Long-Life Lithium-Metal Batteries with Dendrite-Free Anodes Enabled by Zn(Tfsi)2 Additive

Abstract

The lithium-metal batteries (LMBs) have been regarded as the holy grail by using Li-metal as the anode in terms of the energy density. However, the uncontrollable lithium deposition, dendrite growth, and serious volume change upon repeated Li plating/stripping significantly limited the Coulombic efficiency and cycling life of the resulted batteries. Here, we developed a feasible strategy to enhance the cycle stability of Li anodes by introducing Zn(TFSI)2 as an electrolyte additive, with formation of LiZn alloy-coating layer through an in-situ reaction between Zn(TFSI)2 and the metallic lithium. The in-situ formed lithiophilic LiZn layers guided the homogeneous deposition of lithium and then prevented formation of dendrite and/or uncontrollable lithium deposition. By virtue of this Zn-salt additive, the LiZn coated Li anodes (LiZn/Li) showed an improved cycle stability and capability compared with the pristine Li anode. For example, a full cell with a NCM333 cathode and a LiZn/Li anode showed an impressive capacity retention ratio of 90.8% after 200 cycles at 200 mA g-1. This Zn-salt additive strategy provides a simple method for regulating formation of stable electrode-electrolyte interface with beneficial structure and low interface resistance for practical LMBs.

Keywords: Lithiophilic LiZn alloy, Zn(TFSI)2 additive, Dendrite suppression, Li-metal batteries