High Performance TiO₂ And Co₃O₄ Based Anode Material For Lithium-ion Batteries

The main topic of the research work is to improve the electrochemical properties of metal oxides such as poor conductivity,slow reaction power,low specific discharge capacity and poor cycle stability.Representative TiO₂ and Co₃O₄ are selected as research objects.The nanometer,coated,highly conductive material composited and the microstructure of the hollow mesopores are used to improve the cycle stability and rate performance of the material.The research content and main work of this paper are as follows:?1?3D mesopore N-doped carbon assembling P25 is composited by a controllable,low-cost and large-scale synthesis protocol.The process uses common P25 as the raw material,PVP as the dispersing agent and the binder as well as carbon precursor,the boiling bubbles as template,solidifying the boiling foam effectively by PVP-coating-and-connecting TiO₂ nanoparticles.The carbonization transforms PVP-assembling to carbon-assembling,and the obtained carbon is doped by a little N,which endows the carbon with higher conductivity.It is found by XRD,SEM,TEM and BET that the synthesized foam-like P25 possesses abundant mesopores,individual nanoparticles-assembled structure and high conductive N-doped carbon matrix;shows large specific surface area.As anode material for lithium-ion batteries?LIBs?,foam-like P25 exhibits remarkable lithium storage properties with high discharge capacity,stable cycling performance and excellent rate performance.Comparing the charge-discharge curve and the CV curve,the foam-P25 has a greater ability to store lithium than the pure P25,mainly because the special design of the structure allows a larger effective surface area to be exposed,improving the capacity of lithium tantalum capacitor storage.This is the main source of discharge capacity for foam-P25.At 1C,foam-like P25 still delivers the discharge capacity of 223.1 mAh/g at the 200th cycle,and the average discharge capacity over 200 cycles reaches 227 mAh/g.These excellent electrochemical properties should be attributed to the unique foam-like structure that greatly improves the lithium storage properties of common P25.The synthetic method has great potential for large scale production of foam-like P25 for practical application in high-performance LIBs.?2?Nitrogen-doped amorphous mesoporous hollow carbon nanospheres?HCN?are prepared through the unique polymerization reaction between 3-aminophenol and formaldehyde,the selective removal effect of acetone as well as a simple carbonization process.Ultrafine TiO₂nanocrystalline with average size of 7.4 nm are further uniformly,sparsely,tightly anchored onto HCNs through hydrolysis deposition of titanium tetraisopropanolate and a controllable crystallization.Material characterization By means of SEM,TEM,XRD and EDS,the analytical data prove the purity of the material,the synthesis of hollow carbon spheres,the size of ultrafine TiO₂ nanocrystals and the close combination of nanocrystals and carbon spheres.As anode material for lithium ion batteries,TiO₂@HCN exhibit high charge-discharge capacity,stable cycling performance and excellent rate capability.The average discharge capacity over 200 cycles at 1C is242 mAh/g,2C and 5C are 188 and 170 mAh/g.After rate test and subsequent 1500 continuous cycles at 10C,TiO₂@HCN still deliver discharge capacity of 146.1 mAh/g with a high capacity retention of 80.6%and a very low capacity decay of 0.012%per cycle.The superior lithium storage properties should be attributed to synthetic effects of ultrafine TiO₂ nanocrystalline and hollow carbon nanospheres.HCN can act as a micro-collector and evenly distribute the current to a large number of TiO₂ nanocrystals attached to it,thereby reducing polarization and improving high-speed charge and discharge capability;ultrafine TiO₂ nanocrystals significantly shorten the Li⁺diffusion length.Significantly improved Li⁺diffusion ability.All surfaces of TiO₂ nanocrystals are effective exposed surfaces,providing a large number of electrochemically active sites.This work could give rise to the new understanding about design and synthesis of next-generation,high-power TiO₂-based advanced anode for lithium ion batteries.?3?Co₃O₄ nanocrystalline-assembled mesoporous hollow polyhedron nanocage-in-nanocage are synthesized through a metal-organic-framework-engaged strategy that relies on the unique chemical reactivity of zeolitic imidazolate framework-67.As anode materials for lithium ion batteries,Co₃O₄ nanocage-in-nanocage shows high specific capacity?1271 mAh/g at 0.1C at the2nd cycle?and good cycling stability?the capacity retention of 81.6%after 100 cycles?,which could be attributed to beneficial effects of TiO₂ nanocrystalline and the mesoporous hollow nanocage-in-nanocage structure.