Nanostructured Nb₂O₅ Polymorphs by Electrospinning for Rechargeable Lithium Batteries

Abstract

Polymorphs of 1D nanostructures of niobium pentoxide (Nb2O5) are synthesized by electrospinning. Pseudohexagonal (H−Nb2O5), orthorhombic (O−Nb2O5), and monoclinic (M−Nb2O5) structures of Nb2O5 are developed in this study by appropriate heat treatment. Morphological, structural, and electrochemical properties of these nanofibrous polymorphs are studied in detail. The H− and O− phases maintain the usual fibrous morphology, whereas the M− phase adopted a distorted nugget structure. These phases are evaluated for their application as cathode for lithium batteries. The M−Nb2O5 exhibits the highest capacity and better capacity retention compared to the other phases. The M−Nb2O5 delivers a specific capacity of 242(±3) and 218(±3) mAhg−1, cycled at a current of 50 mAg−1 in the voltage range, 1.0−2.6 V versus Li/Li+ at the end of second and 25th cycle, respectively. The electrospun M−Nb2O5 nuggets-based battery performs better than its particle/nanofiber counterpart and could be a cathode material of choice for 2 V due to the commercial viability of the electrospinning process and characteristics of the batteries developed herewith.

Studies on the lithium ion diffusion coefficients of electrospun Nb2O5 nanostructures using galvanostatic intermittent titration and electrochemical impedance spectroscopy

“…As-spun polymeric fibers had a diameter ~ 300 nm. Upon sintering up to ~450 °C, PVP evaporated and the fiber diameter reduced to ~160 nm [4]. The diameter remained constant at temperature up to 900 °C but the fiber surface changed from a smooth surface at 500 °C (Fig.1a.) to an uneven surface at 800 °C (Fig.1b.).…”

“…Kodama et al [3] found that O-Nb 2 O 5 particles possess superior cycling performance compared to M-Nb 2 O 5 particles. In our previous work, we made an opposite observation in the case of bare and Ta-doped Nb 2 O 5 nanofibers [4,5].…”

Electrochemical Energy Storage Applications of CVD Grown Niobium Oxide Thin Films

“…While the pseudohexagonal phase of Nb2O5 (TT-Nb2O5) is preferred in electrochromic applications, the tetragonal phase (MNb2O5) has shown the best performance when integrated in the electrode materials for lithium ion batteries. 38 Recently, the orthorhombic phase (T-Nb2O5) has been reported to exhibit the so called intercalation pseudocapacitance, in which the crystalline network of T-Nb2O5 offers transport pathways where the structural change upon intercalation is insignificant. 13 Ab initio molecular dynamics simulations were performed to compare the pseudocapacitor behavior in orthorhombic and monoclinic Nb2O5 (H-Nb2O5) phases.…”

High rate capability and cyclic stability of hierarchically porous Tin oxide (IV)–carbon nanofibers as anode in lithium ion batteries

“…In case of PVP and PAN, both can form H-bonding with metal oxide and form nanofibers morphology. However, (Viet et al 2009) show that heating temperature also have similar importance, despite of the polymer used. They have shown that Nb 2 O 5 nanofibers can retain their nanofiber morphology up to 800°C, but results in nugget like morphology when heating up to 1100°C due to melting of Nb 2 O 5 .…”

“…These nanofibers can be converted into carbon nanofibers or ceramic nanofibers depending upon polymer, additives and heat treatment conditions. Numerous binary and ternary oxide materials with fibrous (Cherian et al 2013a), nuggets (Viet et al 2009) and rice morphology (Shengyuan et al 2011;Zhu et al 2012) has been synthesized using combination of electrospinning and heat treatment and found application as lithium ion battery materials. Selection of polymer plays important role in deciding morphology of nanomaterial after electrospinning.…”