Sandwich‐Structured Quasi‐Solid Polymer Electrolyte Enables High‐Capacity, Long‐Cycling, and Dendrite‐Free Lithium Metal Battery at Room Temperature

The insufficient ionic conductivity, limited lithium-ion transference number (tLi +), and high interfacial impedance severely hinder the practical application of quasi-solid polymer electrolytes (QSPEs). Here, a sandwich-structured polyacrylonitrile (PAN) based QSPE is constructedin which MXene-SiO2 nanosheets act as a functional filler to facilitate the rapid transfer of lithium-ion in the QSPE, and a polymer and plastic crystalline electrolyte (PPCE) interface modification layer is coated on the surface of the PAN-based QSPE of 3 wt.% MXene-SiO2 (SS-PPCE/PAN-3%) to reduce interfacial impedance. Consequently, the synthesized SS-PPCE/PAN-3% QSPE delivers a promising ionic conductivity of ≈1.7 mS cm-1 at 30 °C, a satisfactory tLi + of 0.51, and a low interfacial impedance. As expected, the assembled Li symmetric battery with SS-PPCE/PAN-3% QSPE can stably cycle more than 1550 h at 0.2 mA cm-2 . The Li||LiFePO4 quasi-solid-state lithium metal battery (QSSLMB) of this QSPE exhibits a high capacity retention of 81.5% after 300 cycles at 1.0 C and at RT. Even under the high-loading cathode (LiFePO4 ≈ 10.0 mg cm-2 ) and RT, the QSSLMB achieves a superior area capacity and good cycling performance. Besides, the assembled high voltage Li||NMC811(loading ≈ 7.1 mg cm-2 ) QSSLMB has potential applications in high-energy fields.