Rational regulation of defect-rich hierarchical porous carbon nanosheets as sustainable anode materials for potassium-ion storage

Potassium-ion storage devices are the most promising equipment for large-scale energy storage due to their low cost and abundant resource. However, the low rate and poor cycling ability of potassium-ion energy storage devices resulting from the dramatic structure changes of electrode materials during operation limit their development. Herein, a defect-rich hierarchical porous carbon nanosheets (HPCS) is successfully synthesized via a facile Mg(OH)2 template approach with low-cost coal tar pitch as carbon precursor. The ultrathin nanosheets framework with a porous structure not only accelerates the rapid infiltration of electrolyte, but also alleviates the volume expansion upon cycling. Benefiting from its unique microstructure, the optimized HPCS-900 exhibits excellent rate performance (156.2 mAh g−1 at 1 A g−1) and cycling stability (130.1 mAh g−1 at 1 A g−1 after 1000 cycles). As a practical device application, the assembled potassium-ion capacitors (HPCS//AC) deliver a high energy density of 130 Wh kg−1 and a maximum power density of 10,735 W kg−1. This work provides an exciting approach to designing advanced defect-structured carbon-based materials for high-performance potassium-ion batteries and capacitors.