Method for manufacturing positive electrode for lithium secondary battery and positive electrode for lithium secondary battery manufactured thereby

Abstract

The present invention provides a method for manufacturing a cathode active material by: i) mixing a lithium transition metal oxide and a carbon-based material having a density of 0.05 g / cc or less by mechanofusion; ii) dry-mixing the positive electrode active material and the binder to form a dry mixture; and iii) A method for manufacturing a positive electrode for a lithium secondary battery, which includes a step of coating the dry mixture on a positive electrode current collector, and a positive electrode for a lithium secondary battery manufactured thereby.

Description

Technical Field

[0001] This application claims the benefit of Korean Patent Application No. 10-2020-0180753, filed with the Korean Intellectual Property Office on December 22, 2020, and the entire contents thereof are incorporated herein by reference.

[0002] The present invention relates to a method for manufacturing a positive electrode for a lithium secondary battery and a positive electrode for a lithium secondary battery manufactured thereby.

Background Art

[0003] As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among such secondary batteries, lithium secondary batteries having high energy density, voltage, long cycle life, and low self-discharge rate have been commercialized and widely used.

[0004] Lithium transition metal oxides are used as the positive electrode active material of lithium secondary batteries, and among them, lithium cobalt oxide of LiCoO2, which has a high operating voltage and excellent capacity characteristics, is mainly used. However, LiCoO2 has very poor thermal characteristics due to the destabilization of the crystal structure by delithiation and is still expensive, so there is a limit to its large-scale use as a power source in fields such as electric vehicles.

[0005] As materials to replace the LiCoO2, lithium manganese composite metal oxides (such as LiMnO2 or LiMn2O4), lithium iron phosphate compounds (such as LiFePO4), or lithium nickel composite metal oxides (such as LiNiO2) have been developed. Among these, research and development on lithium nickel composite metal oxides, which have a high reversible capacity of about 200 mAh / g and are easy to realize a large-capacity battery, has been carried out more actively. However, the LiNiO2 has lower thermal stability compared with LiCoO2, and when an internal short circuit occurs due to external pressure or the like in the charged state, there has been a problem that the cathode active material itself is decomposed, leading to battery rupture and ignition. Thus, as a method to improve the low thermal stability while maintaining the excellent reversible capacity of LiNiO2, lithium nickel cobalt metal oxides in which a part of nickel is replaced by cobalt have been developed.

[0006] However, recently, in view of the high cost of cobalt, active research has been carried out on Co-free (less) cathode materials or Ni-rich cathode materials containing an excessive amount of Ni.

[0007] On the other hand, the Co-free (less) cathode material or Ni-rich cathode material has problems that, compared with the Co-rich composition using an excessive amount of cobalt used conventionally, the electrical conductivity of the cathode active material is low and it is vulnerable to moisture. In order to solve such problems, there has been an attempt to form a carbon coating layer using pitch or the like on the surface of the above-described cathode material.

[0008] However, in the case of such a carbon coating layer, high-temperature heat treatment for carbonization must be accompanied, and during the high-temperature heat treatment, the carbon element on the surface reacts with oxygen on the surface of the cathode material and is reduced, whereby the oxidation number of the cathode active material is greatly changed, and thus there is a disadvantage that the performance of the cathode material is conversely deteriorated.

[0009] Therefore, there is a demand for the development of a cathode active material that can improve electrical conductivity and life characteristics by forming a thin and uniform carbon coating layer on the surface of the cathode active material without changing the oxidation number of the surface of the cathode material in the high-temperature heat treatment process.

Summary of the Invention

Problems to be Solved by the Invention

[0010] In the present invention, there are provided a method for manufacturing a cathode for a lithium secondary battery that manufactures a cathode active material containing a uniform carbon coating layer and utilizes this in a dry electrode process, and a cathode for a lithium secondary battery manufactured using the same.

Means for Solving the Problems

[0011] The present invention provides i) a step of mixing a lithium transition metal oxide and a carbon-based material having a density of 0.05 g / cc or less by a Mechanofusion method to form a cathode active material containing a carbon coating layer; ii) a step of dry-mixing the cathode active material and a binder to form a dry mixture; and iii) a step of applying the dry mixture onto a cathode current collector, and provides a method for manufacturing a cathode for a lithium secondary battery.

[0012] Further, the present invention provides a cathode including a cathode current collector and a cathode active material layer formed on the cathode current collector, wherein the cathode active material layer includes a lithium transition metal oxide and a carbon coating layer formed on the lithium transition metal oxide, and the carbon coating layer is formed by a method of mixing a carbon-based material having a density of 0.05 g / cc or less with the lithium transition metal oxide by a Mechanofusion method, and provides a cathode for a lithium secondary battery.

[0013] The present invention also provides a lithium secondary battery including the positive electrode for the lithium secondary battery.

Advantages of the Invention

[0014] According to the present invention, a thin and uniform carbon coating layer with an unchanged oxidation number can be formed on the surface of the lithium transition metal oxide, and by using this as a positive electrode active material, it is possible to manufacture a positive electrode dryly without using a conductive material or using a small amount thereof without a solvent.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0016] Hereinafter, the present invention will be described in more detail.

[0017] In this specification, the "specific surface area" is measured by the BET method, and specifically, it can be calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mini II of BEL Japan, Inc.

[0018] In this specification, the "dibutylphthalate adsorption" measures the amount of DBP adsorbed on the surface of the chain-shaped secondary structure in which the primary structures of the carbonaceous material are aggregated, and indicates how well the primary structures in the carbonaceous material are connected to form the secondary structure. The DBP absorption rate can be measured by mixing a certain amount of DBP, which is a plasticizer, with the carbonaceous material and measuring the change in torque generated by the impregnation of the plasticizer. Usually, the larger the DBP absorption rate, the more developed the secondary structure and the better the electrical conductivity.

