Low-Cost and Sustainable Cross-Linked Polyvinyl Alcohol-Tartaric Acid Composite Binder for High-Performance Lithium-Sulfur Batteries

Abstract

A highspecific energy density in lithium-sulfur (Li-S)batteries can be achieved by constructing high-sulfur-loading electrodes.However, this electrode type leads to fast capacity decay owing tothe formation of large cracks on its surface. Consequently, the optimizationof polymeric binders is considered an effective strategy to decreasethe volume expansion of sulfur electrodes during cycling. In thisstudy, a three-dimensional (3D) cross-linked polymeric binder wasprepared via the polymerization of polyvinyl alcohol (PVA) and tartaricacid (TA). Acetylene carbon black (C) and elemental sulfur (S) weremixed and melt-diffused to prepare a CS composite. The developed 3Dcross-linked PVA-TA composite binder films exhibited improved breakingstrengths and swelling degrees. Moreover, the inter/intramolecularreactions between the hydroxyl groups of the PVA and TA moleculeseffectively reduced expansion and suppressed lithium polysulfides(LiPSs) during cycling. The synthesized composite binder also improvedthe adhesion of the active material and mechanical properties, whichdecreased the self-discharge and overpotential polarization and increasedthe lithium-ion diffusion coefficient. The CS electrode (78% sulfur,3.3-3.5 mg/cm(2) sulfur loading) with PVA-TA compositebinder exhibited a high initial discharge specific capacity of 537.7mAh/g and maintained 463.99 mAh/g after 400 cycles at 1.0 C-rate withthe decay rate of 0.14%. The outstanding electrochemical performanceis due to the 3D cross-linked polymeric network and the excellentadsorption ability. To the best of our knowledge, a sulfur electrodewith low-cost and sustainable 3D cross-linked PVA-TA composite binderwith excellent electrochemical properties was used for the first timein Li-S batteries.