Preparation And Electrochemical Properties Of Carbon-transition Metal-based Nano-micro Materials

The development of clean energy has become the most urgent issue in recent decades due to the large consumption of fossil energy and its non-renewability.Creating new energy storage technologies is critical to the survival and activity of all human beings in the future.In the current energy storage technology,sodium ion batteries have greater development prospects than lithium ion batteries because of their sufficient sodium resources.However,sodium ion batteries still face some difficulties such as slow thermodynamics,large volume expansion,and low conductivity of active materials.In order to get over these problems,carbon composite nanomaterials have recently been successfully used as new electrodes to improve the performance of the battery based on advantages that include stability,high conductivity,and short charge transfer distance.In this thesis,one-dimensional and two-dimensional carbon composite transition metal-based nanomaterials were successfully prepared by simple and easy method,and they were applied to the field of sodium ion battery anode materials to explore their electrochemical properties.In the second chapter,we use phytic acid as the phosphorus source,urea as the carbon source and nitrogen source,cobalt nitrate and nickel nitrate as the transition metal source,and successfully prepare the two-dimensional carbon composite transition metal phosphide mixed nanosheet through the"one-pot boiling"method.This nanosheet successfully couples the transition metal phosphide nanoparticles and the nitrogen-doped carbon nanosheets by the action of covalent bonds,so that the structure of the composite is extremely stable.The sodium storage performance of the TMP/NC nanosheets was tested during the electrochemical test.It exhibits a discharge specific capacity of 411.7 mAh g-1 in the second turn at a current density of 0.1 A g-1,and gradually decays to 334.8 mAh g-1 after ten cycles,and the subsequent 200-turn discharge specific capacity remains stable.With an extremely long cycle life,it’s specific capacity is 180.1 mAh g-1 after 2700 turns at 1 A g-1,and the specific capacity is 135.2 mAh g-1 after 5000 turns at 2 A g-1.In the third chapter,we use Sb2S3 nanorods as precursors,pyrrole as polymerization monomer,phosphomolybdic acid and phosphotungstic acid as initiators,and successfully prepare a variety of one-dimensional carbon composite transition metal Chalcogenide nanotubes by in-situ polymerization coating method.The sodium storage performance of the MoS2/NPC nanotubes was tested during the electrochemical test.It exhibits a discharge specific capacity of 413.4 mAh g-1 after 100 turns at 100 mA g-1.With an extremely stable cycle life,it’s specific capacity is 220.3 mAh g-1 after 2800 turns at 2 A g-1,and the specific capacity is 147.2 mAh g-1 after 5000 turns at 10 A g-1.