Intrinsic ion-storage pendent and UiO-66-NH₂ based anion tethering: Ether-ester-urethane linkage composite polymer electrolyte for lithium batteries

Polymer electrolytes (PEs), owing to their high flexibility, enhanced processability, and compatibility with lithium metal (Li⁰) anodes, are promising chemical feedstock advancements for lithium batteries. However, low mechanical strength, transference number, ionic conductivity, and narrow electrochemical stability limit the widespread use of PEs. Herein, the strategy of anion tethering in ester-urethane linkage PE is introduced to prepare composite polymer electrolyte (CPE) via intrinsic PEGylated ion-storage pendant regulation and UiO-66-NH₂ frameworks incorporation. The CPE with tethered anions and different interatomic interactions rendered increased mechanical strength, a high transference number (t⁺) of 0.84, selective Li⁺ conductivity, and expanded electrochemical stability window. Molecular dynamics simulations have been performed to reveal the dynamics of diffusion for Li⁺ with and without UiO-66-NH₂ in the electrolytes. The t⁺ has a significant impact on the deposition behavior of Li⁰; the low t⁺ dual-ion electrolyte produced a porous morphology with Li⁰ non-uniform grains, whereas CPE produced a homogeneous, compact morphology. Additionally, the tethered anions and UiO-66-NH₂ contribute to stable SEI formation with reduced organic decomposition on the Li-metal surface. Using the CPE, Li⁰||Li⁰ and Li⁰||LiFePO₄ cells present stable cycling performance. The synergistic interatomic interactions dictating physicochemical and electrochemical properties of the CPE could be envisioned as a promising design route.