Impact of Li Ion Transport Properties on Reversibility of Li Metal Electrode in Glyme‐Based Electrolytes

Abstract

AbstractThe demand for innovative batteries with high specific energy densities has increased. Li‐metal batteries employing Li‐metal anodes, regarded as the ultimate anodes with a high theoretical capacity, have been extensively studied over the past few decades. However, the poor reversibility and safety concerns regarding Li‐metal anodes remain unresolved. The importance of the electrode/electrolyte interface, especially the solid electrolyte interphase (SEI), for achieving reversibility of Li metal anodes has been extensively studied. Herein, we focused on the impact of the Li ion transport properties in oligoether (glyme)‐based electrolytes on the deposition/dissolution efficiency of Li metal anodes. Analysis of the low‐frequency impedance spectra of Li‐plated Cu/Li cells revealed that the diffusion resistance of Li ions (Rdiffusion) may be a dominant contributor to the internal resistance of the cells employing glyme‐based electrolytes. A higher Rdiffusion in poor‐mass‐transport electrolytes with a lower Li ion transference number resulted in larger polarization during Li deposition/dissolution, leading to more pronounced unfavorable side reactions and lower Coulombic efficiency. Rdiffusion rather than interfacial resistance affected the reversibility of the Li metal anode. Enhancing the Li ion mass transport ability of electrolytes is important for achieving highly reversible charge‐discharge performance of Li metal anodes at high current densities.