Understanding mesopore volume-enhanced extra-capacity: Optimizing mesoporous carbon for high-rate and long-life potassium-storage

The relationship between pore volume within pore structure and electrochemical performance is rarely studied, especially for potassium-ion batteries (PIBs). Herein, a series of porous carbon (MPC-Ts) with various pore structures including surface area, pore size and pore volume are fabricated in the closed autoclave by regulating the pressure medium and carbonization temperature. Combined with structural characterization, ex situ tests, electrochemical measurements and DFT calculations, it is demonstrated that the intercalation capacity is positively correlated with IG/ID ratio rather than interlayer distance, and adsorption capacity is positively correlated with mesopore volume rather than surface area or pore size. Mesopores can not only serve as active sites for potassium ion storage with low potential plateau but also promote ions migration and accommodate the huge volume expansion during (de)potassiation process. As a result, the optimized sample (APC-700) with the largest mesopore volume and appropriate surface area exhibits a high capacity of 633.2 mA h g(-1) at 50 mA g(-1), and maintains a reversible capacity of 263.9 mA h g(-1) at 1000 mA g(-1) after 1000 cycles. Even at 2000 mA g(-1) and 5000 mA h g(-1) after 10000 cycles, the capacities of 124.1 and 100.3 mA h g(-1) can still be obtained, respectively.