Primer composition, and electrode and secondary battery comprising same

Abstract

The present invention provides a primer composition, and an electrode and a secondary battery comprising same, the primer composition comprising: a first conductive material; and a second conductive material, wherein the first conductive material includes a first carbon-based material having an average particle diameter of 0.01 μm or more to less than 0.1 μm, the second conductive material includes a second carbon-based material having an average particle diameter of more than 0.2 μm to 20 μm or less, and the solid content weight ratio of the first conductive material to the second conductive material is from 1:1 to 1:3.

Description

Primer composition, electrode and secondary battery comprising the same

[0001] The present invention relates to a primer composition, an electrode comprising the same, and a secondary battery.

[0002]

[0003] The rapid increase in fossil fuel use is driving a growing demand for alternative and clean energy sources. Secondary batteries are a prime example of electrochemical devices that utilize this electrochemical energy, and their applications are expanding. In particular, with the growing emphasis on global environmentally friendly policies, the electric vehicle market is experiencing rapid growth, and research and development on secondary batteries is actively underway both domestically and internationally.

[0004] A secondary battery is a battery that can be used repeatedly through the process of discharging, which converts chemical energy into electrical energy, and charging, which is the reverse process.

[0005] Secondary batteries generally use lithium transition metal oxides as positive electrode active materials and graphite-based materials as negative electrode active materials, and charging and discharging occur through repeated processes of intercalation / deintercalation of lithium ions from the positive electrode to the negative electrode.

[0006] However, during the charging and discharging process, separation between the electrode active materials or between the electrode active materials and the current collector can cause problems such as reduced charge and discharge capacity. The first problem is when applying small-sized active materials with a diameter of approximately 1 ㎛. In the case of NCM and NCA, which were widely used in domestic batteries, the particle size is large, approximately 10 ㎛, so they firmly adhere to the aluminum current collector even with a small amount of binder. On the other hand, LFP has a small particle size and requires a large amount of binder. The large amount of binder used in LFP electrodes causes a decrease in cell capacity and an increase in resistance. Therefore, a technology is required to firmly adhere to the substrate even with a small amount of binder. The second problem is when manufacturing the electrode using a dry process. The existing wet process dissolves PVDF binder in NMP solvent and adheres it to the substrate, whereas the dry process uses a binder such as PTFE that enables adhesion between the active material, conductive material, and current collector without the NMP solvent, which is harmful to the environment and human body. However, PTFE has the problem of poor adhesion to the substrate.

[0007] Therefore, a technology is required that can control the separation of the current collector and electrode active material to improve the structural stability of the electrode and thereby the performance of the battery.

[0008]

[0009] The present invention provides a primer composition having excellent electrode adhesion and improved charge / discharge characteristics and cycle characteristics, and an electrode and a secondary battery including the same.

[0010] In addition, the present invention provides a positive electrode having excellent adhesive strength and improved charge / discharge characteristics and cycle characteristics, and a secondary battery including the positive electrode.

[0011]

[0012] A primer composition according to the present invention comprises a first conductive material and a second conductive material, wherein the first conductive material comprises a first carbon-based material having an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, and the second conductive material comprises a second carbon-based material having an average particle diameter of more than 0.2 ㎛ and less than 20 ㎛, and a solid weight ratio of the first conductive material to the solid weight ratio of the second conductive material is 1:1 to 1:3.

[0013] In one embodiment of the present invention, the first carbon-based material and the second carbon-based material may be point-like carbon-based materials.

[0014] In one embodiment of the present invention, the first carbon-based material may have an oil absorption number of 100 ml / 100g to 300 ml / 100g.

[0015] In one embodiment of the present invention, the solid content weight of the first conductive material may be 3 wt% to 10 wt% relative to the total weight of the primer composition.

[0016] In one embodiment of the present invention, the solid content weight of the second conductive agent may be 3 wt% to 20 wt% relative to the total weight of the primer composition.

[0017] In one embodiment of the present invention, the first carbon-based material may include acetylene black.

[0018] In one embodiment of the present invention, the second carbon-based material may include graphite.

[0019] In one embodiment of the present invention, the primer composition is prepared at room temperature and a shear rate of 10 s -1 The viscosity may be from 100 cPs to 1,000 cPs.

[0020] In one embodiment of the present invention, the primer composition may have a content of transition metal impurities of less than 300 mg / kg according to inductively coupled plasma mass spectrometry.

[0021] An electrode according to the present invention includes a current collector, a primer layer formed on at least one surface of the current collector, and an active material layer formed on the primer layer, wherein the primer layer includes a primer composition, and the primer composition includes a first conductive material and a second conductive material, wherein the first conductive material includes a first carbon-based material having an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, and the second conductive material includes a second carbon-based material having an average particle diameter of more than 0.2 ㎛ and less than 20 ㎛, and a solid weight ratio of the first conductive material: the solid weight ratio of the second conductive material is 1:1 to 1:3.

[0022] In one embodiment of the present invention, the primer layer may have a thickness of 0.3 μm to 3 μm.

[0023] In one embodiment of the present invention, the electrode may have an adhesive strength of 25 gf / 20 mm to 35 gf / 20 mm according to the following measurement method.

[0024] [measurement method]

[0025] 1) The above electrode is punched to 20 mm × 120 mm to manufacture a specimen.

[0026] 2) After attaching double-sided tape to the slide glass, attach the above specimen and press it after rolling it back and forth 10 times using a 2 kg roller.

[0027] 3) Using a universal testing machine, the adhesive strength at which the specimen is peeled off from the slide glass is measured after pulling at a speed of 300 mm / min. At this time, the measurement section is 50 mm, and the measurement angle between the slide glass and the specimen is 90°.

[0028] A secondary battery according to the present invention comprises a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode comprises a primer layer, wherein the primer layer comprises a primer composition, wherein the primer composition comprises a first conductive material and a second conductive material, wherein the first conductive material comprises a first carbon-based material having an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, and wherein the second conductive material comprises a second carbon-based material having an average particle diameter of more than 0.2 ㎛ and less than 20 ㎛, and wherein a solid weight ratio of the first conductive material to the solid weight ratio of the second conductive material is 1:1 to 1:3.

[0029] In one embodiment of the present invention, the primer composition includes a dispersant, and the dispersant may include a polyvinyl compound.

[0030] In one embodiment of the present invention, the primer composition may further include a third conductive material having an average particle diameter of 0.1 µm or more and 0.3 µm or less or a fourth conductive material having an average particle diameter of 8 µm or more and 35 µm or less.

[0031] In one embodiment of the present invention, the sum of the solid weights of the first conductive agent and the third conductive agent may be 3 wt% to 10 wt% relative to the total weight of the primer composition.

[0032] In one embodiment of the present invention, the sum of the solid weights of the first conductive agent and the fourth conductive agent may be 5 wt% to 20 wt% relative to the total weight of the primer composition.

[0033] A primer composition according to the present invention comprises a first conductive agent and a dispersant, wherein the first conductive agent has an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, and the dispersant comprises a polyvinyl compound.

[0034] In one embodiment of the present invention, the primer composition may further include a second conductive material having an average particle diameter of 0.1 µm or more and 0.3 µm or less or a third conductive material having an average particle diameter of 8 µm or more and 35 µm or less.

[0035] In one embodiment of the present invention, the sum of the solid weights of the first conductive agent and the second conductive agent may be 3 wt% to 10 wt% relative to the total weight of the primer composition.

[0036] In one embodiment of the present invention, the sum of the solid weights of the first conductive agent and the third conductive agent may be 5 wt% to 20 wt% relative to the total weight of the primer composition.

[0037] In one embodiment of the present invention, the solid content weight of the dispersant may be 1 wt% to 5 wt% relative to the total weight of the primer composition.

[0038] In one embodiment of the present invention, the polyvinyl compound may include polyvinylpyrrolidone having a weight average molecular weight of 37,000 g / mol to 50,000 g / mol.

[0039] In one embodiment of the present invention, the primer composition may further include a binder, and the solid content weight of the binder may be 1 wt% to 10 wt% based on the total weight of the primer composition.

[0040] In one embodiment of the present invention, the binder may include a first water-soluble binder including an amide group and a carboxyl group.

[0041] In one embodiment of the present invention, the solid content weight of the first water-soluble binder may be 3 wt% to 10 wt% relative to the total weight of the primer composition.

[0042] In one embodiment of the present invention, the binder may include a second water-dispersible binder comprising an ester group.

[0043] In one embodiment of the present invention, the solid content weight of the second water-dispersible binder may be 5 wt% to 10 wt% relative to the total weight of the primer composition.

[0044] In one embodiment of the present invention, the binder may include a third water-soluble binder including a polyvinyl-based compound having a weight average molecular weight of 2,000,000 g / mol to 3,000,000 g / mol.

[0045] In one embodiment of the present invention, the solid content weight of the third water-soluble binder may be 5 wt% to 10 wt% relative to the total weight of the primer composition.

[0046] In one embodiment of the present invention, the primer composition is prepared at room temperature and a shear rate of 10 s -1 The viscosity may be from 100 cPs to 1,000 cPs.

[0047] An electrode according to the present invention comprises a current collector, a primer layer formed on at least one surface of the current collector, and an active material layer formed on the primer layer, wherein the primer layer comprises a primer composition, the primer composition comprises a first conductive material, and a dispersant, wherein the first conductive material has an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, and the dispersant comprises a polyvinyl-based compound.

[0048] In one embodiment of the present invention, the electrode may have an adhesive strength of 10 gf / 20 mm to 25 gf / 20 mm according to the following measurement method.

[0049] A secondary battery according to the present invention comprises a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode comprises a primer layer, the primer layer comprises a primer composition, the primer composition comprises a first conductive material, and a dispersant, the first conductive material having an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, and the dispersant comprises a polyvinyl-based compound.

[0050] In one embodiment of the present invention, the secondary battery may have a voltage range of 0 V to 5.5 V at 0.05 mA when measured by linear sweep voltammetry.

[0051] A positive electrode according to the present invention includes a current collector, a primer layer formed on at least one surface of the current collector, and a positive electrode active material layer formed on the primer layer, wherein the primer layer includes the primer composition, the primer layer includes a fifth conductive material having an average particle diameter of less than 5 ㎛, and the positive electrode active material layer includes a first positive electrode active material having an average particle diameter of less than 5 ㎛, and can satisfy the following equation 1.

[0052] [Formula 1]

[0053] 5% < (X1 / A1) × 100 < 35%

[0054] The above A1 is the average particle diameter (㎛) of the first positive electrode active material, and the above X1 is the average particle diameter (㎛) of the fifth conductive material.

[0055] In one embodiment of the present invention, the fifth conductive material may include carbon black.

[0056] In one embodiment of the present invention, the solid content weight of the fifth conductive material may be 3 wt% to 15 wt% relative to the total weight of the primer layer.

[0057] A positive electrode according to the present invention comprises a current collector, a primer layer formed on at least one surface of the current collector, and a positive electrode active material layer formed on the primer layer, wherein the primer layer comprises a first conductive material having an average particle diameter of less than 5 μm, and the positive electrode active material layer comprises a first positive electrode active material having an average particle diameter of less than 5 μm, and satisfies the following equation 1.

[0058] [Formula 1]

[0059] 5% < (X1 / A1) × 100 < 35%

[0060] The above A1 is the average particle diameter (㎛) of the first positive electrode active material, and the above X1 is the average particle diameter (㎛) of the first conductive material.

[0061] In one embodiment of the present invention, A1 may be 0.6 μm or more and 1.8 μm or less.

[0062] In one embodiment of the present invention, the first positive electrode active material may include lithium iron oxide.

[0063] In one embodiment of the present invention, the first conductive material may include carbon black.

[0064] In one embodiment of the present invention, the solid content weight of the first conductive material may be 3 wt% to 15 wt% relative to the total weight of the primer layer.

[0065] In one embodiment of the present invention, the adhesive strength according to the following measurement method 1 may be 15 gf / 20 mm or more and 30 gf / 20 mm or less.

[0066] [Measurement Method 1]

[0067] 1) The above anode is punched to 20 mm × 120 mm to manufacture a specimen.

[0068] 2) After attaching double-sided tape to the slide glass, attach the above specimen and press it after rolling it back and forth 10 times using a 2 kg roller.

[0069] 3) Using a universal testing machine, the adhesive strength at which the specimen is peeled off from the slide glass is measured after pulling at a speed of 300 mm / min. At this time, the measurement section is 50 mm, and the measurement angle between the slide glass and the specimen is 90°.

[0070] The positive electrode of the present invention includes a current collector, a primer layer formed on at least one surface of the current collector, and a positive electrode active material layer formed on the primer layer, wherein the primer layer includes a second conductive material having an average particle diameter of 5 ㎛ or more and a third conductive material having an average particle diameter different from that of the second conductive material, and the positive electrode active material layer includes a second positive electrode active material having an average particle diameter of 5 ㎛ or more, and satisfies the following equations 2 and 3.

[0071] [Formula 2]

[0072] 100 % < (X2 / A2) × 100 < 300 %

[0073] [Formula 3]

[0074] 0.05 % < (X3 / X2) × 100 < 0.7 %

[0075] The above A2 is the average particle diameter (㎛) of the second positive electrode active material, the above X2 is the average particle diameter (㎛) of the second conductive material, and the above X3 is the average particle diameter (㎛) of the third conductive material.

[0076] In one embodiment of the present invention, A2 may be 8 μm or more and 12 μm or less.

[0077] In one embodiment of the present invention, the second positive electrode active material may include lithium nickel cobalt manganese oxide.

[0078] In one embodiment of the present invention, the second conductive material may include graphite.

[0079] In one embodiment of the present invention, the third conductive agent may include acetylene black.

[0080] In one embodiment of the present invention, the solid weight ratio of the second conductive material to the solid weight ratio of the third conductive material may be 3:1 to 1:1.

[0081] In one embodiment of the present invention, the sum of the solid weight of the second conductive material and the solid weight of the third conductive material may be 3 wt% to 15 wt% relative to the total weight of the primer layer.

[0082] In one embodiment of the present invention, the adhesive strength according to the following measurement method 2 may be greater than 30 gf / 20 mm and less than or equal to 45 gf / 20 mm.

[0083] [Measurement Method 2]

[0084] 1) The above anode is punched to 20 mm × 120 mm to manufacture a specimen.

[0085] 2) After attaching double-sided tape to the slide glass, attach the above specimen and press it after rolling it back and forth 10 times using a 2 kg roller.

[0086] 3) Using a universal testing machine, the adhesive strength at which the specimen is peeled off from the slide glass is measured after pulling at a speed of 300 mm / min. At this time, the measurement section is 50 mm, and the measurement angle between the slide glass and the specimen is 90°.

[0087] A secondary battery according to the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode includes a current collector, a primer layer formed on at least one surface of the current collector, and a positive electrode active material layer formed on the primer layer, wherein the primer layer includes a first conductive material having an average particle diameter of less than 5 ㎛, and the positive electrode active material layer includes a first positive electrode active material having an average particle diameter of less than 5 ㎛, and satisfies the following equation 1.

[0088] [Formula 1]

[0089] 5% < (X1 / A1) × 100 < 35%

[0090] The above A1 is the average particle diameter (㎛) of the first positive electrode active material, and the above X1 is the average particle diameter (㎛) of the first conductive material.

[0091] A secondary battery according to the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode includes a current collector, a primer layer formed on at least one surface of the current collector, and a positive electrode active material layer formed on the primer layer, wherein the primer layer includes a second conductive material having an average particle diameter of 5 ㎛ or more and a third conductive material having a different average particle diameter from the second conductive material, and the positive electrode active material layer includes a second positive electrode active material having an average particle diameter of 5 ㎛ or more, and satisfies the following equations 2 and 3.

[0092] [Formula 2]

[0093] 100 % < (X2 / A2) × 100 < 300 %

[0094] [Formula 3]

[0095] 0.05 % < (X3 / X2) × 100 < 0.7 %

[0096] The above A2 is the average particle diameter (㎛) of the second positive electrode active material, the above X2 is the average particle diameter (㎛) of the second conductive material, and the above X3 is the average particle diameter (㎛) of the third conductive material.

