At present, the development of lithium-ion batteries tends to mature, and they have been commercialized and widely used in people’s daily life, such as small electronic devices. However, its limited energy density has become a bottleneck in the development of high-power, high-energy-density devices (such as electric vehicles, etc.), which greatly limits the driving range of electric vehicles on a single charge. The development and utilization of new energy in the future requires a new energy storage system with high specific energy. As a new power technology with ultra-high specific energy, environmental friendliness and low price, metal-air battery (also known as lithium-air battery) undoubtedly has broad application potential and is expected to become a new generation of secondary batteries. It has attracted widespread attention from the scientific research community and industry. Figure 1 shows the energy density diagram of a typical energy storage device.
In 1976, Littauer et al. first proposed a water-based electrolyte lithium-air battery, using metal lithium as the negative electrode, air (or oxygen) as the positive electrode, and an alkaline aqueous solution as the electrolyte. When the lithium-air battery is discharged, the reduction of oxygen mainly generates oxides or hydroxides, and the battery cannot effectively control the chemical reaction between metal lithium and water. In 1996, Abraham et al. first proposed a non-aqueous solvent lithium-air battery. The polymer electrolyte used in the battery design has a specific discharge capacity of 600~1410 mA h/g, and Li2O2 is identified as a possible discharge product. The battery design can slow down the corrosion of lithium metal, thus highlighting the great advantages of lithium-air batteries. However, since the discharge product Li2O2 or LiO2 is insoluble in the organic electrolyte, the air electrode is gradually blocked by the discharge product during the battery discharge process, resulting in the early termination of the battery discharge, which is not conducive to the improvement of the discharge capacity and the long cycle of the battery. This is also one of the most important factors restricting the development of lithium-air batteries.
Subsequently, in 2006, Peter GBruce et al. used XRD and on-site electrochemical mass spectrometry to prove that the charging and discharging of lithium-air batteries were based on the reversible reaction of Li+2e–+O2→Li2O2. Since solid Li2O2 is a wide-bandgap insulator, the oxidative decomposition process is extremely difficult, which will lead to more side reaction products, such as Li2O3, etc., thereby deteriorating the cycle performance of the battery. The development of new and efficient oxidation catalysts and the improvement of the cycle life of lithium-air batteries have become the main research and development direction. In 2012, Peng et al. reported a novel reversible, high-rate lithium-air battery in the journal Science. The battery uses porous nano-gold as the positive electrode material. After 100 cycles of the battery, the discharge capacity retention rate is as high as 95%, and the advanced in-situ online differential electrochemical mass spectrometry technology is used to verify that the battery reaction is based on the reversible generation and decomposition of Li2O2.
Although lithium-air battery research is gradually deepening. However, its basic research, including battery charging and discharging mechanism, air cathode, metal anode and electrolyte, is not enough, the practical barriers have not been broken, and there are still a series of scientific problems that need to be solved before becoming a commercial battery.
In addition, if you are interested, I will recommend you other related lithium battery introduction articles on the development history of lithium-sulfur batteries.