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To overcome the challenges associated with the toxicity of the majority of organic solvents for the liquid phase synthesis of solid electrolytes toward the human body and environment, we demonstrate the synthesis of tin-based sulphide electrolytes using water, which is the most environmentally friendly solvent. ortho-Thiostannate, i.e., Li4SnS4, was obtained from a mixture of Li2S, Sn, and S using aqueous solution synthesis. Furthermore, Li10SnP2S12, a superionic conductor, was obtained by mixing an aqueous solution of Li4SnS4 and tetrahydrofuran suspension of Li3PS4, which exhibited the highest ionic conductivity (5.9 × 10−3 S cm−1 at 25 °C) in liquid-phase synthesis. This study successfully demonstrates that water can be efficiently used to synthesize sulphide electrolytes instead of conventional organic solvents. [ABSTRACT FROM AUTHOR]

Highly safe all-solid-state batteries are constructed using oxide electrolytes because of their high chemical and electrochemical stabilities. Previously, we have developed various Li 3 BO 3 -based glass-ceramic electrolytes with high ductility and conductivity. In this study, we focus on the importance of electrode/electrolyte interfacial contacts in all-solid-state batteries. All-oxide solid-state cells (Li-In/LiNi 1/3 Mn 1/3 Co 1/3 O 2) with Li 3 BO 3 -based glass-ceramic electrolytes, are fabricated simply by pressing at room temperature. Furthermore, the effects of the ductility and ionic conductivity of glass-ceramic electrolytes on the charge-discharge properties of all-solid-state batteries are investigated. The 33Li 3 BO 3 ·33Li 2 SO 4 ·33Li 2 CO 3 (mol%) glass-ceramic electrolyte shows lower ionic conductivity and better ductility than the 90Li 3 BO 3 ·10Li 2 SO 4 electrolyte. The all-solid-state cells using these electrolytes operate as secondary batteries at 100 °C. However, better cycle performance is obtained with cells using the former electrolyte. Formation of well-contacted electrode/electrolyte interfaces when using highly ductile electrolytes leads to enhanced electrochemical performance of bulk-type all-solid-state batteries. • All-solid-state cells using Li 3 BO 3 -based glass-ceramic electrolytes are fabricated. • The cell with highly ductile electrolyte shows better charge-discharge performance. • Electrode-electrolyte interfacial formation is important for good cyclability. [ABSTRACT FROM AUTHOR]

Composite graphite negative electrodes were prepared by mixing graphite particles and 75Li 2 S·25P 2 S 5 (mol%) glass particles with weight ratios of x :100 −  x ( x  = 50, 60 and 70). The cell with the x  = 50 electrode showed the highest reversible capacity of more than 250 mAh g −1 . Optical microscopy was conducted for each composite electrode after electrochemical lithiation to investigate reaction distributions by color changes of graphite particles. In the x  = 50 electrodes, almost all the graphite particles changed to gold color, suggesting that the graphite particles were fully lithiated. In situ optical microscopy was also carried out for the composite graphite electrode to monitor color changes of graphite particles directly during charge-discharge tests. [ABSTRACT FROM AUTHOR]

Among transition metal sulfides, VS 4 is a promising candidate material for the positive electrode in rechargeable Li/metal-sulfide batteries, due to its long, flat plateau at about 2.0 V and its high theoretical capacity (1195 mAh g −1 ). In this study, we prepared VS 4 positive electrode material by heating in a sealed tube, and studied local structural changes during charge/discharge cycles via X-ray absorption and scattering spectroscopies, focusing on the reversibility of VS 4 . The findings reveal that a VS 4 -like local structure was formed in the first cycle, and that subsequent cycles showed reversible changes. [ABSTRACT FROM AUTHOR]

The effect of the particle sizes of LiNi 1/3 Co 1/3 Mn 1/3 O 2 and Li 2 S–P 2 S 5 solid electrolytes (SEs) on the electrode morphology was investigated. Smaller-sized SE particles were advantageous in fabricating dense and homogeneous electrode layers with an effective lithium-ion conduction pathway and a large electrode–electrolyte interfacial contact area because of the unique mechanical properties of sulfide-based SEs. The homogeneous distribution of the SE is also effective in the suppression of cracking and fracturing of LiNi 1/3 Co 1/3 Mn 1/3 O 2 because of the favorable mechanical properties of the sulfide-based SEs. The capacity of the all-solid-state cells under high-rate operation was thus remarkably improved. [ABSTRACT FROM AUTHOR]

Abstract: Composite electrodes composed of amorphous titanium polysulfide (a-TiSx) and titanium disulfide (TiS2) were designed for application in all-solid-state batteries. The conductivity of the a-TiSx/TiS2-based working electrode was higher than that of the amorphous TiS4 (a-TiS4); the reversible capacity of the cell using a-TiSx/TiS2 electrode was higher than that of the cell using a-TiS4. Designing nanocomposite materials such as the a-TiS x /TiS2 described in this paper is an effective way to improve the performance of all-solid-state batteries. [Copyright &y& Elsevier]

(100 − x)(0.75Li2S·0.25P2S5)·xLiBH4 (0 ≤ x (mol%) ≤ 33) glass electrolytes were prepared from 75Li2S·25P2S5 (mol%) glass and LiBH4 crystal by a mechanical milling technique. The effects of the addition of LiBH4 on the structures and properties of the glass electrolytes were examined. The DSC curves of the prepared glasses with LiBH4 did not have the endothermic peak attributable to the phase transition of LiBH4 crystal. The Raman spectra of the glasses indicated that the glasses included PS4 3− and BH4 − ions. The conductivities of the glasses increased with increasing the LiBH4 content. The glass at the composition of x = 33 showed the highest lithium-ion conductivity of 1.6 × 10−3 S cm−1 at room temperature. The glass had a wide electrochemical window up to 5 V vs. Li+/Li. An all-solid-state Li/TiS2 cell using the glass as an electrolyte successfully operated as a secondary battery at 25 °C. [ABSTRACT FROM AUTHOR]

Amorphous titanium trisulfide (TiS) active materials were prepared by ball milling of an equimolar mixture of crystalline titanium disulfide (TiS) and sulfur. A high-resolution transmission electron microscope image revealed no periodic lattice fringes on the amorphous TiS. The all-solid-state lithium secondary batteries using a sulfide solid electrolyte and the amorphous TiS electrode showed high capacity of greater than 300 mAh g for 10 cycles. The amorphous TiS had a higher capacity than the mixture of crystalline TiS and S, which was used as the starting material of amorphous TiS. The X-ray diffraction patterns and the Raman spectra of the amorphous TiS electrode after the first and tenth charge-discharge measurements were similar to those before the measurement. The amorphous structure of TiS did not change greatly during the first few cycles. The all-solid-state cells with the amorphous TiS electrode showed higher initial coulombic efficiency because the amorphous TiS active material retained its structure during the initial electrochemical test. [ABSTRACT FROM AUTHOR]

Abstract: Composite electrodes based on amorphous titanium polysulfide and acetylene black were mechanically prepared, and their performance was investigated. The amorphous TiS4 and acetylene black composites were discharged and charged with a high reversible capacity of 563mAhg−1 in the 1.9–3.0 voltage range. The Coulombic efficiency of the composite was higher than that of a sulfur electrode because the dissolution of the polysulfide into electrolytes was suppressed. Amorphization and dispersion of carbon inside the particles were effective in improving the performance of the titanium polysulfide electrodes. [Copyright &y& Elsevier]

