However, the redox reversible reactions and cyclability of those batteries are far below expectations. Among the several structures of Li-air batteries, using an aqueous electrolyte provides a higher efficiency and cyclability due to the high ionic mobility and the solubility of discharge products [1]. However, water must not contact lithium metal anode to avoid violent reaction, producing heat and gas evolution. Thus, we apply organic electrolyte on lithium metal anode and aqueous electrolyte on cathode to protect lithium metal and to make highly reversible electrochemical reactions, respectively.
During discharging, the value of pH increases due to the formation of LiOH, damaging the membranes [2,3] and the saturation of LiOH formation [4].
In the system of Li-air, the solubility of O2 in aqueous solution is a key parameter to obtain the highly reversible electrochemical reactions and high energy density.
We studied the O2 solubility in terms of the concentration of LiOH aqueous solution and other salts mixed solutions by means of the electrochemical techniques. Fig. 1 shows the O2 solubility increased with decreasing the concentration of LiOH. We will show the behavior of the O2 solubility of different salts mixed aqueous solutions and the charge/discharge behaviors in dual electrolytes systems.
Fig. 1. The concentrations of O2 in terms of the various concentrations of LiOH aqueous electrolyte.
References
[1] X. Wang, Y. Hou, Y. Zhu, Y. Wu, R. Holze, Scientific Reports 2013, 3, 1401.
[2] D.-J. Lee, O. Yamamoto, D.-M. Im, Y. Takeda, N. Imanishi, 2012, Patent Application No. 13/191769.
[3] J. Christensen, P. Albertus, R. S. Sanchez-Carrera, T. Lohmann, B. Kozinsky, R. Liedtke, J. Ahmed, A. Kojic, J. Electrochem. Soc. 2012, 159, R1-R30.
[4] Y. Wang, H. Zhou, J. Power Sources 2010, 195, 358-361.