Silicon/Carbon Composite Anode Materials for Li-Ion Batteries from a Scalable and Continuous One-Step Gas Phase Process

Abstract

Silicon as an anode material has been intensively studied in academia, yet issues correlated to the vast volume change still hinder application in industry greater than a few mass percent. Some approaches reported can suppress the rapid capacity fade, which is observed for pristine silicon powders. However, they are usually based on complex processes or involve expansive chemicals, making them less interesting for commercial applications. Our approach focuses on the production of a long-term stable, silicon-based composite material in a single, easy-to-scale manufacturing process in a free-space reactor.The newly developed composite consists of a silicon/carbon nanomaterial with a carbon-rich surface produced in a single-step gas phase process with production rates of already 100 – 500 g/h on the lab scale. Carbon is used as a composite component for two reasons: i) The incorporation of carbon in the range of 3-12 wt.% inhibits the formation of crystalline silicon within the silicon/carbon composites by disturbing the silicon-lattice, effectively preventing the formation of detrimental c-Li15Si4 phase during lithiation. ii) Furthermore, the carbon containing materials are less sensitive to oxidation and show enhanced cycling stability compared to pure silicon materials. By adjusting the process parameters, e.g. primary particle size d50,number can be tuned in the range of 40-120 nm. The electrochemical performance of the composite materials has been analyzed in half cells. For 75 wt.% active material electrodes, 90 % first cycle Coulombic efficiency and 75 % capacity retention after 200 cycles with an CCCV protocol at 0.5 C can be realized. Figure 1