Two-dimensional SnO₂ anchored biomass-derived carbon nanosheet anode for high-performance Li-ion capacitors

Lithium-ion capacitors (LICs) combine the advantages of both batteries and supercapacitors; they have attracted intensive attention among energy conversion and storage fields, and one of the key points of their research is the exploration of suitable battery-type electrode materials. Herein, a simple and low-cost strategy is proposed, in which SnO₂ particles are anchored on the conductive porous carbon nano-sheets (PCN) derived from coffee grounds. This method can inhibit the grain coarsening of Sn and the volume change of SnO₂ effectively, thus improving the electrochemical reversibility of the materials. In the lithium half cell (0-3.0 V vs. Li/Li⁺), the as-prepared SnO₂/PCN electrode yields a reversible capacity of 799 mA h g^-1 at 0.1 A g^-1 and decent long-term cyclability of 313 mA h g^-1 at 1 A g^-1 after 500 cycles. The excellent Li⁺ storage performance of SnO₂/PCN is beneficial from the hierarchical structure as well as the robust carbonaceous buffer layer. Besides, a LIC hybrid device with the as-prepared SnO₂/PCN anode exhibits outstanding energy and power density of 138 W h kg^-1 and 53 kW kg^-1 at a voltage window of 1.0-4.0 V. These promising results open up a new way to develop advanced anode materials with high rate and long life.