An in-situ encapsulation approach for polysulfide retention in lithium-sulfur batteries
A long-lived lithium-sulfur battery requires insulation of the dissolved polysulfide intermediates from the reactive anode. However, there exists a trade-off between preventing polysulfide dissolution and facilitating the sulfur redox reactions. Here, an in-situ encapsulation strategy for sulfur/cathode (S/C) cathode is developed. We employ antimony trifluoride as a bi-functional pre-coating layer on the S/C composite surface. During the in-situ encapsulation process, liquid electrolyte can wet the S/C composite; while being catalyzed by antimony trifluoride, the liquid electrolyte can polymerize to form a dense lithium-ion-conducting solid polymer electrolyte (SPE) layer on the S/C composite surface. Additionally, antimony trifluoride proves to have strong anchoring effects for polysulfides, which works together with the SPE layer to suppress polysulfide dissolution. The in-situ encapsulated cathode enhances the cyclability with a minor sacrifice in the rate capability. It is further demonstrated that the cathode can be directly paired with a non-protected lithiatied silicon anode to achieve a practical capacity retention rate of 87% for 200 cycles.