currently citable by using the Digital Object Identifier (DOI) given below. The VoR will be published online in Early View as soon as possible and may be different to this Accepted Article as a result of editing. Readers should obtain the VoR from the journal website shown below when it is published to ensure accuracy of information. The authors are responsible for the content of this Accepted Article. To be cited as: Chem. Eur. J. 10.1002/chem.201704568 Link to VoR: http://dx.doi.org/10.1002/chem.201704568 Supported by 10.1002/chem.201704568 Chemistry - A European Journal Table of content Due to the increasing demand of security and energy density, all-solid-state batteries have become the promising next-generation energy storage devices to replace the traditional batteries with flammable organic electrolytes. In this review, we focus on the recent developments of sulfide inorganic electrolytes in all-solid-state batteries, and the challenges of assembling bulk-type all-solid-state batteries for industrialization are discussed. 1 This article is protected by copyright. All rights reserved. Accepted Manuscript TOC graphic 10.1002/chem.201704568 Chemistry - A European Journal Recent development of all-solid-state lithium secondary batteries with sulfide inorganic electrolytes Ruochen Xu [a], Shengzhao Zhang [a], Xiuli Wang *[a], Yan Xia [a], Xinhui Xia [a], [a] Dr. R. Xu, S. Zhang, Y. Xia, Prof. X. Wang, X. Xia, C. Gu, J. Tu State Key Laboratory of Silicon Materials, Key Laboratory of Advanced Materials and Applications for Batteries of Zhejiang Province, and School of Materials Science and Engineering, Zhejiang University Hangzhou 310027, China E-mail: email@example.com; firstname.lastname@example.org, email@example.com [b] Prof. J. Wu College of Physics & Electronic Engineering, Taizhou University Taizhou 318000, China 2 This article is protected by copyright. All rights reserved. Accepted Manuscript Jianbo Wu [b], Changdong Gu [a], and Jiangping Tu *[a] 10.1002/chem.201704568 Chemistry - A European Journal Abstract Due to the increasing demand of security and energy density, all-solid-state lithium ion batteries have become the promising next-generation energy storage devices to replace the traditional liquid batteries with flammable organic electrolytes. In this solid-state batteries. The challenges of assembling bulk-type all-solid-state batteries for industrialization are discussed, including low ionic conductivity of the present sulfide electrolytes, high interfacial resistance and poor compatibility between electrolytes and electrodes. Many efforts have been focused on the solutions for these issues. Despite some progresses have been achieved, it is still far away from practical application. The perspectives for future research on all-solid-state lithium ion batteries are presented. Keywords: All-solid-state; Sulfide inorganic electrolyte; Lithium secondary battery. 3 This article is protected by copyright. All rights reserved. Accepted Manuscript review, we focus on the recent developments of sulfide inorganic electrolytes for all- 10.1002/chem.201704568 Chemistry - A European Journal 1. Introduction Rechargeable lithium ion batteries (LIBs) are rapidly developing to meet the increasing requirements of energy storage with high energy and power density in recent years, which have become extremely significant in portable electronics and electric bring safety issues, including flammable organic electrolytes, thermal instability and toxic chemicals . However, LIBs have the irreplaceable position in large-scale energy storage devices which almost conquer the electronics market [5, 6]. For these reasons, bulk-type all-solid-state LIBs (ASSLIBs) without organic liquid electrolytes are a good choice to replace the traditional liquid batteries  . ASSLIBs made up of negative/positive electrodes, and solid electrolyte have high energy density due to the compressed structure. In addition, solid-state ionic electrolytes are inert toward metallic lithium and can resist the growth of lithium dendrite  , and also have excellent temperature stability and a wide stable electrochemical window that enables high voltage cathodes . Generally, solid electrolytes can be divided into inorganic solid electrolytes, solid polymer electrolytes and composite solid electrolytes  . In this review, we primarily discuss the classification of inorganic solid electrolytes, focusing on sulfide electrolytes . The study of ASSLIBs was started in the middle of the 20th century with the development of high-conductivity solid-state electrolytes . One of the most important properties of sold electrolytes is the lithium ionic conductivity. Ionic conduction in ceramic electrolytes is realized by movement of ions through vacancies or defects, thus 4 This article is protected by copyright. All rights reserved. Accepted Manuscript vehicles nowadays [1-3]. In particularly, the conventional LIBs with liquid electrolytes 10.1002/chem.201704568 Chemistry - A European Journal the ionic conductivities of electrolytes increase with temperature  . The ionic conductivities of sulfide inorganic electrolytes conform to the Arrhenius equation: ? = A exp (?Ea/kT), where Ea is the activation energy, T is the absolute temperature, k is the Boltzmann constant, and A is the pre-exponential factor  . To achieve fast ionic vacancies or defects for the mobile ions to occupy is larger than that of mobile species; (2) the barrier energies are lower than the transition energies from one site to another; (3) suitable size of mobile ions to fit the conduction channels; (4) the transition of ions can be connected to form a continuous diffusion pathway . To realize bulk-type ASSLIBs, solid electrolytes should have high lithium ionic conductivity at room temperature, low activation energy, stable wide electrochemical window, thermal stability without volume change, chemical stability versus anode and negligible electron conductivity . However, most of the existing solid electrolytes have not achieved the requirement of ionic conductivity for ASSLIBs , which is the main obstacle to limit their large-scale application. Recently, various attempts have been made to improve the ionic