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 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. 10-2020-0079624 filed on June 29, 2020 with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 15 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, 3 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 4 plate 40 to a predetermined size. The leftover after punching is discarded as 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. Meanwhile, the positive electrode sheet 30 usually goes through roll pressing. Thus, in the case of the positive electrode scrap from the electrode, the particles on the surface may be cracked or chipped when pressed down by the roll pressing process. The unused fresh active material has no particle cracking or chipping, but in the case of 20 reusable active material obtained from the roll pressed electrode, with the increasing particles cracked or chipped by roll pressing, the specific surface area of the active material increases, which affects the slurry properties, electrode adhesion and electrode performance reused during reuse. Accordingly, it is necessary to solve the problem. 5 DISCLOSURE Technical Problem The present disclosure is directed to providing a method for collecting and reusing 5 active materials from positive electrode scrap. Technical Solution To achieve the above-described problem, a positive electrode active material reuse method of the present disclosure includes (a) thermally treating positive electrode scrap 10 comprising a lithium composition transition metal oxide positive electrode active material layer on a current collector in air for thermal decomposition of a binder and a conductive material in the active material layer, to separate the current collector from the active material layer, and collecting an active material in the active material layer, (b-1) washing the collected active material with a lithium compound solution which is basic in an 15 aqueous solution, (b-2) mixing the washed active material with a lithium precursor solution and spray drying to obtain an active material with particle control by an addition of a lithium precursor, and (c) annealing the spray dried active material to obtain a reusable active material. In the present disclosure, the step (b-2) includes coating the lithium precursor on a 20 surface of the active material, and the step (c) includes annealing without addition of additional lithium precursor. In the present disclosure, a temperature of the spray drying step may be 100 to 300℃. 6 In the present disclosure, the positive electrode active material reuse method may further include (d) surface-coating the annealed active material. The thermal treatment may be performed at 300 to 650℃. The thermal treatment may be performed at 550℃ for 30 minutes at a temperature 5 rise rate of 5℃/min. The lithium compound solution contains a lithium compound, preferably LiOH, in an amount of more than 0% and 15% or less. The washing may be performed within 1 hour. The washing may be performed by stirring the collected active material at the 10 same time with immersing in the lithium compound solution. The lithium precursor may be at least one of LiOH, Li2CO3, LiNO3 or Li2O. The lithium precursor may be 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. 15 For example, the lithium precursor may be added in an amount for adding lithium at a molar ratio of 0.001 to 0.4. Further, the lithium precursor is preferably 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. 20 The annealing may be performed in air at 400 to 1000℃. A temperature of the annealing step may exceed a melting point of the lithium precursor. The active material in the active material layer may be collected in a form of 7 powder, and carbon produced by carbonization of the binder or the conductive material may not remain on a surface. The surface-coating step may include 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 5 treating at 100 to 1200℃. The reusable active material may be represented by the following Formula 1: [Formula 1] LiaNixMnyCozMwO2+δ where M comprises at least one selected from the group consisting of B, W, Al, Ti 10 and Mg, 1