Solid polymer electrolytes (SPEs) are promising for achieving safe solid-state Li metal batteries (SSLMBs). However, unstable electrode/electrolyte interface contact of SPEs limits their application at high voltage. To address this issue, we designed a multi-layer asymmetric SPE with a sandwich structure based on the hydroxyapatite (HAP) enhanced PVDF-HFP matrix. Two different interfacial modification layers were introduced on the anode and cathode sides. Methyl (2,2,2-trifluoromethyl) carbonate (FEMC) and tetramethylene sulfone (TMS) were selected as plasticizers in the layers, respectively, contacting the anode and cathode to reduce the reactivity of the anode interface and enhance the high-voltage compatibility of the cathode interface. Unlike usual designs, each layer of the asymmetric SPE has essentially the same composition except the plasticizers, effectively eliminating interface resistance and promoting Li⁺ fast migration. Consequently, the asymmetric SPE exhibits excellent ionic conductivity at room temperature (8.8 × 10⁻⁴ S cm⁻¹), superior interfacial stability, and Li dendrite inhibition ability. In addition, LiFePO₄||SPE||Li cell demonstrates a stable retention rate of over 92 % after 500 cycles at 1 C. These findings provide a new approach for implementing SSLMBs under high voltage.

固体聚合物电解质（SPE）有望实现安全的固态锂金属电池（SSLMB）。然而，SPE 不稳定的电极/电解质界面接触限制了其在高电压下的应用。为了解决这个问题，我们设计了一种基于羟基磷灰石（HAP）增强的PVDF-HFP基质的具有夹层结构的多层不对称SPE 。在阳极和阴极侧引入了两种不同的界面改性层。分别选择(2,2,2-三氟甲基)碳酸甲酯(FEMC)和四亚甲基砜(TMS)作为层内增塑剂，分别接触阳极和阴极，降低阳极界面的反应性，增强高压兼容性的阴极接口。与通常的设计不同，不对称SPE的每一层除了增塑剂外都具有基本相同的成分，有效消除界面电阻并促进Li⁺快速迁移。因此，不对称SPE在室温下表现出优异的离子电导率（8.8×10^-4S cm^-1）、优异的界面稳定性和锂枝晶抑制能力。此外，LiFePO₄||SPE||Li 电池在 1 C 下循环 500 次后表现出超过 92% 的稳定保留率。这些发现为在高电压下实现 SSLMB 提供了一种新方法。