| Many advances have been made in the study of binary metal oxides and their graphene composites,but there are still many problems such as complicated preparation methods and insufficient capacity.Therefore,it is still difficult to synthesize binary metal oxides and their composites by simple methods.In this paper,binary transition metal oxide/graphene composites are taken as the research direction.The preparation,mechanism and electrochemical properties of binary transition metal oxides and their graphene composites were studied systematically.CoMn2O4 nanometer electrode materials were prepared by coprecipitation method with deionized water,50%deionized water mixed with 50%ethanol and ethanol as solvent respectively,The phase structure,morphology and electrochemical properties of the three samples were studied.The results showed that the CoMn2O4 material prepared with ethanol had loose and porous granular structure and poor crystallinity.CoMn2O4 material with 50%deionized water and 50%ethanol as solvent has particle and flake hybridstructure.CoMn2O4 material prepared with pure water as the solvent has sheet structure and good crystallinity.The granular porous CoMn2O4 material prepared with ethanol as the solvent has more excellent supercapacitor performance due to its loose and porous structure.CoMn2O4/rGO composites with different graphene contents were prepared by using 50%deionized water and 50%ethanol(percentage by volume)as solvent.Compared with pure CoMn2O4,CoMn2O4/rGO20 samples with 20%graphene content have the maximum specific capacitance,better multiplier performance and cycling stability.Porous NiMn2O4 electrode materials were prepared by solvent thermal method with urea and ammonia as precipitators,respectively.The phase structure,morphology and electrochemical properties of the two electrode materials were studied.The flower-shaped NiMn2O4 nanomaterial prepared with urea as the precipitator has a larger specific surface area and pore diameter,and the contact area between the electrode material and electrolyte is larger,which is conducive to electron transfer,the electrochemical performance of the material is better.NiMn2O4/rGO composite was prepared with deionized water as solvent.NiMn2O4/rGO composite had a specific capacitance of 1360 F g-1 at 1 A g-1,the specific capacitance of the the pure NiMn2O4 powder is 924 F g-1.When the current density increased from 1 A g-1 to 10 A g-1,the specific capacitance retention of NiMn2O4/rGO composite was 62%,while the specific capacitance retention of pure NiMn2O4 powder was 45%.NiMn2O4/rGO samples have good electrochemical properties.NiMn2O4/rGO composite material was prepared with ethanol as solvent.Compared with NiMn2O4/rGO with deionized water as solvent,the size of NiMn2O4/rGO prepared with deionized water was more than 10 times larger than that of NiMn2O4/rGO prepared with ethanol as solvent,and the crystallinity was better.The NiMn2O4/rGO composites prepared with ethanol as solvent are porous and have poor crystallinity.In terms of electrochemical properties,NiMn2O4/rGO composites prepared with ethanol as solvent have higher capacitance,while NiMn2O4/rGO prepared with deionized water as solvent has good rate performance.Porous MnCo2O4 electrode materials were prepared with nitrate and chloride as reactants respectively.The phase structure,morphology and electrochemical properties of the two samples were studied.The results showed that MnCo2O4 material prepared with nitrate as the reactant showed better capacitive performance,MnCo2O4 material prepared with chlorine as the reactant showed good rate performance.MnCo2O4/rGO composite prepared with chlorine salt as the reactant,the specific capacitance of MnCo2O4/rGO sample at 1 A g-1 is 1521 F g-1,while the specific capacitance of pure MnCo2O4 sample at 1 A g-1 is 892 F g-1,the current density increases from 1 A g-1 to 10 A g-1,MnCo2O4/rGO specific capacitance retention rate is 57%,pure MnCo2O4 specific capacitance retention rate is 51%,MnCo2O4/rGO sample has good electrochemical performance.The CuCo2O4 electrode material was prepared by hydrothermal method.The influence of calcination temperature on the phase structure,morphology and electrochemical properties of the CuCo2O4 electrode material was studied.The results showed that the CuCo2O4 material prepared by calcination at 350? had the lowest crystallinity.SEM analysis shows that when calcination temperature is 350? CuCo2O4 presents a two-dimensional lamellar structure,more gaps and channels are formed between lamellar,and electrochemical performance is the best.CuCo2O4/rGO composite material was prepared,The nano-scale CuCo2O4 particles were deposited on the graphene sheet with low crystallinity,which improved the surface/volume ratio and the utilization ratio of CuCo2O4 electroactive components.The electrochemical properties of the materials,especially the rate properties have been greatly improved.There are 82 figures,3 tables and 121 references in this paper. |
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