Phosphorus Vacancies Induced Electron Redistribution of Ni‐CoP _1‐x /Ti ₃ C ₂ Boosting Bimetallic Redox Activity for High‐Performance Hybrid Supercapacitors

Abstract Defect engineering is recognized as an effective strategy to address the sluggish reaction kinetics of cobalt phosphide (CoP). Herein, nickel‐doped CoP nanosheet arrays with different phosphorus vacancies (Ni‐CoP _1‐x ) are vertically grown on both sides of alkali‐induced 3D crumpled Ti ₃ C ₂ nanosheets. P vacancies can regulate the electronic structure of Ni‐CoP _1‐x /Ti ₃ C ₂ , inducing additional active sites and facilitating electron transfer, thereby enhancing the reaction kinetics. Meanwhile, 3D Ti ₃ C ₂ serves as a highly conductive and elastic substrate, boosting charge transport and mitigating volume changes of Ni‐CoP _1‐x during charge and discharge cycles. The unique 3D hierarchical structure promotes the exposure of more active sites and shortens the ion transport path. As a result, the optimal Ni‐CoP _1‐x /Ti ₃ C ₂ ‐3 electrode shows a high specific capacity of 1058 C g ⁻¹ at 1 A g ⁻¹ and an improved rate capability, which are attributed to the enhanced adsorption of OH ⁻ ions and the upward shift in d‐band centers of Ni 3d and Co 3d, as confirmed by density functional theory (DFT) calculations. The assembled Ni‐CoP _1‐x /Ti ₃ C ₂ ‐3//AC hybrid supercapacitor (HSC) exhibits a high energy density of 46.0 Wh kg ⁻¹ at 572.2 W kg ⁻¹ . This work presents an effective strategy for designing transition metal compounds for high‐performance energy storage.