Using a copper hyperaccumulator to synthesize anode and cathode materials for a high-energy 4.1 V full-carbon lithium-ion capacitor

Abstract Biomass-based porous carbons as electrode materials in asymmetric Li-ion capacitors (LICs) have shown broad prospect application. In this work, one kind of copper hyperaccumulator-elsholtzia splendens was selected as biomass source to synthesize micro-/nanoporous carbons to be used as both anode and cathodefor LICs due to the need of waste disposal. On the basis of separate charge storage mechanisms of anode and cathode in this system, corresponding strategies were adopted to rationally optimize the microstructure of micro-/nanoporous carbons to promote their electrochemical performance. Electrochemical tests showed that hierarchical porous carbon microsphere (PECS) anode exhibited an excellent rate capability (215.6 mA h g−1 at 2 A g-1) and a long lifespan (87.1% capacity retention over 1000 cycles). Carbon cathode with an ultrahigh specific surface area of 2819 m2 g-1 revealed a high specific capacity of 90.9 mA h g−1 at 5 A g-1. Benefiting from the high rate capability of anode and the high specific capacity of cathode, the as-assembled LIC delivered a high energy density of 129.4 W h kg−1 and 51.9 W h kg−1 at a power density of 205.5 W kg−1 and 10.3 kW kg−1.