Graphene surface-enabled lithium ion-exchanging cells: next-generation high-power energy storage devices.

Herein reported is a fundamentally new strategy for the design of high-power and high energy-density devices. This approach is based on the exchange of lithium ions between the surfaces (not the bulk) of two nanostructured electrodes, completely obviating the need for lithium intercalation or deintercalation. In both electrodes, massive graphene surfaces in direct contact with liquid electrolyte are capable of rapidly and reversibly capturing lithium ions through surface adsorption and/or surface redox reaction. These devices, based on unoptimized materials and configuration, are already capable of storing an energy density of 160 Wh/kg(cell), which is 30 times higher than that (5 Wh/kg(cell)) of conventional symmetric supercapacitors and comparable to that of Li-ion batteries. They are also capable of delivering a power density of 100 kW/kg(cell), which is 10 times higher than that (10 kW/kg(cell)) of supercapacitors and 100 times higher than that (1 kW/kg(cell)) of Li-ion batteries.