Silicon anodes deposited on various current collectors for the development of high-density lithium-ion cells for the automotive applications

F.Farmakis, M. Hangen, P. Fanz, A. Kovacs, S. Schiestel, P. Selinis, S. Matziris, N., C.Elmasides
2015. 7th German Symposium Advanced Battery Development for Automotive and Utility Applications and their Electric Power Grid, Aachen, April 2015

Abstract: It is well known that silicon presents one of the most important anode materials for the improvement of lithium-­‐ion cells in terms of energy density. Indeed, silicon’s high theoretical specific capacity to lithium (more than 3800 mAh/g at room temperature), environmental friendliness, low potential compared to lithium and material abundance turns silicon to a strong candidate for the replacement of carbon-­‐based anodes. However, one of the main drawbacks of silicon’s application to the lithium-­‐ion technology is its poor cycling stability, mainly due to silicon’s huge volume change (around 400%) during lithiation and delithiation that leads to high internal mechanical stress. Therefore, in order to improve silicon’s stability we have to take into account its adhesion properties to the current collector.

In this work, we present the experimental results of half-­‐cells with silicon anodes that have been deposited by DC sputtering technique on various substrates that can be used as current collectors such as copper foil, carbon fibers, special treated copper foils, electro dag coated and CNT coated copper foil and titanium foil. From those results, it becomes obvious that the adhesion properties of silicon to the current collector play an immense role to the specific capacity of the anode and most particularly to its stability over cycling.

With the proper combinations of current collector and silicon material, anodes with stable high capacity over 3-4 decades when cycled at 0.6 mA/cm2 that exhibit more than 1.5 mAh/cm2 have been achieved. We believe that these silicon anodes can be efficiently associated with commercial cathodes and provide stable full cells with high energy density.