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

• Published in: ACS applied energy materials 2020-10, Vol.3 (10), p.10053-10060
• Main Authors: Yang, Li, Jiang, Yangming, Liang, Xinmiao, Lei, Youyi, Yuan, Tianci, Lu, Haiyan, Liu, Zhihong, Cao, Yuliang, Feng, Jiwen
• Format: Article
• Language: English
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.0c01756

The limitations of conventional organic liquid electrolytes such as sodium dendrite growth, serious side reactions, and liquid leakage hinder the development of sodium–metal 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 °C, a satisfactory ionic conductivity of up to 0.94 × 10–4 S·cm–1 at room temperature, a wide electrochemical window as high as 5.2 V (vs Na+/Na) at 30 °C, and a high sodium-ion transference number of 0.91 at 60 °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 °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 23Na and 19F 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.