Graphene oxide wrapped hollow mesoporous carbon spheres as a dynamically bipolar host for lithium–sulfur batteries

Abstract

Lithium–sulfur batteries (LSBs) hold great potential as a next-generation electrochemical energy storage and conversion system owing to their high theoretical specific capacity (1675 mA h g⁻¹). However, the shuttling of polysulfides dissolved in electrolytes with slow redox kinetics has restricted the near-term commercialization of LSBs. Developing a multifunctional host that can tightly bind polysulfides with fast conversion kinetics represents a promise strategy for improving the electrochemical performances of LSBs towards practical applications. Herein, we design three-dimensional graphene oxide wrapped hollow carbon spheres with straight mesoporous channels (termed “HMCS@GO”) as a novel cathode host for LSBs with several integrated merits: (1) the hollow carbon spheres with a mesoporous shell afford a large interior void for the loading of sulfur species and serve as a conducting substrate for high utilization of the sulfur cathode with reduced polarization; (2) the wrapped graphene oxide layer with rich surface functional groups acts as a polar carrier for effective immobilization of soluble polysulfides and promotes their quick conversion during a charge/discharge process; (3) the hollow carbon spheres also effectively buffer the large volume fluctuation of the sulfur cathode during charge/discharge with enhanced structural integrity during long-term cycling. Experimental data and first-principles density functional theory (DFT) calculations reveal that high electrochemical performance has been realized in LSBs assembled using HMCS@GO as a cathode host. This work can provide new insights into the rational design and fabrication of all carbon-based composite electrodes for useful applications in lithium–sulfur batteries and other electrochemical energy storage and conversion systems.