Fig1: Lithium-sulfur roadmap and LISA objective considering >10 Ah pouch cell format and at least >400 Wh kg-1, adapted from DOI 10.1002/ente.202000694.
Towards a new generation of lithium-based batteries Recent years have seen rapid growth in the number of electric vehicles on Europe’s roads, yet the lithium-ion batteries currently used in them have some significant limitations. We spoke to Dr Christophe Aucher about the LISA project’s work in developing lithium-sulfur batteries, which could represent an attractive and more cost-effective alternative to lithium-ion. The electric vehicles
currently on the road typically use lithium-ion (Li-ion) batteries, yet this technology has some significant limitations from the perspective of European industry, in terms of both performance and logistical considerations. The critical raw materials are not easily available on the continent, so manufacturers are highly dependent on external suppliers. “Li-ion batteries are not a European technology. We have to buy in materials like lithium, cobalt and nickel from outside,” says Dr Christophe Aucher, an energy storage specialist based at the Leitat Technological Centre in Barcelona. As the technical coordinator of the LISA project, Dr Aucher is working to develop lithium-sulfur (LiS) batteries, which could represent an attractive alternative to Li-ion. “We are aiming to make LiS cells at a commercially relevant level, and with better performance than Li-ion. Beyond
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that, we want to demonstrate that they are ready to use,” he outlines.
LiS batteries This approach involves using sulfur as an active material, which is abundantly available as a bi-product from the oil and chemical industries. In theory, LiS batteries should have a higher specific energy than Li-ion batteries, yet in practice there are still some hurdles to overcome before they can be more widely applied. “We are not at a high level of manufacturing LiS batteries in Europe compared to Li-ion. We haven’t yet demonstrated effective technology at a high level of production,” acknowledges Dr Aucher. This is one of the issues the project is working to address, with researchers in LISA working to develop different components for LiS batteries, explore means of manufacturing them more efficiently and ultimately bring
them closer to the market. “The big limitation for LiS is the number of charge-discharge cycles. The more charge-discharge cycles we can do, the more possible applications for LiS batteries we can look into,” says Dr Aucher. There have been a number of pilot studies over the last decade into using LiS batteries in certain types of autonomous drones and satellites, yet the aim in the project is to bring them closer to use in electric vehicles and other more everyday applications. It is possible to increase the number of chargedischarge cycles of LiS batteries and extend their effective life, but this will reduce their energy density. “Li-ion batteries have an energy density of somewhere between 250300 watt-hours per kilogram (Wh/kg). We can achieve superior energy density about 400 Wh/kg but the number of cycles is lower,” explains Dr Aucher. The key is to achieve high volumetric energy density while also
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increasing the number of charge-discharge cycles. “We’re using a process called coextrusion for making the active material of the cathode. This allows us to reach a high volumetric energy density for LiS batteries,” says Dr Aucher. This is a central issue in the battery industry, with researchers seeking to store as much energy as possible within a specific cell volume while also reducing their overall weight. One of the LISA partners is also developing a solvent-free method to make dry film electrodes, which Dr Aucher says is another important dimension of the project’s research. “Here we are replacing the traditional methods with aqueous or dry film cathode processing. We are no longer using solvents, which are toxic and can be difficult to recycle. We have demonstrated this in the project,” he outlines. The ability to recycle lithium from the battery is a prominent consideration; a LiS battery does not include much valuable material, so the priority is to recover the lithium. “The anode is pure lithium. One of our partners has demonstrated that more than 90 percent of the lithium in this technology can be retrieved,” says Dr Aucher. The project’s overall agenda including not just developing components and preparing the electronics, but also evaluating the safety of LiS batteries. This is a critical issue in terms
LISA Lithium sulphur for SAfe road electrification Project Objectives
There is a need for new batteries that enable EVs with higher driving range, higher safety, and faster charging at lower cost. Lithium sulfur is a promising alternative to Li-ion, free of cobalt and nickel, with higher theoretical capacity, and energy. LISA is incorporating manufacturability concepts and new materials, components, cells transferable to other lithium-anode based technologies.
Project Funding Fig2: Scheme of Lithium-sulfur cell charge and discharge mechanism.
ion batteries relatively mature in comparison to LiS, more resources are typically devoted to their development in Europe, but Dr Aucher hopes to encourage further investment in LiS. “It’s really difficult to produce Li-ion batteries in Europe at the same level as they do in China, and as cost-effectively,” he says. “A potential solution to this is to propose an alternative like LiS. At the moment LiS batteries in Europe are at around Technology Readiness Level (TRL) 4, while some of the components are at a higher level. The idea is to work towards new batteries that could be a game-changer in the future.”
We are aiming to make lithium-sulfur cells at a commercially relevant level, and with better performance than lithium-ion. Beyond that, we want to demonstrate that they are ready to use. of their potential wider adoption in electric vehicles. “We need to pilot the technology, to make it charge and discharge in a proper way, and to improve safety,” says Dr Aucher. While the technology is not yet fully mature, Dr Aucher says a great deal of progress has been made over the course of the project. “The feasibility of producing the components has been demonstrated, including the cathode, separator and the solid-state electrolytes. We have already fulfilled some of our objectives in the project, and some of the electronics are available,” he outlines. “We have also demonstrated this technology at relevant dimensions, beyond the laboratory scale.” A number of the techniques and components developed in the project can also be applied on Li-ion batteries, including the extrusion of the active material, the dry film cathode manufacturing and the pulsed laser deposition (PLD) techniques for solid state, non-flammable electrolytes. With Li-
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Sustainability This research represents an important contribution to the wider goal of building manufacturing capability in Europe, and potentially paving the way for further development. In terms of LiS batteries, it remains difficult to manufacture them at commercial scale, in large part because of market realities. “In theory LiS batteries would be a game-changer, but huge investments are required to develop something that is useable and ready for the market,” acknowledges Dr Aucher. With demand for batteries likely to increase in future, Dr Aucher believes that the technology holds great potential, for example in aerospace or even in flying taxis, an idea which has been mooted as a way of addressing urban transport issues. “In future batteries will be needed much more widely, and LiS could be an attractive option,” he says. “What we lack currently is a company to commercialise it, which would require a lot of investment.”
These projects have received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreements Nº 814471. These results reflect the author’s view and the Commission is not responsible for any use that may be made of the information it contains.
Project Partners
https://www.lisaproject.eu/lisa-partners/
Contact Details
Project Coordinator, Christophe Aucher, PhD Area Manager Energy Storage Area Energy & Engineering Department T: +(+34) 93 788 23 00 Ext. 2444 E: caucher@leitat.org W: http://www.lisaproject.eu W: www.leitat.org
Christophe Aucher, PhD
Christophe Aucher has 15 years background in Energy Storage. He is leading the Energy Storage team that is currently involved in research and industrial projects for electrical mobility, stationary, printed electronic and batteries recycling.
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