Capacitive deionization process

A capacitive deionization process comprising:

• a charge water providing step of providing charge water containing lithium ions and other impurities by first heat-treating nickel-cobalt-manganese-lithium mixture of a waste battery and then dissolving the heat-treated nickel-cobalt-manganese-lithium mixture of the waste battery;
• a discharge water providing step of providing discharge water containing lithium ions and ethanol such that lithium ions are in a saturated state in the discharge water, wherein a ratio of the ethanol in the total discharge water is maintained at a substantially constant 50%;
• a charging step of applying power to a capacitive deionization apparatus in a charging state and supplying the charge water to the capacitive deionization apparatus for a first predetermined period of time;
• a charge water removing step of removing, after the first predetermined period of time, the charge water from the capacitive deionization apparatus, wherein the capacitive deionization apparatus remains in the charging state until complete removal of the charge water from the capacitive deionization apparatus;
• a discharging step of applying power to the capacitive deionization apparatus in a discharging state and supplying the discharge water to the capacitive deionization apparatus for a second predetermined period of time;
• and
• a discharge water removing step of removing, after the second predetermined period of time, the discharge water from the capacitive deionization apparatus,
• a crystal recovery step of recovering a crystal of the lithium ions precipitated in the capacitive deionization apparatus and/or the discharge water, wherein the crystal recovery step is performed after repeating the charging step, the charge water removing step, the discharging step, the discharge water removing step for a third predetermined period of time.