Authors: Qi Li, Yibo Zhang, Zhengyu Chen, Jun Zhang, Ying Tao, Quan‐Hong Yang
Published: 2022-07-27
Source: Full article
AbstractGraphite has paved the way for commercial lithium‐ion batteries and shows great potential as an anode for high‐energy potassium‐ion batteries (PIBs) due to its low‐potential charge/discharge plateau. However, the restricted diffusion of large K+ in graphite causes difficulties in generating the stage‐one graphite‐intercalation compound (GIC) KC8 at high rates and results in a low plateau capacity and an inferior rate performance. It is discovered that the formation of high‐stage GICs (prior to KC24) is the rate‐controlling step of K+ intercalation, which is key to forming KC8. Here, a carbon anode material containing the medium‐size discrete graphitic crystallites is reported, produced by heating non‐graphitizable carbon above 2800 °C. This carbon anode material promotes the formation of KC8 due to the accelerated K+ diffusion especially at the rate‐controlling step and the sufficient reactive sites, which leads to a record‐high plateau capacity of 293 mAh g−1 and an excellent rate performance with 180 mAh g−1 at 500 mA g−1. For comparison, the respective values for graphite are only 242 and 51 mAh g−1. This study provides new insights into K+‐intercalation chemistry and shall promote the design of carbon anode materials for high‐energy and high‐power PIBs and even other energy storage systems.