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.