Silicon on the road - how to make silicon-based anodes for Li-ion batteries

To transition to more use of renewable energy, we rely on the availability of cheap and reliable energy storage solutions. Here rechargeable batteries are in a unique position in terms of distribution and ease of use. Among these, the Li-ion batteries not only provide the highest energy density, but also show long-term durability and high efficiency. However, in several use cases, the typical materials currently used in Li-ion batteries unfortunately do not have all the wanted properties. We are therefore working on finding new materials that will make the batteries so good that they can help outperform petrol and diesel as preferred fuel for cars. One very promising material, which we in Norway are a world leader in extracting and making, is silicon. Silicon can be used in the battery anode as a substitute for graphite. And is potentially 10 times better! The problem is that silicon can store so much lithium that it grows to four times its original size. In addition, it reacts easily with the electrolytes commonly used in batteries. In this project, we have been working to improve the silicon materials so that the electrodes we make will withstand both the silicon growing and protect it from the electrolyte. We have used new advanced methods both to create protective layers on the silicon and to characterize the batteries we make. One method that provides very good control and leeway for creating protective layers is "atomic layer deposition" (ALD). To see how the method can best be utilized and develop methods for further characterization of the protective layer, we have used ALD to deposit, among other things, titanium dioxide on thin films of silicon. We have then characterized these using photoelectronic spectroscopy, a technique that gives us detailed information about which atoms the layer consists of and how these are bound to other atoms. We have also tested how our new electrodes work in batteries. Evaluation of this has now given us the necessary knowledge and we have tried more innovative layers of protection that, in addition to stabilizing electrolyte degradation mechanisms, are also flexible so that they are not destroyed when the silicon particles expand. Preliminary results are promising but not 100% unambiguous. Another topic we have worked on that will be very important going forward for Norway if we want to be a battery manufacturer in the future, is how best to make the structure of the electrodes so that it is optimal for materials that expand when recording lithium.

- Økt kompetanse på overflatebehandling av silisium til bruk i Li-ion batterianoder - Nye dataanalyse- og bildebehandlingsverktøy for å analysere elektroder - Forsterket samarbeid med internasjonale forskningspartnere - Forsterket samarbeid mellom norske forskningspartnere

Silicon has the potential of dramatically increasing the volumetric and gravimetric energy density of lithium ion anodes. However, due to several degradation mechanisms involved during lithiation and delithiation of silicon, silicon is typically used only as an additive (typically less than 5 wt.%) in commercial anodes. This project proposal is a competence building project focusing on developing the missing skillsets, characterisation tools and competence for enabling a proper introduction of silicon-based anodes in Li-ion batteries. The project builds on extensive silicon anode based Li-ion battery research and knowledge of the research partners, and aims to offer an arena where commercial companies trying to contribute to battery manufacturing can share pre-competitive knowledge This project aims to address several topics that have been insufficiently covered before, primarily related to lithium and electron kinetics, electrode morphology, as well as new questions based on observations in the previous projects, primarily regarding silicon deformation and surface morphology. Combining the competences of UiO, IFE and Sintef, radical new ideas related to pre-formed SEI will also be tested. In order for silicon anodes to be commercially viable, it is vital to investigate methods for partial or complete prelithiation of anodes. In the long term, silicon anodes are also relevant for Lithium Sulphur cells, so the project will include work building competence in how we can develop silicon anodes for these cell types as well.