(Energy Technology Division Graduate Student Award) All-Graphene Energy Storage Device for High Energy and Power Density

Abstract

The prime importance in the energy storage field is to develop a new system that can combine high energy and power density. While lithium-ion batteries (LIBs) have become scientifically and commercially important because of their high energy densities, their power densities are not sufficient for emerging large-scale applications. Supercapacitors, on the other hand, are capable of delivering very high power due to their intrinsically fast surface-reaction mechanism, but they fail to meet high energy density requirements. This presentation proposes a new type of battery that adopts the fast surface reaction mechanism mimicking the supercapacitor without sacrificing energy density: an all-graphene energy storage device. The key advantages of an all-graphene energy storage device are that (i) both electrodes (a functionalized graphene cathode and a reduced graphene anode) exhibit fast surface reactions instead of intercalation while maintaining high energy density, and (ii) simple chemical modification of graphene yields either the anode or the cathode in a one-pot synthesis. Combined with controlled porous morphology and high electrical conductivity of graphene, the all-graphene energy storage device was capable of delivering a high energy of 195 Wh/kgtotal electrode, which is comparable to the energy density of conventional LIBs. The newly developed all-graphene energy storage device also retains 8.5 Wh/kgtotal electrode (energy) and 3,300 W/kgtotal electrode (power) at charge/discharge rates of just a few seconds. This energy and power performance perfectly spans the region that conventional LIBs and supercapacitors cannot reach. The performance and operating mechanism of an all-graphene energy storage device resemble those of both supercapacitors and batteries, blurring the conventional distinction between the two. This work sheds new light on the development of advanced energy-storage devices that bridge the performance gap between LIBs and supercapacitors. Presenting author: H. Kim E-mail: kimhaegyeom1@gmail.com Corresponding author: K. Kang E-mail: matlgen1@snu.ac.kr