Conductive Na3Sc2P3O12 filler with different crystal phases modified gel polymer electrolyte membranes for sodium ions batteries

Abstract Compared with lithium-ion batteries, sodium-ion batteries possess the advantages of low cost and high energy density. The research and development of the positive, negative and electrolyte materials of sodium-ion batteries is of great significance to develop sodium-ion energy storage devices. The sodium superionic conductor (NASICON) with a stoichiometric ratio of Na3Sc2P3O12 (NSP) has a variety of crystal types, namely α-, β- and γ-phase. Different crystal structures exhibit different ion transport characteristics, resulting in the varied ionic conductivity and other electrochemical performance. The effect of different crystalline-type Na3Sc2P3O12 (α-Na3Sc2P3O12, β-Na3.5Sc2P2.5Si0.5O12 and γ-Na4Sc2P2SiO12) fillers on gel polymer electrolytes (GPE) was investigated in detail. Due to the difference in the adsorption capacity of the gel electrolyte added three types of crystalline-type fillers and the difference in the conductivity of fillers, the composite gel electrolytes exhibited various performances. The optimal gel electrolyte with 7 ​% γ-Na4Sc2P2SiO12 filler delivers the optimal conductivity as high as 2.783 ​× ​10−3 ​S ​cm−1. The optimal performance of Na3V2(PO4)3/C| GPE |Na cell shows that the first discharge specific capacity was 92.3 mAh g−1 with a capacity retention rate of 98.18% after 100 cycles.