Influence of different anode active materials and blends on the performance and fast-charging capability of lithium-ion battery cells

To further extent the driving range of battery electric vehicles, an increase of the energy density of lithium-ion battery cells is necessary. One way to increase the energy density is the use of high-capacity electrodes. The challenges for this kind of electrodes are transport limitations, like the long lithium-ion diffusion path to the layers near the substrate of the electrode, leading to performance degradation during cycling. To get a better understanding on how the material selection influences the battery cell performance, various active materials (graphite, silicon, and hard carbon) are investigated, both, pure and in blends and the relation between material, structure and performance is studied. On material level pure silicon active material has a very high electric resistance compared to carbon-based materials. Nevertheless, on electrode level, the high gravimetric energy density, and the round-shaped particle morphology of silicon result into a lower tortuosity and layer thickness, hence, ionic resistance of the electrode. With respect to cell performance, the ionic resistance seems to have a greater impact compared to the charge-transfer and electric resistance. Therefore, silicon-based electrodes show the best performance.