Study On Preparation Of Co₃O₄ And NiCo₂O₄ Nanofibers By Electrospinning And Their Electrochemical Properties

Co₃O₄ and NiCo₂O₄ are often used as lithium ion anode materials because of their higher theoretical specific capacity.However,either Co₃O₄ or NiCo₂O₄ prepared by traditional methods has serious problems of agglomeration which limits their performance.In this paper,electrospinning method was used to prepare the precursors of Co₃O₄ and NiCo₂O₄ anode material.Various factors affecting the morphology of the precursor during the spinning process were investigated to obtain the best experimental conditions,and the calcined fiber was used as a negative electrode of a lithium ion battery to study its electrochemical performance.At the same time,the electrochemical performance was compared with NiCo₂O₄ prepared by coprecipitation and sol-gel method.Experimental results show:?1?The best conditions for preparing Co₃O₄ nanofibers are:when the solvent is deionized water?6 mL?+anhydrous ethanol?13 mL?,cobalt nitrate?1.5 g?is used as the cobalt source,and the polymer thickener is PVP?K30 concentration is 36%?,the spinning distance is 20 cm,the positive voltage is 25 kV,the injection speed is 0.1 mm/min,the needle diameter is 0.6 mm,and the humidity is 50%,Co₃O₄ precursor nanofibers with uniform distribution,continuous spinning,no tangles,good morphology and diameter of only 315nm can be obtained.TG-DTA curve and XRD image show that cobalt nitrate decomposes at 255²90?,while PVP decomposes at410⁴90?.After being prepared into a battery,the specific discharge capacity was measured to be 843 mAh/g.After 100 cycles,the specific discharge capacity is still 252 mAh/g;the internal composition resistance is 4.63?.After 5 times'cycling under the current density of magnification respectively,it still has a capacity of 387 mAh/g,indicates that it has excellent magnification performance.?2?The NiCo₂O₄ precursor nanofiber with a diameter of about 400 nm can be prepared using1 g of cobalt nitrate and 0.5 g of nickel nitrate,and the same preparation conditions as Co₃O₄nanofiber.The calcination mechanism of the precursor fiber shows that the decomposition of cobalt nitrate and nickel nitrate occurs at 270³20?,and NiCo₂O₄ with good phase can be formed at600?After calcination,the negative electrode material was measured to have a specific discharge capacity of 1165 mAh/g for the first time and a discharge specific capacity of about 400 mAh/g after 100 cycles;the internal component resistance of the battery is only 3.77?,and the electrochemical performance is much larger improve than Co₃O₄.?3?The morphology of NiCo₂O₄ precursors prepared by electrostatic spinning,co-precipitation and sol-gel methods are very different:the NiCo₂O₄ precursors prepared by electrospinning method is fibrous,the NiCo₂O₄ precursors prepared by co-precipitation method is spherical,and the NiCo₂O₄ precursors prepared by sol-gel method is lamellar.The calcined product were all made to negative electrode materials,and their electrochemical properties were measured.After comparing that the NiCo₂O₄ prepared by electrospinning has better charge and discharge performance stability and has the smallest internal resistance.Under different current densities,the discharge capacity of NiCo₂O₄ prepared by electrospinning after 30 cycles is still at 622 mAh/g stably,much higher than the other two methods of 528 mAh/g and 435 mAh/g.