Boosting lithium-ion conductivity of polymer electrolyte by selective introduction of covalent organic frameworks for safe lithium metal batteries

Abstract

The demand for high-energy-density batteries has prompted exploration into advanced materials for enhancing the safety and performance of lithium metal batteries (LMBs). This study introduces a novel approach, incorporating two-dimensional (2D) pyrazine and imine-linked covalent organic frameworks (COFs) into a polyethylene oxide (PEO)-based solid electrolyte matrix. The synthesized COFs act as multifunctional additives, improving mechanical strength, ionic conductivity (reaching 1.86 ×10−3 S/cm at room temperature), electrochemical window (oxidation resistance up to 5 V vs. Li/Li+), and thermal stability (up to 400 °C). The unique electron-rich and polar functionalities of pyrazine and imine linkages facilitate strong interactions with lithium ions (Li+), resulting in a flexible composite solid electrolyte that mitigates dendrite formation and interface instability. Electrochemical performance of LMBs with LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode further confirm the enhanced Li+ conductivity, prolonged cycling stability, and a stable solid electrolyte interface, showcasing the potential of COFs in improving LMB performance. Overall, this study highlights the promising role of pyrazine and imine-linked COFs as effective additives for polymer-based solid electrolytes and their potential for developing safer and more efficient LMBs in the future.