Si/nanoporous carbon composites are promising anode materials for high-energy-density lithium-ion batteries. Chemical vapor deposition of Si into nanoporous carbon is an efficient approach to synthesize high-performance Si/nanoporous carbon composites. While attractive performance has been demonstrated experimentally, there is a lack of modeling work to understand how experimental conditions and carbon properties affect deposition geometry and uniformity. This study aims to develop a general model of chemical vapor deposition of silicon into nanoporous carbon in a tube furnace, which describes key processes such as advection, diffusion, and reaction kinetics. Various parameters such as temperature, pressure, tube length, flow rate, surface area, and pore size were investigated to determine their effects on deposition uniformity and filling portion along the tube. The simulation results align with experimental results reasonably. The model predicts that lower temperature, lower pressure, higher flow rate, less carbon loading, and lower specific surface area favor better uniformity across the whole tube furnace. This work provides valuable insights for optimizing the operating conditions in tube reactors and can contribute to the advancement of deposition processes.

Energy storage devices with high energy and power densities are highly attractive for various applications ranging from portable electronics to electric vehicles and grid-level energy storage, such as rechargeable batteries and supercapacitors. One limiting factor in power density is the ion transport in electrolyte, particularly in tortuous electrode materials with low porosity. A viable approach to enhance ion transport in electrolyte is to create vertically aligned structures and thus reduce electrode tortuosity. In the past decades, various methods have been explored to develop vertically aligned structures. This review summarizes battery kinetics to illustrate the importance of low tortuosity in electrodes, and then introduces various methods to create vertically aligned nanostructures, such as direct growth, templating and microfabrications. The electrochemical performance of electrodes or electrolytes created by each method is presented. At the end, this paper discusses challenges with these structures and the directions these technologies can be taken in the future.