Silicon alloys for improved lithium-ion batteries

Battery researchers and producers are continuously on the lookout for new materials that can increase the amount of energy stored in batteries. For each step in the development, new doors are opening for ever more demanding applications. The benefit can be large for those that are driving this innovation, and for those that manage to take the next step in using batteries in new and growing markets. In the SAIL project we are working on a material that can put IFE in such a position. The battery research at IFE focuses on developing silicon as a material for the negative electrode in lithium-ion batteries. Silicon can in fact store up to ten times as much charge as the material that is used in the negative electrode today, namely graphite. Battery researchers generally agree that silicon is a part of tomorrow?s batteries, and some producers have already started using a few percent of silicon mixed in the graphite electrode. Unfortunately, several problems occur when we fill silicon with many lithium-ions, and the result is that the material cracks and breaks down. At IFE, we have developed a new silicon-based material that intends to solve this problem, amorphous silicon-rich silicon nitride (SiNx). This material has previously been tested in thin film electrodes, with very promising results. In SAIL we continue the development of this material towards more commercially relevant particle-based electrodes. In this project, nanoparticles of SiNx have been produced in a reactor at IFE, and batteries with these materials have been built and tested. Controllable production of SiNx with different values of 'x' has been achieved, and we have developed a better understanding of how changing 'x' affects the performance of the material, enabling us to make suitable compositions depending on what an application needs. The produced particles show very little degradation when compared with pure silicon particles with different degradation pathways. To better understand why this material works as well as it does, much effort has been put towards characterization of the electrodes, in order to improve both lifetime and the energy storage capacity. In this endeavor, the university partners provide invaluable insight into the ageing of the material on particle level through advanced electron microscopy techniques. The results of this work has been very promising, and shows that the excellent performance that this material exhibited in thin film form is transferable to commercially relevant electrodes. Results from the SAIL project have been presented at major conferences and been published in several academic research articles. IFE has attained a lot of attention around the SiNx material, both from interested parties in industry and from national and international media. The development of the SiNx material is set to continue in several recently started KSP projects, and the work with upscaling and commercialization has already commenced in the Forny2020 project SiliconX.

De viktigste virkningene og effektene knyttet til SAIL prosjektet er forståelse av SiNx-materialet som et mulig anodematerial til lithium-ionebatteriet. Dette arbeidet har blitt oppsummert i flertallige vitenskapelige publikasjoner og patenter. I tillegg fikk både materialet og prosjektet internasjonal oppmerksomhet for potensialet til det nye anodematerialet som har blitt fremstilt av IFE. Forskningsprosjektet har banet vei for videre oppskalering og kommersialisering av materialet, noe som har blitt videreført i andre prosjekter knyttet til SAIL.

This project aims to develop new advanced silicon alloys for high-capacity and long-lifetime lithium-ion batteries (LIB). Using strategic funding, and based on learnings from previous silicon battery projects, IFE has developed a new silicon alloy which shows very promising behavior in initial testing. The material combines a high and tunable capacity with excellent cycling stability, and can be produced with a mass-production compatible method. The material's full potential is not yet revealed, and this project is to dive into the fundamental questions, creating a scientific foundation for future development. Topics such as understanding the mechanism of operation, finding the optimal stoichiometry, expansion on lithiation, and methods for prelithiation will be investigated. Silicon alloy nanopowders will be produced in the IFE silicon production laboratory, where optimal composition, size distribution and yield can be controlled. The powders will be processed into battery electrodes at the battery laboratories at IFE, using methods and know-how developed from years of experience from other silicon anode projects. Performance will be characterized through electrochemical testing, including a detailed study of kinetics and loss mechanisms. An important focus of this project will be the characterization of the newly produced material and investigation of the morphology and composition through advanced electron microscopy. Post cycling characterization together with advanced in-situ characterization, conducted together with the partners at the University of Oslo and the University of Cambridge, will provide further understanding of the conversion reaction of the silicon alloy and identify the dominant degradation mechanisms. By enabling better batteries with higher capacity and longer lifetime, it is expected that the impact of the project will support the energy transition in the Norwegian economy, and fuel the global mission for reduction of climate gas emissions.