Sodium metal batteries (SMBS) are considered as potential alternatives to high-energy lithium metal batteries (LMBS). However, the high reactivity of sodium metal to common liquid organic electrolytes makes this battery technology extremely challenging. 
Figure 1 Design of SIPEDominic Bresser, Karlsruhe Institute of TechnologyA multi-block single-ion conductive polymer electrolyte (SIPE) doped with ethylene carbonate was proposed as a suitable electrolyte system for SMBS. It was found that this new SIPE has an extremely high ionic conductivity at 40 (26 ms cm-1), as well as about 4A high electrochemical stability window of 1 V enables stable sodium stripping and deposition and enables na||Na3V2(PO4)3 cells have excellent rate capability of up to 2C. 
Fig. 2 Characterization of the electrochemical and thermal stability of SIPEIn addition, it is worth noting that due to the excellent interfacial stability of SIPE with both sodium metal and Na3V2(PO4)3 cathodes, Na|sipe|NVP batteries received 99High average coulombic efficiency of 9% and a high average coulombic efficiency of 0The volume retention rate is about 85% after 1,000 cycles at 2C, and there is still an excellent rate capacity of 100 mAh g-1 at 2C. The results of this work show that polymer electrolytes are not only a suitable alternative to liquid electrolytes for lithium-metal batteries, but are also suitable for sodium-metal batteries. 
Figure 3 Full battery performancesingle-ion conducting polymer electrolyte for superior sodium-metal batteries. angewandte chemie international edition 2023. doi: 10.1002/anie.202308699