Slide-Crosslinked Polyrotaxane Topological Networks: Quasi-Solid Electrolyte for High-Voltage Lithium Metal Batteries

Although polymer-based electrolytes offer advantages like low cost, favorable interfacial compatibility, and processability for solid-state lithium metal batteries with high safety and high energy density, conventional linear polymer-based electrolytes suffer from inadequate oxidation resistance and mechanical strength at operating voltages above 4.5 V, causing rapid capacity degradation and reduced battery lifespan. Inspired by the mechanical slide-ring structure of polyrotaxanes (PR), a series of high-voltage-resistant sliding crosslinked quasi-solid electrolytes (PMBA-PPR_x) is designed and synthesized via in situ thermal polymerization of varying amounts of vinyl functional polyrotaxanes (PPRs) with N,N'-methylenebisacrylamide (MBA). The optimal PMBA-PPR₅ electrolyte realizes the synergistic enhancement of both mechanical properties and high-voltage-resistant electrochemical properties as well as the good interfacial compatibility. The dynamic slide ring structure of PPRs effectively dissipates the energy generated by lithium dendrite growth, thereby maintaining the mechanical robustness of the electrolyte during battery cycling and achieving lithium deposition/stripping behavior for more than 2000 h at 0.5 mA cm^-2. The strong polar amide groups of MBA not only improve the lithium-ion transference number (0.69), but also enhance the high-voltage stability of the electrolyte (∼ 5.5 V), ultimately resulting in excellent cycling stability and capacity retention of Li|PMBA-PPR₅|LFP and Li|PMBA-PPR₅|NCM811 cells. This slide-crosslinked polyrotaxane topological dynamic structure provides a new strategy for the design of high-voltage lithium metal electrolytes.