Ultrathin PVP/ZnMoO4@PE separator for high-safety sodium-ion batteries

Abstract

In this work, an ultrathin (∼19 μm) PVP/ZnMoO4@PE separator is designed and achieved with much enhanced thermal performance for high-safety sodium-ion batteries (SIBs). The PVP/ZnMoO4@PE separator is prepared by coating the polyvinyl pyrrolidone (PVP)/ZnMoO4 ceramic slurry on one side of commercial polyethylene (PE) separator in an economically efficient way. It is found that the superior PVP binder would interact with ZnMoO4 nanoparticles and enhance the bonding strength of heat-resistant ZnMoO4 ceramic nanoparticles on the surface of PE substrate, which significantly improves the thermal performance of the optimized separator. The optimized PVP/ZnMoO4@PE separator shows high thermal stability with no shrinkage at 180 °C for 30 min. In addition, the PVP/ZnMoO4@PE separator shows improved wettability with electrolyte, larger porosity and better electrolyte storage capacity than bare PE separator, which are quite beneficial to ionic conductivity. Furthermore, the electrochemical results show that half-cell (hard carbon/sodium) assembled with the optimized PVP/ZnMoO4@PE separator shows better electrochemical performance that the half-cell assembled with commercial glass fiber separator (thickness of ∼ 455 μm), while bare PE separator does not work properly in SIBs. This study provides insight into the practical application of ultrathin and high-safety PVP/ZnMoO4@PE separator in commercial SIBs.