[0097]

[0098] In the electrode according to the present invention, a primer layer is formed between the current collector and the active material layer, thereby improving the interfacial adhesive force between the current collector and the active material layer, thereby improving the electrode detachment phenomenon.

[0099] In addition, the primer composition according to the present invention can reduce the ratio of the binder by including two types of carbon-based materials having different average particle diameters in a specific ratio, thereby reducing the thickness of the primer layer, thereby improving electrical conductivity without reducing adhesive strength.

[0100] Furthermore, the primer composition according to the present invention utilizes dot-shaped conductive materials instead of linear conductive materials, thereby improving dispersibility, thereby increasing manufacturing process efficiency and enhancing compatibility with other materials. Furthermore, impurities such as iron elements can be reduced, thereby preventing internal short-circuiting of battery cells during charging and discharging, thereby improving secondary battery performance.

[0101] In the electrode according to the present invention, a primer layer is formed between the current collector and the active material layer, thereby improving the interfacial adhesive force between the current collector and the active material layer, thereby improving the electrode detachment phenomenon.

[0102] In addition, the primer composition according to the present invention includes a conductive material having an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛ and a polyvinyl-based compound as a dispersant, so that the interfacial adhesive strength between the current collector and the active material layer can be improved, and the dispersibility of the conductive material can be improved, so that the electrical conductivity can be improved.

[0103] In addition, the primer composition according to the present invention includes a water-soluble binder containing an amide group and a carboxyl group, a water-dispersible binder containing an ester group, or a binder containing a polyvinyl-based compound having a weight average molecular weight of 2,000,000 g / mol to 3,000,000 g / mol in a specific ratio, thereby improving compatibility with a dispersant, thereby increasing efficiency in the manufacturing process, and reducing the ratio of the binder, thereby improving the initial efficiency, life characteristics, and high-rate discharge characteristics of a secondary battery.

[0104] The positive electrode according to the present invention and the secondary battery including the same have a primer layer formed between the current collector and the positive electrode active material layer, thereby improving the interfacial adhesive force between the current collector and the positive electrode active material layer, thereby improving the electrode detachment phenomenon.

[0105] In addition, the present invention can improve the interfacial adhesive strength between the current collector and the positive electrode active material layer by deriving an optimal combination of conductive materials having different average particle diameters and / or a different average particle diameter range of conductive materials included in the primer layer according to the average particle diameter of the positive electrode active material included in the positive electrode active material layer.

[0106] In addition, the present invention can reduce the ratio of binder in the primer layer compared to the conventional method, so that the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery can be improved.

[0107]

[0108] The structural or functional descriptions of the embodiments disclosed in this specification or application are merely illustrative for the purpose of explaining embodiments according to the technical idea of ​​the present invention, and the embodiments according to the technical idea of ​​the present invention can be implemented in various forms other than the embodiments disclosed in this specification or application, and the technical idea of ​​the present invention is not construed as being limited to the embodiments described in this specification or application.

[0109] In addition, when a component is referred to as "including" in this specification or application, this does not mean that other components are excluded, but rather that other components may be included, unless otherwise specifically stated. In addition, all numerical ranges indicating physical property values, dimensions, etc. of the components described in this specification or application should be understood to be modified by the term "about" in all cases unless otherwise specified. In addition, "ppm" in this specification or application means based on weight. In addition, the description of "A and / or B" in this specification or application means "A, B, or, A and B."

[0110]

[0111] <First embodiment - primer composition, electrode containing the same, and secondary battery>

[0112] Hereinafter, a primer composition according to the present invention, an electrode including the same, and a secondary battery are described.

[0113]

[0114] Typically, during electrode manufacturing, an electrode active material layer is formed on a current collector. However, due to insufficient interfacial adhesive strength between the current collector and the electrode active material layer, a problem of electrode detachment occurs. To improve this problem, a primer layer is formed between the current collector and the electrode active material layer to improve the interfacial adhesive strength between the current collector and the electrode active material layer.

[0115] When the above primer layer is formed, the interfacial adhesive strength can be improved, but a problem of reduced electrical conductivity occurs due to an increase in the physical distance between the current collector and the electrode active material layer.

[0116] As a method for improving electrical conductivity, a conductive material was mixed into the primer composition and used, but in the case of a dot-shaped conductive material, the adhesive strength was low, so the ratio of binder had to be increased, which caused an increase in the thickness of the primer layer, which reduced electrical conductivity and increased resistance, resulting in a problem of deterioration in the performance of the secondary battery.

[0117] Meanwhile, a method of mixing and using linear conductive materials as a conductive material was also considered, but carbon nanotubes, an example of linear conductive materials, have significantly poor dispersibility, making it difficult to mix with other materials, and problems such as reduced economic feasibility and manufacturing process efficiency occurred.

[0118] Accordingly, the primer composition according to the present invention includes two types of point-shaped carbon materials having different average particle diameters in a specific ratio, thereby improving adhesive strength without increasing the ratio of binder, improving the electron transfer path between the current collector and the electrode active material layer, thereby improving electrical conductivity, and by not including a linear conductive material, improving economic feasibility and efficiency in the manufacturing process.

[0119] The primer composition according to the present invention includes a conductive material. The conductive material can improve electrical conductivity between the current collector and the active material layer.

[0120] The above conductive material includes a first conductive material and a second conductive material, wherein the first conductive material includes a first carbon-based material having an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, and the second conductive material includes a second carbon-based material having an average particle diameter of 0.2 ㎛ or more and 20 ㎛ or less.

[0121] The above average particle diameter refers to the particle diameter at the n% point of the cumulative particle number distribution, and refers to the particle diameter at the 50% point of the cumulative particle number distribution. The above average particle diameter can be measured using a laser diffraction method. Specifically, the particle size distribution can be calculated by dispersing the measurement target material in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device, and then measuring the difference in diffraction pattern according to particle size when the particles pass through a laser beam.

[0122] The solid weight ratio of the first conductive material to the solid weight ratio of the second conductive material may be 1:1 to 1:3, 1:1.2 to 1:3, 1:1.5 to 1:3, or 1:1.5 to 1:2.5.

[0123] The above primer composition includes a first conductive material including a first carbon-based material having an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛ and a second conductive material including a second carbon-based material having an average particle diameter of more than 0.2 ㎛ and less than 20 ㎛ in the above ranges, so that the first carbon-based material having a relatively small particle diameter can fill the empty space between the second carbon-based material having a relatively large particle diameter, so that the ratio of the binder can be reduced, and accordingly, the thickness of the primer layer can be reduced, so that electrical conductivity can be improved without lowering the adhesive strength.

[0124] The average particle diameter of the first carbon-based material may be 0.01 ㎛ or more and less than 0.1 ㎛, 0.01 ㎛ or more and 0.09 ㎛ or less, 0.02 ㎛ or more and 0.09 ㎛ or less, 0.02 ㎛ or more and 0.08 ㎛ or less, or 0.03 ㎛ or more and 0.07 ㎛ or less.

[0125] The average particle diameter of the second carbon-based material may be greater than 0.2 µm and less than or equal to 20 µm, greater than or equal to 1 µm and less than or equal to 20 µm, greater than or equal to 5 µm and less than or equal to 20 µm, greater than or equal to 10 µm and less than or equal to 20 µm, or greater than or equal to 15 µm and less than or equal to 20 µm.

[0126] When the above range is satisfied, the first carbon-based material can more efficiently fill the empty space between the second carbon-based material, so that the adhesive strength and electrical conductivity can be further improved.

[0127] The first carbon-based material and the second carbon-based material may be spherical carbon-based materials. By using a spherical carbon-based material instead of a needle-type carbon-based material as a conductive material, the primer composition can improve dispersibility, thereby increasing efficiency in the manufacturing process and improving compatibility with other materials. In addition, impurities such as iron elements can be reduced, thereby improving electron transfer paths and enhancing electrical conductivity, thereby improving the performance of the secondary battery.

[0128] The solid content weight of the first conductive agent may be 3 wt% to 10 wt%, 4 wt% to 10 wt%, 4.5 wt% to 10 wt%, or 5 wt% to 10 wt% relative to the total weight of the primer composition.

[0129] The solid content weight of the second conductive agent may be 3 wt% to 20 wt%, 5 wt% to 20 wt%, 6 wt% to 20 wt%, or 6 wt% to 15 wt% relative to the total weight of the primer composition.

[0130] When the above range is satisfied, the interfacial adhesion between the current collector and the active material layer is not reduced, and electrical conductivity can be improved.

[0131] The first carbon-based material may have an oil absorption number of 100 ml / 100g to 300 ml / 100g, 100 ml / 100g to 200 ml / 100g, 100 ml / 100g to 150 ml / 100g, or 110 ml / 100g to 150 ml / 100g.

[0132] When the above range is satisfied, compatibility with other materials is improved, and the primer composition can exhibit an appropriate viscosity, thereby improving dispersibility.

[0133] The first carbon-based material may include acetylene black. The first carbon-based material may have a BET specific surface area of ​​1 m 2 / g to 200 m 2 / g, 1 m 2 / g to 150 m 2 / g, 1 m 2 / g to 100 m 2 / g, 10 m 2 / g to 100 m 2 / g, or 20 m 2 / g to 100 m 2 / g of acetylene black. The BET specific surface area can be measured from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mini II of BEL Japan.

[0134] The second carbon-based material may include graphite.

[0135] The above second carbon-based material has a BET surface area of ​​1 m 2 / g to 50 m 2 / g, 1 m 2 / g to 40 m 2 / g, 1 m 2 / g to 30 m 2 / g, 1 m 2 / g to 20 m 2 / g, or 1 m2 / g to 10 m 2 / g may contain graphite.

[0136] The above primer composition is prepared at room temperature and a shear rate of 10 s -1 The viscosity may be 100 cPs to 1,000 cPs, 150 cPs to 1,000 cPs, 150 cPs to 900 cPs, or 150 cPs to 850 cPs. When the above viscosity range is satisfied, the phenomenon of cracks or pinholes occurring on the electrode surface can be minimized, and the side ring phenomenon in which the active material layer is applied with a high thickness at the end can be suppressed.

[0137] The above primer composition may have a content of transition metal impurities of less than 300 mg / kg, less than 250 mg / kg, less than 200 mg / kg, less than 150 mg / kg, or less than 130 mg / kg according to inductively coupled plasma mass spectrometry. When the above range is satisfied, the electron movement path is improved, thereby improving electrical conductivity, and thus the performance of the secondary battery may be improved.

[0138] The above transition metal impurities may include at least one selected from the group consisting of cobalt, chromium, copper, iron, manganese, nickel, and zinc.

[0139] The content of cobalt as the above transition metal impurity may be less than 250 mg / kg, less than 200 mg / kg, less than 180 mg / kg, less than 150 mg / kg, or less than 140 mg / kg.

[0140] The content of chromium as the transition metal impurity may be less than 10 mg / kg, less than 8 mg / kg, less than 5 mg / kg, less than 3 mg / kg, or less than 1 mg / kg.

[0141] The content of copper as the transition metal impurity may be less than 5 mg / kg, less than 3 mg / kg, less than 1 mg / kg, less than 0.5 mg / kg, or less than 0.12 mg / kg.

[0142] The content of iron as the transition metal impurity may be less than 100 mg / kg, less than 50 mg / kg, less than 30 mg / kg, less than 20 mg / kg, or less than 10 mg / kg. When the conductive material includes carbon nanotubes, which are an example of linear conductive materials, the content of iron may increase due to residues of the iron catalyst used in the manufacturing process of the carbon nanotubes, which may result in a decrease in electrical conductivity. Accordingly, the conductive material of the present invention includes point-shaped conductive materials instead of carbon nanotubes, and the content of impurities is minimized without decreasing electrical conductivity.

[0143] The content of the manganese as the transition metal impurity may be less than 2 mg / kg, less than 1 mg / kg, less than 0.5 mg / kg, less than 0.1 mg / kg, or less than 0.03 mg / kg.

[0144] The content of nickel as the transition metal impurity may be less than 3 mg / kg, less than 2 mg / kg, less than 1 mg / kg, less than 0.5 mg / kg, or less than 0.28 mg / kg.

[0145] The content of zinc as the transition metal impurity may be less than 2 mg / kg, less than 1 mg / kg, less than 0.5 mg / kg, less than 0.3 mg / kg, or less than 0.15 mg / kg.

[0146] The primer composition may include a solvent. The components included in the primer composition may be dispersed by the solvent. The solvent may be an aqueous solvent. The aqueous solvent may be distilled water. The solvent may be an aqueous solvent, an organic solvent, or a mixture thereof.

[0147] The organic solvent may be an amide polar organic solvent such as dimethylformamide (DMF), diethyl formamide, dimethyl acetamide (DMAc), or N-methyl pyrrolidone (NMP); an alcohol such as methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol (n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl-2-propanol (tert-butanol), pentanol, hexanol, heptanol, or octanol; a glycol such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, or hexylene glycol; a polyhydric alcohol such as glycerin, trimethylolpropane, pentaerythritol, or sorbitol; Examples thereof include glycol ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, or tetraethylene glycol monobutyl ether; ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, or cyclopentanone; esters such as ethyl acetate, γ-butyl lactone, and ε-propiolactone; and any one or a mixture of two or more thereof may be used.

[0148] The above primer composition may include a dispersant.

[0149] The dispersibility of the first conductive agent and the second conductive agent can be improved by the above dispersant.

[0150] When the solvent is an aqueous solvent, the dispersant may be one or a mixture of two or more of carboxymethyl cellulose, polyvinylpyrrolidone (PVP), acrylic resin emulsion, water-soluble acrylic polymer, styrene emulsion, silicone emulsion, acrylic silicone emulsion, fluororesin emulsion, EVA emulsion, vinyl acetate emulsion, vinyl chloride emulsion, and urethane resin emulsion.

[0151] When the solvent is an organic solvent, the dispersant may be one or a mixture of two or more of polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), polyvinylidene fluoride (PVDF), acrylic resin, alkyd resin, and urethane resin.

[0152] The content of the dispersant may be 1 part by weight to 50 parts by weight, 10 parts by weight to 50 parts by weight, 15 parts by weight to 50 parts by weight, or 15 parts by weight to 45 parts by weight relative to 100 parts by weight of the total of the first conductive material and the second conductive material.

[0153] When the above range is satisfied, the dispersibility of the first and second conductive materials can be further improved.

[0154] The above primer composition may include a binder.

[0155] The adhesive strength between the first conductive material and the second conductive material or between the components included in the primer composition may be improved by the binder. In addition, the adhesive strength between the current collector and the active material layer may be improved by the binder.

[0156] The above binder may be a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, poly(acrylic acid-co-acrylamide) (PAA-PAM), polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and various types of binder polymers such as polymers in which hydrogens of these are substituted with Li, Na, Ca, etc., or various copolymers.

[0157] The content of the binder may be 300 parts by weight, 50 parts by weight to 250 parts by weight, 50 parts by weight to 200 parts by weight, or 80 parts by weight to 200 parts by weight, based on 100 parts by weight of the total of the first conductive material and the second conductive material.

[0158] When the above range is satisfied, the decrease in electrical conductivity is minimized, and the adhesion between the current collector and the active material layer can be improved.

[0159] The above primer composition may include a thickener.

[0160] The cohesive force between the binders can be strengthened by the thickener, so that the problem of cracks or pinholes occurring on the electrode surface can be suppressed.

[0161] The thickener may be at least one selected from the group consisting of carboxymethyl cellulose (CMC), methyl cellulose (MC), hydroxypropyl cellulose (HPC), methyl hydroxypropyl cellulose (MHPC), ethyl hydroxyethyl cellulose (EHEC), methyl ethyl hydroxyethyl cellulose (MEHEC), and cellulose gum.

[0162] The degree of substitution of the thickener may be 0.5 or more, 0.55 or more, 0.6 or more, 0.65 or more, 0.7 or more, 1.0 or less, 0.95 or less, 0.9 or less, 0.85 or less, 0.8 or less, 0.5 to 1.0, 0.6 to 0.9, or 0.7 to 0.8. When the above range is satisfied, the residue content of the thickener can be minimized.

