Carbon-nitrogen matrix encapsulated CoSn alloy anode with pseudocapacitive properties for advanced lithium-ion capacitors

Lithium-ion capacitors (LICs) represent a promising advancement in energy storage technology by combining the advantages of lithium-ion batteries and supercapacitors, offering superior energy/power density and long cycle life. However, one persistent challenge lies in kinetic mismatch between the Faradaic reaction of the anode and the surface adsorption/desorption reaction of the cathode. To address this issue, a carbon-nitrogen matrix encapsulated CoSn alloy (CoSn@NC) material derived from the carbonization of the CoSn-MOF precursor synthesized by a solvent-free method has been developed, which incorporates electrochemically inert element Co and an encapsulating of carbon-nitrogen matrix to effectively mitigate the volume expansion of Sn-based materials and improve the reaction kinetics. The resulting CoSn@NC exhibits a low lithium insertion potential, high pseudocapacitive contribution, and stable reversible capacity of 509.3 mAh g- 1 after 500 cycles at 500 mA g- 1, demonstrating excellent cycle stability and rate performance. Utilizing the CoSn@NC anode, the LIC achieves a high energy density of 148.8 Wh kg-1 (at 200 W kg- 1 ), a high power density of 16,000 W kg-1 (at 40.2 Wh kg- 1 ), and a capacity retention of 84.1 % after 8000 cycles.