Porous silicon thin films as anodes for lithium ion batteries deposited by co-evaporation of silicon and zinc

Porous silicon thin films were fabricated by an innovative method using vacuum processing for the application as high capacity anode in lithium ion batteries. The deposition procedure comprises a co-evaporation of silicon and zinc, resulting in a deposition of a compound layer with deposition rates up to 100 nm/s and a subsequent thermal annealing. Due to its high vapor pressure, the zinc fraction is expelled and hence, a porous silicon matrix is formed. Herein, we introduce a novel and potentially scalable synthesis method for porous silicon films and show first analytical investigations concerning the layer morphology and the electrochemical properties. With the novel silicon anode excellent electrochemical performance, particularly high capacities of >3000 mAh/g, reasonable coulombic efficiencies of >90% in the initial cycle and comparably high cycle life>150 cycles can be demonstrated, which reveals their great potential for battery anode applications.