PNNL

Abstract

Lithium (Li) dendrite formation is one of the critical challenges for rechargeable Li-metal batteries and Li-ion batteries, which has not been effectively solved by traditional methods. In this paper, we report the systematic investigation of a novel self-healing electrostatic shield (SHES) mechanism to change the Li deposition behavior by using low-concentration electrolyte additives whose redox potentials are close to that of Li+. The SHES additive cations force Li to be deposited in the region away from protuberant tips due to their preferentially accumulation on the active sites of anode surface. Typical adsorption behavior rather than electrochemical reduction of the additive cation is observed. The existence of Cs+ cations in the electrolytes does not change the components or structure of Li surface films, which is consistent with what the SHES mechanism predicts. The morphologies of deposited Li films on copper substrates are smooth and uniform during repeated deposition-stripping cycles and at various current densities (from 0.1 to 1.0 mA cm-2) by adding only a small amount of Cs+ additive in the electrolytes. Cs+-additive also suppresses Li dendrite growth on carbon anode surface during overcharging, which should improve the safety of Li-ion batteries during abuse conditions. It does not affect the rate capability but improves the long-term cycling stability of Li metal anode, carbon anode and conventional Li-ion cathode materials.