In-situ constructing cathode protective film toward high performance of Li-S batteries at high sulfur loadings

Abstract

Shuttle effect of lithium polysulfide (LiPSs) and low sulfur loadings encumber practical application of Li-S batteries. Sulfur cathode coating is a direct and effective strategy to alleviate the problem. However, it is difficult for the available ex-situ coating to suppress shuttle effect at high sulfur surface loading. In the present work, diphenylamine (DPA) is used as an electrolyte additive, which can undergo electropolymerization and form an in-situ PDPA film on sulfur cathode, thereby inhibiting LiPSs diffusion. More importantly, computations and experiments prove that DPA-LiPSs complexes are formed in the electrolyte, increasing the solubility of LiPSs and improving the conversion kinetics. Benefit from the above, the capacity of DPA battery reaches 1029.5 mAh g−1 with sulfur loading of 3 mg cm−2 at 1 C rate, and keeps 762.1 mAh g−1 after 1000 cycles. Excellent cycling performance is achieved even at a high sulfur loading of up to 7 mg cm−2. This work provides a new strategy for suppressing the LiPSs shuttle effect under high sulfur surface loadings.