Chemical Pre‐Lithiation Toward Scalable Manufacturing of Aluminum Foil Anodes With Unique Gradient Surface Layer for Copper‐Free Lithium‐Ion Batteries

Abstract High‐capacity aluminum (Al) anodes for lithium storage suffer from severe lithium loss, large volume expansion, and uneven stress distribution, leading to rather poor Coulombic efficiency and short cycle life. Here, a simple chemical pre‐lithiation strategy is employed that transforms native Al ₂ O ₃ into a fast‐ion‐conducting LiAlO ₂ . This enables controlled lithium infusion (<1 mAh cm ⁻² ) into ultrathin Al foil, forming a uniform gradient Li‐Al alloy surface layer. Such a gradient layer facilitates homogeneous Li⁺ distribution and alloying reactions while promoting vertically aligned Li⁺ diffusion, mitigating lateral stress accumulation. It also continuously replenishes lithium losses during cycling and enhances structural integrity via its high Young's modulus. By paired with LiCoO ₂ cathode, the Al‐based anode exhibits superior rate capability (185.5 mAh g ⁻¹ at 0.1 C and 164.3 mAh g ⁻¹ at 10 C) and an impressive capacity retention of 87% over 600 cycles at 2 C. The copper‐free design yields high energy densities (529 Wh kg ⁻¹ and 1190 Wh L ⁻¹ ) at reduced cost. Furthermore, the pre‐lithiated Al foil is well‐suited to current production technologies, coupled with the pioneering achievement of assembling Ah‐scale pouch cells, suggesting its high practicability for future high‐energy Li‐ion batteries.