The Effects of Temperature and Lithium Polysulfides on the Composition of Lithium Cathodic Deposits Formed at a Steel Electrode

Abstract

The effect of lithium polysulfides on the amount and ratio of electrochemically active metallic lithium, electrochemically inactive metallic lithium, and chemically formed lithium compounds in the cathodic deposits formed on a stainless-steel electrode during galvanostatic cycling in 1 М LiClO₄ solution in sulfolane at 15, 30, 45, and 60°C is studied using the method we have developed earlier. It is shown that the increase in temperature leads to increase in the Coulomb efficiency of cycling and the amount of electrochemically active metallic lithium; a decrease in the amount of electrochemically inactive metallic lithium, regardless of the presence of lithium polysulfides in the electrolyte. When lithium polysulfides have been introduced into the electrolyte, an increase in the Coulomb efficiency of the metallic lithium cycling and a change in the ratio of various forms of lithium in the cathodic deposits toward an increase in electrochemically active lithium by about 1.5 times are observed. The lithium polysulfides are assumed to contribute to the dissolution of electrochemically inactive metallic lithium, forming an interfacial “sulfide” film at the electrode, which possessed high ionic conductivity and good protective properties, the more so, at elevated temperatures.