Electrochemical Behavior and Discharge Performance of a Low-Alloyed Mg-Ag Alloy as Anode for Mg-Air Battery
HAO Xubang1, CHENG Weili1,2(), LI Jian2, WANG Lifei1, CUI Zeqin1, YAN Guoqing3, ZHAI Kai3, YU Hui4
1 School of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China 2 Salt Lake Chemical Engineering Research Complex, Qinghai University, Xining 810016, China 3 Shanxi Regal Advanced Material Co. Ltd., Yuncheng 043800, China 4 School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300132, China
Cite this article:
HAO Xubang, CHENG Weili, LI Jian, WANG Lifei, CUI Zeqin, YAN Guoqing, ZHAI Kai, YU Hui. Electrochemical Behavior and Discharge Performance of a Low-Alloyed Mg-Ag Alloy as Anode for Mg-Air Battery. Acta Metall Sin, 2025, 61(6): 837-847.
Primary Mg-air batteries have attracted considerable attention in the field of standby emergency energy storage in the wilderness because of their high theoretical voltage (3.1 V) and appreciable specific energy (6.8 kWh/kg). However, because of the severe self-corrosion and sluggish anodic kinetics of Mg anodes, the actual performance of Mg-air batteries is far from the theoretical limits. To synergistically enhance the discharge voltage and specific energy of Mg-air batteries, a low-alloyed Mg-1Ag (mass fraction, %) anode was developed, and its microstructure, electrochemical behavior, and discharge properties were evaluated. The results showed that the extruded alloy mainly consisted of equiaxed grains with an average grain size of (14.19 ± 2.27) μm. The anode studied exhibited a typical extrusion texture with a basal pole perpendicular to the transverse direction, and the texture intensity was 11.05. Additionally, the extruded alloy was shown to exhibit localized segregation of Ag. The Mg-air battery based on the Mg-1Ag alloy as the anode exhibited a stable discharge process. In addition, the cell voltage and specific energy reached 1.344 V and 1374.34 mWh/g at 10 mA/cm2, respectively. The acceptable discharge performance of the anode was mainly due to the redeposition of metal Ag on the electrode surface, the multi-cracked discharge product film, and the non-basal-oriented grains with a high-volume fraction.
Fund: National Natural Science Foundation of China(52375370);Natural Science Foundation of Shanxi Province(202103021224049);Shanxi Zhejiang University New Materials and Chemical Research Institute Scientific Research Project(2022SX-TD025);Open Project of Salt Lake Chemical Engineering Research Complex, Qinghai University(2023-DXSSKF-Z02)
Corresponding Authors:
CHENG Weili, professor, Tel: (0351)6010021, E-mail: chengweili7@126.com
Fig.1 Crystallographic orientation map (a), EBSD mapping of grains (b), and (0001) pole figures of extruded Mg-1Ag (Q1) alloy (c) (ED—extrusion direction, TD—transverse direction, fDRXed grains—area fraction of dynamically recrystallized grains, fSubgrains—area fraction of subgrains, fDeformed grains—area fraction of deformed grains)
Fig.2 Grain size distributions of Q1 alloy (AGS—average grain size)
Fig.3 Low (a) and high (b) magnified SEM images and EDS element mappings of Mg (c) and Ag (d) of Q1 alloy
Fig.4 XRD spectrum of Q1 alloy
Point
Mg
Ag
O
A
93.91
0.31
5.78
B
88.92
0.31
10.77
Table 1 EDS results of Q1 alloy in Fig.3b
Fig.5 Open circuit potentials (EOCP) (a), anodic (b) and cathodic (c) branches of the polarization curves, and Nyquist diagram under open circuit potentials (d) of Q1 alloy and high purity magnesium (HP Mg) (E—potential; i—current density; Z' and Z"—real part and imaginary part of the impedance, respectively; SCE—saturated calomel electrode. Inset in Fig.5d is the zoom-in view of the box area)
Specimen
EOCP (vs SCE) / V
Ecorr (vs SCE) / V
icorr / (μA·cm-2)
βc / mV
βa / mV
Q1
-1.609
-1.5344
79.16
215.35
46.48
HP Mg
-1.649
-1.5997
491.51
366.56
259.16
Table 2 Electrochemical parameters of Q1 alloy and HP Mg
Fig.6 Equivalent circuit diagram of the alloy (Rs—solution resistance; Rfand CPEf—resistance and capacitance of the corrosion products generated on the surface, respectively; L and RL—inductor and resistance, specifying the presence of desorption process of corrosion products; CPEdl—capacitance of the electrical double layer at the interface; Rct—charge transfer resistance; WE—working electrode; RE—reference electrode)
Specimen
Rs
Ω·cm2
CPEdl / (F·cm-2)
Rct
Ω·cm²
Rf
Ω·cm²
L
Ω·cm²
CPEf / (F·cm-2)
RL
Ω·cm²
T
n1
T
n2
Q1
2.412
4.47 × 10-4
0.91
4.838
29.60
116.4
1.45 × 10-4
0.97
29.6
HP Mg
2.908
2.32 × 10-5
0.90
3.524
20.58
247.7
8.65 × 10-5
1.03
40.7
Table 3 Electrochemical parameters obtained from the fits of the experimental electrochemical impedance spectroscopy (EIS) data
Fig.7 Discharge curves of Q1 alloy and HP Mg at different current densities (a) 2.5 mA/cm2 (b) 5 mA/cm2 (c) 10 mA/cm2 (d) 20 mA/cm2
Fig.8 Discharge performance of Q1 alloy and HP Mg at different current densities (a) anodic efficiency and cell voltage (b) specific capacity and specific energy (c) discharge performance statistics of anode materials for Mg-air batteries at 10 mA/cm2 in recent years[1-3,5~8,11,20-26]
Fig.9 Surface (a-h) and cross-sectional (i-l) SEM images for Q1 alloy after discharge in 3.5%NaCl solution at 2.5 mA/cm2 (a, e, i), 5 mA/cm2 (b, f, j), 10 mA/cm2 (c, g, k), and 20 mA/cm2 (d, h, l) for 10 h (Figs.9e-h show the local magnified morphologies corresponding to the boxes in Figs.9a-d, respectively)
Fig.10 XPS of the oxide films on the alloy surface after discharge at 2.5 and 20 mA/cm2 in 3.5%NaCl solution for 10 h, including high-resolution Mg1s (a), Ag3d (b), Cl2p (c), and O1s (d) spectra
Fig.11 Surface SEM images of Q1 alloy discharged at different current densities for 10 min (a, f), 30 min (b, g), 1 h (c, h), 10 h (d, i) after removing the discharge products; and 3D morphologies of Q1 alloy discharged for 10 h after removing the discharge products (e, j) (Insets show the high magnified images) (a-e) 2.5 mA/cm2 (f-j) 20 mA/cm2
Fig.12 Crystallographic orientation maps for Q1 alloy (fBasal grains and fNon-basal grains—fractions of basal-oriented grains and non-basal-oriented grains, respectively; D, G, and H—areas similar to the dissolution morphologies indicated by the white dotted line in Fig.11a and red and green dotted lines in Fig.11f, respectively) (a, e) basal-oriented (a) and non-basal-oriented (e) grains distributions (b, f) grains that size distributions in the range of 0-14.19 μm (b) and more than 14.19 μm (f) (c, g) basal-oriented grains that grain size distributions in the range of 0-14.19 μm (c) and more than 14.19 μm (g) (d, h) non-basal-oriented grains that grain size distributions in the range of 0-14.19 μm (d) and more than 14.19 μm (h)
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