A Facile Route for the Preparation of Calcium Zincate and its Application in Ni–Zn Batteries

Abstract

Calcium zincate microcrystals are successfully prepared with calcium carbonate and zinc oxide as reactants in alkaline solution without protective atmosphere. The structure and composition are analyzed by X-ray powder diffraction (XRD) analysis, thermodiffractometry, scanning electron microscope (SEM), energy dispersive X-ray analysis (EDS), and thermogravimetric analysis (TGA). Electrochemical measurement results prove that the as-synthesized calcium zincate exhibits a good reversibility, a high specific capacity and a good cycling stability. This is a cheap and facile way to synthesize calcium zincate materials which may benefit for mass production of calcium zincate.Calcium zincate has attracted great interests as an active material for secondary Zn electrodes employed in Ni-Zn battery, 1-3 because it is able to promote a better charge/discharge reversibility as well as solve the problems of shape change and dendrite formation in the Zn electrodes. 3,4 This material has been synthesized by different ways, including chemical co-precipitation method under strong alkali solution, 5 mechanical ball milling technique using ZnO and Ca(OH) 2 as reactants in aqueous medium, 6,7 solid-phase method without strong alkali and application of microwave-hydrothermal conditions. 8,9 However, concerning the preparation process, some authors have concerns about deleterious effects for the exposure to CO 2 in the air directly or indirectly, because they expected that CO 2 would react with Ca(OH) 2 to generate CaCO 3 and which will not react with ZnO to form Calcium Zincate, 8,10-12 so they use well-sealed reactors and other protections such as argon or nitrogen atmospheres to avoid any possible interference by CO 2 . In this paper we demonstrate that CaCO 3 can be used in unsealed reactors with an air atmosphere to synthesize wellcrystallized tetragonal-shape calcium zincate at room temperature. ExperimentalAll chemicals used in our experiments were of analytical grade. The water used for solution preparation is distilled water.Synthesis of calcium zincate.-Under continuous stirring, 5.0 g CaCO 3 and 8.14 g ZnO were added to a rocking flask containing 500 mL 20 wt% KOH saturated with ZnO. After reacting for 24 h at room temperature (25 • C), the solution was aged for another 12 h. Then it was filtrated. The obtained solid product was subsequently washed for several times with distilled water till the pH of the filtrate was about 7 and then dried at 50 • C for 12 h.Structural characterization of calcium zincate.-The crystal structure of calcium zincate was determined by X-ray diffraction analysis using a X'pert PRO Panalytical diffractometer with CuKα radiation at 40 kV nominal voltage and 30 mA anodic current. Thermodiffactometric measurements were performed on the Bruker D8 Advance X-ray diffractometer with CuKα radiation at 40 kV nominal voltage and 200 mA anodic current under vacuum. Samples were heated up to a given temperature (10 • C/min). The patterns were recorded after a delay time of 5 min to ensure sample thermal stab...

Performance and failure mechanisms of alkaline zinc anodes with addition of calcium zincate (Ca[Zn(OH)3]2·2H2O) under industrially relevant conditions

“…Filled cells were cycled at room temperature using an Arbin BT-2000 48-channel battery tester. There are two ways to calculate the theoretical capacity of CaZn, (1) based on the theoretical capacity of 347 mAh/g 39,40 given in the literature and (2) based on the theoretical amount of Zn present and using its theoretical capacity of 820 mAh/g. In a typical pure CaZn anode there is approximately 6.…”

“…18,[35][36][37][38] collectors, while the addition of powder bismuth oxide is easy and cheap to incorporate into the manufacturing process. Despite CaZn showing improvement in cyclability at higher utilization 39,40 , studies only cycle CaZn against nickel Ni(OH) 2 counter electrodes because they are at the same state-of-charge. In order to drive costs of grid scale energy storage down from $300/ kWh to $100/kWh or less 41 , CaZn anodes need to be paired with MnO 2 electrodes because nickel cost ten times more than MnO 2 .…”

Interface Engineering of Zinc Electrode for Rechargeable Alkaline Zinc‐Based Batteries

“…When discharged at a relatively low current of 40 mA g −1 , the capacity utilization of the synthesized calcium zincate is 60.8%. [96] Layered double hydroxides (LDHs) are another kind of efficient additives that can be used to suppress the ZnO dissolution in the electrolyte. Xie et al [21] introduced Zn-Al-LDHs as anode additives for rechargeable zinc-nickel battery.…”

“…When discharged at a relatively low current of 40 mA g −1 , the capacity utilization of the synthesized calcium zincate is 60.8%. [ 96 ]…”

A novel ZnO@Ag@Polypyrrole hybrid composite evaluated as anode material for zinc-based secondary cell

“…Calcium hydroxide has long been considered as an effective additive, it can react with zincate ions to form insoluble compound, thereby maintaining zinc species around the electrode 23 . Furthermore, calcium zincate itself can also be used as electrode active material, it presents an improvement of electrochemical properties compared to those of conventional ZnO 24 25 . In addition, surface decorating of zinc metal or zinc oxide with other materials is regarded as a more effective strategy to improve comprehensive properties of zinc electrode.…”