Significant Enhancement in the Electrochemical Performances of a Nanostructured Sodium Titanate Anode by Molybdenum Doping for Applications as Sodium-Ion Batteries

Abstract

Sodium titanate is considered as one of the most promising anode materials for sodium-ion batteries without any serious safety concerns due to its high theoretical capacity at sufficiently low voltage. However, its low electrical conductivity severely restricts the electrochemical performances as an anode for sodium-ion batteries. Because suitable doping is always found to be a trump card strategy to especially enhance the conductivity, a molybdenum-doped sodium titanate nanostructured anode was successfully synthesized for the first time using the solvothermal method. Molybdenum-doped sodium titanate electrode materials showed superior electrochemical performances than the pristine sample. On more precise consideration, the sodium titanate electrode doped with 15 wt % molybdenum not only delivers ∼24% high reversible capacity at a high current density of 1 A g–1 in comparison to the pure sodium titanate electrode but also maintains it until 2500 cycles. It is believed that the improved electrochemical performances are mainly contributed by the combination of enhanced electrical conductivity and oxygen vacancy generated in the sodium titanate framework as a result of molybdenum doping. Molybdenum doping may also allow Na+ ion diffusion through multiple pathways within the sodium titanate crystal lattice and increase the transport rate of Na+ ions.

A highly stable δ-MnO2 cathode with superior electrochemical performance for rechargeable aqueous zinc ion batteries

“…The relative contributions from the diffusion-controlled process and Zn 2+ insertion at a fixed potential can be determined using this equation. 27 The obtained result (Fig. 3(d)) shows that the nearly ∼91% share of the total charge follows the diffusion-controlled behavior at a scan rate of 1 mV s −1 .…”

“…Generally, the slope obtained near 0.5 indicates a diffusion-controlled (battery) behavior, whereas the slope at 1.0 represents a surface diffusion (capacitor) process. 27 The slopes for both cathodic and anodic reactions were found to be 0.603 and 0.7, respectively, which are close to 0.5, thus indicating a diffusion-controlled process for the δ-MnO 2 cathode (battery behavior). 12 On the other hand, the current response at a fixed potential can be expressed as a combination of the surface capacitive effects and diffusion-controlled insertion, which can be expressed by the following equation:…”

“…The relative contributions from the diffusion-controlled process and Zn 2+ insertion at a fixed potential can be determined using this equation. 27 The obtained result (Fig. 3(d))…”

“…1 Furthermore, the charge storage behavior of the electrode was characterized into diffusion-controlled, pseudo-capacitance controlled and nonfaradaic electric double-layer capacitance contributions. 27,28 These parameters can be calculated using the power law relationship, i = an b , where i is the redox peak current, v is the scanning rate, and a and b are adjustable parameters. Particularly, the value of b determines the predominant Zn 2+ storage behavior.…”

Ternary Fe3O4/reduced graphene oxide/phytic acid doped polyaniline hybrid based supercapacitive electrode with high capacitance retention and good cycling stability

“…have been widely investigated to address the existing global energy crisis. 5,6,[8][9][10][11][12] Among various green energy devices, SCs, also known as electrochemical capacitors, are of special attention due to their high power density, robust reversibility and rapid charging/discharging rate compared to lithium-ion batteries and fuel cells. [13][14][15][16] According to their energy storage mechanisms, SCs can be mainly divided into electric double-layer capacitors (EDLCs: energy storage based on charge separation at the electrode/electrolyte interface) and pseudocapacitors (energy storage based on the redox reaction at the electrodes).…”