Liquid–liquid interfacial tension stabilized Li-metal batteries

Abstract

A lithium (Li)-metal anode paired with a high-nickel cathode is considered to be a combination that holds promise to surpass the 500 Wh kg⁻¹ threshold^1,2. Approaching such high energy density, electrolytes capable of stabilizing both anode and cathode interphases are of importance to secure safe and long-term cycling^3,4. Although anion-derived inorganic interphases have shown remarkable success at the Li side^5,6,7, developing intrinsic strategies to concurrently protect both electrodes remains a key challenge. Here we report a micro-emulsion strategy for electrolyte design that bypasses the Li⁺ solvation regulation and produces fluoride-rich interphases for both electrodes. Specifically, liquid–liquid interfacial tension between the micelles and carbonate solvents, rather than the electric field, propels the motion of fluorinated droplets towards the anode and the cathode. In this way, the interphase construction of both electrodes can be enhanced and decoupled from the solvation structure strategy. Through use of the micro-emulsion electrolyte, two pouch full cells with energy densities of 531 Wh kg⁻¹ and 547 Wh kg⁻¹ retain 81% and 79% of their capacity after 189 and 155 cycles, respectively. The introduction of liquid–liquid interfacial tension provides a perspective for interphase regulation and electrolyte design, and paves the way for the development of high-voltage Li-metal batteries.