[0019] In this specification, the "graphitization degree" means the degree to which amorphous carbon is partially or entirely changed into a highly crystalline graphitized structure, and it can be confirmed by using Raman spectroscopy analysis, by which the structure of the carbonaceous material can be analyzed. Among the Raman spectra of the carbonaceous material, the G band is a peak indicating the sp 2 bond, indicating a carbon crystal without structural defects. The D band is a peak indicating the sp 3 bond, and it increases when the atomic bond composed of the sp 2 bond is broken and becomes the sp 3 bond. Since such a D band increases when disorder or defects existing in the carbonaceous material are generated, the ratio (I G ) of the maximum peak intensity (I D ) of the D band to the maximum peak intensity (I D / I G ) of the G band can be calculated to quantitatively evaluate the degree of generation of disorder or defects.

[0020] In the carbonaceous material of the present invention, an aggregate in which primary particles are connected in a chain shape is defined as a secondary particle or a secondary structure. Specifically, sp 2A carbon structure having an atomic arrangement is disposed on spherical primary particles, and such primary particles are aggregates in the form of chain-shaped secondary particles or secondary structures in which the carbon structures of the primary particles are partially interconnected at the contacts and share a carbon unit structure in the form of a graphitic layer as shown in Fig. 4.

[0021] In the present invention, the "primary particle" of the lithium transition metal oxide particles means the smallest particle unit distinguishable as one lump when observing the cross-section of the lithium transition metal oxide through a scanning electron microscope (SEM), and it can be composed of one crystal grain or a plurality of crystal grains. In the present invention, the average particle size of the primary particles can be measured by a method of measuring the size of each particle distinguishable in the cross-section SEM image of the lithium transition metal oxide particles and obtaining their arithmetic mean value.

[0022] In the present invention, the "secondary particle" means a secondary structure formed by aggregation of a plurality of primary particles. The average particle size of the secondary particles can be measured using a particle size analyzer, and in the present invention, S3500 of Microtrac was used as the particle size analyzer.

[0023] In the present invention, the density of the carbonaceous material is the bulk density value obtained by the standard measurement method of JIS K 1649.

[0024] The method for manufacturing a positive electrode for a secondary battery according to the present invention includes steps i) to iii) described below, and each step will be specifically described below.

[0025] Method for manufacturing a positive electrode i) Step of forming a positive electrode active material In the step of forming the positive electrode active material of the present invention, a lithium transition metal oxide and a carbonaceous material having a density of 0.05 g / cc or less are mixed by a Mechanofusion method. Conventionally, a carbonaceous material was mainly introduced onto the surface of the positive electrode active material through high-temperature heat treatment. However, in this case, carbon reacts with oxygen on the surface of the lithium transition metal oxide and is reduced, and the oxidation number of the lithium transition metal oxide is greatly changed, resulting in a problem that the performance of the positive electrode active material is deteriorated.

[0026] Here, the present inventors introduced a Mechanofusion method, which is a physical treatment method using Nobilta equipment, not only to solve the above problems, but also found that the Mechanofusion method is more effective in forming a thin and uniform carbon coating layer compared to simple mechanical mixing using a Paint Shaker or the like.

[0027] In addition, various physical property conditions of the carbonaceous material suitable for the Mechanofusion method were confirmed, and through this, the electrochemical characteristics of the lithium secondary battery were improved.

[0028] At the same time, the present inventors utilized the positive electrode active material of the present invention in the production of dry electrodes, which have recently attracted attention in the electric vehicle market. Specifically, by applying the positive electrode active material having a uniformly formed carbon coating layer, it was found that the problems of diffusion of the conductive material and the binder with respect to the dry electrode using the fibrillation of a Polytetrafluoroethylene (PTFE) binder can be solved, and the dry electrode can be effectively realized.

[0029] That is, by applying the positive electrode active material on which the carbon coating layer is formed, in the dry mixing process, it becomes possible not to use a conductive material that is difficult to disperse uniformly in powder form or to use only a small amount thereof. As a result, the poor dispersibility of the conductive material powder can be greatly improved. In particular, it becomes possible to solve the problem of interference of the conductive material with the fibrillation of the polytetrafluoroethylene binder. Even without a wet process using a toxic organic solvent, the positive electrode can be manufactured only by a dry process, which is not only environmentally friendly but also can greatly reduce the cost of the electrode manufacturing process by omitting the drying process of the organic solvent.

[0030] The lithium transition metal oxide has crystal grains of 50 nm to 4,000 nm, preferably 50 nm to 2,000 nm. For example, the lithium transition metal oxide is in the form of secondary particles formed by aggregation of primary particles, or the lithium transition metal oxide is in the form of single particles.

[0031] In one embodiment of the present invention, when the lithium transition metal oxide is formed of secondary particles in which primary particles are aggregated, the energy density per unit volume of the electrode can be increased. The contact area between the lithium transition metal oxide and the electrolyte is large, the migration distance of lithium ions in the lithium transition metal oxide is short, and high capacity and high output characteristics can be easily exhibited. In addition, a uniform coating layer can be formed even on the uneven portions that are the interfaces between the primary particles of the lithium transition metal oxide, and the conductive network of the carbon coating layer can be maintained more firmly. Thereby, the conductivity of the positive electrode active material can be greatly improved, and the BET specific surface area of the finally manufactured positive electrode active material can also be kept low, and side reactions with the electrolyte due to an increase in the BET specific surface area can be prevented in advance.

