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 TiO 2 . In this work, we present a systematic study of pentavalent-doped anatase TiO 2 materials for third-generation high-rate Li-ion batteries. Mesoporous niobium-doped anatase beads (Nb-doped TiO 2 ) with different Nb 5+ 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 TiO 2 electrode materials exhibit an improved cycling stability at all the doping concentrations by overcoming the capacity fade shown in the case of pure TiO 2 beads. The 0.1% Nb-doped TiO 2 -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 TiO 2 materials as anodes in high-rate Li-ion batteries.
The new iron layered oxysulfate SrFeO(SO) has been prepared by a solid-state reaction in closed ampules into the form of ceramics and single crystals. Its atomic structure has been solved by means of spectroscopy, diffraction techniques, and high-resolution electron microscopy. SrFeO(SO) is a layered structure that derives from the Ruddelsden-Popper (RP) phases with the layer stacking sequence SrO/SrFeO/SrFe(SO)O/SrFeO. Within the mixed Fe/SO layer, the sulfur atoms are slightly shifted from the B site of the perovskite and each sulfate group shares two corners with iron pyramids in the basal plan without any order phenomenon. The electronic conductivity is thermally activated, while no ionic conductivity is detected.
In this work, we establish an innovative protocol for the production of Pt–Rh solid solution/core–shell nanoparticles with excellent control of element distribution and composition, built upon the well-established heat-up method.
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