In the first generation of electrode architectures, researchers emphasized homogeneous nanomaterials, such as nanoparticles (0D), nanowires and nanotubes (1D), layered materials (2D) and mesoporous structures (3D). Nanoparticles of various chemical compositions have demonstrated great potential for high-rate energy storage. For typical Li-ion battery materials, such as LiCoO2, Si, Ge and so on, nanoparticles lead to substantial improvement in power performance and cycling behaviour due to shorter ion diffusion paths and accommodating Li insertion with minimal internal strain373839. In the case of EDLCs, superior power density at charging rates as high as 10 V s−1 was demonstrated for micro-supercapacitors based on carbon onions that are 6–7 nm in diameter40. 1D nanostructures (nanowires, nanotubes) offer most of the benefits of the nanoparticles and, moreover, they can be assembled into free-stranding and flexible electrodes without addition of binder due to their high aspect ratio394142. Conductive carbon nanotubes are used extensively as an additive to conventional battery electrodes to decrease electrode resistance and mitigate associated Ohmic losses, as well as to improve the rate performance of devices43.