Specification Title of Invention: Cathode material including irreversible additive, secondary battery including cathode material, and manufacturing method thereof technical field [One] Cross-Citation with Related Application(s) [2] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0106090 dated August 24, 2020 and Korean Patent Application No. 10-2021-0110819 dated August 23, 2021, All content disclosed in the literature is incorporated as a part of this specification. [3] The present invention relates to a positive electrode material including an irreversible additive, a secondary battery including the positive electrode material, and a method for manufacturing the same background [4] Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy and clean energy is increasing. [5] Currently, a secondary battery is a representative example of an electrochemical device using such electrochemical energy, and its use area is gradually expanding. [6] Recently, as technology development and demand for portable devices such as portable computers, portable phones, and cameras increase, the demand for secondary batteries as an energy source is rapidly increasing. Among such secondary batteries, many studies have been conducted on lithium secondary batteries having high energy density, long cycle life, and low self-discharge rate, and are also commercialized and widely used. [7] In addition, as interest in environmental problems grows, research on electric vehicles and hybrid electric vehicles that can replace vehicles using fossil fuels such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution, is being conducted. have. Although nickel-metal hydride secondary batteries are mainly used as power sources for such electric vehicles and hybrid electric vehicles, research using lithium secondary batteries with high energy density is being actively conducted, and some are in the commercialization stage. [8] A carbon material is mainly used as a negative active material of such a lithium secondary battery, and a lithium transition metal composite oxide is used as a positive active material of a lithium secondary battery. Among them, various lithium transition metal oxides such as LiNiO 2 , LiMnO 2 , LiMn 2O 4 or LiFePO 4 have been developed in addition to lithium cobalt composite metal oxides such as LiCoO 2 having high operating voltage and excellent capacity characteristics. [9] Meanwhile, due to the consumption of Li ions during initial charging and discharging, a solid electrolyte interphase (SEI) layer is formed and irreversibility of the positive and negative electrodes occurs. Due to this, the energy density is reduced, and there is a problem in that the theoretical quantity that can be designed cannot be sufficiently used. [10] To solve this problem, lithium ions may be supplemented by adding an irreversible additive to the cathode material. However, Li 2NiO 2 , which is an irreversible additive conventionally used, has an orthorhombic crystal structure and belongs to a space group of Immm. However, there is a problem in that the material undergoes three-step structural change in the operating voltage range after initial charging of the secondary battery, causing impurities or gas to be generated. [11] Specifically, the material maintains an orthorhombic crystal structure in the range of 3.0 to 3.5 V, but according to the detachment of Li, trigonal at 3.5 to 4.0 V, and monoclinic at 3.5 to 4.25 V ( monoclinic) and undergoes three crystal structure changes. In particular, when an irreversible additive (Li 2NiO 2) having an orthorhombic crystal structure changes to an orthorhombic crystal structure, unpredictable by-products and excessive gas generation occur. Moreover, since it undergoes a change in the crystal structure, there is also a problem of poor structural stability. DETAILED DESCRIPTION OF THE INVENTION technical challenge [12] An object of the present invention is to provide an irreversible additive that minimizes the generation of impurities or gases in the operating voltage range of a secondary battery and has high structural stability. [13] Another object of the present invention is to provide a cathode material for a secondary battery including the irreversible additive, a secondary battery exhibiting excellent electrochemical properties including the same, and a method for manufacturing the same. means of solving the problem [14] A secondary battery according to an embodiment of the present invention is a secondary battery including a positive electrode in which a positive electrode material is applied on a positive electrode current collector, wherein the positive electrode material includes an irreversible additive and a positive electrode active material, and the irreversible additive includes In the operating range of 3.0V or more to 4.0V or less, lithium nickel oxide (LNO) having a trigonal crystal structure is included. [15] When the operating range of the secondary battery is greater than 4.0V and less than or equal to 4.25V, the lithium nickel oxide (LNO) having the trigonal crystal structure may be converted into a monoclinic crystal structure. [16] In the irreversible additive, the space group of lithium nickel oxide (LNO) having the trigonal crystal structure belongs to P3-m1, and the space group of lithium nickel oxide (LNO) having the monoclinic crystal structure is in C2/m can belong [17] The crystal lattice of the irreversible additive having the trigonal crystal structure may be a=3.0954Å, c=5.0700Å, γ=120.00°. [18] In the cathode material, the content of the irreversible additive may be 0.1 wt% to 10 wt% based on the total weight of the cathode material. [19] The positive active