Relationship between tin environment of SnO2 nanoparticles and their electrochemical behaviour in a lithium ion battery
Résumé
SnO2 nanoparticles were synthetized in three different ways (solvothermal, hydrothermal, sol-gel) and heat-treated under argon at 600 °C to obtain different physico-chemical characteristics (texture, structure and surface chemistry) determined by X-ray powder diffraction (XRD), infrared spectroscopy (FTIR), 119Sn solid state Nuclear Magnetic Resonance (NMR), Electron Spin Resonance (ESR), scanning electron microscopy (SEM) and 77 K nitrogen sorption. When used as electrode material in a lithium ion battery, their electrochemical properties were evaluated by galvanostatic measurements. Among crystallinity, particle size, specific surface area and associated porosity, hydroxyl groups and paramagnetic centers, only the last two parameters appear as determinants of electrochemical performance. Solvothermal and hydrothermal syntheses lead to the presence of certain hydroxyl groups in the oxide whereas sol-gel one prevents their formation but forms paramagnetic species. The hydroxyl groups favour a good coulombic efficiency and an interesting reversibility of the conversion process. Paramagnetic species limit the electrochemical process. Their elimination by a heat-treatment at 1000 °C under argon improves the electrochemical properties. Understanding the key factors to favour SnO2-based materials allows to obtain capacities of about 900 mAh.g−1 over 5 cycles.
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