[0032] In one embodiment of the present invention, when the lithium transition metal oxide is formed in the form of single particles composed of only primary particles, the surface is smoother than that of secondary particles, carbon coating is easier, and the rolling density is improved, thereby improving the structural stability of the electrode. However, compared with the positive electrode active material on the secondary particles, the form of single particles composed of only primary particles has a reduced contact area with the electrolyte and has somewhat inferior characteristics in the output characteristics of the battery.

[0033] The lithium transition metal oxide is usually used as a positive electrode active material and can be used without limitation as long as lithium ion insertion or desorption easily occurs during charge and discharge. For example, it is one or more selected from lithium-nickel cobalt-based composite oxides, lithium-manganese-based composite oxides, and lithium-iron phosphate-based composite oxides, and preferably a lithium-nickel cobalt-based composite oxide represented by the following Chemical Formula 1.

[0034] [Chemical Formula 1] Li 1+x (Ni a Co b Mn c M d )O2

[0035] In Chemical Formula 1, M is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Ru, Mg, P, B, Si, Na, K, and Mo, 0 ≦ x ≦ 0.2, 0.50 ≦ a ≦ 0.95, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.5, 0 ≦ d ≦ 0.5, and a + b + c + d = 1.

[0036] According to one embodiment of the present invention, a, b, c, and d are 0.60 ≦ a ≦ 0.80, 0.10 ≦ b ≦ 0.20, 0.10 ≦ c ≦ 0.20, and 0 ≦ d ≦ 0.05, respectively.

[0037] The lithium-manganese-based composite oxide is LiMnO2, LiMnO3, LiMn2O3, Li2MnO3, Li1+y1 Mn 2-y1 O4 (0 ≦ y1 ≦ 0.33), LiMn 2-y2 M y2 O4 (M is one or more selected from Ni, Co, Fe, P, S, Zr, Ti, and Al, and 0 ≦ y2 ≦ 2), LiMn 2-y3 M y3 O2 (M is one or more selected from Co, Ni, Fe, Cr, Zn, and Ta, and 0.01 ≦ y3 ≦ 0.1), or Li2Mn3MO8 (M is one or more selected from Fe, Co, Ni, Cu, and Zn).

[0038] The lithium-iron phosphate composite oxide can be represented by the following Chemical Formula 2.

[0039] [Chemical Formula 2] LiFe 1-x M x PO4

[0040] In the above Chemical Formula 1, M is one or more selected from Ni, Co, Mn, Al, Mg, Y, Zn, In, Ru, Sn, Sb, Ti, Te, Nb, Mo, Cr, Zr, W, Ir, and V, 0 ≦ x < 1.

[0041] The density of the carbonaceous material is 0.05 g / cc or less, specifically 0.01 g / cc to 0.05 g / cc, and more specifically 0.02 g / cc to 0.04 g / cc.

[0042] The BET specific surface area of the carbonaceous material is 300 m 2 / g or more, specifically 500 m 2 / g to 3,000 m 2 / g, and more specifically 700 m 2 / g to 2,500 m 2 / g.

[0043] In one embodiment of the present invention, the carbonaceous material has a porous hollow structure.

[0044] Such a hollow structure has relatively low crystallinity, and the hollow carbon tissue structure may be easily collapsed by mechanical physical surface treatment. In this case, it can be thinly and uniformly coated on the surface of the lithium transition metal oxide compared to other carbon-based substances with a dense structure.

[0045] Figure 1 compares the TEM photographs of carbon black with a hollow structure (left) and carbon black with a dense structure (right).

[0046] The porous hollow carbon-based substance according to the present invention has a chain shape and is in the form of secondary particles in which primary particles are aggregated. By having such a form, it contains pores inside and exhibits low crystallinity. When using this to form a carbon coating layer, due to the low crystallinity, while the structure of the carbon-based substance is collapsed by the externally applied force, the surface of the lithium transition metal oxide is crushed and adhered, and a carbon coating layer with a uniform thickness can be formed on the surface of the secondary particles of the lithium transition metal oxide.

[0047] The carbon-based substance is one or more selected from carbon black, carbon fiber, carbon nanotube, graphite, and graphene, and preferably carbon black.

[0048] The diameter of the primary particles of the carbon-based substance is 10 nm to 100 nm, preferably 30 nm to 60 nm. The diameter is the arithmetic mean value calculated after measurement through TEM equipment. When the size of the primary particles of the carbon-based substance satisfies the above range, it is advantageous for the formation of a uniform carbon coating layer.

[0049] The hollow carbon of the present invention includes a shell on the surface of the primary particles. When such a shell has a thickness of 10 nm or less from the surface of the primary particles, the carbon structure can have flexibility like few-layered graphene. As can be confirmed in (C) of FIG. 2, as the diameter of the primary particles increases, the thickness of the shell also tends to increase together.

[0050] In the present invention, when the diameter of the primary particles of the carbon-based material exceeds 100 nm, in controlling the thickness of the shell for the porous hollow carbon-based material, it is not easy to manufacture it thinly and uniformly with a target thickness of 10 nm or less. As a result, the flexibility of the carbon structure decreases, so the surface adhesion is not good even during mechanical surface coating treatment, and the structure of the carbon structure is not easily collapsed, making it difficult to achieve the desired thin and uniform carbon-based surface coating. Also, when the size of the primary particles of the carbon-based material is less than 10 nm, the specific surface area increases rapidly, so it becomes extremely difficult to disperse the powder due to the intermolecular attraction, and there may occur a problem that a partially aggregated carbon structure is coated in a state where it overlaps at that position, so that a uniform coating layer cannot be formed as a whole.

[0051] The DBP absorption rate (dibutyl phthalate adsorption) of the carbon-based material is 200 mL / 100 g or more, specifically 200 mL / 100 g to 800 mL / 100 g, and more specifically 400 mL / 100 g to 600 mL / 100 g.

