570 Wh/kg-grade Lithium Metal Pouch Cell with 4.9V Highly Li + Conductive Armor-like Cathode Electrolyte Interphase via Partially Fluorinated Electrolyte Engineering.

Lithium-rich manganese-based layered oxides (LRMOs) are promisingly used in high-energy lithium metal pouch cells due to high specific capacity/working voltage. However, the interfacial stability of LRMOs remains challenging. To address this question, we proposed a novel armor-like cathode electrolyte interphase model for stabilizing LRMO cathode at 4.9 V by exploring partially fluorinated electrolyte formulation. The fluoroethylene carbonate (FEC) and tris (trimethylsilyl) borate (TMSB) in formulated electrolyte largely contributed to the formation of 4.9 V armor-like cathode electrolyte interphase with LiB x O y and Li x PO y F z outer layer and LiF- and Li 3 PO 4 -rich inner part. Such CEI effectively inhibited lattice oxygen loss and facilitated the Li + migration smoothly for guaranteeing LRMO cathode to deliver superior cycling and rate performance. As expected, Li||LRMO batteries with such electrolyte achieved a capacity retention of 85.7% with a high average Coulomb efficiency (CE) of 99.64% after 300 cycles at 4.8 V/0.5 C, and even obtained a capacity retention of 87.4% after 100 cycles at higher cut-off voltge of 4.9 V. Meanwhile, the 9 Ah-class Li||LRMO pouch cells with formulated electrolyte showed over 38 stable cycling life with a high energy density of 576 Wh kg -1 at 4.8 V. This article is protected by copyright. All rights reserved.