Developing a reliable synthesis strategy to concurrently realize electronic structure modulation and two-dimensionalization of materials is of paramount significance yet still challenging. Herein, a facile and universal strategy is reported to fabricate defect-abundant atomic-layered materials with unique electronic structures by mechanical shear-assisted exfoliation. As a proof-of-concept demonstration, atomic-layered defect-rich LiCoO2 nanosheets (AD-LCO) are successfully synthesized, which enable accelerated oxygen evolution kinetics with a substantially decreased oxygen evolution reaction overpotential by 184 and 216 mV at 10 and 50 mA cm–2, respectively. X-ray absorption spectroscopy suggests that AD-LCO possesses more d-band holes and enhanced Co-O covalency. Density functional theory calculations reveal that the presence of Co lattice vacancies can optimize the adsorption kinetics of intermediates, consequently lowering the energy barrier of the rate-determining step. Importantly, this method has universal applicability to the fabrication of other ultrathin defect-rich 2D materials such as BN, WS2, and MoS2. The study has potential implications for offering novel insights into the rational design of ultrathin 2D materials with abundant surface defects for various applications.