Method for recovering active metal of lithium secondary battery
In a method of recovering an active metal of a lithium secondary battery, a cathode active material mixture is prepared from a waste cathode of a lithium secondary. The cathode active material mixture is reacted with a reductive reaction gas to form a preliminary precursor mixture having a reduction degree of transition metal defined by Equation 1 in a range from 0.24 to 1.6. A lithium precursor is recovered from the preliminary precursor mixture. A lithium recovery ration is improved by adjusting the reduction degree of transition metal.
1 . A method of recovering an active metal of a lithium secondary battery, the method comprising:
preparing a cathode active material mixture comprising a lithium-transition metal oxide from a waste cathode of a lithium secondary battery;
reacting the cathode active material mixture with a reductive reaction gas to form a preliminary precursor mixture having a reduction degree of transition metal defined by Equation 1 in a range from 0.24 to 1.6; and
recovering a lithium precursor from the preliminary precursor mixture:
wherein the reduction degree of transition metal=(MeO phase fraction+lithium-transition metal oxide phase fraction)/(Me phase fraction) [Equation 1]
wherein Me includes Ni and Co; and
wherein the MeO phase fraction, the lithium-transition metal oxide phase fraction and the Me phase fraction are measured by a Rietveld crystal structure analysis for X-ray diffraction (XRD) analysis peaks of the preliminary precursor mixture.
2 . The method of recovering an active metal of a lithium secondary battery according to claim 1 , wherein the lithium-transition metal oxide is represented by Chemical Formula 1:
Li x Ni a Co b Mn c O y [Chemical Formula 1]
wherein 0<x≤1.1, 2≤y≤2.02, 0<a<1, 0<b<1, 0<c<1, and 0<a+b+c≤1.
3 . The method of recovering an active metal of a lithium secondary battery according to claim 1 , wherein the reductive reaction gas includes hydrogen and a carrier gas, and a hydrogen concentration in the reductive reaction gas is in a range from 10 to 40 vol %.
4 . The method of recovering an active metal of a lithium secondary battery according to claim 1 , wherein a reaction temperature with the reductive reaction gas is in a range from 400 to 600° C.
5 . The method of recovering an active metal of a lithium secondary battery according to claim 1 , wherein the preliminary precursor mixture comprises preliminary lithium precursor particles and transition metal-containing particles, and
the transition metal-containing particles comprise Ni, Co, NiO, CoO, and MnO.
6 . The method of recovering an active metal of a lithium secondary battery according to claim 5 , wherein the preliminary lithium precursor particles comprise at least one of lithium hydroxide, lithium oxide, and lithium carbonate.
7 . The method of recovering an active metal of a lithium secondary battery according to claim 5 , wherein the recovering of the lithium precursor comprises washing the preliminary lithium precursor particles with water.
8 . The method of recovering an active metal of a lithium secondary battery according to claim 5 , further comprising selectively treating the transition metal-containing particles with an acid solution to recover a transition metal precursor in the form of an acid salt.
9 . The method of recovering an active metal of a lithium secondary battery according to claim 1 , wherein the reduction degree of transition metal of the preliminary precursor mixture is in a range from 0.24 to 1.0.
10 . The method of recovering an active metal of a lithium secondary battery according to claim 1 , wherein the forming of the preliminary precursor mixture comprises reacting the cathode active material mixture with the reductive reaction gas in a fluidized bed reactor under conditions controlled to achieve the reduction degree defined by Equation 1.