Li-Ion Storage and Diffusivity in Sulfurized Polybutadiene Containing Covalently Bound Sulfur as a Polysulfide Shuttle-Free Cathode Material for Li−S Batteries

Abstract

In this work, a new polymer has been explored as a cathode host for lithium-sulfur batteries (LSBs). Sulfurized polybutadiene materials were synthesized by a single-step, scalable, and easily tailored heat treatment method. The optimized synthesis process allows for high sulfur loadings of up to 50 wt %. Thermogravimetric analysis-mass spectrometry (TGA-MS) and X-ray photoelectron spectroscopy (XPS) studies confirm that the sulfur is covalently bound to the polymeric backbone, which overcomes the otherwise common capacity-fading polysulfide shuttle effect of lithium-sulfur (LSBs) batteries. The absence of free elemental sulfur in the synthesized active materials allows for a stable capacity of up to 1200 mAh g⁻¹ at a rate of C/20. The porous polymer networks reduce the pulverization of the cathode during cycling, resulting in long-term cycling stability of 1500 continuous galvanostatic charge/discharge (GCD) cycles. Capacity contribution studies depict that at a scan rate of 1 mV s⁻¹, the sulfurized polybutadiene cathode-based cells have 65 % capacitive and 35 % diffusive contribution of the total charge stored. A comprehensive study on Li-ion storage with capacity contribution and diffusion studies of polysulfide shuttle-free sulfurized polybutadiene cathode material for LSBs is presented.