conductivities of sold electrolytes and some progress has been achieved. Sulfide inorganic compounds have been widely studied as solid electrolytes for ASSLIBs because they have higher ionic conductivities than other inorganic electrolytes at room temperature [11,18,19]. However, the most serious drawback of sulfide inorganic electrolytes is that their chemical stability is very poor in air . Sulfide electrolytes are sensitive to moisture and easy to react with the water contained in air, leading to generation of harmful H2S gas and destruction of electrolytes . The 5 This article is protected by copyright. All rights reserved. Accepted Manuscript conduction, the electrolyte should meet the following conditions: (1) the number of 10.1002/chem.201704568 Chemistry - A European Journal effective way to reduce H2S generation and improve chemical stability in air is to substitute oxides in electrolytes . The poor chemical stability strongly limits the application of sulfide electrolytes despite it can be improved by the substitution. An all-solid-state battery is comprised of cathode, anode and solid-state electrolyte,  . The solid electrolyte in ASSLIBs not only serves as lithium-ion conduction but also act as battery separator. Sulfide electrolytes are developed for ASSLIBs because of their high ionic conductivities and non-flammability  . In addition, sulfide inorganic electrolytes generally have a wide stable electrochemical window, which enables the ASSLIBs to be operated over a wide voltage range . Although the sulfide electrolytes have almost reached the demand of ASSLIBs, there are still many critical challenges to be overcome for large-scale application, including large interfacial resistance between electrolyte and electrodes, low ionic conductivity of electrode materials, volume change of cathodes during cycling and instability in contact with anodes [12, 26, 27]. Furthermore, the fabrication technology of ASSLIBs is under developing, and the interfacial contact during the assembly process is an extremely important factor for ASSLIBs. Therefore, suitable approaches of solving the issues mentioned above should be developed to achieve high-performance ASSLIBs. We shall discuss the current progress and potential of sulfide electrolytes in ASSLISs in detail. 6 This article is protected by copyright. All rights reserved. Accepted Manuscript as shown in Figure 1, and the compact structure leads to high energy density for battery 10.1002/chem.201704568 Chemistry - A European Journal Carbon Solid Electrolyte Figure 1. Schematic diagram of a typical bulk-type all-solid-state battery. 2. Sulfide solid electrolytes Inorganic solid electrolytes can be divided into oxide and sulfide electrolytes. Compared to oxide-based solid electrolytes, sulfide-based electrolytes have smaller binding force with Li ions due to the lower electronegativity and the ionic radius of S2? in sulfide-based electrolytes is larger than that of O2? in oxide-based electrolytes, leading the ionic migration channel of the former is larger than that of the latter [19, 29]. Therefore, sulfide electrolytes have higher ionic conductivities than oxide electrolytes. And the sulfide electrolyte shows small grain boundary resistance even in cold-pressed pellet, which is superior to oxide one . To date, sulfide solid electrolytes have been extensively studied for ASSLIBs and they have a high room temperature conductivity over 0.1~1 mS cm?1. Table 1 lists the ionic conductivities of existing sulfide electrolytes. Except the high ionic conductivity, sulfide electrolytes have several advantages, including wide electrochemical window, excellent thermal stability and good mechanical properties [30-35]. 7 This article is protected by copyright. All rights reserved. Accepted Manuscript Active Materials 10.1002/chem.201704568 Chemistry - A European Journal Structure Conductivity (25 癈 /mS cm?1) Reference Li7P3S11 Glass-ceramic 17  Li7P2S8I Crystal 0.63  Li6PS5Cl Crystal 0.7  70Li2S�P2S5 Glass-ceramic 3.2  70Li2S�P2S5�2S3 Glass-ceramic 5.4  70Li2S�P2S5�i3PO4 Glass-ceramic 1.87  75Li2S�P2S5�2O5 Glass-ceramic 0.8  Crystal 0.16  Li3.25P0.95S4 Glass-ceramic 1.3  Li9.6P3S12 Glass-ceramic 1.2  70Li2S�P2S5 Glass 0.054  75Li2S�P2S5 Glass 0.2  80Li2S�P2S5 Glass 0.17  Li10GeP2S12 Crystal 12  Li10.35Ge1.35P1.65S12 Crystal 14.2  Li3.25Ge0.25P0.75S4 Crystal 2.2  Li10SnP2S12 Crystal 4.0  Li10SiP2S12 Crystal 2.3  Li9.54Si1.74P1.44S11.7Cl0.3 Crystal 25  Composition Li3PS4 To data, sulfide electrolytes are usually synthesized by three methods, including melt-quenching [36, 52], mechanical ball-milling [53, 54] and liquid-phase method [55, 56]. Most of the sulfide electrolytes are prepared by mechanical ball-milling method and the ionic conductivity increases with the precipitation of crystalline phase by heattreatment. Eom et al. quantitatively examined the crystallization kinetics of mechanically milled 70Li2S�P2S5 glass to enhance the crystallinity of the solid 8 This article is protected by copyright. All rights reserved. Accepted Manuscript Table 1. Ionic conductivities of different sulfide solid electrolytes 10.1002/chem.201704568 Chemistry - A European Journal electrolyte and they found the enhancement in conductivity for the 78Li2S-22P2S5 glass-ceramics accomplished by using two-step heat treatment of 170 癈 for 30 min (nucleation stage) and 230 癈 for 3 h (crystal growth stage). As for the method of meltquenching, the preparation conditions are harsh and it is easy to produce impurities melt quenching technique under various melting conditions. The conductivity of the glass?ceramics was enhanced by the precipitation and growth of Li7P3S11 crystal. However, the Li7P3S11 crystal changed into the thermodynamically stable phase of low conductive Li4P2S6, with further increasing the heat treatment temperature and holding time. In addition, the liquid-phase method enables sufficient reaction of raw materials and produces homogenous precursor. And the ionic conductivities of solid electrolytes made by liquid-phase method are affected by the organic solvent  . Ito et al. synthesized a crystal phase of Li7P3S11 electrolyte by a liquid phase method using 1,2dimethoxyethane solvent. The impurity or