Material and Interfacial Modification toward a Stable Room-Temperature Solid-State Na–S Battery

Room-temperature solid-state sodium batteries have the remarkable potential to simultaneously achieve high safety, high energy density, and low cost. However, their current performance is far below expectations. Through material and interfacial modification based on Na3PS4 solid electrolytes, progress is made toward stable room-temperature solid-state sodium–sulfur (Na–S) batteries. First, the ionic liquid N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (Pyr14FSI) is employed to modify the anode/electrolyte interface. An overpotential of 0.55 V after 900 h of a symmetrical battery indicates enhanced interfacial stability. A stable in situ solid electrolyte interphase layer is formed at the interface of NaSn alloy and Na3PS4, proved by X-ray photoelectron spectroscopy measurements. Furthermore, selenium-doped sulfurized polyacrylonitrile (Se0.05S0.95@pPAN) is used to boost the ionic and electronic conductivities of the sulfur cathode. As a result, the Na–S battery using a Se0.05S0.95@pPAN cathode and the interfacial modification delivers stable cycle performance and enhanced rate capability.