Abstract: Amorphous Li2S–GeS2 solid electrolyte thin films were prepared using pulsed laser deposition (PLD) at the compositions of 67–83mol% Li2S. The ionic conductivities at room temperature increased with increasing Li2S contents and attained a maximum value of 1.8×10−4 Scm−1 at the composition of 78mol% Li2S. The obtained solid electrolyte thin film was applied to form an ideal electrode–electrolyte interface in all-solid-state batteries. The all-solid-state lithium cell using LiCoO2 coated with the solid electrolyte thin film operated as a lithium secondary battery at room temperature. [Copyright &y& Elsevier]

Titanium sulfide thin film electrodes were prepared by the pulsed laser deposition method using a KrF excimer laser. Thin films of various compositions were prepared under several deposition conditions such as Ar gas pressure, laser fluence, and target-substrate distance. The thickness of the titanium sulfide thin film prepared under Ar gas pressure of 0.01 Pa, the pulse energy of 200 mJ/pulse, and the distance of 5 cm between the target and the substrate was ca. 400 nm. The films prepared at room temperature showed no peaks in the XRD pattern and no periodic lattice fringe in high-resolution transmission electron microscopic images, suggesting that they were amorphous. An all-solid-state cell using a TiS thin film electrode formed on a pelletized LiS-PS glass-ceramic electrolyte showed the reversible capacity of 543 mAh g, which was higher than that of a cell using a TiS film. The former solid-state cell retained higher capacity for 20 cycles at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: Electrode–electrolyte composite materials were prepared by coating a highly conductive Li2S–P2S5 solid electrolyte onto LiCoO2 electrode particles using pulsed laser deposition (PLD). Cross-sections of the composite electrode layers of the all-solid-state cells were observed using a transmission electron microscope to investigate the packing morphology of the LiCoO2 particles and the distribution of solid electrolyte in the composite electrode. All-solid-state cells based on a composite electrode composed entirely of solid-electrolyte-coated LiCoO2 were fabricated, and their performance was investigated. The coating amounts of Li2S–P2S5 solid electrolytes on LiCoO2 particles and the conductivity of the coating material were controlled to increase the capacity of the resulting all-solid-state cells. All-solid-state cells using LiCoO2 with thick solid electrolyte coatings, grown over 120min, had a capacity of 65mAhg−1, without any addition of Li2S–P2S5 solid electrolyte particles to the composite electrode. The capacity of the all-solid-state cell increased further after increasing the conductivity of the Li2S–P2S5 solid electrolyte coating by heat treatment at 200°C. Furthermore, an all-solid-state cell based on a composite electrode using both a solid electrolyte coating and added solid electrolyte particles was fabricated, and the capacity of the resulting all-solid-state cell increased to 95mAhg−1. [Copyright &y& Elsevier]

Abstract: Amorphous thin film electrolytes in the system Li4SiO4–Li3PO4 were prepared by pulsed laser deposition (PLD). The ionic conductivity of the amorphous film at the composition 50Li4SiO4·50Li3PO4 (mol%) was 1.6×10−6 Scm−1 at room temperature which is higher than the conductivities of Li3PO4 and Li4SiO4 films. The 50Li4SiO4·50Li3PO4 film was coated on LiCoO2 active material particles by PLD. All-solid-state lithium secondary batteries using the coated LiCoO2 electrode and the Li2S–P2S5 solid electrolyte were fabricated. The PLD coating of oxide film with high conductivity on LiCoO2 was effective in decreasing the electrode/electrolyte interfacial resistance and developing power density of the all-solid-state cells. [Copyright &y& Elsevier]

Highly lithium-ion conductive Li2S–P2S5 thin films were prepared using pulsed laser deposition at room temperature. The ambient Ar gas pressure during deposition strongly affected the thin films' chemical compositions and local structures. The chemical composition and the local structure of the 80Li2S·20P2S5 thin film prepared under 5 Pa showed good agreement with those of the highly lithium-ion conducting 80Li2S·20P2S5 glass powder prepared by mechanical milling. The ionic conductivity at 25°C and the activation energy for conduction of the as-deposited 80Li2S·20P2S5 thin films were, 7.9 × 10−5 S/cm and 43 kJ/mol, respectively. The ionic conductivity of the 80Li2S·20P2S5 thin film was increased to 2.8 × 10−4 S/cm through heat treatment. The highly lithium-ion conducting thin-films reported in this study are promising electrolytes for developing all-solid-state lithium batteries. [ABSTRACT FROM AUTHOR]

Abstract: All-solid-state lithium secondary batteries using LiCoO2 particles coated with amorphous Li2O–TiO2 films as an active material and Li2S–P2S5 glass-ceramics as a solid electrolyte were fabricated; the electrochemical performance of the batteries was investigated. The interfacial resistance between LiCoO2 and solid electrolyte was decreased by the coating of Li2O–TiO2 films on LiCoO2 particles. The rate capability of the batteries using the LiCoO2 coated with Li2Ti2O5 (Li2O·2TiO2) film was improved because of the decrease of the interfacial resistance of the batteries. The cycle performance of the all-solid-state batteries under a high cutoff voltage of 4.6V vs. Li was highly improved by using LiCoO2 coated with Li2Ti2O5 film. The oxide coatings are effective in suppressing the resistance increase between LiCoO2 and the solid electrolyte during cycling. The battery with the LiCoO2 coated with Li2Ti2O5 film showed a large initial discharge capacity of 130mAh/g and good capacity retention without resistance increase after 50 cycles at the current density of 0.13mA/cm2. [Copyright &y& Elsevier]

Abstract: All-solid-state lithium secondary batteries using LiCoO2 active materials coated with Li2SiO3 and SiO2 oxide films and Li2S–P2S5 solid electrolytes were fabricated and their electrochemical performance was investigated. The electrochemical performace of the all-solid-state cells at a high voltage region was highly improved by using oxide-coated LiCoO2. The oxide coatings are effective in suppressing the formation of an interfacial resistance between LiCoO2 and the solid electrolyte at a high cutoff voltage of 4.6V (vs. Li). As a result, charge–discharge capacities and cycle performance at the cutoff voltage were improved. The cell with Li2SiO3-coated LiCoO2 showed a large initial discharge capacity of 130mAhg−1 and a good capacity retention of 110mAhg−1 after 50th cycles at the cutoff voltage of 4.6V (vs. Li). [Copyright &y& Elsevier]

Mechanical properties and ionic conductivities of solid electrolytes are important factors influencing the performance of all-solid-state batteries. This study investigates composite quasi-solid electrolytes composed of Li 2 S–P 2 S 5 glass and a phosphate ester, prepared via planetary ball milling, and the relative densities of the powder-compressed pellets, formed using the composite quasi-solid electrolytes. Dense pellets of the Li 2 S–P 2 S 5 glass electrolyte are obtained via addition of phosphate esters; the relative densities increase from 90.6% to 93.1%, without the ionic conductivities decreasing, upon addition of a small quantity of tris (2, 2, 2-trifluoroethyl) phosphate to the Li 3 PS 4 glass. The addition of small quantities of phosphate esters to sulfide solid electrolytes is effective in improving the formability of these solid electrolytes. • Quasi-solid electrolytes of Li 2 S-P 2 S 5 (LPS) glass and phosphate ester are prepared. • Relative density of the electrolytes increases by adding the ester to LPS glass. • Adding the ester increases formability and conductivity of the composites. [ABSTRACT FROM AUTHOR]

