T‐Nb₂O₅/C Nanofibers Prepared through Electrospinning with Prolonged Cycle Durability for High‐Rate Sodium–Ion Batteries Induced by Pseudocapacitance

Abstract

Homogeneous ultrasmall T-Nb O nanocrystallites encapsulated in 1D carbon nanofibers (T-Nb O /CNFs) are prepared through electrospinning followed by subsequent pyrolysis treatment. In a Na half-cell configuration, the obtained T-Nb O /CNFs with the merits of unique microstructures and inherent pseudocapacitance, deliver a stable capacity of 150 mAh g at 1 A g over 5000 cycles. Even at an ultrahigh charge-discharge rate of 8 A g , a high reversible capacity of 97 mAh g is still achieved. By means of kinetic analysis, it is demonstrated that the larger ratio of surface Faradaic reactions of Nb O at high rates is the major factor to achieve excellent rate performance. The prolonged cycle durability and excellent rate performance endows T-Nb O /CNFs with potentials as anode materials for sodium-ion batteries.

Exploiting the Condensation Reactions of Acetophenone to Engineer Carbon‐Encapsulated Nb2O5 Nanocrystals for High‐Performance Li and Na Energy Storage Systems

“…[24] Kim et al [66] have reported that the charge storage in the Na-ion electrolyte involves Na-ion intercalation/deintercalation reactions together with surface capacitive reactions. [42][43][44][65][66][67][68] For the Na-ion system, the NS morphology does not have a detrimental effect on the performance, as opposed to lithium, which is due to the differences in the charge storage processes occurring in these electrolytes. [24] In addition, it has been reported that Nb 2 O 5 undergoes amorphization during the first cycle due to conversion reactions associated with sodium insertion/deinsertion.…”

“…[7,34,35] The oxide nanostructures can also be coated with amorphous carbon via postsynthesis procedures, although it is difficult to obtain homogeneous coatings of the surface as particles tend to agglomerate. [42][43][44] However, the larger size of the sodium ion compared to lithium causes slow diffusion of the Na ions inside the structure of Nb 2 O 5 , which results in low capacities and fast capacity loss with the increase of the current density. However, methods that allow us to simultaneously control the Nb 2 O 5 size, composite morphology, porosity, and carbon content through simple experimental steps are still needed to produce high-performance electrode materials.…”

“…[36,37] Nb 2 O 5 /C composites have also been synthesized through thermal treatment of the oxide nanoparticles containing surfactant molecules attached to the surface. [43] Therefore, enhancing the Na-ion rate performance of Nb 2 O 5 -based electrodes remains a demanding task. Nb 2 O 5 has been mostly investigated as an anode electrode material for lithium-ion batteries and hybrid supercapacitors.…”

Niobium‐Based Oxides Toward Advanced Electrochemical Energy Storage: Recent Advances and Challenges

“…As for the application in SIBs, the electrode displays high reversible capacities of 230 and 100 mA h g −1 at 0.25 and 20C rate, respectively. In addition, electrospinning derived T‐Nb 2 O 5 /C nanofibers can also deliver a high capacity of 150 mA h g −1 at the current density of 1 A g −1 over 5000 cycles, as well as superior rate character (97 mA h g −1 at 8 A g −1 ) …”

Monodispersed Silica@Nickel Silicate Hydroxide Core–Shell Spheres for Supercapacitor Electrodes

“…It is found that each value of b at different voltages is around 0.8, indicating that the electrochemical behaviors involve both diffusion and capacitive‐controlled processes. The contribution ratio of the two processes at a certain voltage and fixed scanning rate is calculated on the basis of the given equation…”