This paper reports on the improvement of discharge performances of magnesium-air batteries by adding sodium phosphate and sodium dodecylbenzenesulfonate to sodium chloride aqueous solution. Four different electrolytes are tested. Results obtained show that the discharge potential and anode utilization of magnesium-air battery increase significantly with addition of the additives. With an electrolyte of 3.5 wt% sodium chloride+0.5 g · L −1 sodium phosphate, the discharge potential increases from 1.120 V to 1.150 V and the anode utilization increases from 44.1% to 49.1%. The self-corrosion rate of anode has a tendency to decrease with addition of the additives. In solution of 3.5 wt% sodium chloride+0.5 g · L −1 sodium dodecylbenzenesulfonate +0.5g · L −1 sodium phosphate, the self-corrosion is low and the inhibition efficiency can reach 95.2%. Magnesium-air (Mg-air) battery plays an increasingly significant role in power source energy and storage devices.1,2 There are lots of advantages of Mg-air battery, such as high theoretical potential (3.09 V), high specific energy density (6.8 kWh · kg −1 ), neutral electrolyte, environmental friendliness, and low cost.
3-5Although Mg-air battery has a promising future, there are still some problems remarkably limiting its development and delaying its application in daily life. One of the major problems is anodic polarization during battery discharge. [6][7][8] As the total reaction of Mgair battery (Eq. 1) shows:The discharge product is magnesium hydroxide which has a tendency to attach to the surface of anode. It can reduce the reactionsurface area leading to a decrease of discharge potential when battery discharges in a constant-current mode. As we all know, the potential of Mg is −2.37 V (vs · SHE) and it can react spontaneously with aqueous solution according to the following equation:This wasteful self-corrosion leads to low utilization efficiency during discharge process. 9,10 There are numerous efforts to reduce selfcorrosion of magnesium, focusing either on how to improve anode behaviors [11][12][13] or how to optimize electrolyte composition. 14,15 Compared to studies for anode improvement, there are few studies aimed at electrolyte optimization. Furthermore, adding additives to the electrolyte is known to be a convenient and effective method. For example, the self-discharge capacity is significantly increased by adding water soluble graphene to NaCl solution.14 Jing et al. 15 found that when NaF and Na 3 PO 4 were used as additives to electrolyte Mg-MnO 2 cell demonstrated an excellent discharge performance. And sodium dodecylbenzenesulfonate (SDBS) as a good organic inhibitor can work together with the Na 2 SiO 3 on the AZ31 magnesium alloy in 1% NaCl.
16Although electrolyte is one of the most crucial factors, additive research is few comparing the anode materials. Up to now, Mg-air batteries with Na 3 PO 4 and SDBS as additives have never been studied. It is known that sodium chloride aqueous solution (3.5% NaCl) is the most suitable electrolyte for Mg-air batt...