Interfacial phase regulation of flexible single-ion conducting block copolymer electrolytes ensuring ultra-stable lithium metal batteries

Abstract

Single-ion conducting copolymer electrolytes (SIPEs) have significant potential for next-generation lithium metal batteries (LMBs). However, the unsatisfactory ionic conductivity, limited mechanical strength, and lack of insights into the lithium-ion transport mechanism hinder their wide applications in LMBs. In this regard, we develop a novel SIPE through tethering lithium 3-hydroxypropanesulfonyl-trifluoromethanesulfonylimide onto a poly(vinylidene fluoride-co-trifluorochloroethylene)-based copolymer (PCL-SIPE). Molecular dynamics simulations reveal a unique transport pathway where fluorine atoms in the copolymer backbone interact with lithium-ions, serving as staging points for ion transport between adjacent sidechains. Compared with dual-ion conducting counterparts, PCL-SIPE exhibits significantly higher Young's modulus (28 vs. 17 GPa), tensile strength (20.65 vs. 5.65 MPa), and t_Li⁺ (0.94 vs. 0.39), achieving substantially prolonged lithium stripping-plating lifetime, ca., >3200 vs. 323 h. This is predominantly ascribed to the as-formed favorable solid electrolyte interphase with ideal constitutions—ultra-high LiF content in combination with Li₂O, dynamically regulating uniform Li⁺ flux and stabilizing the electrode|electrolyte interface. Thereby, PCL-SIPE demonstrates superior compatibility with both LiFePO₄ (LFP) and LiNi_0.8Co_0.1Mn_0.1O₂ cathodes in full-cells, and achieves impressive performance even under high-loading conditions (15 mg cm⁻²), low-temperature (−30 °C), in trilayer bipolar stacking pouch full-cells, achieving an energy density of 245.88 Wh kg⁻¹. These render PCL-SIPE a strong candidate for next-generation high-performance LMBs.