钾离子混合电容器(PIHCs)作为一种新型的电化学储能器件, 因其低成本和丰富的资源而成为大规模储能技术的候选者之一. 然而, 钾离子较大的半径导致其迁移速率缓慢, 并且反复脱嵌过程易引发材料的结构坍塌, 限制了器件的应用. 因此, 开发出低成本的碳材料以实现快速的离子扩散和良好的循环稳定性已成为PIHCs当前发展的重要挑战. 本工作以价格低廉的煤沥青为碳材料前驱, 采用高温催化限域的策略制备出具有局部石墨畴结构的N/P共掺杂煤基碳材料, 并对其储钾性能和反应动力学进行探究. 研究表明: N/P共掺杂引入了丰富的缺陷, 可为K⁺的吸附/脱附提供大量的边缘活性位点, 与此同时, 催化生长的纳米石墨畴有利于电子和离子快速的传输. 得益于煤基碳材料中的局部石墨畴、富活性氮和缺陷网络结构的协同作用, 优化的NPC-800负极展现了优异的储钾能力(2 A•g⁻¹电流密度下具有196.3 mAh•g⁻¹的比容量)和循环稳定性(稳定循环1000圈). 此外, 采用商业化活性炭(AC)正极和NPC-800负极构筑的PIHCs (AC//NPC-800)能实现101.4 Wh•kg⁻¹的高能量密度和长循环稳定性(1000圈), 展现出良好的应用前景. 鉴于煤沥青和钾资源的丰富低廉性, 该工作为低成本煤基碳材料在二次电池以及电化学电容器中的应用提供了一种可行性策略.

Potassium-ion hybrid capacitors (PIHCs), as a new type of electrochemical energy storage device, have become one of the candidates for large-scale energy storage technology due to their low cost and abundant resources. Carbon-based materials exhibit excellent conductivity, chemical stability, abundant availability, and low cost, making them become the most promising anode materials used for PIHCs. Notably, introducting local nanographitic domains into heteroatom-doped and defect-rich carbon-based materials is expected to provide sufficient reactive sites and structural stability, together with maintaining good electrical conductivity and ion diffusion rate. However, the larger radius of potassium ions leads to slow migration rates, and the repeated intercalation and deintercalation processes easily cause structural collapse of the active material, which limits the application of the devices. In this regard, developing low-cost carbon materials to achieve rapid ion diffusion and good cyclic stability has become an important challenge for the current development of PIHCs. Herein, the N/P co-doped coal-based carbon materials with local graphitic domain structure were prepared with a high-temperature catalytic confinement strategy by using cheap coal pitch as the carbon precursor, and their potassium storage properties and reaction kinetics were investigated. The study shows that N/P dual doping introduced abundant defects, which provide a large number of edge-active sites for the adsorption/desorption of K⁺. Meanwhile, the catalytically grown nanoscale graphitic domains facilitate rapid electron and ion transport. Thanks to the synergistic effect of the localized graphitic domains, rich active nitrogen, and defect network structure in the coal-based carbon material, the optimized NPC-800 anode exhibits excellent potassium storage capability (a specific capacity of 196.3 mAh•g⁻¹ at current density of 2 A•g⁻¹) and cycling stability (1000 cycles). In addition, the assembled PIHCs (AC//NPC-800) with commercial activated carbon (AC) cathode and the NPC-800 anode achieves a high energy density of 101.4 Wh•kg⁻¹ and long cycling stability (1000 cycles), demonstrating its promising application prospects. Given the abundance and low cost of coal tar pitch and potassium resources, this work provides a feasible strategy for the application of low-cost coal-based carbon materials in secondary batteries and electrochemical capacitors.