amorphous phase easily formed at the grain boundaries, resulting in high activation energy and low ionic conductivity. Research into sulfide-type solid electrolyte started in 1986 with the Li2S-SiS2 system . In 2001, Kanno et al. first reported the crystalline thio-lithium conductor Li3.25Ge0.25P0.75S4 with an ionic conductivity of 2.2 mS cm?1. Li7P3S11 glass-ceramic was found in the Li2S-P2S5 system in 2005, which had high ambient temperature ionic conductivity of 3.2 mS cm?1 with low activation energy, greatly promoting the development of sulfide electrolytes . Recently, a new sulfide crystal Li10GeP2S12 was synthesized. It exhibited an extremely high lithium ionic conductivity of 12 mS cm ?1, 9 This article is protected by copyright. All rights reserved. Accepted Manuscript during the cooling process. Hayashi et al. prepared the 70Li2S�P2S5 glasses by a 10.1002/chem.201704568 Chemistry - A European Journal exceeding even those of liquid electrolytes . The Li10GeP2S12 electrolyte also showed high stability and wide potential window [60-62]. More recently, Kato et al. reported a lithium superionic conductor of Li9.54Si1.74P1.44S11.7Cl0.3 (Figure 2) with an exceptionally high conductivity of 25 mS cm?1. In addition, the ASSLISs based on electrochemical stability, exhibiting high power density and ultrafast charging performance. (b) (c) (a) Figure 2. (a) Arrhenius conductivity plots. (b) Crystal structure of Li9.54Si1.74P1.44S11.7Cl0.3. (c) Nuclear distributions of Li atoms in Li9.54Si1.74P1.44S11.7Cl0.3 at 25 癈. Despite much progress has been achieved, there are still fundamental problems in sulfide solid electrolyte: (1) low lithium ionic conductivities of most existing sulfide electrolytes; (2) poor chemical stability in air; (3) low electrochemical stability at electrolyte/electrode interface; (4) high cost of partial sulfide electrolytes. The ionic 10 This article is protected by copyright. All rights reserved. Accepted Manuscript Li9.54Si1.74P1.44S11.7Cl0.3 electrolyte possessed excellent ionic conductivity and 10.1002/chem.201704568 Chemistry - A European Journal conductivities of solid electrolytes can be enhanced by changing composition or optimizing preparation method. Huang et al. reported on a 70Li2S-30P2S5 system with substitution of Li3PO4. The glass-ceramics substituted with 1 mol % Li3PO4 exhibited the high conductivity of 1.87 mS cm?1 and enhanced its stability. Moreover, al. reported that the hot pressed Li7P3S11 showed high ionic conductivity of 17 mS cm?1 because of the reduced boundary resistance during heat treatment (Figure 3). As for the chemical stability of sulfide electrolytes, changing the component of electrolyte is an effective way. Ohtomo et al. prepared the Li2O-Li2S-P2S5 glass through the replacement of Li2S by Li2O, which was effectively in the suppression of H2S gas generation. The electrochemical stability at interface can be improved by anion doping in electrolytes. Rangasamy et al.  prepared Li7P2S8I from LiI and Li3PS4 that demonstrated high electrochemical stability with metallic lithium anode. To realize industrialization, the price of raw materials is an important factor. As for Li10GeP2S12, the cost of Ge is very high. Bron et al. reported the synthesis of Li10SnP2S12 instead of Li10GeP2S12, showing the ionic conductivity of 4 mS cm?1 and one-third of the cost for the Ge analogue. The Si could also replace the Ge atom and Li11Si2PS12 was recently reported with extremely high ionic conductivity . In a word, enhancing the ionic conductivities of solid electrolytes can be achieved by doping of the existing system or optimizing the preparation method. The stability can be improved by the addition of oxygen atoms or anion doping. The researchers now devote to find new solid electrolyte system with high stability/ionic conductivity and 11 This article is protected by copyright. All rights reserved. Accepted Manuscript the preparation method also greatly affects the property of solid electrolytes. Seino et 10.1002/chem.201704568 Chemistry - A European Journal (a) (c) (b) (d) Figure 3. SEM images of 70Li2S-30P2S5 glass-ceramic: (a) cold-pressed sample, (b) heat-treated sample at 280 癈, (c) Complex impedance plots for 70Li2S-30P2S5 glass-ceramic at ?35 癈, (d) after cold pressing and heat treatment at 280 癈. 3. Development of all-solid-state batteries A bulk-type ASSLIB is comprised of compressed cathode/anode and solid electrolyte layer. The electrolyte is the key component of ASSLIBs, which decides the migration of lithium ions in batteries. Generally, a cathode of ASSLIBs composes of active material, solid electrolyte and conductive additive, which form continuous lithium ion and electron conducting paths to active material to ensure both high ionic and electronic conductivities of the electrode. Because the sulfide electrolyte layer is easy to decrease grain-boundary resistance by conventional cold-press of electrolyte powders, the ASSLIBs can be assembled through simple fabrication processes. 3.1 Cathode 12 This article is protected by copyright. All rights reserved. Accepted Manuscript low cost. 10.1002/chem.201704568 Chemistry - A European Journal 3.1.1 Sulfur and lithium sulfide Lithium-sulfur batteries (LSBs) with a high theoretical energy density (2600 Wh Kg?1) are regarded as one of the most promising candidates to meet the growing application demands [65-70]. However, despite great progress, their extensive application effect leads to low active material utilization and poor cycling stability . Although new structures and technologies [72,73] have been explored, the shuttling problem is not fundamentally solved. Replacement of liquid electrolytes with solid electrolytes is an excellent solution [74-76]. Solid electrolytes can not only completely prevent polysulfide diffusion, but also block dendrite growth, resulting in high stability and safety [77-79]. In addition, sulfur is suitable to be employed as cathodes for ASSLSBs with sulfide inorganic electrolytes because sulfur is more compatible with the electrolytes than others. However, sulfur has poor electronic and ionic conductivities, which is unsatisfactory for the cathode of ASSLSBs [80, 81]. Therefore, sulfur incorporating