Surficial modification enabling planar Al growth toward dendrite-free metal anodes for rechargeable aluminum batteries

Al metal possesses ultrahigh theoretical volumetric capacity of 8,040 mAh cm⁻³, and gravimetric capacity of 2,980 mAh g⁻¹, and thus is highly attractive for electrochemical energy storage. However, it suffers from several issues, such as the dendrite formation, during Al stripping–deposition cycling, which has been verified to account for the short circuit and limited cyclic performance. Herein, we use a facile and applicable method to in-situ reconstruct the Al anode surface with F-Al-O chemical bonds, which could preferentially induce the planar growth of Al along the interface plane, thus leading to the dendrite-free morphology evolution during the cycling. Benefiting from F-Al-O chemical bonds on the surface of Al anodes, long lifespan of symmetric cells can be realized even under 1 mA cm⁻² and 1 mAh cm⁻². Coupling the F-Al anode with graphite-based cathodes, high-voltage dual-ion Al metal batteries can be achieved with long-term cycle stability up to 1,200 cycles (at 0.5 mA cm⁻²), surpassing the counterparts using pristine Al metal anode. Furthermore, the effectiveness of this surficial modification strategy is also elucidated with the aid of theoretical calculation. This work provides novel insights on low-cost and facile strategies against the Al dendrite growth in aluminum batteries.