Next generation of lithium ion batteries

Lithium Ion Batteries currently are the fastest growing battery technology, and dominate global markets in consumer electronics and electric vehicles. Silicon has recently started to replace the carbon used in most battery anodes, allowing capacity increases of more than 50%, and this trend is expected to continue. In the Natbatt project we have significantly improved how we make electrodes based on Si particles, utilising non-intrusive mixing methods and by using screen printing of the electrode material on the current collectors. This has made our experiments more reproducible, which in turn has allowed us to extract more trustable knowledge from our characterization experiments. We have seen how oxide layers on the silicon particles affect the life of the electrodes and how electrolyte additives are consumed during cycling. Coupled with an improved method of making cross-sections of electrodes, we have seen how different biopolymers affect morphology and the life of silicon-based anodes.

Li-ion batteries are a commercially interesting battery technology, with fast market growth. Introducing Silicon is expected to be core of the next generation of Li-ion anodes, allowing higher battery capacity. Silicon expands during lithiation, leading to fast degradation, and limiting industrial use of silicon anodes. Binder modifications are a very promising path towards improved cyclability of silicon anodes. Biopolymers like CMC and alginates have been demonstrated to be promising binder candidates, with the additional benefit that they are water soluble, giving cost and HSE benefits in production. The current project focuses on the interaction between the silicon and the binder, both during the production process and during cycling. The project aims not only to test different parameter spaces, but to document the stepwise influence of the parameters, as the components traverse the production process. Silicon particle surfaces and binder functional groups influence slurry rheology. Slurry rheology influences electrode porosity and stability. Electrode porosity influences kinetics and capacity, and capacity influences cyclability. In order to differentiate direct effects of the silicon from secondary effects in later production steps, an increased understanding and characterization of the individual process steps is needed. Dynatec will, in collaboration with IFE, produce Silicon nanoparticles with different surface morphologies, surface charge and size distribution. Borregaard will provide biopolymers of a wide variety, most of which have not been reported used in the literature. IFE will use these powders to make slurries, electrodes and full batteries, and to test the batteries for kinetics, capacity and cyclability. SINTEF will provide advanced characterization of powders and electrodes and some post mortem analysis of batteries. CEA will provide competence on electrolytes and electrolyte additives, also including post mortem characterization.