Specification Title of Invention: A positive electrode and a secondary battery including the positive electrode Technical field [One] Mutual citation with related applications [2] This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0023971 filed on February 27, 2018, and all contents disclosed in the documents of the Korean patent application are included as part of this specification. [3] [4] Technical field [5] The present invention includes a current collector and a positive electrode active material layer disposed on the current collector, wherein the positive electrode active material layer includes a positive electrode active material, a conductive material, and a binder, and the conductive material is at least one of carbon black and carbon nanotubes. Including, wherein the binder includes polyvinylidene fluoride to which a functional group is bonded, and the functional group includes a carboxyl group, and the carboxy group calculated by the following formula 1 in the polyvinylidene fluoride to which the functional group is bonded The content of is from 1.1 mol% to 3.0 mol% relates to a positive electrode and a secondary battery including the same. [6] [Equation 1] [7] [B/(A+B)] × 100 [8] A is the integral value of the peak of the unit derived from vinylidene fluoride when the 1 H NMR spectrum is measured for the polyvinylidene fluoride to which the functional group is bound, and B is 1 H for the polyvinylidene fluoride to which the functional group is bound. When measuring the NMR spectrum, it is the integral value of the peak of the carboxyl group. Background [9] Recently, as technology development and demand for mobile devices increase, the demand for batteries as an energy source is rapidly increasing, and accordingly, various studies on batteries that can meet various demands are being conducted. In particular, research on a lithium secondary battery having high energy density and excellent lifespan and cycle characteristics as a power source of such a device is actively being conducted. [10] A lithium secondary battery includes a positive electrode including a positive electrode active material capable of intercalating/detaching lithium ions, a negative electrode including a negative active material capable of intercalating/deintercalating lithium ions, and an electrode with a microporous separator interposed between the positive electrode and the negative electrode It means a battery in which the non-aqueous electrolyte containing lithium ions is contained in the assembly. [11] The anode may include a conductive material to improve conductivity. As the conductive material, point-type conductive materials such as carbon black and linear conductive materials such as carbon nanotubes may be used. [12] Recently, in order to increase the energy density of the positive electrode, research has been conducted to increase the content of the positive electrode active material in the positive electrode active material layer. One method is to reduce the content of the conductive material and/or the binder in the positive electrode active material layer. In this case, when the amount of the conductive material decreases, the relative content of the positive electrode active material increases, so that the energy density of the positive electrode increases, but there is a problem that the conductivity in the positive electrode active material layer decreases. In addition, when the content of the conductive material and/or the binder is decreased, the adhesion (positive electrode adhesion) between the positive electrode active material layer and the current collector decreases, thereby deteriorating the life characteristics of the battery. [13] Therefore, an anode having sufficient anode adhesion while being able to increase the energy density of the anode is required. Detailed description of the invention Technical challenge [14] An object of the present invention is to provide a positive electrode having sufficient positive electrode adhesion while being able to increase the energy density of the positive electrode, and a secondary battery including the same and having improved capacity and resistance. Means of solving the task [15] According to an embodiment of the present invention, a current collector and a positive electrode active material layer disposed on the current collector are included, and the positive electrode active material layer includes a positive electrode active material, a conductive material, and a binder, and the conductive material is carbon black and carbon. Including at least any one of the nanotubes, wherein the binder includes polyvinylidene fluoride to which a functional group is bonded, the functional group includes a carboxy group, and in the polyvinylidene fluoride to which the functional group is bonded, the following formula 1 The content of the carboxy group calculated by is provided with a positive electrode of 1.1 mol% to 3.0 mol%. [16] [Equation 1] [17] [B/(A+B)] × 100 [18] A is the integral value of the peak of the unit derived from vinylidene fluoride when the 1 H NMR spectrum is