Quasi-Solid Composite Polymer Electrolyte-Based Structural Batteries with High Ionic Conductivity and Excellent Mechanical Properties

Structural lithium batteries integrated with energy storage and mechanical load-bearing capabilities hold great promise to revolutionize lightweight transport vehicles. However, the current development of structural batteries faces critical challenges in balancing the electrochemical and mechanical properties of the electrolytes. Herein, a super strong quasi-solid composite polymer electrolyte (QCPE) is successfully fabricated by reinforcing polyelectrolyte with 3D in situ self-assembled metal–organic framework-modified glass fiber (MOF@GF) soaking a small amount of liquid electrolyte, which provides continuous ion conductive pathways for fast Li⁺ transport and contributes to the high ambient ionic conductivity of 1.47 × 10⁻³ S cm⁻¹. The micropores and abundant polar functional groups selectively restrict the transport of anions to afford a homogeneous Li⁺ flux and a high Li⁺ transference number (0.56). Simultaneously, the MOF@GF provides more effective reinforcement and a remarkably high tensile strength of 48.6 MPa, and Young's modulus of 1.66 GPa is achieved. Furthermore, the lithium metal batteries fabricated with this QCPE exhibit a long, stable operation lifespan of 2000 h and excellent cycling performance with LiFePO₄ and NCM811 cathodes. This design strategy generally opens a new avenue for structural batteries with high ionic conductivity and outstanding mechanical properties, which holds great promise for industrial translation.