Toward High Temperature Sodium Metal Batteries via Regulating the Electrolyte/ Electrode Interfacial Chemistries

Rechargeable batteries based on sodium metal anodes (SMAs) are endowed with much higher energy density than traditional sodium-ion batteries. However, the use of SMAs brings intrinsic challenges of dendrite growth and situation can be further exacerbated at high temperature (>55 degrees C, HT). Here, we resolve such HT-challenge by formulating a thermally stable sulfolane (SL)-based electrolyte that regulates the electrode/electrolyte interfacial chemistries. Besides rapid Na anode passivation enabled by fluoroethylene carbonate (FEC) molecules, a nitrile-based 1,3,6-hexanetricarbonitrile (HTCN) cosolvent is simultaneously introduced, whose three electron-rich -C equivalent to N groups interact with the electropositive metal ions of Na3V2(PO4)2O2F, shielding away solvent attacks occurring at the cathode interface. As a result, we realize a high capacity retention (91.7% after 500 cycles at 1 C) for the Na/Na3V2(PO4)2O2F cell at 60 degrees C, with a high average carbon equivalent (CE) of similar to 99.6%. Even at 80 degrees C, the cell still delivers similar to 89.1% of its initial capacity after 100 cycles, whereas the control sample fails rapidly within 30 cycles.

Automated summary

This study addresses the challenges of dendrite growth in rechargeable batteries based on sodium metal anodes at high temperatures. By formulating a thermally stable electrolyte, the researchers were able to regulate the electrode/electrolyte interface chemistry and protect against solvent attacks. The results demonstrate a high capacity retention and long cycle life for the batteries at elevated temperatures.