A multifunctional separator as sustained release Carrier of NaNO3 to Address the low solubility of Nitrate in Electrolyte

In the face of modern large-scale energy storage needs, sodium metal batteries (SMBs) with high energy density have received widespread attention. However, safety and cycle stability issues have become obstacles to the practical application of SMBs. In this paper, we present a multifunctional and high-performance SMBs separator (NNP91) utilizing the nonwoven composite NaNO3@PVDF. NNP91 has good tensile properties and offers possibilities for flexible batteries. In addition, NNP91 has a dense separator layer that can physically block sodium dendrites to prevent short-circuit of the cell. More importantly, NNP91 brings NaNO3 into the cell, which is insoluble in conventional electrolytes. NaNO3 and Na metal form a nitride-rich solid electrolyte interphase (SEI) that inhibits the disordered growth of sodium dendrites, increases the rate of ionic shuttling and exhibits excellent electrochemical performance. NNP91 offers a new approach to inorganic materials insoluble in electrolytes. [Display omitted] •NNP91 has a dense separator layer and good tensile properties.•Observation of cell cycling through in-situ optical microscopies.•NNP91 makes the SEI layer more flat to inhibit the growth of sodium dendrites.•High-performance battery cycle by forming a full cell with Na3V2(PO4)3.