(ii) The development of free-standing, highly conductive electrodes to eliminate current collectors. Achieving the electrode-as-current collector approach is possible when nanomaterials with metallic conductivity such as carbon nanotubes26, graphene27 or 2D metal carbides15 are used as active materials, or at least constitute a large part of the electrode and are well interconnected. It is worth noting that complete elimination of the current collector for large-scale high-power devices can be challenging due to insufficient conductivity of the commonly used conductive carbons (multi-wall carbon nanotubes or reduced graphene oxide). Therefore, either some other materials with higher conductivity should be used (for example, metallic single wall carbon nanotubes, transition metal nitrides/carbides and so on) or a compromise should be reached between the current collector thickness and power characteristics of the device.