Hierarchical ionic networks in polymer electrolyte boost high-voltage solid-state Li batteries with stable interfaces and long cycling
Solid-state lithium metal batteries (SLMBs) demand quasi-solid polymer electrolytes (QSSPEs) that simultaneously deliver high ionic conductivity, interfacial stability, and oxidative resistance. This study reports a QSSPE membrane (MP46) formulated with MG30:LiTFSI:succinonitrile at a 10:4:6 weight ratio, exhibiting a wide electrochemical window of 5.1 V. Complementary infrared spectroscopy, small-angle X-ray scattering, and electron microscopy reveal a hierarchical ionic conductive network consisting of sphere-like nanostructures embedded within microphase-segregated architectures. This morphology enhances lithium-ion transport while preserving mechanical integrity. The strong interfacial adhesion between MP46 and lithium metal enables stable lithium plating and stripping for over 800 h at 0.2 mA·cm–2, effectively mitigating dendrite formation. When paired with LiFePO4 and LiCoO2 cathodes, MP46 sustains prolonged cycling, retaining 80.1% capacity after 1400 cycles at 2 C and 92.1% after 200 cycles at 4.5 V, respectively. Pouch-type cells further demonstrate mechanical flexibility and operational safety under deformation. These results establish MP46 as a viable candidate for stable high-energy-density SLMBs, offering fundamental insights into the design of next-generation polymer electrolytes.