Cationic Size Effect Promoting Dissolution of Nitrate Anion in Ester Electrolyte for Lithium-Metal Batteries

The coupling of lithium metal (Li), an ester electrolyte, and high voltage cathode materials is expected to realize rechargeable batteries with high energy densities. Herein, a cationic size effect is first demonstrated to promote the dissolution of NO3- in an ester electrolyte and a SEI layer containing Li3N is constructed. By adjusting the size of quaternary ammonium (R4N+), the charge localization state of R4N+ and the binding energy between R4N+ and NO3- are regulated, achieving a high solubility (1.8 M) of tetraethylammonium nitrate (TEAN) in ethylene carbonate. Using TEAN as an ester electrolyte additive, the Li/Cu batteries can stably run over 1000 h with an average CE of 98.6%, 8 times longer than that of a conventional ester electrolyte. Moreover, the cyclic life of assembled Li/LiFePO4 and Li/NCM811 batteries can also be increased by 3-4 times.

Automated summary

In this study, it is demonstrated that the cationic size effect promotes the dissolution of NO3- in an ester electrolyte and a SEI layer containing Li3N is successfully constructed. By adjusting the size of quaternary ammonium, a high solubility of tetraethylammonium nitrate in ethylene carbonate is achieved, thereby improving the cycling life of lithium metal batteries and lithium-ion batteries.