A critical review on the application and recent developments of post-modified biochar in supercapacitors

The demand for sustainable and renewable energy sources has gained tremendous research attention around the world over the past years. Supercapacitor, among lots of energy storage devices, has been attracted many researches for the advantages of high power density, fast charge-discharge capability and cycle stability. Compared with other carbon materials, biochar materials have attracted special attention as efficient, low-cost, active materials for energy storage. In this work, the typical preparation and modification methods of biochar as the supercapacitor electrode are classified. the factors influencing the electrochemical performance of biochar, such as specific surface area (SSA), pore structure, surface chemical modification and conductivity are systematically discussed. This work studied the relationship between carbon with mesopore and hierarchical pore structure and the electrochemical performance of biochar electrode materials. The advantages and disadvantages of introducing heteroatoms and functional materials on the surface of biochar for supercapacitor electrode are analyzed. Meanwhile, future development trends for biochar materials in this field are also prospected. • Structural characteristics of biochar affecting electrochemical performance are analyzed. • The modification methods of post-modification biochar are classified and discussed. • Recent applications of post-modification biochar in supercapacitors are reviewed. • Common characteristics of biochar-based electrode materials are summarized. • Future development of the biochar electrode materials are proposed.