Construction Of Porous Materials For Electrochemical Energy Storage Devices

Energy is an essential material basis for human survival and sustainable economic development.Electrochemical energy storage devices play a vital role in daily life,which can be applied to many portable electronic devices and vehicles.The development of new energy devices is imminent with the exhaustion of non-renewable energy sources.Batteries of hybrid electric vehicles represent one of the important research directions for energy storage systems,and the demand for their high-energy power density and energy density far exceeds that of current lithium-ion batteries or supercapacitors.Therefore,it is necessary to prepare novel materials and construct a rational energy storage system.In various energy storage devices,electrode materials have a decisive effect on the electrochemical performance.Synthesis of electrode materials with nanostructures of different dimensions is an effective solution to improve the electrochemical performance of energy storage devices.Among numerous microstructures,porous nanostructures of the electrode can provide abundant reactive sites and spaces for electrochemical reactions,shorten the charge transport path,increase the contact area between electrodes and electrolytes,reduce electrode polarization,and can effectively inhibit the agglomeration of nanoparticles in the long-term reaction process,which results in good cycling stability.In this thesis,the prepared porous materials are applied to different energy storage devices.The material morphology is characterized by scanning electron microscope and transmission electron microscope.The structure and phase of the material are studied by X-ray diffraction,BET test,X-ray photoelectron spectroscopy,Raman spectroscopy,Fourier transform infrared spectroscopy.Cyclic voltammetry,galvanostatic charge-discharge method and electrochemical impedance spectroscopy are used to study the electrochemical performance of electrode materials.A simple hydrothermal method is used to prepare the conductive Ni₃（HITP）₂（HITP=2,3,6,7,10,11-hexaaminotriphenylene）metal-organic framework material on the copper foil substrate to prepare a three-dimensional conductive current collector.The porous structure and large specific surface area of conductive Ni₃（HITP）₂ materials benefit to promote the transport and uniform deposition of lithium ions,thereby achieving the effect of inhibiting lithium dendrites.The coulombic efficiency of the symmetric cell assembled with Ni₃（HITP）₂@Cu-foil is 99.8%at 100 cycles.The full cell assembled by Li/Ni₃（HITP）₂@Cu-foil anode and lithium iron phosphate（Li Fe PO₄）cathode shows a capacity retention of about 82%even after 1000 cycles.The sulfonic acid-based covalent-organic framework（Tp Pa-SO₃H）film was prepared by an interfacial reaction method,and the zinc anode was stabilized by modifying the zinc metal surface（Tp Pa-SO₃H@Zn-foil）.The sulfonic acid group is attached to the surface of the zinc anode,which facilitates the transport of zinc ions in the porous channel.In half-cells,Tp Pa-SO₃H@Zn-foil exhibits high coulombic efficiencies of over 99%after 1000 zinc plating/stripping processes.Moreover,the full cell assembled with Tp Pa-SO3H@Zn-foil anode and manganese dioxide（Mn O₂）cathode still show a capacity retention of 94.7%and a coulombic efficiency of 99.8%after 1000 cycles.Porous carbon nanosheets（PCNs）were successfully prepared using one-step activation and carbonization of natural tubular dandelion villi using a one-step carbonization activation method.On this basis,Mn O₂ modified PCNs composites were further prepared by in-situ microwave deposition as the positive electrode of asymmetric supercapacitors.The PCNs can promote ion diffusion and electron transport,which helps to improve the rate capability of electrode materials.The asymmetric supercapacitors assembled with PCNs and Mn O₂/PCNs composites exhibited an energy density of 28.2 Wh kg^-1 at a power density of 899.36 W kg^-1and a capacitance retention of 89% after 10,000 cycles.Activated porous carbon tubes（ACTBs）are prepared by a facile carbonization and activation method using dandelion fluff.The polyaniline（PANI）is then modified on ACTBs in situ polymerization.The porous tube structure can shorten the ion transport path of the composite material and increase the specific surface area,which is beneficial to the transport of electrolyte ions and electrons during the polymerization process and improves the rate capability of the electrode material.The asymmetric supercapacitor assembled from ACTBs and PANI/ACTBs composites exhibit a high energy density of 42 Wh kg^-1 and a capacitance retention rate of 96%after 10,000 cycles.The carbon microtubes are prepared by the carbonization method using the metaplexis japonica fluffs as the carbon precursor.Then,the porous tin sulfide（Sn S）nanosheet array composed of abundant microcrystals is further constructed by the solvothermal method to modify the carbon microtube structure.CTAB as the"inducer"during the reaction can form porous Sn S nanosheets with a large number of crystallites（～5 nm）composition,which can provide abundant active sites and shorten the transport paths of electrons and ions and effectively improve the structure stability and sodium storage capacity.As an anode material for sodium-ion hybrid capacitors,Sn S/a CMT exhibits a high capacity of 517 m A h g^-1 at 0.1 A g^-1 and good rate capability(306 m A h g^-1 even at 5 A g^-1)and long-cycle stability（88.7%capacity retention after 500 cycles）.The SHC assembled by Sn S/a CMT anode and a CMT cathode has a high energy density of 115 Wh kg^-1,and the capacity retention rate can still reach 83%after 5000 cycles.Using a solvothermal method,nickel sulfide（NiS₂）nanosheets are composited on the youngia japonica fluffs precursor with tubular structure and further carbonized to prepare electrode materials.This unique tubular structure facilitates the diffusion of electrolyte ions and the conduction of electrons.The NiS₂/p CMT composite electrode for Na-ion batteries exhibits a high specific capacity of 926 m Ah g^-1 at 0.1 A g^-1 and good cycling performance.The asymmetric sodium-ion hybrid capacitor assembled with NiS₂/p CMT as anode and activated carbon as cathode has a high energy density of 136 Wh kg^-1 and still has a capacitance retention rate of 83% after 5000 cycles.