Effect of the Quantity of Liquid Electrolyte on Self-Healing Electrostatic Shield Mechanism of CsPF6 Additive for Li Metal Anodes

Abstract

We used a cesium hexafluorophosphate (CsPF6)-containing liquid electrolyte for surface-patterned Li metal anodes and confirmed that there is a synergistic improvement in the electrochemical performance such as cycle performance and rate capability. For instance, the surface-patterned Li metal maintains 91.4% of the initial discharge capacity after the 1000th cycle (C/2 = 0.8 mA cm-2 for charging, 1C for discharging). When a large quantity of the CsPF6-containing liquid electrolyte (600 μL) is used, the bare Li metal and surface-patterned Li metal are more effectively stabilized in comparison with the case where 80 μL of electrolyte is used, resulting in improved electrochemical performance. Through systematic testing, we recognize that these results are because of the self-healing electrostatic shield mechanism, which is mainly dependent on the amount of Cs+ ions. A small amount of Cs+ ions cannot effectively counteract the incoming Li+ ions because they cannot form an effective electrostatic shield on the protrusions present on the Li metal surface. Copyright © 2019 American Chemical Society.