A new class of sulfide electrolytes, (1-x)LiCl-xLiBr-2Li(3)PS(4)(x = 0, 0.25, 0.50, 0.75, and 1.0), was synthesized, and characterized their stable temperature range, ionic-conductivity and applicability for all-solid-state lithium metal battery. The optimal heat-treatment temperature of the synthesis process is relatively low, i.e., 200?. Ionic conductivity of the electrolyte increases with increasing LiBr ratio, and maximum ionic conductivity at 25 ? is 1.7 mScm(-1) with x = 0.75. At higher heat-treatment temperature, above 250 ?, a low-ionic-conduction crystalline phase appears in the electrolyte, and at that time, ionic conductivity decreases to a similar value to that of the amorphous precursor used in the synthesis process. Since the electrolyte does not contain a transition metal, it is applicable to the lithium-metal secondary system. A reversible lithium deposition-stripping reaction was demonstrated by cyclic voltammogram, the results of which indicate that the electrolyte is applicable to a typical 4-V rechargeable lithium-metal secondary system. The Coulombic efficiency of the first charge-discharge cycle is approximately 75%, and reversible capacity of 185 mAhg(-1) was verified by a Li/0.25LiCl-0.75LiBr2Li3PS4/NCA pelletized-cell test. It is concluded from these results that the proposed low-temperature synthesized sulfide electrolytes will reduce energy consumption for material production, and such a low carbon-footprint process meets the demand of the future sustainable society.

A study on the interfacial properties between a solid glassy electrolyte, LiI-Li3PS4 (LPSI), and graphite (MAG) composite electrodes was carried out with the aim of reducing or even eliminating the irreversible capacity during the 1(st) charge-discharge cycle. The performances of all-solid-state MAG|LPSI|Li cells were compared with those of conventional liquid cells. To reinforce a well-distributed conductive path in MAG as well as at the MAG/LPSI interface, the type of electron conducting additive and the pressure during cell preparation were optimized. Specific functions of the conducting additive were demonstrated, where the sub-micrometric carbon fibers allowed better galvanostatic performance in the solid-state configuration by virtue of their high aspect ratio. The coulombic efficiency of solid-state cells was improved from 46 to 99 % and the reversible capacity value from 100 to 270 mAh g(-1), by increasing the pressure from 2 to 4 ton. The interfacial stability of LPSI was also evaluated by impedance spectroscopy of MAG|MAG and Li|Li cells over time. Although ionic resistance of LPSI was higher than a conventional liquid electrolyte, LPSI exhibited controlled interfacial resistance.

Inorganic solid electrolytes (ISEs) gain tremendous attention during the past decade for application in energy storage. Among different classes of ISEs, sulfides are particularly appealing due to their higher ionic conductivity, ductility, and lower density compared with oxides. However, most of the preparation methods proposed so far require either the time‐consuming mechanical ball‐milling process or the energy‐consuming high‐temperature solid‐state reaction. Herein, a new and fast liquid‐assisted approach to synthesize LiI‐doped glassy Li 2 S‐P 2 S 5 (LPS) with excellent electrochemical and morphological features is reported. The obtained solid electrolyte offers an ionic conductivity of 1.2 mS cm −1 at room temperature and establishes a rather stable interphase with lithium. These enable rather high critical current densities (up to 1 mA cm −2 ), as well as enhanced cathode active material utilization in solid‐state lithium metal cells.

The interfacial instability between a thiophosphate solid electrolyte and oxide cathodes results in rapid capacity fade and has driven the need for cathode coatings. In this work, the stability, evolution, and performance of uncoated, Li 2 ZrO 3 -coated, and Li 3 B 11 O 18 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathodes are compared using first-principles computations and electron microscopy characterization. Li 3 B 11 O 18 is identified as a superior coating that exhibits excellent oxidation/chemical stability, leading to substantially improved performance over cells with Li 2 ZrO 3 -coated or uncoated cathodes. The chemical and structural origin of the different performance is interpreted using different microscopy techniques which enable the direct observation of the phase decomposition of the Li 2 ZrO 3 coating. It is observed that Li is already extracted from the Li 2 ZrO 3 in the first charge, leading to the formation of ZrO 2 nanocrystallites with loss of protection of the cathode. After 50 cycles separated (Co, Ni)-sulfides and Mn-sulfides can be observed within the Li 2 ZrO 3 -coated material. This work illustrates the severity of the interfacial reactions between a thiophosphate electrolyte and oxide cathode and shows the importance of using coating materials that are absolutely stable at high voltage.

