Novel Sodium-Poly(tartaric acid)Borate-Based Single-Ion Conducting Polymer Electrolyte for Sodium-Metal Batteries

The limitations of conventional organic liquid electrolytes such as sodium dendrite growth, serious side reactions, and liquid leakage hinder the development of sodium-metal 2 batteries (SMBs). In this work, a novel sodium-poly(tartaric acid)borate (NaPTAB) salt with low cost and environmental friendliness was synthesized by an aqueous phase synthesis method. NaPTAB was combined with poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP) to form NaPTAB-SM, and then NaPTAB-SM was swelled in the PC solution to obtain a single sodium-ion conductor gel polymer electrolyte (GPE), denoted NaPTAB-SGPE. NaPTAB-SGPE has perfect thermal stability with an initial decomposition temperature of 345 degrees C, a satisfactory ionic conductivity of up to 0.94 x 10(-4) S.cm(-1) at room temperature, a wide electrochemical window as high as 5.2 V (vs Na+/Na) at 30 degrees C, and a high sodium-ion transference number of 0.91 at 60 degrees C. Except for these satisfying performances, the Na3V2 (PO4)(3)/Na cells assembled with NaPTAB-SGPE present excellent charge-discharge performance and stable cycling capability at high temperatures (60 degrees C). They also exhibit superior cycling stability compared to the liquid electrolyte cells with 1 M NaClO4 (EC/PC, 1:1, v/v, and 5% fluoroethylene carbonate (FEC)). After cycling, NaF is generated on the polymer electrolyte membrane as observed by Na-23 and F-19 solid-state NMR, which is more likely responsible for the excellent charge-discharge stability and cycling performance of the battery. These results show that NaPTAB-SGPE is a great potential alternative for solid-state sodium batteries.