Simultaneously high mass-loading and volumetric energy density in Ag2O-intercalated MnO2-based supercapacitor with rapid electron/ion transport channels

High volumetric energy density (VED) is essential for supercapacitors' practicality, but is extremely challengeable when high mass-loading is simultaneously demanded, because the high mass-loaded electrode always encounters the limited ions-diffusion accessibility and sluggish electron transferability. Herein, for the first time, Ag2O-intercalated hollow MnO2 (Ag2O-HMnO2) electrode with rapid ion/electron transport channels is rationally designed and fabricated by a facile in-suit growth & self-sacrificing template method. Ultrahigh massloading benefits from the randomly arrayed MnO2-nanosheets fully covered on silver-nanowire@polypyrrole (AgNW@PPy-template). Vast interior space in MnO2, which forms after the oxidative decomposition of AgNW@PPy-template, offers large electrode-electrolyte interfaces and huge open space channel for unimpeded ions transport. Such Ag2O-intercalated hierarchical hollow structure not only provides spacious "ion transport channel" (hollow interior space) and "reservoir" (much space between neighboring MnO2-nanosheets) for ions diffusion/storage, but also boosts electron transferability via the conductive Ag2O-particulate-based percolation networks. As a consequence, Ag2O-HMnO2 exhibits excellent electrochemistry performance and unprecedented MnO2 utilization efficiency. Ag2O-HMnO2-based supercapacitor exhibits a remarkably enhanced VED of 7.33 mWh cm-3, approximately sixfold improvement compared to that of pristine MnO2. The novel structure engineering strategy presented herein facilitates the excellent ion/electron transferability, which may open a new avenue for transition-metal-oxide/hydroxides-based supercapacitors to achieve high mass-loading and VED.