Scalable fabrication of Ni(OH)2/carbon/polypropylene separators for high-performance Li-S batteries

Lithium-sulfur (Li-S) batteries are one of the most promising energy storage systems due to their attractive features of high energy density, low cost, and environmental friendliness. However, the shuttle effect of lithium polysulfides stays an obstacle for the further advancement of Li-S batteries. Herein, a novel Ni(OH) 2 /carbon/ Polypropylene(Ni(OH) 2 /C/PP) separator was prepared and applied in Li-S batteries to alleviate the shuttle issue. The Ni(OH) 2 /C/PP separator was constructed through vacuum filtration coating a super thin layer of super P(0.007 mg cm –2 ) on the Celgard 2325 followed by decorating the carbon layer with Ni(OH) 2 nanosheets film formed by a scalable gas-liquid diffusion method. Influence of Ni(OH) 2 /C on surface hydrophilicity, polysulfide permeability and catalytic effect on polysulfide conversion have been investigated. The results of contact angle, permeation test of Li 2 S 6 , XPS S2p spectra, symmetric Li 2 S 6 cells, Li + ion diffusion coefficient and Tafel slope confirmed that the Ni(OH) 2 /C/PP greatly improved the wettability for better penetration of electrolyte, lowered polysulfide permeability to retard its diffusion, and enhanced catalytic effect for the polysulfide conversion to boost the electrochemical kinetics. Thus, compared with the bare PP separator, the Ni(OH) 2 /C/PP separator enabled significantly increased capacity (1153 vs. 703 mAh g -1 at 0.2 C), greatly enhanced rate performance (816 vs. 381 mAh g -1 at 2 C) and satisfactory cyclability ( 0.10% decay rate after 500 cycles). This study provides a feasible separator modification approach for advanced Li-S batteries. • Large-area Ni(OH) 2 nanosheets film was prepared by a scalable gas-liquid diffusion method. • Micro-structured Ni(OH) 2 film@lightweight carbon layer (Ni(OH) 2 /C) decorated PP separator was prepared. • Ni(OH) 2 /C can accelerate the reversible conversion kinetics of polysulfides. • Li-S battery assembled with Ni(OH) 2 /C/PP separator shows good rate-performance.