Morphology Control Of Co 3 O 4 Nanomaterials And Its Effect On Lithium Storage Performance

With the development of electronic devices,lithium-ion batteries(LIBs)with high capacity is expected.Graphite as the classic anode material has already achieved its theoretical capacity limit(372 mAh g-1),it is unable to meet people's requirements for high capacity lithium-ion battery.As a kind of transition metal oxide,Co3O4 with the high theoretical capacity(890 mAh g-1).It has become a hot spot for people to study because of it has high capacity and simple synthesis process.But it has poor conductivity,volume change during insertion/extraction Li+ process and capacity decay fast restricts its practical application in LIBs.In this paper,the work is focused on the preparation of Co3O4 nanostructures and improvement of conductivity,and the development of cycling stability when it is used as anode material during the charge/discharge cycle.The multilayer structure Co3O4 mesoporous nanosheets were obtained by hydrothermal synthesis of Co(OH)2 precursors after heat treatment in air.The nanosheets structure change little during the Li+ insertion/extraction process.The discharge process maintain stable when the charge-discharge current density is 100 mAg-1 after 100 cycles,the capacity can still be maintained at 1067 mAh g-1,the capacity is higher than the theoretical capacity(890 mAh g-1).Even charge and discharge current density of 2 A g-1 after 500 cycles,the reversible capacity can reach 507 mAh g'1.It is found that multilayer structure Co3O4 mesoporous nanosheets preserve their original nanosheets morphologies.It is helpful to the stability charge and discharge cycle when the retention of the material morphology.The Co3O4 nanocubes were synthesized by hydrothermal method.Co3O4 nanocubes have a terrible performance when it was made the anode electrode of lithium ion battery.Co3O4 nanocubes were reduced in the reducing atmosphere,Co3O4 particles which have hollow structure were obtained by the thermal treatment in the air.The hollow structure was favorable for the expansion and contraction of the Co3O4 particles during the Li+ insertion/extraction process.On the other hand,Co3O4 nanocubes and graphite oxide(GO)were compounded under hydrothermal condition,and the GO was reduced and synthesized with Co3O4 nanocubes to obtain Co3O4/rGO composite materials.In the composites,Co3O4 nanocubes were tightly bonded with rGO nanosheets,RGO nanosheets can improve Co3O4 nanocubes conductivity and buffer the Co3O4 nanocubes volume change during charge and discharge process.By the electrochemical test,the Co3O4 particles and the Co3O4/rGO composite materials showed a significant improvement in the reversible capacity,cycling stability and magnification performance.Reversible capacity can still be maintained at 740 mAh g-1 when the charge and discharge current density of 100 mA g-1 after 50 cycles.While the Co3O4 nanocubes has only 241 mAh g-1 under the same test conditions.Co3O4 particles and Co3O4/rGO composite materials have a reversible capacity of 800 mAh g-1duiring variety charge and discharge current density,while the Co3O4 nanocubes has a reversible capacity of 250 mAh g-1.So it is feasible to modify the Co3O4 nanocubes.