Metal-air batteries are electrochemical batteries with an air electrode as the positive electrode and a metal electrode as the negative electrode. The metal-air batteries that have made research progress include zinc-air batteries, aluminium-air batteries, magnesium-air batteries, lithium-air batteries and so on.
Zinc air batteries are the most mature and promising air batteries, which have been or will be used in new energy vehicles and power supply systems, and the installation cost is expected to be less than 1/4 of that of lithium-ion batteries.
The advantages of zinc air batteries are environmentally friendly, safe, high energy density and low cost. The theoretical energy density of zinc-air battery is 1360Wh/kg, while the theoretical energy density of lithium-ion battery is only 460Wh/kg.
However, the disadvantages of zinc air batteries are also obvious. The zinc electrode is unstable in alkaline solution, high self-discharge rate, electrolyte leakage, limited power output and short service life.
These shortcomings of zinc air batteries are more fatal, so it is not yet possible to completely replace lithium batteries, but as a more environmentally friendly battery, the industry is very optimistic about its development prospects, and scientists are constantly attacking the shortcomings of zinc air batteries, so that they can be used in more fields.
Recently, researchers at Edith Cowan University (ECU) in Australia redesigned zinc air batteries by combining the use of carbon, cheaper iron and cobalt-based minerals and other new materials, and found in tests that the new design and combination greatly improved the service life and performance of zinc batteries, which could replace lithium-ion batteries as a safer and more sustainable battery alternative.
This latest result was published in the journal EcoMat. The scientists say that the new design is so efficient that it suppresses the internal resistance of the battery, and the device’s voltage is close to the theoretical voltage, resulting in high peak power density and ultra-long stability.
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Redesigning zinc air batteries with new materials
A breakthrough by an Edith Cowan University team has enabled engineers to redesign zinc air batteries using a combination of new materials such as carbon, cheaper iron and cobalt-based minerals.
The researchers coupled CoNiFe layered double hydroxide (LDH) with cobalt-coordinated N-doped porous carbon (Co-N-C) networks to prepare a rechargeable zinc-air battery (ZABS) composite electrode with a unique structure and synergistic effect, offering good bifunctionality and durability.
When the bifunctional air electrode was integrated into the ZABS, it showed a high peak power density of up to 228 mW?cm?2 and a low voltage gap of 0.77?V over an ultra-long lifespan of 950 hours, which is highly promising for practical use.
Dr Muhammad Rizwan Azhar, who led the project, said that the new design is very efficient, suppressing the internal resistance of the cell and keeping the cell voltage close to the theoretical voltage, resulting in high peak power density and ultra-long stability.
Dr Azhar added that rechargeable zinc air batteries are becoming increasingly attractive due to their low cost, environmental friendliness, high theoretical energy density and inherent safety. In addition to revolutionising the energy storage industry, this breakthrough contributes to building a sustainable society, reducing dependence on fossil fuels and mitigating environmental impact.
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Some companies are already laying claim to zinc air batteries
The inexpensive and earth-abundant metal material gives metal-air batteries a significant advantage over lithium-ion batteries, and the manufacturing cost of metal-air batteries may be reduced to less than 1/10 of that of lithium-ion batteries.
Extremely low material costs, high energy density, relatively simple battery design, and good safety make metal-air batteries, mainly zinc-air batteries, have a bright future.
Currently, metal-air batteries are mainly used in new energy storage and electric vehicles. For example, the U.S. company Eos Energy Storage and another U.S. company EnerSmart signed a 20 million U.S. dollar order in 2021, mainly for the installation of 10 zinc-air battery storage equipment in California, each project 3 megawatts, which can supply energy for 2,000 households.
Canada’s Zinc8 Energy Solutions also announced in 2022 that its independently developed zinc-air batteries will take the first step towards commercialisation: a new 1.5 MWh storage facility for New York City, combining its independently developed zinc-air batteries with existing solar power to power local apartment buildings.
Other foreign companies mainly engaged in the development and production of metal-air batteries are the European utility EDF, Belgium’s AZA Battery, Japan’s Sanyo and so on.
In addition, there are also a number of listed companies in China that have also made technical and industrial layouts for zinc air batteries, such as Penghui Energy, Xiongtao Stock, Desai Battery, Tsim Sha Tsui Group, and China Power.
The current commercialisation of metal-air batteries is still at an early stage, with some technologies already having the conditions for large-scale mass production, some still in the laboratory stage, and some about to be loaded on new energy vehicles on a large scale.
However, zinc-air batteries have a number of challenges that need to be addressed before they can be widely adopted. One challenge is that the air electrodes degrade over time, reducing the battery’s performance. Zinc-air batteries can also be less efficient at low temperatures.
The research is still in its early stages, but the Edith Cowan University researchers are optimistic that it could lead to the development of commercially viable zinc-air batteries for electric vehicles.
