Concurrent electrode-electrolyte interfaces engineering <i>via</i> nano-Si<sub>3</sub>N<sub>4</sub> additive for high-rate, high-voltage lithium metal batteries

Abstract

Electrolyte engineering is emerging as a key strategy for enhancing the cycle life of lithium metal batteries (LMBs). Fluorinated electrolytes have dramatically extended cycle life; however, intractable challenges in terms of rate capability and fluorine overuse persist. Here, we introduce a lithiophilic, solvent-interactive, and fluorine-free nano-Si3N4 additive that facilitates the fine-tuning of weak Li+ solvation to form inorganic-rich solid-electrolyte interphase (SEI) layers. Additionally, the alloying and conversion reactions between nano-Si3N4 and Li generated a fast Li+-conductive SEI, overcoming the poor rate performance of weakly solvating electrolytes. Simultaneously, nano-Si3N4 interacts with ethylene carbonate (EC), minimizing hydrogen (H)-transfer reactions and scavenging HF, thus increasing the high-voltage tolerance. Consequently, nano-Si3N4 extends the cyclability of the commercial carbonate-based electrolyte in 360 W h kg-1-level Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) pouch-cells, resulting in 74% capacity retention after 100 cycles, whereas failure occurred without it. Our study provides an in-depth understanding of the working mechanisms of suspension electrolytes through comprehensive analysis.