Three‐Dimensional Hierarchical Nanoporosity for Ultrahigh Power and Excellent Cyclability of Electrochemical Pseudocapacitors

Electronic and ionic conductivity of pseudocapacitive SnO2 can be dramatically improved by a hierarchically oxide/metal nanoporous structure. The hierarchical nanoporosity gives rise to an exceptionally high volumetric power density of 257 W cm–3 and excellent cycling stability along with high volumetric energy density and ultrafast rate capability in both aqueous and nonaqueous electrolytes.