Fig 1

SEM images of low-magnification (a, c) and high-magnification (b, d) of hierarchical MnO2 nanoflowers synthesized at different concentration: (1) n(KMnO4) : n(KCl) = 1 : 3; (2) n(KMnO4) : n(KCl) = 3 : 1 37."

Fig 2

SEM and TEM images of the as-synthesized α-MnO2 nanowires 38. (a, b) SEM images at different magnifications, (c) TEM image, (d) HRTEM image, the inset image is the SAED pattern. "

Fig 3

SEM images of fours samples treated at various conditions 39. (a) 15 h at 25 ℃ (Sample B); (b) 20 h at 25 ℃ (Sample C); (c) 40 h at 25 ℃ (Sample D); (d) 3 h at 80 ℃ (Sample E). "

Fig 4

Schematic illustration of the formation of bowl-like MnO2 nanosheets 41."

Fig 5

(A) Schematic diagram and (B) photographs of the fabrication process of flexible solid-state supercapacitors based on graphene hydrogel films. (C) Low-and (D) high-magnification SEM images of the interior microstructure of the graphene hydrogel before pressing. (E) Low- and (F) high-magnification SEM images of the interior microstructure of the graphene hydrogel film after pressing 57."

Fig 6

Design and fabrication of alternating stacked graphene-conducting polymer hybrid film for in-plane MSCs 58. (a-c) Illustration of the fabrication procedure for in-plane MSCs with interdigital fingers, including (a) transfer of LBL stacked 2D nanohybrid film onto silicon wafer, (b) masking micropattern and deposition of gold current collector, (c) oxidative etching in oxygen plasma and drop-casting electrolyte. (d, e) Cross-section SEM images of 2D nanohybrid film. "

Fig 7

Cycling stability of P2G3-MSCs-C 58. 50 mV∙s −1 for 1000 cycles under flat and bending state. Inset shows the optical images of the device in flat and bend states."

Fig 8

Schematic illustration of the sequential steps for fabricating large-scale Re-PARG film 59."

Fig 9

(a) Digital photographs of flexible Re-PARG film. The top image exhibits the folding characteristics of the film. The bottom images illustrate the high flexibility (bending and twisting) of the film; (b) CV curves of Re-PARG film electrodes with two different bending angles of 0° and 180° at a scan rate of 5 mV∙s−1 59."

Fig 10

Schematic illustration of the process for producing single-layer β-Co(OH)2 nanosheets and SEM images of products after each step 60."

Fig 11

Electrochemical properties of RGO/β-Co(OH)2 NS composite-based electrode. (a) CV curves at different scan rates, (b) charge-discharge curves, (c) specific capacitance at different current densities, and (d) specific capacitance vs cycle number of the composite at a current density of 10 A·g−1 (inset of panel disgalvano static charge-discharge curves with time) 60."

Fig 12

(a) SEM, (b) TEM and (c) high-magnification TEM image of MnO2 nanofiber/graphene composites 63."

Fig 13

SEM images of (a) diatomite@graphene, (b) 3D graphene, (c-f) N-G@MnO2 synthesized with different reaction time (1, 3, 5 and 7 h) 64."

Fig 14

Electrochemical properties of N-G@MnO2//AG ASC 64. (a and b) CV curves tested at different potential windows and different scan rates. (c) Charge/discharge curves tested at different current (d) the energy density vs. power density in a Ragone plot densities. "

Fig 15

CV curves of the GR/MnO2-600 and GO/MnO2 hybrids at 200 mV∙s−1 69."

Fig 16

The figure of Composite Synthesis 70."

Fig 17

Schematic preparation representation of the all-solid-state cable-type supercapacitor based on the Cu/RGO/MnO2 fiber electrode 78."

Fig 18

XRD patterns (a) and SEM images of the ultralong α-MnO2 nanowires (b), δ-MnO2 nanosheets (c) and α-MnO2 nanowires@ultrathin δ-MnO2 nanosheets core-shell nanowires (d) 84."

Fig 19

(a) Galvanostatic charge-discharge curves of the ultralong α-MnO2 nanowires, the hierarchical α-MnO2 nanowires@ultrathin δ-MnO2 nanosheets core-shell nanowires and δ-MnO2 nanosheets. (b) Galvanostatic charge-discharge curves and (c) specific capacitance of the hierarchical α-MnO2 nanowires@ultrathin δ-MnO2 nanosheets core-shell nanostructure at different current densities. (d) Long-term cycle performance of the hierarchical α-MnO2 nanowires@ultrathin δ-MnO2 nanosheets core-shell nanostructure at 20 A∙g−1 84."

