Enhancing potassium‐ion storage of Bi₂S₃ through external–internal dual synergism: Ti₃C₂Tx compositing and Cu²⁺ doping

Potassium‐ion batteries (PIBs) offer a cost‐effective and resource‐abundant solution for large‐scale energy storage. However, the progress of PIBs is impeded by the lack of high‐capacity, long‐life, and fast‐kinetics anode electrode materials. Here, we propose a dual synergic optimization strategy to enhance the K + storage stability and reaction kinetics of Bi 2 S 3 through two‐dimensional compositing and cation doping. Externally, Bi 2 S 3 nanoparticles are loaded onto the surface of three‐dimensional interconnected Ti 3 C 2 T x nanosheets to stabilize the electrode structure. Internally, Cu 2+ doping acts as active sites to accelerate K + storage kinetics. Various theoretical simulations and ex situ techniques are used to elucidate the external–internal dual synergism. During discharge, Ti 3 C 2 T x and Cu 2+ collaboratively facilitate K + intercalation. Subsequently, Cu 2+ doping primarily promotes the fracture of Bi 2 S 3 bonds, facilitating a conversion reaction. Throughout cycling, the Ti 3 C 2 T x composite structure and Cu 2+ doping sustain functionality. The resulting Cu 2+ ‐doped Bi 2 S 3 anchored on Ti 3 C 2 T x (C‐BT) shows excellent rate capability (600 mAh g –1 at 0.1 A g –1 ; 105 mAh g –1 at 5.0 A g –1 ) and cycling performance (91 mAh g –1 at 5.0 A g –1 after 1000 cycles) in half cells and a high energy density (179 Wh kg –1 ) in full cells.