Construction Of Cobalt Oxide Composite Micro/Nanostructured Materials And Assembly Of Lithium Ion Battery

Due to the low self-discharge rate,high energy density and light weight,lithium-ion batteries?LIBs?have been widely used in lots of devices for human life.However,the theoretical capacity of commercial graphite anode materials is low,which hinders the further development of LIBs to some extent.Fortunately,owing to the high energy density,environmental friendliness and low cost,cobalt oxides are regarded as one of the most promising anode materials to replace graphite.However,the large volume change and inferior conductivity of cobalt oxides have been limited their commercial developments.Research shows that the above defects can be effectively overcome via rational morphology controlling of materials and construction of composite materials.Metal-organic framework compounds?MOFs?with large specific surface area,controlled pore structure and composition have been considered as ideal templates for the preparation of metal oxides and their composites.Based on these performances,the following four kinds of cobalt-based oxides were constructed by using MOFs as templates followed by the reasonable heat treatment,furthermore,structures and electrochemical properties were explored.The PAN/ZIF-67 composite nanofibers were prepared by the combination electrospinning with in situ growth method.Then,the hierarchical porous CNFs/Co₃O₄composite nanofibers were fabricated by using subsequent multi-step thermal treatment.The hierarchical porous CNFs/Co₃O₄-1 demonstrates high capacity of 1352 mAh g^-11 and 661 mAh g^-1 at 0.2 and 2 A g^-1 up to 500 cycles,respectively.Moreover,the composities show excellent cyclical stability.The Co₂?OH?₂CO₃@ZIF-67 precursor was directly grown on the copper foil by combining hydrothermal method with in situ growth method.Subsequently,porous Co₃O₄with the Cu foil substrate as a self-standing electrode was obtained through heat treatment.The as-fabricated self-standing electrode is directly used as an anode with excellent electrochemical performance for LIBs,achieving a high specific capacity of 2327 mAh g^-1 at0.1 A g^-1 after 100 cycles.In addition,the prepared self-standing electrode exhibits superior rate performance.The Co₂?OH?₂CO₃/ZIF-67 precursor was directly grown on the copper foam by hydrothermal method combined with in situ growth method.The porous bell orchid-like Co₃O₄/CuO with the Cu foam substrate as a self-standing electrode was fabricated by using subsequent heat treatment.The as-obtained self-standing electrode is directly used as an anode of LIBs,which exhibits a capacity of 1057 mAh g^-1 at a current density of 0.1 A g^-1 after 100cycles,and superior cyclic stability.The electrospinning combined with in situ growth method was used to fabricate PAN/Zn-Co-ZIFs composite nanofibers.Subsequently,the CNFs/ZnCo2O4 composite nanofibers were obtained by a multi-step heat treatment.The CNFs/ZnCo₂O₄-1 shows a capacity of 641 mAh g^-1 at a current density of 0.1 A g^-1 up to 500 cycles,and a capacity of 385 mAh g^-1 was achieved even at a current of 1 A g^-1,which shows a great rate performance.