Uniform carbon coating and solid electrolyte interphase synergistically enhanced exceptional anodic K-ion storage properties of stable KTiOPO4 single crystals

Searching for low-cost, high-capacity, high-power, high-stability, high-tap-density, and inherently safe materials for developing cheap, safe, and high-performance batteries has always been a research hotspot. Herein, an inherently safe, low-cost, and low-strain KTiOPO₄ (KTOP) submicron single crystals with a uniform thin layer carbon coating are developed using a ball-mill assisted solid-state method. Uniform solid electrolyte interphase, carbon coating, and inherently stable structure synergistically help compact KTOP submicron single crystals achieve an exceptional anodic K-ion storage performance. The carbon-coated KTOP single crystals obtained under the carbonization temperature of 400°C (KTOP-C-400) can deliver an exceptional potassium ion storage performance of 253.3, 224.0, 175.5, and 131.1 mA h g⁻¹ at the current density of 100, 200, 500, and 1000 mA g⁻¹, respectively, in the electrolyte of 5 M potassium bis(fluorosulfonyl)imide (KFSI) in DIGLYME electrolytes. Even after being cycled at 1000 mA g⁻¹ for 1000 cycles, the capacity was maintained at 182.5 mA h g⁻¹ with a coulombic efficiency of 99.9%.