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

4 years ago

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

Jianming Zheng, Xiaodi Ren, Brian D. Adams, Ji-Guang Zhang, Wu Xu

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. Electrochemical methods are developed to accurately measure the Coulombic efficiency (CE) of lithium metal anodes and lithium metal batteries. The amount of Li consumed during plating/stripping cycling is quantified and used to estimate the cycle life of Li metal batteries. With the proper electrolyte, Li metal can be cycled with a CE of 99.5% at high capacity.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/aenm.201702097