Abstract: Described herein are carbon-silicon composite structures and methods of producing such structures. A carbon-silicon composite structure comprises one or more carbon-containing structures that have pores at least partially filled with silicon-containing structures. Specifically, the silicon-containing structures are attached to the pore walls while maintaining void spaces within these pores. These void spaces can accommodate silicon expansion during lithiation. Carbon-silicon composite structures can be produced by submerging carbon-containing structures into a precursor liquid solution (comprising a precursor) and driving this solution into the pores. The silicon-containing structures are then formed (from the precursor) within the pores either electrochemically (e.g., by applying a voltage to the solution and structures) or chemically (e.g., by introducing the structures into a reducing liquid solution). In some examples, these void spaces are sealed from the environment by additional structures, e.g.

Abstract: Described herein are active materials for use in negative electrodes of lithium-ion electrochemical cells as well methods of forming such active materials. In some examples, an active material comprises secondary active-material structures, each formed by physical or chemical attachment of multiple primary active-material structures. These primary active-material structures can comprise one of silicon, silicon oxide, tin, tin oxides, germanium, metal, and silicide, and each structure can have a size of between 5 nanometers and 30 micrometers. The small size of the primary active-material structures helps to maintain the mechanical stability of these structures as well as of the secondary active-material structures during battery cycling. Furthermore, these specific arrangements of the primary active-material structures support high charge-discharge rates. Some of the secondary active-material structures can be joined with other such structures, e.g., forming a network of the structures.

Abstract: Described herein are electrochemically active-material structures comprising high-capacity materials. The mean largest cross-sectional dimension of these structures is kept below the pulverization threshold, which corresponds to the structures' composition. As such, the structure fracturing during battery cycling is reduced thereby preserving the battery capacity. Furthermore, these structures have a sphericity of at least about 0.9. Such high sphericity values translate into a small surface area for a given volume thereby reducing the electrolyte decomposition and solid electrolyte interphase (SEI) formation on the surface of these structures. Furthermore, the small size and high sphericity help to keep swelling substantially isotropic nature. The small structure size also helps with preserving the initially formed SEI layer thereby limiting this SEI formation to initial cycles.