Review of macroporous materials as electrochemical supercapacitor electrodes

Benefitting from excellent reversibility, high power density, and long cycle lifetime, electrochemical supercapacitors have become a versatile solution to meet the needs of various emerging energy storage applications. Their performances depend strongly on the properties of electrode materials. The composition, morphology, and structure are considered as the most important factors affecting the performances of electrode materials. Many previous review articles have discussed the research advances of some SC electrode materials with similar chemical compositions or microscopic morphologies. However, few review articles put their focus on the specific microstructures. Macropores, as a typical microstructure, can serve as ion-buffering reservoirs to minimize the diffusion distances of electrolyte. Thus, tremendous research efforts have been recently made to design and construct macropores for electrode materials to improve supercapacitive performance. Therefore, in this article, we review the recent developments of macroporous materials for SC applications, primarily including the preparation, microstructure, and performance of macroporous electrode materials. Typical five categories of macroporous electrode materials, including biomass-derived macroporous carbons, non-biomass-derived macroporous carbons, non-carbon-based macroporous materials, macroporous carbon-based composite materials, and active materials supported on macroporous substrates, are discussed in detail. Since mesopores can decrease ion-transport resistance, and micropores favor in-depth interfacial interactions, most porous electrode materials with excellent performance usually contain hierarchical porous structures consisting of macropores, mesopores, and micropores. Thus, the synergistic effects of hierarchical porous structures of various electrode materials are also indicated and summarized in this article. In addition, we also describe the influences of architecture’s several factors on the performance, and the differences in architecture of five categories of electrode materials. Finally, we present our perspectives on the challenges and prospects of macroporous electrode materials.