Nonflammable Succinonitrile-Based Deep Eutectic Electrolyte for Intrinsically Safe High-Voltage Sodium-Ion Batteries

Intrinsically safe sodium-ion batteries are considered as a promising candidate for large-scale energy storage systems. However, the high flammability of conventional electrolytes may pose serious safety threats and even explosions. Herein, a strategy of constructing a deep eutectic electrolyte is proposed to boost the safety and electrochemical performance of succinonitrile (SN)-based electrolyte. The strong hydrogen bond between S & boxH;O of 1,3,2-dioxathiolane-2,2-dioxide (DTD) and the alpha-H of SN endows the enhanced safety and compatibility of SN with Lewis bases. Meanwhile, the DTD participates in the inner Na+ sheath and weakens the coordination number of SN. The unique solvation configuration promotes the formation of robust gradient inorganic-rich electrode-electrolyte interphase, and merits stable cycling of half-cells in a wide temperature range, with a capacity retention of 82.8% after 800 cycles (25 degrees C) and 86.3% after 100 cycles (60 degrees C). Correspondingly, the full cells deliver tremendous improvement in cycling stability and rate performance. An intrinsically safe sodium-ion battery is realized by the new-type of nonflammable succinonitrile (SN)-based deep eutectic electrolyte. The deep eutectic electrolyte with a strong hydrogen bond between S & boxH;O of 1,3,2-dioxathiolane-2,2-dioxide and the alpha-H of SN effectively improves the compatibility of SN with Lewis bases. image