Enhanced capacity of aluminum-ion batteries by adjusting the average pore size of the porous carbon cathode

Lithium-ion batteries (LIBs) are widely used but with the increasing scarcity and uneven distribution of global lithium resources, there is a need to explore alternative battery technologies. Due to its abundance, low cost, and high theoretical capacity, aluminum is a strong candidate for metal anodes, making aluminum-ion batteries (AIBs) an area of considerable interest. Current mainstream research focuses on ionic liquid electrolytes, which offer a wide electrochemical window and high ionic conductivity. Carbon materials are ideal cathode candidates due to their low cost, abundance, and high voltage platform. AIBs using carbon materials typically exhibit low discharge capacity. This study addressed the challenge of improving the discharge capacity of carbon-based cathodes in AIBs. By using porous carbon (PC) materials with varying specific surface areas, average pore sizes, and total pore volumes as cathodes, average pore size was found to impact capacity. This contradicts the contention that larger specific surface areas result in higher capacities. There is a key difference in ion behavior: whereas aluminum chloride ions intercalate into layered graphite structures, they do not intercalate into PC materials but are adsorbed to the surface. By adjusting the average pore size, it is possible to increase the discharge capacity of AIBs, challenging the traditional emphasis on specific surface area. This research does not fully solve the problem of low discharge capacity in carbon-based cathodes, but provides a new perspective on the role of pore size in enhancing battery performance, offering valuable insights for future electrode design.