Trimethyl Phosphate for Nonflammable Carbonate-Based Electrolytes for Safer Room-Temperature Sodium-Sulfur Batteries

Graphical Try to set the night on fire : a nonflammable electrolyte for room-temperature sodium-sulfur (RT Na-S) batteries is prepared by introducing trimethyl phosphate (TMP) into 1.0 M NaClO 4 -ethylene carbonate/ propylene carbonate (EC/PC) electrolyte. With 15 wt.% TMP-contained electrolyte the C/S electrode shows excellent cycling stability with a reversible capacity of 788 mAh g −1 after 80 cycles as well as a good rate performance. To address the safety concern for room-temperature sodium-sulfur batteries, such as fires easily triggered by organic electrolytes, an applicable non-flammable electrolyte formula was developed by introducing trimethyl phosphate (TMP) into 1.0 M NaClO 4 -ethylene carbonate/propylene carbonate electrolyte. It is demonstrated that the electrolyte containing 15 wt.% TMP was a optimized formula, exhibiting nonflammability, thermal stability, electrochemical compatibility and lasting cell performance. Using this optimized electrolyte formula, the sulfur cathode exhibited a stable capacity of 788 mAh g −1 at a rate of 0.1 C and excellent rate capability of 441 and 177 mAh g −1 for 200 cycles at rates of 1 C and 5 C , respectively. When the TMP content further increases to 25 wt.%, the specific capacity of batteries declined significantly due to unstable SEI. Our study can shed light on the development of flame-retardant electrolyte for room-temperature sodium-sulfur or other batteries.