Mitigation of Self-Discharge of Lithium Sulfur Batteries by Functionalized Membranes and Electrolyte Additives

Lithium-sulfur (Li−S) batteries are considered as one of the most promising next geeration rechargeable batteries owing to their very high theoretical capacity of sulfur (S) cathodes (1672 mAhg^-1), low cost and environmental benignity. Nevertheless, the commercialization of this system is plagued by a number of serious problems, which include poor electronic conductivity of sulfur, volume change, shuttling of polysulfide and high self-discharge during dynamic and static conditions. These problems arise in large part from the dissolution, diffusion, and side-reaction of soluble lithium polysulfides in the electrolyte, formation of irreversible insoluble Li₂S and Li₂S₂ Although numerous studies have been focused on enhancing the conductivity of elemental sulfur only a few studies have been reported on the mitigation of lithium polysulfides and self-discharge.

The most commonly employed methods for preventing LiPS from shuttling are chemisorption, ion sieving, and electrostatic attraction/repulsion. The interlayer/permselective membrane not only prevents the lithium polysulfides from shuttling but also prevents self-discharge. Inorganic oxides, sulfides, and carbides have also been coated onto porous separators that provide adsorption sites for trapping LiPS. Researchers have explored inhibition of LiPS by electrostatic attraction and repulsion through the introduction of functionalized organic, and porous organic polymers. The importance of a permselective membrane/interlayer and the role of different electrolyte additives in enhancing the formation SEI layers, fire retardant properties have been systematically investigated. The self-discharge of Li- S cells were appreciably suppressed and are discussed.

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