Lithium-Rich Porous Aromatic Framework-Based Quasi-Solid Polymer Electrolyte for High-Performance Lithium Ion Batteries

The development of solid polymer electrolytes (SPEs) with high ionic conductivity, wide electrochemical window, and high mechanical strength is the key factor to realize high-energy-density solid lithium ion batteries (SLIBs). Porous aromatic frameworks (PAFs) have the advantages of high porosity, easily functionalized molecular structure, and rigid stable framework, which fully meet the requirements of solid polymer electrolytes with high Li+ capacity, fast Li+ transport, and safety. Herein, a lithium-rich amidoxime (AO)-modified porous aromatic framework (PAF-170-AO) was obtained through the absorption of LiTFSI by amidoxime groups and abundant pores and then compounded with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) to prepare a PAF-based quasi-solid polymer electrolyte (PAF-QSPE) with only tiny amounts of plasticizer (∼12 μL). The amidoxime groups of PAF-170-AO restricted the movement of the anions of LiTFSI through hydrogen bonding, which effectively promoted the dissociation and migration number of Li+ (tLi+), reduced the concentration polarization, and inhibited the growth of lithium dendrites. The PAF-QSPE exhibited a high ionic conductivity of 1.75 × 10-4 S cm-1 and tLi+ of 0.55 at room temperature. The activation energy was as low as 0.136 eV. Furthermore, the assembled SLIBs with the PAF-QSPE presented a discharge capacity of 163 mAh g-1 at 0.2 C and a capacity retention rate of 96% after 350 cycles, illustrating a stable cycling performance. This work demonstrated the great application potential of lithium-rich PAFs in QSPEs.