Based on the principle of technically feasible reverse implementation, the objective of this work was to determine the optimal operating conditions that can be scaled up in an existing recycling plant for verification. First, after pretreatments the samples of screen undersize of 18650 cylindrical type and prism type of spent LiCo batteries (LIBs) were collected from a local spent battery recycling plant. After analysis, it was found that major elements in the 18650 cylindrical type spent LIB were Ni, Co, and Mn having 30-32 wt%, 30-32 wt%, and 17-29 wt%, respectively; whereas 73-75 wt% of Co and 5-10 wt% of Mn in the prism type spent LIB. Results of the acid leaching tests showed that the optimal leaching conditions were determined to be 80˚C, 3 M H2SO4 and 10 vol% H2O2 for the 18650 cylindrical type spent LIB, whereas 80˚C, 4 M H2SO4 and 10 vol% H2O2 for the prism type. Then various separation methods have been used for the separation of metallic ions in the leached solution. The relevant test results for the 18650 cylindrical type spent LIB are given as follows: (1) Under the condition of pH 3.8, ferric/ferrous ions were totally removed; (2) 0.45 M D2EHPA having a saponification degree of 35% could extract up to 79% of Mn without co-extraction of other metals; (3) The stripping efficiency for Mn was 100% if 0.1 M H2SO4 was used as the stripping agent; (4) When the aqueous solution was at pH 7, an extraction efficiency of 100% for Co was obtained by 2-stage extraction using Cyanex 272; (5) When the aqueous solution pH was adjusted to 8, an extraction efficiency of 100% for Ni was also obtained by 2-stage extraction using Cyanex 272; (6) The 2-stage stripping efficiency of 99% was obtained if 0.1 M H2SO4 was used as the stripping agent. On the other hand, the relevant test results for the prism type spent LIB are given as follows: (1) pH 10 and a molar ratio of 0.6 was found for carbonate to co-precipitate Co and Mn; (2) 80˚C, 0.3 M H2SO4 and 10 vol% H2O2 were capable of 100% dissolving the above-said cobalt carbonate and manganese carbonate. Tests results for electrowinning of metals are given as follows: (1) In the case of the 18650 cylindrical type spent LIB, the operation of electrowinning for 4 h and 5 h respectively could recover 100% of Ni from NiSO4 electrolyte and 100% of Co from CoSO4 electrolyte; (2) In the case of the prism type spent LIB, the operation of electrowinning for 5 h could recover 96% of Co from CoSO4 electrolyte. Based on the test results obtained from the aforementioned unit operations, the overall recoveries of 93% Co and 95% Ni were obtained for the 18650 cylindrical type spent LIB and 91% Co was obtained for the prism type spent LIB. In conclusion, satisfactory recycling flowcharts have been devised in this study. It is suggested that a semi-full scale testing should be carried out in the near future to verify the findings obtained in this study.

Spent LiCo battery; Recovery of metals; Optimal operating conditions