Preparation And Electrochemical Performance Of Cerium-doped Hydrotalcite-like Composite Materials

In recent years,global climate change has led to a significant increase in the frequency and intensity of extreme weather,posing a huge threat to human survival and development.China has put forward the goal of“carbon peak”in 2030 and“carbon neutral”in 2060.It has become the consensus of the international community to develop and utilize clean energy such as wind,water,nuclear and solar energy to achieve energy conservation and emission reduction.These clean energy has the characteristics of seasonality and timeliness,which requires reasonable energy storage in order to achieve stable and sustainable energy output.Therefore,to realize the efficient utilization of new energy lies in the innovative development of energy storage materials and equipment.Supercapacitor is a new type of electrochemical energy storage equipment,whose advantages including high power density,long cycle life,fast charging and discharging,safety and environmental protection.Hydrotalcite(LDHs)materials are supercapacitor materials with application prospects,but there are still many shortcomings in terms of conductivity and cycle stability,which limit their development in the application of energy storage materials.In this paper,the rare earth element Ce was compounded with LDHs to prepare a cerium-doped hydrotalcite-like composite material to improve the electrochemical performance of LDHs.The structure and morphology of the material was characterized by XRD,XPS,SEM,FT-IR and EDS.The electrochemical performance of materials was detected by CV,GCD,EIS and cycle performance.and improved their market application capabilities.Firstly,Ni-Al LDHs was used as the research object,and different amounts of Ce2(SO4)3·8H2O were selected and added to the mixed solution of Ni SO4·6H2O and Al2SO4·18H2O,a layered composite of Ni-Al LDHs/Ce(NAHCe)was synthesized by a one-step hydrothermal method.Compared with NAH,NAHCe-2.5 with the optimal dosage of Ce had a larger specific surface area(113.20 m²·g^-1),total pore volume(0.47 cm³·g^-1)and average pore size(12.45 nm).According to the electrochemical test results,we can know that the specific capacitance of Ni-Al LDHS is 541.82 F·g^-1 at the current density of 1 A·g^-1,while the specific capacitance of NAHCe-2.5 was879.63 F·g^-1 at the current density of 1 A·g^-1.The specific capacitance of NAHCe-2.5is 396.82 F·g^-1 at the high current density of 20 A·g^-1,and the capacitance retention rate at 2 A·g^-1 can reach 90.36%after 1000 cycles.Combined with the EIS pattern,compared with the Ni-Al LDHs without Ce addition,the NAHCe composite has a smaller charge transfer resistance.Ce doping can increase the specific surface area of LDHs to provide more electrochemical reaction sites,while effectively preventing the collapse of the layered structure,thereby improving the energy storage performance of the material.Secondly,Co-Al LDHs was used the research object,the Ce-doped Co-Al LDHs materials were prepared by hydrothermal method,and the influence of Ce doping amount on the electrochemical performance of Co-Al LDHs was studied.The electrochemical test results showed that the specific capacitance of Co-Al LDHs was407 F·g^-1 at 1 A·g^-1,while the specific capacitance of Co-Al LDHs with optimal Ce doping can reach 560 F·g^-1 at 1 A·g^-1,and it still had a capacitance retention rate of85.9%after 3000 cycles of charging/discharging.The EIS test showed that CAHCe-2had the smallest semicircular arc diameter,which represents the smallest charge transfer resistance and more likely to react with ions in the electrolyte.It fully proved that CAHCe-2 has the most excellent electrochemical performance.The rapid redox reaction of Ce³⁺/Ce⁴⁺in CeO₂ further expedited the electron transfer rate between the Co-Al LDHs layered structure,and can greatly improve the cycle stability of CoAl LDHs.On the basis of the above research,the CeO2 composite Co-Al LDHs active material was grown on the foamed nickel base material by hydrothermal method to form a unique cactus-shaped structure electrode CeO2@CoAl LDHs-NF,without the use of adhesives,it can be used directly as a super capacitor electrode.Electrochemical test results showed that the CeO2@CoAl LDHs-NF electrode with an area of 1 cm^-2 had specific capacitances of 5.246,4.122,2.534,1.668 and 1.136F·cm^-2 at current densities of 5,10,20,30 and 40 m A·cm^-2,with good rate performance.The coulomb efficiency of CeO2@CoAl LDHs-NF electrode material was still as high as 99.18%after 3000 cycles of charge/discharge at a high current density of 20 m A·cm^-2.The EIS spectrum showed that the charge transfer resistance of CeO2@CoAl LDHs-NF was the smallest,which was more conducive to the transmission of electrons.Compared with traditional supercapacitor cathode materials which were mixed with active materials,binders and conductive additives,which caused problems such as low ion and electron diffusion efficiency,CeO2@CoAl LDHs-NF electrode materials had good cycle stability and application prospects without binders.The above studies proved that the doping of LDHs with a certain amount of Ce can availably enhance the electrochemical behavior of LDHs,and the synergistic effect between CeO2 and LDHs composite material made it had outstanding electrochemical performance.The cactus-shaped CeO2@CoAl LDHs-NF electrode material synthesized by the hydrothermal method without adding a binder can be directly used for supercapacitor electrodes,which provided a new idea for the optimization of supercapacitor electrode performance.