Synthesis Of Composite Transition Metal Oxides Via Hydrotalcite-precursor Method And Their Lithium Storage Performance

Nowadays,energy issue is the focus and hot topic of common concern all over the world.Green,efficient lithium-ion batteries are already shining in the fields of portable electronics,battery-powered cars and electrochemical energy storage.However,the anode material(commercial graphite),which plays an important role in lithium ion batteries,has the disadvantages of high initial irreversible capacity and low reversible capacity in the process of repeated charging and discharging,which limits the further development of lithium ion batteries.Transition metal oxides usually have a high theoretical specific capacity,which can make up for the low reversible capacity of commercial graphite.However,single-component transition metal oxide electrode materials usually have problems such as poor cyclic stability and serious particle agglomeration under high current density,and the combination of them with good electrical conductivity carbon materials or non-electrochemical activity metal oxides is one of the effective ways to solve the above problems.The traditional preparation methods are complex and complicated,and the active materials are easy to fall off from the metal collecting collector,so it is still a challeng to synthesize the composite materials that can synergistically improve the lithium storage performance of transition metal oxides by simple and efficient methods.As a new composite functional lamellar material,hydrotalcite compounds have made great progress.Hydrotalcite precursor composite materials(CoAl-LDHs)were synthesized using microwave-assisted synthesis method in this article,Co₃O₄/Al₂O₃,NiCo₂O₄/Co₃O₄/Al₂O₃//NF,NiCo₂O₄/Co₃O₄/Al₂O₃/N-C//NF were successfully synthesized by high temperature pyrolysis method.Three composite oxide materials can significantly improve the electrochemical performance of lithium ion battery anode.The contents of the paper are as follows:1.CoAl-LDHs precursor was synthesized rapidly by microwave-assisted method.The precursor was composed of ultrathin nanosheet by nano-flower spherical particle.After the pyrolysis,the porous nanoflower spherical Co₃O₄/Al₂O₃ composite material was obtained.Different from the ordinary hydrothermal synthesis method and crystallization isolation method,the crystallinity of the composite was high and the particle size distribution was uniform.Compared with the single component Co₃O₄ material,the cyclic stability and rate performance of the composite material were significantly improved.At the current density of 0.2 A g^-1,the composite electrode still shows good stability after100 cycles,while the single component electrode has a significant tendency of attenuation.This is due to the synergistic effect of the two components in the composite and the non-electrochemical activity of Al₂O₃,which buffers the volume expansion of Co₃O₄ in the charging and discharging process.2.CoAl-LDHs precursor on metal nickel substrate was synthesized in situ by microwave-assisted method.During the synthesis process,the huge energy generated by microwave and the strong acidity in the precursor solution caused part of the nickel substrate to dissolve,forming the ternary NiCoAl-LDHs composite.The composite material grew tightly in the inner and outer walls of the nickel wire,and the inner part is the morphology of nano-sheet array,and the outer part is the morphology of nano-sheet flower ball.NiCo₂O₄/Co₃O₄/Al₂O₃//NF porous nanocomposite electrode was obtained by the pyrolysis of NiCoAl-LDHs.The electrode can be used directly for lithium ion anode materials.The electrochemical performance test result shows that the electrode can maintain 1.77 m A h cm^-2 at the current density of 0.5 m A cm^-2.3.NiCoAl-LDHs//NF precursors were rapidly synthesized in situ on nickel substrate by microwave-assisted synthesis.And then the precursors were soaked in Coca-Cola and slowly stirred.Then the electrode was dried and annealed at low temperature to form NiCo₂O₄/Co₃O₄/Al₂O₃/N-C//NF composite electrode.The composite material has a long cycle life(>2500 times)and excellent rate performance.