[0052] In the present invention, the DBP absorption rate is measured for the DBP absorption amount on the surface of the chain-shaped secondary structure in which the primary structures of the carbon-based material are aggregated, and indicates how well-connected secondary structures the primary structures in the carbon-based material have. Usually, the larger the DBP absorption rate, the more developed the secondary structure and the better the electrical conductivity.

[0053] For example, when the DBP absorption rate is less than 200 mL / 100 g, since the chain-like secondary structure with respect to the carbonaceous material is not developed, it may be difficult to exhibit improved conductivity.

[0054] In one embodiment of the present invention, the graphitization degree (I D / I G ) of the carbonaceous material is 1.0 or more, specifically 1.0 to 2.0. In the case of a carbonaceous material with a graphitization degree of less than 1.0, generally having high crystallinity, carbon tissue structure collapse does not easily occur. Therefore, even when an external force is applied, the structure of the carbonaceous material on the surface of the lithium transition metal oxide does not collapse, and a highly crystalline carbon tissue is maintained. As a result, it cannot be smoothly coated on the surface and has an overall rough surface characteristic. Based on this, the BET specific surface area of the positive electrode active material increases. Also, it is not easy to form a firm and uniform carbon coating layer on the surface of the positive electrode active material by forming a carbon coating layer in a simple adsorption form on the surface of the lithium transition metal oxide without collapsing the tissue structure of the carbonaceous material, and there is a fatal problem that it may be easily desorbed from the surface. In particular, when the lithium transition metal oxide has a secondary particle form in which primary particles are aggregated, it is difficult to form a carbon coating layer on the uneven portions at the interfaces between the primary particles of the lithium transition metal oxide, so it is even less easy to form a uniform carbon coating layer.

[0055] Based on the total weight of the positive electrode active material, the content of the carbonaceous material is 0.1% by weight to 10.0% by weight, preferably 0.1% by weight to 5.0% by weight, more preferably 0.1% by weight to 3.0% by weight.

[0056] When the content of the carbonaceous material is within the above range, while forming a uniform carbon coating layer on the entire surface of the lithium transition metal oxide, the problem of forming an overly thick carbon coating layer can be prevented. When an overly thick carbon coating layer is formed, it can act as a resistance that obstructs the diffusion of lithium ions, and when applied to a battery, the input / output characteristics of the battery may be degraded.

[0057] Through the foregoing step i), a carbon coating layer is formed on the lithium transition metal oxide.

[0058] Specifically, the mechanical fusion method mixing is carried out using a nobilta facility under anhydrous process conditions (dry process) without further containing additives such as solvents and binders. Specifically, based on a 0.5 L capacity nobilta facility, the reactor can be stirred at a current of 3 to 15 A, a power of 0.2 W to 5.5 W, and a rotational speed of 300 rpm to 6,000 rpm. The mechanical fusion method may have different conditions of current, power, and rotational speed depending on the capacity of the facility. For example, when the capacity of the facility increases, the power increases and the rotational speed decreases. As a specific example, when using a 300 L capacity nobilta facility, it can be carried out while stirring at a power of 10 W to 200 W and a rotational speed of 50 rpm to 800 rpm. By introducing such a mechanical fusion method, the dispersibility of the particles is improved, and the carbon substances are separated at uniform intervals on the surface of the lithium transition metal oxide, and a uniform carbon coating layer can be formed on the surface of the lithium transition metal oxide by a high shearing force. Further, when the lithium transition metal oxide has a form of secondary particles in which primary particles are aggregated, a carbon coating layer can be formed not only on the surface of the secondary particles of the lithium transition metal oxide but also at the boundaries between the primary particles.

[0059] According to an embodiment of the present invention, the thickness of the carbon coating layer is 1 nm to 500 nm, preferably 1 nm to 300 nm, more preferably 1 nm to 100 nm.

[0060] ii) Step of forming a dry mixture Step ii) is carried out by dry-mixing the cathode active material and the binder formed through the foregoing step i). Specifically, the binder may include polytetrafluoroethylene (PTFE).

[0061] Specifically, the dry mixing means a mixing method without using a solvent, and can be carried out by repeating the process conditions of mixing at 10,000 rpm for 1 minute three times by utilizing the Laboratory Blender equipment of Waring. Generally, when manufacturing electrodes, a slurry form containing a solvent is used, so not only is an electrode drying process required, but particularly in the case of the positive electrode, there was also a risk of safety problems due to the toxicity of the organic solvent.

[0062] In the case of the present invention, since no solvent is used in the mixing process of the positive electrode active material and the binder, there are effects of simplifying the process, reducing costs, and improving safety. Furthermore, in the case of the positive electrode manufactured through the dry process, the porosity can be reduced compared to the positive electrode manufactured through the drying process after the wet process using a solvent, so the effect of improving the energy density can also be expected.

[0063] In one embodiment of the present invention, the binder may further contain polyvinylidene fluoride or an acrylic polymer.

[0064] Since the positive electrode active material of the present invention already has a carbon coating layer uniformly formed on its surface, the dry mixture may not contain a conductive material, or in some cases, may further contain a small amount of a conductive material for improving the formation of a conductive network between the active materials.

[0065] Based on the total weight of the dry mixture, the content of the positive electrode active material is 60% by weight to 99.9% by weight, preferably 80% by weight to 99% by weight. When the content of the positive electrode active material is within the above range, there is an effect of increasing the energy density per unit volume.

[0066] Based on the total weight of the dry mixture, the content of the binder is 0.1% by weight to 20% by weight, preferably 1% by weight to 10% by weight. When the content of the binder is within the above range, while increasing the energy density per unit volume, there is an effect of reducing the resistance of the electrode and maintaining the adhesion of the electrode.

