Lithium–sulfur battery cathode with sulfurized bacterial cellulose and metal-coordinated polymers to strengthen stress and promote sulfur utilization

Abstract

Lithium–sulfur batteries (LSBs) have been attracting tremendous attention for their outstanding theoretical energy density, which can help to meet the demand for huge reservoirs of natural intermittent energy. However, the volumetric variations of sulfur species, severe shuttling of polysulfides, and sluggish kinetics of liquid–solid conversion lower the specific capacity and coulombic efficiency and shorten the battery lifetime. Conventional strategies for tackling these issues mainly center on confining sulfur species in highly porous hosts and buffering volumetric variations with spare space in the pores. However, the rigid inorganic nature of the hosts often leads to disorganized structures upon extended charge–discharge cycles. Herein, a sustainable biomass of bacterial cellulose (BC) is sulfurized as a novel composite active material in which the strengthened BC skeletons offer strong mechanical support to the LSB cathode. After coating with metal-coordinated polymers (BTA–Ni), the well-dispersed Ni nodes enable localization of the polysulfides and greatly expedite their reaction kinetics via electrocatalysis. As a result, the LSBs with BTA–Ni@BC/CNT cathodes deliver a high reversible capacity (1120 mAh g⁻¹ at 0.2 A g⁻¹) and decent rate capability (670 mAh g⁻¹ at 4.0 A g⁻¹). Moreover, the optimal BTA–Ni@BC/CNT specimen can retain a capacity of 680 mAh g⁻¹ after 700 cycles with an average coulombic efficiency of 99.03%. This work paves the way to fabricating higher-strength LSB cathodes with sufficient utilization of sulfur species.