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All‐solid‐state lithium‐sulfur batteries (ASSLSB), composed of sulfur cathode and lithium metal anode with high theoretical capacity, have a potentially higher energy density by weight than a typical lithium‐ion battery (LIB). However, due to insulating sulfur, a relatively large proportion of electronic (carbon) and ionic (solid electrolyte) conductors are mixed for cathode fabrication, leading to inferior practical capacity. Herein, we report a novel integrated cathode Li2S‐LiI‐MoS2 which has relatively high electronic and ionic conductivities (the order of 10−4 S cm−1) without any carbon and solid electrolyte. The ASSLSB with integrated Li2S‐LiI‐MoS2 cathode delivers a remarkably high energy density of 1020 Wh kg−1 at the cathode level at room temperature. By applying precise X‐ray diffraction, pair distribution function analysis and X‐ray computed tomography, it is found that the formation of an ionic conducting phase composed mainly of LiI during discharge is responsible for the high rate capability. Furthermore, X‐ray absorption fine structure (XAFS) has also revealed the charge compensation mechanism and ascertained the involvement of both Mo 3d and S 3p orbitals during the charging and discharging process. It is believed the strategy will pave the way for developing high practical energy density at room temperature for all‐solid‐state batteries. [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]

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]

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: 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: 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]

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]

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]

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]

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]

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]

In this study, we present a dry coating process to produce a core-shell composite particle for an all-solid-state lithium battery, where a single particle of the active material is coated with solid electrolytes. LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM) and Li 3 PS 4 (LPS), which are typical cathode active material and sulfide solid electrolyte, were used. A dry impact-blending device was employed for the dry coating process. We demonstrated that a single particle of NCM was uniformly coated with a continuous layer of LPS by the dry coating process without any breakage or attrition of NCM, to produce an NCM@LPS core-shell particle. The charge-discharge cycling tests showed that the rate and cycle performances of an all-solid-state half-cell prepared with the NCM@LPS core-shell particles significantly improved. The three-dimensional internal structure of the composite cathode was subsequently analyzed using FIB-SEM with an image reconstruction technique. The results revealed that the composite cathode prepared with the NCM@LPS core-shell particles had a (i) high interfacial contact area between NCM and LPS and (ii) well-percolated ion transport pathway. In conclusion, the core-shell composite particle contributed to the structure of the composite cathode, thus resulting in improved cell performance. Image 1 • Dry coating was used to produce a core-shell composite particle for an all-solid-state battery. • A single particle of NCM was uniformly coated with a continuous layer of Li 3 PS 4. • The cell performance significantly improved when using the core-shell composite particles. • A high NCM-Li 3 PS 4 contact area and well-percolated ion transport path were formed. [ABSTRACT FROM AUTHOR]