An ultraviolet polymerized 3D gel polymer electrolyte based on multi-walled carbon nanotubes doped double polymer matrices for lithium-sulfur batteries

Abstract

At present, the further evolution of liquid lithium-sulfur batteries (LSBs) is limited because there is no effective strategy to fundamentally solve the capacity decay caused by shuttle effect and the safety problems triggered by lithium dendrites. However, the application of gel polymer electrolytes (GPEs) to assemble quasi-solid-state LSBs opens up a novel research prospective to enhance the cycle life and security. Herein, we propose a 3D membrane, in which the ultraviolet polymerized pentaerythritol tetrakis-divinyl adipate (PETT-DA) serves as the in situ 3D network to simultaneously restrict lithium dendrite and shuttle effect, the long-chain poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) is the co-doped polymer to guarantee high ionic conductivity and toughness, and multi-walled carbon nanotubes (MWCNTs) act as the interactive nanofillers without the phenomenon of short circuit even when the content reaches 2.5 wt% because of the negligible electronic conductivity. More significantly, the intermolecular hydrogen bonds triggered by MWCNTs further reduce the crystallinity of the membrane, contributing to the superior performance of LSBs. Prominently, the designed 3D GPEs possess the increased Li+ transference number of 0.64 and superior ionic conductivity up to 1.1 × 10−3 S cm−1. Furthermore, the assembled LSBs exhibit stable cycling performance with the capacity retention of 85.4% after 300 cycles at 0.5 C, demonstrating the superior electrochemical performance.