Novel Nonstoichiometric Niobium Oxide Anode Material with Rich Oxygen Vacancies for Advanced Lithium-Ion Capacitors

Abstract

Given the inherent features of open tunnel-like structures, moderate lithiation potential (1.0–3.0 V vs Li/Li+), and reversible redox couples (Nb5+/Nb4+ and Nb4+/Nb3+ redox couples), niobium-based oxides with Wadsley–Roth crystallographic shear structure are promising anode materials. However, their practical rate capability and cycling stability are still hindered by low intrinsic electronic conductivity and structural stability. Herein, ultrathin carbon-confined Nb12O29 materials with rich oxygen vacancies (Nb12O29–x @C) were designed and synthesized to address above-mentioned challenges. Computational simulations combined with experiments reveal that the oxygen vacancies can regulate the electronic structure to increase intrinsic electronic conductivity and reduce the Li+ diffusion barrier. Meanwhile, the carbon coating can enhance structural stability and further improve the electronic conductivity of the Nb12O29 material. As a result, the as-prepared Nb12O29–x @C exhibits high reversible capacity (226 mAh g–1 at 0.1 A g–1), excellent high-rate performance (83 mAh g–1 at 5.0 A g–1), and durable cycling life (98.1% capacity retention at 1.0 A g–1 after 3000 cycles). The lithium storage mechanism and structural stability of Nb12O29–x @C were also revealed by in situ X-ray diffraction (XRD), ex situ X-ray photoelectron spectroscopy (XPS), and ex situ Raman spectroscopy. When applied as the anode of lithium-ion capacitors (LICs), the as-built LIC achieves high energy density (72.4 Wh kg–1) within the voltage window of 0.01–3.5 V, demonstrating the practical application potential of the Nb12O29–x @C materials.

Enhanced Energy Storage Performance of Zr-Doped TiNb2O7 Nanospheres Prepared by the Hydrolytic Method

“…To investigate the influence of Zr doping on the electronic conductivity, four-point probe resistivity measurement was employed to measure and compare the electronic conductivity of Zr-doped TNO and pure TNO . We prepared a slurry containing active material (70 wt %), Super P (20 wt %), and poly(vinylidene difluoride) (10 wt %) and then coated it on insulating plastic sheets in order to obtain an electrode film with a thickness of 0.4 mm.…”

Morphology Variations in Copper Sulfide Nanostructures as Anode Materials for Na-Ion Capacitors

“…The dependence of the gravimetric capacitance on the current density can be seen in Figure c. The energy density ( E ) and power density ( P ) of the symmetric configuration was obtained using GCD profiles by the utilization of eqs and : E = 1 7.2 ( C V 2 ) P = E false( true t 3600 false) where C , V ,and t denote the gravimetric capacitance in F g –1 , potential in voltage, and discharge time (s), respectively. The symmetric configuration shows an energy density of 28 Wh k g –1 at a power density of 1600 W k g –1 , down to 7 Wh k g –1 at 8400 W k g –1 (Figure d).…”

An in situ dual-modification strategy for O3-NaNi1/3Fe1/3Mn1/3O2 towards high-performance sodium-ion batteries

“…[1][2][3][4][5] In contrast to P2-type cathodes, the advantage of O3-type cathodes is that they deliver higher reversible capacity due to accommodating considerably more of Na + into the interlayer. [6][7][8] Meanwhile, the full content of Na + in the layer structure would have no limitation for the practical capacity when constructing a full cell with sodium-free anodes. [9][10][11] Among the numerous reported O3-layered structures of ternary transition metal mixtures, O3-NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NFM), rst reported by Johnson et al, is one of the promising Na-storage cathode candidates with an appreciable capacity of >130 mA h g −1 (0.1C) and relatively simple phase transformation (O3-P3-P3-O3) in the voltage range of 2.0-4.0 V. 12,13 Besides, the usage of cost-effective transition metals Fe and Mn further enhances the value for commercialization.…”

“…1–5 In contrast to P2-type cathodes, the advantage of O3-type cathodes is that they deliver higher reversible capacity due to accommodating considerably more of Na + into the interlayer. 6–8 Meanwhile, the full content of Na + in the layer structure would have no limitation for the practical capacity when constructing a full cell with sodium-free anodes. 9–11…”