All-solid-state lithium-ion batteries are promising candidates to overcome safety and energy limitations of common lithium-ion batteries. Although excellent results have been reported for sulfide based electrolytes on a small scale, classical slurry-based lithium-ion processing fails to reproduce the same performance in a larger cell. In this study, a dry-film (DF) process is presented that replaces slurry based binders by a fibrous PTFE binder and reduces the binder amount to an absolute minimum as low as 0.1 wt%, which is the lowest reported value so far. Freestanding NCM sheets with a high areal loading of 6.5 mAh cm(-2) were prepared showing even at room temperature the same rate performance like binder-free electrodes with 2.5 mAh cm(-2). The impact of binder content on cell performance has been studied revealing significantly reduced impedance at contents below 0.7 wt%. To realize a practical cell, the cell composition was optimized and a 9 cm(2) sized rocking-chair type all-solid-state battery was prepared without any solvents underlining the sustainability of the DF process. The battery was cycled for 100 cycles without any artificial pressure, demonstrating the versatility and potential of the DF process.

Accompanying the recent technological advance, sulfide-based all-solid-state Li ion battery (ASSB) is anticipated to reach to the stage of commercialization within 10 years. In particular, significant progress has been made within the last five years with the discoveries of several sulfide-based compounds whose conductivity is greater than 10 mS/cm, such as Li10GeP2S12 [1], Li7P3S11 [2], and Li9.54Si1.74P1.44S11.7Cl0.3[3]. Usually such new Li-ion conductive materials have been discovered through engineering manners, such as changing the composition of a known superionic compound, or adjusting the synthesis conditions. Recently, however, there have been other attempts to predict new SE materials by means of a computational approach using first-principles calculations. W. Richards et al. [4] predicted that Na10SnP2S12, in which Li is substituted to Na in Li10SnP2S12, would be a good Na ion conductor. They also synthesized Na10SnP2S12 in practice and confirmed that the experimentally measured ionic conductivity and the activation energy of Na10SnP2S12 agreed well with those of the predicted values. In this study, we examined I-4 type Li1+2xZn1-xPS4 — a new Li ionic conductor computationally predicted by Richards et al. [5-6]. They predicted that the stoichiometric LiZnPS4 is almost insulative, but non-stoichiometric compound of Li1+2xZn1-xPS4 can show superionic conductivity with the predicted room temperature ionic conductivity (σ25 ℃) as large as 50 mS/cm at x=0.5. Li1+2xZn1-xPS4 was synthesized by using solid state reaction. We ball-milled the starting materials and heated it at elevated temperature under vacuum. We measured the XRD patterns and the Raman spectra for Li1+2xZn1-xPS4 at various x and confirmed that the samples with x ≤ 0.625 have I-4 structure with little impurities. Figure 1 shows the ionic conductivity at 25℃ (σ25 ℃) and the activation energy (Ea) for Li1+2xZn1-xPS4 at various x. Li1+2xZn1-xPS4 shows negligible conductivity when x ≤ 0.2. At x = 0.375, σ25 ℃ starts increasing and Ea starts decreasing. The highest σ25 ℃ achieved was 5.7 x 10-4 S/cm at x = 0.625. This tendency qualitatively agrees with the theoretical predictions [6], but there remains a considerable amount of discrepancy. When x ≥ 0.75, σ25 ℃ decreases, which likely corresponds to low phase purity and poor crystallinity of the material. We also examined the feasibility of Li2.25Zn0.375PS4(x=0.625) in a practical ASSB with NCM cathode and various anodes (graphite, indium, LTO), and found that this material was not stable with graphite and indium, but can be paired with NCM and LTO. References [1] N. Kamaya, K. Homma, Y. Yamakawa, M. Hirayama, R. Kanno, M. Yonemura, T. Kamiyama, Y. Kato, S. Hama, K. Kawamoto and A. Mitsui, Nature Materials, 10 (2011), 682. [2] Y. Seino, T. Ota, K. Takada, A. Hayashi and M. Tatsumisago, Energy & Environmental Sciences, 7 (2014) 627. [3] Y. Kato, S. Hori, T. Saito, K. Suzuki, M. Hirayama, A. Mitsui, M. Yonemura, H. Iba, R. Kanno, Nature Energy, 1 (2016) 16030. [4] W. Richards, T. Tsujimura, L. Miara, Y. Wang, J. Kim, S. Ong, I. Uechi, N. Suzuki and G. Ceder, Nature Communications, 7 (2016) 11009. [5] Y. Wang, W. D. Richards, S. P. Ong, L. J. Miara, J. C. Kim, Y. Mo and G. Ceder, Nature Materials, (2015), 14, 1026. [6] W. Richards, Y. Wang, L. Miara, J. Kim and G. Ceder, Energy and Environmental Sciences, 9 (2016) 3272. Figure 1. σ25℃ and Ea for Li1+2xZn1-xPS4.

