关键词: 防腐蚀薄膜, 析氢腐蚀, SnO₂, 聚乙烯吡咯烷酮, 柔性铝-空气电池, 静电纺丝

Abstract:

Objective With the update and iteration of material science and energy technology, the demand for portable wearable electronics is increasing. Therefore, flexible electronic energy storage equipment is particularly important. Flexible Al-air battery can be used as energy storage devices for wearable electronic products due to their excellent characteristics of flexibility and low cost. However, hydrogen evolution corrosion of metal anode of flexible Al-air battery is serious in alkaline environment, which results in uneven anode consumption and battery bulge, shortening battery life and reducing the corrosion of hydrogen evolution of anode.
Method In order to slow down the hydrogen evolution corrosion in the anode of flexible Al-air batteries, nano tin dioxide (SnO₂) and polyvinylpyrrolidone (PVP) were uniformly dispersed in absolute ethanol as the precursor solution, then the SnO₂/PVP membrane were prepared by electrospinning. The membrane-attached aluminum foils served as the anodes for Al-air batteries. SnO₂/PVP membrane were characterized and tested by X-ray diffraction(XRD), scanning electron microscope(SEM), contact angle, hydrogen evolution test, Tafel, EIS and battery performance test, and the effect of SnO₂content on corrosion inhibition rate and battery performance were also explored.
Results XRD and SEM showed that the SnO₂/PVP thin membrane had clear composition (Fig. 4), and SnO₂ nanoparticles were embedded into PVP fibers (Fig. 5). Through the self-made experimental device test, hydrogen evolution rate and hydrogen evolution amount of aluminum foil with functional membrane decreased significantly (Fig. 7). The hydrogen generation rate ratio of the two groups of experimental data with the largest difference reached 3 times. Then we tested the dynamic polarization curves of the potential of aluminum anodes attached with different membranes in 2 mol/L KOH solution, and obtained the corresponding corrosion current density (Tab. 1). When pure aluminum was used as anode, the corrosion current density was 0.29 mA/cm². With the mass fraction of SnO₂ increased to 40% and 50%, the corrosion current density decreased to 0.14 mA/cm² and 0.11 mA/cm², and the corrosion inhibition rate increased to 51.7% and 62.1%, respectively. The result is in good agreement with that of hydrogen evolution rate experiment. The battery performance test and the discharge curve is shown as follows: the discharge voltages of the three cells with the anti-corrosion membrane decreased slightly, but the discharge times of the cells with the 50% SnO₂/PVP membrane reached 168 min and 127 min respectively at the discharge densities of 3 mA/cm² and 5 mA/cm². Compared with pure aluminum anode aluminum-air battery (70 min and 53 min), the utilization rate of aluminum anode metal was increased by 140.0% and 139.6%, respectively. The specific capacity of the battery was positively correlated with the content of SnO₂ in the membrane. Although the anti-corrosion membrane improves the anti-corrosion performance and specific capacity, it sacrifices a certain power density (as indicated in Fig. 10). However, it can still be applied to low-power flexible electronic devices and expand the application of flexible batteries.
Conclusion SnO₂ nanoparticles are embedded into PVP fiber by electrospinning process, and aluminum foil is used as the receiving base to successfully prepare anti-corrosion membrane suitable for flexible Al-air batteries. A flexible Al-air battery was designed and manufactured, the SnO₂/PVP membrane had an obvious inhibition on the hydrogen evolution corrosion of the anode of Al-air battery, and the discharge time of the fabricated flexible battery increased with the increase of the mass percentage of SnO₂ (within a certain range). Under the action of anti-corrosion membrane, the battery power density decreased slightly, but the prepared flexible Al-air battery was still suitable for small power flexible electronic equipment, expanding the application of flexible batteries.

Key words: anti-corrosion membrane, hydrogen evolution corrosion, SnO₂, polyvinylpyrrolidone, flexible Al-air battery, electrospinning