Introduction to Metal-Air Batteries: Theory and Basic Principles

Nowadays, energy is the power engine that sustains the operation of our society. In the energy field, we are confronted with a daunting challenge caused by the gradual depletion of fossil fuel. To secure a safe and sustainable energy supply, renewable energies such as solar and wind have been developed. However, these energies are geographically limited and intermittent, thus calling for reliable electrical energy storage (EES) system for stable and efficient power delivery. Simultaneously, the growing number of transportation vehicles has made the development of reliable EES system a task of urgency. Among various EES systems, rechargeable batteries are the most promising to meet these needs thanks to their high energy density and high energy efficiency [1]. Among them, the lithium-ion battery (LIB), which is operated on the basis of intercalation mechanism, has played an important role in our society in the past two decades [2]. However, the low energy density of LIB has restricted its application as the energy supplier of next generation. Under this circumstance, the development of metal–air battery has provided a solution benefitting from its much higher energy theoretical energy density than that of LIB. In contrast to the closed system of LIB, the metal–air battery are featured with an open cell structure, in which the cathode active material, oxygen, coming from ambient atmosphere. In general, the metal–air battery consists of metal anode, electrolyte, and porous cathode. Metals such as Li, Na, Fe, Zn, etc. can be used as anode materials in metal–air batteries. And the theory and battery electrochemistry will be briefly discussed on the basis of metal–air battery with different metallic anodes in the following section, which will be discussed in detail in the following chapters.