Sodium-ion batteries based on renewable raw materials

January 30th, 2024

The demand for energy storage is growing worldwide. Lithium-ion batteries will only cover them to a limited extent due to the use of critical raw materials. The search for alternative battery technologies is therefore in full swing: A promising project called “four-volt sodium-ion battery” (4NiB) is expected to make progress here. In the project, the HIU, together with the Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) and three renowned partners, is developing sodium-ion batteries that are not only powerful and cost-efficient, but also represent an environmentally friendly alternative. It is planned that organic waste will also be used. The batteries should be tailored to electric vehicles in city traffic and stationary battery storage. The Federal Ministry of Education and Research (BMBF) is funding the project with 1.35 million euros over a period of three years under funding number 03XP0572.

In addition to the ZSW and the HIU in Ulm, the Karlsruhe Institute of Technology (KIT) and the Forschungszentrum Jülich GmbH with the Institute for Energy and Climate Research are among the project partners of the 4NIB consortium. Another partner is the Albert Ludwigs University of Freiburg with the Freiburg Materials Research Center (FMF).

4,700 gigawatt hours by 2030

In future scenarios for a sustainable energy supply, batteries are a key element and indispensable, especially for storing electricity generated from renewable sources and for electromobility. The forecast increase in the need for energy storage from 700 gigawatt hours (2022) to 4,700 gigawatt hours (2030) requires not only the production of the batteries, but also the provision of the significant amounts of raw materials required for this.

Sodium instead of lithium

A currently young but rapidly emerging technology is sodium-ion batteries. In them, sodium takes over the job of lithium. Sodium is available in large quantities and is inexpensive because it can be obtained, for example, from sodium chloride (sea salt).

The other key materials of sodium ion batteries do not contain cobalt, nickel or lithium and can therefore be produced without critical raw materials. By eliminating expensive copper foils in the battery and replacing the graphite currently used in lithium-ion batteries with alternative carbon compounds that can be obtained from renewable raw materials, not only can costs be reduced, but sustainability can also be further improved.

Such sodium-ion batteries are already being commercialized in China, so Europe needs to follow suit as quickly as possible. However, it will still be a few years before it becomes a truly mass-produced product because a lot of this new type of battery needs to be optimized.

Revolutionary anode technology: Hard carbon replaces graphite

The focus of the four-volt sodium-ion battery project is the development and optimal coordination of anodes, cathodes and electrolytes in order to realize a powerful, cost-effective and environmentally friendly sodium-ion battery. The main goal of the project is to present a high-performance cell in pouch format that achieves a specific energy of over 200 watt-hours per kilogram.

On the cathode side, the focus is on the development of high-voltage cathodes with four volts. The focus here is on the development of safe, high-voltage-stable mixed phosphates made from polyanions. Simulations are used to determine the optimal composition of the transition metals used in order to maximize the stored energy. The anode is made on the basis of hard carbon from organic waste, using preliminary products that are plentiful in Germany.

The electrolyte will be a non-aqueous liquid to which a so-called ionic liquid can be added to increase conductivity and safety. Strategies for pre-charging (pre-sodizing) such batteries should also be developed in order to maximize the energy in the battery.

About ZSW

The Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) is one of the leading institutes for applied research in the major topics of the energy transition: photovoltaics, wind energy, batteries, fuel cells, electrolysis, eFuels, circular economy, policy advice and the use of AI for process and system optimization. Together with industry, we pave the way for new technologies to enter the market. More than 300 colleagues and around 100 research and student assistants work at the ZSW locations in Stuttgart and Ulm. The ZSW operates a test field for wind energy and another test field for PV systems. The ZSW is a member of the Baden-Württemberg Innovation Alliance (innBW), an alliance of ten business-related research institutions.

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