Tailored high-activity cathode materials are of great importance for construction of high-performance capacitors and hybrid batteries. In this work, we report a facile template-free chemical bath deposition method to fabricate porous Co3O4 nanoflake microspheres consisting of self-assembled nanoflakes with thicknesses of ∼10nm. The as-prepared Co3O4 microspheres have average diameters of ∼2μm and the secondary Co3O4 nanoflakes are interconnected with each other forming a highly open net-structure with pore diameters of 20-200nm. When evaluated as cathode materials for pseudocapacitive hybrid batteries, the Co3O4 nanoflake microspheres deliver a specific capacity of 83mAhg−1 at 1Ag−1 after 10,000 cycles, higher than the Co3O4 nanowire microspheres counterpart (70mAhg−1). In addition, the electrode exhibits excellent long-term cycling stability with 94.5% capacity retention after 10,000 cycles at 1Ag−1. The enhancement of high-rate electrochemical performances is due to the unique nanoflake microspheres architecture with large surface area and open porous structure.