[0163] The content of the thickener may be 0.1 wt% to 2 wt%, 0.1 wt% to 1.5 wt%, 0.1 wt% to 1.2 wt%, or 0.1 wt% to 1 wt% relative to the total weight of the primer composition. The content of the thickener may be 1 wt% to 100 wt%, 1 wt% to 80 wt%, 1 wt% to 70 wt%, or 1 wt% to 50 wt% relative to 100 wt% of the total conductive material included in the primer composition. When the above range is satisfied, an increase in resistance within the electrode can be minimized.

[0164] The above primer composition includes a dispersant, and the dispersant may include a polyvinyl compound.

[0165] The above primer composition may further include a third conductive agent having an average particle diameter of 0.1 ㎛ or more and 0.3 ㎛ or less or a fourth conductive agent having an average particle diameter of 8 ㎛ or more and 35 ㎛ or less.

[0166] The sum of the solid weights of the first and third conductive agents may be 3 wt% to 10 wt%, 3 wt% to 9 wt%, 3 wt% to 8 wt%, or 3 wt% to 7 wt% relative to the total weight of the primer composition.

[0167] The sum of the solid weights of the first and fourth conductive agents may be 5 wt% to 20 wt%, 10 wt% to 20 wt%, 12 wt% to 20 wt%, or 12 wt% to 18 wt% relative to the total weight of the primer composition.

[0168] An electrode according to the present invention includes a current collector, a primer layer formed on at least one surface of the current collector, and an active material layer formed on the primer layer, wherein the primer layer includes a primer composition, and the primer composition includes a first conductive material and a second conductive material, wherein the first conductive material includes a first carbon-based material having an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, and the second conductive material includes a second carbon-based material having an average particle diameter of more than 0.2 ㎛ and less than 20 ㎛, and a solid weight ratio of the first conductive material: the solid weight ratio of the second conductive material is 1:1 to 1:3.

[0169] A positive electrode according to the present invention includes a current collector, a primer layer formed on at least one surface of the current collector, and a positive electrode active material layer formed on the primer layer, wherein the primer layer includes the primer composition described above, the primer layer includes a fifth conductive material having an average particle diameter of less than 5 μm, and the positive electrode active material layer includes a first positive electrode active material having an average particle diameter of less than 5 μm, and can satisfy the following equation 1.

[0170] [Formula 1]

[0171] 5% < (X1 / A1) × 100 < 35%

[0172] The above A1 is the average particle diameter (㎛) of the first positive electrode active material, and the above X1 is the average particle diameter (㎛) of the fifth conductive material.

[0173] The fifth challenge material may include carbon black.

[0174] The solid content weight of the fifth conductive agent may be 3 wt% to 15 wt%, 3 wt% to 12 wt%, 3 wt% to 10 wt%, or 3 wt% to 10 wt% relative to the total weight of the primer layer.

[0175] The above electrode may be a cathode. The cathode may be manufactured by forming a primer layer by applying the primer composition onto a cathode current collector, and then forming a cathode active material layer by applying a cathode active material onto the primer layer. In addition, the cathode may be manufactured by forming a cathode active material layer by applying the primer composition onto a cathode current collector, and then applying a cathode active material onto the primer composition by a wet-on-wet method.

[0176] The above primer composition may be the same as the primer composition described above.

[0177] After the formation of the above-described positive electrode active material layer, a rolling process may be performed. The drying and rolling may be performed under appropriate conditions, taking into account the properties of the electrode to be ultimately manufactured.

[0178] The positive electrode current collector is made of a highly conductive metal to which the primer composition can be easily adhered, and is not particularly limited as long as it has high conductivity without causing chemical changes in the secondary battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength of the primer composition. The positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric, and may have a thickness of 3 ㎛ to 500 ㎛.

[0179] The positive electrode active material may include a binder and a conductive agent. In addition, the positive electrode active material may include a solvent.

[0180] The above positive electrode active material may include a lithium iron phosphate-based active material. The lithium iron phosphate-based active material may be a compound represented by the following chemical formula 1.

[0181] [Chemical Formula 1]

[0182] Li 1+a Fe 1-x M x (PO 4-b )Y b

[0183] In the above chemical formula 1, M is at least one element selected from the group consisting of Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, and Cu, Y is at least one element selected from the group consisting of F, S, and N, and a, b, and x are -0.5≤a≤0.5, 0≤b≤0.1, and 0≤x≤0.5.

[0184] The above positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically may include a lithium composite metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum.

[0185] The above lithium composite metal oxides include lithium-manganese oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt oxides (e.g., LiCoO2, etc.), lithium-nickel oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese oxides (e.g., LiNi 1-Y Mn Y O2 (here, 0 <Y<1), LiMn 2-z Ni z O4 (where 0<Z<2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2 (here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2 (here, 0 <Y2<1), LiMn 2-z1 Co z1 O4 (wherein, 0<Z1<2) etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r1 )O2(wherein, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni p1 Co q1 Mn r2 )O4 (wherein, 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2) etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2)O2 (wherein, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r3 and s2 are atomic fractions of independent elements, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1), etc.), and any one or two or more compounds thereof may be included. Among these, the lithium composite metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (for example, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), and considering the remarkable improvement effect according to the control of the type and content ratio of the constituent elements forming the lithium composite metal oxide, the lithium composite metal oxide may be Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc., and any one of these or a mixture of two or more of them may be used.

[0186] The above binder can improve the adhesion between the positive electrode active materials or between the positive electrode active material and the positive electrode current collector. The above binder may be a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and various types of binder polymers such as polymers in which hydrogens of these are substituted with Li, Na, Ca, etc., or various copolymers.

[0187] The conductive material can improve electrical conductivity. The conductive material can include a conductive material such as graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black; metal powder such as fluorocarbon, aluminum, nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; and a polyphenylene derivative.

[0188] The above-described conductive material may include carbon nanotubes. The carbon nanotubes may include multi-walled carbon nanotubes and / or single-walled carbon nanotubes. Preferably, the carbon nanotubes may include single-walled carbon nanotubes having an average diameter of 0.5 nm to 25 nm, 0.5 nm to 20 nm, 0.5 nm to 15 nm, 0.5 nm to 10 nm, 0.8 nm to 10 nm, 1 nm to 10 nm, 1 nm to 5 nm, or more than 1 nm to less than or equal to 5 nm.

[0189] The solvent can mix each component in the positive electrode active material and control the viscosity. The solvent may be an organic solvent such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide, or water, and these solvents may be used alone or in combination of two or more. The amount of the solvent used may be used to an extent that can dissolve and disperse the positive electrode active material, the binder, and the conductive agent, taking into account the coating thickness and manufacturing yield of the positive electrode slurry composition.

[0190] The above electrode may be a negative electrode. The negative electrode may be manufactured by forming a primer layer by applying the primer composition onto a negative electrode current collector, and then applying a negative electrode active material onto the primer layer to form a negative electrode active material layer. In addition, the negative electrode may be manufactured by forming a negative electrode active material layer by applying the primer composition onto a negative electrode current collector, and then applying a negative electrode active material onto the primer composition using a wet-on-wet method.

[0191] After the formation of the above-described negative active material layer, a rolling process may be performed. The drying and rolling may be performed under appropriate conditions, taking into account the properties of the electrode to be ultimately manufactured.

[0192] The above negative electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the secondary battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the bonding strength of the negative electrode active material can be strengthened by forming fine unevenness on the surface, and can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc.

[0193] The positive electrode active material may include a binder and a conductive agent. In addition, the positive electrode active material may include a solvent.

[0194] The negative electrode active material may include a carbon-based material. The carbon-based material may include natural graphite particles or artificial graphite particles. The negative electrode active material may include a silicon-based material. The silicon-based material may include metallic silicon (Si), silicon oxide (SiOx, 0 <x<2), 실리콘카바이드(SiC) 및 Si-Y 합금(상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Si은 아님)으로 이루어진 군으로부터 선택된 1종 이상을 포함할 수 있다. 상기 원소 Y로는 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, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, 및 이들의 조합으로 이루어진 군에서 선택될 수 있다.

[0195] The silicon-based material can exhibit higher capacity characteristics than the carbon-based material. When the silicon-based material is included in the negative electrode active material, the capacity characteristics can be improved. However, the silicon-based material has a problem in that the volume change during charge and discharge is large compared to the carbon-based material, resulting in lower cycle characteristics. Therefore, when the single-walled carbon nanotube according to the present invention is used as a conductive material, the high electron movement path can be improved compared to the conventional conductive material, thereby improving the electrical conductivity, and the dispersibility is improved, thereby increasing the structural stability. Therefore, when the negative electrode active material includes the silicon-based material, not only the capacity characteristics can be improved, but also the cycle characteristics can be improved.

[0196] The above binder may be used to bind particles included in the negative active material to maintain the molded body. The binder may be a non-aqueous binder or an aqueous binder. For example, the non-aqueous binder may be polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinyl pyrrolidone, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyethylene, or polypropylene, and further, the aqueous binder may be any one selected from the group consisting of acrylonitrile-butadiene rubber, styrene-butadiene rubber, and acrylic rubber, or a mixture of two or more thereof. The above aqueous binder is more economical and environmentally friendly than a non-aqueous binder, is harmless to the health of workers, and has a superior binding effect compared to a non-aqueous binder, so that the ratio of active material per volume can be increased, enabling high capacity. Specifically, styrene-butadiene rubber can be used as the aqueous binder.

[0197] The above conductive material may be a point-shaped conductive material such as carbon black, acetylene black, or graphite, and / or a linear conductive material such as a single-walled carbon nanotube or a multi-walled carbon nanotube.

[0198] The above solvent can mix each component in the positive electrode active material and control the viscosity. The same solvent as the above-described solvent can be used.

[0199] The primer layer formed on the positive and / or negative electrode may have a thickness of 0.3 µm to 3 µm, 0.5 µm to 3 µm, 0.5 µm to 2.5 µm, 0.5 µm to 2 µm, or 0.5 µm to 1.5 µm.

[0200] When the above range is satisfied, electrical conductivity can be improved without reducing adhesive strength.

[0201] The above electrode may have an adhesive strength of 25 gf / 20mm to 35 gf / 20mm, 25 gf / 20mm to 33 gf / 20mm, 25 gf / 20mm to 32 gf / 20mm, or 26 gf / 20mm to 31 gf / 20mm according to the following measurement method.

[0202] [measurement method]

[0203] 1) The above electrode is punched to 20 mm × 120 mm to manufacture a specimen.

[0204] 2) After attaching double-sided tape to the slide glass, attach the above specimen and press it after rolling it back and forth 10 times using a 2 kg roller.

[0205] 3) Using a universal testing machine, the adhesive strength at which the specimen is peeled off from the slide glass is measured after pulling at a speed of 300 mm / min. At this time, the measurement section is 50 mm, and the measurement angle between the slide glass and the specimen is 90°.

[0206] When the above range is satisfied, the adhesion between the current collector and the active material layer can be maintained for a long period of time without a decrease in electrical conductivity, so that the performance of the secondary battery can be improved.

[0207] A secondary battery according to the present invention comprises a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode comprises a primer layer, wherein the primer layer comprises a primer composition, wherein the primer composition comprises a first conductive material and a second conductive material, wherein the first conductive material comprises a first carbon-based material having an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, and wherein the second conductive material comprises a second carbon-based material having an average particle diameter of more than 0.2 ㎛ and less than 20 ㎛, and wherein a solid weight ratio of the first conductive material to the solid weight ratio of the second conductive material is 1:1 to 1:3.

[0208] The above electrode may refer to a cathode and an anode. The anode and cathode may be the same as the anode and cathode described above. The primer composition, the first conductive material, the second conductive material, the first carbon-based material, and the second carbon-based material may be the same as the primer composition, the first conductive material, the second conductive material, the first carbon-based material, and the second carbon-based material described above.

[0209] The secondary battery includes a conductive material having the characteristics described above, thereby improving the interfacial adhesive strength between the current collector and the active material layer, and improving the electrical conductivity, thereby improving the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery.

[0210] The separator may be interposed between the cathode and the anode. The separator may be configured to prevent electrical short-circuiting between the cathode and the anode and to allow ion flow. The separator may include a porous polymer film or a porous non-woven fabric. The porous polymer film may be composed of a single layer or multiple layers including a polyolefin polymer such as an ethylene polymer, a propylene polymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer. The porous non-woven fabric may include high-melting-point glass fibers or polyethylene terephthalate fibers. However, the present invention is not limited thereto, and according to an embodiment, the separator may be a high-heat-resistant separator (CCS; Ceramic Coated Separator) including ceramic.

[0211] The electrolyte may be a non-aqueous electrolyte. The electrolyte may include a lithium salt and an organic solvent. The organic solvent may include at least one of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), dipropyl carbonate (DPC), vinylene carbonate (VC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, gamma-butyrolactone, propylene sulfide, and tetrahydrofuran.

[0212] The positive electrode, negative electrode, and separator may be manufactured into an electrode assembly by a winding, lamination, folding, or zigzag stacking process. The electrode assembly may be provided together with the electrolyte to be manufactured into a secondary battery. The secondary battery may be any one of a cylindrical shape using a can, a square shape, a pouch shape, and a coin shape, but is not limited thereto.

[0213] The above secondary battery can be used in a high-output and large-capacity secondary battery that requires a long lifespan and excellent durability, or in a module or pack that includes multiple of the above secondary batteries as unit batteries.

[0214] The above plurality of secondary batteries can be manufactured into a module. The above plurality of modules can be manufactured into a pack.

[0215] The above pack can be used as a power source for medium- to large-sized devices that require high-temperature stability, long-cycle characteristics, and high-rate characteristics. Examples of the medium- to large-sized devices include power tools that are powered by an electric motor; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; electric trucks; electric commercial vehicles, or power storage systems.

[0216]

[0217] <Second embodiment - primer composition, electrode containing the same, and secondary battery>

[0218] In general, the problem of electrode detachment occurs due to insufficient interfacial adhesion between the current collector and the electrode active material layer. To improve this problem, a primer layer is formed between the current collector and the electrode active material layer to improve the interfacial adhesion between the current collector and the electrode active material layer.

[0219] When the above primer layer is formed, the interfacial adhesive strength can be improved, but a problem of reduced electrical conductivity occurs due to an increase in the physical distance between the current collector and the electrode active material layer.

[0220] The above primer layer can have the interface adhesion improved by a binder, the electrical conductivity improved by a conductive material, and the dispersibility of the binder and conductive material improved by a dispersant.

[0221] That is, the primer layer may have properties related to the interface adhesion between the current collector and the electrode active material layer and the electrical conductivity depending on the type and content of the binder, conductive agent, and dispersant.

[0222] Accordingly, the inventors of the present invention have designed a secondary battery in which the dispersibility and compatibility of each component of the primer composition are excellent, and the interfacial adhesiveness and electrical conductivity are improved, thereby improving the properties related to the interfacial adhesiveness and the electrical conductivity between the current collector and the electrode active material layer, and the electrical conductivity, by combining a conductive material having an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛ and a dispersant including a polyvinyl-based compound.

[0223] The primer composition according to the present invention includes a first conductive material. The first conductive material can improve electrical conductivity between the current collector and the active material layer.

[0224] The above first conductive agent may have an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, 0.01 ㎛ or more and 0.09 ㎛ or less, 0.02 ㎛ or more and 0.09 ㎛ or less, 0.02 ㎛ or more and 0.08 ㎛ or less, or 0.03 ㎛ or more and 0.07 ㎛ or less. When the above range is satisfied, the empty space between the conductive agents can be minimized, the ratio of the binder can be reduced, so that the electrical conductivity can be improved, and the compatibility with the polyvinyl-based dispersant is excellent, so that the dispersibility is improved, so that the efficiency in the manufacturing process can be increased.

[0225] The above average particle diameter refers to the particle diameter at the n% point of the cumulative particle number distribution, and refers to the particle diameter at the 50% point of the cumulative particle number distribution. The above average particle diameter can be measured using a laser diffraction method. Specifically, the particle size distribution can be calculated by dispersing the measurement target material in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device, and then measuring the difference in diffraction pattern according to particle size when the particles pass through a laser beam.

