Muscovite as an inert filler for highly conductive and durable gel polymer electrolyte in sodium-ion batteries

Abstract

Sodium-ion batteries emerge as complementary to commercially established lithium-ion batteries. The keynote of the presented study is sodium gel polymer electrolyte for efficient and safer post-lithium batteries. The study aims at better mechanical strength, higher ionic conductivity, and improved thermal properties of the gel polymer electrolyte. These properties strongly depend on the composition of the electrolyte. Ionic liquid and sulfolane as plasticizers improved the ionic conductivity of the electrolyte up to 5.5 mS cm−1. Polyacrylonitrile matrix established flexibility and mechanical strength up to 5.9 MPa. However, the most significant change is the partial substitution of polymer with an inert filler. For the first time, the inert filler in sodium gel polymer electrolyte is muscovite, which affects most of the properties of the polymer electrolytes. It broadens the anodic region of the electrochemical window even by 200 mV and reduces the dimensional shrinkage of the electrolyte by 1–4% compared to the reference sample. Furthermore, muscovite enhances the tensile strength of the electrolyte, delays thermal degradation, and improves the long-term stability of the GPE/Na interface. It also assures that the gel electrolyte is compatible with a hard carbon anode in a cell that delivers a capacity of 200 mAh g−1 at C/20.