Polyrotaxane‐Assembled Semi‐Interpenetrating Polymer Electrolytes Enabling High‐Voltage Lithium Metal Batteries

Polyether-based solid polymer electrolytes suffer from low ionic conductivity at room temperature, poor oxidative stability at high voltages, and susceptibility to dendrite growth, all of which hinder their application in high-energy-density lithium batteries. Herein, we report a polyrotaxane-assembled supramolecular semi-interpenetrating network electrolyte (SSNE), synthesized through in situ polymerization of polyrotaxane with crosslinked polydioxolane (PDOL). The key innovations of this architecture are threefold: it creates hierarchical ion-conduction pathways, introduces Lewis acid sites, and imposes spatial confinement within a polyrotaxane framework. Through host-guest interactions, these elements synergistically decouple the transport of Li⁺ ions from the migration of anions. The SSNE exhibits impressive room-temperature ionic conductivity of 0.18 mS cm^- ¹ and Li⁺ transference number ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>t</mml:mi> <mml:mrow><mml:mi>L</mml:mi> <mml:msup><mml:mi>i</mml:mi> <mml:mo>+</mml:mo></mml:msup> </mml:mrow> </mml:msub> <mml:annotation>${t_{L{i^ + }}}$</mml:annotation></mml:semantics> </mml:math> > 0.73). Furthermore, fluorine- and boron-functionalized polyrotaxane stabilizes the electrode-electrolyte interphase and extends the electrochemical window (> 4.9 V). The full cell prototype comprising the LiNi_0.8Co_0.1Mn_0.1O₂ cathode, the SSNE, and Li foil delivers 81.4% capacity retention after 200 cycles and rate capability up to 2C. Moreover, a 1.2 Ah pouch-format cell operates reliably for 190 cycles at room temperature with a cutoff voltage of 4.5 V. This study integrates dynamic polyrotaxane chemistry with a semi-interpenetrating polymer electrolyte architecture, offering a molecule-to-system strategy for the development of next-generation high-voltage lithium metal batteries.