Sulfur-Rich Sustainable Copolymers for Enhancing Redox Kinetics and Alleviating Cathode Passivation in Lithium-Sulfur...

Lithium-sulfur (Li-S) batteries are promising candidates for advanced energy storage systems. However, their performance is hindered by uncontrolled cathode passivation due to the formation of electronically insulating lithium sulfide (Li₂S). Here, we report a sulfur-rich copolymer, poly(sulfur-random-cardanol cystamine) [poly(S-r-Ccys)], as an efficient cathode material that enables spatially regulated Li₂S growth and improved redox kinetics. The nitrogen and oxygen functionalities in the Ccys moiety facilitate electrostatic interactions with lithium polysulfides, enhancing their dissolution and redistribution. Pulsed-field gradient nuclear magnetic resonance measurements confirm improved Li⁺ ion diffusion, while galvanostatic intermittent titration technique analysis reveals faster reaction kinetics in the poly(S-r-Ccys) cathode. The poly(S-r-Ccys) cathodes exhibit superior cycling stability compared to conventional elemental sulfur cathodes, maintaining 76.7% of their initial capacity after 300 cycles at 1 C, with a low average capacity fade of just 0.077% per cycle. This work demonstrates that poly(S-r-Ccys) offers a viable strategy to overcome Li₂S deposition challenges and improve the cycle life of Li-S batteries without altering the conventional ether-based electrolyte system.