A mechanochemical method with SiO₂ as the grinding aid was used to enhance the leaching efficiencies of Co and Li from spent lithium batteries (LIBs). Experiment results show that the optimal leaching efficiencies of 94.91% for Co and 97.22% for Li were obtained under the parameters of SiO₂/LiCoO₂ mass ratio of 1:1, grinding speed of 500 r/min and grinding time of 30 min in citric acid. Characterization results indicate that the surficial properties of LiCoO₂ were changed after mechanochemical grinding treatment due to the newly generated surfaces on LiCoO_2. Meanwhile, the incompletely coordinated atomic structure and defective lattice structure lead to the activation of LiCoO₂. The reduction effect of carbon black on Co³⁺ under the action of mechanical forces increases its leaching efficiencies in the citric acid solution. The proposed process was found efficiently to recover Co and Li from LiCoO₂.