Method for reusing active material using positive electrode scrap
There is provided a method for collecting and reusing an active material from positive electrode scrap. The method of reusing a positive electrode active material of the present disclosure includes (a-1) immersing a positive electrode scrap comprising an active material layer on a current collector into a basic solution to separate the active material layer from the current collector, (a-2) thermally treating the active material layer in air for thermal decomposition of a binder and a conductive material in the active material layer, and collecting an active material in the active material layer, (b) washing the active material collected from the step (a-2) with a lithium compound solution which is basic in an aqueous solution and drying, and (c) annealing the active material washed from the step (b) with a lithium precursor to obtain a reusable active material.
1 . A method for reusing a positive electrode active material, comprising:
(a-1) immersing a positive electrode scrap comprising an active material layer on a current collector into a basic solution to separate the active material layer from the current collector;
(a-2) thermally treating the active material layer in air for thermal decomposition of a binder and a conductive material in the active material layer, and collecting an active material in the active material layer;
(b) washing the active material collected from the step (a-2) with a lithium compound solution which is basic in an aqueous solution and drying; and
(c) annealing the active material washed from the step (b) with a lithium precursor to obtain a reusable active material.
2 . The method according to claim 1 , wherein the basic solution comprises LiOH or NaOH.
3 . The method according to claim 1 , further comprising:
(d) surface-coating the active material annealed from the step (c).
4 . The method according to claim 1 , wherein the thermal treatment in the step (a-2) is performed at 300 to 800° C.
5 . The method according to claim 1 , wherein the lithium compound solution contains a lithium compound in an amount of more than 0% and 15% or less, and the washing is performed within 1 hour.
6 . The method according to claim 1 , wherein the washing in the step (b) is performed by stirring the active material collected from the step (a-2) at the same time with immersing into the lithium compound solution.
7 . The method according to claim 1 , wherein the lithium precursor used in the annealing step (c) is one or more selected from the group consisting of LiOH, Li 2 CO 3 , LiNO 3 and Li 2 O.
8 . The method according to claim 1 , wherein, in the annealing step (c), the lithium precursor is added in an amount that satisfies a ratio of lithium to other metals in a raw active material used in the active material layer.
9 . The method according to claim 1 , wherein, in the annealing step (c), the lithium precursor is added in an amount corresponding to an amount of lithium at a molar ratio of 0.001 to 0.4 relative to an amount of lithium in a raw active material used in the active material layer.
10 . The method according to claim 8 , wherein, in the annealing step (c), the lithium precursor is further added in an amount corresponding to an amount of lithium at a molar ratio of 0.0001 to 0.1 relative to an amount of lithium in the raw active material used in the active material layer.
11 . The method according to claim 1 , wherein the annealing is performed in air at 400 to 1000° C.
12 . The method according to claim 1 , wherein a temperature of the annealing step exceeds a melting point of the lithium precursor.
13 . The method according to claim 1 , wherein the active material in the active material layer is collected in a form of powder, and carbon produced by carbonization of the binder or the conductive material does not remain on a surface of the powder.
14 . The method according to claim 3 , wherein the surface-coating step (d) includes coating at least one of a metal, an organic metal or a carbon material on a surface of the active material annealed from the step (c) by a solid or liquid phase process, and thermally treating at 100 to 1200° C.
15 . The method according to claim 1 , wherein the reusable active material is represented by the following Formula 1:
Li a Ni x Mn y Co z M w O 2+δ [Formula 1]
where M comprises at least one selected from the group consisting of B, W, Al, Ti and Mg, 1<a≤1.1, 0≤x<0.95, 0≤y<0.8, 0≤z<1.0, 0≤w≤0.1, −0.02≤δ≤0.02, x+y+z+w=1.
16 . The method according to claim 1 , wherein the reusable active material has a fluorine (F) content of 150 ppm or less.
17 . The method according to claim 1 , wherein the positive electrode scrap comprises a residual electrolyte solution, and the residual electrolyte solution is removed in the step (a-1), and
wherein the step (a-1) further comprises filtration and washing after the immersion.
18 . The method according to claim 1 , wherein, in the annealing step (c), the lithium precursor is added in an amount corresponding to an amount of lithium depleted during the steps (a-2) and (b).