ผลของแมกนีเซียมและอินเดียมในโลหะผสมสังกะสีต่อประสิทธิภาพ เชิงไฟฟ้าเคมีของขั้วแอโนดสังกะสีในแบตเตอรีสังกะสี-อากาศ

Abstract

Zinc is utilized as anodes in Zn-air batteries. The addition of a small amount of alloying element such as Mg to zinc can improve its electrochemical properties. Zn-Mg alloys containing nominal Mg contents of 0.1, 0.5, 1.0, 3.0 and 5.0 wt.% and Zn-Mg -In alloys containing nominal Mg contents of 0.1 and 0.5 wt.% , In contents of 0.1 0.1, 0.5, 1.0, 3.0 and 5.0 wt.%,were prepared by melting and casting into an iron mold at a casting temperature of 750 ºC and then quenching in air at room temperature. Microstructural examination found that the alloys with 0.1 and 0.5 wt.%Mg contained η-Zn phase and eutectic structure which consisted of Zn-rich and Mg-rich phase (Mg2Zn11 intermetallic compound). Indium addition refined the grain size of Zn-(0.1-0.5)wt.%Mg alloys, the grain size decreasing with increasing indium contents. Potentiodynamic polarization testing showed that the Icorr values of Zn-Mg alloys and Zn-Mg-In alloys were higher than that of pure zinc and increased with increasing Mg and In content. A single cell of a zinc–air battery was tested, MnO2 was used as a catalyst coating on a gas diffusion layer (GDL). The electrolyte used in the zinc–air battery was 6 M KOH, and Zn, Zn-Mg alloys, and Zn-Mg-In alloys were assessed as potential materials for the anode. For each alloy the power density was obtained using a galvanodynamic method with a current density ranging from 0 to 80 mA/cm2. The Zn-0.5wt.%Mg and Zn-0.1wt.%Mg-In alloys containing 0.5 wt.%In showed current densities higher than for pure Zn. Discharge curves were obtained using a current density 20 mA/cm2. Specific capacity was normalized to the mass of consumed Zn at an applied current density of 20 mA/cm2. The results showed that the specific capacity gradually increased for Zn alloys containing 0.1 wt.% Mg and 0.5 wt.% In content. Cycling experiments were performed using the recurrent galvanic pulse method for 100 cycles, where one cycle consisted of a discharging step (20 mA/cm2 for 5 minutes) followed by a charging step with the same current and time duration. The charge and discharge voltages of the zinc air battery have shown promising performance. the battery with Zn containing small Mg and In contents can still show both long term durability and narrow charge–discharge voltage gap (~2.0 V). The morphology and microstructure of metal oxides formed on each anode after discharge testing were investigated using scanning electron microscopy equipped with energy dispersive x-ray spectrometry (SEM-EDS) and x-ray diffractometry (XRD). The porous structure of the mixed metal oxides of ZnO/Zn(OH)2/MgO/Mg(OH)2 which formed on the Zn-Mg alloy anodes in each composition, and the mixed metal oxides of ZnO/Zn(OH)2/MgO/Mg(OH)2/In2MgO4/In2O3 which formed on the Zn-Mg-In alloy anodes improved the battery performance during discharge. This indicated that Zn-0.1wt.%Mg-(0.1-0.5wt.%)In could provide improved electrochemical performance when used as an anode compared the use of pure Zn. The synthesized alloys are considered as a promising material for Zn-air batteries.