Synthesis Of Al Doped Nickel-Cobalt-based Electrode Materials For Highly Stable Flexible All-solid-state Supercapacitor

With the development of flexible wearable electronic devices,the demand for energy storage devices is higher and higher.Supercapacitor has an irreplaceable position in the new generation of energy storage devices with its unique high power density.However,the low energy density of supercapacitor limits its practical application.In order to improve the energy density,the materials of battery capacitors have been widely studied and applied in supercapacitors.For example,nickel cobalt based electrode materials have been widely studied because of their high specific capacity,but their energy storage process requires redox reaction for under potential chemical adsorption and desorption,which is easy to collapse in the process of use,so the cycle stability is poor.At present,Al doping is an effective method to improve the cycling stability of nickel cobalt based electrode materials.However,the conventional homogeneous coprecipitation method will cause composition segregation due to the precipitation of Al element is not synchronous with other elements,which is not easy to control.In view of this,a rapid precipitation method was developed to prepare Al doped nickel cobalt based electrode materials to improve the electrochemical cycle stability.This strategy can overcome the problem of Al doping segregation or doping failure of nickel cobalt based materials.On this basis,nickel cobalt based cathode materials with high performance were obtained by surface vulcanization,and flexible devices were further assembled to verify the feasibility It’s practical.The main results are as follows:（1）α-Al doped nickel cobalt based oxide（Ni Co-LDH）nanosheets were prepared by rapid coprecipitation method.The effective doping of Al³⁺was realized and the surface sulfurization was carried out to increase the intrinsic activity of the materials.The effects of Al doping and sulfurization on the morphology,structure and growth mechanism were studied.The electrochemical performance of S-NCA_0.1-LDH with10%Al content and surface vulcanization is the best.The specific capacity of S-NCA_0.1-LDH is 727.1 C g^-1at 1 A g^-1current density and 556 C g^-1at 20 A g^-1current density,indicating that S-NCA_0.1-LDH has high specific capacity and excellent rate performance The capacity retention rate is 95.1%when the current density is10000 cycles.There is no obvious change in morphology and crystal structure before and after cycling test,which indicates that the material has good structural stability.（2）S-NCA_0.1-LDH was used as cathode material,commercial AC as anode material,and KOH doped PBI film as electrolyte to assemble all solid state supercapacitor.The effect of positive and negative electrode mass ratio on the electrochemical performance was studied.When the negative positive electrode mass ratio of the device was 1.5,the electrochemical performance was the best,the voltage window could reach 1.8 V,and no obvious side reaction occurred Under the power density of 18000 W kg^-1,the energy density can still reach 42 Wh kg^-1.The results show that the specific capacitance loss rate is less than 10%when the bending radius is0.5 cm,0.25 cm and half fold.Finally,the LED panel lamp is illuminated by the device,which shows a good application prospect.（3）Nickel cobalt based electrode material（Ni（OH）₂@NiCoAl-LDH）with high nickel content and high stability was prepared by coating Ni（OH）₂with NiCoAl-LDH prepared by rapid coprecipitation method.The morphology is cage like.When the current density is 1 A g^-1,the specific capacity is 614.6 C g^-1.At the same time,Ni（OH）₂@NiCoAl-LDH show that the electrode material has excellent cycle stability when it is fully charged and discharged for 5000 times at a current density of 10 A g^-1,and the capacity retention rate is 90.5%.It shows that this method is a feasible strategy to prepare materials with high nickel content and low cobalt content.