Electrochemical Performance Of Ternary Metal Oxides-carbon Based Network Structures

Since the 21st century,lithium-ion batteries?LIBs?have become the most important power source for mobile phones,laptops and electric vehicles.At present,the continuous development of electric vehicles has put forward higher requirements for lithium batteries?such as large capacity,long service life,fast charging speed,etc.?,which has caused researchers at home and abroad to explore new electrode materials.Because the transition metal oxide has a high capacity under ideal conditions,it is considered by many researchers as an ideal substitute for graphite anode materials for industrial applications.Ternary transition metal oxides such as Zn Co₂O₄,Co Mn₂O₄,Mn Co₂O₄,and Ni Co₂O₄ can usually demomstrate outstanding electrochemical performance because of the synergistic effect of the two metal elements coexisting in single crystal.However,like other transition metal oxides,its conductivity is poor,and the volume change caused by lithium ion insertion/extraction is large,resulting in its fast capacity fading.In this paper,the ternary metal oxides-carbon based network structures were prepared by hydrothermal method.The specific experimental methods and results are as follows:Fe₂O₃-C composite coating with three-dimensional network structure can be prepared on the surface of copper foil by coating and calcining with iron nitrate,pan and PMMA as raw materials.The Fe₂O₃-C composite coating with three-dimensional network structure also has relatively stable performance.Zn Co₂O₄ nano films can be synthesized on the surface of the composite coating by hydrothermal reaction.However,the pure Zn Co₂O₄nanocomposites show unstable cycle performance in the test of electrochemical performance.The composite coating with three-dimensional network structure can provide rich nucleation sites,which is conducive to the formation of non agglomerated Zn Co₂O₄ nanocomposites.Its good conductivity and unique three-dimensional network structure can significantly improve the electrochemical performance of Zn Co₂O₄.In the second part of the experiment,three kinds of high temperature carbonated melamine foam were prepared at first,and all of them had stable electrochemical properties.Among them,the performance of melamine foam carbonized at 700?is more outstanding.Through the test,the melamine foam carbonized at 700?has a three-dimensional network structure composed of 10?m wide carbon skeleton.The foam has a high capacity after the rate performance test.In addition,Cu Co₂O₄ melamine foam composite can be obtained by hydrothermal reaction and subsequent heat treatment with copper nitrate and cobalt nitrate as raw materials.The Cu Co₂O₄ loaded on the surface of melamine carbonate foam is nanowire structure,and its length is about 10?m.Cu Co₂O₄ melamine carbonate foam composite has excellent electrochemical performance,and it can reach 1202 m Ah/g capacity after 100 cycles at the current density of 100m A/g.Because Cu Co₂O₄ can grow into nanowire structure on the surface of melamine foam,its electrochemical performance is effectively improved,and it has high capacity and good cycle stability.However,the electrochemical performance of Cu Co₂O₄ synthesized by hydrothermal method is poor without melamine foam.After 20cycles,the capacity of Cu Co₂O₄decreases rapidly to 33 m Ah/g.