A Bandgap-Tuned Tetragonal Perovskite as Zero-Strain Anode for Potassium-Ion Batteries.

PIBs are emerging as a promising energy storage system due to high abundance of potassium resources and theoretical energy density, however, progress of PIBs is severely hindered by structural instability and poor cycling of anode material during continual insertion and extraction of larger-sized K. Hence, developing anode material with structural stability and stable cycling remains a great challenge. Herein, band gap-tuned Mo-doped and carbon-coated lead titanate (CMPTO) with zero-strain K storage is presented as ultra-stable PIBs anode. Mo doping introduces narrowed band gap and optimized crystal lattice for enhanced intrinsic electron and ion transfer. Demonstrated by in situ XRD characterizations, the crystal structure stays stable with unchanged peak positions, fully revealing zero-strain characteristic of CMPTO anode during potassium storage for stable cyclic capability. Ultimately, CMPTO anode achieved ultra-stable cycling performance of 7000 cycles at 500 mA g with high capacity retention of 90 % and considerable specific capacity of 130.9 mAh g after 600 cycles at 100 mA g; with relatively large density, CMPTO realized eminent volumetric capacity of 1111.09 mAh cm and ultra-long cycling life of 10000 cycles at 7041 mA cm. This work introduces a promisingly new route into developing anode materials with ultra-stable performance for PIBs.