Self-formed carbon layer on calcium Metal-organic framework and rGO composite with High-stable K-storage performance in K-ion batteries

Potassium ion (K-ion) batteries are expected to be utilized as potential energy storage devices to replace the commercialized lithium ion (Li-ion) batteries in the upcoming large-scale system due to their abundant potassium resources as well as fast ion transport capability. Nevertheless, developing superior anode materials that can store K+ with a large ion radius has been the hotspot and leading edge. Herein, a self-formed carbon layer on calcium metal–organic framework and rGO composite with high-stable K-storage performance was initially introduced as an advanced anode material for K-ion battery. Due to the in-situ formed carbon coating layer on the surface by proper thermal treatment, the highly stable crystal structure and molecule structure of CaC8H4O4, as well as enhanced electronic conductivity from the two-dimentional rGO, the as-prepared CaC8H4O4/rGO-450 composite could exhibit excellent cyclic stability and rapid electrochemical reaction rate with a reversible capacity of 110 mAh g−1 over 700 cycles at the current density of 100 mAg−1. This work provides guidelines for the further realization of the preparation of K-ion battery anode materials with a fast electrochemical reaction rate, high rate and long life.