A reversible oxygen redox reaction in bulk-type all-solid-state batteries

An all-solid-state lithium battery using inorganic solid electrolytes requires safety assurance and improved energy density, both of which are issues in large-scale applications of lithium-ion batteries. Utilization of high-capacity lithium-excess electrode materials is effective for the further increase in energy density. However, they have never been applied to all-solid-state batteries. Operational difficulty of all-solid-state batteries using them generally lies in the construction of the electrode-electrolyte interface. By the amorphization of Li₂RuO₃ as a lithium-excess model material with Li₂SO₄, here, we have first demonstrated a reversible oxygen redox reaction in all-solid-state batteries. Amorphous nature of the Li₂RuO₃-Li₂SO₄ matrix enables inclusion of active material with high conductivity and ductility for achieving favorable interfaces with charge transfer capabilities, leading to the stable operation of all-solid-state batteries

Addition of Na3PO4 for Enhanced Positive Electrode Performance in All-Solid-State Sodium Batteries

All-solid-state sodium secondary batteries have attracted attention as next-generation batteries owing to their balanced performances in terms of energy density, battery life, abundant availability of sodium resources, and resulting cost reduction. For the positive electrode materials, NaFe0.5Mn0.5O2 is promising because it consists of abundant elements. However, its application in all-solid-state batteries with sulfide solid electrolytes are hindered by side reactions with the solid electrolytes, which lower the operating voltage. In this study, the electrode performances of all-solid-state sodium batteries were enhanced by mixing Na3PO4 with NaFe0.5Mn0.5O2 particles. Subsequent heat treatment further improved the electrode performance, resulting in an increased discharge voltage and a reversible capacity of 140 mAh g−1

Mechanochemical Synthesis and Characterization of Metastable Hexagonal Li₄SnS₄ Solid Electrolyte

A new crystalline lithium-ion conducting material, Li₄SnS₄ with an <i>ortho</i>-composition, was prepared by a mechanochemical technique and subsequent heat treatment. Synchrotron X-ray powder diffraction was used to analyze the crystal structure, revealing a space group of <i>P</i>6₃/<i>mmc</i> and cell parameters of <i>a</i> = 4.01254(4) Å and <i>c</i> = 6.39076(8) Å. Analysis of a heat-treated hexagonal Li₄SnS₄ sample revealed that both lithium and tin occupied either of two adjacent tetrahedral sites, resulting in fractional occupation of the tetrahedral site (Li, 0.375; Sn, 0.125). The heat-treated hexagonal Li₄SnS₄ had an ionic conductivity of 1.1 × 10^–4 S cm^–1 at room temperature and a conduction activation energy of 32 kJ mol^–1. Moreover, the heat-treated Li₄SnS₄ exhibited a higher chemical stability in air than the Li₃PS₄ glass-ceramic