Engineered bilayer interfacial protection for stable aluminum metal anodes in aqueous batteries

Aqueous aluminum-ion batteries (AAIBs) have emerged as a promising energy storage technology due to their high energy density and the natural abundance of Al resources. However, the practical application of Al metal anodes is hindered by persistent challenges, including hydrogen evolution, corrosion, and passivation. To address these issues, we developed a bilayer artificial protective interface on the Al metal surface by combining a physically blade-coated activated carbon (AC) layer with an electrochemically deposited indium (In) particle layer. This InC hybrid layer synergistically suppresses side reactions, significantly enhancing anode stability. The resulting In-C@Al electrode delivers outstanding electrochemical performance. The In-C@Al symmetric cell achieves remarkable cycling stability, operating continuously for 2000 h with an ultra-low overpotential (<20 mV) and an average overpotential of just 5 mV. When paired with an Mn₃O₄ cathode, the In-C@Al||Mn₃O₄ full cell retains a high specific capacity of 146.72 mAh g^-1 after 700 cycles at 1 A g^-1, demonstrating an exceptional capacity retention of 90 %. Moreover, the In-C@Al||nickel hexacyanoferrate cell exhibits significantly improved cycling performance compared to its unprotected counterpart, maintaining 66.7 % capacity retention after 400 cycles. This work provides a universal paradigm for stabilizing Al metal anodes, paving the way for high-performance AAIBs.