Composite polymer electrolytes (CPEs) for solid-state Li-metal batteries (SSLBs) still suffer from gradually increased interface resistance and unconstrained Li-dendrite growth. Herein, we addressed the challenges by designing a LiF-rich inorganic solid-electrolyte interphase (SEI) through introducing a fluoride-salt-concentrated interlayer on CPE film. The rigid but flexible CPE helps accommodate the volume change of electrodes, while the polymeric highly concentrated electrolyte (PHCE) surface-layer regulates Li-ion flux due to the formation of a stable LiF-rich SEI via anion reduction. The designed CPE-PHCE presents enhanced ionic conductivity and high oxidation stability of >5.0 V (versus Li/Li⁺). Furthermore, it dramatically reduces the interfacial resistance and achieves a high critical current density of 4.5 mA cm⁻². The SSLBs, fabricated with thin CPE-PHCE membranes (<100 μm) and Co-free LiNiO₂ cathodes, exhibit exceptional electrochemical performance and long cycling stability. This approach of SEI design can also be applied to other types of batteries.

用于固态锂金属电池 (SSLB) 的复合聚合物电解质 (CPE) 仍然存在界面电阻逐渐增加和锂枝晶生长不受限制的问题。在此，我们通过在 CPE 膜上引入氟化盐浓缩夹层来设计富含 LiF 的无机固体电解质中间相 (SEI)，从而解决了这些挑战。刚性但柔性的 CPE 有助于适应电极的体积变化，而聚合物高浓度电解质 (PHCE) 表面层通过阴离子还原形成稳定的富含 LiF 的 SEI，从而调节锂离子通量。设计的 CPE-PHCE 具有增强的离子电导率和 >5.0 V 的高氧化稳定性（相对于 Li/Li ⁺）。此外，它显着降低了界面电阻并实现了 4.5 mA cm ^-2的高临界电流密度。SSLB 由薄 CPE-PHCE 膜（<100 μm）和无 Co LiNiO ₂阴极制成，表现出优异的电化学性能和长循环稳定性。这种 SEI 设计方法也可以应用于其他类型的电池。