A general method for high-performance Li-ion battery Ge composites electrodes from ionic liquid electrodeposition without binders or conductive agents: The cases of CNTs, RGO and PEDOT

Abstract

High-capacity anode materials for lithium ion batteries (LIBs), such as Ge, generally suffer tremendous volume changes, as a result of the conversion reaction mechanism with Li, severely impede the high rate and cycling performance toward their practical application. In this article, we demonstrate a general LIBs Ge composites electrodes fabrication method using electrodeposition from room temperature ionic liquid. Our process is capable of forming composites electrodes with carbon nanotubes (CNTs), reduced graphene oxide (RGO), poly (3,4-ethylenedioxythiophene) (PEDOT), without the additives and conductive agents. During the electrodeposition process, Ge nanoparticles are integrated into the substrate network. Benefiting from the porosity, conductive network and mechanical stability constructed by interpenetrated compound layers, the hybrid system synergistically enhances the intrinsic properties of each component, yet is robust and flexible. The Ge/CNTs, Ge/RGO and Ge/PEDOT composites retain capacities of ∼851, 1212, and 1300 mAh/g after 200 cycles at 0.1 C. SEM analysis suggests that Ge/PEDOT composites have flower-like hierarchically porous structure, during cycling this structure transforms into a porous network, which can mitigate the physical strains during the Li uptake/release process, and increase the interfacial contact area with organic electrolyte. Consequently, the Ge/PEDOT composites demonstrate greatly enhanced rate capability without obvious capacity fading at high rate of up to 5 C.