Interfacial Modulation of Lithium Deposition via an Adaptive Poly(Ether-Thiourea) Protective Layer

Abstract

Lithium metal is a promising anode material for high-energy-density batteries; however, its practical applications are significantly hindered by unstable lithium deposition and dendrite growth at the solid electrolyte interface. Functional protective coatings on lithium metal surfaces offer a viable solution to these challenges. Herein, an innovative adaptive protective layer for lithium metal anodes based on a thiourea H-bonded supramolecular polymer is developed for the first time. With dense thiourea H-bonding, the lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) incorporated poly(ether-thiourea) protective layer shows strong adhesion to the lithium metal surface and good adaptive properties. The unique viscoelastic and flow characteristics of the poly(ether-thiourea) coating facilitate uniform Li⁺ flux, effectively suppressing dendrite formation at the solid electrolyte interface. Furthermore, this innovative polymer integrates in situ generated compounds, such as Li₃N and Li₂O, significantly enhancing interfacial stability. A comprehensive analysis involving X-ray photoelectron spectroscopy, scanning electron microscopy, X-ray tomography, and COMSOL simulations elucidates the beneficial effects of the adaptive coating. Enhanced performances in Li||Cu, Li ||Li, Li||LiFePO₄, and Li||S cells demonstrate the effectiveness of the poly(ether-thiourea) coating and its undeniable capability to improve lithium deposition and cycling stability. This study highlights a promising new candidate for developing supramolecular materials capable of stabilizing lithium metal anodes.

Keywords

adaptive coating / cycling stability / dendrite growth / lithium metal anode / protective layer

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