Preparation And Electrochemical Properties Of Onion-Like Hollow Carbon Nanoparticle/SnO₂ Electrode Materials For Lithium-Ion Batteries

Recently, Lithium-ion batteries have been widely used in portable electronic devices such as cellular phones, camcorders, notebook computers due to their high energy density, high voltage and non-pollution. Meanwhile, they have great potential in electric vehicles and tools. The electrochemical properties of lithium ion batteries mainly depend on the structures and properties of electrode materials and electrolyte. Especially, the quality of electrode material directly decides the lithium ion battery characteristics and price. For the problems of larger capacity loss and lower reversible capacity of carbon materials using in lithium-ion batteries during charge and discharge process at high rate, this research firstly focused on the preparation of onion-like hollow carbon nanoparticles (OC) with average particle size of around 40nm. After further treatment, graphitized onion-like hollow carbon nanoparticles (GOC) and expanded graphitized onion-like hollow carbon nanoparticles (EGOC) were obtained. And then the novel tin oxides/carbon composites were prepared using the onion-like carbon materials as the matrix by impregnating and oxidation treatment of tin salt. The morphology and structure were systematically investigated by scanning electron microscope (SEM), transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and thermogravimetric-differential scanning calorimetry (TG-DSC) measurements. The electrochemical properties were investigated via galvanostatic charge and discharge, cyclic voltammetry (CV) and electrochemical impedance spectroscopy tests (EIS). The relationship between the synthesis condition, morphology and structure of composites and their electrochemical properties was revealed. It had great academic and practical significances for the broadening of new carbon materials and the promotion of negative materials with high capacity for lithium-ion batteries.The results showed that the type of matrix, synthesis method, synthesis condition and the content of tin oxide in composites had significant influence on the morphology, structure and electrochemical properties of composites. At optimized condition, OC and GOC with hollow sphere structure could deliver the reversible capacities of 446 and 495mAh/g, respectively, when they were used as the matrix of tin oxides and showed excellent cycle performance at the higher current density. Tin oxide/EGOC composite delivered the reversible capacity of 518 mAh/g and almost didn't show capacity loss over the same cycles. All above results indicated that OC, GOC and EGOC are the suitable matrix for tin and tin oxides because they not only could ensure the high electronic conductivity of composites, but also could efficiently buffer the specific volume change of tin during charge and discharge process.