Powering a battery storage revolution

The atomic structure of common table salt could hold the key to a revolution in energy storage. FET-Open-funded researchers are developing batteries that will extend the life of your mobile, power electric cars farther and support Europe's transition to renewables.

Today’s go-to battery technology, lithium-ion or Li-ion, is far from ideal. The technology’s shortcomings are the reason why your laptop only runs for a few hours unplugged or electric cars can only drive a few hundred kilometres on a single charge. The inherent instability of Li-ion is also the reason why some mobile phones are prone to bursting into flames.

A number of EU-funded projects, supported by the European Commission’s breakthrough innovation programme FET Open, are leading the charge to develop safer, longer-lasting and more efficient batteries. They are exploring innovative and sustainable materials and technologies to achieve the holy grail of energy storage: safe, light, power-dense, long-lasting and fast-charging batteries.

‘This is one of the major issues in battery research at the moment,’ says Maximilian Fichtner, executive director of Helmholtz Institute Ulm for Electrochemical Energy Storage in Germany. ‘Storing more energy in batteries is necessary not only to satisfy future consumer demands for smartphones, laptops and electric cars, but also to fully enable the transition to renewable energy worldwide.’

Fichtner is coordinating LIRICHFCC, a pioneering project that builds on the recent discovery by researchers at the Helmholtz Institute Ulm of an entirely new class of materials for electrochemical energy storage. These so-called Li-rich FCC materials enable a very high concentration of lithium in a dense cubic crystal formation resembling the atomic structure of rock salt, a lattice in which each atom has six equally distant neighbours.

‘There is no alternative in nature to pack atoms more densely than such a structure,’ Fichtner says. ‘We can therefore store very high amounts of lithium - and energy - in a small volume.’

Playing Jenga with lithium

The way these breakthrough crystal structures function can be compared to the popular table game Jenga. But instead of moving wooden blocks, batteries made with this face-centred cubic, or FCC, crystal geometry enable small amounts of lithium to move freely between the gaps in the structure. By doing so, the crystal can be recharged more often and exhibit much better energy capacity than existing battery cells.

‘In a classical storage material, a cubic dense structure would block the transport of the lithium ions but the opposite occurs in the case of these novel lithium-rich materials,’ Fichtner says. ‘We found that these materials can be stable and deliver high voltages with very high amounts of lithium stored in a small volume, resulting in a significant increase in energy density.’

As the first project worldwide focusing on Li-rich rock salt materials – starting with a highly efficient oxyfluoride, a compound containing metals, oxygen and fluorine – the LIRICHFCC partners are addressing important questions related to novel energy storage mechanisms and how lithium interacts with different elemental compositions.

‘The beauty of this new class of materials is that they open up many new possibilities, including the potential to use more abundant and less toxic elements than those present in Li-ion batteries at the moment,’ Fichtner says. ‘Though it will take a couple of years for the technology to mature and be ready to scale up, we expect our work to lead to important commercial applications. This is fascinating science that could have an enormous economic impact.’

Indeed, in addition to the practical limitations of current Li-ion technology, industry forecasts warn of a significant shortage of lithium in the near future. Lithium is one of the rarest elements in the Earth’s crust and demand for it is continuing to rise, leading European researchers to seek alternative materials and compounds, which, if successful, could have a major long-term impact on the evolution of energy storage.

Improving battery economics

In the SALBAGE project, also funded under the FET Open programme, a team led by Spanish SME Albufera Energy Storage is developing an aluminium sulphur battery as a viable and economic alternative to Li-ion.

By employing innovative chemistry and manufacturing technology, the researchers aim to achieve a very energy-dense battery that can be manufactured at 60 % lower cost than a comparable Li-ion. Notably, the SALBAGE team’s approach will enable novel flexible and mouldable battery designs, allowing unique energy storage solutions in almost any shape that would be suitable for a wide range of applications in consumer electronics and transport.

CARBAT, another project coordinated in Spain by research institute ICMAB-CSIC, is looking to common calcium as an alternative for rechargeable batteries. The fifth most abundant element in the Earth’s crust, calcium could offer a viable alternative to lithium-based cells. Though less energy dense than other emerging materials and technologies, it would offer an efficient and low-cost way to fill a gap in the energy storage market without relying on rare and expensive materials.

‘While the cost of the totally dominant Li-ion battery technology has fallen by an impressive 50 % in the last decade, Li-ions are slowly reaching their fundamental limits in terms of energy density,’ the CARBAT team says. ‘Furthermore, the risk of limited lithium supply and associated cost increases cannot be ignored. Therefore, new sustainable battery chemistries must be developed.’