High-performance carbon by amorphization and prepotassiation for potassium-ion battery anodes

Rechargeable K-ion batteries (KIBs) have attracted tremendous attention as a replacement for Li-ion batteries because potassium is earth-abundant and inexpensive. Although the formation of K-ion intercalated graphite compounds gives graphite a reasonable capacity, its capacity is insufficient, and its initial Coulombic efficiency (ICE) is low because of the slow kinetics of the large K ion. In this study, to address the shortcomings of graphite anodes for KIBs, we obtained a high-performance C-based anode by a simple, scalable two-step approach of amorphization and prepotassiation of carbon black (CB). CB was amorphized to provide numerous K-ion insertion sites and thus improve the K storage properties. However, the ICE and reversible capacity (RC) remained low. Therefore, to enhance the electrochemical performance, the amorphized CB (a-CB) was prepotassiated. The prepotassiated/amorphized CB showed a high RC (>300 mAh g−1) with an extraordinarily high ICE (>100%), high rate capability (255 mAh g−1 at 1C, 210 mAh g−1 at 2C), and remarkable cycling stability after 300 cycles at a high rate of 1C. Its electrochemical performance is among the best reported for C-based anode materials for KIBs, which suggests that it is a promising material for next-generation KIB anodes.