Potassium-ion capacitors (PICs) are promising energy storage devices, which are competitive with lithium-ion and sodium ion capacitors. PICs combine the advantages of a battery-type anode and a capacitive cathode, resulting in a low cost, high energy density, high power density and long cycle life. However, there is still a mismatch between the anode and cathode materials for achieving the optimum specific capacity and kinetics in PICs. Early studies have shown that the careful selection of electrode materials and their optimization is an effective way to solve this problem. We focus on the development of PIC anode materials including insertion-type and conversion-type materials. The insertion-type materials include carbon materials (graphite, soft carbons, hard carbons, etc.), K-based titanates, MXenes, and dipotassium terephthalate. The conversion-type materials include metal sulfides/selenides, metal phosphides and sodium super ionic conductor-type phosphates (NASICON). Their preparation, structural characteristics, electrochemical performance as anode materials in half-cell and PIC devices are summarized and discussed. The future prospects and challenges of PICs are also considered.

钾离子电容器（PIC）是有前途的储能设备，可与锂离子和钠离子电容器竞争。PIC结合了电池型阳极和电容性阴极的优势，从而实现了低成本，高能量密度，高功率密度和长循环寿命。但是，阳极材料和阴极材料之间仍然存在不匹配，无法在PIC中实现最佳的比容量和动力学。早期研究表明，精心选择电极材料及其优化方法是解决此问题的有效方法。我们专注于PIC阳极材料的开发，包括插入型和转换型材料。插入型材料包括碳材料（石墨，软碳，硬碳等），K基钛酸酯，MXenes和对苯二甲酸二钾。转化型材料包括金属硫化物/硒化物，金属磷化物和钠超离子导体型磷酸盐（NASICON）。总结和讨论了它们的制备，结构特征，作为半电池和PIC器件阳极材料的电化学性能。同时也考虑了事先知情同意的未来前景和挑战。