High-Strength MOF-Based Polymer Electrolytes with Uniform Ionic Flow for Lithium Dendrite Suppression.

ABSTRACT

The uneven formation of lithium dendrites during electroplating/stripping leads to a decrease in the utilization of active lithium, resulting in poor cycling stability and posing safety hazards to the battery. Herein, introducing a 3D continuously interconnected zirconium-based metal-organic framework (MOF808) network into a polyethylene oxide polymer matrix establishes a synergistic mechanism for lithium dendrite inhibition. The 3D MOF808 network maintains its large pore structure, facilitating increased lithium salt accommodation, and expands anion adsorption at unsaturated metal sites through its diverse large-space cage structure, thereby promoting the flow of Li+. Infrared-Raman and synchrotron small-angle X-ray scattering results demonstrate that the transport behavior of lithium salt ion clusters at the MOF/polymer interface verifies the increased local Li+ flux concentration, thereby raising the mobility number of Li+ to 0.42 and ensuring uniform Li+ flux distribution, leading to dendrite-free and homogeneous Li+ deposition. Furthermore, nanoindentation tests reveal that the high modulus and elastic recovery of MOF-based polymer electrolytes contribute to forming a robust, dendrite-resistant interface. Consequently, in symmetric battery systems, the system exhibits minimal overpotential, merely 35 mV, while maintaining stable cycling for over 1800 h, achieving low-overpotential lithium deposition. Moreover, it retains redox stability under high voltages up to 5.3 V.