Enhancing potassium-ion storage of Bi₂S₃ through external-internal dual synergism: Ti₃C₂T_x 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 Bi2S3 through two-dimensional compositing and cation doping. Externally, Bi2S3 nanoparticles are loaded onto the surface of three-dimensional interconnected Ti3C2Tx nanosheets to stabilize the electrode structure. Internally, Cu2+ 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, Ti3C2Tx and Cu2+ collaboratively facilitate K+ intercalation. Subsequently, Cu2+ doping primarily promotes the fracture of Bi2S3 bonds, facilitating a conversion reaction. Throughout cycling, the Ti3C2Tx composite structure and Cu2+ doping sustain functionality. The resulting Cu2+-doped Bi2S3 anchored on Ti3C2Tx (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.