One-minute deposition of micrometre-thick porous Si anodes for lithium ion batteries

We report the rapid vapour deposition of 3-14 μm-thick porous Si anodes on Cu current collectors in 10-60 s. Such rapid deposition was achieved by heating the Si source to over 2000°C, well above the melting point of Si, while the porous structure was realized in the deposited Si films by keeping the Cu collector at a much lower temperature of 100-500°C. The adhesion between the Cu collectors and Si films was enhanced by forming a CuSi_x intermixed layer by post-deposition annealing as well as surface treatment of the Cu collectors. Half-cell measurements showed that the porous Si anodes without post-annealing degraded in a few cycles. A markedly improved cycle performance (1000 mA h g_Si^-1 and 0.66 mA h cm_anode^-2 at the anode for the 50th cycle) was achieved for post-annealed 3.5 μm-thick porous Si films. Rapid vapor deposition of micrometre-thick porous Si films using inexpensive, safe Si powder is a practical route to fabricate high-capacity anodes for lithium ion batteries.