Mg‐Doped Porous Silicon Derived from Silica Aerogels for Fast and Stable Zinc‐Ion Hybrid Capacitors with High Capacitance

Abstract Zinc‐ion hybrid capacitors (ZICs) are of interest for their optimal balance between power and energy density. Among the cathode materials, silicon is particularly attractive due to its abundance and potential compatibility with the microelectronics industry. However, silicon‐based materials exhibit specific capacitances far below 100 mF cm −2 because of their inherently low electronic and ionic transport, making them less competitive than other nanomaterials such as carbon and MXenes. In this study, state‐of‐the‐art silicon‐based ZICs using Mg‐doped porous silicon (PSi) derived from silica aerogels are constructed. The improved electronic conductivity achieved by Mg doping, combined with enhanced ion diffusion promoted by the porous structure, results in excellent electrochemical properties of the ZIC. Consequently, the prepared ZIC exhibits a specific capacitance of 106.1 mF cm −2 at 0.2 mA cm −2 with remarkable cyclic stability (92% retention after 20 000 cycles). Additionally, the pouch ZICs using gel electrolytes demonstrate good rate capability and a long lifespan, indicating significant potential for practical applications. These results underscore the potential of heteroatom‐doped PSi as a cathode for ZICs.