RT-NaMn 1/2 Sn 1/2 S 2 was prepared by mechanochemical synthesis from a mixture of Na 2 S, MnS, and SnS 2. The crystal structure was determined from X-ray powder diffraction data. The chemical composition was confirmed by energy dispersive X-ray spectroscopy, and the electrical conductivity was measured using electrochemical impedance spectroscopy. The RT-NaMn 1/2 Sn 1/2 S 2 sample crystallizes with rock salt-type structure, space group Fm 3 ‾ m , a = 5.4368(2) Å, V = 160.71(2) Å3, and Z = 2. This sample exhibits an irreversible phase transition. It transforms into a high temperature phase, HT-NaMn 1/2 Sn 1/2 S 2 which crystallizes with α-NaFeO 2 -type structure, space group R 3 ‾ m , a = 3.7523 (4) Å, c = 19.883 (2) Å, V = 242.44 (4) Å3, and Z = 3. The structure was determined from single crystal XRD data. The electrical conductivities of the RT- and HT-forms are 2.5 × 10−8 S cm−1 (E a = 0.58 eV) and 3.3 × 10−7 S cm−1 (E a = 0.42 eV) at 25 °C, respectively. [Display omitted] • The cubic NaMn 1/2 Sn 1/2 S 2 phase was prepared by mechanochemical synthesis route. • The rock salt structure of the NaMn 1/2 Sn 1/2 S 2 phase was solved from XRPD data. • Irreversible cubic to trigonal phase transition was observed at high temperature. • The trigonal NaMn 1/2 Sn 1/2 S 2 phase is crystallizes with the α-NaFeO 2 -type structure. • The ionic conductivity of the trigonal phase is higher than the cubic phase. [ABSTRACT FROM AUTHOR]

• Room-temperature operating all-solid-state Na-S batteries are fabricated. • High reversible capacity of 1500 mAh g−1 is retained in the batteries for 50 cycles. • Coating of Na 3 SbS 4 on activated carbon–sulfur particles improves cell performance. The need for an effective design of composite electrodes in all-solid-state Na-S batteries is warranted because of their slow charge–discharge reactions. By employing a composite of activated carbon MSP20, sulfur, and Na 3 SbS 4 as the positive electrode material, we developed an effective all-solid-state Na-S battery that demonstrated the advantages of exhibiting a high capacity and good cyclability. Further, we discovered that filling the carbon micropores with sulfur and combining with highly conductive Na 3 SbS 4 , results in a reversible two-electron reaction between S and Na 2 S. This all-solid-state Na-S battery, operating at room temperature, demonstrates a high capacity of 1560 mAh per gram of sulfur (ca. 330 mAh per gram of positive electrode) and a capacity retention of 93% after 50 cycles. Decreasing the size of the S-MSP20 particles coated with Na 3 SbS 4 in a liquid phase process was observed to reduce the volume change of the particles during charge and discharge cycles, which resulted in an excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

The charge-discharge capacity of lithium secondary batteries is dependent on how many lithium ions can be reversibly extracted from (charge) and inserted into (discharge) the electrode active materials. In contrast, large structural changes during charging/discharging are unavoidable for electrode materials with large capacities, and thus there is great demand for developing materials with reversible structures. Herein, we demonstrate a reversible rocksalt to amorphous phase transition involving anion redox in a Li2TiS3 electrode active material with NaCl-type structure. We revealed that the lithium extraction during charging involves a change in site of the sulfur atom and the formation of S−S disulfide bonds, leading to a decrease in the crystallinity. Our results show great promise for the development of long-life lithium insertion/extraction materials, because the structural change clarified here is somewhat similar to that of optical phase-change materials used in DVD-RW discs, which exhibit excellent reversibility of the transition between crystalline and amorphous phase. [ABSTRACT FROM AUTHOR]

Solid electrolytes, such as sulfide glasses, are key materials to put all-solid-state Li-ion batteries into practical use. We evaluated the local structure of 75Li 2 S･25P 2 S 5 (mol%) Li 3 PS 4 glass with a structural phase transition from glass to crystal between 298 K and 523 K by X-ray total scattering data coupled with Reverse Monte Carlo (RMC) modeling. We have obtained structural models consistent with the observed structure factors (S obs (Q)) of Li 3 PS 4 at different temperatures with a low R -factor R p value within 2.0%. The RMC results suggest the PS 4 anion remains a tetrahedron over the wide range from glass to crystal based on the angular and distance distribution of intra-PS 4 S S pairs. On the other hand, the S S correlation of inter-PS 4 distances changes from a wider to a narrower distribution during crystallization. The angular distance distribution functions g (r , θ) indicate that the orientation of the PS 4 tetrahedra changes from random to long-range ordered as crystallization progresses. S Li partial correlation and the average spatial distribution of P and S show a wider distribution of Li-ions at a higher temperature of the glassy state and the distribution then narrows due to crystallization. The RMC results suggest that PS 4 libration plays an important role in Li-ion migration in Li 3 PS 4 solid electrolytes. • RMC can construct local structural model of Li 3 PS 4 over a wide range between glass to crystal. • The peak changes in G obs (r) at r = 3.3 Å and 4.0 Å are caused from narrowing S S correlation of inter-PS 4 anion with crystallization progresses. • The average spatial distribution of S atom and partial distribution function g Li-S (r) are indicated that Li-ion follows near S atom at any state. • The distribution of the angular histogram between the global z -axis and the orientational vector defined in PS 4 anion are narrower changing from glass to crystal. [ABSTRACT FROM AUTHOR]

Abstract All-solid-state batteries comprising sulfide solid electrolytes are promising for energy storage in electric vehicles because of their safety record. There is a high demand for batteries in the form of stackable compact sheets with high cell-based energy density that are mass fabricated in a scalable process. A slurry coating is advantageous for fabricating sheet-type batteries, improves productivity, and allows control of the layer thickness. Here we present a slurry-mixing method for fabricating homogeneously dispersed composite sheets containing micrometer-sized silicon particles. Subsequent removal of the volatile binder from the stacked-sheet cells is demonstrated to reduce their internal resistance. The silicon composite sheets exhibit high initial Coulombic efficiencies of 95%, with practical areal capacities of 2.0–4.4 mAh cm−2 at the 47th cycle under 0.30 mA cm−2, a reversible specific capacity of 2300 mAh g−1 after 100 cycles, and long-term cycling stability (specific capacity above 1700 mAh g−1 after 375 cycles). Cracks that are vertical to the silicon composite layer after cycling buffer the internal strain originating from silicon volume changes, providing excellent cycling stability. These results can assist the rational design of silicon anodes for high-cell-performance all-solid-state batteries. Graphical abstract Image 1 Highlights • Slurry mixing assisted by ZrO 2 balls forms good ionic/electronic conduction paths. • The binder is removed from the sheet-type cell to minimize its resistance. • The μm-Si-composite sheet with practical areal capacity has excellent performance. • Strain from Si volume changes is buffered by vertical cracks in the composite layer. • The slurry overcoating of solid electrolyte leads to high cell-based energy density. [ABSTRACT FROM AUTHOR]