[0226] The above primer composition may further include a second conductive agent and / or a third conductive agent having a different average particle diameter from the first conductive agent to further improve electrical conductivity.

[0227] The second conductive material may be the same as the third conductive material of the first embodiment described above, and the third conductive material may be the same as the fourth conductive material of the first embodiment described above.

[0228] The above second conductive material may have an average particle diameter of 0.1 µm or more and 0.3 µm or less, 0.12 µm or more and 0.3 µm or less, 0.15 µm or more and 0.3 µm or less, 0.15 µm or more and 0.28 µm or less, or 0.15 µm or more and 0.25 µm or less.

[0229] The third conductive material may have an average particle size of 8 µm or more and 35 µm or less, 10 µm or more and 35 µm or less, 12 µm or more and 35 µm or less, 15 µm or more and 35 µm or less, or 18 µm or more and 30 µm or less.

[0230] By including the second conductive agent and / or the third conductive agent in the above range, the first conductive agent can fill the empty space between the second conductive agent and / or the third conductive agent, so that the ratio of the binder can be reduced, and the thickness of the primer layer can be reduced, so that the electrical conductivity can be further improved without reducing the adhesive strength.

[0231] The solid content weight of the first conductive agent may be 1 wt% to 10 wt%, 1 wt% to 8 wt%, 2 wt% to 8 wt%, or 3 wt% to 7 wt% relative to the total weight of the primer composition.

[0232] The sum of the solid weights of the first and second conductive agents may be 3 wt% to 10 wt%, 3 wt% to 9 wt%, 3 wt% to 8 wt%, or 3 wt% to 7 wt% relative to the total weight of the primer composition.

[0233] The sum of the solid weights of the first and third conductive agents may be 5 wt% to 20 wt%, 10 wt% to 20 wt%, 12 wt% to 20 wt%, or 12 wt% to 18 wt% relative to the total weight of the primer composition.

[0234] When the above range is satisfied, the interfacial adhesion between the current collector and the active material layer is not reduced, and electrical conductivity can be improved.

[0235] The first, second, and third conductive materials may be spherical carbon-based materials. The primer composition uses spherical carbon-based materials instead of needle-based carbon-based materials as the conductive material, thereby improving dispersibility, increasing efficiency in the manufacturing process, and enhancing compatibility with other materials. Furthermore, impurities such as iron elements may be reduced, thereby improving electron transport pathways and enhancing electrical conductivity, thereby improving the performance of secondary batteries.

[0236] The first conductive agent may have an oil absorption number of 100 ml / 100g to 200 ml / 100g, 100 ml / 100g to 180 ml / 100g, 100 ml / 100g to 150 ml / 100g, or 110 ml / 100g to 150 ml / 100g.

[0237] When the above range is satisfied, compatibility with other materials is improved, and the primer composition can exhibit an appropriate viscosity, thereby improving dispersibility.

[0238] The first conductive material may include acetylene black. The first conductive material may have a BET specific surface area of ​​1 m 2 / g to 200 m 2 / g, 1 m 2 / g to 150 m 2 / g, 1 m 2 / g to 100 m 2 / g, 10 m 2 / g to 100 m 2 / g, or 20 m 2 / g to 100 m 2 / g of acetylene black. The BET specific surface area can be measured from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mini II of BEL Japan.

[0239] The second challenge agent may include carbon black.

[0240] The above second challenge material has a BET surface area of ​​1 m 2 / g to 100 m 2 / g, 1 m 2 / g to 90 m 2 / g, 1 m 2 / g to 70 m 2 / g, 1 m 2 / g to 60 m 2 / g, or 1 m 2 / g to 50 m 2 / g may contain carbon black.

[0241] The third challenge material may include graphite.

[0242] The third challenge material above has a BET surface area of ​​1 m 2 / g to 50 m 2 / g, 1 m 2 / g to 40 m 2 / g, 1 m 2 / g to 30 m 2 / g, 1 m 2 / g to 20 m 2 / g, or 1 m 2 / g to 10 m 2 / g may contain graphite.

[0243] The primer composition includes a dispersant, and the dispersant includes a polyvinyl compound. The polyvinyl compound is suitable for surrounding a conductive material having an average particle size of 0.01 ㎛ or more and less than 0.1 ㎛ compared to a polyacrylic compound and a cellulose compound, so that the conductive material can be dispersed more uniformly, and has excellent weather resistance, durability, and thermal characteristics, so that an increase in viscosity due to changes over time can be minimized.

[0244] The solid content weight of the dispersant may be 1 wt% to 5 wt%, 1 wt% to 4 wt%, 1 wt% to 3 wt%, or 1 wt% to 2 wt% relative to the total weight of the primer composition.

[0245] When the above range is satisfied, the dispersibility of the conductive material included in the primer composition can be further improved.

[0246] The above polyvinyl compound may include at least one selected from the group consisting of polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl chloride, polyvinyl fluoride, and polyvinyl acetate.

[0247] Preferably, the polyvinyl compound may include polyvinylpyrrolidone having a weight average molecular weight of 37,000 g / mol to 50,000 g / mol. The weight average molecular weight of the polyvinylpyrrolidone may be 37,000 g / mol to 50,000 g / mol, 37,000 g / mol to 43,000 g / mol, 37,000 g / mol to 42,000 g / mol, 39,000 g / mol to 42,000 g / mol, or 29,000 g / mol to 41,000 g / mol.

[0248] When the above range is satisfied, it is more suitable for surrounding a conductive material having an average particle size of 0.01 ㎛ or more and less than 0.1 ㎛, so that the conductive material can be more efficiently dispersed.

[0249] The primer composition may further include a binder, and the solid content weight of the binder may be 1 wt% to 10 wt%, 2 wt% to 10 wt%, 3 wt% to 10 wt%, or 4 wt% to 10 wt% relative to the total weight of the primer composition.

[0250] The adhesive strength between the first conductive material, or between the first conductive material and the second conductive material and / or the third conductive material, may be improved by the binder. In addition, the adhesive strength between the current collector and the active material layer may be improved by the binder.

[0251] The binder may include a first water-soluble binder containing an amide group and a carboxyl group. The first water-soluble binder may include poly(acrylic acid-co-acrylamide) (PAA-PAM). When the primer composition includes poly(acrylic acid-co-acrylamide) as a binder, it is easy to bind conductive materials having an average particle size of 0.01 ㎛ or more and less than 0.1 ㎛, and has excellent compatibility with a polyvinyl-based compound, so that efficiency in the manufacturing process is increased, and the ratio of the binder can be reduced, so that the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery can be improved.

[0252] The solid content weight of the first water-soluble binder may be 3 wt% to 10 wt%, 4 wt% to 10 wt%, 4 wt% to 9.5 wt%, or 4 wt% to 9 wt% relative to the total weight of the primer composition.

[0253] When the above range is satisfied, the decrease in electrical conductivity is minimized, and the adhesion between the current collector and the active material layer can be improved.

[0254] The binder may include a second water-dispersible binder including an ester group. The second water-dispersible binder may include a polyester compound. The second water-dispersible binder may have a structure in which at least one compound selected from polyhydric carboxylic acids and derivatives thereof having two or more carboxyl groups per molecule and at least one compound selected from polyhydric alcohols having two or more hydroxyl groups per molecule are condensed. When the primer composition includes a polyester compound as a binder, the primer composition is easy to bind between conductive materials having an average particle size of 0.01 ㎛ or more and less than 0.1 ㎛, has excellent compatibility with a dispersant and an aqueous solvent, and has excellent solvent resistance, and can improve the initial efficiency, life characteristics, and high-rate discharge characteristics of a secondary battery.

[0255] The above polyester compound is at room temperature and a shear rate of 10 s -1 The viscosity may be from 30 cPs to 100 cPs, from 40 cPs to 100 cPs, from 40 cPs to 90 cPs, or from 50 cPs to 90 cPs.

[0256] The polyester compound may have a pH of 4.5 to 8, 5 to 8, 5 to 7.5, or 5 to 7.

[0257] The polyester compound may have a weight average molecular weight of 13,000 g / mol to 20,000 g / mol, 14,000 g / mol to 20,000 g / mol, 14,000 g / mol to 18,000 g / mol, or 15,000 g / mol to 17,000 g / mol.

[0258] The above polyester compound may have an acid value of less than 7.5 mgKOH / g, less than 7 mgKOH / g, less than 6.5 mgKOH / g, or less than 5 mgKOH / g.

[0259] When the polyester compound satisfies the above properties, compatibility with the dispersant and the aqueous solvent is further improved, and the adhesive strength between the current collector and the active material layer can be improved.

[0260] The solid content weight of the second water-dispersible binder may be 5 wt% to 10 wt%, 6 wt% to 10 wt%, 7 wt% to 10 wt%, or 8 wt% to 10 wt% relative to the total weight of the primer composition.

[0261] When the above range is satisfied, the decrease in electrical conductivity is minimized, and the adhesion between the current collector and the active material layer can be improved.

[0262] The above binder may include a third water-soluble binder comprising a polyvinyl-based compound having a weight average molecular weight of 2,000,000 g / mol to 3,000,000 g / mol, 2,100,000 g / mol to 3,000,000 g / mol, 2,200,000 g / mol to 3,000,000 g / mol, or 2,300,000 g / mol to 3,000,000 g / mol.

[0263] The above polyvinyl compound may include at least one selected from the group consisting of polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl chloride, polyvinyl fluoride, and polyvinyl acetate.

[0264] Preferably, the polyvinyl compound may be of the same type as the polyvinyl compound included in the dispersant and may have a relatively large weight average molecular weight.

[0265] When the primer composition includes the polyvinyl compound as a binder, it has excellent compatibility with a dispersant including the polyvinyl compound, and the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery can be improved.

[0266] The solid content weight of the third water-soluble binder may be 5 wt% to 10 wt%, 6 wt% to 10 wt%, 7 wt% to 10 wt%, or 8 wt% to 10 wt% relative to the total weight of the primer composition.

[0267] When the above range is satisfied, the decrease in electrical conductivity is minimized, and the adhesion between the current collector and the active material layer can be improved.

[0268] The above primer composition may further include a thickener.

[0269] The cohesive force between the binders can be strengthened by the thickener, so that the problem of cracks or pinholes occurring on the electrode surface can be suppressed.

[0270] The thickener may be at least one selected from the group consisting of carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (Na-CMC), methyl cellulose (MC), hydroxypropyl cellulose (HPC), methyl hydroxypropyl cellulose (MHPC), ethyl hydroxyethyl cellulose (EHEC), methyl ethyl hydroxyethyl cellulose (MEHEC), and cellulose gum.

[0271] The degree of substitution of the thickener may be 0.5 or more, 0.55 or more, 0.6 or more, 0.65 or more, 0.7 or more, 1.0 or less, 0.95 or less, 0.9 or less, 0.85 or less, 0.8 or less, 0.5 to 1.0, 0.6 to 0.9, or 0.7 to 0.8. When the above range is satisfied, the residue content of the thickener can be minimized.

[0272] The content of the thickener may be 0.1 wt% to 2 wt%, 0.1 wt% to 1.5 wt%, 0.1 wt% to 1.2 wt%, or 0.1 wt% to 1 wt% relative to the total weight of the primer composition. The content of the thickener may be 1 wt% to 100 wt%, 1 wt% to 80 wt%, 1 wt% to 70 wt%, or 1 wt% to 50 wt% relative to 100 wt% of the total conductive material included in the primer composition. When the above range is satisfied, an increase in resistance within the electrode can be minimized.

[0273] The above primer composition may further include a solvent. The solvent may be the same as the solvent of the first embodiment described above.

[0274] The above primer composition is prepared at room temperature and a shear rate of 10 s -1 The viscosity may be 100 cPs to 1,000 cPs, 150 cPs to 1,000 cPs, 150 cPs to 900 cPs, or 150 cPs to 850 cPs. When the above viscosity range is satisfied, the phenomenon of cracks or pinholes occurring on the electrode surface can be minimized, and the side ring phenomenon in which the active material layer is applied with a high thickness at the end can be suppressed.

[0275] The above primer composition may have a content of transition metal impurities according to the first embodiment and the analysis method described above.

[0276] An electrode according to the present invention comprises a current collector, a primer layer formed on at least one surface of the current collector, and an active material layer formed on the primer layer, wherein the primer layer comprises a primer composition, the primer composition comprises a first conductive material, and a dispersant, wherein the first conductive material has an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, and the dispersant comprises a polyvinyl-based compound.

[0277] The above electrode may be a cathode. The cathode may be manufactured by forming a primer layer by applying the primer composition onto a cathode current collector, and then forming a cathode active material layer by applying a cathode active material onto the primer layer. In addition, the cathode may be manufactured by forming a cathode active material layer by applying the primer composition onto a cathode current collector, and then applying a cathode active material onto the primer composition by a wet-on-wet method.

[0278] The above primer composition may be the same as the primer composition described above.

[0279] After the formation of the above-described positive electrode active material layer, a rolling process may be performed. The drying and rolling may be performed under appropriate conditions, taking into account the properties of the electrode to be ultimately manufactured.

[0280] The above positive electrode collector may be the same as the positive electrode collector of the first embodiment described above.

[0281] The above positive electrode active material may be the same as the positive electrode active material of the first embodiment described above.

[0282] The binder can improve the adhesion between the positive electrode active materials or between the positive electrode active material and the positive electrode current collector. The binder may be the same as the binder of the first embodiment. The conductive agent can improve electrical conductivity. The conductive agent may be the same as the conductive agent of the first embodiment. The solvent can mix each component in the positive electrode active material and control the viscosity. The solvent may be the same as the solvent of the first embodiment described above.

[0283] The above electrode may be an anode. The above anode may be the same as the anode of the first embodiment described above.

[0284] The primer layer formed on the positive and / or negative electrode may be the same as the primer layer of the first embodiment described above.

[0285] The above electrode may have an adhesive strength of 10 gf / 20mm to 25 gf / 20mm, 10.5 gf / 20mm to 25 gf / 20mm, 11 gf / 20mm to 25 gf / 20mm, or 12.22 gf / 20mm to 21.26 gf / 20mm according to the following measurement method.

[0286] [measurement method]

[0287] 1) The above electrode is punched to 20 mm × 120 mm to manufacture a specimen.

[0288] 2) After attaching double-sided tape to the slide glass, attach the above specimen and press it after rolling it back and forth 10 times using a 2 kg roller.

[0289] 3) Using a universal testing machine, the adhesive strength at which the specimen is peeled off from the slide glass is measured after pulling at a speed of 300 mm / min. At this time, the measurement section is 50 mm, and the measurement angle between the slide glass and the specimen is 90°.

[0290] When the above range is satisfied, the adhesion between the current collector and the active material layer can be maintained for a long period of time without a decrease in electrical conductivity, so that the performance of the secondary battery can be improved.

[0291] A secondary battery according to the present invention comprises a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode comprises a primer layer, the primer layer comprises a primer composition, the primer composition comprises a first conductive material, and a dispersant, the first conductive material having an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, and the dispersant comprises a polyvinyl-based compound.

[0292] The above electrode may refer to an anode and a cathode. The anode and cathode may be the same as the anode and cathode described above. The primer composition may be the same as the primer composition described above.

[0293] The secondary battery includes a first conductive material and a dispersant having the characteristics described above, thereby improving the interfacial adhesive strength between the current collector and the active material layer, and improving the electrical conductivity, thereby improving the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery.

[0294] The secondary battery may have a voltage range of 0 V to 5.5 V, 3 V to 5.5 V, 4 V to 5.5 V, or 4.5 V to 5.5 V at 0.05 mA when measured by linear sweep voltammetry. When the above range is satisfied, the composition included in the primer layer and the electrolyte are electrochemically stable at low and high voltages, so that side reactions due to reduction and / or oxidation of the electrolyte can be suppressed when applied to a secondary battery.

[0295] The separator may be interposed between the cathode and the anode. The separator may be the same as the separator of the first embodiment described above.

