Preparation And Electrochemical Properties Of MOFs Nanowire/PEO Composite Solid Electrolyte

Composite polymer electrolytes（CPEs）can integrate the advantages of inorganic and polymer electrolytes,showing high flexibility,low interface impedance,easy processing and good ionic conductivity,which are widely favored.MOFs have been used as functional fillers for CPEs in recent years due to their high porosity,flexible design and organic-inorganic hybrid properties.However,MOFs are generally nano/micro particles,their agglomeration in the matrix seriously affects the performance of CPEs.Therefore,designing the morphology and active sites of MOFs,realizing the uniform dispersion of MOFs in CPEs and constructing strong interfacial coupling between MOFs and polymer and Li salt are important methods for preparing high-performance MOFs-based CPEs.Herein,Bi/HMT-MOFs nanowires were synthesized by solvothermal method using Bi（NO₃）₃as metal source and hexamethylenetetramine（HMT）as ligand.Bi/HMT-MOFs nanowires were used as fillers to prepare PEO based composite electrolyte（BMCPEs）.Bi³⁺in MOFs coordinate with PEO oxygen atoms and Li salt anions to form a strong coupling interface,which not only improves the creep ability of PEO segments but also promotes Li salt dissociation.Compared with SPE,BMCPE has wider voltage window（4.8 V）,higher room temperature ionic conductivity(3.06×10^-5S cm^-1)and higher mechanical property（2.14 MPa）.In addition,the Li/BMCPE/Li symmetric cell cycled for 1550 h at 0.2 m A cm^-2and 0.2 m Ah cm^-2.The Li Fe PO₄/BMCPE/Li cell can cycle stable with a high capacity of 124.2 m Ah g-1 and a retention rate of 77.23%after 300 cycles at 1 C.MOFs nanowires with core-shell structure were synthesized by ZIF-8 coated Bi/HMT-MOFs,which further improved the performance of the composite electrolyte:the ionic conductivity at room temperature was 6.73×10^-5S cm^-1,and the electrochemical window was 5 V.The full battery can provide a capacity of107.5 m Ah g^-1at 1 C and can be cycled to 750 cycles.At this time,the specific capacity is 95.2 m Ah g^-1,showing excellent capacity retention.