Preparation And Electrochemical Properties Of Cobalt Oxide With High-capacity For Lithium-ion Batteries

Cobalt oxides（CoO、Co₃O₄） have long been promising alternative anode materials tographite, which have higher theoretical specific capacity (716and829mAh g^-1).However, this kind of oxide anode material usually suffers from poor electronicconduction and cycle performance, and hence needs to be modified by admixingelectronically conductive phases or constructed different nanostructured electrodematerials. In this dissertation, we have sucessfully fabricated CoO porous nanospindles/graphene nanocomposites and well-alligned NiCo₂O₄nanorod arrays with a Cu collectoror without a collector. The morphology of the samples was observed by scanning electronmicroscopy （SEM）. The crystallographic structure of the samples was characterized byX-ray diffraction （XRD）. The cycling performance and charge-discharge curves wereevaluated by battery tester. The detailed contents are as following:Firstly, the CoO porous nanospindles/graphene composites have been successfullyprepared by a two-step process involving solvothermal crystallization and post synthesisself-assembly under mild reaction conditions. All the diffraction peaks of the finallyproducts can be indexed as the cubic CoO by XRD. From SEM, it can be clearlyobserved that these CoO nanospindles all have the uniform spindle-shaped morphology.When evaluated for Li-storage properties, the composite electrode showed a high initialdischarge capacity (about1092mAh g^-1at a current of0.1C) and excellent cyclicperformance (a stable high specific reversible capacity of around700mAh g^-1, which wasnearly unvarying over20cycles).Secondly, we reported a mild and cost-effective solution method to directly growNi-substituted Co₃O₄（ternary NiCo₂O₄） nanorod arrays on Cu substrates. The resultsshowed that ternary NiCo₂O₄presented well-aligned1D nanorod microstructure. Thedoped nickel replaced part of cobalt from Co₃O₄, which indeed improved the electronicconductivity. So these ternary NiCo₂O₄nanorod arrays manifest high specific capacity,excellent cycling stability (a high reversible capacity of about830mAh g^-1was achievedafter30cycles at0.5C) and high rate capability (787,695,512,254,127mAh g^-1at1C,2C,6C,50C and110C, respectively).Thirdly, we have successfully fabricated ternary NiCo₂O₄by self-assemble process.Typical the NiCo₂O₄urchins were composed of mumerous small nanorods radially grownfrom the center, simillar with nature dandelion. The electrochemical tests resulted that this NiCo₂O₄anode showed high specific capacity and excellent cycling stability. At arate of0.1C, the fist irreversible capacity is2317mAh g^-1. After65cycles, a stable highcapacity of1132mAh g^-1can be resumed.