A Safer Sodium-Ion Battery Based on Nonflammable Organic Phosphate Electrolyte

Sodium-ion batteries are now considered as a low-cost alternative to lithium-ion technologies for large-scale energy storage applications; however, their safety is still a matter of great concern for practical applications. In this paper, a safer sodium-ion battery is proposed by introducing a nonflammable phosphate electrolyte (trimethyl phosphate, TMP) coupled with NaNi 0.35 Mn 0.35 Fe 0.3 O 2 cathode and Sb-based alloy anode. The physical and electrochemical compatibilities of the TMP electrolyte are investigated by igniting, ionic conductivity, cyclic voltammetry, and charge–discharge measurements. The results exhibit that the TMP electrolyte with FEC additive is completely nonflammable and has wide electrochemical window (0–4.5 V vs. Na/Na + ), in which both the Sb-based anode and NaNi 0.35 Mn 0.35 Fe 0.3 O 2 cathode show high reversible capacity and cycling stability, similarly as in carbonate electrolyte. Based on these results, a nonflammable sodium-ion battery is constructed by use of Sb anode, NaNi 0.35 Mn 0.35 Fe 0.3 O 2 cathode, and TMP + 10 vol% FEC electrolyte, which works very well with considerable capacity and cyclability, demonstrating a promising prospect to build safer sodium-ion batteries for large-scale energy storage applications.