Abstract
A promising strategy to improve the rate performance of Li-ion batteries is to enhance and facilitate the insertion of Li ions into nanostructured oxides like TiO2. In this work, we present a systematic study of pentavalent-doped anatase TiO2 materials for third-generation high-rate Li-ion batteries. Mesoporous niobium-doped anatase beads (Nb-doped TiO2) with different Nb5+ doping (n-type) concentrations (0.1, 1.0, and 10% at.) were synthesized via an improved template approach followed by hydrothermal treatment. The formation of intrinsic n-type defects and oxygen vacancies under RT conditions gives rise to a metallic-type conduction due to a shift of the Fermi energy level. The increase in the metallic character, confirmed by electrochemical impedance spectroscopy, enhances the performance of the anatase bead electrodes in terms of rate capability and provides higher capacities both at low and fast charging rates. The experimental data were supported by density functional theory (DFT) calculations showing how a different n-type doping can be correlated to the same electrochemical effect on the final device. The Nb-doped TiO2 electrode materials exhibit an improved cycling stability at all the doping concentrations by overcoming the capacity fade shown in the case of pure TiO2 beads. The 0.1% Nb-doped TiO2-based electrodes exhibit the highest reversible capacities of 180 mAh g–1 at 1C (330 mA g–1) after 500 cycles and 110 mAh g–1 at 10C (3300 mA g–1) after 1000 cycles. Our experimental and computational results highlight the possibility of using n-type doped TiO2 materials as anodes in high-rate Li-ion batteries.
Highlights
As the field of use of battery systems further expands, batteries with higher capacity, cyclability, and safety are deemed necessary
Considering the similarity in ionic radii and previous results reported in literature,[18] it is reasonable to assume that Nb5+occupies Ti4+ sites and that the lattice constants of a Nb-doped TiO2 crystal will be larger than those of the pure TiO2 crystal
The present work reports a detailed study on the effect of Nb5+ doping in anatase materials for high-rate Li-ion batteries
Summary
As the field of use of battery systems further expands, batteries with higher capacity, cyclability, and safety are deemed necessary. TiO2-based nanomaterials and, in particular, the polymorphs anatase and TiO2(B) are promising as negative electrodes due to their high structural stability, thanks to the low volume change during cycling (∼4%).[1] the poor electronic conductivity and the low ionic diffusivity, which influence the Li insertion/desertion in TiO2, are affecting their use in practice.[8]. Our results show that the synergistic effect of the mesoporous bead morphology and the Nb5+ doping (n-type) significantly improves the cycling life by reducing the capacity fading and increasing the specific nominal capacity both at low (1C) and at high (from 10C up to 100C) current rates, suggesting the use of these materials for both low and high rate capability fast rechargeable Li-ion batteries
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