Preparation Of TiO₂,NiCoO₂ And Mn₃O₄ Based Nanocomposites Materials And Research On Battery Performance Of Lithium And Zinc Storage

Ti,Ni,Co,Mn-based oxides have always been the focus of attention on electrode materials for lithium-ion batteries and aqueous zinc-ion batteries.TiO₂ has a low theoretical specific capacity and poor electrical conductivity.The significant volume changes of Ni and Co oxides during charge and discharge make its energy storage performance poor.Mn-based compounds are used as cathode materials for aqueous zinc-ion batteries with low electrical conductivity and great volume change,resulting in poor actual capacity and cycle stability.In this paper,TiO₂,NiCoO₂,Mn₃O₄ are used as the research objects,using hydrothermal reaction,chemical bath deposition,template method and et al to synthesize unique pomegranate-like C@TiO₂ mesoporous honeycomb spheres,double-shelled carbon@NiCoO₂-Co OOH hollow burr nanospheres and honeycomb C@Mn₃O₄,through nanostructure design and carbon composite strategy to improve the material's lithium or zinc ion storage performance.The main research content of this paper can be shown as follow:(1)Through hydrolysis and polymerization of isopropyl titanate and hexadecylamine,hydrothermal reaction to remove hexadecylamine,chemical polymerization to coat polypyrrole and carbonization,a unique pomegranate-like C@TiO₂ mesoporous honeycomb sphere have been synthesized.TiO₂ mesoporous honeycomb spheres are assembled from TiO₂ nanocrystalline grains with a size of about10 nm.They have abundant mesopores,a specific surface area of 153 m² g^-1,and a 30-40nm thickness of amorphous carbon tightly covering the TiO₂ mesoporous honeycomb spheres.The material is made into a button-type lithium-ion battery.The electrochemical test shows excellent specific capacity,cycle stability and rate performance.The current density is 1 C for 500 cycles,the discharge capacity reaches 184 m Ah g^-1.The excellent lithium battery performance is due to the mesoporous honeycomb structure which makes TiO₂ have excellent electrochemical and dynamic properties,and the coated carbon layer also improves the conductivity and stability of the TiO₂ mesoporous honeycomb sphere.(2)C@NiCoO₂-Co OOH hollow burr nanospheres were prepared by growing Ni-Co precursor on the surface of synthesized SiO₂ template microspheres,polymerizing and coating polypyrrole on the surface of Ni-Co precursor,removing SiO₂ after carbonization.The height and diameter of the NiCoO₂-Co OOH burrs are approximately 120 nm and 5nm,the diameter of the hollow sphere is 400 nm,and the thickness of the carbon layer after carbonization of polypyrrole is 20 nm,which partially fills the gaps between the NiCoO₂ burrs and provides a strong structural support.As anode material for lithium-ion batteries,C@NiCoO₂-Co OOH hollow burr nanospheres have high reversible capacity,stable cycle performance and good rate capability.At a current density of 200 m A g^-1,the discharge capacity is still as high as 912 m Ah g^-1 after 600 cycles.Excellent lithium storage performance is due to the double-shell hollow nanosphere structure.The burrs make NiCoO₂ and Co OOH have high electrochemical activity.The hollow nanosphere structure enhances the adaptive capacity of NiCoO₂ and Co OOH for volume changes.Amorphous carbon coating layer improves the structural stability and electrical conductivity of NiCoO₂ and Co OOH.The synergistic effect of these factors makes NiCoO₂ and Co OOH ultimately have excellent lithium storage performance.(3)Using SiO₂ microspheres with a diameter of 350 nm as the pore-forming template and polyvinylpyrrolidone as the carbon source,the honeycomb porous carbon is prepared by solution drying,carbonization and lye desiliconization,and then a flake-like shape is grown on the surface of the honeycomb carbon through a chemical reaction Mn O₂,the honeycomb C@Mn₃O₄ nanocrystalline composite material is obtained after calcination.The carbon substrate has rich and dense macropores,with a typical honeycomb structure,with a specific surface area of 88.778 m² g^-1,and the Mn₃O₄ nanocrystalline size is 7-11nm,uniformly coupled in the honeycomb pores.As a cathode material for aqueous zinc-ion batteries,honeycomb C@Mn₃O₄ nanocrystals have excellent zinc-ion storage performance,including high specific capacity,cycle stability and excellent rate performance.The discharge capacity release 120 m Ah g^-1 at a current density of 3 A g^-1after 748 cycles,high reversible capacity under various current densities.The excellent zinc-ion battery performance is due to its unique structural design.The nanocrystalline size shortens the diffusion path of zinc ions in Mn₃O₄ and improves the reaction kinetics.The honeycomb porous structure facilitates the penetration of the electrolyte and is conducive to the full contact between the Mn₃O₄ nanocrystals and the electrolyte.The carbon substrate improves the conductivity of Mn₃O₄.The combined effect of these factors improves the performance of the Mn₃O₄ zinc battery.