Electrochemical Performance of a Thin Fabric ZnO Anodic Material in a Free Membrane Ni–Zn Battery

Abstract

The Ni-Zn secondary battery is a promising candidate in secondary alkaline storage batteries due to its high specific energy density.1 However, they have not come to the commercial markets in spite of their many advantages such as low toxicity and low cost, because of the short and unpredictable lifetime of the Zn electrodes when subjected to charge-discharge cycling.2 In order to enhance the cell performance, many attempts have been made to reduce the solubility of active materials 3 and suppress the formation of zinc dendrite. Many researchers have concluded that the electrochemical performance of Ni/Zn battery should be closely related to the microstructure of ZnO itself. 4 In particular, Yang and coworkers 5 have reported the electrochemical performance of ZnO with different morphologies (hollow ZnO and the hexagonal taper-like ZnO) as anodic materials for Ni/Zn secondary batteries; the initial discharge capacity of hollow ZnO was 476 mA/(h g), and the discharge capacity remained almost unchanged with the capacity retention ratio of 99.5% over 50 cycles. However, there are very few investigations that have been devoted to ZnO as an anodic material until now.In the present work, we prepared thin fabric ZnO using a simple precipitation route, and investigated in detail its performance as the anodic active material for Zn/Ni cells. Conventional ZnO was used to compare the difference in the electrochemical properties. Thin fabric consisting of ZnO nanoparticle was prepared through a precipitation route. A NaOH solution of 8.0 mol was slowly dropped into 2.0 mol Zn(NO 3 ) 2 4(H 2 O) aqueous solution, and then the mixed solution was intensely stirred for 3 h. Afterward, the white precipitate in the solution was filtrated and washed several times with distilled water until the pH reached 7.0. The washed powder was dried and crystallized at 70C for 24 h. The chemical reaction can be represented as follows: 2Zn(NO 3 ) 2 4(H 2 O) + 8NaOH ! 8Na + + 4NOIn the washing step, the 8Na + , 4NO − 3 , and 4OH − ions were removed, and finally crystallization was continued through the next step at 70 C for 24 h: 2Zn(OH) 2 ! 2ZnO + 2H 2 O. The acquired material was named fabric ZnO, and a conventional ZnO was used for comparison. The synthesized ZnO powder was characterized using X-ray diffraction (X'pert MRD, Panalytical, The Netherlands) and transmission electron microscopy (TEM, JEM-2000EX, JEOL, Japan). The galvanostatic charge/discharge cycles were performed by a battery test system (WPG100e, WonATech., Seoul, Korea) using a single flow-type cell designed by Vitzrocell Co. Ltd., Yeosan, Korea, as shown in Figure 1 , respectively. The cell was filled with 5.0 M KOH aqueous solution, which was saturated by 0.46 M ZnO as the electrolyte. Before the cycling tests, the cells were preactivated by charging at a current density of 0.1C for 10 h and discharging at 0.2C to the 1.4 V cutoff. During the cycling procedure, the cells were charged at a current density of 2 A for 1 min and discharged at 1 A to the 1.4 V cutoff. The table in ...

Communication—Bi@CMC Composite as a Multifunctional Electrolyte Channel for the Anode of Rechargeable Zn–Ni Battery

“…Moreover, after the 100th cycle, the discharge capacities were 193.5 mAh g −1 and 137.0 mAh g −1 , re-spectively; hence, the performance of the anode including Bi@CMC was higher than that of pristine CMC. Notably, the discharge specific capacity of the Zn-Ni battery in this study was lower than that of our previous work and others, [11][12][13][14][15][16][17][18][19] because the electrolyte used here was 6 M KOH and lacked ZnO. To address the dissolution of a ZnO electrode in an alkaline electrolyte, dissolving saturated or nearly saturated ZnO in a KOH solution in advance has been widely employed, and high-performance Zn-Ni batteries have been obtained.…”