Research On Nickel-cobalt Dual-ligand MOFs In Efficient Tunable Wave Absorbing Properties And Gel Electrolytes

Energy consumption and environment protection are significant aspects that influence the sustainable development of society.Typical examples include the expansion of various electronic and communication devices over the past few decades.These technologies undoubtedly facilitate and enrich daily life,but issues related to energy use and environmental protection should be addressed simultaneously,and in both respects,there is an urgent need for multifunctional materials with both excellent lithium storage and electromagnetic wave absorption capabilities.As a novel framework material,MOFs are widely used in electromagnetic wave absorption,gas adsorption,energy storage materials and other fields.In this paper,a nickel-cobalt dual ligand MOF was successfully prepared.After carbonization,the core-shell double-carbon layer MOF derivative can be perfectly maintained.In addition to the skeleton structure,it has excellent adjustable microwave absorption performance.At the same time,in terms of energy storage,the nickel-cobalt dual ligand MOF is used as the filler of the epoxy resin matrix,and the epoxy resin is composited with PVDF-HFP spinning membrane.The composite gel electrolyte can maintain excellent mechanical properties while maintaining good electrochemical properties after electrolyte activation,which expands the direction for the multi-functional application of MOF materials.Firstly,by changing the mass ratio of the second ligand of the shell nickel-based MOF to nickel chloride hexahydrate,can form nickel-cobalt dual-ligand MOFs with different morphologies from sea urchin-like,rod-like,petal-like,etc.The reaction conditions were used to explore the growth mechanism of its morphology.Due to the special double-skeleton structure,the dual-core-shell carbon layer structure formed after carbonization maintained the original shape,while the nickel-cobalt nano-metal was embedded in the carbon layer to form double-layer magnetic loss and dielectric loss of the inner and outer layers.The impedance matching of nano-fillers was enhanced and its wave-absorbing performance was improved.When the ligand ratio was 1:2 and 1:4 with filler addition of 40%,the optimum reflection loss and frequency bandwidth of the nickel-cobalt dual-ligand MOF derivatives reached their peaks respectively;the optimum reflection loss reached-70.70 d B,and the maximum frequency bandwidth was 5.92 GHz.When the filler content was 50%,When the ratio of the second ligand of the nickel-cobalt dual-ligand MOF derivative to nickel chloride hexahydrate is 1:6,the optimal reflection loss and frequency bandwidth of the nickel-cobalt dual-ligand MOF derivative are both achieved at this ratio.The best reflection loss reaches-58.40 d B.At the same time,the growth mechanism of MOF and the relationship between its special structure and electromagnetic wave absorption mechanism are explored in depth,in order to expect its application in practical production and life.Secondly,by adjusting the addition quantity of the pore-forming agent to explore the change trend of the microscopic morphology of the composite membrane surface and the cross-sectional morphology,a composite membrane with a suitable microporous structure was obtained.The change trend of the mechanical performances and electrochemical properties of the composite separator was obtained,and the separator with the best filler content was obtained.Due to the combination of the excellent mechanical properties of epoxy resin and the advantages of PVDF-HFP in lithium salt ionization and carrier concentration,by introducing nickel-cobalt dual ligand MOF as the filler of epoxy resin matrix,a composite diaphragm was prepared by combining the PVDF-HFP electrospun film and the epoxy resin matrix,this can act as a bridge to enhance the bond between layers,which synergistically improve the mechanical performances as well as electrochemical properties of the diaphragm.In addition,the fibers presented vertical arrangement in the membrane layer.With the effect of the pore-forming agent,the synergistic effect of the composite membrane micropores and the fiber membrane can greatly improve the transmission efficiency of Li ions.The comprehensive performance of MOF-7%@EP@PVDF-HFP membrane reached the best,the liquid absorption rate reached 376%,and the ionic conductivity reached 2.22×10^-3 S cm^-1,all reaching the peak value.The electrochemical window reaches 5.03 V,and the migration number reaches 0.696.