[0296] The above electrolyte may be a non-aqueous electrolyte. The above electrolyte may be the same as the electrolyte of the first embodiment described above.

[0297] The above positive electrode, negative electrode, and separator can be manufactured into an electrode assembly by a winding, lamination, folding, or zigzag stacking process. The electrode assembly can be the same as the electrode assembly of the first embodiment described above.

[0298] The above secondary battery can be used in a high-output and large-capacity secondary battery that requires a long lifespan and excellent durability, or in a module or pack that includes multiple of the above secondary batteries as unit batteries.

[0299] The above-described plurality of secondary batteries may be manufactured as modules. The above-described plurality of modules may be manufactured as a pack. The above-described plurality of modules and pack may be identical to the modules and pack of the first embodiment described above.

[0300]

[0301] <Third embodiment - positive electrode and secondary battery including the same>

[0302] Typically, a positive electrode active material layer is formed on a current collector during the manufacture of a positive electrode. However, due to insufficient interfacial adhesion between the current collector and the positive electrode active material layer, a problem has arisen in which the positive electrode active material layer detaches from the current collector. Accordingly, a method has been considered to enhance the interfacial adhesion between the current collector and the positive electrode active material layer by increasing the binder content in the positive electrode active material layer or by forming a primer layer between the current collector and the positive electrode active material layer.

[0303] However, when the binder content in the positive electrode active material layer increases, the content of the positive electrode active material relatively decreases, resulting in a problem of reduced capacity of the secondary battery.

[0304] In addition, when the primer layer is formed, the interfacial adhesive strength between the current collector and the positive electrode active material layer can be improved, but a problem of reduced electrical conductivity occurs due to an increase in the physical distance between the current collector and the electrode active material layer.

[0305] Accordingly, a conductive material was mixed into the primer layer as a method for improving electrical conductivity, but the adhesive strength was reduced by the conductive material, so the ratio of the binder had to be increased, which caused a problem in that the thickness of the primer layer increased, the resistance increased, and the performance of the secondary battery deteriorated.

[0306] The present inventors have noted that the surface roughness of the primer layer can be varied depending on the average particle diameter of the conductive material and / or a combination of conductive materials having different average particle diameters, in order to improve the interfacial adhesiveness between the current collector and the positive electrode active material layer and the performance of the secondary battery. In addition, the inventors have conceived that the interfacial adhesiveness between the current collector and the positive electrode active material layer can be varied depending on the relationship between the surface roughness of the primer layer and the average particle diameter of the positive electrode active material formed on the primer layer.

[0307] That is, the inventors of the present invention have devised a secondary battery in which the interface adhesiveness between a current collector and the positive electrode active material layer is improved compared to the prior art, and the phenomenon of the positive electrode active material layer being detached from the current collector is suppressed, thereby improving the initial efficiency, life characteristics, and high-rate discharge characteristics by deriving an optimal average particle diameter of the conductive material according to the average particle diameter of the positive electrode active material and / or a combination of conductive materials having different average particle diameters.

[0308] A cathode according to the present invention includes a current collector, a primer layer formed on at least one surface of the current collector, and a cathode active material layer formed on the primer layer.

[0309] The current collector is not particularly limited as long as it is a highly conductive metal to which the primer composition can easily adhere, and has high conductivity without causing chemical changes in the secondary battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, fine unevenness may be formed on the surface of the current collector to increase the adhesive strength of the primer composition. The current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric, and may have a thickness of 3 ㎛ to 500 ㎛.

[0310] The primer layer includes a first conductive material having an average particle diameter of less than 5 μm, and the positive electrode active material layer includes a first positive electrode active material having an average particle diameter of less than 5 μm. The first conductive material may be the same as the fifth conductive material of the first embodiment.

[0311] The above average particle diameter refers to the particle diameter at the n% point of the cumulative particle number distribution, and refers to the particle diameter at the 50% point of the cumulative particle number distribution. The above average particle diameter can be measured using a laser diffraction method. Specifically, the particle size distribution can be calculated by dispersing the measurement target material in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device, and then measuring the difference in diffraction pattern according to particle size when the particles pass through a laser beam.

[0312] The anode according to the present invention satisfies the following equation 1.

[0313] [Formula 1]

[0314] 5% < (X1 / A1) × 100 < 35%

[0315] The above A1 is the average particle diameter (㎛) of the first positive electrode active material, and the above X1 is the average particle diameter (㎛) of the first conductive material.

[0316] In the above formula 1, the (X1 / A1) × 100 may be 5.5% or more and less than 35%, 5.5% or more and less than 34%, 5.5% or more and less than 30%, 8% or more and less than 30%, or 8% or more and less than 25%.

[0317] The above A1 may be less than 5 ㎛, less than 4.5 ㎛, less than 3 ㎛, less than 3.5 ㎛, less than 3 ㎛, less than 2 ㎛, 0.1 ㎛ or more to less than 2 ㎛, 0.2 ㎛ or more to 2 ㎛ or less, 0.6 ㎛ or more to 2 ㎛ or less, or 0.6 ㎛ or more to 1.8 ㎛ or less.

[0318] The above formula 1 may mean the ratio of the average particle diameter of the first conductive material to the average particle diameter of the first positive electrode active material.

[0319] The above formula 1 may mean a ratio of the average particle diameter of the conductive material to the average particle diameter of the positive electrode active material, which can improve the interfacial adhesive force between the current collector and the positive electrode active material layer, when the average particle diameter of the positive electrode active material is less than 5 ㎛ among positive electrode active materials having various average particle diameters.

[0320] When the range of the above formula 1 is satisfied, the interfacial adhesive strength between the current collector and the positive electrode active material layer is improved, and the phenomenon of the positive electrode active material layer being detached from the current collector is suppressed, so that the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery can be improved.

[0321] The above first positive electrode active material may include lithium iron oxide.

[0322] The above lithium iron oxide may be a compound represented by the following chemical formula 1.

[0323] [Chemical Formula 1]

[0324] Li 1+a Fe 1-x M x (PO 4-b )Y b

[0325] In the above chemical formula 1, M is at least one element selected from the group consisting of Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, and Cu, Y is at least one element selected from the group consisting of F, S, and N, and a, b, and x are -0.5≤a≤0.5, 0≤b≤0.1, and 0≤x≤0.5.

[0326] The above lithium iron oxide may be LiFePO4.

[0327] The above lithium iron oxide has a BET surface area of ​​30 m 2 / g or less, 20 m 2 / g or less, or 8 m 2 / g to 12 m 2 / g. The above BET specific surface area can be calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mino II of BEL Japan. When the above range is satisfied, the adhesion to the primer layer may not be reduced.

[0328] The above lithium iron oxide has a tap density of 0.5 g / cm 3 Above, 0.6 g / cm 3 or more than 0.6 g / cm 3 Inland 1.5 g / cm 3It can be. The above tap density refers to the apparent density of the lithium iron oxide powder and can be measured using Seishin's KYT-5000. When the above range is satisfied, the packing density of the positive electrode is improved, the thickness of the positive electrode is improved to be thinner, and the breakage phenomenon of the positive electrode active material can be improved.

[0329] Electrical conductivity between the current collector and the positive electrode active material layer can be improved by the first conductive material.

[0330] The above first conductive material may have an average particle diameter of less than 5 ㎛, less than 4 ㎛, less than 3 ㎛, less than 2 ㎛, less than 5 ㎛, 0.1 ㎛ or more to 0.3 ㎛ or less, 0.12 ㎛ or more to 0.3 ㎛ or less, 0.12 ㎛ or more to 0.25 ㎛ or less, 0.12 ㎛ or more to 0.20 ㎛ or less, or 0.12 ㎛ or more to 0.18 ㎛ or less. When the above range is satisfied, the empty space between the first conductive materials can be minimized, the ratio of the binder can be reduced, so that the electrical conductivity can be improved, and the compatibility with the dispersant is excellent, so that the dispersibility is improved, so that the efficiency in the manufacturing process can be increased.

[0331] The above first challenge material may include carbon black.

[0332] The above first challenge material has a BET surface area of ​​1 m 2 / g to 100 m 2 / g, 1 m 2 / g to 90 m 2 / g, 1 m 2 / g to 70 m 2 / g, 1 m 2 / g to 60 m 2 / g, or 1 m 2 / g to 50 m 2 / g may contain carbon black.

[0333] The solid content weight of the first conductive material may be 3 wt% to 15 wt%, 3 wt% to 12 wt%, 3 wt% to 10 wt%, or 3 wt% to 10 wt% relative to the total weight of the primer layer. When the above range is satisfied, the interfacial adhesive strength between the current collector and the active material layer is not reduced, and electrical conductivity can be improved.

[0334] The positive electrode active material layer can be manufactured by forming the primer layer by applying the primer composition on the current collector, and then forming the positive electrode active material layer by applying the positive electrode active material on the primer layer. In addition, the positive electrode active material layer can be manufactured by forming the positive electrode active material layer by applying the primer composition on the current collector, and then forming the positive electrode active material layer on the primer composition by a wet-on-wet method.

[0335] The above anode may have an adhesive strength of 15 gf / 20mm to 30 gf / 20mm, 18 gf / 20mm to 30 gf / 20mm, 18 gf / 20mm to 28 gf / 20mm, or 22 gf / 20mm to 22.5 gf / 20mm according to the following measurement method 1.

[0336] [Measurement Method 1]

[0337] 1) The above anode is punched to 20 mm × 120 mm to manufacture a specimen.

[0338] 2) After attaching double-sided tape to the slide glass, attach the above specimen and press it after rolling it back and forth 10 times using a 2 kg roller.

[0339] 3) Using a universal testing machine, the adhesive strength at which the specimen is peeled off from the slide glass is measured after pulling at a speed of 300 mm / min. At this time, the measurement section is 50 mm, and the measurement angle between the slide glass and the specimen is 90°.

[0340] When the above range is satisfied, the adhesion between the current collector and the positive electrode active material layer can be maintained for a long period of time without a decrease in electrical conductivity, so that the performance of the secondary battery can be improved.

[0341] When the positive electrode active material layer according to the present invention includes a second positive electrode active material having an average particle diameter of 5 ㎛ or more, the primer layer includes a second conductive material having an average particle diameter of 5 ㎛ or more and a third conductive material having an average particle diameter different from that of the second conductive material, and satisfies the following equations 2 and 3.

[0342] [Formula 2]

[0343] 100 % < (X2 / A2) × 100 < 300 %

[0344] [Formula 3]

[0345] 0.05 % < (X3 / X2) × 100 < 0.7 %

[0346] The above A2 is the average particle diameter (㎛) of the second positive electrode active material, the above X2 is the average particle diameter (㎛) of the second conductive material, and the above X3 is the average particle diameter (㎛) of the third conductive material.

[0347] The present inventors have noted that when the average particle size of the positive electrode active material is 5 ㎛ or more, unlike when the average particle size of the positive electrode active material is less than 5 ㎛, the phenomenon of the positive electrode active material layer being detached from the current collector is suppressed by including two types of conductive materials having different average particle sizes and satisfying a specific average particle size ratio between the two types of conductive materials, thereby improving the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery.

[0348] In the above formula 2, the (X2 / A2) × 100 may be 105% or more to 280% or less, 110% or more to 270% or less, 120% or more to 270% or less, 133% or more to 270% or less, or 133% or more to 263% or less.

[0349] The above A2 may be 8 ㎛ or more and 12 ㎛ or less, 9 ㎛ or more and 12 ㎛ or less, 9 ㎛ or more and 11 ㎛ or less, or 9.5 ㎛ or more and 11 ㎛ or less.

[0350] The above equation 2 may mean the ratio of the average particle diameter of the second conductive material to the average particle diameter of the second positive electrode active material.

[0351] The above formula 2 may mean a ratio of the average particle diameter of the conductive material to the average particle diameter of the positive electrode active material, which can improve the interfacial adhesive force between the current collector and the positive electrode active material layer, when the average particle diameter of the positive electrode active material is 5 ㎛ or more among positive electrode active materials having various average particle diameters.

[0352] When the range of the above formula 2 is satisfied, the interfacial adhesive strength between the current collector and the positive electrode active material layer is improved, and the phenomenon of the positive electrode active material layer being detached from the current collector is suppressed, so that the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery can be improved.

[0353] In the above formula 3, the (X3 / X2) × 100 may be 0.1% or more and less than 0.7%, 0.15% or more and 0.65% or less, 0.2% or more and 0.5% or less, or 0.23% or more and 0.32% or less.

[0354] The above formula 3 may mean the ratio of the average particle diameter of the third conductive material to the average particle diameter of the second conductive material.

[0355] When the range of the above formula 3 is satisfied, the empty space between the second conductive materials having a large average particle diameter can be minimized, so that electrical conductivity can be improved, and the interfacial adhesive force between the current collector and the positive electrode active material layer can be improved, so that the phenomenon of the positive electrode active material layer being detached from the current collector can be suppressed.

[0356] The second positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and may include a lithium composite metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. The lithium composite metal oxide may be the same as the lithium composite metal oxide of the first and second embodiments described above.

[0357] Preferably, the second positive electrode active material may include lithium nickel cobalt manganese oxide, and most preferably Li(Ni 0.6 Mn 0.2 Co 0.2 ) may contain O2.

[0358] Electrical conductivity between the current collector and the positive electrode active material layer can be improved by the second and third conductive agents.

[0359] The second conductive material may have an average particle size of 8 µm or more and 35 µm or less, 10 µm or more and 35 µm or less, 12 µm or more and 35 µm or less, 15 µm or more and 25 µm or less, or 16 µm or more and 21 µm or less.

[0360] The third conductive material may have an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, 0.01 ㎛ or more and 0.09 ㎛ or less, 0.02 ㎛ or more and 0.09 ㎛ or less, 0.02 ㎛ or more and 0.08 ㎛ or less, or 0.03 ㎛ or more and 0.07 ㎛ or less.

[0361] By including the second and third conductive materials in the above range, the third conductive material can fill the empty space between the second conductive materials, so that the ratio of the binder can be reduced, and the thickness of the primer layer can be reduced, so that the electrical conductivity can be further improved without reducing the adhesive strength.

[0362] The second challenge material may include graphite.

[0363] The above second challenge material has a BET surface area of ​​1 m 2 / g to 50 m 2 / g, 1 m 2 / g to 40 m 2 / g, 1 m 2 / g to 30 m 2 / g, 1 m 2 / g to 20 m 2 / g, or 1 m 2 / g to 10 m 2 / g may contain graphite.

[0364] The third challenge agent may include acetylene black.

[0365] The third challenge material above has a BET surface area of ​​1 m 2 / g to 200 m 2 / g, 1 m 2 / g to 150 m 2 / g, 1 m 2 / g to 100 m 2 / g, 10 m 2 / g to 100 m 2 / g, or 20 m 2 / g to 100 m 2 / g may contain acetylene black.

[0366] The third challenge material may have an oil absorption number of 100 ml / 100g to 300 ml / 100g, 100 ml / 100g to 200 ml / 100g, 100 ml / 100g to 180 ml / 100g, 100 ml / 100g to 150 ml / 100g, or 110 ml / 100g to 150 ml / 100g.

[0367] When the above range is satisfied, compatibility with other materials is improved, and the primer composition can exhibit an appropriate viscosity, thereby improving dispersibility.

[0368] The sum of the solid weights of the second and third conductive agents may be 3 wt% to 15 wt%, 4 wt% to 15 wt%, 5 wt% to 15 wt%, or 8 wt% to 15 wt% relative to the total weight of the primer composition.

[0369] The solid weight ratio of the second conductive agent to the solid weight ratio of the third conductive agent may be 3:1 to 1:1, 2.8:1 to 1:1, 2.5:1 to 1:1, or 2:1 to 1:1.

[0370] When the above range is satisfied, the interfacial adhesion between the current collector and the positive electrode active material layer is not reduced, and the electrical conductivity can be improved.

