Room-temperature Operation of All-solid-state Chloride-ion Battery with Perovskite-type CsSn<sub>0.95</sub>Mn<sub>0.05</sub>Cl<sub>3</sub> as a Solid Electrolyte

Perovskite-type CsSnCl3 is an attractive candidate for use as a solid electrolyte in all-solid-state chloride-ion batteries because it exhibits high ionic conductivity. However, perovskite-type CsSnCl3 is metastable at room temperature and easily undergoes a phase transition to a stable phase. Here, we prepared perovskite-type CsSn0.95Mn0.05Cl3, in which the Sn2+ in CsSnCl3 is partly substituted with Mn2+, via a mechanical milling method. Differential scanning calorimetry showed that the perovskite-type CsSn0.95Mn0.05Cl3 is stable to −15 °C. Moreover, it exhibits a high chloride ionic conductivity of 2.0 × 10−4 S cm−1 at 25 °C. We demonstrated the room-temperature operation of an all-solid-state chloride-ion battery with a BiCl3 cathode, an Sn anode, and CsSn0.95Mn0.05Cl3 as the electrolyte. The first discharge capacity of the all-solid-state cell at room temperature was 169 mAh g−1 based on the weight of BiCl3. X-ray diffraction and X-ray photoelectron spectroscopic analyses confirmed that the reaction mechanism of the cell is derived from the redox reaction of BiCl3 and Sn.