measured for the polyvinylidene fluoride to which the functional group is bound, and B is 1 H for the polyvinylidene fluoride to which the functional group is bound. When measuring the NMR spectrum, it is the integral value of the peak of the carboxyl group. [19] According to another embodiment of the present invention, a secondary battery including the positive electrode is provided. Effects of the Invention [20] According to the present invention, since the positive electrode contains polyvinylidene fluoride containing an appropriate amount of functional groups together with carbon black and/or carbon nanotubes, the positive electrode adhesion of the positive electrode can be improved, and the volume of the positive electrode is expanded during charge and discharge. This can be suppressed. Thus, the capacity and resistance of the manufactured battery can be improved. Brief description of the drawing [21] 1 is a graph showing the volume change rate of the film when each of the binders used in manufacturing the positive electrode of Example 1 and Comparative Examples 1, 2, and 4 was prepared as a film, and the film was immersed in a high-temperature electrolyte. [22] 2 is a graph showing the positive electrode adhesion of the positive electrodes of Example 1 and Comparative Examples 1, 2, and 4; [23] 3 is a graph showing the positive electrode adhesion of the positive electrodes of Example 2 and Comparative Examples 3 and 5. [24] 4 is a graph showing a capacity retention rate and an increase rate of battery resistance in a battery including the positive electrodes of Example 1 and Comparative Examples 1, 2, and 4, respectively, when stored at a high temperature. Mode for carrying out the invention [25] Hereinafter, the present invention will be described in more detail to aid understanding of the present invention. At this time, terms or words used in the present specification and claims should not be construed as being limited to a conventional or dictionary meaning, and the inventor appropriately defines the concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of ​​the present invention based on the principle that it can be done. [26] In the present specification, the average particle diameter (D 50 ) may be defined as a particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve of the particles. The average particle diameter (D 50 ) can be measured using, for example, a laser diffraction method. In general, the laser diffraction method can measure a particle diameter of about several mm from a submicron region, and high reproducibility and high resolution results can be obtained. [27] [28] A positive electrode according to an embodiment of the present invention includes a current collector and a positive electrode active material layer disposed on the current collector, and the positive electrode active material layer includes a positive electrode active material, a conductive material, and a binder, and the conductive material is carbon black and Including at least any one of carbon nanotubes, the binder includes polyvinylidene fluoride to which a functional group is bonded, the functional group includes a carboxy group, and in the polyvinylidene fluoride to which the functional group is bonded, the following formula The content of the carboxyl group calculated by 1 is 1.1 mol% to 3.0 mol%. [29] [Equation 1] [30] [B/(A+B)]×100 [31] A is the integral value of the peak of the unit derived from vinylidene fluoride when the 1 H NMR spectrum is measured for the polyvinylidene fluoride to which the functional group is bound, and B is 1 H for the polyvinylidene fluoride to which the functional group is bound. When measuring the NMR spectrum, it is the integral value of the peak of the carboxyl group. [32] [33] The current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, as the current collector, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, or the like may be used. Specifically, a transition metal such as copper and nickel that adsorbs carbon well can be used as the current collector. [34] [35] The positive active material layer may be disposed on the current collector. The positive active material layer may be disposed on one or both surfaces of the current collector. The positive electrode active material layer may include a positive electrode active material, a conductive material, and a binder. [36] [37] The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may include a layered compound such as lithium cobalt oxide (LiCoO 2 ) or lithium nickel oxide (LiNiO 2 ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as formula Li 1+y1 Mn 2-y1 O 4 (0≦ y1 ≦0.33), LiMnO 3 , LiMn 2 O 3 , and LiMnO 2 ; Lithium copper oxide (Li 2 CuO 2 ); LiV 3 O 8 , V 2 O 5 , Cu 2 V 2 O 7Vanadium oxides such as; Ni site-type lithium nickel oxide represented by the formula LiNi 1-y2 M1 y2 O 2 (where M1 is Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and satisfies 0.01≦y2≦0.3); Formula LiMn 2-y3 M2 y3 O 2 (where M2 is Co, Ni, Fe, Cr, Zn or Ta, and satisfies 0.01≤y3≤0.1) or Li 2 Mn 3 M3O 8 (where M3 is Fe, A lithium manganese