[0371] The above anode may have an adhesive strength according to the following measurement method 2 of more than 30 gf / 20mm to 45 gf / 20mm, 30 gf / 20mm to 40 gf / 20mm, 30 gf / 20mm to 35 gf / 20mm, or 32.2 gf / 20mm to 34.9 gf / 20mm.

[0372] [Measurement Method 2]

[0373] 1) The above anode is punched to 20 mm × 120 mm to manufacture a specimen.

[0374] 2) After attaching double-sided tape to the slide glass, attach the above specimen and press it after rolling it back and forth 10 times using a 2 kg roller.

[0375] 3) Using a universal testing machine, the adhesive strength at which the specimen is peeled off from the slide glass is measured after pulling at a speed of 300 mm / min. At this time, the measurement section is 50 mm, and the measurement angle between the slide glass and the specimen is 90°.

[0376] When the above range is satisfied, the adhesion between the current collector and the positive electrode active material layer can be maintained for a long period of time without a decrease in electrical conductivity, so that the performance of the secondary battery can be improved.

[0377] The above measurement method 2 may be the same as the above-described measurement method 1.

[0378] The aforementioned primer layer may include a dispersant.

[0379] The above dispersant may include a polyvinyl compound. The polyvinyl compound may be the same as the polyvinyl compound of the first and second embodiments described above.

[0380] The aforementioned primer layer may include a binder. The binder may be the same as the binder of the first and second embodiments described above.

[0381] The primer composition described above may further include a thickener. The thickener may be the same as the thickener of the first and second embodiments described above.

[0382] The aforementioned primer layer refers to a cured product of a primer composition, and the primer composition may include a solvent. The components included in the primer composition may be dispersed by the solvent. The solvent may be the same as the solvent of the first and second embodiments described above.

[0383] The above primer composition may have a content of transition metal impurities according to the inductively coupled plasma mass spectrometry in the first and second embodiments described above.

[0384] The aforementioned positive electrode active material layer may include a binder and a conductive material. In addition, the positive electrode active material layer refers to a cured product of a positive electrode active material composition, and the positive electrode active material composition may include a solvent.

[0385] The above binder can improve the adhesion between the positive electrode active materials or between the positive electrode active material and the positive electrode current collector. The binder may be the same as the binder in the first and second embodiments described above.

[0386] The above conductive material can improve electrical conductivity. The above conductive material may be the same as the conductive material in the first and second embodiments described above.

[0387] The solvent can mix each component in the positive electrode active material and control the viscosity. The solvent may be the same as the solvent in the first and second embodiments described above.

[0388] A secondary battery according to the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode includes a current collector, a primer layer formed on at least one surface of the current collector, and a positive electrode active material layer formed on the primer layer, wherein the primer layer includes a first conductive material having an average particle diameter of less than 5 ㎛, and the positive electrode active material layer includes a first positive electrode active material having an average particle diameter of less than 5 ㎛, and satisfies the following equation 1.

[0389] [Formula 1]

[0390] 5% < (X1 / A1) × 100 < 35%

[0391] The above A1 is the average particle diameter (㎛) of the first positive electrode active material, and the above X1 is the average particle diameter (㎛) of the first conductive material.

[0392] In addition, a secondary battery according to the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode includes a current collector, a primer layer formed on at least one surface of the current collector, and a positive electrode active material layer formed on the primer layer, wherein the primer layer includes a second conductive material having an average particle diameter of 5 ㎛ or more and a third conductive material having an average particle diameter different from that of the second conductive material, and the positive electrode active material layer includes a second positive electrode active material having an average particle diameter of 5 ㎛ or more, and satisfies the following equations 2 and 3.

[0393] [Formula 2]

[0394] 100 % < (X2 / A2) × 100 < 300 %

[0395] [Formula 3]

[0396] 0.05 % < (X3 / X2) × 100 < 0.7 %

[0397] The above A2 is the average particle diameter (㎛) of the second positive electrode active material, the above X2 is the average particle diameter (㎛) of the second conductive material, and the above X3 is the average particle diameter (㎛) of the third conductive material.

[0398] In the secondary battery, when the average particle diameter of the positive electrode active material included in the positive electrode active material layer is less than 5 ㎛, the average particle diameter of the conductive material included in the primer layer is less than 5 ㎛, and the relationship between the average particle diameter of the positive electrode active material and the average particle diameter of the conductive material satisfies the above equation 1.

[0399] Meanwhile, the secondary battery includes a conductive material having an average particle diameter of 5 μm or more in the primer layer and a different conductive material having an average particle diameter different from that of the conductive material, when the average particle diameter of the positive electrode active material included in the positive electrode active material layer is 5 μm or more, and the relationship between the average particle diameter of the positive electrode active material and the average particle diameters of the conductive materials satisfies Equations 2 and 3.

[0400] The secondary battery has the above-described characteristics of the average particle diameter of the positive electrode active material and the average particle diameter of the conductive material, so that the interfacial adhesive force between the current collector and the positive electrode active material layer is improved, and the electrical conductivity is improved, so that the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery can be improved.

[0401] The above-mentioned anode may include a current collector and a negative electrode active material layer formed on the current collector. In addition, the anode may be the same as the anode in the first and second embodiments described above.

[0402] The separator may be interposed between the cathode and the anode. The separator may be the same as the separator in the first and second embodiments described above.

[0403] The above electrolyte may be a non-aqueous electrolyte. The above electrolyte may be the same as the electrolyte in the first and second embodiments described above.

[0404] The above positive electrode, negative electrode, and separator can be manufactured into an electrode assembly by a winding, lamination, folding, or zigzag stacking process. The electrode assembly can be the same as the electrode assembly in the first and second embodiments described above.

[0405] It can be manufactured into a secondary battery by being provided with the above electrolyte. The secondary battery can be any one of a cylindrical shape using a can, a square shape, a pouch shape, and a coin shape, but is not limited thereto.

[0406] The above secondary battery can be used in a high-output and large-capacity secondary battery that requires a long lifespan and excellent durability, or in a module or pack that includes multiple of the above secondary batteries as unit batteries.

[0407] The above-described plurality of secondary batteries can be manufactured as modules. The above-described plurality of modules can be manufactured as a pack. The above-described plurality of modules and pack may be the same as the modules and packs in the first and second embodiments described above.

[0408]

[0409] Hereinafter, the present invention will be described in more detail based on examples and comparative examples. However, the following examples and comparative examples are merely illustrative examples for further explaining the present invention, and the present invention is not limited to the following examples and comparative examples.

[0410]

[0411] Manufacturing Example 1 - Preparation of primer composition

[0412] - Challenge #1: Acetylene black (average particle size: 0.05 ㎛, oil absorption capacity: 117 ml / 100 g)

[0413] - Challenge #2: Graphite (average particle size: 17 ㎛)

[0414] - Challenge #3: Carbon black (average particle size: 0.15 ㎛)

[0415] - Challenge #4: Multi-walled carbon nanotubes (average length: 20 μm, average diameter: 15 nm)

[0416]

[0417] Manufacturing Example 1-1

[0418] A first mixture was prepared by mixing polyvinylpyrrolidone as a dispersant, conductive agent #1, and conductive agent #2 in distilled water.

[0419] A primer composition was prepared by mixing poly(acrylic acid-co-acrylamide) (PAA-PAM) as a binder into the first mixture, and the specific specifications are shown in Table 1 below.

[0420]

[0421] Manufacturing Examples 1-2 to 1-8 and Comparative Manufacturing Examples 1-1 to 1-10

[0422] A primer composition was manufactured by the same process as Manufacturing Example 1-1, except that the primer composition was manufactured according to the specifications shown in Table 1 below.

[0423]

[0424] Dispersant Binder Solvent Challenger #1 Challenger #2 Challenger #3 Challenger #4 PVP 1) PAA-PAM 2) Distilled water unit weight % 3) Manufacturing example 1-136--0.55 Residue Manufacturing example 1-233--0.55 Residue Manufacturing example 1-339--0.55 Residue Manufacturing example 1-455--0.55 Residue Manufacturing example 1-5510--0.55 Residue Manufacturing example 1-6515--0.55 Residue Manufacturing example 1-71010--0.55 Residue Manufacturing example 1-81020--0.55 Residue Comparison Manufacturing example 1-1--10-0.55 Residue Comparison Manufacturing example 1-210---0.55 Residue Comparison Manufacturing example 1-3-10--0.55 Residue Comparison Manufacturing example 1-4-63-0.55 Residue Comparison Manufacturing example 1-5-33-0.55 Residue Comparison Manufacturing example 1-6-93-0.55 Residue Comparative Manufacturing Example 1-731.5--0.55 Residue Comparative Manufacturing Example 1-8312--0.55 Residue Comparative Manufacturing Example 1-9-33-0.515 Residue Comparative Manufacturing Example 1-103--0.50.55 Residue 1) PVP: Polyvinylpyrrolidone 2) PAA-PAM: Poly(acrylic acid-co-acrylamide) 3) Weight %: Solid weight of each conductive agent, dispersant, and binder

[0425]

[0426] Example 1

[0427] Example 1-1

[0428] <Cathode manufacturing>

[0429] The primer composition of Manufacturing Example 1 was applied to a 20 ㎛ thick aluminum current collector with a thickness of 1 ㎛, and then dried at 100 ℃ to produce a primer layer.

[0430] Li[Ni], a cathode active material, in distilled water 0.8 Co 0.1 Mn 0.1]O2, conductive agent #3, and polyvinylidene fluoride (PVdF) as a binder were mixed in a weight ratio of 8:1:1 to prepare a slurry. The slurry was uniformly applied onto the primer layer, dried at 100°C, and rolled to prepare a positive electrode.

[0431] <Secondary Battery (Coin Full Cell) Manufacturing>

[0432] A polyethylene separator was interposed between the positive electrode and the carbon-based negative electrode manufactured above, and an electrolyte solution containing a lithium salt of 1M LiFP6 dissolved in a mixed solvent of ethylene carbonate:diethyl carbonate:ethylmethyl carbonate having a volume ratio of 2:2:4 was injected to manufacture a coin full cell.

[0433]

[0434] Examples 1-2 to 1-8

[0435] A coin full cell was manufactured by the same process as Example 1-1, except that the primer composition shown in Table 2 below was used.

[0436]

[0437] Comparative Example 1-1

[0438] In the above Example 1-1, a coin full cell was manufactured by the same process as Example 1-1, except that the positive electrode was manufactured without forming a primer layer on the aluminum current collector.

[0439]

[0440] Comparative Examples 1-2 to 1-11

[0441] A coin full cell was manufactured by the same process as Example 1-1, except that the primer composition shown in Table 2 below was used.

[0442]

[0443] Experimental Example 1

[0444] Experimental Example 1-1 - Adhesive Strength

[0445] Each of the anodes manufactured in Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-11 was punched to a size of 20 mm × 120 mm to manufacture a test piece. After attaching double-sided tape to a slide glass, the test piece was attached, and after 10 round trips using a 2 kg roller, it was pressed.

[0446] The above specimen was placed in a universal testing machine and pulled at a speed of 300 mm / min, and the adhesive strength at which the specimen was peeled off from the slide glass was measured. The measurement section was 50 mm, and the measurement angle between the slide glass and the electrode was 90°. The measurement results are shown in Table 2 below.

[0447]

[0448] Experimental Example 1-2 - Viscosity

[0449] For each primer composition manufactured in the above Manufacturing Examples 1-1 to 1-8 and Comparative Manufacturing Examples 1-1 to 1-10, a Brookfield viscometer was used at room temperature and a shear rate of 10 s. -1 The viscosity was measured, and the results are shown in Table 2 below.

[0450]

[0451] Experimental Example 1-3 - Pinhole Evaluation

[0452] For each of the positive electrodes manufactured in Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-11, the positive electrode 10 cm 2 The number of pinholes with a diameter of 200 μm or more per area was measured five times, and the average value was calculated. The results were evaluated according to the following criteria, and are shown in Table 2.

[0453] - ○: Number of pinholes: 5 or less

[0454] - ×: Number of pinholes exceeds 5

[0455]

[0456] Experimental Example 1-4 - Impurity Content

[0457] For each primer composition manufactured in Manufacturing Examples 1-1 to 1-8 and Comparative Manufacturing Examples 1-1 to 1-10, the content of transition metal impurities was measured using inductively coupled plasma mass spectrometry, and the results are shown in Table 3 below.

[0458]

[0459] Experimental Example 1-5 - Initial Efficiency

[0460] For each coin pool cell manufactured in Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-11, formation was performed by performing one charge / discharge cycle at 0.1 C, and then the initial charge / discharge characteristics were confirmed by one charge / discharge cycle at 0.2 C. The initial efficiency was calculated according to the following equation, and the results are shown in Table 4 below.

[0461] The above charging and discharging process was performed under room temperature conditions. When charging, it started in CC (constant current) mode and then changed to CV (constant voltage) to set the cutoff at 4.3 V. When discharging, it was set in CC (constant current) mode to cutoff at 1.5 V from 2.75 V.

[0462] [ceremony]

[0463] Initial efficiency (%) = (discharge capacity in 1 cycle) / (charge capacity in 1 cycle) Х 100

[0464]

[0465] Experimental Example 1-6 - Life Characteristics

[0466] For each coin pool cell manufactured in Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-11, charge / discharge was repeated 300 times under the same conditions as in Experimental Example 1-5, and then the discharge capacity was measured, and the capacity retention rate compared to the discharge capacity in one cycle of Experimental Example 1-5 was measured. The results are shown in Table 4 below.

[0467]

[0468] Experimental Example 1-7 - High-rate discharge characteristics

[0469] For each coin pool cell manufactured in Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-11, the cell was charged under constant current (0.1 C) and constant voltage (1.0 V, 0.01 C cut-off) conditions, rested for 10 minutes, and discharged under constant current (0.2 C, 0.5 C, 1 C, 2 C, or 3 C) conditions until the voltage reached 2.5 V.

[0470] As the number of charge / discharge cycles increased, the rate capability of each coin full cell was evaluated according to the following equation by periodically changing the discharge rate to 0.2 C, 0.5 C, 1 C, 2 C, and 3 C, respectively. The full cell was discharged at a rate of 0.2 C for 1 to 3 charge / discharge cycles, and the results are shown in Table 4 below.

