Effect of the Niobium Doping Concentration on the Charge Storage Mechanism of Mesoporous Anatase Beads as an Anode for High-Rate Li-Ion Batteries

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 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.

Niobium K-Edge X-ray Absorption Spectroscopy of Doped TiO2 Produced from Ilmenite Digested in Hydrochloric Acid

“…Production of Nb-doped TiO 2 has been proposed by sol–gel synthesis, for example, for anatase beads with 0.1–10 atom % Nb from starting material of titanium(IV) isopropoxide with 1-hexadecylamine as a structure-directing agent for use in Li-ion batteries. 20 A similar sol–gel synthesis of TiO 2 doped with about 10% Nb from titanium tetrabutyl titanate with 1-hexadecylamine and polydimethylsiloxane as structure determining agents was prepared for use in electrorheological fluids. 39 A sol–gel preparation followed by spark plasma sintering with repeated oxidation and reduction is another method proposed for the preparation of Nb-doped TiO 2 powders.…”

“… 12 Other catalytic applications are for catalyst supports, 13 for example, for the oxygen reduction reaction 14 and H 2 production, 15 or for dimensionally stable anodes for the chlorine evolution reaction, 16 and electrochemical destruction of “forever chemicals”. 17 Nb-doped TiO 2 has potential application in batteries and supercapacitors 18 including lithium-ion batteries 19 , 20 and Na-ion batteries. 21 Other potentials uses are for CO sensing 22 and thermoelectric power production.…”

Atomic‐Scale Design of Anode Materials for Alkali Metal (Li/Na/K)‐Ion Batteries: Progress and Perspectives

“…Similarly, sodiation can change the electronic properties from insulating to metallic. [273] DFT simulations showed that a Nb concentration of 0.1-1.0% increased the metallic character of TiO 2 due to the induced shift in Fermi level upon doping, whilst retaining the redox properties of the undoped anatase, [274] whereas the semiconducting Na 2 Ti 3 O 7 with bandgap 2.25 eV becomes metallic upon full sodiation. [273] The role of functionalization is not limited to voltage and surface adsorption though, and can be employed as a materials design tool to also modify mobility.…”

Unravelling nanostructured Nb-doped TiO2 dual band behaviour in smart windows by in situ spectroscopies

“…It is well known that the effects related to surface charge are more noticeable at high scan rate analysis. 25,49 A possibility is to attribute this overall charge capacitance effect to the surface effect associated with the presence of LSPRs in the doped NCs, something we will address later. Moreover, looking at the CVs in detail (inset graphs Fig.…”