with electronic conductive materials and solid electrolytes to form a composite cathode is a useful strategy to enable both high electronic and ionic conductivities. Nagao et al. developed sulfur-composite cathodes in ASSLSBs. The cathodes were prepared by mechanical milling of sulfur particles with acetylene black and Li2S-P2S5 glass-ceramic electrolyte at high temperature. Because of the large contact area among sulfur, acetylene black and solid electrolyte, the ASSLSBs fabricated using the composite electrodes exhibited excellent cycling stability (1050 mAh g?1 for 50 cycles) and good 13 This article is protected by copyright. All rights reserved. Accepted Manuscript is still restrained by the shuttle effect of soluble polysulfide intermediates. The shuttle 10.1002/chem.201704568 Chemistry - A European Journal rate capability. In addition, reducing the sulfur particle size is able to improve the contact area with electronic and ionic conductive materials. Nagao et al. found that a reduction in particle size of composite electrode materials could be controlled by mechanical milling. The small particles improved the contact among the electrode another problem that is the volume expansion. Because the contact at interface in ASSLSBs is solid-to-solid, the volume change during cycling easily leads to poor contact, resulting in fast capacity deterioration. Recently, Yao et al. reported a unique sulfur cathode fabricated by deposition on reduced graphene oxide (rGO) to improve the electronic conduction and reduce the stress/strain from volume change. The ASSLSBs with rGO/S cathode show a high initial discharge capacity of 1629 mAh g?1 at 0.05 C and excellent cycling stability (830 mAh g?1 after 750 cycles at 1 C) (Figure 4). They further investigated the reaction mechanism of sulfur electrode in ASSLSBs. Unlike the traditional liquid LSBs, ASSLSBs conforms the direct electrochemical reaction S + 2Li+ + 2e ? Li2S during the discharge process, without producing polysulfide intermediates through the analysis of CV curves. Lack of comparable system studies of the reaction mechanism in ASSLSBs, further work is needed to clarify. 14 This article is protected by copyright. All rights reserved. Accepted Manuscript components to enhancement of the capacities of ASSLSBs. Also, sulfur cathode has 10.1002/chem.201704568 Chemistry - A European Journal (a) (b) (d) (e) Figure 4. (a) Cyclic voltammogram of rGO@S-40 composite in all-solid-state cell at 60 癈. (b) Galvanostatic discharge/charge profiles for rGO@S-40 composite in all-solid-state cell at different rates at 60 癈. (c) Cycling performances of rGO@S-40 composites at 1.0 C and corresponding Coulombic efficiencies at 60 癈. Photograph of the Li?S full cells (d) before and (e) after 750 cycles at 1.0 C and 60 癈. Li2S is also regarded as a promising material for LSBs due to its high theoretical capacity of 1168 mAh g?1 without volume expansion. In addition, it can be used as an anode that does not have lithium sources . However, Li2S has low electronic and ionic conductivities same as sulfur. Han et al.  reported a novel bottom-up method to 15 This article is protected by copyright. All rights reserved. Accepted Manuscript (c) 10.1002/chem.201704568 Chemistry - A European Journal synthesize a nanocomposite by dissolving Li2S as the active material, polyvinylpyrrolidone (PVP) as the carbon precursor, and Li6PS5Cl as the solid electrolyte (Figure 5). The addition of carbon black and Li6PS5Cl in the cathode forms multiscale electronic/ionic conducting networks, thus the cathode delivers a high investigated the performance of ASSLSBs based on the small particle size of Li2S electrodes. Reducing the particles size was effective for improving their reversible capacity and rate performance. (a) (b) (c) Figure 5. (a) Schematic illustration of the bottom-up synthesis of the mixed conducting Li2S nanocomposite. (b) Cycling performances of Li2S?C and Li2S?Li6PS5Cl?C nanocomposite electrodes at 50 mA g?1. (c) Charge/discharge profiles of Li2S?Li6PS5Cl?C nanocomposite electrode at various current densities from 50 mA g?1 to 400 mA g?1. 16 This article is protected by copyright. All rights reserved. Accepted Manuscript reversible capacity (830 mAh g?1 for 60 cycles at 50 mA g?1). Nagao et al. 10.1002/chem.201704568 Chemistry - A European Journal In order to improve the performance of ASSLSBs based on sulfur or lithium sulfide, the effective ways are to combine electronic-conductive additive and ionic-conductive additive in cathodes, decrease the particle size of active materials, and build 3-D carbon 3.1.2 Metal sulfides Recently, metal sulfides have been attracted much attention in application of ASSLIBs because of their high electrochemical activity, excellent electronic conductivity, high theoretical capacities and mild operating voltages [87, 88]. Moreover, metal sulfides show superior compatibility combined with sulfide electrolytes and exhibit a highly reversible intercalation reaction with lithium. For example, the nanocomposite electrodes prepared by ball-milling of TiS2 and Li2S-P2S5 electrolyte for ASSLIBs exhibited a high initial discharge capacity of 840 mAh g?1 at 50 mA g?1, benefiting from the formation of an amorphous Li-Ti-P-S phase, size control of electrodes, and homogeneous distribution of solid electrolyte and TiS2 during the controlled ball-milling process . Chen et al. mixed MoS2 with Li6PS5Br and super P carbon to form a composite cathode. The resulting ASSLIBs displayed a capacity of 270 mAh g?1 up to 700 cycles at 0.2 C at 70 癈 with a high Coulombic efficiency. However, the large particle size of MoS2 is the limiting factor to enhance the reversible capacity. Recently, Co9S8 nanoparticles synthesized by a solution-based precipitation exhibited a capacity of 151 mAh g?1 at 0.38 mA?1 cm2 after 50 cycles . To improve cycling stability and rate performance, the Co9S8-Li7P3S11 nanocomposites were prepared by anchoring Li7P3S11 electrolyte particles on Co9S8 nanosheets. As a result, 17 This article is protected by copyright. All rights reserved. Accepted Manuscript structure to accommodate volume change. 