A glass fiber reinforced crosslinked polyurethane-based composite electrolyte with high mechanical strength and large ion conductivity

Solid polymer electrolytes offer intimate interfacial contact with electrodes, making them ideal for solid-state lithium metal batteries. However, the well-known tradeoff between ion conductivity and mechanical property hinders its commercial application. Herein, a novel composite polymer electrolyte (CPE) is developed, which is composed of a highly crosslinked polyurethane matrix reinforced with glass fibers for strong mechanical properties, and filled with porous metal-organic framework to boost lithium-ion transport. The CPE with abounding functional hydrogen-bonding and ion-conducting domains, yields a large tensile strength of 66.8 MPa, electrochemical stability window of 5.3 V, a high ionic conductivity of 5.57 × 10⁻⁴ S cm⁻¹ at room temperature, and a good lithium transference number of 0.59. The stable electrolyte interphase formed on the lithium metal (Li) surface enables the Li/CPE/Li cell to maintain performance for an extraordinary 1200 h. Additionally, this CPE based LiNi_0.8Co_0.1Mn_0.1O₂ batteries can achieve an extended lifespan. This design offers a new avenue for the development of CPEs with high ionic conductivity and great mechanical properties to practical high-energy solid-state batteries.