TECHNICAL FIELD
The present disclosure relates to a method for reusing resources in the fabrication
of a lithium secondary battery. More particularly, the present disclosure relates to a
method for collecting and reusing a positive electrode scrap generated in the lithium
10 secondary battery fabrication process or positive electrode active materials of lithium
secondary batteries discarded after use. The present application claims the benefit of
Korean Patent Application No. 10-2020-0134325 filed on October 16, 2020 with the
Korean Intellectual Property Office, the disclosure of which is incorporated herein by
reference in its entirety.
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BACKGROUND ART
Lithium secondary batteries that can be recharged repeatedly are gaining attention
as an alternative to fossil energy. They have been primarily used in traditional handheld
devices such as mobile phones, video cameras and electric power tools. Recently, the
20 range of applications tends to gradually extend to vehicles which are powered by
electricity (EVs, HEVs, PHEVs), large-capacity energy storage systems (ESSs) and
uninterruptible power systems (UPSs).
A lithium secondary battery includes an electrode assembly including unit cells,
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each unit cell including a positive electrode plate and a negative electrode plate including a
current collector and an active material coated on the current collector with a separator
interposed between the positive electrode plate and the negative electrode plate, and a
packaging or a battery case in which the electrode assembly is hermetically received
5 together with an electrolyte solution. The lithium secondary battery primarily includes
lithium-based oxide as the positive electrode active material and a carbon-based material
as the negative electrode active material. The lithium-based oxide contains a metal such
as cobalt, nickel or manganese. In particular, cobalt, nickel and manganese are very
expensive invaluable metals. Among them, cobalt is a strategic metal, and its supply is
10 the focus of attention all over the world. Due to the limited number of cobalt producing
countries, the global supply of cobalt is unstable. When a supply and demand imbalance
of strategic metal occurs, there is a very high possibility that the cost of the raw material
will rise.
Studies have been made to collect and recycle invaluable metals from lithium
15 secondary batteries (waste batteries) discarded after the expiration date. In addition to
waste batteries, resources may be more preferably collected from waste materials
discarded after punching the positive electrode plate or the positive electrode in which
defects or failures occurred during the process.
Currently, the lithium secondary battery is fabricated, as shown in FIG. 1, by
20 coating a positive electrode slurry including a positive electrode active material, a
conductive material, a binder and a solvent on a long sheet-type positive electrode current
collector 10 such as an aluminum (Al) foil to form a positive electrode active material
layer 20, manufacturing a positive electrode sheet 30, and punching a positive electrode
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plate 40 to a predetermined size. The leftover after punching is discarded as a positive
electrode scrap 50. If the positive electrode active material is collected and reused from
the positive electrode scrap 50, it will be very desirable in the industrial-economic and
environmental aspects.
5 Most of the existing methods of collecting the positive electrode active material
include dissolving the positive electrode with hydrochloric acid, sulfuric acid, nitric acid
or the like, extracting the active material elements such as cobalt, nickel and manganese
and using them as raw materials for the positive electrode active material synthesis.
However, the active material element extraction using acids uses a non-eco-friendly
10 process to collect pure raw materials, and needs a neutralization process and a waste water
treatment process, resulting in the increased process cost. Additionally, it is impossible
to collect lithium, one of the key positive electrode active material elements. To
overcome these disadvantages, there is a need for a direct reuse method that does not
dissolve the positive electrode active material and does not extract the active material in
15 the form of an element.

WHAT IS CLAIMED IS:
1. A method for reusing a positive electrode active material, comprising:
(a-1) dry-milling a positive electrode scrap comprising a lithium composite
5 transition metal oxide positive electrode active material layer on a current collector to
bring the active material layer into a powdered state and separate from the current
collector;
(a-2) thermally treating the active material layer in powder form in air for thermal
decomposition of a binder and a conductive material in the active material layer, to collect
10 an active material;
(b) washing the collected active material with a lithium compound solution which
is basic in an aqueous solution and drying; and
(c) annealing the washed active material with an addition of a lithium precursor to
obtain a reusable active material.
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2. The method for reusing a positive electrode active material according to
claim 1, further comprising:
(d) surface-coating the annealed active material.
20 3. The method for reusing a positive electrode active material according to
claim 1, wherein the dry-milling uses any one of a pin mill, a disc mill, a cutting mill and a
hammer mill.
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4. The method for reusing a positive electrode active material according to
claim 1, further comprising:
shredding or cutting the positive electrode scrap before the dry-milling.
5 5. The method for reusing a positive electrode active material according to
claim 1, wherein the thermal treatment is performed at 300 to 1000℃.
6. The method for reusing a positive electrode active material according to
claim 1, wherein the lithium compound solution contains a lithium precursor in an amount
10 of more than 0% and 15% or less, and the washing is performed within 1 hour.
7. The method for reusing a positive electrode active material according to
claim 1, wherein the washing is performed by stirring the collected active material at the
same time with immersing in the lithium compound solution.
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8. The method for reusing a positive electrode active material according to
claim 1, wherein the lithium precursor is at least one of LiOH, Li2CO3, LiNO3 or Li2O.
9. The method for reusing a positive electrode active material according to
20 claim 1, wherein the lithium precursor is added in an amount for adding lithium at a ratio
of lost lithium to a ratio between lithium and other metal in a raw active material used in
the active material layer.
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10. The method for reusing a positive electrode active material according to
claim 9, wherein the lithium precursor is added in an amount for adding lithium at a molar
ratio of 0.001 to 0.4.
5 11. The method for reusing a positive electrode active material according to
claim 9, wherein the lithium precursor is added in an amount for adding more lithium at a
molar ratio of 0.0001 to 0.1 based on a 1 : 1 molar ratio of lithium : other metal.
12. The method for reusing a positive electrode active material according to
10 claim 1, wherein the annealing is performed in air at 400 to 1000℃.
13. The method for reusing a positive electrode active material according to
claim 1, wherein a temperature of the annealing step exceeds a melting point of the lithium
precursor.
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14. The method for reusing a positive electrode active material according to
claim 2, wherein the surface-coating step includes coating at least one of a metal, an
organic metal or a carbon material on the surface by a solid or liquid phase process, and
thermally treating at 100 to 1200℃.
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15. The method for reusing a positive electrode active material according to
claim 1, wherein the reusable active material is represented by the following Formula 1:
[Formula 1]
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LiaNixMnyCozMwO2+δ
where M comprises at least one selected from the group consisting of B, W, Al, Ti
and Mg, 1