Bifunctional tin modified SnO2 nanospheres embedded biomass-derived carbon network for polysulfides adsorption-conversion in lithium-sulfur batteries

Abstract

Lithium-sulfur batteries (LSBs) have been intensively studied as promising candidates of energy storage devices due to the high theoretical specific capacity. Unfortunately, the insulating nature and shuttling effect of sulfur are crucial obstacles. In this study, a “network-sphere” structure of in-situ reduced Sn modifying SnO2 nanospheres embedded in carbonized bacterial cellulose (CBC) porous nanofiber network (CBC@SnO2-Sn) is designed via two-step thermal treatment as 3D sulfur host material for LSBs to overcome these issues. The CBC exerts a positive role in alleviating the volume change as well as accelerating the electron and ion transfer. More significantly, the uniformly distributed SnO2 nanospheres with in-situ reduced Sn not only provide numerous active sites for chemisorption of polysulfides, but also accelerate the redox kinetics by catalyzing the polysulfides conversion, coordinately alleviating the shuttle effect during cycling. The CBC@SnO2-Sn/S cathode delivers an outstanding electrochemical performance with a high initial discharge capacity of 1573.6 mA h g−1 at 0.1 A g−1 and superior cycling stability (564.6 mA h g−1 after 500 cycles at 3 A g−1 with the coulombic efficiency kept above 99%). The novel structure, with synergy effect between conductive network and polysulfide adsorption-conversion, creates a promising strategy in improving the electrochemical performance for LSBs and other energy storage applications.