[0067] Based on the total weight of the dry mixture, the content of the conductive material is 20% by weight or less, specifically 0.05% to 10% by weight, and may further be 0.05% to 5% by weight. Since an amount of conductive material powder less than that used during normal cathode formation is introduced, there is an effect of improving dispersibility.

[0068] In one embodiment of the present invention, after rolling the cathode active material at a pressure of 10 MPa to 100 MPa, the electrical conductivity of the measured powder is 5.0×10 -3 S / cm to 10.0×10 -3 S / cm, preferably 5.5×10 -3 S / cm to 8.5×10 -3 S / cm.

[0069] iii) A step of applying the dry mixture onto a cathode current collector The application in step iii) of the present invention can be carried out by a scattering method, through which the dry mixture can be arranged on the current collector with a uniform thickness.

[0070] The scattering method is carried out through a feeding roller to move the dry mixture, and when the dry mixture is applied to the current collector, a squeeze roll is used to maintain the thickness of the dry mixture layer during the coating process.

[0071] Since the dry mixture is disposed on the current collector in a powder state, the contact between the current collector and the dry mixture may increase compared to the case where it is disposed in a film form, whereby the positive electrode adhesion can be further improved. Further, the dry mixture can pass vertically between two horizontally arranged rolls and can also be manufactured in the form of a free-standing film. In this case, the electrode can be manufactured by laminating the manufactured film and the current collector through hot rolling. The current collector may be a porous foil having surface irregularities in order to strengthen the adhesion to the active material layer, or may be a foil coated with an adhesive layer such as polyvinylidene fluoride or an acrylic binder on the surface, and in order to improve the resistance due to the introduction of the adhesive layer, it may be a foil having an adhesive layer containing a carbon-based conductive material.

[0072] The dry mixture disposed on the current collector can be formed into a positive electrode active material layer having a desired target thickness through a further rolling process. Specifically, the positive electrode active material layer can be formed by rolling the current collector on which the dry mixture is disposed, and the rolling is to apply spinning to the dry mixture. When spinning is applied, a large shear force is applied with less force compared to the case where surface pressure is applied, and at the same time, the rolling process is also possible, so that the manufacturability of the electrode can be greatly improved.

[0073] The rolling step can include a step of rolling the current collector on which the dry mixture is disposed through a roll. Such a roll press method includes applying pressure with the roll while the two rolls are disposed above and below the current collector on which the dry mixture is disposed, and at the same time moving the current collector on which the dry mixture is disposed in the tangential direction and the horizontal direction of the two rolls.

[0074] Positive electrode The positive electrode for a lithium secondary battery according to the present invention is manufactured by the method for manufacturing a positive electrode for a lithium secondary battery described above. That is, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, the positive electrode active material layer includes a lithium transition metal oxide and a carbon coating layer formed on the lithium transition metal oxide, and the carbon coating layer is formed by a method of mixing a carbon-based material having a density of 0.05 g / cc or less with the lithium transition metal oxide by a Mechanofusion method.

[0075] Specifically, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material includes a lithium transition metal oxide and a carbon coating layer formed on the lithium transition metal oxide, and the carbon coating layer is formed by a method of mixing a carbon-based material having a density of 0.05 g / cc or less with the lithium transition metal oxide by a Mechanofusion method.

[0076] The components constituting the positive electrode can cite the description of the method for manufacturing a positive electrode for a lithium secondary battery described above.

[0077] Lithium secondary battery The lithium secondary battery of the present invention includes the positive electrode described above.

[0078] Specifically, the lithium secondary battery can be manufactured by a method generally used in the art, except for manufacturing the positive electrode according to the present invention, and includes the positive electrode manufactured according to the present invention, a negative electrode positioned opposite to the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode.

[0079] Hereinafter, specific descriptions will be made only for other configurations excluding the positive electrode.

[0080] Further, the lithium secondary battery can optionally further include a battery container for housing the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

[0081] In the lithium secondary battery, the negative electrode contains a negative electrode active material, and can be manufactured by coating a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, a solvent, etc. on a negative electrode current collector, followed by drying and rolling.

[0082] The negative electrode current collector generally has a thickness of 3 μm to 500 μm. Such a negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes to the battery. For example, copper; stainless steel; aluminum; nickel; titanium; fired carbon; those with the surface of copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.; or aluminum-cadmium alloy, etc. can be used. Also, similar to the positive electrode current collector, fine irregularities can be formed on the surface to strengthen the binding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven fabrics, etc.

[0083] Also, the negative electrode active material can include one or more selected from carbon materials that can reversibly intercalate / deintercalate lithium ions; metals or alloys of these metals and lithium; metal composite oxides; substances that can dope and undope lithium; lithium metal; and transition metal oxides.

[0084] The carbon material that can reversibly intercalate / deintercalate lithium ions is not particularly limited as long as it is a carbon-based negative electrode active material commonly used in lithium ion secondary batteries, and representative examples thereof include crystalline carbon, amorphous carbon, or these can be used together. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature fired carbon), hard carbon, mesophase pitch carbide, fired coke, etc.

[0085] As the metal or an alloy of these metals and lithium, a metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn, or an alloy of these metals and lithium can be used.

[0086] Examples of the metal composite oxide include PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3 (0 ≦ x ≦ 1), Li x WO2 (0 ≦ x ≦ 1), and Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8), and one or more selected from the group can be used.

[0087] Examples of the substance capable of doping and undoping lithium include Si, SiO x (0 < x ≦ 2), Si - Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn - Y (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), etc. Also, at least one of these can be mixed with SiO2 and used. The element Y can be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0088] Examples of the transition metal oxides include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, and the like.

