Layer Phase Transformation Of Manganese-Based Spinel Electrode Materials And Investigation Of Their Electrochemical Properties

Since human society entered the era of industrialization,the demand for energy in the process of social development to meet basic human needs and promote economic growth has been on the rise,and the shortage of non-renewable energy has gradually become one of the unavoidable problems with the continuous development of society.For a long time,the academic community has been committed to the development of renewable long-term energy supply for social development,such as solar energy,wind energy,geothermal energy and so on.However,most of these new energy sources have unstable factors such as timeliness and periodicity,and cannot be directly integrated into the grid for use.As a fast charge-discharge energy storage device with high power density,supercapacitor has become one of the solutions to the above problems.In the research of supercapacitors,studying the electrochemical behavior of electrode materials during the charging and discharging process and obtaining a mechanismlevel explanation can scientifically guide the preparation,compounding and modification of electrode materials,thereby effectively improving the electrochemical performance of supercapacitors.In this paper,the overpotential-induced phase transition behavior of manganese-based spinel was explored,and the phase transition phenomenon of A-site manganese-based spinel was discovered for the first time,and the effect of different A/B-site ion occupancy on binary spinel was systematically studied.The influence mechanism of the overpotential phase transition behavior of active materials is as follows:(1)Two kinds of Mn-Fe spinel were synthesized by co-precipitation method and the phase transformation process was carried out under specific electrochemical conditions.Electrochemically induced layer phase transition in Na2SO4).The electrode samples before and after the phase transition were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and X-ray photoelectron spectroscopy(XPS).The research shows that the two spinel nanoparticle electrodes form a twodimensional network-like morphology wrapped by layer phase after potential activation,which greatly improves the specific surface area and electrochemical reaction active sites of the bulk material.The specific capacitance of the two electrode materials is about three times that of bulk spinel,and Fe-birnessite/FeMn2O4 has a specific capacitance of 256 F g-1 at a current density of 100 mA g-1.In this work,the overpotential phase transition reaction of Mn-Fe binary spinel in neutral electrolyte and the phase transition mechanism of A/B-site manganese-based spinel were studied,which provided a new method for the modification of electrode active materials.new ideas.(2)Three kinds of Mn-Co binary spinel phases were synthesized by electrospinning and the phase transformation process was carried out under specific electrochemical conditions.MnCo2O4,CoMn2O4 and[Co,Mn][Co,Mn]2O4 was found for the first time that they have the phenomenon of different phases of Mn-Co spinel produce layer phase transition under specific electrochemical conditions.The research shows that the prepared three kinds of spinel nano hollow tubes formed a two-dimensional hollow tube network morphology wrapped by layer phase after overpotential activation,which greatly improved the specific surface area and electrochemical reaction active sites of the bulk material,the specific capacitance of the prepared electrode materials has a large increase,and the current density of[Co,Mn][Co,Mn]2O4 mixed with Mn in A and B positions at 100 m A g-1 It has a specific capacitance of 212.3 F g-1 under the electrochemical working window of 0-0.8 V.In addition,the effects of Mn at different positions of the unit cell on the degree of electrochemically induced layer transformation were compared.Various test results showed that the[Co,Mn][Co,Mn]2O4 samples mixed with Mn elements at A/B sites were Under the same electrochemical induction conditions,it has the largest degree of layer phase transition phenomenon.The discovery of the layer phase transition of manganese-based spinel in neutral solution points out a new development direction for the application and development of new supercapacitor electrode materials,electrocatalysis,and electromagnetic shielding materials.