Regulation of the cathode inner Helmholtz plane in dilute ether electrolytes using an electric-field-responsive solvent for high-voltage lithium metal batteries

Abstract

Raising the cut-off voltage to 4.6 V can boost the energy density of lithium metal batteries (LMBs) with the LiCoO2 cathode. However, the unfavorable cathode electrolyte interphase (CEI) formed on the high-voltage cathode when using Li metal-compatible ether electrolytes leads to a short lifespan of batteries. Here, we harness the battery intrinsic electric field to manipulate the cathode inner Helmholtz plane (IHP) during the battery's charge by simply introducing an electric-field-responsive solvent into an ether electrolyte. Specifically, 2,2-difluoroethyl trifluoromethanesulfonate (DTS) as a weak solvated co-solvent preferentially adsorbs on the cathode surface under electric field activation. Owing to the majority of “high-voltage fragile” 1,2-dimethoxyethane ether molecules squeezed out from the IHP by DTS, a LiF-rich and organics-less stable CEI film is formed, which minimizes cathode cracking and structure degradation under high-voltage. The DTS-containing electrolyte shows superior cycling stability of LMBs under harsh conditions of 4.6 V, 4.2 mA h cm−2 cathode loading and 15 μL less electrolyte. Furthermore, the feasibility of this concept is validated in practical A h-level pouch full cells. This work highlights the significance of the IHP modulation and interfacial chemistry, providing an alternative pathway towards ether-based electrolyte engineering for high-voltage LMBs.

Graphical abstract: Regulation of the cathode inner Helmholtz plane in dilute ether electrolytes using an electric-field-responsive solvent for high-voltage lithium metal batteries

Supplementary files

Article information

Article type
Paper
Submitted
09 Dec 2024
Accepted
10 Mar 2025
First published
18 Mar 2025

Energy Environ. Sci., 2025, Advance Article

Regulation of the cathode inner Helmholtz plane in dilute ether electrolytes using an electric-field-responsive solvent for high-voltage lithium metal batteries

J. Wu, Z. Gao, Z. Fu, L. Lin, X. Wang, Y. Zhao, L. Peng, F. Kang, Z. Guo, M. Titirici, Y. Zhao, X. Fan and B. Li, Energy Environ. Sci., 2025, Advance Article , DOI: 10.1039/D4EE05818F

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