Introduction Li-ion solid electrolytes have been attracted great interest to researchers, because it could potentially replace conventional organic liquid or gel electrolytes, which are not desirable for the next generation Li-ion battery because of their flammable property. Recently, some Li-ion solid electrolytes whose conductivities exceed 10mS/cm, were reported, e.g., LGPS (Li10GeP2S12) crystal with 12mS/cm [1] and Li7P3S11 glass ceramics synthesized using hot-press with 17mS/cm [2]. Despite their excellent conductivities, however, these materials are not suitable in use with Li anode because they are not stable against Li metal. Li-ion conductive glass or glass ceramics with high ionic conductivity without reaction with Li metal are eagerly desired. Recently, Li-argyrodite, whose structure is an analogue of chalcogenide such as the mineral Ag8GeS6, were reported. Rayavarapu et al. [3] revealed the high ionic conductivity of the order of 10-4 S/cm for the crystalline Li6PS5X (X=Cl, Br), which is brought by the disorder of lithium and S2-/Cl- or S2-/Br-. Besides degree of disorder in crystals, the lattice volume is one of the most important parameter. In this study, we tried adding small amount of Na+ ions to expand the lattice volume of the Li-argyrodite and examined its ionic conductive property. Experiments We prepared the argyrodite-type glass ceramics of (Li 5.75-xNax)PS4.75Cl1.25 as a solid electrolyte using a high-energy ball-milling process. Desired amounts of Li2S, Na2S, LiCl and P2S5 were weighed and mixed in an agate mortar for about 20 min. High-energy ball milling was conducted by using a planetary ball-milling apparatus for 16.5h and the rotation speed was 380 rpm. The ball-milled powder was sealed in a quartz tube under vacuum and heated in various conditions. After heating, the quartz tube was slowly cooled down to room temperature. The obtained samples were characterized by means of X-ray diffraction (XRD) with Cu-Kα radiation. Simulation of the XRD data was performed using Rietveld crystal structure refinement software (Highscore plus). Electrochemical impedance (EIS) was measured using an AUTOLAB PGSTAT30 (Metrohm Autolab, Utrecht) controlled by a personal computer. Approximately 200 mg of the electrolyte powder was measured by a micro-balance, and we prepared the sample pellet by pressing at 3 tons with a die with a diameter of 13mm. Indium foils were attached to the both side of the pellets to use them as the blocking electrodes, and contained in a SUS cell. We put the cell in an incubator ESPEC TH-241 (Espec, Osaka), and measured the EIS with an amplitude of 10 mV in a frequency range of 1MHz-100mHz at 30 ºC under a normal pressure. The cyclic voltammetry (CV) was measured with a Li/ (Li 5.75-xNax)PS4.75Cl1.25/SUS cell , where Li electrode was used either as the counter or the reference electrode and the scan range between -0.5 and 5V. Results and Discussion The XRD patterns of the (Li5.75-xNax)PS4.75Cl1.25 synthesized in the present study show that the main phases appearing in the patterns were indexed by the tetragonal crystal structure of argyrodite in space group F4-3m. Additional peaks are observed for the samples whose Na substitution levels are relatively high, i.e., x is large in (Li5.75-xNax)PS4.75Cl1.25. These peaks were indexed by the LiCl and Li2S phases. A continuous peak shift attributed to the argyrodite suggests the formation of the solid solutions with the composition 05.75-xNax)PS4.75Cl1.25 . With increasing x value, the lattice volume of the argyrodite expands systematically. The conductivity continuously increased as the Na content increased from x = 0.0 (σ = 2.2 mS/cm) to x = 0.03 (σ = 5.6 mS/cm) in (Li5.75-xNax)PS4.75Cl1.25. In a higher Na content above x=0.03, however, the conductivity continuously decreased. The lattice volume of the argyrodite increases systematically with increasing x value, but the amounts of LiCl and Li2S also increases. In the CV, we observed solely cathodic and anodic currents corresponding to lithium deposition and dissolution. No significant currents due to the electrolyte decomposition or the redox reaction of Na+/Na were observed between -0.5 and 5V, indicating that this material is stable against Li metal and that the Na+does not contribute to the ionic current. References [1] Kamaya N. et al., Nature Mater. 10, 682-686 (2011) [2] Seino Y., et al., Energy Environ. Sci. 7, 627-631 (2014) [3] Rayavarapu P. R. et al., J. Solid State Electrochem. 16, 1807-1813 (2012) Figure 1

Sodium-ion batteries are emerging as candidates for large-scale energy storage due to their low cost and the wide variety of cathode materials available. As battery size and adoption in critical applications increases, safety concerns are resurfacing due to the inherent flammability of organic electrolytes currently in use in both lithium and sodium battery chemistries. Development of solid-state batteries with ionic electrolytes eliminates this concern, while also allowing novel device architectures and potentially improving cycle life. Here we report the computation-assisted discovery and synthesis of a high-performance solid-state electrolyte material: Na 10 SnP 2 S 12 , with room temperature ionic conductivity of 0.4 mS cm −1 rivalling the conductivity of the best sodium sulfide solid electrolytes to date. We also computationally investigate the variants of this compound where tin is substituted by germanium or silicon and find that the latter may achieve even higher conductivity.

