Study On Inkjet Printing Conductive Substrate Supported Ni-Co LDH For Supercapacitor Performance

Supercapacitors have drawn particular concern in electronic systems due to its high power density,good stability,long cycle life,low energy consumption and environmental friendliness.Currently,these electronic systems are undergoing a major shift from rigid devices to flexible,portable and scalable electronic devices.Printing technology(inkjet printing,screen printing and 3D printing)offers same manufacturing advantages as simple,low-cost,time-saving,versatile and environmental friendliness for supercapacitors.Among them,inkjet printing with non-contact,high-precision and on-demand processing method provides a possibility for large-scale industrial processing of flexible energy storage devices.However,with the increasing demand for multi-function of storage electronic products,printable conductive ink has developed rapidly due to its advantages of high conductivity,high optical transparency and thermal stability.In this paper,the inkjet printing method with the advantages of non-contact,digitized precision,compatibility with a variety of substrates and low material consumption were effectively combined with electrochemical deposition method to achieve the combination of flexible substrate surface-conductive layer and conductive layer-active materials on the substrate surface.Hence,this paper mainly prepared conductive inks of unifomity,stability and suitable physical properties,which were printed on different current collector as a new conductive supporter to support the upper Ni-Co LDH.The prepared samples were used as the positive electrode materials and carbon materials as the negative electrode materials to assemble the asymmetric supercapacitor and assess the electrochemical performance.The research contents are as follows:The modified Hummer's method was used to prepare graphene oxide(GO),and the reduced graphene oxide(rGO)was obtained by simple room-temperature-reduction process.Then,the conductive graphene film and Ni-Co LDH were prepared on rigid nickel foam(NF)by combining the inkjet printing and electrochemical deposition method.The Ni-Co LDH/rGO with the two layers was prepared by combining the advantages of inkjet printing and the idea of layer-by-layer construction.Compared with the Ni-Co LDH/rGO electrode material,the Ni-Co LDH/rGO with two layers electrode material has higher electrochemical performance,as the specific capacity of 227 mAh/g at the current density of 1.2 A/g.The assembled asymmetric supercapacitor has the energy density of 84.9 Wh/kg and power density of 424 W/kg.According to the attractive characteristics of inkjet printing,the NF was replaced with flexible carbon cloth(CC)as the current collector to further fabricate Ni-Co LDH/Ag/rGO electrode material.Firstly,silver nanoparticles(Ag NPs)were prepared by hydrothermal method.GO and Ag NPs layers were constructed on the CC by inkjet printing,and the rGO was formed and the adhesive force was increased via the high-temperature calcination.Furthermore,the Ni-Co LDH with the outstanding theoretical specific capacity was deposited on Ag/rGO,which achieves the specific capacity of 173 mAh/g at current density of 1 A/g,and the assembled asymmetric supercapacitor has the energy density of 76 Wh/kg and power densityof 480 W/kg.The rGO and multi-wall carbon nanotubes(CNTs)ink were printed on A4 paper by all inkjet printing,and conductive Ag NPs were further printed to improve the conductive of electrode materials.The Ni-Co LDH was prepared via a step of hydrothermal process,and Ni-Co LDH ink was spread firstly to rGO ink for forming the uniform Ni-Co LDH-rGO ink.In the printed process,the CNTs-rGO can intimately interact with Ni-Co LDH-rGO through?-? stacking to increase the overall conductivity and stability of material.The electrode material realizes the specific capacity of 142 mAh/g at current density of 1 A/g,and when the current density reaches 50 A/g,the specific capacity still reaches 106.9 mAh/g.At the same time,the asymmetric supercapacitors were first assembled by printing the CNTs and rGO ink on graphite paper as negative electrode materials.The energy density of the assembled asymmetric supercapacitors can reach 49.8 Wh/kg at the power densityof 800 W/kg.