Defective MoSSe with local-expanded structure for high-rate potassium ion battery

Potassium ion batteries with microparticulate electrodes promise a high volumetric capacity, yet they suffer from poor rate capacity and cyclic stability due to the long K+diffusion path and structural collapse upon K+ insertion/de-insertion. In this work, a local-expanded MoSSe material with wave structure is successfully constructed in a microparticulate state (labeled as LE-MoSSe). The high curvature design in this wave structure breaks the defect concentration limitation in MoSSe crystal, resulting in an abundance of surface active site with up to 29 % vacancy defects for S and 31 % for Se. Moreover, such a structure can adaptively and efficiently release internal stress during long-term repeated K+ insertion/de-insertion. Consequently, the LE-MoSSe material delivers a superior volumetric capacity (854 mAh cm−3), a record-high rate capability (19.3 C, ∼3 min), and a long cycle stability (only 0.039 % fading per cycle). This work demonstrates a practical approach to accelerate reaction kinetics and enhance structural stability of TMDs toward practical battery systems.