Constructing effective interface for room-temperature Beta-Al2O3 based sodium metal batteries

The interface problem between the electrodes and Beta-Al2O3 solid-state electrolyte severely hindered its practical application as a room-temperature battery. Herein, the poly(vinylidene fluoride-co-hexafluoropropylene)/poly(methyl methacrylate)(PVDF-HFP/PMMA) gel polymer membrane was tightly coated on the surface of Beta-Al2O3 electrolyte to construct an interlayer by a convenient method. The flexible and porous PVDF-HFP/PMMA gel polymer membranes can not only significantly enhance the physical attach between electrolyte and electrodes, but also absorb liquid electrolyte provide an effective way for Na ion transport, thereby inhibiting sodium dendrites. With Gel modification layer, the interfacial resistance of Beta-Al2O3/Na significantly decreased from 2865 Ω cm2 to 251 Ω cm2. At room temperature, the Na/Gel-Beta-Al2O3-Gel/Na symmetric cell can run stably for 200 h at 0.25 mA cm−2 with a high critical current density of 0.85 mA cm−2. The fabricated Na3V2(PO4)3(NVP)/Gel-Beta-Al2O3-Gel/Na cell also displayed favorable capacity retention ratios and rate performance profiting from the constructed stable interface. This work raised a convenient approach to solve the interface problem, driving the development of room-temperature Beta-Al2O3 based sodium metal batteries.