Application examples: Energy materials

Silicon (Si) as an anode material is a key component for increasing the energy density of nowadays Lithium-Ion Batteries (LIB). Graphite is the most commonly used anode material in commercial LIB. The drawback of graphite is its lowest specific storage capacity of approximately 370 mAhg^-1. In contrast, Si theoretically possesses, with the exception of lithium, the highest specific capacity among anode materials at room temperature (approximately 4200 mAhg^-1). Challenges arise in using Si due to the significant volume change of the host material during the lithiation process (up to approximately 400%). Additionally, there is chemical instability at the anodic interface with the electrolyte, the so-called Solid-Electrolyte Interface (SEI), over cycling.

Our battery activities focus on developing of high-capacity silicon anode materials using a dry process combining the use of sputtering and Flash Lamp Annealing (FLA). This approach enables a considerable reduction of the volume change of the Si after lithiation and an improved battery performance in full-cell configurations, e.g. using a cathode material of lithium iron phosphate and a liquid electrolyte of LiPF₆ (in ethylene carbonate and dimethyl carbonate solution). Such coin cells achieve a surface capacity of up to 2 mAh/cm², more than 100 cycles, and a stable coulombic efficiency of up to 98%.