Due to the current widespread use of lithium-ion batteries in a range of applications, significant amounts of metal-containing waste materials are generated. Typically, the recycling of transition metals from lithium-ion batteries involves leaching of Co²⁺ and Li⁺ from the LiCoO₂ anode and the electrolyte (e.g., LiPF₆, LiBF₄). Thus, we herein examined the application of slug flow to the extraction of Co²⁺ and Li⁺ from an aqueous solution into an organic (cyclohexane) phase containing di-(2-ethylhexyl)phosphoric acid (D2EHPA) as the extraction reagent. The extraction equilibrium and extraction rate were then investigated to design a novel extraction process. In addition, a microchannel was employed to extract the Co²⁺ and Li⁺ ions from the aqueous phase. We found that the D2EHPA–Na solution (prepared from the partial exchange of H⁺ from D2EHPA with Na) was effective for extracting Co²⁺ and, at a mole fraction of D2EHPA–Na >10%, complete Co²⁺ extraction from the aqueous phase was achieved. In addition, the presence of co-existing ions did not significantly affect the extraction behavior of Co²⁺ and Li⁺. Furthermore, the volumetric mass transfer coefficients (k_La) of Co²⁺ and Li⁺ exhibited the same order as those previously reported for other slug flow extraction systems. Finally, the ion concentration and selectivity were successfully simulated using the k_La values and the simulation results were in good agreement with experimental data. Such simulation of the Co²⁺ yield and purity is essential for selecting optimal process design conditions.