Abstract The use of Li metal anode is important for developing all-solid-state Li rechargeable batteries with high energy densities. In this study, all-solid-state Li symmetric cells using sulfide electrolytes in the Li 3 PS 4 -LiI system were fabricated to investigate the Li dissolution/deposition cycling performance. A cell using 54Li 3 PS 4 ·46LiI (mol%) glass electrolyte was cycled at a current density of 1.25 mA cm−2 for 3400 h at 100 °C without short-circuiting, and the highest areal capacity of 7.5 mAh cm−2 was achieved. Structural analyses of the interface between Li and solid electrolytes revealed that the reduction of electrolyte by the Li metal was suppressed by adding LiI to Li 3 PS 4 , and good interfacial contact was maintained even after prolonged cycling. The addition of LiI to Li 3 PS 4 glass improved the tolerance to reduction with Li metal, and enhanced the Li dissolution/deposition cycling performance. [ABSTRACT FROM AUTHOR]

The structure of Fe-substituted Li 2 S-based positive electrode material Li 8 FeS 5 was analyzed using high-energy X-ray total scattering measurements. Pair distribution function (PDF) analyses indicated that the mechanically milled Li 8 FeS 5 sample could best be described as having an anti-fluorite structure in which Fe ions partially occupy Li sites in the Fm 3 ¯ m unit cell. The electrochemical properties of a cell utilizing Li 8 FeS 5 as the positive electrode were also consistent with this structural model. [ABSTRACT FROM AUTHOR]

Amorphous active materials have been developed for high-performance lithium and sodium secondary batteries to achieve a higher capacity, higher rate performance, and longer cycle life than those of crystalline active materials. In this study, a new function of amorphous active materials was explored through the heat treatment of pseudobinary amorphous materials (for example, LiCoO 2 –Li 2 SO 4). Additionally, active materials with crystalline/amorphous nanoheterostructures, in which the nano-LiCoO 2 domains were dispersed in a Li 2 SO 4 -rich matrix, were demonstrated. In all-solid-state batteries with sulfide solid electrolytes (SEs), the crystalline/amorphous active materials reduced the interface resistance of the active material and SE when compared with that of Li. High electrochemical performance was achieved using the Li 2 SO 4 -rich matrix, which served as an interfacial stabilizer. In summary, this paper reports a new strategy based on annealing amorphous materials for developing active materials with nanoheterostructures for high-performance energy storage devices. [Display omitted] • Electrode active materials with crystalline/amorphous nanostructures were developed.. • The active materials showed high electrode performance in all-solid-state batteries. • This study offers a new strategy for high-performance secondary batteries.. [ABSTRACT FROM AUTHOR]

The problem of lithium dendrites must be addressed for practical lithium metal all-solid-state batteries. Herein, three-dimensional morphological changes within Li3PS4 electrolyte away from the anode were observed using operando X-ray computed tomography. We revealed that the electronic conduction of decomposition and the electrolyte/void interface cause the lithium deposition within the Li3PS4. [ABSTRACT FROM AUTHOR]

Yellow needles-like single crystals of Li4P2S6 were obtained serendipitously during the preparation of Li7P3S10O. The twinned crystal structure of Li4P2S6 was determined from single-crystal X-ray diffraction data [wR(F2) = 0.069, 716 reflections, 40 variables]. Li4P2S6 crystallizes in the trigonal system, space group P 3 ‾ m 1 (N° 164), a = 10.5042(8) Å, c = 6.5837(6) Å, V = 629.11(9) Å3 and Z = 2. The lithium octahedra form a [Li4S6]8− honeycomb-like structure within which diphosphate units are located. The comparison of our crystal structure to those of P63/mcm-, P 3 ‾ 1 m -, and P321-Li4P2S6 demonstrated group-subgroup relationships and associated the disorder or order of the phosphorus atoms within the identical [Li4S6]8− 3d-frameworks to the choice of the unit cell (the subcell with a ∼ 6.07 Å vs. the supercell with a ∼ 10.5 Å). [ABSTRACT FROM AUTHOR]

Transparent needles-like single crystals of Na 2 MgP 2 S 6 were obtained by self-flux synthesis route from Na 2 S, Mg, and P 2 S 5. The crystal structure of the new compound was determined from single-crystal X-ray diffraction data [ wR (F 2) = 0.066, 1088 reflections, 58 variables]. The chemical composition was confirmed by energy dispersive X-ray spectroscopy (EDX), and the ionic conductivity was measured using electrochemical impedance spectroscopy (EIS). Na 2 MgP 2 S 6 crystallizes in the orthorhombic system, space group Pbcn (N° 60), a = 7.3629 (3) Å, b = 21.5547 (8) Å , c = 6.2155 (3) Å, V = 986.43 (7) Å3 and Z = 4. The sulfur atoms form a distorted hexagonal close packing within which the sodium, magnesium, and P-P dimer units are octahedrally coordinated and form a honeycomb-like structure. Two of the three sodium atomic positions are partially occupied. Na 2 MgP 2 S 6 exhibits an ionic conductivity of 8.8×10−7 S cm−1 (E a = 0.48 eV) at 29.6 °C. [Display omitted] • The crystallographic data of thiohypodiphosphate compounds were reviewed. • The single crystals of Na 2 MgP 2 S 6 were obtained by self-flux synthesis route. • The unique crystal structure of Na 2 MgP 2 S 6 was solved from single crystal XRD. • The structure of Na 2 MgP 2 S 6 is isostructural to the Na 2 MnP 2 S 6 -type. • The electrical conductivity of Na 2 MgP 2 S 6 is 8.8×10−7 S cm−1 at 29.6 °C. [ABSTRACT FROM AUTHOR]

All-solid-state sodium-sulfur (Na/S) batteries are promising next-generation batteries with high safety and high energy density. Sodium sulfide (Na 2 S) has application as active material in positive electrodes owing to its advantages such as low cost, low toxicity, and a large theoretical capacity. However, the electronic and sodium ion conductivities of Na 2 S are significantly low, and ascertaining the entire contribution of the active materials to cell capacities is challenging. Therefore, facilitating an electronic and ionic conduction path in the positive electrode is essential. In this study, Na 2 S was mixed with sodium iodide (NaI) via a mechanochemical process and was used as an active material in an all-solid-state Na/S battery. Consequently, a Na 2 S–NaI solid solution was formed, and the ionic conductivity of Na 2 S–NaI increased by five orders of magnitude compared to that of Na 2 S. Na 2 S–NaI showed large charge–discharge capacities and cycle capability. In particular, 90Na 2 S·10NaI showed a large capacity and high cycle efficiency, and 94% of Na 2 S acted as an active material. The result of this study leads to the development of all-solid-state Na/S batteries with high capacities, high rates, and high cycles. • Na 2 S–NaI solid solution was synthesized via mechanochemical process. • Na 2 S–NaI showed five orders of magnitude higher ionic conductivity than that of Na 2 S. • Na 2 S–NaI showed large charge–discharge capacities and cycle capability. [ABSTRACT FROM AUTHOR]

