Comparative Study on the Microstructure and Electrochemical Properties of Distilled Grains Derived Hard Carbon as Anode for Potassium Ion Batteries: Effect of Carbonization Temperature

The design and preparation of novel carbon electrodes are the key to the development of potassium ion batteries (PIBs). The unique short-range ordered graphene sheet and defective amorphous domain composite structure of hard carbon (HC) provide favorable support for the storage and adsorption of potassium ions. In this paper, derived biomass carbons (DBCs) as a HC material were prepared by simple two-step carbonization of pre-carbonized at 500 °C and the graphitization transformation at a higher carbonization temperature employing the distilled grain biomass as a carbon source. The effect of carbonization temperature at the second step on the surface structure and electrochemical performance of the DBCs applied in PIBs were checked. It was found that 900 °C of carbonization temperature was favored for the formation of DBCs with a proper degree of graphitization, large lattice spacing (3.55 Å), and large specific surface area (111.9 m2/g−1). Ascribed to the microstructural advantage, the DBC-900 based PIBs displayed astonishing potassium storage capacity (160.5 mAh/g at 50 mA/g) and extremely low-capacity attenuation (0.041% per cycle at 50 mA/g after 800 cycles). This work not only provides a kind of HC materials with low-cost and easy preparation for PIBs, but also offers a way for the application of distilled grains.