Confined graphitization induced pore generation for designing novel potassium-ion battery carbon anode with large capacity and ultra-long cycle life

Carbon is one of the most superior anode materials for K-ion batteries but faces the challenges of low capacity and poor cycle stability. In general, the K+ storage capacity depends on the graphitized carbon layers and defective structure, while the cycle stability can be enhanced by constructing sufficient nanospace to alleviate the volume expansion during the potassiation/depotassiation process. However, the above structures are difficult to integrate into a single carbon material because graphitization often eliminates defects and pore structures. In this work, we find that ultrathin carbon sheets have a confined graphitization effect, which allows the carbon layer to orientationally arrange at a low heating-treatment temperature. More importantly, this orientational arrangement causes size shrinkage, inducing structural splitting on the faces of the carbon sheets and producing abundant defects and a large number of pores. Based on this, we obtain a novel carbon with highly graphitized, large-surface-area and defect-rich frameworks, which gives a K+ storage capacity of 358 mAh g−1, and after 4000 cycles, this carbon shows no obvious capacity degradation, with a capacity retention rate of nearly 100 %. Carbon anodes of K-ion batteries with such large capacity and long cycling life have rarely been achieved before.