A Structurally Flexible Halide Solid Electrolyte with High Ionic Conductivity and Air Processability

In this work, a structurally revivable, chloride-ion conducting solid electrolyte (SE), CsSn$_{0.9}$In$_{0.067}$Cl$_3$, with a high ionic conductivity of 3.45 × 10$^{−4}$ S cm$^{−1}$ at 25 °C is investigated. The impedance spectroscopy, density functional theory, solid-state $^{35}$Cl NMR, and electron paramagnetic resonance studies collectively reveal that the high Cl$^−$ ionic mobility originates in the flexibility of the structural building blocks, Sn/InCl$_6$ octahedra. The vacancy-dominated Cl$^−$ ion diffusion encompasses co-ordinated Sn/In(Cl) site displacements that depend on the exact stoichiometry, and are accompanied by changes in the local magnetic moments. Owing to these promising properties, the suitability of the CsSn$_{0.9}$In$_{0.067}$Cl$_3$, as an electrolyte is demonstrated by designing all-solid-state batteries, with different anodes and cathodes. The comparative investigation of interphases with Li, Li–In, Mg, and Ca anodes reveals different levels of reactivity and interphase formation. The CsSn$_{0.9}$In$_{0.067}$Cl$_3$ demonstrates an excellent humidity tolerance (up to 50% relative humidity) in ambient air, maintaining high structural integrity without compromises in ionic conductivity, which stands in contrast to commercial halide-based lithium conductors. The discovery of a halide perovskite conductor, with air processability and structure revival ability paves the way for the development of advanced air processable SEs, for next-generation batteries

KNi_0.8Co_0.2F₃ as an Efficient Electrocatalyst for Nonaqueous Li–O₂ Batteries

The rechargeable nonaqueous Li–O2 battery provides an ultrahigh theoretical energy density for energy storage application. However, its electrochemical performance is significantly hindered by numerous challenges including short cycle life, lower round-trip efficiency, and insulation caused by lithium peroxide (Li2O2) that results in a large overpotential. Utilizing known merits of fluoride perovskite structures and building on previous studies in an aqueous electrolyte, KNi0.8Co0.2F3 (KNCF82), shows promise as a Li–O2 battery electrocatalyst. When placed in a nonaqueous rechargeable Li–O2 battery, the KNCF82 cathode demonstrates an improved specific capacity of ∼9600 mA h g–1 at a current density of 175 mA g–1. The battery shows a cycling stability for 85 cycles with a narrow charge–discharge voltage difference of 1.41 V when the capacity was regulated at 500 mA g–1 and a round-trip efficiency of 63%. Further, despite a slight increase in overpotential, the cell exhibited good stability for 145 cycles and cycled over 835 h