Development of TiO2 rutile as negative electrode material for lithium ion batteries
FacultiesFakultät für Naturwissenschaften
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Lithium ion batteries are capable to meet the increasing demand of energy storage systems especially in the field of hybrid electric vehicles (HEVs), electric vehicles (EVs) and renewable energies. However a lot of research has to be done to improve the existing lithium ion batteries in terms of safety and power density. It was recently shown that nanostructured TiO2 in the rutile modification can reversibly insert lithium ions which makes it suitable for the use as electrode material for lithium ion batteries. The material is environmental friendly, exhibits an excellent thermal and chemical stability and many TiO2 precursors are commercially available. Pure rutile nanomaterials were synthesized via a standard TiCl4 precursor and a new route using glycerin and ethylene glycol modified TiO2 precursor. In this thesis, new insights into the lithium insertion / extraction mechanism were gained by TEM measurements of cycled electrodes. It could be proven that the rutile structure is retained after the electrochemical delithiation of the electrode. The structure-morphology-property relationships which were investigated on the crystallite level by TEM and on the particle level by SEM showed an improved capacity for smaller crystallite size and a better high rate capability for homogeneous particles. The electrochemical measurements of the rutile negative electrode exhibit an excellent high rate capability up to a charge / discharge rate of 30 C (2 min charge / discharge time), good low temperature behaviour and a good cycling stability for more than 1000 cycles. For the first time rutile electrodes were cycled in the potential window of 0.1-3 V reaching high capacities comparable to commercial graphite electrodes. Investigations of the electrode interfaces by XPS and impedance spectroscopy evidenced the formation of a SEI layer in the potential window of 0.1-3 V which is dynamic upon cycling.
Subject HeadingsLithiumbatterie [GND]
Lithium cells [LCSH]
Lithium ion batteries [LCSH]