The high performance of Al3+-preintercalated Cu9S5 derived from layered double hydroxide precursor in aqueous Cu-Al hybrid-ion battery

Aqueous hybrid-ion batteries (AHBs) are a promising class of energy storage devices characterized by low cost, high safety, and high energy density. However, aqueous Cu-Al hybrid-ion batteries face challenges such as sluggish reaction kinetics and severe structural collapse of cathode materials, which limit their practical application. Here, a high-performance aqueous Cu-Al hybrid-ion battery is developed using aluminum pre-inserted Cu₉S₅ (Al-Cu₉S₅) as the cathode material, derived from CuAl-layered double hydroxide (CuAl-LDH). The Al³⁺ pre-intercalation strategy narrows the band gap, enhancing electron transport and improving electrochemical kinetics. The battery exhibits excellent rate performance (463 and 408 mA h g⁻¹ at current densities of 500 and 1000 mA g⁻¹, respectively) and good cycle stability (with a capacity retention ratio of 81% after 300 cycles at a current density of 1000 mA g⁻¹). Its performance surpasses that of most reported Al-ion batteries. Ex situ characterization and density functional theory (DFT) calculations reveal that the pre-intercalated Al³⁺ in Al-Cu₉S₅ participates in the reversible embedding/removal of Al ions during charge/ discharge processes. These findings provide valuable insights for designing pre-intercalated cathodes in aqueous Cu-Al hybrid-ion batteries with stable cycle life.