Preparation And Performance Enhancement Of Lithiated Covalent Organic Framework Composite Polymer Electrolyte

Solid electrolytes are the key part of solid-state lithium-ion batteries,which have attracted much attention due to their high energy density and superior safety.Polymer electrolytes are the most commercial solid electrolytes,but still limited by low ionic conductivity at room temperature.In this research,a kind of lithiated covalent organic framework is selected as the active filler,with poly（ethylene oxide）（PEO）as the matrix,to prepare composite polymer electrolytes（CPEs）.Lithated COF has a regular one-dimensional channel structure with uniformly distributed lithiation sites.It can reduce the lithium ion diffusion energy barrier by building a fast lithium ion conduction channel.Lithated COF can further reduce the PEO crystallinity to enhance electrochemical performance at a higher filling amount.The main research results are as follows:Preparation and electrochemical performance enhancement of lithiated COF composite PEO-based solid electrolyte:1,3,5-triformylphloroglucinol（Tp）and 2,5-diaminobenzenesulfonic acid（Pa-SO₃H）was used to prepare imine-linked Tp Pa-SO₃H by solvothermal method.Tp Pa-SO₃Li was obtained by chemical lithiation strategy and used as an active filler for CPEs.Tp Pa-SO₃Li provides repid Li-ion transfer via the regularly arranged lithiation sites in the channels.Meanwhile,it can stabilize the interface between CPEs and the electrodes,and reduce the interfacial reactions.With an ultra-low filling amount of 0.75 wt%,the CPE obtained an ionic conductivity of3.01×10^-4 S/cm at 60℃.When the CPE was applied in Li Fe PO₄ all-solid-state batteries,the cell delivered a stable capacity of 125 m Ah/g after 250 cycles at 0.5 C,60℃.The mechanical preparation and electrochemical performance enhancement of lithiated COF and its composite polymer electrolyte:By solvent-free ball milling method,the production capacity of Tp Pa-SO₃H was significantly improved:Tp Pa-SO₃H was prepared in gram-scale and the preparation time was shortened from 72 h to3 h,Tp Pa-SO₃Li was obtained by chemical lithiation strategy.Through the mechanical mixing and calendering method,the preparation time of CPEs was shortened to 30minutes.The holes and defects on the surface of CPEs caused by solvent volatilization were avoided,as well as the agglomeration and sedimentation of Tp Pa-SO₃Li in the solution.The use of purely mechanical methods avoids the use of organic solvent in the preparation process and is environmentally friendly.In addition to providing repid Li-ion transfer,Tp Pa-SO₃Li can also inhibit the orderly arrangement of PEO segments to reduce the crystallinity of CPEs.The ionic conductivity of CPEs with 10 wt%Tp Pa-SO₃Li at 20℃reached 9.51×10^-6 S/cm,which was about 13 times higher than（PEO）₁₂Li Cl O₄.Tp Pa-SO₃Li improved the interface contact between the CPE and the electrodes,which improved the performance of all-solid-state lithium-ion batteries.