A team of researchers from the Institute of Materials Science of Barcelona (ICMAB-CSIC) has made a huge step towards the production of rechargeable calcium batteries: for the first time, calcium has been extracted electrochemically of a metal oxide in a partially reversible way.
This breakthrough demonstrates that this oxide could be used as cathode (positive electrode) in future rechargeable calcium batteries. The results, published in the journal Dalton Transactions, represent a further step towards the development of rechargeable calcium batteries, a more economical and with more energy density alternative than the current most common Li-ion batteries. The study was carried out in collaboration with Toyota Motor Europe, which shares the patent.
This finding can help solve one of the main problems to produce rechargeable calcium batteries, which consists in finding cathodes that can extract and incorporate calcium ions in a reversible way, explains the ICMAB researcher M. Rosa Palacín, leader of the study. In this case a calcium-cobalt oxide has been used. The researchers have observed how its structure changed once the calcium was electrochemically extracted. This discovery is added to the one that Palacín's team made in 2016, when they showed that metallic calcium can be a good anode (negative electrode) for batteries.
In order to bring the calcium batteries to the market, the cathode's reversibility must be increased and all the battery's components optimized. At the moment, there is no prototype of rechargeable calcium battery. However, all the technological development of lithium batteries, which have been on the market for nearly 30 years, could serve to boost calcium batteries, once the first prototype is out.
Reference article: Electrochemical calcium extraction from 1D-Ca3Co2O6. Deyana Tchitchekova, Carlos Frontera, Alexandre Ponrouch, Christopher Krich, Fanny Bardé and M. Rosa Palacín. Dalton Transactions. July 2018. DOI: 10.1039/C8DT01754A
Figure 1: Calcium rechargeable battery (metallic calcium anode, electrolyte, calcium-cobalt oxide cathode)
Figure 2: Initial structure of the calcium-cobalt structure (Ca3Co2O6) and final structure, once the calcium has been extracted (Ca3-yCo2O6).
Press release in Catalan, Spanish and English here.