After electrochemical intercalation and ion exchange, ideally Li0.94CoO2 will be delithiated to Li0.48CoO2 for high purity Li + recovery. The delithiation showed Li1-vCoO2 charging type curve (Supplementary Fig. ) . With no doubt, C-rate of the following extraction is still critical in determining the ion pathway from Li0.48CoO2 to Li0.94CoO2. We found that the intercalation behavior differs significantly at different rates, and it correlates with the relative rates of intercalation and ion exchange. Therefore, to be quantitative, we define CpseudoIX to characterize the average rate of the initial ion exchange starting from NCO so that CpseudoIX = (yinitial -yfinal)/𝜏, where yinitial and yfinal is the Na + content in NayCoO2 phases before and after ion exchange, respectively (Supplementary Table ). The yfinal is determined by comparing the plateau voltage to Na1-vCoO2 charging curve . The 𝜏 is the time of ion exchange between yinitial and yfinal (Supplementary Fig. ). The kinetics of ion exchange is affected by many factors such as particle morphology, electrolyte transport, and especially particle packing and electrode porosity. A detailed investigation on these effects is beyond the scope of this work; however, the use of CpseudoIX offers a simplified metric to compare the ion exchange kinetics with intercalation kinetics, the applied C-rate (Cinter).