The Preparation And Eelectrochemical Performance Of MnO₂ Assisted With Pulse Electromagnetic Field

Manganese dioxide?MnO₂?is a kind of important inorganic functional materials.It has been widely used in the study of supercapacitors,Li-ion batteries and zeolites,and has attracted the attention of the researchers.Currently,the researchers mainly study the crystal form,morphology and doping modification of MnO₂.In this paper,preparing MnO₂ is used redox conditions assisted with pulse electromagnetic field and doping.The evolution of crystal and morphology are controlled and the different process conditions on the electrochemical performance of MnO₂ were studied.The effects of redox conditions on the MnO₂ are studied in this paper.Results show that nano flower-like?-type,nanowire?-type and nano-particulate?-type MnO₂ powders can be prepared by changing the molar ratio,reaction temperature and reaction time.The optimum reaction conditions are as follows:at the temperature of 90?for 2h,the molar ratio of KMnO₄ to MnSO₄ is 2:3,the?-type MnO₂ powders with high crystallinity and uniformly distributed can be obtained.On the basis of redox conditions,the effects of pulse parameters on the MnO₂ are studied.Results show that MnO₂ powder is?-type with low purity and uneven distribution without PEF.And the MnO₂ powders are all nano-particulate?-type with PEF.The best pulse parameter is 400V,3Hz,90s,the particle size is about 10nm.In order to further improve the electrochemical performance of MnO₂,the MnO₂ is dopted with Fe by PEF.Results show that the MnO₂ powder is?-type without PEF.Then the crystal form of MnO₂ powder is transform from?-type to?-type with PEF,and the morphology change from nano-particles to nanoscale-rods,the length are about 50⁸0nm.The effects of the products of different reaction conditions on the electrochemical properties of MnO₂ electrode materials are studied.Results show that the specific capacity of?-PEF-MnO₂?PEF?reaches maximum?1750F/g?,but the specific discharge capacity of?-MnO₂,?-MnO₂ and?-MnO₂ are 570F/g,467.5F/g and 437.5F/g respectively at the current destinyof1A/g.Theinternalresistancefromsmalltolarge:?-PEF-MnO₂<?-MnO₂<?-MnO₂<?-MnO₂.A specific discharge capacity of 1560F/g is obtained?MFe?,the value is 52%higher than that of the undoped MnO₂?M?at the current destiny of 2A/g.Meanwhile,the internal resistance of MFe is less than M,which indicate that nano-rod?-MnO₂ possesses electrochemical performance.