Li plating on alloy with superior electro-mechanical stability for high energy density anode-free batteries

Abstract

Anode-free batteries possess high energy density and avoid the use of reactive Li during battery fabrication, and thus are highly desirable for high energy density batteries. However, they encounter fast failure due to the inferior electrochemical reversibility. One main reason is the fast inactive Li accumulation caused by the coupling of side reactions and mechanics during complicated Li plating/stripping processes, among which, mechanical stability of plated Li on current collector is crucial but often ignored. To achieve good electro-mechanical stability, we construct a stable lithium-metal alloy interphase for Li plating, which sharps the Li deposition morphology and enhances the connection with deposited Li. The Li-metal alloy possesses reduced Li nucleation energy barrier and strong bonding with metallic Li, which enables dense and chunky Li deposits with firm connection with the substrate in sharp contrast the fully peeling off of metallic Li for bare Cu after 50 Li plating/stripping cycles. A Li-Sn alloy-modified Cu anode displays stable Li plating/stripping cycling with average Coulombic efficiency of 94.1% for 400 cycles at 1 mA cm–2 and 1 mAh cm–2, significantly outperforming the bare Cu electrode. As a demonstration, in an anode-free cell with Li rich Mn-based cathode, 16.7% increase in capacity and 14.1% increase in capacity retention for 20 cycles are achieved using alloy-modified anode. This sheds new insights on the improvement of dynamic mechanical stability between Li deposits and current collector by regulating Li plating and its connection with the current collector and guides the design of high-performance initial-Li-free anode.