Accurate Determination of Coulombic Efficiency for Lithium Metal Anodes and Lithium Metal Batteries

TLDR

Lithium metal is an attractive high‑energy‑density anode, yet its low Coulombic efficiency and dendrite formation during repeated plating/stripping hinder practical use, and accurate CE measurement is critical but confounded by multiple factors that produce conflicting literature values. This study aims to identify the parameters that influence Li CE measurement and to develop a more accurate determination method. The authors systematically examined several experimental variables affecting CE and proposed a refined protocol for measuring Li CE. They found that higher cycling capacity accelerates stabilization and raises average CE, and that with a proper protocol the average CE can be increased from 99.0 % to 99.5 % at 6 mA h cm⁻² using a high‑concentration ether‑based electrolyte.

Abstract

Abstract Lithium (Li) metal is an ideal anode material for high energy density batteries. However, the low Coulombic efficiency (CE) and the formation of dendrites during repeated plating and stripping processes have hindered its applications in rechargeable Li metal batteries. The accurate measurement of Li CE is a critical factor to predict the cycle life of Li metal batteries, but the measurement of Li CE is affected by various factors that often lead to conflicting values reported in the literature. Here, several parameters that affect the measurement of Li CE are investigated and a more accurate method of determining Li CE is proposed. It is also found that the capacity used for cycling greatly affects the stabilization cycles and the average CE. A higher cycling capacity leads to faster stabilization of Li anode and a higher average CE. With a proper operating protocol, the average Li CE can be increased from 99.0% to 99.5% at a high capacity of 6 mA h cm −2 (which is suitable for practical applications) when a high‐concentration ether‐based electrolyte is used.