Three-Dimensional Nanostructured Air Electrode for Sodium–Oxygen Batteries: A Mechanism Study toward the Cyclability of the Cell

Abstract

A binder-free three-dimensional (3D) nanostructured air electrode composed of vertically grown nitrogen doped carbon nanotubes on carbon paper (NCNT-CP) is developed and applied to Na−O 2 cells. The 3D architecture of the air electrode results in increased discharge capacity by optimizing the utilized area of the electrode material. The chemical and electrochemical reaction mechanisms of the cell are also explored with the use of synchrotron-based X-ray absorption spectroscopy (XAS). Investigation of the discharge product of Na−O 2 cells during discharge and charge cycles using X-ray absorption near-edge structure (XANES) indicates that both sodium superoxide and peroxide are produced under various physicochemical conditions and can be subsequently decomposed with different overpotentials. Furthermore, formation of carbonate-based parasitic products is also shown to restrict the cyclability of the cell.

Hierarchical Porous Carbon Spheres for High‐Performance Na–O2 Batteries

“…[27] Yadegari et al employed corrosive gas-treated mesoporous carbon as the oxygen cathode in Na-O 2 batteries and identified that both NaO 2 and Na 2 O 2 were produced at the end of discharge. [21,25,30,31] To achieve high-performance and low-cost Na-O 2 batteries, it is important to rationally design and fabricate carbon-based oxygen electrodes that can sustain the desired Na-O 2 electrochemistry (i.e., formation and decomposition of NaO 2 ) and maximize the performance (capacity, cyclability, and rate capability). [21,25,30,31] To achieve high-performance and low-cost Na-O 2 batteries, it is important to rationally design and fabricate carbon-based oxygen electrodes that can sustain the desired Na-O 2 electrochemistry (i.e., formation and decomposition of NaO 2 ) and maximize the performance (capacity, cyclability, and rate capability).…”

“…The galvanostatic discharge/ charge performances of Na-O 2 cells with PCS electrodes were examined in the voltage range of 1.8-3.0 V at room temperature. [29,31] A comparison of the rate capabilities of the PCS and CB-based Na-O 2 batteries is shown in Figure 2c, and the effects of carbon loading on the discharge capacity of the respective Na-O 2 cells are shown in Figure 2d. The Na-O 2 cell with PCS cathode achieved a much higher discharge capacity (16 500 mA h g −1 ) than that of the cell with CB electrode (7790 mA h g −1 , Figure S3, Supporting Information) at 500 mA g −1 .…”

Ab initio prediction of borophene as an extraordinary anode material exhibiting ultrafast directional sodium diffusion for sodium-based batteries

“…Sodium-ion and sodium-oxygen batteries have recently drawn considerable attention as a promising alternative to lithium-based batteries due to the abundance and low price of sodium element [1][2][3][4][5][6]. However, sodium is a highly reactive metal with low melting temperature, and also shares the same dendrite problem with lithium, all of which pose sever safety concern [7,8].…”

Electrolyte-controlled discharge product distribution of Na–O2batteries: a combined computational and experimental study

“…In previous experimental study, the observed charge voltage profile was classified into three different plateaus. 19,20 For comparison, we further plotted the experimental and computational charge potentials in Figure 4. The computational average charge potentials (3.60 V, 2.92 V, and 2.59 V) are well consistent with experimental observation for Na 3 O 4 -like species are very possible to exist in the discharge and charge processes in Na-O 2 battery.…”

“…[1][2][3][4][5][6][7][8][9][10] The composition of discharge products can be regulated by tuning their reaction conditions such as adding redox mediators [11][12][13][14][15][16][17][18] and changing electrochemical environment. [19][20][21][22][23] Some monovalent discharge products such as LiOH 18 and LiO 2 23 could be formed by adding some mediators and controlling electrode structures. These regulations were demonstrated to have significant effect on reducing overpotential, avoiding side-reactions, and improving reversibility.…”