The electrochemical window of solid electrolytes (SEs) plays a crucial role in designing active material–SE interfaces in high‐energy‐density all‐solid‐state batteries (ASSBs). However, the suitable electrochemical window for individual active materials is not yet investigated, as the electrochemical window of SEs is overestimated. In this study, the oxidation onset voltages (OOVs) of several SEs, namely those compatible with Li2S as a high‐capacity positive electrode material are determined. Results reveal that SEs with low OOVs decrease the capacity and increase the interfacial resistance of the corresponding ASSBs. The OOVs of SEs must exceed that of Li2S by more than 0.2 V to achieve high capacity, which in turn depends on SE ionic conductivity. Therefore, an Li2S positive electrode is combined with pseudobinary Li‐oxyacid salts as SEs, exhibiting high OOVs and ionic conductivities, to afford a high‐capacity (500 Wh kg−1) ASSB with high Li2S content. [ABSTRACT FROM AUTHOR]

Sulfide-based solid electrolytes (SEs) exhibiting high ionic conductivity are indispensable battery materials for next-generation all-solid-state batteries. However, sulfide-based SEs have a major drawback in their low chemical stability in air. When exposed to H2O or O2 gas, toxic H2S is generated, and their ionic conductivity considerably declines. However, their degradation mechanism caused by air exposure has not been understood yet. To clarify the degradation process, in this study, we developed a transmission electron microscope (TEM) system to evaluate the air stability of battery materials. Using a vacuum transfer double-tilt TEM holder with a gas-flow system, the in situ observation of the degradation process was conducted for a sulfide-based Li4SnS4 glass ceramic under an air-flow environment. Consequently, electron diffraction (ED) patterns and TEM images could clearly capture morphological changes and the amorphization process caused by air exposure. Moreover, based on the analysis of ED patterns, it is observed that Li4SnS4 is likely to decompose because of the reaction with H2O in air. Therefore, this airtight and air-flow TEM system should be effective in clarifying the process of the deterioration of sulfur-based SEs during exposure to air. [ABSTRACT FROM AUTHOR]

All-solid-state sodium batteries are attracting attention as next-generation batteries, owing to their improved safety and abundance of sodium resources. To realize all-solid-state sodium batteries, solid electrolytes with high sodium-ion conductivities are required. In this study, Na 3 PS 4 electrolytes with partial substitution of P5+ with W6+ were investigated. The Na 3– x P 1– x W x S 4 sulfide-based solid electrolytes were prepared via a mechanochemical process and consecutive heat treatment. The Na 2.85 P 0.85 W 0.15 S 4 electrolyte with Na vacancies exhibited an ionic conductivity of 8.8 × 10−3 S cm−1 at 25 °C, which was higher than that of Na 3 PS 4 solid electrolyte. The all-solid-state batteries (Na-Sn/Na 2.85 P 0.85 W 0.15 S 4 /TiS 2) exhibited a reversible capacity of 140 mA h g−1 at a current density of 0.038 mA cm−2 and retained the capacity of 115 mAh g−1 for 40 cycles at 0.130 mA cm−2 at 25 °C. The Na 3– x P 1– x W x S 4 samples prepared via mechanochemistry are homogeneous electrolytes free of crystalline WS 2 impurities and are effective for application to all-solid-state sodium batteries. • Sulfide Na 3– x P 1– x W x S 4 electrolytes are prepared via a mechanochemical process. • Na 2.85 P 0.85 W 0.15 S 4 with Na vacancies shows a conductivity of 8.8 × 10−3 S cm−1. • All-solid-state cells exhibit a reversible capacity of 140 mAh g−1 of TiS 2 at 25 °C. [ABSTRACT FROM AUTHOR]

All-solid-state lithium‑sulfur batteries (ASSLSBs) based on sulfur or lithium sulfide (Li 2 S) as cathodes are one of the most promising candidates for next-generation energy storage devices due to their high theoretical energy density and good safety features. However, despite the promising outlook, the practical application of ASSLSBs is impeded due to the electronically and ionically insulating nature of S and Li 2 S. Consequently, even with carbon and solid state electrolytes (SSEs) addition, the electron and lithium-ion cannot transport smoothly through the cathode. Therefore, it is imperative to establish and tune effective electron/ion transport paths in the composite cathode to achieve high performance. In the present study, electronically/ionically dual conductive active material Li 2 S-LiI-MoS 2 and high ionically conductive Li 6 PS 5 Cl SSE were coupled and modified to control ionic and electronic paths in Li 2 S-based cathode composite. The optimized composite cathode possessed an overall gravimetric capacity of 423 mAh g−1 at 0.5C and 308 mAh g−1 at 2C with respect to the total mass of the cathode. The corresponding ASSLSBs achieved distinctively high energy with acceptable power density. The in-depth analysis by X-ray computed tomography revealed the three-dimensional conductive pathway in the composite cathode. • The Li 2 S-LiI-MoS 2 coupling with Li 6 PS 5 Cl as composite cathode. • The cathode shows balanced electronic and ionic conductivity approaching 10−3 S cm−1. • The optimized composite cathode exhibits good overall capacity of 423 mAh g−1 at 0.5C and 308 mAh g−1 at 2C. • X-ray CT reveals the microstructure of the cathode, including tortuosity and contact area. [ABSTRACT FROM AUTHOR]

Highlights: [•] LiMn2O4 thin films were prepared by using the mist CVD process. [•] An aqueous solution of lithium and manganese acetates is used for the precursor solution. [•] The cell with the LiMn2O4 thin films exhibited a capacity of about 80mAh/g. [•] The cell showed good cycling performance during 10 cycles. [Copyright &y& Elsevier]

Compressive pressure applied during the operation of all-solid-state batteries that employ a sulfide solid electrolyte (SE) assists particle contact, thereby maintaining the ionic and electronic conduction network. The relationship between compressive pressure and volume variation in active materials is critical for designing practical full-cells with enhanced cell-based energy densities. However, studies into these aspects are rare. Here, we systematically investigate the effects of volume change of active materials [silicon, graphite, and LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC)] at different pressures (75 and 50 MPa) on electrochemical performance, cell internal resistance, and microstructure of full-cells with a thin SE layer (approximately 75-μm-thick). Pressurization at 75 MPa and use of graphite with lower expansion ratios improves capacity and capacity retentions. Increasing variation in the negative electrode volume increases charge-transfer resistance and crack formation in the NMC-composite layer. This indicates that the buffering effect via the elastic deformation of the thin SE layer is insufficient. Pressure facilitates plastic deformation of Li x Si and SE, resulting in their improved contact, while perpendicular cracks appear throughout the Si-composite layer, effectively alleviating stress derived from variations in the volume of Si. This study provides important mechanistic insights into the design of advanced active materials and batteries required for industrial applications. Image 1 • Effects of volume variations in active materials under pressure on cells are studied. • High compressive pressure and low volume variation improve cell performance. • Volume variation of Si affects opposite electrode via thin solid electrolyte layer. • Pressure heals fine cracks and forms large perpendicular cracks in Si electrodes. • Pressure facilitates contact of Li x Si and solid electrolyte via plastic deformation. [ABSTRACT FROM AUTHOR]

