Since commercialization in 1992, lithium-ion batteries have been globally applied. In light of the increasing demand for high energy density and safety, all-solid-state lithium batteries have been considered as a potential candidate. Polymer-based solid-state electrolytes with conspicuous flexibility are attractive. However, their practical applications encounter significant challenges of interfacial instability.

A primary hindrance lies in the solid electrolyte interphase on the anode. As compared, Li₂O displays a much lower diffusion energy barrier and higher intrinsic ionic conductivity for Li⁺, making Li₂O more conducive to SEI transport.
In this study, researchers proposed a lithium crosslinking strategy to tailor the stable Li₂O-rich SEI by introducing 15-crown-5 into the polymer matrix. The 15-crown-5 crosslinks with lithium ions, weakening the coordination between lithium ions and polymer chains. The crosslinked 15-crown-5 moves along with lithium ions to the anode and decomposes to form a Li₂O-rich SEI.
The PL15C5 electrolyte presented improved mechanical performance with tensile modulus of 352.06 MPa. Ionic conductivity reached 7.52×10⁻⁵ S·cm⁻¹ at room temperature. Raman spectra showed a distinct peak at 865 cm⁻¹, indicating the 15-crown-5 coordinated with Li⁺.
The Li‖PL15C5‖Li symmetric cell presented lower polarization voltage and enhanced cycling time of 1100 h. XPS depth profiling revealed a Li₂O-rich SEI formed with PL15C5. The Li₂O-rich SEI significantly reduced the lithium-ion diffusion energy barrier from 84.89 kJ·mol⁻¹ to 50.86 kJ·mol⁻¹.
The LiFePO₄‖PL15C5‖Li battery delivered discharge capacities of 167.6 mAh·g⁻¹ at 0.2 C, maintaining 92.75% capacity retention after 500 cycles at 1 C. When paired with NCM811 cathode, the battery maintained 81.44% capacity retention after 300 cycles at 1 C.
This study inspires the development of high-performance all-solid-state lithium batteries by rationally tailoring interface chemistry components at the molecular level.

DOI
10.1007/s11705-026-2633-y