Morphology-controlled Modification Of Co₃O₄ Nanoparticles And Their Electrochemical Properties

Transition metal oxides have attracted considerable attention as possible electrode materials for lithium-ion batteries.Among them,the high specific capacity of Co3O4(890 mAhg1)as an anode electrode material has attracted great attention of many researchers.However,poor electrical conductivity and volume change during cycling result in low rate capacity and rapid capacity fading,which hinder the practical applications of those electrodes.To solve these problems,Co3O4 nanoparticles(NPs)with three morphologies were successfully synthesized and designed three modification methods for Co3O4 nanocube,which has high control rate of morphology and simple crystal structure.Firstly,we report a facile approach to modify Co3O4 NPs by laser irradiation treatment.Co3O4 NPs were treated by strong laser irradiation.The results show that the surface of the asprepared particles transforms to a thin CoO layer,and oxygen vacancies are generated after the laser treatment.Compared to the as-prepared Co3O4NPs,the unique microstructure induced by laser irradiation,namely,high surface area,special surface composition and oxygen vacancy,promotes the transport of lithium ions and increases the electrochemical activity sites,which is an important reason for improving the performance of lithium storage.Secondly,we designed a modification experiments of gas phase treatment.Co3O4 NPs were annealed at different temperatures in argon atmosphere.The electrochemical properties can be controlled by controlling the thickness of CoO layer and chemical defects(oxygen vacancy)accurately.The results reveal that the thinnest CoO film and oxygen vacancies were generated at 350℃,which exhibit excellent cycle stability and rate performance.Therefore,rational interface modification engineering can create a unique micro-structure and enhance lithium storage properties.Finally,we designed a modification experiment of liquid phase treatment.In this work,we report a facile chemical reduction approach to modify Co3O4 nanocubes by NaBH4 solution treatment.The results indicate that the modified Co3O4 NPs are oxygen deficient,and with the increase of NaBH4 concentration,the crystallinity decreases.When the concentration of NaBH4 solution is 10 mM,the electrochemical properties are optimal.Therefore,the balanced oxygen deficiency and crystallinity in the chemically reduced nanoscale electrodes are responsible for the improved lithium storage properties.The optimal parameters of the above three modification methods were applied to the other two morphologies(sphere and octahedron).The results showed that the electrochemical properties of Co3O4 NPs were greatly improved after modification treatment,indicating that the three different modification methods had a positive impact on the Co3O4 NPs with different crystal structures.