Multifunctional Asymmetric Separator Constructed by Polyacrylonitrile-Derived Nanofibers for Lithium–Sulfur Batteries

Abstract

Lithium−sulfur (Li−S) batteries hold great promise as next-generation high-energy storage devices owing to the high theoretical specific capacity of sulfur, but polysulfide shuttling and lithium dendrite growth remain key challenges limiting cycling life. In this work, we propose a polyacrylonitrile-derived asymmetric (PDA) separator to enhance Li−S battery performance by accelerating sulfur redox kinetics and guiding lithium plating and stripping. A PDA separator was constructed from two layers: the cathode-facing side consists of polyacrylonitrile nanofibers carbonized at 800 °C and doped with titanium nitride, which can achieve rapid polysulfide conversion via electrocatalysis to suppress their shuttling; the anode-facing side consists of polyacrylonitrile oxidized at 280 °C, on which the abundant electronegative groups guide uniform lithium ion plating and stripping. Li−S batteries assembled with the PDA separator exhibited enhanced rate performance, cycling stability, and sulfur utilization, retaining 426 mA h g −1 capacity at 1 C over 1000 cycles and 632 mA h g −1 at 4 C over 200 cycles. Attractively, the PDA separator showed high thermal stability, which could mitigate the risk of internal short circuits and thermal runaway. This work demonstrates an original path to addressing the most critical issues with Li−S batteries.

Suppression of Polysulfides by Carbonized Polyacrylonitrile Modified Polypropylene Janus Separator for Li2S/r-GONR/CNT-Based Li–S Batteries

“…Recently, modified separators that could suppress PSs and facilitate Li + migration have been used to mitigate the shuttle effect. , This well-known method modifies the surface by coating functional materials as interlayers to enhance the electronic/ionic properties of the separator. , Compared with other materials, carbonaceous materials provide advantages, including current regulation, the provision of attachment absorption sites for soluble PSs, and PS reactivation. , Manthiram used a microporous carbon paper interlayer and a freestanding multiwalled CNT interlayer between the cathode and separator to improve the Li–S battery performance. , Similarly, graphene-treated carbon paper and carbon nanofibers have also been used to build interlayers owing to their superior electronic conductivity. Zhao used Ketjen Black, and Chung used Super P coated on one side of a polypropylene (PP) membrane, which showed high reversible capacity after a long-term cycling test.…”