Decoupling Lithium Reutilization Behavior under Different Discharge Rates for Anode-Free Lithium Metal Batteries

Abstract

Anode-free lithium metal battery (AFLMB) has become an excellent candidate for long endurance electric vehicles and electric low altitude aircraft, profiting from its high energy density as well as outstanding manufacturing safety. However, the limitation at high discharge rates of AFLMBs is shrouded in mystery, yet to achieve more attention. Herein, the limitation of fast discharge for AFLMBs is dissected exhaustively, and a symptomatic strategy to break the limit is put forward, in order to eliminate the inevitable mismatch that lies in the inferior performance of AFLMBs. A “volcano-type” curve of capacity retention of AFLMBs is discovered with the discharge rate increased. Systematic investigation revealed that the overlapped spatial relationship between fresh deposited Li and residue Li⁰ facilitated the utilization of “recoverable Li⁰” (Li⁰) at the prophase of discharge rate increase. However, further enhanced discharge rate induced large concentration polarization (η_conc), reflecting limited Li⁺ diffusion. Enabling the electrolyte to rapidly transport Li⁺ by lowering η_conc increased the optimal discharge rate as well as the cycling stability of AFLMBs. This work reveals the rate-determining step for high-rate discharge and expands the employment boundary of AFLMBs under harsh conditions, providing a significant complement of present knowledge with respect to the power performance of AFLMBs.