The International Energy Agency (IEA) has stated on several occasions that in the next 25 years we will experience unprecedented growth in the demand for batteries, driven precisely by the popularization of the use of renewable energies and electric cars, among other trends.

To get an idea of the expected demand for these energy storage systems in the medium term, in 2019 the demand for batteries for the electric car accounted for a total of 80 GWh. Well, this international body estimates that the demand for batteries for the electric car will exceed 3,000 GWh (40 times higher) by 2030, and will reach 9,000 GWh (120 times more than what is demanded today) within 15 years.

This spectacular data is directly linked to the coming wave of renewables (expected to increase by 250 times, reaching 2,000 GWh by 2040), but, as might be expected, the main source of battery demand is the sector associated to the electric vehicle.

The fact that the demand for energy for stationary storage will grow the most, together with the complexities associated to the industrialization of lithium-ion batteries, makes it necessary to develop new battery technologies to complement the hegemonic lithium-ion batteries.

For this purpose, sodium-ion batteries are presented as a technology as valid as that based on lithium to supply the energy demand of such a demanding area as stationary storage (electric vehicle charging points, self-consumption, lighting, renewable energies...).

In order to understand the perfect harmony between the two technologies, it is important to first summarize the main strengths of sodium-ion batteries. Once these strengths are known, it will be easier to determine what challenges the industry will have to face and, in particular, how to overcome them.

STRENGTHS OF SODIUM-ION BATTERIES

1) Both lithium (Li) and sodium (Na) belong, within the periodic table, to the same group of alkaline metals. This means that they have very similar chemical, technological and performance properties, so that, in order to start industrializing the manufacture of this type of batteries, the infrastructures used for the production of lithium-ion batteries could be used. Thus, by maximizing the industrial production of this technology, the corresponding economies of scale would be achieved, minimizing to the maximum the great obstacle that the cost of industrialization represents.

2) The materials from which lithium-ion batteries are made are classified as critical. One of the main objectives set by Europe for sustainable development is the reduction in the use of this type of critical raw materials (CRM). Apart from being increasingly scarce, these raw materials are found in underdeveloped countries or countries in conflict, which use this market as a means of financing and enrichment. Sodium-ion batteries, on the other hand, use sustainable materials, low cost and abundant in nature.

3) Sodium-ion batteries, due to the chemical properties of their constituent elements, provide a low-cost, safe and, as we have already said, sustainable energy storage system. All these attributes make it, for example, a very suitable technology for the storage of renewable energies. The properties of lithium-ion batteries, for their part, are ideal for electric vehicles (largely thanks to their high energy density).

One of the main challenges facing sodium batteries is the need to develop the market for components. Today, only a few manufacturers - 2 or 3 suppliers worldwide - are in charge of transforming this raw material and giving it the right format for the battery industry. Currently, the European company E-lyte is one of the main players involved in sodium processing in Europe. However, it is sourced from Asian markets. Therefore, for the industrialization of this technology in Europe, it is necessary to have more and better European allies producing "Battery Grade" sodium.

What is clear from this is that, given the expected high demand for energy, the more alternatives there are on the market, the easier it is for them to complement each other to meet energy needs.

Therefore, although promising announcements have been made in recent months by international companies that are already working on technologies associated with sodium-ion batteries, further research is still needed to make them fully complementary to lithium-ion-based technologies. In this way, very competitive solutions capable of meeting the growing market demand in the different applications would be achieved.

As can be seen in the image below, the complementarity between the two technologies is promising. The development of sodium-ion technologies and their industrialization suggests that sodium batteries could reach where lithium batteries cannot, and vice versa.

SCIENTIFIC ACTIVITY: KEY TO MEETING THE CHALLENGE

Fortunately, the growing interest emerging from the markets for this type of technology is translating directly into the evolution of research activity for this purpose.

And despite the fact that, over the last 20 years, more than 50% of patented research activity in the field of sodium-ion batteries has been registered in China (52.71%), followed by Japan (16.39%) and the USA (12.7%), Europe is also starting to move in this direction in pursuit of the goal of becoming progressively more independent of the Asian market.

Internationally, the role played in this field by the Asian giant CATL is particularly noteworthy. The announcement of a second generation of sodium-ion batteries, to be developed at its plants in China and Germany, was a milestone both for the company and for the industry in general. This second generation represents a real technological revolution, as it is expected to achieve an energy density of 200 kWh/kg, which means that, for the first time, it will really approach the values of a lithium-ion battery. In the meantime, the company is working on the production of first-generation batteries with an energy density of 160 kWh/kg, which are expected to start being commercialized next year.

However, in the race towards the energy transition, the role of smaller players also becomes crucial. Thanks to their scientific activity and their firm commitment to electrification, important advances are being made in this field. This is the case, for example, of the company Natron Energy (USA) or the research center CIC energiGUNE.

On the one hand, Natron Energy presents a technological project, with a very ambitious growth, based on the development of batteries for telecommunications and data centers. However, the company is already considering expanding its applications to a third stage in the future: electric mobility. The particularity of these batteries is the use of aqueous electrolyte, providing a lower energy density, but allowing higher power densities with high cycling stability, as well as being safer and more sustainable.

Last May, they reached an agreement with the world leader in advanced low-voltage battery technologies, Clarios International Inc. for the mass production of sodium-ion batteries in 2023. This strategic move is an example of how the sodium-ion battery market is moving towards industrialization. Moreover, although in 2021 the American company already started to commercialize a first product (BlueTray 4000), this time it is a first contact with the mass scaling of sodium-ion batteries, taking advantage, as we have mentioned, of machinery that was previously used to assemble lithium-ion batteries to reduce costs and speed up their insertion in the market.

At CIC energiGUNE, aware of the importance of responding to market needs, we offer the best energy storage solutions to improve the competitiveness of the industry. Our team of researchers, fully experienced in this technology (from the most fundamental level to large-scale proof of concept), seek to develop, design and optimize the properties of the materials in terms that will determine the performance of sodium-ion batteries, such as energy density, power or cyclability, among others. All this with maxims such as sustainability, recycling and circular economy to meet future challenges, while meeting current challenges.

This is reflected in the two projects that CIC energiGUNE is already working on to continue researching the qualities and performance of this technology: TOPSIDES and NIB-MOVE. The first one, included in the R&D&I Program "Challenges of Society" of the State Research Agency, is focused on developing a solid-state metal-sodium battery, with high-voltage cathodes and alternative "green" anodes obtained from PET plastic waste.

For its part, NIB-MOVE - funded by the Ministry of Science and Innovation of Spain, as part of the "R&D&I Challenges" program - aims to identify materials for the next generation of electrochemical energy storage technologies based on sodium.

This commitment of companies and research centers such as CIC energiGUNE to sodium-ion batteries is also reflected in the market´s own vision of this technology. Moreover, in a recent survey carried out on CIC energiGUNE´s social networks, it can be seen how more than 60% of the users who responded to it trust in sodium as the most promising technology to complement the hegemonic lithium.

A forecast that is shared by consulting firms such as Deloitte, which, in one of its latest reports, predicts a growth in market demand for sodium-ion batteries of more than 671% by 2025. This would represent up to 75% of the market share related to stationary applications.