Data from: Effect of Hf-doping on electrochemical performance of anatase TiO2 as an anode material for lithium storage

Hafnium-doped titania (Hf/Ti = 0.01; 0.03; 0.05) had been facilely synthesized via a template sol-gel method on carbon fiber. Physicochemical properties of the as-synthesized materials were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, scanning transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry analysis, and Brunauer−Emmett−Teller measurements. It was confirmed that Hf4+ substitute in the Ti4+ sites, forming Ti1–xHfxO2 (x = 0.01; 0.03; 0.05) solid solutions with an anatase crystal structure. The Ti1–xHfxO2 materials are hollow microtubes (length of 10–100 μm, outer diameter of 1–5 μm) composed of nanoparticles (average size of 15–20 nm) with surface area of 80–90 m2 g–1 and pore volume of 0.294–0.372 cm3 g–1. The effect of hafnium ions incorporation on electrochemical behavior of anatase TiO2 as Li-ion battery anode was investigated by galvanostatic charge/discharge and electrochemical impedance spectroscopy. It was established that Ti0.95Hf0.05O2 shows significantly higher reversibility (154.2 mAh g–1) after 35-fold cycling at C/10 rate in comparison with undoped titania (55.9 mAh g–1). The better performance offered by Hf4+ substitution of the Ti4+ into anatase TiO2 mainly results from more open crystal structure, which has been achieved via the difference in ionic radius values of Ti4+ (0.604 Å) and Hf4+ (0.71 Å). The obtained results are in a strong accordance with ones for anatase TiO2 doped via Zr4+ (0.72 Å) published earlier. Furthermore, improved electrical conductivity of Hf-doped anatase TiO2 materials due to charge redistribution in the lattice and enhanced interfacial lithium storage due to increased surface area directly depending on Hf/Ti atomic ratio have beneficial effect on electrochemical properties.以碳纤维为基底，通过模板溶胶-凝胶法简便合成了铪掺杂二氧化钛（Hf/Ti原子比分别为0.01、0.03、0.05）。采用X射线衍射（X-ray diffraction）、拉曼光谱（Raman spectroscopy）、扫描电子显微镜（scanning electron microscopy）、能量色散X射线能谱（energy-dispersive X-ray analysis）、扫描透射电子显微镜（scanning transmission electron microscopy）、X射线光电子能谱（X-ray photoelectron spectroscopy）、热重分析（thermogravimetry analysis）以及布鲁瑙尔-埃米特-特勒（Brunauer−Emmett−Teller, BET）比表面积测试对所合成材料的物理化学性质进行了表征。经证实，四价铪离子（Hf⁴+）取代了四价钛离子（Ti⁴+）的晶格位点，形成具有锐钛矿晶体结构的Ti₁₋ₓHfₓO₂（x=0.01、0.03、0.05）固溶体。该系列Ti₁₋ₓHfₓO₂材料为由平均粒径15~20 nm的纳米颗粒组装而成的中空微管，其长度为10~100 μm，外径1~5 μm，比表面积为80~90 m²·g⁻¹，孔容为0.294~0.372 cm³·g⁻¹。研究采用恒流充放电测试与电化学阻抗谱（electrochemical impedance spectroscopy），探究了铪离子掺杂对作为锂离子电池负极的锐钛矿型二氧化钛电化学行为的影响。结果表明，在C/10倍率下循环35次后，Ti₀.₉₅Hf₀.₀₅O₂的可逆比容量（154.2 mAh·g⁻¹）显著高于未掺杂二氧化钛（55.9 mAh·g⁻¹）。四价铪离子取代锐钛矿型二氧化钛中的四价钛离子所带来的优异性能，主要源于更开放的晶体结构——这一结构变化源于Ti⁴+（离子半径0.604 Å）与Hf⁴+（离子半径0.71 Å）之间的离子半径差异。本研究所得结果与此前已发表的四价锆离子（Zr⁴+，离子半径0.72 Å）掺杂锐钛矿型二氧化钛的相关研究结果高度一致。此外，因晶格内电荷重新分布而提升的铪掺杂锐钛矿型二氧化钛材料的电导率，以及随Hf/Ti原子比提升而增大的比表面积所带来的界面储锂能力增强，均对其电化学性能产生了积极影响。