Rare Earth Doping Engineering Tailoring Advanced Oxygen-Vacancy Co 3 O 4 with Tunable Structures for High-Efficiency Energy Storage.

Co O  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 O  lead to unsatisfactory charge storage capacity. For boosting its energy storage capability, rare earth (RE)-doped Co O  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 O  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 /Co , oxygen vacancy content, crystalline phase, microstrain parameter, and the capacitance performance are regularly affected. Notably, Eu-doped Co O  nanoparticles with good cycle stability show a maximum specific capacitance of 1021.3 F g (90.78 mAh g ) at 2 A g , higher than 388 F g (34.49 mAh g ) of pristine Co O  nanosheets. The assembling asymmetric supercapacitor delivers a high energy density of 48.23 Wh kg  at high power density of 1.2 kW kg . These findings denote the significance and great potential of RE-doped Co O  in the development of high-efficiency energy storage.