composite oxide represented by Co, Ni, Cu or Zn); Li in the formula may include LiMn 2 O 4 in which a part of Li is substituted with an alkaline earth metal ion, but is not limited thereto. Specifically, the positive electrode active material is Li[Ni a1 Mn b1 Co c1 ]O 2(0.50≤a1≤0.70, 0.15≤b1≤0.25, 0.15≤c1≤0.25, a1+b1+c1=1) and Li[Ni a2 Mn b2 Co c2 ]O 2 (0.72≤a2≤0.90, 0.05≤b2≤ It may be at least one of 0.14, 0.05≦c2≦0.14, and a2+b2+c2=1). The Li[Ni a1 Mn b1 Co c1 ]O 2 and Li[Ni a2 Mn b2 Co c2 ]O 2 have high energy density, and thus the capacity of the battery may be improved. [38] The average particle diameter (D 50 ) of the positive active material may be 3 μm to 20 μm, specifically 6 μm to 18 μm, and more specifically 9 μm to 16 μm. When the above range is satisfied, high-temperature life characteristics and output characteristics of the battery may be improved. [39] [40] The conductive material serves to reduce battery resistance by improving the conductivity of the positive active material layer. The conductive material may be at least one of carbon black and carbon nanotubes. [41] The carbon black may be in the form of secondary particles in which primary particles are aggregated. [42] The average particle diameter of the primary particles of the carbon black may be 5 nm to 500 nm, specifically 10 nm to 300 nm, and more specifically 20 nm to 100 nm. When the above range is satisfied, aggregation between conductive materials is suppressed, so that the carbon black may be uniformly dispersed in the positive electrode active material layer. At the same time, by preventing a decrease in battery efficiency due to the use of an excessively sized conductive material, deterioration in operating performance of the battery can be suppressed. The average particle diameter of the primary particles may be calculated by calculating an average of the particle diameters of 40 primary particles measured by TEM or SEM. [43] The average particle diameter (D 50 ) of the secondary particles of the carbon black may be 100 nm to 1000 nm, and specifically 200 nm to 600 nm. The average particle diameter means the average particle diameter of the secondary particles. When the above range is satisfied, the carbon black can be easily dispersed, and electrical conductivity in the positive electrode is improved, so that battery performance can be improved. [44] The BET specific surface area of ​​the carbon black may be 100m 2 /g to 150m 2 /g, specifically 110m 2 /g to 150m 2 /g. If the above range is satisfied, the conductivity of the carbon black is sufficient, and the resistance of the anode may be lowered. At the same time, since the viscosity of the positive electrode slurry can be prevented from increasing excessively, there is an advantage in transporting and coating the positive electrode slurry. [45] [46] The carbon nanotubes may be bundled carbon nanotubes. The bundled carbon nanotube may include a plurality of carbon nanotube units. Specifically, herein, the term'bundle type' refers to a bundle in which a plurality of carbon nanotube units are arranged side by side or entangled in substantially the same orientation, in which the axes of the length direction of the carbon nanotube units are substantially the same, unless otherwise stated. It refers to a secondary shape in the form of a bundle or rope. The carbon nanotube unit has a graphite sheet in the form of a cylinder having a nano-sized diameter, and has an sp 2 bonding structure. At this time, the characteristics of a conductor or a semiconductor may be expressed according to the angle and structure at which the graphite surface is rolled. Compared to the entangled type carbon nanotubes, the bundled carbon nanotubes may be uniformly dispersed when manufacturing the anode, and the conductive network within the anode may be formed smoothly, thereby improving the conductivity of the anode. [47] The carbon nanotube unit is a single-walled carbon nanotube (SWCNT, singlewalled carbon nanotube) unit, a double-walled carbon nanotube (DWCNT, double-walled carbon nanotube) unit, and a multi-walled carbon nanotube (MWCNT) according to the number of bonds forming the wall. , multi-walled carbon nanotube) can be classified as a unit. Specifically, the carbon nanotube unit may be a multi-walled carbon nanotube unit. The multi-walled carbon nanotube unit is preferable in that the energy required for dispersion is lower than that of the single-walled carbon nanotube unit and the double-walled carbon nanotube unit and has a dispersing condition at a level that is easy to control. [48] [49] The average diameter of the carbon nanotube unit may be 1 nm to 30 nm, specifically 3 nm to 26 nm, and more specifically 5 nm to 22 nm. When the above range is satisfied, the carbon nanotubes may be uniformly dispersed in the positive electrode slurry, and thus the conductivity of the prepared positive electrode may be improved. The average diameter may be an average value of the diameters of 40 carbon nanotube units measured by TEM or SEM. [50] The BET specific surface area of ​​the carbon nanotubes may be 100m 2 /g to 300m 