A bifunctional lithium polysilicate as highly efficient adhesion agent and anchoring host for long-lifespan Li-S...

The development of Li-S battery has been seriously hindered by the shuttle effect of polysulfides and the mechanical instability of the sulfur electrode during cycling. Constructing strong-affinity oxide hosts is an effective way to anchor the polysulfides. And then the oxide hosts with sulfur active materials need additional binder to adhere them to the current collector, and they also possess poor ability to suppress the volume change of sulfur cathode. Herein, a bifunctional lithium polysilicate (Li₂O·nSiO₂, LSO) as highly efficient adhesion agent and anchoring host has been exploited for long-lifespan Li-S battery. Like other oxide hosts, density functional theory (DFT) calculations reveal that LSO also displays strong chemisorption effect towards polysulfides. Specially, the LSO shows impressive adhesive property and mechanical strength, which make it act as a robust binder to improve the mechanical stability of the sulfur electrode. The sulfur cathode with LSO as the highly efficient adhesion agent and anchoring host can give an excellent cycling stability with ∼ 0.076 % capacity decay per cycle at 0.5C for 500 cycles. This work lights a new way to improve the chemical and mechanical stability of sulfur cathodes.