The Stability of Polymers in Liquid Li-S Battery

Abstract

Polymers have been widely employed as the binders, separators, separator modifiers and gel polymer electrolytes in lithium-sulfur batteries. Considering the special electrolyte system and discharge/charge mechanism, to verify whether the common polymer is applicable for Li-S battery is extremely necessary but often overlooked. In this paper the stability of some frequently-used polymersin the ether electrolyte(1 M LiTFSI + 0.2 MLiNO 3 /dioxolane (DOL) and 1,2-dimethoxyethane(DME) (1:1, v/v)) on the cycling and storage performances of Li-S batteryis examined by testing the solubility of the PEO, PVDF and PVDF-HFP particles/membranes in ether electrolyte and detecting the structure and composition changes of PVDF and PVDF-HFP membranes after cycling and storage as the separators of Li-S batteries. The results show that PEO particle and membrane both can dissolve in DOL and DME(1:1). PVDF and PVDF-HFP particles also dissolve in DOL and DME(1:1) but the membranes remain relatively stable, whereas PVDF-HFP react with Li 2 S x in liquid Li-S cellto form sulfone, which induce the crystalline phase transformation (from α-phase to γ-phase) and cystallinity decrease. PVDF can also react with Li 2 S x in liquid Li-S cell, but the action is less intensive than PVDF-HFP.

Styrene-co-DVB grafted PVDF proton exchange membranes for vanadium redox flow battery applications

“…The pores are not interconnected with each other as confirmed by the cross-sectional view of the membrane Fig. 1C and D. 44 The membrane was transparent in nature and no phase separation was found in it ( Fig. 2).…”

A Review of the Design of Advanced Binders for High‐Performance Batteries

“…Comparably, PEO was found to have an advantage over PVDF in terms of cycling stability and capacity utilization. However, the latest research reveals that the PEO is highly soluble in ether‐based electrolytes, [ 158 ] making it unsuitable for high sulfur loading. In addition, all three polymers mentioned above usually pair with NMP to prepare the slurry for the electrode coating.…”

Sulfur‐containing polymer cathode materials: From energy storage mechanism to energy density

“…The commonly used adhesives PVDF, PEO, and PTFE, 101 due to their small van der Waals force, will experience expansion and contraction of positive electrode volume in a long‐term cycle, leading to the separation of the active substance from the conductive agent and collector, and resulting in irreversible capacity loss and even the collapse of the electrode structure. Although the cycle stability and capacity retention ratio of PEO are better than that of PVDF, the high solubility of PEO in ether electrolyte also results in an unsatisfactory battery performance 102 …”

“…Although the cycle stability and capacity retention ratio of PEO are better than that of PVDF, the high solubility of PEO in ether electrolyte also results in an unsatisfactory battery performance. 102 F I G U R E 9 (A) Molecular structures of PVS and natural product of carrageenan and UV-vis spectra of PVDF, PVS and carrageenan, respectively, and (B) electrochemical performance of Li-S batteries of different electrodes based on PVDF, PVS, and carrageenan. Reproduced with permission.…”