2 /g, specifically 125m 2 /g to 275m 2 /g, and more specifically 150m 2 /g to 250m 2 /g I can. When the above range is satisfied, since the carbon nanotubes can be uniformly dispersed in the positive electrode slurry, the conductivity of the prepared positive electrode can be improved. The BET specific surface area may be measured through a nitrogen adsorption BET method. [51] Specifically, the conductive material may be any one of carbon black and carbon nanotubes, more preferably carbon nanotubes. When the conductive material is a carbon nanotube, a positive electrode adhesion may be further improved based on a high affinity and adsorption property between polyvinylidene fluoride to which a functional group is bonded and the carbon nanotube to be described later. [52] The conductive material may be included in an amount of 0.5% to 3.0% by weight in the positive active material layer, specifically 0.5% to 2.6% by weight, and more specifically 0.5% to 2.3% by weight. When the above range is satisfied, the conductivity of the positive electrode is secured, and the content of the positive electrode active material may be increased, so that the capacity of the positive electrode may be improved. In particular, when using carbon nanotubes as the conductive material, the carbon nanotubes may be included in 0.5% to 1.6% by weight, specifically 0.5% to 1.2% by weight in the positive electrode active material layer. [53] [54] The binder may include polyvinylidene fluoride to which a functional group is bonded. [55] The weight average molecular weight of the polyvinylidene fluoride to which the functional group is bonded may be 700,000 g/mol to 2,000,000 g/mol, specifically 710,000 g/mol to 1,800,000 g/mol, and more specifically 750,000 g/mol To 1,500,000 g/mol. When the above range is satisfied, since polyvinylidene fluoride to which the functional group is bonded is easily dissolved in an organic solvent, the viscosity of the positive electrode slurry formed during preparation of the positive electrode may be at an appropriate level. Accordingly, the coating of the positive electrode slurry is smooth, and the positive electrode adhesion of the manufactured positive electrode can be improved. In addition, when the above range is satisfied, the resistance of the manufactured battery can be prevented from excessively increasing. [56] Since the functional group has an interaction with the positive active material and/or the conductive material, when a shear force is applied to the positive electrode slurry, the phase stability and viscosity of the positive electrode slurry may be increased at a specific shear rate. Accordingly, when the positive electrode slurry is coated on the current collector and then dried, migration of the binder is suppressed so that the binder may be uniformly disposed in the positive electrode active material layer, and thus positive electrode adhesion may be increased. [57] Specifically, the functional group may include a carboxyl group. For example, the functional group may be a carboxyl group. Since the carboxyl group has a strong bonding force with the hydroxy group that is inevitably present on the surface of the current collector, the positive electrode adhesion can be further improved. Further, the functional group may further include at least one selected from the group consisting of a sulfonic acid group, a phosphoric acid group, and a hydroxy group. [58] The binder may be polyvinylidene fluoride to which the functional group is bonded. In other words, the binder does not contain polyvinylidene fluoride to which the functional group is not bonded, and may be composed of polyvinylidene fluoride to which the functional group is bonded. When the binder is composed of only polyvinylidene fluoride to which the functional group is not bonded, the interaction between the conductive material and the binder in the positive electrode slurry is weak, and when the positive electrode slurry is coated on the current collector, the migration of the binder ) Occurs. In addition, the affinity or adsorption of the carbon black or carbon nanotubes and the binder is insufficient. Accordingly, the positive electrode adhesive strength and battery life characteristics are deteriorated. When the polyvinylidene fluoride to which the functional group is not bonded is used in combination with the polyvinylidene fluoride to which the functional group is bonded, the content of the functional group in the polyvinylidene fluoride in the positive electrode active material layer, in particular, the content of carboxyl groups may be changed. In addition, since phase separation between the polyvinylidene fluoride to which the functional group is bonded and the polyvinylidene fluoride to which the functional group is not bonded may occur in the positive electrode slurry, the phase stability of the positive electrode slurry is reduced, and finally, positive electrode and battery performance This is degraded. Accordingly, the binder may be polyvinylidene fluoride to which the functional group is bonded. [59] In the polyvinylidene fluoride