10.1002/chem.201704568 Chemistry - A European Journal the ASSLIBs showed a high capacity of 421 mAh g?1 at 1.27 mA?1 cm2 after 1000 cycles. As mentioned above, metal sulfides have good electronic conductivity so that they do not need extra electronic-conductive additive in cathodes. The only problems for solid-electrolyte in cathode and designing suitable interfacial architecture can lead to advances in the development of ASSLIBs with metal sulfides. 3.2 Anode 3.2.1 Lithium metal Metallic lithium has an extremely high theoretical specific capacity of 3860 mAh g?1 and the lowest negative electrochemical potential. However, the metallic lithium is active and easy to form lithium dendritic, leading to the internal short circuits. Many works to form protective films on the surface of metallic lithium have been reported in liquid batteries [92-95] . Although the protective films restrain the growth of lithium dendritic, the security of batteries with lithium metal anodes is still very low. ASSLIBs with solid electrolytes can use lithium metal anodes directly, greatly improving their security and energy density. However, there are many chemical, electrochemical and mechanical stability issues at the interface between lithium metal and solid electrolyte. Certainly, the electrochemical stability of solid electrolyte can be affected by its composition. Tao et al. investigated the substitution of P2O5 for P2S5 in 70Li2S30P2S5 glass-ceramic. The 70Li2S-29P2S5-1P2O5 shows higher electrochemical stability than 70Li2S-30Li2S and it is completely compatible with metallic lithium, as 18 This article is protected by copyright. All rights reserved. Accepted Manuscript metal sulfides are the poor ionic conductivity and interface issue. Therefore, adding 10.1002/chem.201704568 Chemistry - A European Journal shown in Figure 6. Therefore the assembled ASSLIBs with 70Li2S-29P2S5-1P2O5 exhibited better electrochemical performances than those with the pristine electrolyte. Sun et al. reported the oxygen substitution effects in Li10GeP2S12 electrolytes. The partial substitution of oxygen for sulfur (Li10GeP2S12-xOx) not only improves the ionic metal electrodes in ASSLIBs, Kato et al. developed a modification method by depositing Au thin film between lithium metal and Li2S-P2S5 electrolyte. The insertion of Au film improved the utilization of lithium metal and ensured the stability of metallic lithium with sulfide electrolyte. 3.2.2 Lithium alloys Due to the instability of lithium with sulfide electrolytes, researchers use lithium alloys instead of lithium metal in ASSLIBs. Lithium alloys, such as Li-In , Li-Al , Li-Si  are good candidates for negative electrodes because of their high capacities and safety. Despite indium is included in the rare metal, Li-In is the most commonly used alloy because its potential is almost constant (0.62 V vs. Li/Li+) and the electrochemical reaction is reversible. Nagata et al. used Li-In alloy as anode in ASSLSBs and the molar ratio of Li-In is 0.79 . The cells showed a high initial capacity of 1096 mAh g?1 with excellent cycling stability in the voltage range of 0.5?2.5 V. Employing lithium alloys is an effective method to dramatically improve the interfacial stability between anodes and solid electrolytes. 19 This article is protected by copyright. All rights reserved. Accepted Manuscript conductivity but also enhances the electrochemical stability. To further protect lithium (a) (b) (c) (d) Figure 6. (a) Cyclability of 75Li2S-25P2S5 glass-ceramics. (b) Cyclability of 75Li2S-24P2S5- 1P2O5 glass-ceramics. (c) Charge-discharge curves and (d) Cycling performance of all-solid-state cell Li/75Li2S-(25-x) P2S5-xP2O5/LiCoO2 (x = 0% and 1%) at 25 癈. The interfacial stability between electrolytes and anodes is a significant factor to achieve high-performance ASSLIBs. Modifying the composition of solid electrolytes or employing lithium alloys as anodes are useful ways to enhance the stability of sulfide electrolyte versus lithium metal. 3.3 Interface 3.3.1 Interface phenomena Due to the solid-solid contact between electrode material and electrolyte, the large resistance exists at the interface, which limits the transport of lithium ions [102-105]. In addition, the stress/strain at interface dramatically increases because of volume change 20 This article is protected by copyright. All rights reserved. Accepted Manuscript 10.1002/chem.201704568 Chemistry - A European Journal 10.1002/chem.201704568 Chemistry - A European Journal of some electrodes during cycling, loose contact or interface separation occurs. As a result, the ASSLIBs show poor cycling stability or even become damaged. Recently, there are several methods developed to intimate the interfacial contact between electrode and electrolyte: (1) Reduce the particle sizes of active material and electrolyte; cathode; (4) Construct reasonable interfacial architecture. 3.3.2 Interface modification Modification of the interface between solid electrolyte and electrode can effectively imitate the interfacial contact and decrease the interfacial resistance. (1) As for the particle size, Hayashi et al. prepared nanosized NiS electrode via a mechanochemical reaction and the nanointerface was formed between the electrode and electrolyte. This method obtained a good solid-solid interface for fast transport of lithium ions due to the reduced size of NiS. The ASSLIBs with the nanocomposite electrode exhibit high capacity and good cycling stability. (2) ASSLIBs employed sulfide electrolytes are ordinarily assembled by cold-pressing. Although this method is very convenient, it still exists space at interface, resulting large interfacial resistance. Busche et al. reported that the interfacial resistance could be lowered considerably by hot-pressing during the preparation procedure of ASSLSBs. By introduction a hotpressing process, the grain boundary and interfacial resistance could be significantly reduced, enabling a continuous transport channel in batteries. The assembled ASSLSBs achieved a high sulfur utilization (1370 mAh g?1) in the first cycle and showed a good cycling stability. This study provides an effective method to reduce interfacial 21 This article is protected by copyright. All rights reserved. Accepted Manuscript (2) Introduce hot-pressing