Manipulating kinetics of sulfurized polyacrylonitrile with tellurium as eutectic accelerator to prevent polysulfide dissolution in lithium-sulfur battery under dissolution-deposition mechanism

摘要

Employing "solid-state" mechanism can avoid polysulfides dissolution in lithium-sulfur batteries but lead to limited reactivity. It is desirable to eliminate polysulfides dissolution under "dissolution-deposition" mechanism but merely impossible with S-8 due to its intrisic parasitic reaction pathway. However, sulfurized polyacrylonitrile (S@pPAN) is suggested to involve S3-4 and soluble intermediates Li2S3-4, thus a fast and reversible conversion to insoluble Li2S2 and Li2S can avoid dissolution. Herein, Te is used as eutectic accelerator in S@pPAN to accelerate the redox conversion and prevent polysulfides dissolution under "dissolution-deposition" mechanism. In TexS1-x@pPAN (Te-doped S@pPAN) cathodes, Te can be uniformly distributed through Te-S bond and accelerate the reactivity while contribute capacity, resulting in compatiblity with both ether and carbonate electrolytes, high capacities of 1507 and 861 mA h g(-1) at 0.1 and 10 A g(-1), and stable cyling over 600 cycles in ether electrolyte (0.05% decay per cycle). Good performance is also demonstrated with 3.11 mg cm(-2) sulfur loading and 6 mu L mg(-1) electrolyte/sulfur ratio. Further studies confirm that Te promotes the diffusion of Li ion and reduces reaction resistance during charge/discharge process, which affords significantly enhanced reaction kinetics and mitigates polysulfides dissolution. This work shows a high performance lithium-sulfur batteries operated under "dissolution-deposition" without polysulfides dissolution.