Electrical energy storage is a critical component in green energy transition from fossil fuels to renewable energy. Among a variety of energy storage solutions, Li-ion-battery (LiB) represents the most developed and reliable technology, which demonstrates high energy density and long-term durability. The deployment for LiB has been surging due to the growing market of electrical vehicles, consumer electronics and stationary storage. One of the LiB market needs is the increasing demand for higher energy density of LiB.
A great deal of effort has been made to improve the energy density of LiBs while maintaining long-term performance in academy and industry. While the energy density of cathode materials has almost reached the limit, finding the alternative anode candidate to the currently utilized graphite appears to be potentially the most feasible and economical approach towards higher energy density. Silicon was found to be an alternative anode material due to its abundancy, low price and a remarkable storage capacity for the Li ions, which could improve the battery capacity by almost an order of magnitude. However, substantial structural/morphological changes during charge and discharge cycles results in fast degradation of the batteries fabricated with Si-anodes.
The primary aim of SIGNAL was to address the issue with Si as anode material through a scalable production process that produces engineered Si/graphene at nano scale.
Through testing different silicon materials, we have, among other things, found out how large the silicon particles should be in order for them to be most easily covered with CealTech's graphene. Various combinations of silicon, graphene-protected silicon and graphite have been tested as electrode materials in so-called half-cells, of which a promising combination has progressed to testing together with a cathode material in full-cells.
Si-based anodes is viewed as the next step for Li-ion batteries. However, the use of Si in LIB’s anodes is hindered by the severe degradation of Si as active material. Nanostructuring the Si particles with carbon materials such as graphene was shown as a promising mitigation strategy but only at the research level obtained at high cost. The planned outcome of the project is the development of scalable procedures for the preparation of Si-based anodes engineered with graphene. The resulting product will deliver the structural stability needed for the use of Si in Li-ion batteries. The results obtained in SIGNAL project have demonstrated potential for further improvement in performance.
Continuation of the effort could lead to the delivery of such materials to the market which will substantially boost the materials industry of Norway, potentially making it the largest European supplier of anode materials for the next generation of Li-ion batteries. Such batteries will have a tremendous impact not only on the European economy, but also will assist in implementation of green energy for the society.
The present project aims to raise a new material based on a combination of silicon nanoparticles and graphene as a future anode composition for Li-ion batteries (LIBs) to a level where it can meet all the industrial requirements necessary for the successful deployment of this technology. That includes the development of the methods necessary for up-scaling the material’s synthesis/production, optimization of materials and anode properties as well as incorporation of the final nanostructured silicon/ graphene composite into industrially relevant prototype LIBs. Manufacturing perspectives such as possibility of up-scaling, assessment of material’s availability, price competitiveness and readiness for use with emerging battery technologies will be also assessed through the project.
The project will evaluate a scalable method for the preparation of silicon/graphene composites by growth of the graphene on Si nanoparticles. The prepared material in different stages of production will be subjected to extensive structural and chemical characterization in order to evaluate material morphology, coverage of coatings, quality and reproducibility, using techniques such as XRD, Raman, SEM, TEM and XPS. The material's performance as anode material will be determined by different electrochemical test procedures, including galvanostatic cycling and rate performance testing in half and full cells. Data analysis tools, like differential capacity analysis, will be used in conjunction with post-mortem analysis of materials to elucidate degradation pathways and stabilization mechanisms. The project will be finalized by verification through fabrication of pouch full celll using NMC622 as a cathode.