A Single-Ion Polymer Composite Electrolyte Via In Situ Polymerization of Electrolyte Monomers into a Porous MOF-Based Fibrous Membrane for Lithium Metal Batteries

Single-ion polymer electrolytes have received considerable attention in the development of high-safety and high-energy-density lithium metal batteries due to their high lithium ion transference number, good interfacial compatibility with lithium metal anode, and suppression of lithium dendrite benefits from the immobilization of anions. In this work, we develop a novel single-ion polymer composite electrolyte (SIPCE) by an in situ photoinitiated polymerization of single-ion polymer monomers into porous metal–organic frameworks (MOF)/polymer electrospun fibrous membrane. Experimental results demonstrate that the received SIPCE-MOF exhibits a high lithium ion transference number of 0.80, a wide electrochemical stability window up to 5.68 V, and the remarkable ionic conductivity of 1.14 × 10–5 and 2.23 × 10–5 S cm–1 at 30 and 60 °C, respectively. In addition, the lithium symmetrical battery with such SIPCE-MOF shows a polarization voltage of 120 mV at a current density of 2 mA cm–2 and a stable cycling time of more than 2200 h, implying the excellent long-term lithium plating/stripping performance. As a result, the solid-state LiFePO4/SIPCE-MOF/Li battery achieves an unparalleled rate performance (105 mAh g–1 at 2 C) and maintains 98.3% of its initial capacity after 120 cycles with a superhigh Coulombic efficiency of 99% at 0.5 C. These excellent properties provide great potential for the application of single-ion polymer composite electrolytes in solid-state lithium metal batteries.