Abstract
Nickel- and zinc-doped TiO2(B) nanobelts were synthesized using a hydrothermal technique. It was found that the incorporation of 5 at.% Ni into bronze TiO2 expanded the unit cell by 4%. Furthermore, Ni dopant induced the 3d energy levels within TiO2(B) band structure and oxygen defects, narrowing the band gap from 3.28 eV (undoped) to 2.70 eV. Oppositely, Zn entered restrictedly into TiO2(B), but nonetheless, improves its electronic properties (Eg is narrowed to 3.21 eV). The conductivity of nickel- (2.24 × 10−8 S·cm−1) and zinc-containing (3.29 × 10−9 S·cm−1) TiO2(B) exceeds that of unmodified TiO2(B) (1.05 × 10−10 S·cm−1). When tested for electrochemical storage, nickel-doped mesoporous TiO2(B) nanobelts exhibited improved electrochemical performance. For lithium batteries, a reversible capacity of 173 mAh·g−1 was reached after 100 cycles at the current load of 50 mA·g−1, whereas, for unmodified and Zn-doped samples, around 140 and 151 mAh·g−1 was obtained. Moreover, Ni doping enhanced the rate capability of TiO2(B) nanobelts (104 mAh·g−1 at a current density of 1.8 A·g−1). In terms of sodium storage, nickel-doped TiO2(B) nanobelts exhibited improved cycling with a stabilized reversible capacity of 97 mAh·g−1 over 50 cycles at the current load of 35 mA·g−1.
Highlights
Up until recently, electrochemical energy storage devices, among which lithium-ion batteries (LIBs) are dominant, were mainly used for areas that demanded moderate characteristics and soft operating standards
Due to the fundamental physicochemical properties of carbonaceous anode-active material, LIBs suffers restricted performance for such aims, especially in terms of charging rate, operating temperature range, and safety [1,2,3]
Their analysis revealed that monoclinic bronze of TiO2 (PDF #46-1238, space group C2/m) was a dominant phase and tetragonal anatase (PDF #21-1272, space group I41/amd) was an impurity for all samples confirming the correct synthesis [37]
Summary
Electrochemical energy storage devices, among which lithium-ion batteries (LIBs) are dominant, were mainly used for areas that demanded moderate characteristics and soft operating standards (e.g., portable electronics, medical equipment, and power tools). Due to the fundamental physicochemical properties of carbonaceous anode-active material (the voltage of Li+ insertion is close to that of Li metal formation, thereby causing its dendritic deposition; this is critical for charge in high-rate or low-temperature conditions), LIBs suffers restricted performance for such aims, especially in terms of charging rate, operating temperature range, and safety [1,2,3] To avoid these problems, a negative electrode based on lithium pentatitanate with an operating potential of 1.55 V vs Li/Li+ [4] was recently proposed and successfully commercialized (for example, in Mitsubishi i-MiEV and Honda Fit EV electric cars).
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