[0471] [ceremony]

[0472] High-rate discharge characteristics (%) = (discharge capacity when discharging a full cell at a rate of 3 C) / (discharge capacity when discharging a full cell at a rate of 0.2 C) Х 100

[0473]

[0474] Classification Primer Composition Adhesion Viscosity Pinhole Evaluation Unit - gf / 20 mmcPs - Example 1-1 Manufacturing Example 1-1 27.7815 ○ Example 1-2 Manufacturing Example 1-2 26.1956 ○ Example 1-3 Manufacturing Example 1-3 27.38520 ○ Example 1-4 Manufacturing Example 1-4 28.9110 ○ Example 1-5 Manufacturing Example 1-5 30.1376 ○ Example 1-6 Manufacturing Example 1-6 29.8310 ○ Example 1-7 Manufacturing Example 1-7 27.9236 ○ Example 1-8 Manufacturing Example 1-8 28.1512 ○ Comparative Example 1-1-19.8 - ○ Comparative Example 1-2 Comparative Manufacturing Example 1-113.3452 ○ Comparative Example 1-3 Comparative Manufacturing Example 1-223.8672 ○ Comparative Example 1-4 Comparative Manufacturing Example 1-315.8353 ○ Comparative Example 1-5 Comparative Manufacturing Example 1-417.6234 ○ Comparative Example 1-6 Comparative Manufacturing Example 1-516.5123 ○ Comparative Example 1-7 Comparative Manufacturing Example 1-618.1383 ○ Comparative Example 1-8 Comparative Manufacturing Example 1-719.2545 ○ Comparative Example 1-9 Comparative Manufacturing Example 1-820.1452 ○ Comparative Example 1-10 Comparative Manufacturing Example 1-939.53,210 × Comparative Example 1-11 Comparative Manufacturing Example 1-1015.2234 ○

[0475]

[0476] ClassificationImpurity contentFeCoCrCuMnNiZnUnitmg / kgExample 1-11.01060.25<0.12<0.03<0.28<0.15Example 1-21.11050.22<0.12<0.03<0.28<0.15Manufacturing example 1-31.11060.22<0.12<0.03<0.28<0.15Manufacturing example 1-41.01000.21<0.12<0.03<0.28<0.15Manufacturing example 1-51.41150.21<0.12<0.03<0.28<0.15Manufacturing example 1-61.01100.23< 0.12< 0.03< 0.28< 0.15 Manufacturing example 1-71.01100.22< 0.12< 0.03< 0.28< 0.15 Manufacturing example 1-81.01150.22< 0.12< 0.03< 0.28< 0.15 Comparative manufacturing example 1-11.31100.25< 0.12< 0.03< 0.28< 0.15 Comparative manufacturing example 1-21.21150.26< 0.12< 0.03< 0.28< 0.15 Comparative manufacturing example 1-31.41200.25< 0.12< 0.03< 0.28< 0.15Comparative Manufacturing Example 1-41.51200.21< 0.12< 0.03< 0.28< 0.15Comparative Manufacturing Example 1-51.61100.22< 0.12< 0.03< 0.28< 0.15Comparative Manufacturing Example 1-61.31200.23< 0.12< 0.03< 0.28< 0.15Comparative Manufacturing Example 1-71.41150.23< 0.12< 0.03< 0.28< 0.15Comparative Manufacturing Example 1-81.51100.25< 0.12< 0.03< 0.28< 0.15Comparative Manufacturing Example 1-91.81100.25< 0.12< 0.03< 0.28< 0.15Comparative manufacturing example 1-102,2501800.25< 0.12< 0.03220< 0.15

[0477]

[0478] Initial efficiency, lifespan, high-rate discharge, charge capacity 1) Discharge capacity 2)Initial Efficiency Capacity Retention Rate Discharge Capacity (@0.2C) Discharge Capacity (@0.5C) Discharge Capacity (@1C) Discharge Capacity (@2C) Discharge Capacity (@3C) High Rate Discharge Characteristic Unit mAh% mAh% Example 1-1 189.4 165.687.476 160.2 156.3 153.6 150.2 146.59 1.4 Example 1-2 190.2 165.887.275 160.1 156.2 153.1 150.7 146.19 1.3 Example 1-3 188.2 165.888.174 158.9 155.9 153.6 149.2 145.59 1.6 Example 1-4 189.1 165.687.674 158.6 156.3 153.4 150.3 145.39 1.4 Example 1-5 188.1 164.9 87.775157.2156.1154.6150.1146.593.2Embodiment 1-6189.5164.787.074158.3156.4153.6149.4146.292.4Embodiment 1-7189.4165.687.475160.2156.3153.6150.2146.591.4Embodiment 1-8190.2165.887.275160.1156.2153.1150.7146.191.3Comparative Example 1-1188.5142.575.652140.1128.5115.290.569. 349.5Comparative Example 1-2186.2153.682.568150.6145.5135.1130.2125.283.1Comparative Example 1-3185.1152.082.167150.1145.4135.2130.1124.883.1Comparative Example 1-4184.3149.881.365145.6141.3135.1129.2122.784.3Comparative Example 1-5187.1154.082.366151.6145.3133.1130.4125.582.8Comparative Example 1-6184.2150.181.5671 48.2142.3132.2130.3122.282.5Comparative Example 1-7183.2147.580.568144.6139.5131.4129.2120.583.3Comparative Example 1-8181.2148.481.965145.4141.6130.9128.2121.783.7Comparative Example 1-9182.2146.580.465142.1138.5129.3127.4119.484.0Comparative Example 1-10178.5141.479.263139.5135.4129.2120.6113.881.6Comparative Example 1-11187.4163.287.161158.2140.5135.2129.5122.977.71) Charge capacity: Charge capacity in one cycle2) Discharge capacity: Discharge capacity in one cycle.

[0479]

[0480] As can be seen in Tables 1 to 4 above, Examples 1-1 to 1-8, which contain two types of conductive materials having average particle diameters satisfying a specific range in a ratio of 1:1 to 1:3, showed improved adhesive strength, reduced impurity content, improved pinhole generation problems, and improved initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery compared to Comparative Examples 1-1 to 1-11.

[0481] Specifically, it was confirmed that Examples 1-1 to 1-8 had superior interfacial adhesion between the current collector and the positive electrode active material layer compared to Comparative Example 1-1 in which no primer layer was formed, thereby improving the electrode detachment problem and thus improving the characteristics of the secondary battery. In addition, it was confirmed that Examples 1-1 to 1-8 had improved pinhole generation problems and thus improved the characteristics of the secondary battery compared to Comparative Example 1-10 in which the adhesive strength was improved by increasing the binder content. In addition, it was confirmed that Examples 1-1 to 1-8 had reduced impurities and had superior interfacial adhesion between the current collector and the positive electrode active material layer compared to Comparative Example 1-11 in which a linear conductive agent, multi-walled carbon nanotubes, were included, thereby improving the life characteristics and high-rate discharge characteristics of the secondary battery.

[0482]

[0483] Manufacturing Example 2 - Manufacturing of Primer Composition

[0484] - Challenge #1: Acetylene black (average particle size: 0.05 ㎛)

[0485] - Challenge #2: Carbon black (average particle size: 0.15 ㎛)

[0486] - Challenge #3: Graphite (average particle size: 18 ㎛)

[0487] - PVP #1: polyvinylpyrrolidone (Mw: 40,000 g / mol)

[0488] - PVP #2: polyvinylpyrrolidone (Mw: 2,500,000 g / mol)

[0489] - PAA: polyacrylic acid (Mw: 100,000 g / mol)

[0490] - PE: Water-dispersible polyester (Mw: 100,000 g / mol)

[0491] - PAM-PAA: poly(acrylamide-co-acrylic acid) (Mw: 250,000 g / mol)

[0492]

[0493] Manufacturing Example 2-1

[0494] A first mixture was prepared by mixing PVP #1 as a dispersant and conductive agent #1 in distilled water.

[0495] A primer composition was prepared by mixing PAM-PAA as a binder into the first mixture, and the specific specifications are shown in Table 5 below.

[0496]

[0497] Manufacturing Examples 2-2 to 2-6 and Comparative Manufacturing Examples 2-1 to 2-7

[0498] A primer composition was manufactured by the same process as Manufacturing Example 2-1, except that the primer composition was manufactured according to the specifications shown in Table 5 below.

[0499]

[0500] DispersantBinderSolventConductor #1Conductor #2Conductor #3PVP #1PAAPAM-PAAPEPVP #2Distilled waterUnit weight% 1)Manufacturing Example 2-15--3-4--Residue Manufacturing Example 2-25--1.5-4--Residue Manufacturing Example 2-35--1.5-9--Residue Manufacturing Example 2-45--1.5--9-Residue Manufacturing Example 2-55--1.5---9-Residue Manufacturing Example 2-623-1.5--9-Residue Manufacturing Example 2-75-101.5--9-Residue Comparison Manufacturing Example 2-13---4.03--Residue Comparison Manufacturing Example 2-2-5-1.5-4--Residue Comparison Manufacturing Example 2-3-5-1.5--9-Residue 1) Weight %: Solid weight of each conductive agent, dispersant, and binder

[0501]

[0502] Second Example

[0503] Example 2-1

[0504] <Cathode manufacturing>

[0505] The primer composition of Manufacturing Example 1 was applied to a 20 ㎛ thick aluminum current collector with a thickness of 1 ㎛, and then dried at 100 ℃ to produce a primer layer.

[0506] Li[Ni], a cathode active material, in distilled water 0.8 Co 0.1 Mn 0.1 ]O2, conductive agent #3, and polyvinylidene fluoride (PVdF) as a binder were mixed in a weight ratio of 8:1:1 to prepare a slurry. The slurry was uniformly applied onto the primer layer, dried at 100°C, and rolled to prepare a positive electrode.

[0507] <Secondary Battery (Coin Full Cell) Manufacturing>

[0508] A polyethylene separator was interposed between the positive electrode and the carbon-based negative electrode manufactured above, and an electrolyte solution containing a lithium salt of 1M LiFP6 dissolved in a mixed solvent of ethylene carbonate:diethyl carbonate:ethylmethyl carbonate having a volume ratio of 2:2:4 was injected to manufacture a coin full cell.

[0509]

[0510] Examples 2-2 to 2-7

[0511] A coin full cell was manufactured by the same process as Example 2-1, except that the primer composition shown in Table 6 below was used.

[0512]

[0513] Comparative Example 2-1

[0514] In the above Example 2-1, a coin full cell was manufactured by the same process as Example 2-1, except that the positive electrode was manufactured without forming a primer layer on the aluminum current collector.

[0515]

[0516] Comparative Examples 2-2 to 2-4

[0517] A coin full cell was manufactured by the same process as Example 2-1, except that the primer composition shown in Table 6 below was used.

[0518]

[0519] Experimental Example 2

[0520] Experimental Example 2-1 - Adhesive Strength

[0521] Each of the anodes manufactured in Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-4 was punched out to a size of 20 mm × 120 mm to manufacture a test piece. After attaching double-sided tape to a slide glass, the test piece was attached, and after 10 round trips using a 2 kg roller, it was pressed.

[0522] After the above specimen was placed in a universal testing machine and pulled at a speed of 300 mm / min, the adhesive strength at which the specimen was peeled off from the slide glass was measured. At this time, the measurement section was 50 mm, and the measurement angle between the slide glass and the electrode was 90°. The measurement results are shown in Table 6 below.

[0523]

[0524] Experimental Example 2-2 - Viscosity

[0525] For each primer composition manufactured in the above Manufacturing Examples 2-1 to 2-7 and Comparative Manufacturing Examples 2-1 to 2-3, a Brookfield viscometer was used at room temperature and a shear rate of 10 s. -1 The viscosity was measured, and the results are shown in Table 6 below.

[0526]

[0527] Experimental Example 2-3 - LSV

[0528] For each of the secondary batteries manufactured in Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-4, the electrolyte decomposition range was measured using linear sweep voltammetry. Half cells were manufactured using an aluminum current collector formed with the primer layer as a working electrode and lithium metal as a reference electrode, and the voltage was scanned at a rate of 0.1 mV / s from 0 V to 5.5 V versus the lithium metal. The voltage range at 0.05 mA was measured, and the results are shown in Table 6 below.

[0529]

[0530] Experimental Example 2-4 - Initial Efficiency

[0531] For each coin pool cell manufactured in Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-4, formation was performed by performing one charge / discharge cycle at 0.1 C, and then the initial charge / discharge characteristics were confirmed by one charge / discharge cycle at 0.2 C. The initial efficiency was calculated according to the following equation, and the results are shown in Table 7 below.

[0532] The above charging and discharging process was performed under room temperature conditions. When charging, it started in CC (constant current) mode and then changed to CV (constant voltage) to set the cutoff at 4.3 V. When discharging, it was set in CC (constant current) mode to cutoff at 1.5 V from 2.75 V.

[0533] [ceremony]

[0534] Initial efficiency (%) = (discharge capacity in 1 cycle) / (charge capacity in 1 cycle) Х 100

[0535]

[0536] Experimental Example 2-5 - Lifespan Characteristics

[0537] For each coin pool cell manufactured in Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-4, charge / discharge was repeated 300 times under the same conditions as in Experimental Example 2-4, and then the discharge capacity was measured, and the capacity retention rate compared to the discharge capacity in one cycle of Experimental Example 2-4 was measured. The results are shown in Table 7 below.

[0538]

[0539] Experimental Example 2-6 - High-rate discharge characteristics

[0540] For each coin full cell manufactured in Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-4, the cell was charged under constant current (0.1 C) and constant voltage (1.0 V, 0.01 C cut-off) conditions, rested for 10 minutes, and discharged under constant current (0.2 C, 0.5 C, 1 C, 2 C, or 3 C) conditions until the voltage reached 2.5 V.

[0541] As the number of charge / discharge cycles increased, the rate capability of each coin full cell was evaluated according to the following equation by periodically changing the discharge rate to 0.2 C, 0.5 C, 1 C, 2 C, and 3 C, respectively. The full cell was discharged at a rate of 0.2 C for 1 to 3 charge / discharge cycles, and the results are shown in Table 7 below.

[0542] [ceremony]

[0543] High-rate discharge characteristics (%) = (discharge capacity when discharging a full cell at a rate of 3 C) / (discharge capacity when discharging a full cell at a rate of 0.2 C) Х 100

[0544]

[0545] Adhesion of the primer composition Adhesion increase / decrease rate 1) Viscosity LSV Unit - gf / 20 mm % cPsV Example 2-1 Manufacturing Example 2-1 12.76 120 8 15 4.80 Example 2-2 Manufacturing Example 2-2 12.5 4 118 9 5 6 4.52 Example 2-3 Manufacturing Example 2-3 12.2 2 115 2,5 20 4.53 Example 2-4 Manufacturing Example 2-4 13.8 2 130 110 4.57 Example 2-5 Manufacturing Example 2-5 12.6 5 119 3 7 4.58 Example 2-6 Manufacturing Example 2-6 12.86 121 110 4.57 Example 2-7 Manufacturing Example 2-7 21.2 6 20 0 136 4.57 Comparative Example 2-1 - 10.63 - 4.50 Comparative Example 2-2 Comparative Manufacturing Example 2-16.91652514.89 Comparative Example 2-3 Comparative Manufacturing Example 2-28.72826524.80 Comparative Example 2-4 Comparative Manufacturing Example 2-38.1977824.571) Adhesive strength increase / decrease rate: Based on the adhesive strength of Comparative Example 2-1

[0546]

[0547] Initial efficiency, lifespan, high-rate discharge, charge capacity 1) Discharge capacity 2)Initial Efficiency Capacity Retention Rate Discharge Capacity (@0.2C) Discharge Capacity (@0.5C) Discharge Capacity (@1C) Discharge Capacity (@2C) Discharge Capacity (@3C) High Rate Discharge Characteristics Unit mAh% mAh% Example 2-1 189.5 165.7 87.475 160.1 156.2 153.3 150.1 146.2 9 1.3 Example 2-2 190.3 165.3 86.974 160.3 156.4 153.2 150.6 146.3 9 1.3 Example 2-3 188.2 165.8 88.175 158.915 5.9153.6149.2145.591.6Example 2-4189.3165.787.575158.5156.2153.5150.1145.391.7Example 2-5188.2165.187.773157.1155.9153.6150.1146.193.0Example 2-6189.5164.787. 074158.3156.4153.6149.4146.292.4Example 2-7189.4165.687.475160.2156.3153.6150.2146.591.4Comparative Example 2-1188.5140.574.552138.1128.1116.291.569.250.1Comparative Example 2-2186.2 152.682.068150.1144.5135.2130.1123.282.1Comparative Example 2-3185.1151.081.668149.2144.4135.1130.2122.882.3Comparative Example 2-4184.3148.780.766145.6142.3135.4129.2121.783.61) Charge capacity: Charge capacity in one cycle2) Discharge capacity: Discharge capacity in one cycle

[0548]

[0549] As can be seen in Tables 5 to 7 above, in Examples 2-1 to 2-7, a primer layer is formed, and a conductive material having an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛ and a polyvinyl-based compound as a dispersant are included as a primer composition. Compared to Comparative Examples 2-1 to 2-4, the interfacial adhesive strength between the current collector and the active material layer is improved, and the dispersibility of the conductive material is improved, so that the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery are improved.

[0550]

[0551] Manufacturing example 3

[0552] - Challenge #1: Carbon black (average particle size: 0.15 ㎛)

[0553] - Challenge #2: Graphite (average particle size: 18 ㎛)

[0554] - Challenge #3: Acetylene black (average particle size: 0.05 ㎛)

[0555] - Cathode active material #1: LiFePO4 (average particle size: 1.2 ㎛)

[0556] -Cathode active material #2: Li[Ni 0.8 Co 0.1 Mn 0.1 ]O2 (average particle size: 10 ㎛)

[0557]

[0558] Manufacturing Example 3-1

[0559] A first mixture was prepared by mixing polyvinylpyrrolidone as a dispersant and conductive agent #1 in distilled water.

