▲

Fig. 1 An aqueous rocking-chair aluminum-ion capacitor. (a) Merits of Al³⁺ ions acting as the charge carriers. (b) Schematic illustration of the aqueous rocking-chair aluminum-ion capacitor. (c) Typical cyclic voltammetry curves of the graphene-based cathode and the MXene-based anode.

▲

Fig. 2 Pore-structure remolding of the graphene-based cathode. (a) Schematic illustration of the self-adaptive electrochemical pore-structure remolding process. (b) The first twenty CV curves of HOPC in the Al₂(SO₄)₃ electrolyte. (c) The first twenty CV curves of HOPC in the H2SO4 electrolyte, producing electrochemically activated HOPC (AHOPC). (d) The first twenty CV curves of AHOPC in the Al₂(SO₄)₃ electrolyte, producing completely remolded AHOPC (RHOPC). (e–g) Contour-type in situ Raman spectra of (e) HOPC in the Al₂(SO₄)₃ electrolyte, (f) HOPC in the H₂SO₄ electrolyte, and (g) AHOPC in the Al₂(SO₄)₃ electrolyte.

▲

Fig. 3 Electrochemical performance of the RHOPC electrode in the Al₂(SO₄)₃ electrolyte and its charge storage mechanism study. (a) CV curves at different scan rates (mV s⁻¹). (b) GCD curves at different current densities (A g⁻¹). (c) Gravimetric and volumetric capacitances at different current densities. (d and e) In situ FTIR spectra with different representations. (f) Corrected contour-type in situ FTIR spectra. (g) Electrode mass change upon potential variation during the EQCM test. (h) Electrode mass change versus CV scanning during the EQCM test.

▲

Fig. 4 Pore-structure remolding of the MXene-based anode. (a and b) TEM image (a) and STEM image (b) of Ti₃C₂T_x sheets. (c–f) TEM image (c), STEM image (d), HRTEM image (e), and SAED pattern (f) of AT-Ti₃C₂T_x sheets. (g and h) Cross-sectional SEM images of the (g) Ti₃C₂T_x film and (h) AT-Ti₃C₂T_x film. (i) The first twenty CV curves of AT-Ti₃C₂T_x in the Al₂(SO₄)₃ electrolyte. (j) Contour-type in situ XRD patterns of AT-Ti₃C₂T_x in the Al₂(SO₄)₃ electrolyte. (k) Typical XRD patterns of AT-Ti₃C₂T_x in the Al₂(SO₄)₃ electrolyte before and after pore-structure remolding.

▲

Fig. 5 Electrochemical performance of the RAT-Ti₃C₂T_x electrode in the Al₂(SO₄)₃ electrolyte and its charge storage mechanism study. (a) CV curves at different scan rates (mV s⁻¹). (b) GCD curves at different current densities (A g⁻¹). (c) Gravimetric and volumetric capacitances at different current densities. (d) Contour-type in situ Raman spectra. (e) Contour-type in situ XRD patterns. (f) In situ XRD patterns. (g–i) STEM-EDS mapping at fully discharged state: (g) TEM image, (h) corresponding STEM image, and (i) EDS mappings of characteristic elements.

▲

Fig. 6 Electrochemical performance of as-built aqueous rocking-chair AIC. (a) CV curves with different cut-off voltages (V). (b) CV curves at different scan rates (mV s⁻¹). (c) GCD curves at different current densities (A g⁻¹). (d) Gravimetric and volumetric capacitances at different current densities. (e) Capacitance delivery ratios of both cathode and anode at different current densities. (f) Ragone plots of the AIC, with red stars based on active materials and blue stars based on the whole device. (g) Long-term cycling stability at a current density of 5 A g⁻¹.