Electrophoretic Deposition of Mesoporous Niobium(V)Oxide Nanoscopic Films

Abstract

Nb 2 O 5 is a Li + intercalation metal oxide that is of current interest for lithium ion battery electrodes. The electrophoretic deposition (ED) of Nb 2 O 5 thin-films from aqueous, NbO x colloidal solutions is reported here. For films ranging in thickness from 38 to 144 nm, the mass loading of Nb 2 O 5 on the electrode is correlated with the coulometry of ED using quartz crystal microbalance gravimetry. Crystalline, phase pure films of orthorhombic, T-Nb 2 O 5 , are obtained by postdeposition calcination. These films exhibit unusually high specific capacities for Li +-based energy storage as a consequence of ≈70% porosity. For example, a 60 nm thick film displays a specific capacity, C sp , of 420 mAh/g at 5 A/g and 220 mAh/g at 50 A/g, which can be compared with the theoretical Faradaic capacity of 202 mAh/g. T-Nb 2 O 5 films also have a specific energy density in the range from 770−486 Wh/kg, and a specific power density in the range from 9 to 90 kW/kg. These excellent energy storage metrics are attributed to augmentation of the Faradaic capacity by high double-layer capacities enabled by the mesoporous structure of these films. 37 of a few k B T, for Li + transport in this material, as measured 38 using nuclear magnetic resonance. 39 T-Nb 2 O 5 is most often synthesized by hydrothermal 40 methods, 1,2,4,13,14 and highly dispersed T-Nb 2 O 5 on carbon 41 has demonstrated specific capacities of up to 590 F/g. 14 Other 42 methods for preparing Nb 2 O 5 films include electrospinning 43 followed by thermal annealing, 16 spray pyrolysis, 17 sol−gel 44 processing methods, 9,10,18 electrospinning, 19 and reactive 45 sputtering. 11 46 Electrodeposition has hardly been attempted, in spite of the 47 fact that it is an attractive method for both electrochromics and 48 battery/capacitor materials because it promotes an electrically 49 intimate contact with an electrode that can also serve as a 50 current collector. The reason is that electrodeposition of 51 Nb 2 O 5 is difficult: the cathodic electrodeposition of niobium 52 oxides (NbO x) is complicated by the very negative reduction 53 potential for Nb 3+ (−1.1 V vs NHE) which makes disruptive

Tunable Intracrystal Cavity in Tungsten Bronze‐Like Bimetallic Oxides for Electrochromic Energy Storage

“…The high-resolution XPS spectra of W 4f and Nb 3d support the expected high-oxidation valence states of W 6+ and Nb 5+ , respectively. [25] These results match well with previous literature for Nb 18 W 16 O 93 , [20,21] indicating that the Nb 18 W 16 O 93 nanomaterial was successfully fabricated by this sol-hydrothermal method at a lower temperature than the solid-state synthesis. The Raman spectra of WO 3 , Nb 2 O 5 , and Nb 18 W 16 O 93 nanomaterials were further characterized as shown in Figure S2 (Supporting Information).…”

Investigating the Degradation of Nb2O5 Thin Films Across 10,000 Lithiation/Delithiation Cycles

“…First, all binders and fillers are eliminated, ensuring that degradation pathways involving these extrinsic materials are removed. Second, electrophoretic deposition (EPD) 19 is used for synthesizing thin films of T-Nb 2 O 5 films. We have recently reported 19 that EPD provides an unusually reproducible method for synthesizing thin films of T-Nb 2 O 5 .…”

“…Second, electrophoretic deposition (EPD) 19 is used for synthesizing thin films of T-Nb 2 O 5 films. We have recently reported 19 that EPD provides an unusually reproducible method for synthesizing thin films of T-Nb 2 O 5 . The use of many quasi-identical T-Nb 2 O 5 films provides a means for studying the evolution of the structure and composition during the degradation process using tools including cyclic voltammetry, high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energydispersive X-ray (fluorescence elemental) spectroscopy (EDS), electrochemical impedance spectroscopy (EIS), Raman microprobe spectroscopy, and X-ray photoelectron spectroscopy (XPS).…”

Mesoporous WO3 Nanofibers With Crystalline Framework for High-Performance Acetone Sensing

“…Therefore, MSMOs are regarded as promising candidates for gas sensing. To date, various MSMOs have been synthesized through different approaches, such as sol–gel processes, spray pyrolysis, chemical vapor deposition and precipitation reactions (Du et al, 2011; Luo et al, 2016a; Zhao et al, 2016; Channei et al, 2018; Jha G. et al, 2018; Zhang Y. et al, 2018). However, these methods usually give rise to an uncontrolled morphology and low porosity, which is not favorable for sensing performance.…”

“…However, these methods usually give rise to an uncontrolled morphology and low porosity, which is not favorable for sensing performance. Additionally, a lot of work has been focused on the design and construction of various nanostructures of SMOs to improve the their sensing performance, including zero-dimensional nanoparticles (NPs) (Yang Z. et al, 2018; Zhang H. et al, 2018; Zhao et al, 2019), one-dimensional nanofibers (NFs) (Saha and De, 2013; Kim et al, 2016a; Ren et al, 2016; Nada et al, 2017; He et al, 2018; Jeong et al, 2018) and nanowires (NWs) (Wang et al, 2004; Rakhi et al, 2012; Dam and Lee, 2013; Chen et al, 2015; Li X. et al, 2017), two-dimensional nanosheets (Wang et al, 2016, 2017; Li F. et al, 2017; Kaneti et al, 2018) and membranes (Dasog et al, 2012; Barr et al, 2017; Jha G. et al, 2018; Wang W. Q. et al, 2018). Nanofibers have drawn particular attention due to their exceptionally high surface area-to-volume ratio, high porosity, superior surface permeability and accessibility, making them an attractive candidate for gas sensing (Guo et al, 2014; Jha R. K. et al, 2018; Yan et al, 2018).…”