Ultra-long cycle sodium ion batteries enabled by glutaric anhydride additive

Abstract

For sodium-ion batteries, solving the pain point of short cycle life is the key to large-scale promotion for the industry, and the electrolyte plays an important role on it. Herein, this work is on purpose to design a practical sodium ion battery electrolyte with industrial application value and introduces anhydride compounds as additives for the first time. Meanwhile, by adjusting the solvent composition and using the combination of ether and ester solvent, the optimal electrolyte formulation 1 M NaPF6+DME/VC (1:1, v/v)+2 wt.% GA is designed. Na+-VC, which has the highest occupied molecular orbital in this electrolyte, is preferentially oxidized to form cathode electrolyte interface on the cathode. And synchronously, Na+-GA with the lowest unoccupied molecular orbital is preferentially reduced to form surface electrolyte interface on the anode. This electrolyte can achieve simultaneous film formation on both sides of the electrode, thus greatly increasing the cycle life of sodium-ion battery. For example, the Na||NVP battery still maintains a specific capacity of 91.16 mAh g-1 with a capacity retention rate of 85.06% after 2500 cycles. And the NVP||HC full battery also retains a capacity retention rate of 66.50% after 800 cycles. This work will provide important ideas and strong evidence for the industrial application of sodium ion battery electrolyte with long cycle life.