The Construction Of Cobalt-based Oxide Nanostructures And Their Electrochemical Properties

Transition metal oxides play an important role in the field of energy storage,such as cell phone batteries,electric vehicles,and so on,due to it high specific capacity.Among of them,Co₃O₄ has drawn increasing attention as a promising alternative anode material owing to its high theoretical capacity?890 m Ah g-1?.However,Co₃O₄ is still far away from real application since it suffers from problems regarding to irreversible capacity loss and poor cycling performance resulting from its intrinsic low electronic conductivity and large volume changes during discharge/charge processes.It is well-known that the nanostructure of the materials can deeply influence their performance,so previous studies demonstrate that various synthesis conditions of the samples especially calcination treatment significantly influence their lithium-storage performance and nanostructure.Firstly,in this paper,the Co₃O₄ nanopillars were fabricated by annealing the precursor of Co?OH?y?CO3?0.5?2-y?·11H2O at various temperatures,which was synthesized by hydrothermal method.[13] The obtained Co₃O₄ samples were characterized by X-ray diffractometer?XRD?,Raman spectroscope and scanning electron microscope?SEM?to study their phases and morphologies.It was found that the Co-450,with the size of 60-100 nm in length and 30-40 nm in width,owns good crystallinity,stable structure and low Rct which can offer low charge transfer resistance.It also delivers good cycle performance with a high reversible capacity of 805.8 m Ah g-1 after 30 cycles at a current density of 100 m A g-1.Secondly,we successful designed a Co₃O₄ nanoarray on Ni foam.It delivers good cycle performance due to the 3D structure of the Ni foam,and provides a high reversible capacity of 2012 m Ah g-1at the first cycle,but it remains only about 818 m Ah g-1 and 577 m Ah g-1,respectively.At last,we successful designed a Co₃O₄@Co₃S₄ heterogeneous structure on Ni foam,exhibiting better lithium-storage performance,including high specific capacity and high conductivity,in comparison of Co₃O₄@Ni foam composite.To our knowledge,Co₃S₄@Co₃O₄ nanoarrays on Ni foam has been utilized in supercapacitor,but there is no report on its application in LIBs.The Co₃O₄@Co₃S₄ nanowires delivers good cycle performance with a high reversible capacity of 1903.1 m Ah g-1at the first cycle at a current density of 200 m A g-1,and it even delivers a high charged capacity of 1565 m Ah g-1.The Co₃O₄@Co₃S₄ nanoarrays with a resulting coulombic efficiency of about 82.25 %.