The Effect of Crystalline Water on Lattice Transformation and Li ⁺ Diffusion Promotion in Halide Perovskite Anode Materials

Halide perovskite materials have garnered significant attention due to their outstanding optoelectronic properties; however, their development was limited by their low stability and lithium storage performance. In this study, CsMnCl3·2H2O and CsMnCl3 were synthesized via the solid-state synthesis method and selected to demonstrate the effects of crystalline water on their lattice transformation and electrochemical properties. The results indicate that the presence of crystalline water alters the Li+ insertion/extraction sites, thereby promoting Li+ insertion/extraction kinetics and lattice stability, resulting in the specific capacity of CsMnCl3·2H2O being 103.7 mAh·g–1, which is higher than the 57.7 mAh·g–1 of CsMnCl3 after 200 charge/discharge cycles, and the Coulombic efficiency of both approaching 100%. Besides, the density functional theory (DFT) calculations were used to demonstrate the influence of crystalline water on the halide perovskite lattice. This study not only opens new avenues for optimizing halide perovskite materials as high-performance lithium-ion battery anodes but also provides theoretical support for understanding the Li+ insertion sites in halide perovskite lattices for halide solid-state electrolytes.