Metal Aluminum-Free Configuration Toward High-Performance Aqueous Aluminum Ion Battery

Rechargeable aluminum batteries hold great promise for high energy density and low-cost energy storage applications but are stalled by severe electrochemical side reactions (e.g., dendrite, passivation, and corrosion) at aluminum (Al) metal anode. Here, we design an aluminum ion battery with an Al-free configuration to circumvent the problems caused by the above side reactions. The feasibility of Al_xMnO₂·nH₂O cathode in aluminum ion batteries is revealed in conjunction with TiO₂ anodes by using the optimal 5 M Al(OTF)₃ electrolyte. The as-assembled aluminum ion battery enables high initial discharge capacity of 370.4 mAh g^–1 at 30 mA g^–1, favorable stability with low irreversible capacity loss, and enhanced safety. Further, the mechanism is intensively elucidated by multiple characterization results, indicative of the Al³⁺ ions (de)intercalation redox chemistry. Revealed by empirical analyses, the capacity contribution of high-voltage plateau, corresponding to the disproportionation reaction of Mn³⁺ in an Al_xMnO₂·nH₂O battery system, tends to increase with the increasing electrolyte concentration. Our findings may provide fresh impetus to the rational design of aluminum ion batteries with excellent electrochemical properties.