[0089] The negative electrode active material can be contained in the negative electrode slurry at 80% by weight to 99% by weight based on the total weight of the solid content.

[0090] The binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can usually be added in a content of 1% by weight to 30% by weight based on the total weight of the solid content in the negative electrode slurry. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, styrene-butadiene rubber, fluorine rubber, or combinations thereof.

[0091] The conductive material can be added in a content of 1% by weight to 20% by weight based on the total weight of the solid content in the negative electrode slurry as a component for further improving the conductivity of the negative electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change to the battery. For example, carbon powders such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powders such as natural graphite, artificial graphite, single-layer or multi-layer carbon nanotubes, or graphene, graphite, etc. with a well-developed crystal structure; conductive fibers such as carbon fibers or metal fibers; conductive powders such as carbon fluoride powder, aluminum powder, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives can be used.

[0092] The solvent of the negative electrode slurry can include water; or organic solvents such as NMP and alcohol, and when including the negative electrode active material, binder, conductive material, etc., it can be used in an amount that results in a preferable viscosity. For example, it can be included such that the solid content concentration in the slurry containing the negative electrode active material, binder, and conductive material is 30% by weight to 80% by weight, preferably 40% by weight to 70% by weight.

[0093] On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a migration path for lithium ions. It is not particularly limited as long as it is usually used as a separator in a lithium secondary battery, and those having low resistance to the ion migration of the electrolyte and excellent moisture retention ability of the electrolyte solution are preferable.

[0094] Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as a polyethylene homopolymer, a polypropylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof can be used. Also, a normal porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fibers, polyethylene terephthalate fibers, etc. can be used. Further, a coated separator containing a ceramic component or a polymer substance to ensure heat resistance or mechanical strength can also be used, and it can be selectively used in a single-layer or multilayer structure.

[0095] Moreover, examples of the electrolyte used in the present invention can include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc. that can be used when manufacturing a lithium secondary battery, and are not limited thereto.

[0096] Specifically, the electrolyte can include an organic solvent and a lithium salt.

[0097] The organic solvent can be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethanol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may contain a double bond, aromatic ring, or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant, which can enhance the charge-discharge performance of the battery, and a linear carbonate compound having low viscosity (e.g., ethylmethylcarbonate, dimethylcarbonate, or diethylcarbonate) is more preferred. In this case, the cyclic carbonate and the chain carbonate are preferably mixed and used at a volume ratio of about 1:1 to about 1:9.

[0098] The lithium salt can be used without limitation, such as those commonly used in electrolytes for lithium secondary batteries. For example, the cation is Li + and the anion is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO4 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - , BF2C2O4 - , BC4O8 - , BF2C2O4CHF - , PF4C2O4 - , PF2C4O8 - , PO2F2 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - and can include at least any one selected from the group consisting of SCN - .

[0099] Specifically, the lithium salt can include one or more mixtures selected from the group consisting of LiN(FSO2)2 (Lithium bis(fluorosulfonyl)imide, LiFSI), LiPF6, LiClO4, LiBF4, LiTFSI, Lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), LiSO3CF3, LiPO2F2, Lithium bis(oxalate)borate (LiBOB), Lithium difluoro(oxalate)borate (LiFOB), Lithium difluoro(bisoxalato)phosphate (LiDFBP), Lithium tetrafluoro(oxalate)phosphate (LiTFOP), and Lithium fluoromalonato(difluoro)borate (LiFMDFB).

[0100] In addition to the electrolyte components, the electrolyte can selectively include additives as needed to prevent the electrolyte from decomposing in a high-voltage environment and causing electrode collapse, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and the effect of suppressing battery swelling at high temperatures.

[0101] The additives are one or more selected from cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, phosphorus compounds, nitrile compounds, amine compounds, silane compounds, benzene compounds, and lithium salt compounds.

[0102] The cyclic carbonate compound is one or more selected from vinylene carbonate (VC) and vinyl ethylene carbonate, specifically vinylene carbonate.

[0103] The halogen-substituted carbonate compound is fluoroethylene carbonate (FEC).

[0104] The sultone compound is a substance capable of forming a stable SEI film by a reduction reaction on the surface of the negative electrode, and is one or more compounds selected from 1,3-propanesultone (PS), 1,4-butanesultone, ethenesultone, 1,3-propenesultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone, specifically 1,3-propanesultone (PS).

[0105] The sulfate compound is a substance that can be electrically decomposed on the surface of the negative electrode to form a stable SEI film without cracks even during high-temperature storage, and is one or more selected from ethylene sulfate (Ethylene Sulfate; Esa), trimethylene sulfate (Trimethylene sulfate; TMS), or methyl trimethylene sulfate (Methyl trimethylene sulfate; MTMS).

[0106] The phosphorus compound is one or more selected from lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, tris(2,2,2-trifluoroethyl)phosphate, and tris(trifluoroethyl)phosphite.

[0107] The nitrile compound is one or more selected from succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile. Specifically, it is one or more selected from 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, and trifluorobenzonitrile containing a fluorine component.

[0108] The amine compound is one or more selected from triethanolamine and ethylenediamine, and the silane compound is tetravinylsilane.

[0109] The benzene compound is one or more selected from monofluorobenzene, difluorobenzene, trifluorobenzene, and tetrafluorobenzene.

[0110] The lithium salt compound is one or more compounds selected from LiPO2F2, lithium difluoro(oxalato)borate (LiODFB), LiBOB (lithium bis(oxalato)borate (LiB(C2O4)2)), lithium tetraphenylborate, and lithium borofluoride (LiBF4) as a compound different from the lithium salt contained in the non-aqueous electrolyte.

