Electrochemical deposition and dissolution of lithium on a carbon fiber composite electrode in a solvate ionic liquid

Electrochemical deposition and dissolution of Li metal on a carbon fiber composite electrode were investigated in lithium bis(trifluoromethylsulfonyl)amide-tetraglyme solvate ionic liquid electrolyte. The carbon fiber composite coated on a Cu substrate was composed of vapor-grown carbon fiber (VGCF®-H) and poly(vinylidene fluoride). The coulombic efficiency for dissolution of Li deposits on the VGCF®-H modified Cu electrode was kept more than 98% at 100th cycle and higher than that on a Cu electrode in the solvate ionic liquid. Li was deposited in the porous structure of the VGCF®-H modified Cu electrode and scarcely observed on the surface of the VGCF®-H modified Cu probably because the overpotential for the reduction of Li is smaller on the Cu substrate and/or deposited Li than that on the cylindrical basal plane of VGCF®-H. This result suggests that the voids in the carbon fiber network effectively act as the Li deposition sites at the electrode|separator interface in the coin cell.