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

Abstract Co 3 O 4 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 Co 3 O 4 lead to unsatisfactory charge storage capacity. For boosting its energy storage capability, rare earth (RE)‐doped Co 3 O 4 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 Co 3 O 4 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 Co 2+ /Co 3+ , oxygen vacancy content, crystalline phase, microstrain parameter, and the capacitance performance are regularly affected. Notably, Eu‐doped Co 3 O 4 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 Co 3 O 4 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 Co 3 O 4 in the development of high‐efficiency energy storage.