Fig 20

SEM images of typical FeCo2O4@MnO2 CSN on Ni foam 90."

Fig 21

Schematic illustration of the synthetic process of MnO2@NiO/ NiMoO4 HPCSs 91."

Fig 22

Electrochemical characterizations in 5 mol∙L−1 aqueous KOH at room temperature 91. (A) CV curves of different electrodes at a scan rate of 10 mV∙s−1. (B) CV curves at different scan rates and (C) charge-discharge curves at different current densities for the MnO2@NiO/NiMoO4 electrode. (D) The specific capacitance of different electrodes at different current densities. (E) Cycling stability and CE of the MnO2@NiO/NiMoO4 electrode at a current density of 3 A∙g−1; inset: the galvanostatic charge-discharge curve for the first ten cycles. "

Fig 23

The Ragone plot that relates power density to energy density of the MnO2@NiO/NiMoO4//AC ASC compared with CoMoO4/NiMoO4//AC, Ni(OH)2//AC, and NiO//rGO 91."

Fig 24

Schematic diagram illustrating of the fabrication process of MnO2 (a) and MnO2-Ni(OH)2 (f) in the M-NF/AB and MN-NF/AB electrodes, respectively; the SEM images of the M-NF/AB (b and d) and MN-NF/AB (c and f) with different magnifications, respectively 95."

Fig 25

(a) Optical graphics of Ni foam with different samples(c) SEM images of the MnO2@NiAl-LDH composites grown on Ni foam 99."

Fig 26

Schematic illustration of the fabrication process of NiAl-LDH/MnO2 and NiFe-LDH/MnO2 composites 100."

Fig 27

(a) CV curves of AC and NiAl-LDH/MnO2-6 at 10 mV∙s−1, and the inset shows the schematic of the NiAl-LDH/MnO2-6//AC ASC. (b) CV curves of NiAl-LDH/MnO2-6//AC ASC at different scan rates. (c) GCD curves of NiAl-LDH/MnO2-6//AC ASC at different current densities within a voltage of 1.58 V 100."

Fig 28

General scheme for the preparation of the NiMn-LDH/MnO2 composite obtained by restacking of oppositely charged nanosheets obtained by exfoliation of NiMn- LDH and MnO2 in formamide/water solutions 101."

Fig 29

Nitrogen adsorption-desorption isotherms (a) and pore size distribution (b) of the samples 101."

Fig 30

Capacity retention and cycling stability at 10 A∙g–1 of the whole series of prepared samples 101. (a) in 1 mol∙L−1 KOH and (b) in 0.5 mol∙L−1 Na2SO4. "

Fig 31

XRD patterns, cyclic voltammograms and Galvanostatic charge/discharge properties of MnO2/MoS2 composites 106. (a) XRD patterns of MoS2, pure MnO2 and MnO2/MoS2 composites; (b) Cyclic voltammetry curves of MnO2/MoS2 composites in 1 mol∙L−1 Na2SO4 aqueous electrolyte at various current densities in the potential window of −0.2 to −0.9 V; (c) Galvanostatic charge/discharge curves of MnO2/MoS2 composites in 1 mol∙L−1 Na2SO4 aqueous electrolyte at various current densities in the potential window of −0.2 to −1 V; (d) capacitance retention of MnO2/MoS2 composites at different current density. "

Fig 32

SEM images of stacked multilayer sheets of Ti3C2Tx_Ar (a) and ε-MnO2/Ti3C2Tx_Ar (b); TEM images of Ti3C2Tx_Ar sample (c) and ε-MnO2/Ti3C2Tx_Ar (d) 111."

Fig 33

(a) Schematic illustration of the synthesis process of MnO2/Ti3C2 nanocomposite; (b) SEM images of typical as-fabricated Ti3C2, and MnO2/Ti3C2 nanocomposite; TEM images of Ti3C2, and MnO2/Ti3C2; (c) XRD patterns of Ti3C2 and MnO2/Ti3C2 samples and magnification of XRD patterns 113."

Fig 34

(a) Illustration of the process for making the hybrid film, (b) Electrochemical performance of the hybrid film, (c) Two-electrode performance 114."

Fig 35

A schematic illustration of the formation of ultrathin Cu-MOF@δ-MnO2 nanosheets 116."

Fig 36

The electrochemical performance of K-CNM, Na-CNM and CNM measured in 1 mol·L−1 Na2SO4 (a) CV curves at the scan rate of 100 mV∙s−1; (b) GCD curves at 0.5 A∙g−1; (c) specific capacitances under different current densities; (d) EIS patterns at open circuit potentials 122."