New stepwise potentiostatic charge protocol for preventing dendrite formations in Li metal batteries

Abstract

Here, we report a new charge protocol for dendrite-free Li-metal battery based on the understanding the effects of over-potential on Li dendritic growth. We demonstrate that when a large over-potential is applied, the deposited Li metal shows a needle-like morphology even though a current density of a cell does not reach the limiting current density. This clearly indicates over-potential leads to the early formation of space charge region near a negative electrode, and thereby the Li dendritic growth can be easily triggered. As a result, control of the over-potential is very important for dendrite-free Li metal batteries. Through this understanding, we propose a new stepwise potentiostatic charge protocol that can keep the over-potential below a certain critical value. By applying new charge protocol, we clearly demonstrate that Ni-rich layered materials can be fully utilized without triggering the Li dendritic growth. The understanding and finding provide a novel guideline and stimulate further research to develop ways to safely operate high energy density Li metal battery.