Research On Anode Materials Of Lithium Ion Battery Based On The Hollow Carbon Spheres

The nanosized hollow carbon microspheres (HCM), manganite/HCM composite (Mn3O4/HCM and MnO/HCM), MnO/carbon composite with multi-modal pore structure using phenolic resin and dopamine as shell materials respectively were prepered by template method. The morphology, component, structure, crytal texture, porosity and inner structure of the materials were characterised by transmission electron microscope (TEM), scanning electron microscope (SEM), Fourier transform infrared spectroscopic (FT-IR), Raman, thermogravimetric analysis (TGA), X-ray diffraction spectrum analysis (XRD) and BET nitrogen adsorption-desorption test. Using the as prepared materials as anode for Li-ion batteries represently, the electrochemical performance of the as prepared five samples were contrasted and analyzed by using cyclic voltammetry test (CV), alternating current impedance test and galvanostatic charge-discharge test.The as prepared HCM with good regularity and integrity had a low degree of graphitization and a high specific surface area of 814.8 m2g-1.The HCM belongs to "hard carbon" with a far more higher capacity than the theoretical specific capacity of graphite. A reversible capacity of 511.5mAhg-1 was obtened after 1000 cycles at the current density of 1.0Ag-1, exhibiting a good rate performance and cycling stability. The as prepared MnOx/HCM composites were mixture of manganite crystal particles and HCM. Only a little smaller crystal particles may enter in the inner of HCM. The capacity of the MnOx/HCM composites was greatly improved compared to the corresponding blank HCM samples due to the redox reaction of manganite.The homogeneous composite microparticles (2?3?m) with nano-sized MnO crystal paticals embedding in the carbon matrix and multi-modal pore structure were obtained when adding manganese source before coating a shell material on the spheres. The MnO/C composite with a 8% carbon content and using PF as shell materials showed a certain superiority:the reversible capacity reached 1224.6 mAhg-1 after 700 cycles at 1.0Ag-1, the culombic efficiency was as high as above 80% for the first time, the rate performance was satisfactory (charged to 99.8% in 7.7min at 3.0 A g-1, obtained a capacity of 391.1 mAhg-1) and the structure kept consistent after charge-discharge for amounts of cycles. The mesoporous of carbon layers can provide a lot of active sites for lithium storage. The carbon layers both on the surface of the composite and between the MnO crystals and the multi-modal pore structure of the microparticles formed from the decomposition of PF and sPS nanospheres can buffer the severe volume change of electrode materials during the lithiation/delithiation process, thus kept the structure steady. The amorphization of MnO crystal, the decline of charge transfer resistance and the formation of higher oxidation state made the capacity raised up to a high lever subsequently.