In the present manuscript, a simple hydrometallurgy process for recovering and recycling cobalt from spent lithium cobalt oxide LiCoO2 (LCO) in lithium-ion batteries (LIBs) is described. First, the black material (BM) containing LCO active material is extracted by discharging, dismantling and detachment of cathode active materials with an organic solvent. Then, sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) are used to fully dissolve Co and Li in an aqueous solution at high dissolution efficiency (more than 99% of Li and Co). After a purification step, Co is selectively precipitated and separated from Li, as CoCO3, using a simple method. Results show that the obtained CoCO3 crystals have a unique sheets-like structure with a purity of more than 97% and could be reused to regenerate LCO active material for LIB. The as-prepared sheet-like CoCO3 was then converted to flower-like LCO through a solid-state reaction with commercial lithium carbonate (Li2CO3). Electrochemical performances of the regenerated LCO (LCOReg) in LIB have been studied. Interestingly, the flower-like LCOReg showed a good charge capacity of about 145 mAh.g−1 at the first cycle, compared to LCO synthesized from commercial cobalt and lithium precursors (LCOCom). Specific charge capacity and columbic efficiency also remained relatively stable after 60 charge/discharge cycles. The proposed recycling process of Co in the present work doesn’t require the use of the complicated and expensive solvent extraction method and thus it is simple, cost-effective, environmentally-friendly and could be used for recovering high purity critical metals such as Co and Li from spent LIBs at the industrial scale.