during preparation; (3) Add ionic-conductive materials in 10.1002/chem.201704568 Chemistry - A European Journal resistance and intimate the contact between sulfur cathode and electrolyte for the construction of high-performance ASSLSBs. (3) In addition, cathodes need to possess high contact area with electrolyte to arrive high utilization of active materials. Many electrodes have low ionic and electronic conductivities thus efforts have been done to solid electrolyte and carbon materials. Certainly, the way for mixing of solid electrolyte, carbon and active materials affects the combination of the three ingredients. Hakari et al. compared the electrochemical performance of composite electrodes prepared by hand grinding and ball milling. The electrode prepared by milling showed much higher performance than that by grinding, due to the intimate contact and the increase in lithium ion paths at interface. Now the strategy of mixing active materials, electronicconductive additive and solid electrolytes by ball milling has been widely applied in the preparation of cathodes for ASSLIBs. (4) Recently, interfacial architecture has been developed to further optimize interface. To achieve interface contact, the sulfide electrolyte is directly coated on the surface of active materials. Aso et al. reported that a highly conductive 80Li2S-20P2S5 electrolyte was coated on NiS-VGCF composite by pulsed laser deposition to form intimate solid-solid contacts between the cathode and electrolyte (Figure 7). The electrolyte coating gave the favorable lithium ion conduction paths in the working electrode. As a result, the SE-coated NiS-VGCF composite showed a high initial discharge capacity of 300 mAh g?1, and much better cycling stability than the counterpart without NiS-VGCF coating. 22 This article is protected by copyright. All rights reserved. Accepted Manuscript improve both the contact area and the ionic/electronic conductivity by incorporating (a) (b) (c) (d) Figure 7. (a) Schematic illustration of SE-coated NiS-VGCF composite. (b) Cycle performance of all-solid-state cell using uncoated or SE-coated NiS-VGCF composites. Charge?discharge curves of all-solid-state cell using (c) uncoated or (d) SE-coated NiS-VGCF composite. ASSLIBs with sulfide solid electrolytes are on their way toward achieving small interfacial resistance and high stability/compatibility. Present studies mainly focus on the contact modification between electrolyte and cathode by reducing particle size, introducing hot-pressing, adding ionic-conductive materials and construction reasonable interfacial architecture, which expand fundamental understanding and guide the design of ASSLIBs. As for the future research direction, more attention can be paid on the interface between electrolyte and anode and how to realize the ASSLIBs in largescale applications. 23 This article is protected by copyright. All rights reserved. Accepted Manuscript 10.1002/chem.201704568 Chemistry - A European Journal 10.1002/chem.201704568 Chemistry - A European Journal 4. Conclusions and perspectives To summarize, all-solid-state battery becomes a promising candidate for next generation of energy storage devices due to its improved safety, high energy density and wide operating temperatures. However, there still exist many challenges for conductivities and poor stability with lithium/air, and large interfacial resistance between cathodes and electrolytes, large volume change in electrodes for ASSLIBs during cycling. Many efforts have been done to improve ionic conductivities of electrolytes and overcome the problems mentioned above in ASSLIBs. (1) Enhancing the ionic conductivities of solid electrolytes can be achieved by doping of the existing system or finding new solid electrolytes; (2) Modifying the composition of solid electrolytes or employing lithium alloys as anodes can be improve stability of sulfide electrolytes versus lithium metal; (3) Overcoming the large interfacial resistance at solid/solid interface between electrodes and electrolyte is a huge challenge. It would be useful to solve the interface issues by reducing particle size, introducing hot-pressing, adding ionic-conductive materials and construction reasonable interfacial architecture; (4) Building 3-D construction of cathodes is an effective way to accommodate the volume change in electrodes and decrease stress/strain during cycling. It is necessary to ensure the imitate contact and chemical/electrochemical compatibility at solid-solid interface, and fast/continuous lithium ion transport in ASSLIBs in order to realize high utilization of active materials and excellent cycling stability. The research for future directions on the exploration of advanced ASSLIBs with 24 This article is protected by copyright. All rights reserved. Accepted Manuscript application of ASSLIBs employed sulfide inorganic electrolytes, such as low ionic 10.1002/chem.201704568 Chemistry - A European Journal sulfide electrolytes are as follows: (1) Synthesis of new sulfide electrolytes with improved ionic conductivities for meeting the requirements of application; (2) Enhancement of chemical stability of sulfide electrolytes in air in order to simplify production condition; (3) Improvement of the compatibility between solid electrolyte resistance; (5) Fabrication of novel composite cathodes with high ionic/electronic conductivities; (6) Modification Li metal anode to decrease the resistance; (7) Investigation of the electrochemical reaction mechanisms in ASSLIBs to guide the design of high-performance solid batteries; (8) Exploration of novel cell configuration design to further improve the energy density and realize high power density; (9) Optimization of the preparation/assembly process for all-solid-state batteries. As the most promising candidate for the energy storage devices, ASSLIBs provide advanced safety, high energy density and long cycling stability. The future developments of overcoming the challenges are expected to realize large-scale applications of ASSLIBs. Acknowledgements This work is supported by the National Natural Science Foundation of China (51271167) and the Program for Innovative Research Team in University of Ministry of Education of China (IRT13037). References  V. Etacheri, R. Marom, R. Elazari, G. Salitra, D. Aurbach, Energy Environ. Sci. 2011, 4, 3243. 