Interfacial Phase Regulation of Flexible Single-ion Conducting Block Copolymer Electrolytes Ensuring Ultra-stable Lithium Metal Batteries

Abstract

Single-ion conducting copolymer electrolytes (SIPEs) hold 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 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 counterpart, PCL-SIPE exhibits significantly higher Young’s modulus (28 vs. 17 GPa), tensile strength (20.65 vs. 5.65 MPa), and tLi⁺ (0.94 vs. 0.39), achieving substantially prolonged lithium stripping-plating lifetime, ca., > 3200 vs. 323 h. This predominantly ascribes to the as-formed favorable solid electrolyte interphase with ideal constitutions—ultra-high LiF content in combination of Li2O, dynamically regulating uniform Li flux and stabilizing electrode|electrolyte interface. Thereby, PCL-SIPE demonstrates superior compatibility with both LiFePO4 (LFP) and LiNi0.8Co0.1Mn0.1O2 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 cells, achieving an energy density of 245.88 Wh kg−1. These render PCL-SIPE a strong candidate for next-generation high-performance LMBs.