Lithium-ion batteries are now an essential source of energy in everything from electric cars to medical implants. This type of battery in not without disadvantages though. That is why the CSEM Battery Innovation Hub is developing and testing new materials and manufacturing processes that will provide safer and more powerful batteries.
Picture: CSEM
The current generation of lithium-ion batteries generally use a graphite anode (the negative electrode) and liquid electrolyte. When the battery is in operation, the electrolyte enables the charge to flow, in the form of lithium ions, between the anode and the cathode (the positive electrode). Even with further optimisation, this design is likely to reach the limits of its physical energy-storage capacity in the next few years. Moreover, lithium-ion batteries with liquid electrolytes entail a risk of leakage – and can even ignite if they overheat.
A new generation of so-called ‘solid-state’ batteries promises to remedy this situation. The CSEM Battery Innovation Hub is developing batteries with high-performance lithium-metal anodes and a solid electrolyte made from a polymer material. These batteries can store twice as much energy as their graphite-anode counterparts and offer a high level of safety.
The major problem facing efforts to improve the performance of batteries with lithium-metal anodes is that the metal is highly reactive and forms an irregular surface layer in conventional manufacturing processes, on which additional metal might be deposited during operation, negatively affecting the storage capacity and service life of the battery. CSEM has therefore adopted physical vapour deposition (PVD), a technology that is often used to process metal parts in the watch industry. CSEM itself is a research and development centre with roots in this very same industry. PVD can be used to apply thin, uniform and highly pure layers of lithium metal to high-performance anodes in a vacuum, along with a protective film that prevents unwanted additional metal deposits. Andrea Ingenito, co-director of the Battery Innovation Hub, is firmly convinced that “thin-film technology is a crucial step towards the next generation of batteries”.
The second key step is to use these new anodes in a solid-state battery. Alongside the aforementioned safety benefits, this type of battery also promises to be cheaper and more energy-efficient to produce. CSEM uses in-situ polymerisation, in which a liquid raw material is introduced between the battery electrodes and subsequently polymerises to form a solid electrolyte. The contact surfaces between the battery elements that this creates enable a very good flow of charge inside the battery, which in turn has a positive effect on performance and service life. Furthermore, CSEM is using its expertise in material development to improve the properties of the polymer electrolytes, so that solid-state batteries can also deliver high performance at room temperature. The high operating temperatures or pressures required by other solid-state batteries make it difficult to bring them onto the market.
A new generation of solid-state lithium-metal batteries would primarily benefit the electric vehicle market. These vehicles could be improved in terms of range, costs, charging times and service life to such an extent that they would at least match, or even surpass, today’s combustion-engine vehicles. Reducing the size and weight of future lithium batteries while also increasing their safety would be beneficial for niche applications, such as medical implants.
Andrea Ingenito finishes by pointing out that it will be several years before mass-produced solid-state batteries appear on the market. However, he does see an exciting and promising future for this rapidly developing field, which decision-makers should follow closely. “The new materials and manufacturing processes,” he says, “offer an opportunity to rebuild the European battery industry.”