material may include an oxide represented by the following Chemical Formula 2: [20] Li(Ni aCo bMn c)O 2 (2) [21] In the above formula, 0 [101] The prepared secondary battery was charged and discharged three times at a C-rate of 0.1. [102] [103] [104] After activation of the prepared secondary battery at 0.025 citrate (C-rate), charging and discharging were performed twice at 0.1 citrate (C-rate). [105] [106] [107] Ex-situ XRD analysis was performed on the secondary batteries subjected to charging and discharging in Comparative Examples and Examples, and the results are shown in FIGS. 1 to 4 . [108] XRD analysis was measured with Bruker XRD D4 equipment, Cu source target was used, and experiments were conducted from 10° to 80° in 0.02 steps. [109] 2 and 3, when the secondary battery of Comparative Example was charged with 30% SOC, 60% SOC, and 90% SOC, both LNO (101) and LNO (002) peaks were detected. can be checked In particular, when charged to 30% SOC, the available voltage range corresponds to the range of 3.0V to 3.5V, it can be confirmed that both the LNO (101) and LNO (002) peaks are detected. In addition, even when charged to 60% SOC and 90% SOC, respectively, the available voltage range corresponds to the range of 3.0V to 4.0V and 3.0V to 4.25V, so that the LNO(101) and LNO(002) peaks are It can be confirmed that all are detected. [110] Accordingly, when charging and discharging is performed at 0.1 C-rate as in Comparative Example, the structure of at least a portion of the lithium nickel oxide (LNO), which is an irreversible additive, is not converted, and an orthorhombic structure is obtained. You can check what you have. In addition, at least a portion of lithium nickel oxide (LNO) within this available voltage range has an orthorhombic crystal structure, so that lithium nickel oxide (LNO) having an orthorhombic crystal structure has a trigonal crystal structure or a monoclinic crystal structure. Change can happen. In the process of this structural change, the secondary battery of Comparative Example is expected to be accompanied by a side reaction proceeding or gas/impurity generation. [111] [112] 4 and 5, after activation at 0.025 citrate (C-rate) for the secondary battery of the embodiment, XRD analysis according to the voltage change of the charging and discharging process twice at 0.1 citrate (C-rate) It can be confirmed that the LNO (101) and LNO (002) peaks disappear through two charging and discharging processes. [113] In particular, it can be seen that both the LNO ( 101 ) and LNO ( 002 ) peaks are detected in the one-time charging/discharging process. However, it can be seen that both the LNO 101 and LNO 002 peaks are not detected in the second charge/discharge process. [114] Accordingly, unlike the comparative example, in the example, the crystal structure of lithium nickel oxide (LNO) as an irreversible additive was changed to a trigonal crystal structure by activation at 0.025 citrate (C-rate) before two charging and discharging processes. that can be checked This embodiment activates lithium nickel oxide (LNO) with a relatively slow cilate, and is relatively within the voltage range of 3.5V to 4.0V in which lithium nickel oxide (LNO) is changed into a trigonal crystal structure compared to the conventional charging and discharging process. As it is activated for a long time, lithium nickel oxide (LNO) can change into a trigonal crystal structure. [115] Accordingly, the irreversible additive according to the embodiment includes a lithium nickel oxide having a trigonal crystal structure within an available voltage range, and the lithium nickel oxide included in the irreversible additive has a number of steps smaller than the number of steps of general structural change. By changing the structure, it is possible to minimize the progress of side reactions or the generation of gases/impurities as the structural change of each step proceeds. [116] [117] Although the preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also presented. It is within the scope of the invention. Claims [Claim 1] A secondary battery including a positive electrode in which a positive electrode material is applied on a positive electrode current collector, wherein the positive electrode material includes an irreversible additive and a positive electrode active material, and the irreversible additive has an operating range of 3.0 V or more to 4.0 V or less of the secondary battery. In the range, a secondary battery comprising lithium nickel oxide (LNO) having a trigonal crystal structure. [Claim 2] The rechargeable battery of claim 1 , wherein the lithium nickel oxide (LNO) having the trigonal crystal structure is converted into a monoclinic crystal structure when the operating range of the secondary battery is in the range of more than 4.0V to 4.25V or less. . [Claim 3] The space group of claim 2, wherein in the irreversible additive, the space group of lithium nickel oxide (LNO) having the trigonal crystal structure belongs to P3-m1, and the space group of lithium nickel oxide (LNO) having the monoclinic crystal structure. A secondary battery belonging to this C2/m. [Claim 4] The secondary battery of claim 3 , wherein a crystal lattice of the irreversible additive having a trigonal crystal structure is a=3.0954Å, c=5.0700Å, and γ=120.00°. [Claim 5] The secondary battery of claim 4 , wherein in the cathode material, the content of the irreversible additive is 0.1 wt% to 10 wt% based on the total weight of the cathode material. [Claim 6] The secondary battery of claim 1 , wherein the cathode active material includes an oxide represented by the following Chemical Formula 2: Li(Ni aCo bMn c)O 2 (2) In the formula, 0