Manganese dioxide (MnO 2 ) materials have received much attention as promising pseudocapacitive materials owing to their high theoretical capacitance and natural abundance. Unfortunately, the charge storage performance of MnO 2 is usually limited to commercially available mass loading electrodes because of the significantly lower electron and ion migration kinetics in thick electrodes. Here, an alternatively assembled 2D layered material consisting of exfoliated MnO 2 nanosheets and nitrogen-doped carbon layers for ultrahighmass-loading supercapacitors without sacrificing energy storage performance is reported. Layered birnessite-type MnO 2 is efficiently exfoliated and intercalated by a carbon precursor of dopamine using a fluid dynamic-induced process, resulting in MnO 2 /nitrogen-doped carbon (MnO 2 /C) materials after self-polymerization and carbonization. The alternatively stacked and interlayer-expanded structure of MnO 2 /C enables fast and efficient electron and ion transfer in a thick electrode. The resulting MnO 2 /C electrode shows outstanding electrochemical performance at an ultrahigh mass loading of 19.7 mg cm −2 , high gravimetric and areal capacitances of 480.3 F g −1 and 9.4 F cm −2 at 0.5 mA cm −2 , and rapid charge/discharge capability of 70% capacitance retention at 40 mA cm −2 . Furthermore, asymmetric supercapacitor based on high-mass-loading MnO 2 /C can deliver an extremely high energy of 64.2 Wh kg −1 at a power density of 18.8 W kg −1 in an aqueous electrolyte.

Flexible, thin, and lightweight supercapacitors have been regarded as important power sources for portable and wearable electronics; however, these are usually limited by relatively low areal or volumetric performances compared to their gravimetric performance. In this paper, a large-area, thin, and flexible three-dimensional (3D) polyaniline nanoweb film with controlled nanomorphology is reported for the improvement of the areal and volumetric performances of supercapacitors. The 3D nanoweb structure provides large ion accessible active sites, short ion diffusion distance, and enhanced mechanical tolerance during electrochemical reactions. The resulting polyaniline nanoweb film electrodes exhibit a high areal capacitance of 303 mF/cm 2 at 10 mV/s, a high capacitance retention of 73% even at a high scan rate of 1000 mV/s, and long-term cycle stability (98.9% capacitance retention over 10000 cycles). The all-solid-state flexible supercapacitors deliver high device area-specific and volume-specific energy densities of 12.7 μWh/cm 2 and 1.0 Wh/L, respectively.

No abstract

No abstract

Two-dimensional molybdenum disulfide (MoS2) nanosheets have attracted great attention for electrochemical storage and conversion, but the scalable preparation of highly conductive and stable MoS2 nanosheets with a porous structure is challenging. Here, an efficient and high-throughput fluid dynamics process is presented for high-yield exfoliation of MoS2 with a phase transformation of 2H into 1T phase and basal activation of MoS2, resulting in ultrathin nanoporous nanosheets of MoS2 with a high-content 1T phase. The metallic and tailored porous structure in holey MoS2 nanosheets ensures a large ion-accessible area and rapid and efficient charge transport properties. The resulting MoS2 electrodes show an outstanding gravimetric capacitance of 572.6 F g–1 at 2 mV s–1, an impressive high capacitance retention of 71% measured in the 2–1000 mV s–1 range, and a good long-term stability with a capacitance retention of 96% over 10,000 cycles.