to which the functional group is bonded, the content of the carboxyl group calculated by the following formula 1 may be 1.1 mol% to 3.0 mol%, specifically 1.1 mol% to 2.5 mol%, and 1.2 It may be mol% to 2.0 mol%. [60] [Equation 1] [61] [B/(A+B)]×100 [62] A is the integral value of the peak of the unit derived from vinylidene fluoride when measuring a 1 H NMR (proton nuclear magnetic resonance) spectrum of the polyvinylidene fluoride to which the functional group is bound , and B is the functional group It is the integral value of the peak of the carboxyl group when 1 H NMR spectrum is measured for the bound polyvinylidene fluoride . [63] When the content of the carboxy group is less than 1.1 mol%, the bonding strength between the polyvinylidene fluoride and the current collector is insufficient, so that the positive electrode adhesion is excessively decreased. Accordingly, the positive electrode active material layer is easily detached from the current collector, and the lifespan characteristics of the battery decrease. On the other hand, when the content of the carboxy group exceeds 3.0 mol%, the affinity between the electrolyte and the binder is excessively increased, so that the binder or the positive electrode active material layer is excessively expanded by the electrolyte in a high-temperature environment when the battery is driven, resulting in a decrease in positive electrode adhesion. And the battery life characteristics may be deteriorated. [64] Therefore, using the content of the carboxy group in an amount of 1.1 mol% to 3.0 mol% corresponds to a preferable range capable of maintaining positive electrode adhesion, and accordingly, the life characteristics of the battery may be improved. Further, when the conductive material is a carbon nanotube, even if the carbon nanotube is used in a small amount, the positive electrode adhesion can be maintained. The mole% of the functional group may be measured by 1 H NMR (proton nuclear magnetic resonance). Specifically, after performing nuclear magnetic resonance spectrum analysis on the polyvinylidene fluoride to which the functional group is bound, the mole% of the functional group can be determined using the relative ratio of the integral value of the peak. [65] The polyvinylidene fluoride to which the functional group is bonded may be included in 0.5% to 3.0% by weight in the positive electrode active material layer, specifically 0.7% to 2.5% by weight, and more specifically 1.0% to 2.3% by weight. It may be included in weight percent. When the above range is satisfied, the positive electrode adhesive strength is maintained at a high level, and an increase in battery resistance due to an excessive amount of polyvinylidene fluoride to which the functional group is bonded can be prevented. [66] [67] The positive active material layer may further include a dispersant. The dispersant may serve to improve dispersibility of constituents in the positive electrode slurry. The dispersant may be at least one of nitrile butadiene rubber (NBR) and hydrogenated nitrile butadiene rubber (H-NBR), and specifically hydrogenated nitrile butadiene rubber. [68] The weight average molecular weight of the dispersant may be 100,000g/mol to 700,000g/mol, and specifically 200,000g/mol to 500,000g/mol. When the above range is satisfied, the conductive material can be uniformly dispersed in the positive electrode active material layer even with a small amount of the dispersant, and at the same time, the viscosity of the conductive material dispersion used for dispersing the conductive material can be suppressed from excessively increasing. The processability of manufacturing can be improved. [69] [70] A secondary battery according to another embodiment of the present invention includes a positive electrode; cathode; A separator interposed between the anode and the cathode; And an electrolyte, and the positive electrode is the same as the positive electrode of the above-described embodiment. Accordingly, a description of the anode is omitted. [71] [72] The negative electrode may include a negative electrode current collector and a negative active material layer disposed on one or both surfaces of the negative electrode current collector. [73] [74] The negative electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, as the negative electrode current collector, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. . Specifically, a transition metal such as copper and nickel that adsorbs carbon well can be used as the current collector. [75] The negative active material layer may include a negative active material, a negative conductive material, and a negative binder. [76] The negative active material may be graphite-based active material particles or silicon-based active material particles. The graphite-based active material particles may be one or more selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fiber, and graphitized mesocarbon microbead, and particularly, when using artificial graphite, rate characteristics may be improved. . The silicon-based active material particles are Si, SiO x (0