A novel polymeric sodium tartaric acid borate is synthesized and blended with poly(vinylene carbonate) to prepare a single-ion conducting gel polymer electrolyte (PSP-GPE). The PSP-GPE possesses a superior ionic conductivity of 1 x 10(-4) S cm(-1) at ambient temperature and a high sodium ion transference number of 0.88. Compared to the NaClO4 based liquid electrolyte, the Na3V2(PO4)(3)/Na battery assembled with the PSP-GPE exhibits improved cycling performance, especially at elevated temperatures, and effective suppression of sodium dendrites. This work demonstrates a promising method to design single-ion conducting gel polymer electrolytes for elevated-temperature sodium metal batteries.