The hybrid devices based on traditional planar architectures are limited in the thickness of the pseudocapacitive electrode because of low electrical and ionic conductivities, which slow the overall device kinetics. Both ionic and electronic conductivities are critical for increasing rate performance of battery electrodes, especially when large and multivalent ions are used in electrolytes35. As a result, the energy density of EES materials in thick electrodes is much lower than the theoretical values that can be achieved with very thin films. Thus, an important goal for EES electrodes is co-integration of different materials at the nanoscale and the development of new material architectures that are scalable and enable rapid ion access to each electrochemically active site. As discussed in the following section, new approaches to electrode design need to be implemented to achieve fast energy storage combined with high energy density and a long cycling lifetime for devices. In particular, a transition to 3D nanoarchitectures is required to improve ion access to electrochemically active surfaces and minimize both diffusion limitations as well as macroscopic electrode strain during charging/discharging. 3D architectures also allow the use of thicker electrodes. As a general strategy, the use of nanostructured materials36 allows us to increase ion accessibility and rate performance owing to their high surface-to-volume ratio.