Nitrogen-rich hard carbon as a highly durable anode for high-power potassium-ion batteries

Carbonaceous electrode materials for potassium-ion batteries (KIBs) are attractive due to the abundant resource of potassium and their rational capability. However, their rate capability and cycle life are mainly hindered by the intercalation chemistry involving repeated potassium insertion/extraction that are difficult to maintain within a short time or long-term cycling. Here, for the first time, a seafood waste (chitin)-derived hierarchically porous nitrogen-doped carbon microsphere (NCS) electrode with a surface-driven potassium storage mechanism is developed. The NCS electrode demonstrates a record high rate capability of 154 mA h g−1 at 72 C and ultralong cycle life of 4000 cycles without obvious capacity decay (180 mA h g−1 at 1.8 C), representing the best rate capability and longest cycle life among all electrodes in KIBs and even supassing most electrodes in sodium-ion batteries (NIBs). Further kinetic analysis and first-principle calculations reveal the dominated capacitive surface-driven mechanism of potassium storage in NCS, which is attributed to the hierarchically porous microstructure and nitrogen-doped carbon structure with enhanced potassium adsorption capability and electronic/ionic conductivities.