High grain boundary density Li4Ti5O12/anatase-TiO2 nanocomposites as anode material for Li-ion batteries

•Li4Ti5O12/TiO2 nanocomposites with high grain boundary density were synthesized.•7Li NMR and impedance spectroscopy shows high Li-ion mobility in nanocomposites.•The shape of charge/discharge curves changes for nanocomposites.•Influence of particle size on cycling performance of lithium titanates was shown.•Li4Ti5O12/TiO2 nanocomposite exhibits good cycling performance and rate capability.

Li4Ti5O12/TiO2 nanocomposites are synthesized by a sol-gel method. The size of Li4Ti5O12 and TiO2 particles is of 4–5 and 7–10 nm, respectively. The obtained materials are characterized by XRD, SEM, HRTEM and BET. Ion mobility of the composites and their performance as anode materials for lithium-ion batteries are studied. According to the conductivity and 7Li NMR data, Li+ mobility is much higher in the Li4Ti5O12/TiO2 nanocomposites as compared with that in pure Li4Ti5O12. For Li4Ti5O12/TiO2 nanocomposites, marked changes in the charge–discharge curves are observed; charge–discharge rate and effective capacity at a high cycling rate are shown to increase. During the first cycle, charge capacity of these materials surpasses the theoretical capacity of Li4Ti5O12. However, this parameter decreases sharply with cycling, whereas the discharge capacity remains almost unchanged. This phenomenon is attributed to the solid electrolyte interphase formation due to a partial electrolyte reduction on the Li4Ti5O12/TiO2 composite surface.

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