Sulfur–Carbon Electrode with PEO‐LiFSI‐PVDF Composite Coating for High‐Rate and Long‐Life Lithium–Sulfur Batteries
Ling Li, Jong Seok Nam, Min Soo Kim, Yifan Wang, Shaohua Jiang, Haoqing Hou, Il‐Doo Kim
Abstract
Abstract To address the problem of the serious capacity fading in lithium–sulfur batteries, a multi‐functional PEO(polyethylene oxide)/LiFSI (lithium bis(fluorosulfonyl)imide)/PVDF (polyvinylidene fluoride) (PLP) gel polymer electrolyte is exploited by coating PLP on a carbon nanotubes (CNTs) based sulfur cathode (PLP‐S/CNTs) with a controlled thermal annealing process. The annealing process leads to the conformal infusion of PLP through the matrix of S/CNTs with retaining the amorphous phase of the PLP, which enhance the rate performance compared to the bare S/CNTs. The PLP coating drives the transformation of more elemental sulfur to Li 2 S 2 /Li 2 S without forming intermediary product by restraining soluble‐polysulfides formation. Furthermore, the PLP coating successfully inhibits the dissolution of Li 2 S x ( x > 4) in PEO and prevents the loss of active material in the cathode, which is confirmed by density functional theory calculations. Comprehensively, the PLP coating applied to the surface of the S/CNTs cathode exhibit significantly suppressed shuttle effect and greatly improve long‐term cycle stability of the lithium–sulfur battery. The synthesized PLP‐coated S/CNTs composite cathode demonstrates a high specific capacity of 573.6 mAh g −1 at a current density of 0.5 C after 1 000 cycles, even achieving 318.1 mAh g −1 at an extremely high C‐rate (6 C). which is unprecedented performance among the reported studies on coating technology.