White opaque single crystals of Na 6 Ge 2 S 6 O were obtained serendipitously during the preparation of Na 4 GeS 4. Then, pure glass and ceramic Na 6 Ge 2 S 6 O samples were synthesized from Na 2 S, GeS 2 , and GeO 2 reagents. The crystal structure was determined from powder and single crystal X-ray diffraction data. The physical properties were characterized by TG-DTA, SEM-EDX, Raman spectroscopy and electrochemical impedance spectroscopy. Na 6 Ge 2 S 6 O crystallizes with a new type of structure in the non-centro-symmetric space group P 2 1 2 1 2 1 , a = 6.96882 (6) Å, b = 7.04159 (6) Å, c = 26.7069 (2) Å, V = 1310.55 (2) Å3 and Z = 4. The asymmetric unit is built up of six Na+ cations surrounding a bi-tetrahedral complex anion, [S 3 GeOGeS 3 ]6−, which adopts a staggered conformation. The strongly distorted sodium polyhedra share edges and/or faces. The electrical conductivities of Na 6 Ge 2 S 6 O glass and ceramic at 25 °C are 2.9 × 10−5 S cm−1 (E a = 0.47 eV) and 1.8 × 10−7 S cm−1 (E a = 0.43 eV), respectively. [Display omitted] • The ternary system Na 2 S-GeO 2 -GeS 2 was investigated by solid state synthesis. • Glass and ceramic forms of the new Na 6 Ge 2 S 6 O compound were prepared. • Single crystals of Na 6 Ge 2 S 6 O were isolated after melting the Na 4 GeS 4 composition. • The new crystal structure was solved from powder and single crystal XRD data. • The electrical conductivity of amorphous Na 6 Ge 2 S 6 O is 2.9 × 10−5 S cm−1 at 25 °C. [ABSTRACT FROM AUTHOR]

Electron tomography is an observation technique for nanometer-scale three-dimensional structures, using transmission electron microscopy (TEM). TEM tomography has been used to examine the 3D structures of various materials, such as biological samples and catalysts. In this study, we applied TEM tomography to battery materials. All-solid-state lithium-ion batteries have recently received much attention owing to their thermal safety. In all-solid-state cells, the electrode layer is composed of nonflammable solid electrolytes and electrode active materials. In order to improve the charge–discharge cycle performance, it is necessary that the electrolyte–electrode interface has no void spaces or defects. We used TEM tomography to investigate the solid interfaces of Sn–Li3PS4 (LPS) negative electrode composites of all-solid-state cells. We observed that Sn, Li-Sn alloy nanoparticles, and LPS glass electrolytes formed a solid interfacial contact with no void spaces during initial charge–discharge cycles. We suggest that as a new cycle deterioration analysis method, TEM tomography is useful in evaluating solid interfaces in all-solid-state cells. [ABSTRACT FROM AUTHOR]

As an environmentally friendly Pb-free material, SnO–B 2 O 3 glass is considered a next-generation negative-electrode active material for all-solid-state lithium-ion batteries. Using SnB 2 O 4 (50SnO·50B 2 O 3) as a negative-electrode active material, the all-solid-state cells exhibit a high initial discharge capacity of approximately 950 mAh g−1. In this study, the microstructures of the SnB 2 O 4 glassy electrode composites are investigated to clarify the charge–discharge behavior and charge–discharge mechanisms of the SnB 2 O 4 glassy electrode composites using transmission electron microscopy (TEM). Here, ex situ TEM observations capture Sn and Li–Sn alloy nanocrystallites in the amorphous matrix. Li+ is incorporated into Sn, and Li–Sn alloy nanocrystallites are formed after initial lithiation. Further, Li+ is extracted from Li–Sn alloys to form Sn nanocrystallites after initial delithiation. In particular, Sn is lithiated and delithiated during the first cycle. However, as the cycle number increases, the capacity deteriorates. Ex situ TEM observations further reveal that Li–Sn alloys remain unchanged even after delithiation, and the crystallite size increases significantly. It is thus found that the capacity deterioration is attributed to the irreversible Li insertion/extraction between Sn and Li–Sn alloys. • SnO–B 2 O 3 glass is a next-generation negative-electrode active material. • SnO–B 2 O 3 glass is applied to all-solid-state lithium-ion batteries. • Microstructure and morphology during charge-discharge process are examined by TEM. • Ex situ TEM observations capture the formation of Sn and Li–Sn alloy crystallites. [ABSTRACT FROM AUTHOR]

Sulfide-based lithium ionic conductors show high conductivity. Many studies have focused on improving conductivity and understanding their migration mechanisms. Argyrodite-type Li 6 PS 5 X (X = Cl, Br, I) electrolytes with P cations are among the main subjects of research regarding the substitution of anions and cations. In this study, argyrodite-type thioantimonate electrolytes were prepared to extend the compositions of argyrodite-type electrolytes and study their mechanisms of ion conduction. An argyrodite-type crystal precipitated in the composition of Li 6 SbS 5 I, but was not obtained in the composition of Li 6 SbS 5 X (X = Cl, Br). This could be explained by the difference in size between the SbS 4 tetrahedra and halide anions. Argyrodite-type Li 6 SbS 5 I displayed a conductivity of 2.1 × 10−6 S cm−1 at 25 °C, which was higher than that of Li 6 PS 5 I. Comparing these crystal structures, only the lattice parameters differed, and the site positions and occupancies were almost identical. However, the pathways limiting 3D migration were intra-cage jumps within Li 6 SbS 5 I and inter-cage jumps within Li 6 PS 5 I, based on their bond valence-based energy landscapes. The bottleneck sizes for ionic conduction in Li 6 SbS 5 I is better than that of Li 6 PS 5 I. This difference was due to the lattice parameters derived from the SbS 4 and PS 4 tetrahedra. This study reveals a strategy to predict the producibilities and increase the conductivities of argyrodite-type electrolytes. • Argyrodite-type Li 6 SbS 5 X (X = Cl, Br, I) electrolytes are prepared. • Only Li 6 SbS 5 I exhibits an argyrodite-type structure. • The sizes of the MS 4 tetrahedra are critical in forming the argyrodite structure. • Li 6 SbS 5 I displays a higher ionic conductivity than that of Li 6 PS 5 I. • The different sizes of the MS 4 tetrahedra affect the ion migration pathways. [ABSTRACT FROM AUTHOR]

The Na 2 S-Na 4 GeS 4 section of the binary system Na 2 S-GeS 2 has been studied and the crystal structure of the Na 4 GeS 4 compound was determined from single-crystal X-Ray diffraction data. The physical properties of Na 4 GeS 4 were characterized by X-ray powder diffraction, TG/DTA, SEM-EDX, Raman spectroscopy and electrochemical impedance spectroscopy. Na 4 GeS 4 crystallizes with a new type of structure in the non-centro-symmetric space group Im , a = 10.9822(9) Å, b = 29.652(2) Å, c = 20.0391(16) Å, β = 105.77(1) (°), V = 6279.96(90) Å3 and Z = 30. The Na 4 GeS 4 asymmetric unit that contains 76 atoms is made up of 10 isolated GeS 4 tetrahedra. The 31 sodium atoms are located between these tetrahedra. The distorted NaS 6 octahedra, NaS 5 trigonal bipyramids, NaS 5 square pyramids and NaS 4 tetrahedra share corners, edges or faces. The electrical conductivity [2.7 × 10−5 S cm−1 (E a = 0.41 eV) at 25 °C] of the Na 4 GeS 4 glass phase, prepared by mechanochemical synthesis, is two orders of magnitude higher than that of the glass-ceramic phase, prepared by the combination of mechanochemical and solid-state synthesizes [9.8 × 10−8 (E a = 0.65 eV) at 25 °C]. [Display omitted] • The binary system Na 2 S-GeS 2 was reinvestigated by solid state synthesis. • Amorphous Na 4 GeS 4 was prepared by mechanochemical synthesis. • Single crystals of Na 4 GeS 4 were isolated after melting the Na 6 GeS 5 composition. • The unique crystal structure of Na 4 GeS 4 was solved from single crystal XRD. • The electrical conductivity of amorphous Na 4 GeS 4 is 2.7 × 10−5 S cm−1 at 25 °C. [ABSTRACT FROM AUTHOR]