25 This article is protected by copyright. All rights reserved. Accepted Manuscript and lithium metal; (4) Design of new interfacial architecture to reduce the interfacial 10.1002/chem.201704568 Chemistry - A European Journal  J. R. Szczech, S. Jin, Energy Environ. Sci. 2011, 4, 56-72.  D. Xie, X. H. Xia, Y. Zhong, Y. D. Wang, D. H. Wang, X. L. Wang, J. P. Tu, Adv.  J. W. Wen, Y. Yu, C. H. Chen, Mater. Express 2012, 2, 197-212.  X. Y. Yao, B. X. Huang, J. Y. Yin, G. Peng, Z. Huang, C. Gao, D. Liu, X. X. Xu, Chin. Phys. B 2016, 25, 018802.  L. Borchardt, M. Oschatz, S. Kaskel, Chem. Eur. J. 2016, 22, 7324-7351.  A. Hayashi, M. Tatsumisago, Electron. Mater. Lett. 2012, 8, 199-207.  W. D. Richards, L. J. Miara, Y. Wang, J. C. Kim, G. Ceder, Chem. Mater. 2016, 28, 266-273.  Z. C. Liu, W. J. Fu, E. A. Payzant, X. Yu, Z. L. Wu, N. J. Dudney, J. Kiggans, K. L. Hong, A. J. Rondinone, C. D. Liang, J. Am. Chem. Soc. 2013, 135, 975-978.  R. J. Chen, W. J. Qu, X. Guo, L. Li, F. Wu, Mater. Horiz. 2016, 3, 487-516.  M. Eom, J. Kim, S. Noh, D. Shin, J. Power Sources 2015, 284, 44-48.  K. Takada, Acta Mater. 2013, 61, 759-770.  J. W. Fergus, J. Power Sources 2010, 195, 4554-4569.  Z. Lin, Z. C. Liu, W. J. Fu, N. J. Dudney, C. D. Liang, Angew. Chem. Int. Ed. 2013, 52, 7460-7463.  A. Manthiram, X. W. Yu, S. F. Wang, Nat. Rev. Mater. 2017, 2, 16103.  F. D. Han, Y. Z. Zhu, X. F. He, Y. F. Mo, C. S. Wang, Adv. Energy Mater. 2016, 6, 1501590.  S. P. Ong, Y. Mo, W. D. Richards, L. Miara, H. S. Lee, G. Ceder, Energy Environ. 26 This article is protected by copyright. All rights reserved. Accepted Manuscript Energy Mater. 2017, 7, 1601804. 10.1002/chem.201704568 Chemistry - A European Journal Sci. 2013, 6, 148-156.  T. Hakari, M. Nagao, A. Hayashi, M. Tatsumisago, Solid State Ionics 2014, 262, 147-150.  J. Kim, Y. Yoon, J. Lee, D. Shin, J. Power Sources 2011, 196, 6920-6923.  H. Muramatsu, A. Hayashi, T. Ohtomo, S. Hama, M. Tatsumisago, Solid State Ionics 2011, 182, 116-119.  A. Hayashi, H. Muramatsu, T. Ohtomo, S. Hama, M. Tatsumisago, J. Alloys Compd. 2014, 591, 247-250.  Y. Kato, K. Kawamoto, R. Kanno, M. Hirayama, Electrochemistry 2012, 80, 749751.  J. Y. Yin, X. Y. Yao, G. Peng, J. Yang, Z. Huang, D. Liu, Y. C. Tao, X. X. Xu, Solid State Ionics 2015, 274, 8-11.  R. C. Xu, X. H. Xia, X. L. Wang, Y. Xia, J. P. Tu, J. Mater. Chem. A 2017, 5, 28292834.  H. Visbal, S. Fujiki, Y. Aihara, T. Watanabe, Y. Park, S. Doo, J. Power Sources 2014, 269, 396-402.  D. Y. Oh, Y. E. Choi, D. H. Kim, Y.-G. Lee, B.-S. Kim, J. Park, H. Sohn, Y. S. Jung, J. Mater. Chem. A 2016, 4, 10329-10335.  F. D. Han, T. Gao, Y. J. Zhu, K. J. Gaskell, C. S. Wang, Adv. Mater. 2015, 27, 3473-3483.  M. Tatsumisago, A. Hayashi, Int. J. Appl. Glass Sci. 2014, 5, 226-235. 27 This article is protected by copyright. All rights reserved. Accepted Manuscript  Y. S. Jung, D. Y. Oh, Y. J. Nam, K. H. Park, Isr. J. Chem. 2015, 55, 472-485. 10.1002/chem.201704568 Chemistry - A European Journal  R. C. Xu, X. H. Xia, S. H. Li, S. Z. Zhang, X. L. Wang, J. P. Tu, J. Mater. Chem. A 2017, 5, 6310-6317.  H. Yamane, M. Shibata, Y. Shimane, T. Junke, Y. Seino, S. Adams, K. Minami, A. Hayashi, M. Tatsumisago, Solid State Ionics 2007, 178, 1163-1167. Gasteiger, T. F. Faessler, Chem. Eur. J. 2016, 22, 17635-17645.  A. Hayashi, H. Muramatsu, T. Ohtomo, S. Hama, M. Tatsumisago, J. Mater. Chem. A 2013, 1, 6320-6326.  T. Ohtomo, A. Hayashi, M. Tatsumisago, Y. Tsuchida, S. Hama, K. Kawamoto, J. Power Sources 2013, 233, 231-235.  R. C. Xu, Z. Wu, S. Z. Zhang, X. L. Wang, Y. Xia, X. H. Xia, X. H. Huang, J. P. Tu, Chem. Eur. J. 2017, 23, 13950-13956  Y. Seino, T. Ota, K. Takada, A. Hayashi, M. Tatsumisago, Energy Environ. Sci. 2014, 7, 627-631.  E. Rangasamy, Z. C. Liu, M. Gobet, K. Pilar, G. Sahu, W. Zhou, H. Wu, S. Greenbaum, C. D. Liang, J. Am. Chem. Soc. 2015, 137, 1384-1387.  P. R. Rayavarapu, N. Sharma, V. K. Peterson, S. Adams, J. Solid State Electrochem. 2011, 16, 1807-1813.  F. Mizuno, A. Hayashi, K. Tadanaga, M. Tatsumisago, Adv. Mater. 2005, 17, 918921.  A. Hayashi, K. Minami, S. Ujiie, M. Tatsumisago, J. Non-Cryst. Solids 2010, 356, 2670-2673. 28 This article is protected by copyright. All rights reserved. Accepted Manuscript  L. Toffoletti, H. Kirchhain, J. Landesfeind, W. Klein, L. van Wuellen, H. A. 10.1002/chem.201704568 Chemistry - A European Journal  B. X. Huang, X. Y. Yao, Z. Huang, Y. B. Guan, Y. Jin, X. X. Xu, J. Power Sources 2015, 284, 206-211.  Y. C. Tao, S. J. Chen, D. Liu, G. Peng, X. Y. Yao, X. X. Xu, J. Electrochem. Soc. 2015, 163, A96-A101. 177, 2721-2725.  Y. Kato, S. Hori, T. Saito, K. Suzuki, M. Hirayama, A. Mitsui, M. Yonemura, H. Iba, R. Kanno, Nat. Energy 2016, 1, 16030.  M. Tatsumisago, Solid State Ionics 2004, 175, 13-18.  A. Hayashi, S. Hama, T. Minami, M. Tatsumisago, Electrochem. Commun. 2003, 5, 111-114.  N. Kamaya, K. Homma, Y. Yamakawa, M. Hirayama, R. Kanno, M. Yonemura, T. Kamiyama, Y. Kato, S. Hama, K. Kawamoto, A. Mitsui, Nat. Mater. 2011, 10, 682-686.  O. Kwon, M. Hirayama, K. Suzuki, Y. Kato, T. Saito, M. Yonemura, T. Kamiyama, R. Kanno, J. Mater. Chem. A 2015, 3, 438-446.  R. Kanno, M. Murayama, J. Electrochem. Soc. 2001, 148, A742-A746.  P. Bron, S. Johansson, K. Zick, J. Schmedt auf der Gunne, S. Dehnen, B. Roling, J. Am. Chem. Soc. 2013, 135, 15694-15697.  J. M. Whiteley, J. H. Woo, E. Hu, K. W. Nam, S. H. Lee, J. Electrochem. Soc. 2014, 161, A1812-A1817.  A. Hayashi, K. Minami, F. Mizuno, M. Tatsumisago, J. Mater. Sci. 2008, 43, 188529 This article is protected by copyright. All rights reserved. Accepted Manuscript  F. Mizuno, A. Hayashi, K. Tadanaga, M. Tatsumisago, Solid State Ionics 2006, 10.1002/chem.201704568 Chemistry - A European Journal 1889.  Y. Seino, M. Nakagawa, M. Senga, H. Higuchi, K. Takada, T. Sasaki, J. Mater. Chem. A 2015, 3, 2756-2761.  K. Ohara, A. Mitsui, M. Mori, Y. Onodera, S. Shiotani, Y. Koyama, Y. Orikasa, M. Sci. Rep. 2016, 6, 21302.  S. Teragawa, K. Aso, K. Tadanaga, A. Hayashi, M. Tatsumisago, J. Mater. Chem. A 2014, 2, 5095-5099.  S. Yubuchi, S. Teragawa, K. Aso, K. Tadanaga, A. Hayashi, M. Tatsumisago, J. Power Sources 2015, 293, 941-945.  