[0111] The content of the additive is 0.01% by weight to 5% by weight based on the total weight of the electrolyte.

[0112] The lithium secondary battery including the positive electrode manufactured through the method for manufacturing a positive electrode according to the present invention stably exhibits excellent discharge capacity, output characteristics, and lifespan characteristics, and thus is useful for portable devices such as mobile phones, notebook computers, digital cameras, etc., and for electric vehicle fields such as electric vehicles (EV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), etc.

[0113] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0114] The battery module or battery pack can be used as a power source for one or more medium and large-sized devices among power tools; automobiles including electric vehicles, hybrid electric vehicles, and plug-in hybrid electric vehicles; or power storage systems.

[0115] The outer shape of the lithium secondary battery of the present invention is not particularly limited, and can be, for example, a cylindrical shape, a rectangular shape, a pouch type, or a coin type using a can.

[0116] The lithium secondary battery according to the present invention can be preferably used not only as a battery cell for powering small devices, but also as a unit battery for medium and large-sized battery modules including a large number of battery cells.

[0117] Hereinafter, the present invention will be specifically described in detail with reference to examples.

[0118] [Example: Manufacture of Positive Electrode Active Material] In the following examples and comparative examples, carbon blacks with porous hollow structures having the characteristics shown in Table 1 below were used as carbon-based materials, respectively.

[0119]

Table 1

[0120] Example 1 LiNi 0.6 Co 0.2 Mn 0.2 300 g of a mixture containing 99% by weight of a lithium transition metal oxide represented by O2 and 1% by weight of the carbon black in Table 1 above was charged into a mechanofusion apparatus (Nobilta NOB-130, Hosokawa Micron Corporation) and treated at 3,000 rpm for 10 minutes to produce a positive electrode active material having a carbon coating layer with a thickness of 10 nm to 100 nm formed thereon.

[0121] Example 2 A positive electrode active material having a carbon coating layer with a thickness of 10 nm to 100 nm formed thereon was produced in the same manner as in Example 1 above, except that the carbon black in Table 1 above was used.

[0122] Example 3 A positive electrode active material having a carbon coating layer with a thickness of 10 nm to 100 nm formed thereon was produced in the same manner as in Example 1 above, except that the carbon black in Table 1 above was used.

[0123] Example 4 LiNi 0.6 Co 0.2 Mn 0.2 200 g of a mixture containing 99% by weight of a lithium transition metal oxide represented by O2 and 1% by weight of the carbon black in Table 1 above was charged into a mechanofusion apparatus (Nobilta NOB-130, Hosokawa Micron Corporation) and treated at 3,000 rpm for 10 minutes to produce a positive electrode active material having a carbon coating layer with a thickness of 10 nm to 100 nm formed thereon.

[0124] Comparative Example 1 LiNi 0.6 Co 0.2Mn 0.2 300 g of a mixture containing 99% by weight of a lithium transition metal oxide represented by O2 and 1% by weight of the carbon black in Table 1 above was put into a paint shaker (1400 Al classic shaker, manufactured by Red Devil) and mixed for 60 minutes to produce a positive electrode active material having a carbon coating layer with a thickness of 10 nm to 100 nm formed thereon.

[0125] Comparative Example 2 LiNi without a carbon coating layer formed 0.6 Co 0.2 Mn 0.2 A lithium transition metal oxide represented by O2 was used as the positive electrode active material.

[0126] Comparative Example 3 A positive electrode active material having a carbon coating layer with a thickness of 10 nm to 100 nm formed thereon was produced in the same manner as in Example 2 above, except that the carbon black in Table 1 above was used.

[0127] Experimental Example 1. (1) Confirmation of surface characteristics of positive electrode active material Figure 3 is an SEM photograph of the surfaces of the positive electrode active materials of Comparative Examples 2 and 3 and Example 3.

[0128] First, when comparing the surface of Example 3 with the surface of Comparative Example 2 where no carbon coating layer is formed, it can be confirmed that a film with a gray shadow is formed on the particle surface. Through this, it can be seen that the surface of the lithium transition metal oxide is uniformly coated with a carbon-based coating layer.

[0129] Also, when coating with dense carbon black whose density and BET specific surface area are outside the scope of the present invention (Comparative Example 3), even when a carbon coating layer is formed by the mechanofusion method, it can be confirmed that the carbon particles are not uniformly coated on the particle surface and are simply attached only in the form of aggregation at the interface uneven portions and the surface between the primary particles.

[0130] (2) Powder electrical conductivity of the positive electrode active material (S / cm) After putting 5 g of the positive electrode active material produced in Examples 1 to 4 and Comparative Examples 1 to 3 into a holder, it was rolled under a pressure of 62 MPa, and the powder electrical conductivity was measured using a 4-Probe powder electrical conductivity measurement electrode dedicated to powder (Mitsubishi Chemical, Powder Resistance System (MCP-PD51)). The measurement results are shown in Table 2 below.

[0131]

Table 2

[0132] Through Table 2 above, it can be confirmed that the powder electrical conductivity of the positive electrode active materials of Examples 1 to 4 produced according to the present invention was improved compared to Comparative Examples 1 to 3.

[0133] Experimental Example 2. Production of positive electrode and battery The positive electrode active materials produced in Examples 1 to 4 and Comparative Examples 1 to 3 were pre-treated (Pre-Mixing) by repeating the process conditions of mixing 97% by weight of the positive electrode active material, 1% by weight of a conductive material (Imerys, Super C65), and 2% by weight of a PTFE binder (Dupont, TEFLON (registered trademark) PTFE 60 TYPE) at 10,000 rpm for 1 minute using a Waring laboratory blender device 3 times. Thereafter, the corresponding dry mixture was treated with a self-made special mixer capable of applying a high shear force, a dry mix paste was produced through the PTFE fibrillation process, and a free-standing film was produced in a rolling process through an Inoue two-roll mill facility. The corresponding film was hot-rolled at 100°C and laminated together with an aluminum current collector (Primer Coated Al Foil, Dongwon Systems) having an adhesive layer in which PVDF and carbon black were mixed.

