The world is ditching fossil fuels and turning to greener energy sources. One of the most important topics in this area is batteries, which are used in everything from mobile devices to electric vehicles.
In the past, lead-acid batteries were replaced by nickel-cadmium batteries, which in turn were replaced by nickel-metal hydride batteries. After that, lithium-ion batteries and lithium-sulfur batteries were offered to consumers.
Nowadays, lithium-ion batteries seem to be used the most intensively, with their advantages such as fast charging, higher efficiency and recharging without complete discharge. Mobile devices such as phones and tablets, electric cars, buses, ships and even airplanes use lithium-ion batteries.
Aluminum-air batteries are a new alternative
But in recent years, studies on “aluminum-air batteries” have caused excitement across all industries. Although lithium is a limited mineral, aluminum is abundant in many countries, including Turkey. It also claims benefits such as “storing 40 times more energy than lithium-ion batteries” and “charging up to 100 times faster”.
This means that a significantly longer range can be achieved with the same battery size and you can use a phone that charges very quickly for days. The disadvantages include “too much recycling effort” and “the technology is not yet suitable for the end user”.
What do the experts say?
Sabancı University is the only school in Turkey with a minor program in battery science and engineering. Faculty members of the University's Faculty of Engineering and Natural Sciences, Dr. Selmiye Alkan Gürsel, Dr. Alp Yürüm and Deputy Dean Burç Mısırlıoğlu answered questions about aluminum-air batteries for TRT Haber. According to experts, aluminum-air batteries have great potential, but there is still a long way to go.
“Since aluminum is a naturally abundant metal and has relatively low production costs, the development of these batteries is of great interest. In addition, magnesium, calcium and lithium-air batteries are other metal-air battery types that are being researched.”
What are aluminum-air batteries?
The opinions of scientists about aluminum-air batteries can be summarized as follows:
“A type of metal-air (or oxygen) battery. Metal-air batteries have a higher energy density than conventional batteries. The most typical example of metal-air batteries are zinc-air batteries, which have been used for years in specialized areas such as hearing aids. Zinc-air batteries are generally not rechargeable. The energy density is about five times that of lead-acid batteries and is similar to that of lithium-ion (lithium-ion) batteries. The practical energy density of aluminum-air batteries is about twice that of zinc-air batteries (and lithium-ion batteries). However, the charge/discharge life of these batteries is limited due to corrosion. The negative side of the battery (anode) is made of aluminum metal, while the positive side (cathode) is made of a porous material that reacts with oxygen in the environment. The charging reaction is not very efficient. If 100 units of energy are consumed for charging, about 75 units of them are used to charge the battery, the remaining part is used as a resistor, etc. For various reasons it seems like a loss.
On the negative side of the battery (anode) a reaction occurs that supplies electrons, while on the positive side (cathode) a reaction occurs that consumes electrons. These reactions produce free electrons and ions, and the flow of electrons from the anode to the cathode occurs in devices, etc. It provides the necessary electrical energy for In normal batteries, this reaction takes place in a closed system. Aluminum-air batteries, on the other hand, are an “open” system because these batteries require a constant supply of oxygen from outside in order to continue producing energy. In this respect, aluminum-air batteries are similar to fuel cells. “The fact that aluminum metal is light and the oxygen reaction provides many electrons means that the energy density of these batteries is high, but unwanted reactions also occur, reducing the efficiency and life of aluminum-air batteries.”
What work is being carried out?
“Work on this technology continues in three different areas; Anode, cathode and electrolyte… The reduction of undesirable side reactions with different alloys in the anode area are priority research topics. On the cathode side, catalysts are being developed for more effective oxygen reactions. But porous and conductive structures are also being investigated for oxygen gas flow. Instead of water-based electrolytes, organic solvents or solid electrolytes are also being investigated. Sabancı University is also conducting studies on oxygen catalysts, porous cathode structures and solid-state polymer electrolytes for metal-air batteries.”
A promising technology
“Aluminium-air batteries have the potential to meet future consumer needs. Their wide range of applications, from electric vehicles to military systems, environmentally friendly battery reactions and the cheap and abundant availability of aluminum make these batteries a promising battery technology of the future. However, current aluminum-air battery technology still needs to be improved to enable industrial-scale production of electrodes and electrolytes.”
The focus should be on optimization
“Research on aluminum-air batteries should focus on optimizing the cathode, anode, electrolyte and other battery components to ensure that they can be easily manufactured on an industrial scale, perform well and are economical.”
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