Effect of Surfactant on Morphology and Supercapacitor Properties of NiMn₂O₄ Electrode Material

The morphology of nanomaterials can affect their electrochemical performance. It is a challenge to design metal oxide nanostructures with controllable morphology/size and good electrical conductivity for their application in electrochemical supercapacitors and other energy storage devices. NiMn₂O₄ electrode materials with different amounts of polyvinylpyrrolidone (PVP) were prepared by a co-precipitation method. The effect of PVP (0, 0.2, 0.4, 0.8 g) amount on the microstructure and capacitance properties of NiMn₂O₄ was investigated. The results show that the microstructure of NiMn₂O₄ changes from an agglomerated granular to loose flocculent and fine powder with the increase of PVP content. The optimum capacitance performance of NiMn₂O₄ can be obtained at PVP amount of 0.4 g, and the specific capacitance of NiMn₂O₄ is 1464 F/g at a current density of 1 A/g. At PVP amount of 0.8 g, the excessive amount of PVP is easy to cause residue in NiMn₂O₄ in the cleaning process. During the electrochemical test, the amount of active substances involved in the redox reaction is relatively reduced, leading to the decrease of the capacitance performance of NiMn₂O₄-0.8. The specific capacitance is 1010 F/g when a current density is 1 A/g.