[0134] The positive electrode manufactured by a dry process without using any solvent was manufactured to a thickness of 200 μm through a multi-stage rolling process, and a coin half-cell was manufactured using lithium metal as the negative electrode. The electrolyte used was 1 M LiPF6, EC / EMC = 3 / 7 (volume ratio).

[0135] After manufacturing the coin half-cell battery by the method described above, it was charged at 0.1 C up to 4.3 V at 25 °C by CC / CV, charged at 0.005 C until cut-off, discharged at 0.1 C down to 3.0 V, and the initial charge and discharge capacity measurements and cell verification were carried out. Thereafter, the manufactured battery was charged at a constant current of 0.2 C up to 4.25 V with a 0.05 C cut-off at 25 °C. Then, it was discharged at a constant current of 0.2 C until it reached 2.5 V to measure the initial charge and discharge capacity. Thereafter, it was charged at a constant current of 0.2 C up to 4.25 V with a 0.05 C cut-off, and discharged at a constant current of 2.0 C until it reached 2.5 V. The above charging and discharging were regarded as one cycle, and two cycles were carried out. Thereafter, the 0.2 C discharge capacity and the discharge capacity at 2.0 C of the battery were measured and shown in Table 3 below.

[0136]

Table 3

[0137] Through the results in Table 3 above, it can be confirmed that for the cells applying the positive electrode active materials of Examples 1 to 4, the discharge capacity is superior to that of the cells applying the positive electrode active materials of Comparative Examples 1 to 3.

Claims

1. i) A step of forming a positive electrode active material including a carbon coating layer by mixing a lithium transition metal oxide and a carbonaceous material having a density of 0.05 g / cc or less by a mechanofusion method; ii) A step of dry-mixing the positive electrode active material and a binder to form a dry mixture; and iii) A step of applying the dry mixture onto a positive electrode current collector, wherein the step of i) is carried out in a dry process, and a method for manufacturing a positive electrode for a lithium secondary battery.

2. The method for manufacturing a positive electrode for a lithium secondary battery according to claim 1, wherein the carbonaceous material has a porous hollow structure.

3. The carbonaceous material has a BET specific surface area of 300 m ２ / g or more. The method for manufacturing a positive electrode for a lithium secondary battery according to claim 1 or 2.

4. The method for manufacturing a positive electrode for a lithium secondary battery according to any one of claims 1 to 3, wherein the primary particle diameter of the carbonaceous material is 10 nm to 100 nm.

5. The method for manufacturing a positive electrode for a lithium secondary battery according to any one of claims 1 to 4, wherein the DBP absorption rate (dibutyl phthalate adsorption) of the carbonaceous material is 200 mL / 100 g or more.

6. The graphitization degree (I Ｄ / I Ｇ ) of the carbonaceous material is 1.0 or more. The method for manufacturing a positive electrode for a lithium secondary battery according to any one of claims 1 to 5.

7. The method for manufacturing a positive electrode for a lithium secondary battery according to any one of claims 1 to 6, wherein the content of the carbonaceous material is 0.1% by weight to 5% by weight based on the total weight of the lithium transition metal oxide and the carbonaceous material.

8. The method for manufacturing a positive electrode for a lithium secondary battery according to any one of claims 1 to 7, wherein the lithium transition metal oxide is a lithium-nickel cobalt-based composite oxide represented by the following Chemical Formula 1: [Chemical Formula 1] Li １＋ｘ (Ni ａ Co ｂ Mn ｃ M ｄ )O ２ In the Chemical Formula 1, M is one or more selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Ru, Mg, P, B, Si, Na, K, and Mo, 0 ≦ x ≦ 0.2, 0.50 ≦ a ≦ 0.95, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.5, 0 ≦ d ≦ 0.5, and a + b + c + d = 1.

9. The method for manufacturing a positive electrode for a lithium secondary battery according to any one of claims 1 to 8, wherein the binder contains polytetrafluoroethylene.

10. After the positive electrode active material is rolled under a pressure of 10 MPa to 100 MPa, the measured powder electric conductivity is 5.0×10 －３ S / cm to 10.0×10 －３ S / cm. The method for manufacturing a positive electrode for a lithium secondary battery according to any one of claims 1 to 9.

11. A positive electrode including a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, wherein the positive electrode active material layer includes a lithium transition metal oxide and a carbon coating layer formed on the lithium transition metal oxide, The carbon coating layer has a thickness of 1 nm to 500 nm, the carbon coating layer is made of a carbonaceous material, the carbonaceous material has a BET specific surface area of 300 m 2 / g or more, the lithium transition metal oxide is a lithium-nickel cobalt-based composite oxide represented by the following Chemical Formula 1, [Chemical Formula 1] Li 1+x (Ni a Co b Mn c M d )O 2 In the Chemical Formula 1, M is one or more selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Ru, Mg, P, B, Si, Na, K, and Mo, 0 ≦ x ≦ 0.2, 0.50 ≦ a ≦ 0.95, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.5, 0 ≦ d ≦ 0.5, and a + b + c + d = 1, a positive electrode for a lithium secondary battery.

12. The positive electrode active material layer contains a binder, the binder contains polytetrafluoroethylene, the positive electrode for a lithium secondary battery according to Claim 11.

13. A lithium secondary battery including the positive electrode for a lithium secondary battery according to Claim 11.

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