Modified MOF‐Based Composite All‐Solid‐State Polymer Electrolyte with Improved Comprehensive Performance for Dendrite‐Free Li‐Ion Batteries

Solid‐state polymer electrolytes (SPEs) used for Li‐ion batteries have consistently received widely−attention owing to its high safety, excellent flexibility, and good compatibility with electrodes. However, pristine SPEs are difficult to satisfy all necessary demands for the practical applications in high‐performance Li‐ion batteries. Herein, a polycaprolactone modified metal‐organic framework (MOF‐PCL) composite polymer electrolyte (CSPE) is fabricated through the facile UV‐light induced photopolymerization of boronic ester crosslinking monomer (BEM) and poly (ethylene glycol) diacrylate (PEGDA) in the presence of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) and MOF‐PCL. The existence of MOF‐PCL in the electrolyte can not only obviously improve the ion conduction, but also enhance electrochemical stability simultaneously. Besides, the boron‐doped network structure can further promote the transport of Li‐ions. As a result, the obtained CSPE has a higher lithium‐ion transference number of 0.59 and a wide electrochemical window of 5.29 V. Moreover, the LiFePO4/Li cell based on this CSPE also exhibits excellent long‐cycling and rate performance. Undoubtedly, this study not only can provide a new designed method for SPEs with comprehensive performance, but also exhibits a good application potential of this modified MOF‐based CSPE with borate ester in the high‐performance Li‐ion batteries. A modified metal‐organic framework (MOF‐PCL) in the as‐prepared solid electrolyte with a cross‐linked network structure provides efficient pathways for Li‐ions and absorbs impurities to improve electrochemical stability at the same time, while the Lewis acid properties of both central metal of MOF‐PCL and the boron atoms can promote the interaction with TFSI−, further achieving the enhancement of ion conduction.