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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]

Li2S is a promising cathode candidate for all-solid-state batteries (ASSBs) because of its high theoretical capacity and availability for coupling with a Li-free anode or an anode-less electrode. However, ionically insulating Li2S leads to excess conductive additives, low sulfur utilization and sluggish kinetics, which hinders the implementation of high energy density potential by ASSBs. Improving the intrinsic conductivity of Li2S is the key to solve this issue. In this study, PI3-doped Li2S cathodes were fabricated and the relationship between lithium vacancies and ionic conductivities was examined quantitatively by the time-of-flight (TOF) neutron diffraction. By cation–anion dual doping, the ionic conductivities of Li2S–PI3 materials were improved to 10−4 S cm−1, which is desirable for the cathode without solid electrolytes added. Upon simply mixing with carbon, the Li2S–PI3–C cathode shows a high overall cathode capacity of 541 mA h g−1 with a high S utilization of 82% at 0.05C and a capacity of 207 mA h g−1 at 1C at room temperature, realizing high energy density with good rate performance. [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]

The reaction uniformity of LiCoO2 composite positive electrodes in all-solid-state cells was compared quantitatively by investigating the Raman band shifts corresponding to the state-of-charge (SOC) of LiCoO2. The quantitative SOC analysis was conducted using the Raman imaging data of composite electrodes with smaller or larger solid electrolytes. The electrodes exhibited different reaction uniformity although the cells showed similar initial charge capacities and average SOC. In the case of larger solid electrolytes, most LiCoO2 particles showed higher or lower SOC than the average SOC, and lower battery performance. The quantitative analysis of SOC in each LiCoO2 electrode demonstrated that a variable SOC outside the average SOC resulted in larger irreversible capacity and lower rate performance. The quantitative SOC analysis newly developed in the present study is a useful technique for designing composite electrodes showing higher battery performance. [ABSTRACT FROM AUTHOR]

We report a route for the synthesis of Na3SbS4–Na2WS4 superionic conductors from aqueous solution. Na3SbS4–Na2WS4 has the highest high sodium-ion conductivity (4.28 mS cm−1 at 25 °C) of reported sulfide-based solid electrolytes prepared via liquid-phase methods. The antimony in Na3SbS4 is replaced by tungsten in a higher valence state, which is charge-compensated by sodium vacancies in the form Na3−xSb1−xWxS4. Introducing sodium vacancies while maintaining the 3D conduction pathways increases the pre-exponential factor in the Arrhenius plots of ionic conduction. The development of a facile synthetic protocol, as well as the high ionic conductivity and excellent chemical stability of Na3SbS4–Na2WS4 in the presence of water, is a major step towards the realization of all-solid-state sodium batteries. [ABSTRACT FROM AUTHOR]

Sulfide-based solid electrolytes with halide elements are essential components of advanced all-solid-state batteries. Argyrodite crystals are viable candidates as solid electrolytes for realizing all-solid-state batteries. However, a simple and effective route for the synthesis of these solid electrolytes is required. Herein, argyrodite Li6PS5Br superionic conductors were synthesized from a homogeneous solution by a liquid-phase technique. The Li6PS5Br solid electrolyte was prepared in a shorter synthesis time of one day using tetrahydrofuran and ethanol as compared with the solid-phase method. More importantly, of all the sulfide-based solid electrolytes prepared by liquid-phase techniques, Li6PS5Br showed the highest ionic conductivity of 3.1 mS cm−1 at 25 °C. The obtained particle size of 1 μm is suitable for application in all-solid-state cells. Moreover, coating electrode active materials with the solid electrolyte using the precursor solution led to a large contact area between the electrode and electrolyte and improved the cell performance. In addition, infiltrating a porous electrode with the precursor solution of the solid electrolyte is suitable for forming homogeneous composite electrodes to improve the cell performance. The all-solid-state cell using the Li6PS5Br fine powder with a high conductivity of 1 mS cm−1 or more exhibited a reversible capacity of 150 mA h g−1. This technique is effective for the industrial production of solid electrolytes and is applicable to all-solid-state batteries. [ABSTRACT FROM AUTHOR]

Mechanical properties such as formability and elastic moduli of solid electrolytes are important for the fabrication of all-solid-state batteries and retention of their charge–discharge capacities. In this paper, xNa2S·(100 −x)P2S5 (mol%) sulfide glass electrolytes (x = 50, 67, and 75) were prepared and their formability and elastic moduli were evaluated by an ultrasonic pulse-echo technique and a compression test under uniaxial pressing. The glasses were better densified and showed lower Young's moduli (15–19 GPa) than the Li2S–P2S5 glasses. [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 Li 3 PS 4 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 Li 3 PS 4 .

Understanding the differences in the structures and defects in the stable crystalline phase and metastable phase is important for increasing the ionic conductivities of a solid electrolyte. The metastable phase often has higher conductivity than the stable phase. In this study, metastable lithium thiogallate, Li 5 GaS 4 , was synthesized via mechanochemistry and stable Li 5 GaS 4 was obtained by heating the metastable phase. The metastable Li 5 GaS 4 sample was found to have an antifluorite-type crystal structure with cationic disorder, while the stable phase was found to have a monoclinic crystal structure, similar to that of another solid electrolyte, Li 5 AlS 4 . In both the structures, the Ga 3+ cations were surrounded by four S 2- anions in tetrahedral coordination. The conductivity of the metastable phase was determined to be 2.1 × 10 -5 S cm -1 at 25 °C, which is 1000 times greater than that of the monoclinic phase. The high conductivity of the metastable phase was achieved owing to cation disorder in the crystal structure., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)