Fig. 3. Probing the role of the active anode.

a SEM images and elemental mapping (EDS) of gallium distribution on anode. Before charging, liquid metal forms a spread-out network on Al. After charging, part of the liquid metal wraps up as spheres next to those newly grown aluminum sites. b The effect of liquid metal treatment time on capacity (charging and discharging current density of 20 A g⁻¹ and cut-off voltage of 2.45 V). c Galvanostatic charge and discharge curves. Graphene cathode has a mass of 0.026 mg and density of 0.16 mg cm⁻². Note the optimal time (4 h) has the lowest saturation voltage and maximum capacity (i_c = 200 A g⁻¹). d Stability test of our Al-ion batteries using active anode over 45,000 cycles (same charging and discharging current density of 40 A g⁻¹, cut-off voltage of 2.45 V). e Raman setup to study reaction on the active anode. f Time series of Raman spectra for one full cycle of charging and discharging at the interface of anode (i_c = i_dc). Al₂Cl₇⁻, 299 cm⁻¹ (green zone); AlCl₄⁻, 338 cm⁻¹ (yellow zone); Al₃Cl₁₀^-, 500 cm⁻¹ (red zone); and EMI⁺, 753, 790, 1135, 1410, 1590 cm⁻¹ (blue zone).