Lithium–air battery

The lithium-air battery is is a state in 2013 with research execution of a rechargeable lithium -ion battery with a cell voltage of 2.91 V. First, theoretical work on lithium-air batteries are from the mid 1990s and go on Kuzhikalail M. Abraham and Jiang Zhiping back.

There are several possible embodiments which are the subject of various research for several decades. The reason for the research activities in this area lies in the theoretically high specific energy density of 11,14 kWh / kg. This would lithium air battery is an approximately 10 - to 20 -fold have higher energy density than a conventional lithium-ion batteries.

Construction

Despite the differences in details embodiments, the basic principle is the same for all lithium-air battery types. At the discharge of the negative electrode made ​​of metallic lithium with the loss of an electron emitted positive lithium ions through the electrolyte to the positive electrode, where the lithium ion with oxygen ( O2) at first to lithium ( Li2O ), and then to lithium peroxide ( Li2O2 ) oxidized. Metallic lithium on the positive electrode the oxygen (O2) is dispensed on the negative electrode deposited: during charging of the battery, this process is reversed.

The positive electrode is constructed as mesoporous carbon and is not directly involved in the electrochemical process. The carbon acts as an electrical conductor and connection to facilitate the mesoporous structure to maximize the surface area for reaction with the oxygen of the lithium ions in the positive electrode. The negative electrode consists of a block of metallic lithium. There is an electrolyte, which, depending on the embodiment, in the liquid form, or may also be fixed between the two electrodes. In the latter case, there is a Festkörperakkumulator.

Technical difficulties

The real implementation of lithium-air batteries come across various difficulties, which is why this accumulator is restricted to research of no practical significance. The main problems of the lithium-air battery include:

• The mesoporous carbon electrode there is a clumping, which reduces the capacity.
• The effects of pore size and their distribution in carbon is incompletely understood.
• If the oxygen in the ambient air is drawn, it can lead to an impairment of the galvanic cell in the ambient air by the ever-present water vapor ( humidity). If the cell is hermetically sealed decreases the high specific energy density, since the reservoir for the oxygen must be taken into account.
• At the metallic lithium electrode may lead to internal electrical short circuits in the battery by unintentional crystal growth and the formation of so-called dendrites.