Study On The Zinc Storage Performance Of Co/Ni Doped Manganese Oxide Electrode Material

With the utilization of existing energy storage resources,while developing efficient and convenient energy storage devices,environmental friendliness and safety issues have become more severe.Lithium-ion batteries have been widely used due to their ultra-high energy density.However,there are potential safety hazards due to the high cost of preparation,the use of flammable organic electrolytes and lithium dendrites.Aquoeus zinc-ion battery has become a potential alternative energy storage device due to its environmental friendliness,low cost and other advantages.Manganese-based oxides are regarded as popular research objects for zinc-ion battery cathode materials due to its high capacitance,low cost,and environmental friendliness.However,the exposed problems cannot be ignored.For example,the irreversible lattice distortion and disproportionation and dissolution of manganese-based oxide（MnO_x）during the charging and discharging process will lead to poor cycle stability.In this thesis,a systematic study on the dissolution inhibition of manganese-based materials is carried out in this paper in conjunction with related literature:adopt transition metal element doping close to manganese to modify the structure of MnO_xand systematically study its high stability mechanism.Co/Ni is doped in MnO_x（Mn₃O₄,α-MnO₂,γ-MnO₂）mainly by electrodeposition,and then the electrochemical reaction process that inhibits the disproportionation and dissolution of manganese and the irreversible lattice distortion is systematically studied.The energy storage mechanism of the doped manganese-based material always maintaining excellent stability during the charge and discharge process was explained.The research contents are as follows:1.First,a layer of carbon nanosheet arrays（CNAs）is uniformly grown on the surface of the carbon cloth by the method of room temperature immersion.Next,Co-doped trimanganese tetroxide（Co-Mn₃O₄/CNA）nanosheets were deposited on the prepared CNAs by constant potential,and the doping type and doped lattice position of Co in Mn₃O₄were analyzed.Studies have shown that,compared with undoped Mn₃O₄/CNA,the electrochemical performance of Co-Mn₃O₄/CNA has been significantly improved during the charge and discharge process.Combined with density functional theory,it further reveals that multivalent metal ions(Co^2+/3+/4+)doped in the Mn₃O₄lattice coordinately regulate the electronic state of Mn-O,thereby improving the stability of Co-Mn₃O₄/CNA.2.Co-dopedα-MnO₂（Co-MnO₂）was prepared by constant potential electrodeposition on carbon cloth as the cathode material.The electrode material exhibits remarkable electrochemical performance.The most obvious effect of Co doping is to improve the cycle stability of the material.Up to 247 mAh g^-1specific capacity at a current density of 0.1 A g^-1.As even at 4 A g^-1,it has a capacity retention of about 85 mAh g^-1.And returning to 0.1 A g^-1,the capacity retention rate exceeds100%.3.Ni-dopedγ-MnO₂（Ni-MnO₂）was prepared by galvanostatic electrodeposition on carbon cloth as the cathode.The structure characterization technique shows that Ni doping is substitution doping toγ-MnO₂in the form of Ni²⁺.Tests using AC impedance,linear cyclic voltammetry and other related electrochemical methods show that Ni-MnO₂exhibits excellent electrochemical performance.It has a specific capacity of 240 mAh g^-1at 0.1 A g^-1.As even at 10 A g^-1,it has a gratifying capacity retention of about 55 mAh g^-1.Such good rate characteristics are rarely reported for manganese-based zinc-ion batteries.At the same time,at a high current density of 3 A g^-1,the capacity retention rate exceeds 100%after 11,000 cycles(69 mAh g^-1).In summary,the manganese-based material doped with transition metal ions can effectively improve structural stability,thereby exhibiting excellent cycle stability.As a result,this will provide new research ideas for the development of manganese-based electrode materials for high-performance zinc-ion batteries.And it also provides a theoretical reference for the research and development of other energy storage systems.