Stability of Li Metal Anode in Li-S Batteries

Abstract

Because of its high energy density and promising potential to revolutionize the future electric energy storage systems, the technology of Li-S batteries has attracted significant interests in recent years. With the significant progresses made on the development of cathode materials in lithium-sulfur (Li-S) batteries, the stability of anode in Li-S batteries has become one of the more urgent challenges in order to reach the long-term stability of Li-S batteries. Lithium metal is the preferential option for the anode material in Li-S batteries because of its high specific capacity. However, lithium polysulfides formed during discharge and charge processes may migrate from cathode to anode side to react with the lithium metal, so called shuttle problem, leading to limited cycle life and poor Coulombic efficiency of Li-S batteries. A passivation layer is easily formed on the metallic Li anode surface because of the presence of polysulfides and electrolyte additives, which is supposed to corrode Li anode and result in failure of the Li-S battery. Various strategies used to minimize the corrosion of Li anode and to reduce its impedance increase have been developed, including electrolyte additives, polymer electrolytes and interlayers. Recently, concentrated electrolytes were demonstrated to offer lower solubility of polysulfides and could lead to more stable cycling stability in Li-S batteries. Concentrated electrolytes tend to reduce the solubility of lithium polysulfides due to the lack of available solvent to partially solvate the Li+ cations. Coordinating anions also affect the solubility of lithium polysulfides through interacting with the Li+ cations with different solvation strength. In this presentation, the failure mechanism and the stability of anode/electrolyte interface in Li-S batteries with highly concentrated electrolyte will be reported.