Cost-effective hard–soft carbon composite anodes with promising potassium ions storage performance

Abstract

Potassium-ion batteries (KIBs) are promising candidates as alternatives to lithium-ion batteries (LIBs) for large-scale energy storage due to the abundant potassium reserves and low cost. However, many well-established anode materials in LIBs are rarely suitable for KIBs. Herein, amorphous carbons including hard carbon, soft carbon and hard–soft carbon composites as KIBs anodes were systematically investigated. The synergy between hard carbon and soft carbon results in structure of relatively large interlayer distance, moderate defects and ordered carbon clusters, leading to excellent electrochemical performance. The hard–soft carbon composite with only 20 wt% hard carbon exhibits high reversible capacity of 376.8 mA h g−1 with a remarkable initial coulombic efficiency (ICE) of 71.04%, an excellent rate capability and a stable cycling performance for KIBs. In addition, full cells assembled with the obtained hard–soft composite as anode and Potassium Prussian blue (KPB) as cathode also exhibit an initial discharge capacity of 200.3 mA h g−1 at 100 mA g−1 and stable cycling performance (146.1 mA h g−1 after 100 cycles at a current density of 100 mA g−1). Owing to the great potential for practical applications, this work may appeal the development of cost-effective and sustainable carbonaceous materials for KIBs.