Rare Earth Doping Engineering Tailoring Advanced Oxygen‐Vacancy Co₃O₄ with Tunable Structures for High‐Efficiency Energy Storage

Abstract Co₃O₄ with high theoretical capacitance is a promising electrode material for high‐end energy applications, yet the unexcited bulk electrochemical activity, low conductivity, and poor kinetics of Co₃O₄ lead to unsatisfactory charge storage capacity. For boosting its energy storage capability, rare earth (RE)‐doped Co₃O₄ nanostructures with abundant oxygen vacancies are constructed by simple, economical, and universal chemical precipitation. By changing different types of RE (RE = La, Yb, Y, Ce, Er, Ho, Nd, Eu) as dopants, the RE‐doped Co₃O₄ nanostructures can be well transformed from large nanosheets to coiled tiny nanosheets and finally to ultrafine nanoparticles, meanwhile, their specific surface area, pore distribution, the ratio of Co²⁺/Co³⁺, oxygen vacancy content, crystalline phase, microstrain parameter, and the capacitance performance are regularly affected. Notably, Eu‐doped Co₃O₄ nanoparticles with good cycle stability show a maximum specific capacitance of 1021.3 F g⁻¹ (90.78 mAh g^‐1) at 2 A g^‐1, higher than 388 F g^‐1 (34.49 mAh g^‐1) of pristine Co₃O₄ nanosheets. The assembling asymmetric supercapacitor delivers a high energy density of 48.23 Wh kg^‐1 at high power density of 1.2 kW kg^‐1. These findings denote the significance and great potential of RE‐doped Co₃O₄ in the development of high‐efficiency energy storage.