The use of elongated nanostructures in separators and associated devices and methods, including devices and methods for energy storage and/or use, are generally described. According to certain embodiments, the elongated nanostructures can extend from a first solid substrate to a second solid substrate. In some embodiments, the nanostructures penetrate a surface of the first solid substrate (e.g., a first electrode) and/or a surface of the second solid substrate (e.g., a second electrode). The elongated nanostructures can, according to certain embodiments, provide structural reinforcement between two substrates (e.g., between two electrodes) while maintaining electronic insulation between the two substrates.