Stress-tolerant sulfur cathode with a super-stretchable polymer coating via initiated chemical vapor deposition

The mechanical deterioration of the sulfur cathode during cycling from repeated voltage changes is a limiting factor of the cycling stability of lithium-sulfur batteries. Herein, we present a stress-tolerant sulfur cathode by conformally coating the surface with a super-stretchable thin polymer layer via an initiated chemical vapor deposition method. A layer tens of nanometers thick is formed in the sulfur cathode via the copolymerization of hydroxyethyl acrylate and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane in a gas-phase reaction, and its mechanical properties are tuned by varying the copolymer composition. In comparison with a bare sulfur cathode, which exhibited cracking after cycling, the sulfur cathode with an optimized polymer layer exhibited a crack-free morphology and showed significantly improved cycling stability owing to its high elastic modulus and high elongation at break. Furthermore, the coating reduced the polysulfide shuttle current, demonstrating its function as a polysulfide-blocking layer. This super-stretchable polymer coating provides a unique platform for mechanically robust and high-performance sulfur cathodes. The mechanical instability of sulfur cathodes limits the cycling stability of lithium-sulfur batteries. Here, a stress-tolerant sulfur cathode is achieved by applying a super-stretchable polymer coating via chemical vapor deposition, enhancing cycling stability and reducing polysulfide shuttle