A high-sulfur-loading freestanding SPANI/MWCNT electrode for high-performance lithium–sulfur batteries

Abstract

Sulfurized polyaniline (SPANI) serves as a novel advanced cathode material that can chemically immobilize the sulfur active substance via robust intramolecular C–S bonding, thereby eliminating the shuttle effect in conventional lithium–sulfur battery systems. As a result, SPANI can exhibit commendable cycling stability and is compatible with commercial carbonate electrolytes. However, the conductivity of SPANI and its discharge product, Li₂S, is exceedingly low, severely hampering the discharge capacity of SPANI at high current rates. To solve this issue, a freestanding SPANI/MWCNT (multi-walled carbon nanotube) electrode with an internal three-dimensional conductive network structure has been successfully constructed for the first time. Compared to traditional coated SPANI electrodes, which deliver only 324.9 mAh g⁻¹ at a high rate of 8C (13 376 mA g⁻¹), the freestanding design enhances the capacity by approximately 1.5 times, reaching 480.5 mAh g⁻¹. Additionally, stemming from the robust mechanical property and the interwoven winding characteristic of MWCNTs, the electrode enables stable operation even with a high sulfur loading of 13.0 mg cm⁻², substantially exceeding the feasible limits of the traditional slurry-coating technique. Furthermore, this electrode demonstrates a consistent areal capacity reaching 8.30 mAh cm⁻² at a current density of 5 mA cm⁻², maintaining 86.4% of its original capacity after 100 charge–discharge cycles. Besides, the freestanding electrode craft can eradicate the need for expensive metal current collectors, binders, and the toxic binder dispersant NMP (1-methyl-2-pyrrolidinone).