Head-Mounted coating on graphite host enabling highly reversible Li Plating/Stripping in Lithium-ion/Lithium metal hybrid anode

Abstract

Commercial graphite hosting excessive Li is a promising hybrid Li-ion/Li metal anode for high energy battery. Nevertheless, the issue of Li plating on the top surface of the graphite anode (Gra) is not well tackled, resulting in the uncontrollable growth of Li dendrites and accumulation of “dead Li”, as well as the deactivation of graphite particles. In this work, an insulating ethylene vinyl alcohol copolymer (EVOH) layer is head-mounted covered on the graphite anode surface (Gra-OH) via a simple spray coating method. Due to the electron retarding ability of EVOH film, the top surface of the graphite host is passivated and the excessive Li can be well accommodated inside the porous structure of graphite host. Meanwhile, the lithiophilic –OH group of EVOH can regulate the Li+ flux and render the uniform Li plating behavior. Featuring these, the Gra-OH anodes with a Li storage capacity of 600 mAh/g show high Coulombic efficiencies (CEs) in both coin-cell and pouch cell even under carbonate electrolyte condition. When operating in Li-ion working mode, higher capacity retentions are readily achieved in the half-cell, full-cell and 5 Ah NCM811 pouch-cell, further demonstrating the application compatibility of this surface passivated Gra-OH anode.