Composite polymer electrolyte is promising in future lithium-ion battery due to its high safety, easy-processing feature and electrochemical stability. However, it is still a great challenge to obtain the electrolyte with both low thickness and high conductivity. In this work, we synthesize a ~25 μm thin electrolyte membrane with the Li₇La₃Zr₂O₁₂-embedded polyacrylonitrile-based fiber as the 3D backbone and the in-situ polymerized gel electrolyte as the fillers. The electrolyte with the multi-dimensional lithium ion conducting channels exhibits a high conductivity of 1.60 × 10⁻³ S·cm⁻¹ at 25 °C. The wide electrochemical window of 4.5 V vs. Li/Li⁺ enables the electrolyte to match with high voltage cathode materials. The Li||Li symmetric cell with the electrolyte shows a high cycling stability with more than 350 h at a current density of 0.1 mA·cm⁻². In addition, the solid-state LiFePO₄||Li full cell has a stable charge-discharge cycle at 25 °C. This thin electrolyte can be used in lithium-ion batteries to improve energy density. The method of preparing thin composite polymer electrolyte membrane can also be extended to other polymer-filler systems.

复合聚合物电解质由于其高安全性，易加工性和电化学稳定性而在未来的锂离子电池中很有前途。然而，获得具有低厚度和高导电率的电解质仍然是巨大的挑战。在这项工作中，我们以嵌入Li ₇ La ₃ Zr ₂ O ₁₂的聚丙烯腈基纤维为3D主链，并使用原位聚合的凝胶电解质作为填料，合成了约25μm的薄电解质膜。与多维锂离子传导通道的电解质表现出1.60×10高导电率^{- 3}  S·厘米^{- 1}在25℃下。相对于Li / Li为4.5 V的宽电化学窗口⁺使电解质能够与高压阴极材料匹配。带有电解质的Li || Li对称电池在电流密度为0.1 mA·cm ^{- 2的情况下，}在超过350小时的时间内显示出高循环稳定性。此外，固态LiFePO ₄ || Li满电池在25°C时具有稳定的充放电循环。这种稀薄的电解质可用于锂离子电池中，以提高能量密度。制备复合聚合物电解质薄膜的方法也可以扩展到其他聚合物-填料体系。