Multi-scale uniform Li regulation triggered by tunable electric field distribution on oxygen-functionalized porous framework for flexible Li-S full batteries

Abstract

Lithium-sulfur (Li-S) batteries with high theoretical energy densities have long been identified a promising energy storage system. Nonetheless, it is not trivial to simultaneously achieve dendrite-free lithium metal anode and stable sulfur cathode for practical applications. To tackle this issue, we herein design an oxygen-functionalized mesoporous carbon nanofiber framework decorated with well-distributed nickel nanoparticles as bifunctional hosts for both electrodes. The combined theoretical and experimental results reveal that the regulated electric field stemming from the oxygenated and mesoporous structure can effectively facilitate the uniform nucleation and growth of dendrite-free Li metal in local nanofiber and whole electrode levels. Meanwhile, the strong affiliation of oxygenated groups to lithium polysulfides greatly alleviate the shuttle effect, leading to impressive cyclic stability. When coupling above optimal electrodes into a flexible Li-S full battery with an ultralow negative to positive capacity ratio of 2.0, the new battery presents remarkable electrochemical performance with a high rate capability of 882 mAh g−1 at 2.0 C and an extremely low capacity decay rate of 0.005% per cycle over 300 cycles. The stable electrochemical performance exhibited by a flexible Li-S battery under different mechanical deformations paves the way for future practical applications in flexible energy storage devices based on the bifunctional hosts.