New Nitrate Additive Enabling Highly Stable and Conductive SEI for Fast-Charging Lithium Metal Batteries

Polyester-based electrolytes formed via in situ polymerization, have been regarded as one of the most promising solid electrolyte systems. Nevertheless, it is still a great challenge to address the issue of their high reactivity with metallic lithium anode by optimizing the components and properties of solid electrolyte interphase (SEI). Herein, a new class of N-containing additive, isopropyl nitrate (ISPN) that can be miscible with ester solvents is demonstrated, and a chemically stable and ion-conductive LiF-Li3N composite SEI is constructed. In addition, ISPN can induce the formation of anion-enriched solvation structures and reduces the desolvation barrier of Li+, resulting in fast transport of Li+. With the addition of ISPN, ionic conductivity of the electrolyte has nearly doubled, reaching as high as 5.3 x 10-4 S cm-1. What's more, the LiFePO4 (LFP)|ISPN-PTA|Li cell exhibits exceptional cycle stability and fast charging capabilities, maintaining stable cycling for 850 cycles at 10 C rate. Even when paired with the high-voltage cathode, the LiNi0.6Co0.2Mn0.2O2 (NCM622)|ISPN-PTA|Li cell achieves an impressive capacity retention of 97.59% after 165 cycles at 5 C. This study offers a novel approach for ester-based polymer electrolytes, paving the way toward the development of stable and high-energy Li metal battery technologies. By introducing isopropyl nitrate (ISPN) that can be miscible with ester-based electrolytes as an additive, a chemically stable and highly ion-conductive LiF-Li3N enriched solid electrolyte interphase is constructed. In addition, the introduction of ISPN diminishes the preferential coordination of ethylene carbonate in the solvated structure and induces the formation of anion-rich solvated structure, resulting in the reduced dissolvation barrier. image