All-solid-state sodium batteries with sulfide-based solid electrolytes are attracting attention as next-generation energy storage systems to replace Li-ion batteries, owing to their improved safety and the abundant sodium resources. Na 3 PS 4 -based materials, which have relatively high conductivities and favorable mechanical properties, make promising Na-ion solid electrolytes for realizing all-solid-state sodium batteries. However, it is essential to establish a further simple and effective protocol for manufacturing such solid electrolytes and composite electrodes. In this study, Na 3- x PS 4- x Cl x (x = 0, 0.0625) was prepared by a liquid-phase (suspension) process from Na 2 S, P 2 S 5 , and NaCl using 1,2-dimethoxyethane as a reaction media. Na 3 PS 4 heated at 400 °C and Na 2.9375 PS 3.9375 Cl 0.0625 heated at 480 °C exhibited Na-ion conductivities of 2.6 × 10−4 and 4.3 × 10−4 S cm−1 at 25 °C, respectively. A homogenous composite electrode was prepared with TiS 2 active material and Na 3 PS 4 solid electrolyte via the simple liquid-phase process, resulting in large contact areas between electrode and electrolyte particles. The electrode obtained by liquid-phase provided an all-solid-state cell with higher reversible capacity of 161 mAh g−1 than a conventional mechanically mixed electrode. Suspension syntheses of Na 3- x PS 4- x Cl x are useful for the simple production of solid electrolytes and are highly applicable to all-solid-state sodium batteries. • Na 3- x PS 4- x Cl x (x = 0, 0.0625) electrolytes are prepared using 1,2-dimethoxyethane. • Na 3 PS 4 shows a high sodium-ion conductivity of 2.6 × 10−4 S cm−1. • Na 2.9375 PS 3.9375 Cl 0.0625 exhibits a superior conductivity of 4.3 × 10−4 S cm−1. • A TiS 2 –Na 3 PS 4 composite electrode is obtained by a simple liquid-phase process. • An all-solid-state cell using the electrode shows a high capacity of 161 mAh g−1. [ABSTRACT FROM AUTHOR]

Abstract Li 3 SbS 4 glass was prepared by a mechanochemical process and a glass-ceramic was prepared by heating the glass above the crystallization temperature. The glass-ceramic had a crystal structure similar to that of γ-Li 3 PS 4. As indicated by the Raman spectra, both electrolytes contained an SbS 4 unit. The conductivity of the pelletized Li 3 SbS 4 glass was 1.5 × 10−6 S·cm−1 at 25 °C, which was higher than that of its glass-ceramic. The amount of H 2 S generated from Li 3 SbS 4 glass in humid air was considerably lower than that from the Li 3 PS 4 glass. Highlights • Li 3 SbS 4 glass electrolyte is prepared by a mechanochemical process. • The crystal structure of Li 3 SbS 4 precipitated in Li 3 SbS 4 glass-ceramic is revealed. • The glass exhibits the conductivity of 1.5 × 10−6 S cm−1 at 25 °C. • The conductivity of the glass-ceramic is lower than that of the glass. • The glass hardly generates any H 2 S gas even when exposed to humid air. [ABSTRACT FROM AUTHOR]

Abstract All-solid-state cells are safe, and have high energy densities and power densities. Sulfide-based solid electrolytes (SEs) exhibit high ionic conductivities and favorable mechanical properties allowing for the facile preparation of all-solid-state cells via simple mixing and cold-pressing processes. For practical applications, it is necessary to produce SEs and all-solid-state cells more efficiently. Herein, a novel fabrication process for homogeneous composite electrodes used in all-solid-state cells was successfully demonstrated using an infiltration technique. The Li 4 Ti 5 O 12 and carbon nanotube (LTO@CNT) porous electrode was infiltrated with a precursor solution containing an argyrodite Li 6 PS 5 Br SE, and the solvent was removed by drying at 150 °C under vacuum to prepare an infiltrated SE-LTO@CNT electrode. The process without conventional mixing formed an electrochemically active interface with a large contact area and favorable conduction pathways. The all-solid-state cell with the SE-LTO@CNT electrode showed an improved capacity of 163 mAh g−1 compared to those prepared with the dry-mixed electrodes at 25 °C, and the high capacity was maintained for 500 cycles. Moreover, the cell with the SE-LTO@CNT electrode showed a reversible capacity of 100 mAh g−1 or more at 4 C-rate and 100 °C. Thus, the infiltration process is effective for the practical fabrication and application of all-solid-state cells. Highlights • Li 4 Ti 5 O 12 -CNT-Li 6 PS 5 Br electrode is prepared by an infiltration technique. • The infiltration process is effective in achieving electrode-electrolyte interface. • An all-solid-state cell with the electrode shows a high capacity of 163 mAh g−1. • The cell operates with high rate and good cycle performances at 100 °C. [ABSTRACT FROM AUTHOR]

Na 3 PS 4 solid electrolytes were synthesized by liquid-phase reactions of Na 2 S and P 2 S 5 in 1,2-dimethoxyethane or diethyl ether. After stirring of the starting materials, white suspensions were obtained. The suspensions were dried at room temperature and heated at 270 °C under vacuum to obtain powders. The crystalline phases of the powders were cubic Na 3 PS 4 . The pelletized Na 3 PS 4 prepared using 1,2-dimethoxyethane or diethyl ether showed conductivities of 2.6 × 10 − 5 S cm − 5 or 1.8 × 10 − 5 S cm − 1 at 25 °C, respectively. [ABSTRACT FROM AUTHOR]

The ternary oxide glasses in the system of Li 3 BO 3 -Li 2 SO 4 -Li 2 CO 3 were prepared by mechanical milling. By heating the glasses to crystallize, the glass-ceramics were obtained. The 90Li 3 BO 3 ·7Li 2 SO 4 ·3Li 2 CO 3 (mol%) glass-ceramic electrolyte showed the conductivity of 1.0 × 10 − 5 S cm − 1 at room temperature, which was higher than that of the 90Li 3 BO 3 ·10Li 2 SO 4 glass-ceramic electrolyte. At the 33Li 3 BO 3 ·33Li 2 SO 4 ·33Li 2 CO 3 composition, a cold-pressed pellet at 720 MPa of the glass exhibited excellent formability with the relative density of 90%, which was comparable to that of sulfide glass electrolytes. By heating the glass, a metastable phase was precipitated and the glass-ceramic exhibited the conductivity of 1.8 × 10 − 6 S cm − 1 at room temperature. To obtain a denser pellet, hot-pressing at around its glass-transition temperature and consecutive crystallization were conducted. The hot-pressed pellet of the glass-ceramic was transparent and showed the conductivity of 2.3 × 10 − 6 S cm − 1 at room temperature. From the ultrasonic pulse-echo measurement, the bulk modulus of the glass was 44 GPa, which was lower than that of 68 GPa of the 90Li 3 BO 3 ·10Li 2 SO 4 glass. From the galvanostatic cycling test, the 33Li 3 BO 3 ·33Li 2 SO 4 ·33Li 2 CO 3 glass-ceramic electrolyte was kinetically stable against lithium metal negative electrode. The 33Li 3 BO 3 ·33Li 2 SO 4 ·33Li 2 CO 3 glass-ceramic electrolyte is therefore a promising material with both conductivity and ductility for the application to all-solid-state batteries. [ABSTRACT FROM AUTHOR]

