Research progress of carbon cathode materials for zinc-ion capacitors

Zinc-ion capacitors have now become a popular research direction in the energy storage direction by virtue of the abundant natural resources of zinc, high theoretical capacity, and excellent safety. Carbon-based materials are often used as cathode materials for zinc-ion capacitors due to their rich microstructure, low cost, high chemical stability, and good electrical conductivity, but their use in some aspects is limited by the fact that the energy storage mechanism of double capacitors cannot provide sufficient energy. In this review, the advantages and disadvantages of several commonly used methods for preparing carbon-based materials are first discussed, followed by a summary of methods to improve the energy and power density of carbon-based materials by changing their structure and composition. In addition, the application of zinc-ion carbon cathode materials in flexible capacitors and the problems thereof are introduced, and finally, some outlooks on the direction of improvement of zinc-ion capacitors are given.