Anion-enrichment interface enables high-voltage anode-free lithium metal batteries

Abstract

Aggressive chemistry involving Li metal anode (LMA) and high-voltage LiNi_0.8Mn_0.1Co_0.1O₂ (NCM811) cathode is deemed as a pragmatic approach to pursue the desperate 400 Wh kg⁻¹. Yet, their implementation is plagued by low Coulombic efficiency and inferior cycling stability. Herein, we propose an optimally fluorinated linear carboxylic ester (ethyl 3,3,3-trifluoropropanoate, FEP) paired with weakly solvating fluoroethylene carbonate and dissociated lithium salts (LiBF₄ and LiDFOB) to prepare a weakly solvating and dissociated electrolyte. An anion-enrichment interface prompts more anions’ decomposition in the inner Helmholtz plane and higher reduction potential of anions. Consequently, the anion-derived interface chemistry contributes to the compact and columnar-structure Li deposits with a high CE of 98.7% and stable cycling of 4.6 V NCM811 and LiCoO₂ cathode. Accordingly, industrial anode-free pouch cells under harsh testing conditions deliver a high energy of 442.5 Wh kg⁻¹ with 80% capacity retention after 100 cycles.

The implementation of Li metal anode with high-voltage Ni/Co rich cathode is plagued by low coulombic efficiency and inferior cycling stability. Here authors propose an anion-enriched interface to facilitate the columnar-structure of Li deposits to solve this issue.