Synthesis, Characterization And Electrochemical Performance Investigation To Cobalt-Based Anode Materials For Lithium Ion Batteries

Lithium ion battery?LIB?has become one of the most important energy storage devices through the development of more than two decades.Though commercialization applications on 3C products?Computer,Communication and Consumer Electronics?and electric vehicles have been achieved,LIB is still far from the rapidly increasing needs on high-rate discharge and long battery life,which need to further improve its energy and power density.Graphite and lithium titanate are two common commercialized anode materials at present,both of which have the disadvantages of low specific capacity and so on.So,both of these materials are difficult to satisfy the requirements of development.In order to find new alternative anode materials,the work here is mainly focusing on the transition metal cobalt-based anode materials and can be separated to be three parts as following:?1?Co₂?OH?₂CO₃@rGO nanosheet arrays grown directly on Cu foil used as anode material for LIB.Materials grown directly on current collector can not only simplify the process to save time but also avoid the use of adhesives to increase the conductivity,which is an effective approach to improve the performance of a battery.In this part,active materials consisted of Co₂?OH?₂CO₃ nanosheets and CoO nanowires and covered by rGO were grown on the Cu foil directly through a hydrothermal reaction.The small amount of rGO plays an important role in the proportion of the two phases.When used as anode for LIBs,the reversible capacity can reach 2,100 mA h g^-1 at 100 mA g^-1 after activation and even as high as 1,240 mA h g^-1 at a much higher current of 5,000 mA g^-1.Additionally,the composite electrode exhibited a high cycling stability,85% of the initial capacity was remained after 100 cycles test at 1,000 mA h g^-1.?2?Fabrication of TiO₂ coated porous CoMn₂O₄ submicrospheres for advanced lithium ion anodes.Volume expansion is a common problem in transition metal oxides during charge/discharge process,which may cause pulverization,leading to dramatic decline in performance.Coating a layer of other material or fabricating special morphology can buffer volume change to some extent.In this part,Co_0.33Mn_0.67CO₃ precursor was firstly synthesized through a solvothermal procedure.After that,CoMn₂O₄ porous submicrospheres was gained by annealing in air.A layer of TiO₂ was finally coated on the submicrospheres through a hydrolysis and polymerization process.When used as anode material for LIBs,the reversible capacity can reach 940 mA h g^-1 at 1000 mA g^-1 after 500 cycles and even as high as 196 mA h g^-1 at a much higher current of 5,000 mA g^-1,which is much better than pristine CoMn₂O₄.?3?Template synthesis of Co₉S₈/C nanoparticles for lithium ion batteries.The morphology of the material can be of great significance to electrochemical performance and template method has an important application in the synthesis of various shapes of the material.In this paper,Co/C nanosheet precursor was firstly synthesized using economical and simple NaCl as template.After sulfuration,Co₉S₈/C was finally obtained,which has smaller particle size,less agglomeration,uniform carbon coating layer and can fully contact with the electrolyte,resulting in enhanced electrochemical performance than Co₉S₈/C prepared without template.When used as anode,the reversible capacity can reach 631 mA h g^-1 at 200 mA g^-1 after 100 cycles and even as high as 362.5 mA h g^-1 at a much higher current of 5000 mA g^-1,which is much better than those of Co₉S₈/C without template.