Modification of LiMnO Cathodes to Boost Kinetics Match via rGO for High-Performance Rocking-Chair Lithium-Ion Capacitors.

The rocking-chair lithium-ion capacitors (RLICs), composed of a battery-type cathode and capacitive-type anode, alleviates the issue of increased internal resistance caused by electrolyte consumption during the cycling process of the lithium-ion capacitors (LICs). However, the poor conductivity of cathode materials and the mismatch between the cathode and anode are the key issues that hinder its commercial application. In this work, a modification simplification strategy is proposed to tailor the conductivity of the cathode and matching characteristic with the anode. The in situ grown lithium manganate (LMO) is featured with a three-dimensional conductive network constructed by reduced graphene oxide (rGO). The optimized LMO/rGO composite cathode demonstrates an excellent rate performance, lithium-ion diffusion rate, and cycling performance. After assembling an RLICs with activated carbon (AC), the RLICs exhibits an energy density of as high as 239.11 Wh/kg at a power density of 400 W/kg. Even at a power density of 200 kW/kg, its energy density can maintain at 39.9 Wh/kg. These excellent electrochemical performances are mainly attributed to the compounding of LMO with rGO, which not only improves the conductivity of the cathode but also realizes a better matching with the capacitive-type anode. This modification strategy provides a reference for the further development of energy storage devices suitable for actual production conditions and application scenarios.