The structural characterization for Na+ Super Ionic Conductor (NASICON)-type glass ceramics of 20R2O–XZrO2–15P2O5–(65-X)SiO2 (R = Na, Li) was investigated by X-ray diffraction (XRD) and X-ray absorption fine structure to clarify the better conductive mechanism of Li-glass ceramics than that of Na-glass ceramics. The Na-glass ceramics were synthesized by heat treatment using glass material, and the Li-glass ceramics were obtained through ion exchange techniques from Na-glass ceramics. From the XRD analysis, the positive correlation between ionic conductivity and lattice parameter was identified for the Na-glass ceramics, on the other hand, there was no positive relation for Li-glass ceramics, indicating that the ion conductive mechanism cannot be explained by the lattice parameter of NASICON crystalline phase alone. The Debye–Waller factors related to the oxygen surrounding the Zr-ion for the Li-glass ceramics were higher than those for the Na-glass ceramics. The static disorder around Zr-ion may cause more weakly bonding between the Li ions and surrounding atoms, resulting in the improvement of ionic conductivity.

The effect of water on the internal friction of SiO2–Al2O3–Na2O–MgO glasses with water content up to 0.070mol/l was determined. For (74−x)SiO2–xAl2O3–(26−y)Na2O–yMgO glasses in which 0≦x≦3 and 0≦y≦16, the low temperature friction peak below 200°C caused by the stress-induced movement of sodium ion shifts to higher temperature, and its activation energy becomes larger with increasing water content. This result suggests that the low temperature motion of Na+ ion (γ relaxation) becomes slower by addition of water. For 69SiO2–5Al2O3–13Na2O–13MgO glass, however, adding water enhanced sodium ion movement since aluminate tetrahedral became charge balanced by H+ instead of Na+ cation, thereby inducing γ relaxation.

The surface of LiNi0.8Co0.15Al0.05O2 (NCA) cathode material was coated with diamond like carbon (DLC) by chemical vapor deposition method, in order to prevent the side reaction at the interface for sulfide based all-solid state lithium-ion batteries. The DLC coated material showed a higher capacity with good cyclability and high rate performance. The interface resistance between the cathode active material and the solid electrolyte significantly decreases by DLC coating onto the NCA powder. The discharge capacity of DLC coated sample at 0.05C was 113 mAhg−1 while that of bared one was about 102 mAhg−1. The charge and discharge cut off potentials were 4.0 and 2.8 V, respectively. The thickness of the DLC coated layer was verified by transmission electron microscope (TEM), and was about 3`5 nm. The sp2 bonding ratio of the DLC coated LiNi0.8Co0.15Al0.05O2 powder was estimated from the C-KELNES spectra to be 50`55%. DLC coating could avoid formation of an inactive layer when surface impurities of NCA react with the sulfide electrolyte to form at irreversible passivation byproduct. This layer of impurities obstructs the Li-ion transport at the interface, and therefore increases the interfacial resistance and decreases the rate capability for bare samples. In this work, the diamond like carbon (DLC) coating were proposed for the first time as buffer coating layers for all-solid state battery. We demonstrated that the buffer layer is not needed to have a lithium conductivity to reduce the interface resistance between cathode material and sulfide based electrolyte.

Ion exchange of LiNO3 molten salt into Na2O-ZrO2-P2O5-SiO2 glass ceramics was successfully performed in order to obtain Li-exchanged Na+ superionic conductor (NASICON) -type glass ceramics. This procedure was carried out to stabilize the Li-ion-exchanged NASICON-type crystals in a system composed of Li2O-ZrO2-P2O5-SiO2. The total conductivity of the prepared system increased as the X value in the 20Li(2)O-XZrO2-15P(2)O(5)-(65-X) SiO2 system increased, reaching a maximum conductivity value of 3.0 (+/- 2.0) x 10(-4) S/cm (X = 30). The conductivity was affected by the existence of the Li3PO4 phase, which was present in the Li-exchanged glass ceramics. (C) 2013 Elsevier B.V. All rights reserved.