Sulfide-based solid electrolytes have gained attention for application in solid-state lithium batteries, due to their high ionic conductivities, suitable mechanical properties, and wide electrochemical windows. However, the sulfide in these materials is very hygroscopic, and can react with traces of water, thus generating toxic H 2 S gas. This reduces the lithium-ion conductivity, which plays an important role in solid state batteries. On the contrary, it has also been found that the conductive performance of a sulfide solid electrolyte exposed to water can be partially recovered by a suitable heat treatment. In this study, multiple spectroscopic analyses using X-ray photoelectron spectroscopy, Raman spectroscopy, nuclear magnetic resonance spectroscopy, and diffuse reflectance infrared Fourier-transform spectroscopy were performed on an argyrodite-type sulfide solid electrolyte to elucidate the degradation mechanism under a small amount of moisture, as in a dry room, as well as the recovery mechanism of a degraded sample by vacuum heat treatment. We found that the degradation behavior of the PS 4 3− unit and the adsorption/desorption of water molecules on the surface of the electrolyte were correlated with the lithium-ion conductivity. [Display omitted] • Water durability of an argyrodite-type sulfide-based solid electrolyte in a low dew point air was investigated by using XPS, Raman, NMR, and DRIFTS. • The decomposed species and the adsorbed H 2 O were observed on the SE surface. • It was directly confirmed that the adsorbed H 2 O was desorbed by vacuum heating, and the conductivity recovered partially. [ABSTRACT FROM AUTHOR]

For an attempt to incorporate phosphorous ions into the Fe-containing Li 2 S, we have prepared Li 2 S–FePS 3 composite positive electrode materials using the combination process of the thermal heating and the mechanical milling. The XRD results showed that the Li 2 S–FePS 3 composite samples consisted of low-crystalline Li 2 S and small amounts of FeP as impurity. The electrochemical tests demonstrated that the Li 2 S-rich composite sample cells (Li 2 S:FePS 3 = 4:1 mol) showed relatively high initial discharge capacity (ca. 780 mAh·g − 1 ) without any pre-cycling treatments. This makes a clear contrast to the Fe-containing Li 2 S (Li 2 S–FeS x composite) sample cells, which showed the initial discharge capacity of ca. 330 mAh·g − 1 and it was enlarged to ca. 730 mAh·g − 1 after the stepwise pre-cycling treatment. Ex-situ XRD and XAFS measurements showed the reversible changes of the peaks ascribed to Li 2 S and the local structures around S atoms during cycling. The incorporation of phosphorous ions into the Fe-containing Li 2 S was effective for improving the structural reversibility against Li extraction/insertion reactions, resulting in the improved electrochemical performance of the cells. [ABSTRACT FROM AUTHOR]

The development of all-solid-state capacitors (ASSCs) based on inorganic solid electrolytes (SEs) with high thermal stability is desired. However, because of their high cell resistance, such capacitors have lower capacitances and rate capabilities than conventional electric double-layer capacitors (EDLCs) that use aqueous solutions and organic liquid electrolytes. The high resistance is caused by the mechanical and electrochemical properties of the SE. In this study, a highly deformable Li-ion conducting oxide SE was investigated to improve the electrochemical performance of ASSCs. Bulk-type symmetric ASSCs, with a 33Li 3 BO 3 ·33Li 2 SO 4 ·33Li 2 CO 3 (LBSC) SE layer between two electrode layers of an LBSC-CNT composite, showed low resistance and were operable at 100–300 °C. Additionally, the highest capacitance at the highest current reported for ASSCs till date was achieved. The highly deformable SE will facilitate the design of ASSCs and expand the potential range of applications of EDLCs. [Display omitted] • Thermally stable all-solid-state capacitor with oxide electrolyte is developed. • Highly-deformable electrolyte and carbon nanotube are mixed to obtain electrode. • The fabricated capacitor is operable at 100–300 °C with high capacity. [ABSTRACT FROM AUTHOR]

A promising method to increase the energy density of all-solid-state batteries (ASSBs) featuring lithium ions as carriers is to employ Li metal as the anode. However, this has been accompanied by safety problems like flammable accidents associated with lithium dendrites originating from reactions with the solid electrolyte, leading to reduced battery performance. To overcome this issue toward the commercialization of ASSBs, various approaches have been proposed by many researchers. Among the suggested solutions, the use of lithium-halide-doped Li 3 PS 4 , to suppress lithium dendrite formation, has attracted attention. LiI-doped Li 3 PS 4 has shown the highest lithium dendrite growth suppression among lithium-halide-doped systems, but the reason for this is unclear. Thus, we attempted to clarify the cause of this suppression by comparing LiBr-doped Li 3 PS 4 with LiI-doped Li 3 PS 4. Investigation using various methods such as electrochemical evaluation, X-ray absorption spectroscopy, X-ray computed tomography, and pair distribution function analysis revealed that two factors affect the suppression of Li dendrite growth: the suppression of the current density distribution by improving the ionic conductivity and the stable interfacial layer. This is the main reason LiI-doped Li 3 PS 4 shows excellent Li dendrite suppression. • The structural properties and ability to lithium dendrite suppression of LiBr–doped Li 3 PS 4 were investigated by pair distribution function (PDF) analysis and critical current density (CCD) test in relation to the ionic conductivity. • The PDF analysis revealed that the LiBr–doped Li 3 PS 4 solid electrolyte has a structure in which bromine is inserted between the PS 4 3− anions. • Although Interfacial layer between LiBr-doped Li 3 PS 4 and Li metal is stable, the interfacial resistance is relatively high. [ABSTRACT FROM AUTHOR]

Graphite–solid electrolyte (SE) composite anode, prepared by spark-plasma-sintering (SPS) process, was applied to all-solid-state lithium secondary batteries with lithium sulfide (Li2S) positive electrode. The electrochemical tests demonstrated that the graphite–SE/Li2S cells showed the discharge capacity of ca. 750mAh·g−1-Li2S with the average voltage of ca. 1.98V. Although the discharge capacity was lower than that of the In/Li2S cells (ca. 920mAh·g−1-Li2S), the estimated energy density was higher than that (ca. 1490 and 1220mWh·g−1-Li2S for graphite–SE/Li2S and In/Li2S cells, respectively), due mainly to its higher average voltage. The graphite–SE/Li2S cells showed improved rate capability as compared with the cells with the graphite+SE blended powder, which was attributable mainly to the reduced interfacial resistance between the graphite and SE particles caused by the SPS process. [ABSTRACT FROM AUTHOR]