In Situ Orthorhombic to Amorphous Phase Transition of Nb₂O₅ and Its Temperature Effect on Pseudocapacitive Behavior

Abstract

Niobium pentoxide (Nb2O5) represents an exquisite class of negative electrode materials with unique pseudocapacitive kinetics that engender superior power and energy densities for advanced electrical energy storage devices. Practical energy devices are expected to maintain stable performance under real-world conditions such as temperature fluctuations. However, the intercalation pseudocapacitive behavior of Nb2O5 at elevated temperatures remains unexplored because of the scarcity of suitable electrolytes. Thus, in this study, we investigate the effect of temperature on the pseudocapacitive behavior of submicron-sized Nb2O5 in a wide potential window of 0.01–2.3 V. Furthermore, ex situ X-ray diffraction and X-ray photoelectron spectroscopy reveal the amorphization of Nb2O5 accompanied by the formation of NbO via a conversion reaction during the initial cycle. Subsequent cycles yield enhanced performance attributed to a series of reversible NbV, IV/NbIII redox reactions in the amorphous Li x Nb2O5 phase. Through cyclic voltammetry and symmetric cell electrochemical impedance spectroscopy, temperature elevation is noted to increase the pseudocapacitive contribution of the Nb2O5 electrode, resulting in a high rate capability of 131 mAh g–1 at 20,000 mA g–1 at 90 °C. The electrode further exhibits long-term cycling over 2000 cycles and high Coulombic efficiency ascribed to the formation of a robust, [FSA]−-originated solid-electrolyte interphase during cycling.

In Situ Raman Spectroscopy of Li+ and Na+ Storage in Anodic TiO2 Nanotubes: Implications for Battery Design

“…The asymmetric distribution of gust ions imparts a higher strain in the host lattice, which eventually disrupts the long-range order and makes the lattice amorphous. Such a crystalline-to-amorphous transition of the storage hosts under electrochemical ion insertion is already reported for capacitive-type Li-ion storage . The increasingly higher sloping of the discharge profile and quasi-rectangular nature of the differential capacity plots of the TiNP electrodes toward lower voltages signify a substantial capacitive contribution to the total storage capacity.…”

“…Such a crystalline-to-amorphous transition of the storage hosts under electrochemical ion insertion is already reported for capacitivetype Li-ion storage. 42 The increasingly higher sloping of the discharge profile and quasi-rectangular nature of the differential capacity plots of the TiNP electrodes toward lower voltages signify a substantial capacitive contribution to the total storage capacity. Hence, the lattice evolution of the TiNP electrodes under electrochemical Li-ion insertion shall be summarized as in given Figure 5.…”

Inducing a Conductive Surface Layer on Nb2O5 via Argon-Ion Bombardment: Enhanced Electrochemical Performance for Li-Ion Batteries

“…The electrochemical performance of the pristine Nb 2 O 5 and Nb 2 O 5 -AIB electrodes was investigated using Li/Nb 2 O 5 cells with 1 mol dm –3 LiPF 6 -EC/DMC electrolyte at 25 °C. In the 1.0–2.3 V voltage range, lithium insertion occurs into Nb 2 O 5 , which was proven by the reversible XRD diffraction peaks during (de)­lithiation. , Figure a shows that Nb 2 O 5 -AIB30 attained a considerably higher capacity of 211 mAh g –1 than the pristine Nb 2 O 5 (138 mAh g –1 ) at a current density of 40 mA g –1 , which reaches the theoretical capacity of Nb V/IV reaction (211 mAh g –1 ). For insight into the rate capabilities, current density was varied between 200 and 40,000 mA g –1 during discharge and fixed at 200 mA g –1 during charge (Figure b, Figure S2, and Table S2).…”

“…The surging demand for advanced electrochemical storage devices has shifted development focus into high-energy and high-power-density electrode materials in efforts to meet modern energy needs. − Among secondary batteries, niobium pentoxide (Nb 2 O 5 ), specifically its orthorhombic polymorph, has gained attention as a high-performance negative electrode material with a high theoretical capacity of 201.7 mAh g –1 based on Nb 5+ /Nb 4+ , exhibiting superior electrochemical performances emanating from pseudocapacitive Li + insertion mechanism(s). ,− Even so, the stoichiometric Nb 2 O 5 is an insulator with a wide band gap (between 3.2 and 4.0 eV) that engenders poor electronic conductivity (σ ∼3 × 10 –6 S cm –1 at 300 K); therefore improving the poor electronic conductivity is key to achieving a high rate performance of Nb 2 O 5 that eventually facilitates the realization of fast rechargeable energy devices. − To overcome the drawback, considerable efforts have been devoted to investigating fabrication techniques such as building special morphology, introducing conductive carbon networks, doping foreign elements for adequate utilization, and nanoarchitecture current collector. − Although materials with the utilization of these methods show certain enhancements, the compatibility with the ongoing manufacturing line remains challenging to meet the requirement of practical utilization of the mentioned methods. A simple experimental design is still highly desirable to circumvent the multistep or complicated synthesis routes.…”

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

“…Owing to the excellent stability and high energy density, rechargeable lithium-ion batteries (LIBs) have captured the extensive attention of researchers in the last few years. , As one of the components, anode materials has gone through several generations of updates. Among these, insertion-type anode materials show excellent rate capability − because their framework could provide available sites for Li-ions to be inserted and extracted while preserving the structure of the host lattice …”