Silicon anode processing using flash lamp annealing for lithium ion batteries

In the near future, silicon will play a key role as anode material for rechargeable lithium ion batteries (LIBs). It shows a low discharge potential and an extremely high specific theoretical capacity of about 4200 mAhg-1 in comparison to that of graphite with a theoretical capacity of 370 mAhg-1. However, the intrinsic volume change of Si particles of more than 400 % during the lithiation and delithiation processes hinders the Si to fully replace the conventional graphite in commercial LIBs. Using planar flash-lamp annealing (FLA) with annealing times in the sub-second range directly after the deposition of a Si thin film on a copper foil, we fabricated a copper silicide anode (CuSi-anode) with outstanding electrical and electrochemical properties. Herein, structural investigations using scanning electron microscopy and X-ray diffraction show a Cu-mediated silicidation at generating mixed phases of copper silicides, SiOx, Cu, and Si nanoparticles. The performance of battery cells with CuSi-anode having a Si thickness of 5 µm versus LiFePO4 shows a surface capacity of 2mAh/cm2 over 100 cycles with capacity loss in the course of cycling but with good electrical conductivity between the anode and current collector. Finally, we compare the electrochemical performance of the CuSi-anode with a conventional graphite anode at the same cell configuration and chemical conditions.