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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]

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]

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]

Effects of modification of the electrode/electrolyte interface with Li2O-SiO2 thin films on impedance profiles and rate capabilities of all-solid-state ln/80Li2S·20P2S5 glass ceramic/LiCoO2 cells were investigated. Large resistance was observed at the LiCoO2—electrode/sulfide—electrolyte interface in all-solid-state cells. The interfacial resistance was decreased by 0.06 wt % oxide coatings on LiCoO2 the effective coatings were a lithium-ion conductive Li2SiO3 glassy film and an insulative SiO2 film. The Li2SiO3 coating film decreased the interfacial resistance more effectively when the coating amounts increased from 0.06 to 0.6 wt % (film thickness was ca. 10 nm). However, 0.6 wt % of SiO2 coating exhibited higher interfacial resistance than noncoating because the thick SiO2 coating film acted as a high-resistance layer. Temperature dependence of the interfacial resistance suggests that the resistance decrease was achieved mainly by an increase of pre-exponential factor rather than by a decrease of activation energy for ion conduction at the interface. At room temperature, all-solid-state cells with Li2SiO3-coated LiCoO2 were discharged even under the high current density, 6.4 mA cm-2. [ABSTRACT FROM AUTHOR]

All‐solid‐state batteries attract significant attention owing to their potential to realize an energy storage system with high safety and energy density. In this paper, a mechanochemical synthesis of novel amorphous positive electrode materials of the Ni‐rich LiNi1−x−yMnxCoyO2 (NMC)–Li2SO4 system suitable for oxide‐type all‐solid‐state batteries is reported. Through the mechanochemical treatment with Li2SO4, excellent formabilities of the electrode materials as those of ductile solid electrolytes are obtained. Owing to the deformability of the active material, a good electrode/electrolyte interface is provided simply by pressing at room temperature. In all‐oxide solid‐state cells using 80NMCs·20Li2SO4 (mol%) positive electrode materials, the cell capacity increases with the Ni content in the NMC. The all‐solid‐state cell using the 80NMC811·20Li2SO4 positive electrode active material exhibits a high capacity larger than 250 mAh g−1 in a voltage range of 1.6–4.8 V versus Li at 100 °C. Furthermore, bulk‐type all‐oxide solid‐state batteries (Li4Ti5O12/80NMC532·20Li2SO4 (mol%)) successfully function as secondary batteries with excellent cycle performances. [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]

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]

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]

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]

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]

All-solid-state sodium secondary batteries have attracted significant attention as an alternative for post‑lithium-ion batteries. However, to obtain all-solid-state sodium secondary batteries with high-energy density, it is necessary to develop a high-capacity positive electrode material. In this study, two types of amorphous (a-)MoS x (x ≃ 6) active electrode materials were prepared using a mechanochemical (MC) process and through the thermal decomposition (TD) of (NH 4) 2 Mo 2 S 12 ·2H 2 O. Herein, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) analyses were conducted, and the results revealed significantly different local structures of a-MoS x (MC) and a-MoS x (TD). The all-solid-state sodium cells with a-MoS x (MC) and a-MoS x (TD) possessed high reversible capacities of 510 and 690 mAh g−1, as well as high-capacity retention rates of 80% and 92% for the 2nd to 30th cycles, respectively. XPS analysis of the discharge–charge products further suggested that dissociation and formation of disulfide bonds occurred reversibly during the discharge–charge reaction. This study shows that a-MoS x (MC) and a-MoS x (TD) are promising active electrode materials for all-solid-state sodium batteries. • Two types of amorphous MoSx were prepared using a mechanochemical process and through the thermal decomposition (TD). • All-solid-state sodium cells with amorphous MoSx possessed high reversible capacities of 690 mAh g−1. • Dissociation and formation of disulfide bonds occurred reversibly during the discharge–charge reaction. [ABSTRACT FROM AUTHOR]

A positive electrode containing Li 3 PS 4 (LPS) glasses and LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC) is a promising candidate for sulfide-based all-solid-state lithium batteries owing to its excellent charge–discharge cycle characteristics. However, sulfide-based solid electrolytes exhibit low chemical stability in air. This disadvantage affects process cost and thermal stability of all-solid-state cells. To resolve these issues, in this study, we focus on solid electrolytes, Li 4 SnS 4 (LSS), that do not generate H 2 S gas in air. The thermal behavior and microstructure of LSS–NMC positive electrode composites before and after the initial charge–discharge cycle are investigated. The initially charged LSS–NMC composites exhibit several exothermal reactions above 250 °C. However, pristine and initially discharged samples do not show any considerable exothermal reactions. For LPS–NMC composites, by contrast, exothermal reactions are detected regardless of the charging and discharging state. To clarify the exothermic factors of initially charged LSS–NMC composites, we performed ex situ transmission electron microscopy observation and X-ray diffraction measurements. It is determined that SnS 2 , transition metal sulfides, and metal oxides are formed above 300 °C, which is attributable to LSS and NMC decomposition reactions. On the basis of the relation between thermal behavior and corresponding structural changes, exothermic factors and thermal stability of LSS–NMC composites are discussed in comparison with LPS–NMC composites. • Li 4 SnS 4 –LiNi 1/3 Mn 1/3 Co 1/3 O 2 positive electrode composites are synthesized. • Exothermic factors and thermal stability of the composites are investigated. • The reactivity of Li 4 SnS 4 and LiNi 1/3 Mn 1/3 Co 1/3 O 2 during heating is low. • Li 4 SnS 4 –LiNi 1/3 Mn 1/3 Co 1/3 O 2 composites exhibit excellent thermal stability. [ABSTRACT FROM AUTHOR]