ENERGIX-Stort program energi

The importance of battery technology in our energy systems have tremendously increased over the last decade. Now utilized in computers and cellphones; to electric vehicles even houses the batteries are required for storage and delivery of clean renewable electricity. In a future society without fossil fuels, energy storage will become the key to flexibility in the energy supply. The rapid increase in use of batteries demands new technologies and innovations. In the present project we investigated the pathways which will allow to fabricate better rechargeable Li-ion batteries. IFE's battery research focuses on developing silicon as a material for storing lithium atoms within Li-ion batteries. Silicon can store up to ten times the amount of electric energy compared to the standard electrode material of today - graphite. Battery scientists worldwide agree that silicon will be a part of the batteries of the future while some battery producers are already using small amounts silicon in the graphite electrode to increase their capacity. Despite the promising properties of silicon as anode material in Li-ion batteries it suffers from several problems limiting its wide deployment in the modern battery technologies. Specifically, an ability of silicon to accommodate a large amount of lithium comes with a price ? enormous expansion of the material. Removal of lithium as part of cycling of the battery leads to respective loss of volume. To accommodate such volume changes which can reach 400%, a concept of using silicon nanoparticles as active material was introduced. However, even the nanoparticles are exposed to a tremendous mechanical stress, and after a few cycles of introduction and removal of lithium the nanoparticles crack and fracture. As a result, the battery loses its high capacity. Better understanding of the chemistry and pathways for the preparation of the nanoparticles can solve the problem: the present project develops methods for understanding the mechanisms and underlying chemistry which controls the lifetime of the silicon nanoparticles in the battery. Over the years IFE has developed its own technology for preparation of silicon nanoparticles which allows to tailor the size and morphology of nanoparticles. That allows silicon to better withstand the uptake of lithium and thereby enable the fabrication of Li-ion batteries that retain their high capacity for many cycles. Over the course of the project, several master and summer students, one post doc, and more than 10 researchers and engineers have been involved in the development of the silicon nanoparticles chemistry and understanding their behavior as anode materials for Li-ion batteries. Such efforts led to the development of the silicon nanoparticles with extended lifetime. In addition, the group has evaluated various methodologies for the particle treatment and methods for preparation. The research group has also established connections to several relevant international groups. The presentations at conferences and anticipated publications in peer-reviewed journals provided an international recognition of the conducted work. Some of the highlights of the project are listed below: - Results presented at multiple international conferences (including IMLB and MRS) and public outreach through interview on Dagsrevyen and an article in Romerikes Blad - Synthesis of silicon nanoparticles of different size and morphology has been demonstrated. The development led to extension of the silicon lifetime and functionality in Li-ion batteries. - First experiments on small angle neutron scattering of Si particles and cell were performed and setup for in operando studies developed and tested. The achievements of the present project highlighted the importance of the research in the area of silicon-based materials for their application in Li-ion batteries as well as demonstrated promising routes for the future developments in the area. Such results support Norway's strong position and competence within silicon materials as well as establishing an international recognition of the Norwegian science.

Silicon can greatly enhance the energy storage capacity in Li-ion batteries. But how do we make the needed silicon materials in the most efficient way? What is the ideal material like, how does it react to further processing, how does it change during cycling, and how can we find a balance between efficient, cheap production and high durability? These are the questions to be answered by this project: Siproco Fobeliba. The project is cross-disciplinary: Combining competence from three different departments at Institute for Energy Technology, we will be able to investigate and tailor the silicon materials from the production stage to electrode preparation and cycling. In the production process and during final operation, we will make use of advanced material characterization methods available only at IFE in Norway to better understand how the silicon material behaves during the different steps. This information will provide input to tailor the production process for the best particles with regards to battery performance and production efficiency.