Calcium-ion batteries: the future of battery technology?
It is hard to imagine the modern world without lithium-ion batteries. They can be found in smartphones, e-bikes, electric vehicles, cordless screwdrivers, vapes and many other devices that they supply with energy. However, lithium and other ingredients in these batteries are rare and often come from problematic sources. Many alternatives such as sodium-ion batteries do not have the necessary energy density to replace lithium-based batteries. Calcium-ion batteries (calcium batteries for short) could offer a remedy here.
At first glance, lithium is the ideal material for a rechargeable battery, as it has the strongest negative redox potential (or reduction potential) of all elements. However, the reduction potential of calcium is only slightly weaker and calcium releases 2 electrons during oxidation – in contrast to lithium, which can only release 1 electron. Therefore, a calcium battery can theoretically achieve significantly more ampere hours with a comparable cell voltage. In total, this can result in a higher energy density.
Calcium is one of the most abundant elements on earth. Among other things, it is a main component of lime, which is also ubiquitous in most of the world – for example as a deposit on the heating rods of washing machines. Many other materials that are being discussed for use in the electrolytes, cathodes and anodes of calcium batteries are also significantly cheaper and less harmful to the environment than, for example, the cobalt used in many lithium-ion batteries.
The disadvantage of calcium-ion batteries is that they still require intensive research before they are ready for mass production. Although experiments have already been carried out in the laboratory with calcium batteries that have survived up to 700 charging cycles, customers expect at least twice as many cycles. In addition, the laboratory experiments have not yet used finished batteries, but individually manufactured fibres. A variety of materials for electrodes and electrolytes are currently still being researched.
The extent to which calcium batteries will be safer than current lithium-ion batteries cannot yet be conclusively determined.
Good to know: In addition to calcium-ion batteries, lead-calcium batteries are also sometimes referred to as calcium batteries. However, these are merely improved lead-acid batteries that have been in use for a long time.
