Fig. 1. Ragone plot illustrating the performances of specific power vs. specific energy for different electrical energy storage technologies. Times shown in the plot are the discharge time, obtained by dividing the energy density by the power density^[5] (color online)

Fig. 2. K-edge absorption spectra of Cu^[24]

Fig. 3. In situ synchrotron radiation electrochemical XAS equipment^[26]

Fig. 4. Comparison of in situ XANES data collected on the electrode with that from the reaction model of Co(OH)₂ and CoOOH transformation (color online) (a) In-situ XANES spectra of the entire charge/discharge cycle, (b) Reaction model of Co(OH)₂ and CoOOH phase transformation, (c) In situ XANES spectra of the charging process, (d) In situ XANES spectra of the discharge process^[26]

Fig. 5. Structural changes of the electrode material during phase transition obtained by theoretical computations in comparison with in situ EXAFS fitting results (color online) (a) Phase transformation energy profile from DFT and the corresponding lattice structure changes, (b) In situ EXAFS spectra of an entire charge/discharge cycle in 3D mode, (c~d) In situ EXAFS spectra of the charge and discharge processes, respectively, (e~g) Fitting results of EXAFS spectra A, D and H, respectively^[26]

Fig. 6. Analysis of charge storage mechanism in Zn_xCo_1-xO NRs (color online)(a) O-K edge XAS spectra of Zn_0.04Co_0.96O NRs before and after processing at -0.2 V (Ag/AgCl), (b) Co-L_2,3 edge XAS spectra of Zn_xCo_1-xO NRs collected at -1 V and -0.2 V (Ag/AgCl), (c) Average Co-oxidation state change (right) and the corresponding theoretical/experimental capacity (left) of Zn_xCo_1-xO NRs from -1 V to -0.2 V (Ag/AgCl) based on the Co-L_2,3 edge spectra fitting^[27]

Fig. 7. Mn K-edge XANES spectra at different working potentials of Li-birnessite with Li₂SO₄ (a), Na₂SO₄ (b), K₂SO₄ (c), Rb₂SO₄ (d), and Cs₂SO₄ (e) electrolytes at 0.5 mol·L^{-1 [28]} (color online)

Fig. 8. Variation of the Mn oxidation states in Li-MnO₂ nanoplates with respect to the applied potentials. These oxidation states were derived from the XAS measurements of Li-birnessite within Li₂SO₄ (a), Na₂SO₄ (b), K₂SO₄ (c), Rb₂SO₄ (d), and Cs₂SO₄ (e) electrolytes, respectively^[28] (color online)

Fig. 9. (a) In-situ high-resolution Ni K-edge fluorescence XAS spectra of the as-prepared Ni(OH)₂-N-rGO_ae electrode at different charging/discharging potentials and XAS spectra of Ni standard compounds, and (b) Ni oxidation state vs. ΔE (eV) of the Ni(OH)₂-N-rGO_ae electrode during charging/discharging by a chronoamperometry method at different applied potentials (Ag/AgCl)^[29] (color online)

Fig. 10. In-situ electrochemistry SAXS experimental device^[38]

Fig. 11. Combined X-ray scattering and theoretical modeling for analysis^[40] (color online)

Fig. 12. Quantification of parameters controlling ion charge storage mechanisms^[41] (color online)

Fig. 13. Ion concentration change during potentiostatic charge/discharge^[41] (color online)

Fig. 14. Schematic of AMPIX electrochemical reaction cell^[47]

Fig. 15. (a) CV curves of the first 27 cycles of a ZMO electrode cycled in Li₂SiO₄ (aq) and the CV curve of a CLMO electrode (red dashed line) is also shown for comparison; (b) operando synchrotron XRD patterns obtained at the end of each cycle; and (c) XANES spectra of ZMO, ion-exchange derived TLMO, and CLMO^[46] (color online)

Fig. 16. (a) Operando XRD patterns during a CV scan and (b) in situ XANES spectra acquired at the end of cathodic and anodic scans of a CV cycle, respectively^[46] (color online)

Fig. 17. Synchrotron XRD (λ=0.467 94 Å) patterns and interlayer spacing vs. temperature curves recorded for BGO in: (a, d) 0.5 mol·L^-1 TEA-BF4 electrolyte, (b, e) 1 mol·L^-1 TEA-BF4 electrolyte, and (c, f) 2 mol·L^-1 TEA-BF4 electrolyte, upon cooling until the freezing of acetonitrile^[48] (color online)