R. C. Xu, X. H. Xia, Z. J. Yao, X. L. Wang, C. D. Gu, J. P. Tu, Electrochim. Acta 2016, 219, 235-240.  S. Ito, M. Nakakita, Y. Aihara, T. Uehara, N. Machida, J. Power Sources 2014, 271, 342-345.  J. H. Kennedy, Y. Yang, J. Electrochem. Soc. 1986, 133, 2437-2438.  Y. Mo, S. P. Ong, G. Ceder, Chem. Mater. 2012, 24, 15-17.  J. Hassoun, R. Verrelli, P. Reale, S. Panero, G. Mariotto, S. Greenbaum, B. Scrosati, J. Power Sources 2013, 229, 117-122.  C. H. Hu, Z. Q. Wang, Z. Y. Sun, C. Y. Ouyang, Chem. Phys. Lett. 2014, 591, 1620.  T. Ohtomo, A. Hayashi, M. Tatsumisago, K. Kawamoto, J. Non-Cryst. Solids 2013, 364, 57-61. 30 This article is protected by copyright. All rights reserved. Accepted Manuscript Murakami, K. Shimoda, K. Mori, T. Fukunaga, H. Arai, Y. Uchimoto, Z. Ogumi, 10.1002/chem.201704568 Chemistry - A European Journal  A. Kuhn, O. Gerbig, C. Zhu, F. Falkenberg, J. Maier, B. V. Lotsch, Phys. Chem. Chem. Phys. 2014, 16, 14669-14674.  W. Z. Bao, X. Q. Xie, J. Xu, X. Guo, J. J. Song, W. J. Wu, S. W. Su, G. X. Wang, Chem. Eur. J. 2017, 23, 12613-12619.  Y. M. Chen, X. Y. Li, K.-S. Park, J. H. Hong, J. Song, L. M. Zhou, Y.-W. Mai, H. T. Huang, J. B. Goodenough, J. Mater. Chem. A 2014, 2, 10126-10130.  D. H. Wang, X. H. Xia, Y. D. Wang, D. Xie, Y. Zhong, J. B. Wu, X. L. Wang, J. P. Tu, Chem. Eur. J. 2017, 23, 11169-11174.  X. Q. Zhang, D. Xie, Y. Zhong, D. H. Wang, J. B. Wu, X. L. Wang, X. H. Xia, C. D. Gu, J. P. Tu, Chem. Eur. J. 2017, 23, 10610-10615.  D. H. Wang, D. Xie, T. Yang, Y. Zhong, X.L. Wang, X. H. Xia, C. D. Gu, J. P. Tu, J. Power Sources 2016, 313, 233-239.  R. P. Fang, S. Y. Zhao, Z. H. Sun, D. W. Wang, H. M. Cheng, F. Li, Adv. Mater. 2017, 1606823.  A. Manthiram, S. H. Chung, C. Zu, Adv. Mater. 2015, 27, 1980-2006.  A. Rosenman, E. Markevich, G. Salitra, D. Aurbach, A. Garsuch, F. F. Chesneau, Adv. Energy Mater. 2015, 5, 1500212.  T. Kobayashi, Y. Imade, D. Shishihara, K. Homma, M. Nagao, R. Watanabe, T. Yokoi, A. Yamada, R. Kanno, T. Tatsumi, J. Power Sources 2008, 182, 621-625.  M. Agostini, Y. Aihara, T. Yamada, B. Scrosati, J. Hassoun, Solid State Ionics 2013, 244, 48-51. 31 This article is protected by copyright. All rights reserved. Accepted Manuscript  L. Borchardt, M. Oschatz S. Kaskel, Chem. Eur. J. 2016, 22, 7324-7351. 10.1002/chem.201704568 Chemistry - A European Journal  M. Chen, S. Adams, J. Solid State Electrochem. 2014, 19, 697-702.  J. E. Trevey, J. R. Gilsdorf, C. R. Stoldt, S. H. Lee, P. Liu, J. Electrochem. Soc. 2012, 159, A1019-A1022.  H. Nagata, Y. Chikusa, J. Power Sources 2014, 264, 206-210. Hassoun, B. Scrosati, J. Electrochem. Soc. 2015, 162, A646-A651.  N. Ding, S. W. Chien, T. S. A. Hor, Z. Liu, Y. Zong, J. Power Sources 2014, 269, 111-116.  F. D. Han, J. Yue, X. L. Fan, T. Gao, C. Luo, Z. H. Ma, L. M. Suo, C. S. Wang, Nano Lett. 2016, 16, 4521-4527.  M. Nagao, A. Hayashi, M. Tatsumisago, Energy Technol. 2013, 1, 186-192.  M. Nagao, A. Hayashi, M. Tatsumisago, Electrochim. Acta 2011, 56, 6055-6059.  X. Y. Yao, N. Huang, F. D. Han, Q. Zhang, H. L. Wan, J. P. Mwizerwa, C. S. Wang, X. X. Xu, Adv. Energy Mater. 2017, 7, 1602923.  T. Takeuchi, H. Kageyama, K. Nakanishi, T. Ohta, A. Sakuda, H. Sakaebe, H. Kobayashi, K. Tatsumi, Z. Ogumi, ECS Electrochem. Lett. 2014, 3, A31-A35.  M. Nagao, A. Hayashi, M. Tatsumisago, J. Mater. Chem. 2012, 22, 10015-10020.  D. Xie, X. H. Xia, Y. D. Wang, D. H. Wang, Y. Zhong, W. J. Tang, X. L. Wang, J. P. Tu, J. Chem. Eur. J. 2016, 22, 11617-11623.  Y. Nishio, H. Kitaura, A. Hayashi, M. Tatsumisago, J. Power Sources 2009, 189, 629-632.  B. R. Shin, Y. J. Nam, J. W. Kim, Y. G. Lee, Y. S. Jung, Sci. Rep. 2014, 4, 5572. 32 This article is protected by copyright. All rights reserved. Accepted Manuscript  T. Yamada, S. Ito, R. Omoda, T. Watanabe, Y. Aihara, M. Agostini, U. Ulissi, J. 10.1002/chem.201704568 Chemistry - A European Journal  M. H. Chen, X. S. Yin, M. V. Reddy, S. Adams, J. Mater. Chem. A 2015, 3, 1069810702.  X. Y. Yao, D. Liu, C. S. Wang, P. Long, G. Peng, Y. S. Hu, H. Li, L. Q. Chen, X. X. Xu, Nano Lett. 2016, 16, 7148-7154. Y. J. Zhang, W. Q. Bai, X. L. Wang, X. H. Xia, C. D. Gu, J. P. Tu, J. Mater. Chem. A 2016, 4, 15597-15604.  Y. J. Zhang, W. Wang, H. Tang, W. Q. Bai, X. Ge, X. L. Wang, C. D. Gu, J. P. Tu, J. Power Sources 2015, 277, 304-311  B. Zhu, Y. Jin, X. Z. Hu, Q. H. Zheng, S. Zhang, Q. J. Wang, J. Zhu, Adv. Mater. 2017, 29, 1603755.  Y. J. Zhang, X. Y. Liu, W. Q. Bai, H. Tang, S.J. Shi, X. L. Wang, C. D. Gu, J. P. Tu, J. Power Sources 2014, 266, 43-50.  Y. Sun, K. Suzuki, K. Hara, S. Hori, T.-A. Yano, M. Hara, M. Hirayama, R. Kanno, J. Power Sources 2016, 324, 798-803.  A. Kato, A. Hayashi, M. Tatsumisago, J. Power Sources 2016, 309, 27-32.  H. Nagata, Y. Chikusa, J. Power Sources 2014, 263, 141-144.  M. Nagao, Y. Imade, H. Narisawa, T. Kobayashi, R. Watanabe, T. Yokoi, T. Tatsumi, R. Kanno, J. Power Sources 2013, 222, 237-242.  S. Kinoshita, K. Okuda, N. Machida, M. Naito, T. Sigematsu, Solid State Ionics 2014, 256, 97-102.  K. Takada, N. Aotani, K. Iwamoto, S. Kondo, Solid State Ionics 1996, 86, 877882. 33 This article is protected by copyright. All rights reserved. Accepted Manuscript  10.1002/chem.201704568 Chemistry - A European Journal  N. Ohta, K. Takada, I. Sakaguchi, L. Zhang, R. Ma, K. Fukuda, M. Osada, T. Sasaki, Electrochem. Commun. 2007, 9, 1486-1490.  Z. Bai, N. Fan, C. Sun, Z. Ju, C. Guo, J. Yang, Y. Qian, Nanoscale 2013, 5, 24422447.  Z. Bai, N. Fan, Z. Ju, C. Guo, Y. Qian, B. Tang, S. Xiong, J. Mater. Chem.A 2013, 1, 10985.  A. Hayashi, Y. Nishio, H. Kitaura, M. Tatsumisago, Electrochem. Commun. 2008, 10, 1860-1863.  M. R. Busche, D. A. Weber, Y. Schneider, C. Dietrich, S. Wenzel, T. Leichtweiss, D. Schr鰀er, W. Zhang, H. Weigand, D. Walter, S. J. Sedlmaier, D. Houtarde, L. F. Nazar, J. Janek, Chem. Mater. 2016, 28, 6152-6165.  T. Hakari, M. Nagao, A. Hayashi, M. Tatsumisago, J. Power Sources 2015, 293, 721-725.  K. Aso, A. Sakuda, A. Hayashi, M. Tatsumisago, ACS Appl. Mater. Interfaces 2013, 5, 686-690. 34 This article is protected by copyright. All rights reserved. Accepted Manuscript  Z. Bai, Z. Ju, C. Guo, Y. Qian, B. Tang, S. Xiong, Nanoscale 2014, 6, 3268-3273.