Weakly anion-driven solvation towards stable operation of carbonate ester-based sodium metal batteries at −40°C
Fei Huang, Yunpeng Zhong, Mulam Qin, Ju Qiu, Chao Hu, Peng Xu, Hanqi Zhang, Chaoyi Sheng, Shuquan Liang, Guozhao Fang
Abstract
Carbonate ester-based electrolyte are crucial to support practical sodium-metal batteries (SMBs) due to their favourable oxidative stability and low cost. However, the stable operation for SMBs at −40 °C with carbonate ester-based electrolyte remains a tremendous challenge owing to sluggish kinetic of Na + desolvation and Na + migration through solid electrolyte interphase (SEI). Hence, we construct stable operation of ultralow-temperature SMBs at −40 °C via a weakly anion-drived solvation of carbonate-ester electrolyte with low concentration, which endows high Na + conductivity and low Na + desolvation barrier. Anion-driven solvation is favor of forming a roust Na + -conductive NaF-rich SEI film, thereby stabilizing SMBs at low temperature. As a result, symmetrical cells achieve long cyclic stability for 1000 h at −20 °C. In addition, the SMBs matching the P2-type Na 0.75 Ni 0.34 Mn 0.66 O 2 (NNMO) cathode with an electrochemical window of 4.15 V achieve the high capacity retention of 91.5 % after 600 cycles at −20 °C and 85.4 % after 160 cycles at −40 °C. Moreover, pouch cell with high energy density (227.4W h kg −1 ) and high-loading cathode (11.76mg cm −2 ) provides a stable 100 cycle at −20 °C. The optimized carbonate ester electrolyte provides vital insights into developing ultra-low-temperature SMBs.