Enhancement of interfacial sodium ion transport stability in quasi-solid-state sodium-ion batteries using polyethylene glycol

Poor electrode/solid electrolyte interface stability and dendrite growth have seriously hindered the widespread application of solid-state sodium-ion batteries with high energy density, low cost, and high safety. Herein, a facile strategy is proposed to stabilize the interfacial layer and inhibit dendrite growth using a polyethylene glycol (PEG)-modified poly(vinylidene fluoride-co-hexafluoropropylene)-in-NASICON (Na3Zr2Si2PO12) quasi-solid electrolyte (QSE). PEG enhances the coordination strength between Na+ and solvent molecules, and inhibits the volatilization of the solvent. The "sodiophilic" -OH functional group improves the wettability of the QSE surface to sodium metal and inhibits the dendrite growth, thereby constructing a stable interfacial ion transport channel. The room temperature ionic conductivity of QSE with 5% PEG content is 2.4 x 10(-4) S cm(-1), and has a high Na+ transference number of 0.84. In addition, the Na||Na battery exhibits stable sodium deposition/stripping capability at a current density of 0.2 mA cm(-2) for 3000 h without dendrite growth. The initial discharge specific capacity of the Na||Na3V2(PO4)(3) battery at 1C current density is 100.3 mA h g(-1), and the capacity retention rate after 200 cycles is up to 94%. The mechanism of action of a PEG-modified QSE was determined, which provides a reference for the rational design and optimization of QSEs.