[0560] A primer composition was prepared by mixing poly(acrylic acid-co-acrylamide) (PAA-PAM) as a binder into the first mixture, and the specific specifications are shown in Table 8 below.

[0561]

[0562] Manufacturing Examples 3-2 to 3-6 and Comparative Manufacturing Examples 3-1 to 3-11

[0563] A primer composition was manufactured by the same process as Manufacturing Example 3-1, except that the primer composition was manufactured according to the specifications shown in Table 8 below.

[0564]

[0565] Dispersant Binder Solvent Challenger #1 Challenger #2 Challenger #3 PVP 1) PAA-PAM 2) Distilled water unit weight % 3)Manufacturing example 3-15--0.55 Residue Manufacturing example 3-26--0.55 Residue Manufacturing example 3-34--0.55 Residue Manufacturing example 3-4-1050.55 Residue Manufacturing example 3-5-1040.55 Residue Manufacturing example 3-6-860.55 Residue Comparison Manufacturing example 3-1-7-0.55 Residue Comparison Manufacturing example 3-2-5-0.55 Residue Comparison Manufacturing example 3-3-1050.55 Residue Comparison Manufacturing example 3-4510-0.55 Residue Comparison Manufacturing example 3-5--50.55 Residue Comparison Manufacturing example 3-6--50.520 Residue Comparison Manufacturing example 3-7--50.55 Residue Comparison Manufacturing example 3-8510-0.55 Residue Comparison Manufacturing example 3-95--0.55 balance Comparative manufacturing example 3-10-10-0.55 balance Comparative manufacturing example 3-115--0.520 balance 1) PVP: polyvinylpyrrolidone 2) PAA-PAM: poly(acrylic acid-co-acrylamide) 3) Weight %: solid weight of each conductive agent, dispersant, and binder

[0566]

[0567] Third Example

[0568] Example 3-1

[0569] <Cathode manufacturing>

[0570] The primer composition of Manufacturing Example 3-1 was applied to a 20 ㎛ thick aluminum collector with a thickness of 1 ㎛, and then dried at 100 ℃ to produce a primer layer.

[0571] A slurry was prepared by mixing positive electrode active material #1, conductive material #2, and polyvinylidene fluoride (PVdF) as a binder in distilled water at a weight ratio of 8:1:1. The slurry was uniformly applied onto the primer layer, dried at 100°C, and rolled to prepare a positive electrode.

[0572] <Secondary Battery (Coin Full Cell) Manufacturing>

[0573] A polyethylene separator was interposed between the positive electrode and the carbon-based negative electrode manufactured above, and an electrolyte solution containing a lithium salt of 1M LiFP6 dissolved in a mixed solvent of ethylene carbonate:diethyl carbonate:ethylmethyl carbonate having a volume ratio of 2:2:4 was injected to manufacture a coin full cell.

[0574]

[0575] Examples 3-2 to 3-6

[0576] A coin full cell was manufactured by the same process as Example 3-1, except that the primer composition and positive electrode active material shown in Table 9 below were used.

[0577]

[0578] Comparative Examples 3-1 and 3-8

[0579] A coin full cell was manufactured using the positive electrode active material shown in Table 9 below, and using the same process as Example 3-1, except that the positive electrode was manufactured without forming a primer layer on the aluminum current collector in Example 1.

[0580]

[0581] Comparative Examples 3-2 to 3-7 and Comparative Examples 3-9 to 3-13

[0582] A coin full cell was manufactured by the same process as Example 3-1, except that the primer composition and positive electrode active material shown in Table 9 below were used.

[0583]

[0584] Experimental Example 3

[0585] Experimental Example 3-1 - Adhesive Strength

[0586] Each of the anodes manufactured in Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-13 was punched out to a size of 20 mm × 120 mm to manufacture a test piece. After attaching double-sided tape to a slide glass, the test piece was attached, and after 10 round trips using a 2 kg roller, it was pressed.

[0587] After the above specimen was placed in a universal testing machine and pulled at a speed of 300 mm / min, the adhesive strength at which the specimen was peeled off from the slide glass was measured. At this time, the measurement section was 50 mm, and the measurement angle between the slide glass and the electrode was 90°. The measurement results are shown in Tables 10 and 11 below.

[0588]

[0589] Experimental Example 3-2 - Interface Stability Evaluation

[0590] After measuring the adhesive strength in Experimental Example 3-1, the separation location was visually confirmed for each of the positive electrodes of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-13. The evaluation was conducted according to the following criteria, and the results are shown in Tables 10 and 11 below.

[0591] - Good: Separation occurs in the positive electrode active material layer.

[0592] - Defect: Separation occurs at the interface between the positive active material layer and the primer layer or at the interface between the positive active material layer and the current collector.

[0593]

[0594] Experimental Example 3-3 - Initial Efficiency

[0595] For each coin pool cell manufactured in Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-13, formation was performed by performing one charge / discharge cycle at 0.1 C, and then the initial charge / discharge characteristics were confirmed by one charge / discharge cycle at 0.2 C. The initial efficiency was calculated according to the following calculation formula, and the results are shown in Table 12 below.

[0596] The above charging and discharging process was performed under room temperature conditions. When charging, it started in CC (constant current) mode and then changed to CV (constant voltage) to set the cutoff at 4.3 V. When discharging, it was set in CC (constant current) mode to cutoff at 1.5 V from 2.75 V.

[0597] [Calculation formula]

[0598] Initial efficiency (%) = (discharge capacity in 1 cycle) / (charge capacity in 1 cycle) Х 100

[0599]

[0600] Experimental Example 3-4 - Lifespan Characteristics

[0601] For each coin pool cell manufactured in Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-13, charge / discharge was repeated 300 times under the same conditions as in Experimental Example 3-3, and then the discharge capacity was measured, and the capacity retention rate compared to the discharge capacity in one cycle of Experimental Example 3-3 was measured. The results are shown in Table 12 below.

[0602]

[0603] Experimental Example 3-5 - High-rate discharge characteristics

[0604] For each coin full cell manufactured in Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-13, the cell was charged under constant current (0.1 C) and constant voltage (1.0 V, 0.01 C cut-off) conditions, rested for 10 minutes, and discharged under constant current (0.2 C, 0.5 C, 1 C, 2 C, or 3 C) conditions until the voltage reached 2.5 V.

[0605] As the number of charge / discharge cycles increased, the rate capability of each coin full cell was evaluated according to the following calculation formula by periodically changing the discharge rate to 0.2 C, 0.5 C, 1 C, 2 C, and 3 C, respectively. The full cell was discharged at a rate of 0.2 C for 1 to 3 charge / discharge cycles, and the results are shown in Table 12 below.

[0606] [Calculation formula]

[0607] High-rate discharge characteristics (%) = (discharge capacity when discharging a full cell at a rate of 3 C) / (discharge capacity when discharging a full cell at a rate of 0.2 C) Х 100

[0608]

[0609] Whether a primer layer is formedPrimer compositionCathode active materialExample 3-1○Manufacturing example 3-1Cathode active material #1Example 3-2○Manufacturing example 3-2Example 3-3○Manufacturing example 3-3Comparative example 3-1×-Comparative example 3-2○Comparative manufacturing example 3-1Comparative example 3-3○Comparative manufacturing example 3-2Comparative example 3-4○Comparative manufacturing example 3-3Comparative example 3-5○Comparative manufacturing example 3-4Comparative example 3-6○Comparative manufacturing example 3-5Comparative example 3-7○Comparative manufacturing example 3-6Example 3-4○Manufacturing example 3-4Cathode active material #2Example 3-5○Manufacturing example 3-5Example 3-6○Manufacturing example 3-6Comparative example 3-8×-Comparative example 3-9○Comparative Manufacturing Example 3-7 Comparative Example 3-10 ○ Comparative Manufacturing Example 3-8 Comparative Example 3-11 ○ Comparative Manufacturing Example 3-9 Comparative Example 3-12 ○ Comparative Manufacturing Example 3-10 Comparative Example 3-13 ○ Comparative Manufacturing Example 3-11

[0610]

[0611] Whether the average particle size of the conductive material in the separation primer layer is less than 5 ㎛ Formula 1 1)SatisfactionAdhesionInterface adhesion evaluation unit-gf / 20mm-Example 3-1○○22.0GoodExample 3-2○○22.5GoodExample 3-3○○22.3GoodComparative Example 3-1--4.2PoorComparative Example 3-2×-7.2PoorComparative Example 3-3×-6.5PoorComparative Example 3-4×-6.1PoorComparative Example 3-5×-7.7PoorComparative Example 3-6○×13.5PoorComparative Example 3-7○×32.5Good1) Formula 1: 5 % < (X1 / A1) Х 100 < 35 %In the above formula, X1 is the average particle diameter of the conductive material #1, and A1 is the average particle diameter of the positive electrode active material #1.

[0612]

[0613] Whether conductive materials with an average particle size of 5 ㎛ or more are included Whether conductive materials with different average particle sizes are included Formula 2 2) Satisfaction Test 3 3) Satisfaction AdhesionInterface adhesiveness Evaluation unit-gf / 20mm-Example 3-4○○○○32.2GoodExample 3-5○○○○33.5GoodExample 3-6○○○○34.9GoodComparative Example 3-8----9.2PoorComparative Example 3-9××××16.7PoorComparative Example 3-10○○○×21.2PoorComparative Example 3-11××××27.9PoorComparative Example 3-12○×○×20.5PoorComparative Example 3-13××××48.5Good2) Formula 2: 100 % < (X2 / A2) Х 100 < 300 %3) Formula 3: 0.05 % < (X3 / X2) Х 100 < 0.7 %In the above formulas 2 and 3, the X2 is a conductive material #2 is the average particle size, X3 is the average particle size of the conductive material #3, and A2 is the average particle size of the positive electrode active material #2.

[0614]

[0615] Initial efficiency, lifespan, high-rate discharge, charge capacity 1) Discharge capacity 2)Initial Efficiency Capacity Retention Rate Discharge Capacity (@0.2C) Discharge Capacity (@0.5C) Discharge Capacity (@1C) Discharge Capacity (@2C) Discharge Capacity (@3C) High Rate Discharge Characteristic Unit mAh% mAh% Example 3-1158.5130.882.562125.5115.4108.396.588.370.4 Example 3-2157.6128.181.361122.4114.1107.393.385.169.5 Example 3-3155.4127.982.362122.5115.2108.196.285.970.1 Comparative Example 3-1151.5117.477.535110.591.265.350.533.930.7 Comparative Example 3-2153.2119.878.241113.5 103.579.260.248.943.1Comparative Example 3-3150.4116.777.640112.2103.380.161.148.443.1Comparative Example 3-4150.2117.378.142113.9101.181.163.247.541.7Comparative Example 3-5152.6117.877.240112.6100.882.362.446.541.3Comparative Example 3-6152.1119.178.339111.3103.280.361.545.540.9Comparative Example 3-7150.3116.577.53 2110.293.177.351.734.431.2Embodiment 3-4189.3165.787.575158.3156.1153.5150.0145.391.8Embodiment 3-5188.2165.187.774157.0155.3153.6150.2146.193.1Embodiment 3-6189.5164.787.075158.1156.2153.6149.6146.292.5Comparative Example 3-8185.2155.584.065139.6131.5127.7109.273.452.6Comparative Example 3- 9180.3152.284.469150.5145.6132.1125.4119.079.1Comparative Example 3-10181.3155.085.568150.2145.3132.0125.2121.280.7Comparative Example 3-11182.5153.784.269149.5145.1131.2123.1116.577.9Comparative Example 3-12181.3153.084.469148.1144.6130.1122.1121.682.1Comparative Example 3-13185.2155.584.063138.6130.5125.7103.170.350.71) Charge capacity: Charge capacity in one cycle2) Discharge capacity: Discharge capacity in one cycle.

[0616]

[0617] As can be seen in Tables 8 to 12 above, Examples 3-1 to 3-3 and Comparative Examples 3-1 to 3-7 include a lithium iron oxide-based positive electrode active material having an average particle size of less than 5 μm.

[0618] Examples 3-1 to 3-3 included a conductive material having an average particle diameter of less than 5 ㎛ in the primer layer, and the relationship between the average particle diameter of the conductive material included in the primer layer and the average particle diameter of the positive electrode active material included in the positive electrode active material layer satisfied Equation 1, thereby improving the interfacial adhesive strength between the current collector and the active material layer compared to Comparative Examples 3-2 to 3-6, thereby improving the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery.

[0619] In addition, in Comparative Example 3-1, in which no primer layer was formed, the interfacial adhesive strength between the current collector and the active material layer was significantly reduced compared to Examples 3-1 to 3-3, and in Comparative Example 3-7, in which the binder content was increased to improve the adhesive strength, the interfacial adhesive strength between the current collector and the active material layer was improved, but it was confirmed that the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery were deteriorated compared to Examples 3-1 to 3-3 due to the increase in the binder content.

[0620] Meanwhile, Examples 3-4 to 3-6 and Comparative Examples 3-8 to 3-13 include a lithium nickel cobalt manganese oxide-based positive electrode active material having an average particle diameter of 5 ㎛ or more.

[0621] Examples 3-4 to 3-6 include a conductive material having an average particle diameter of 5 ㎛ or more in the primer layer and a different conductive material having an average particle diameter different from that of the conductive material, and the relationship between the average particle diameter of the conductive material included in the primer layer and the average particle diameter of the positive electrode active material included in the positive electrode active material layer satisfies Equations 2 and 3, thereby improving the interfacial adhesive strength between the current collector and the active material layer compared to Comparative Examples 3-9 to 3-12, thereby improving the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery.

[0622] In addition, in Comparative Example 3-8, in which no primer layer was formed, the interfacial adhesive strength between the current collector and the active material layer was significantly reduced compared to Examples 3-4 to 3-6, and in Comparative Example 3-13, in which the binder content was increased to improve the adhesive strength, the interfacial adhesive strength between the current collector and the active material layer was improved, but it was confirmed that the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery were deteriorated compared to Examples 3-4 to 3-6 due to the increase in the binder content.

[0623]

[0624] The embodiment can be applied to a primer composition, an electrode including the same, and a secondary battery.

Claims

1. The first challenge; and Includes the second challenge, The first conductive material includes a first carbon-based material having an average particle diameter of 0.01 ㎛ or more and less than 0.1 ㎛, The second conductive material includes a second carbon-based material having an average particle diameter of more than 0.2 ㎛ and less than or equal to 20 ㎛, A primer composition in which the solid weight ratio of the first conductive agent to the solid weight ratio of the second conductive agent is 1:1 to 1:

3.

2. In paragraph 1, A primer composition wherein the first carbon-based material and the second carbon-based material are point-shaped carbon-based materials.

3. In paragraph 1, A primer composition wherein the first carbon-based material has an oil absorption number of 100 ml / 100g to 300 ml / 100g.

4. In paragraph 1, A primer composition wherein the solid content weight of the first conductive agent is 3 wt% to 10 wt% relative to the total weight of the primer composition.

5. In paragraph 1, A primer composition wherein the solid content weight of the second conductive agent is 3 wt% to 20 wt% relative to the total weight of the primer composition.

6. In paragraph 1, A primer composition wherein the first carbon-based material comprises acetylene black.

7. In paragraph 1, A primer composition wherein the second carbon-based material comprises graphite.

8. In paragraph 1, The above primer composition is prepared at room temperature and a shear rate of 10 s -1 A primer composition having a viscosity of 100 cPs to 1,000 cPs.

9. In paragraph 1, The above primer composition comprises a dispersant, A primer composition wherein the dispersant comprises a polyvinyl compound.

10. In paragraph 9, A primer composition further comprising a third conductive agent having an average particle diameter of 0.1 ㎛ or more and 0.3 ㎛ or less or a fourth conductive agent having an average particle diameter of 8 ㎛ or more and 35 ㎛ or less.

11. In paragraph 10, A primer composition wherein the sum of the solid content weights of the first and third conductive agents is 3 wt% to 10 wt% relative to the total weight of the primer composition.

12. In paragraph 10, A primer composition wherein the sum of the solid content weights of the first and fourth conductive agents is 5 to 20 wt% relative to the total weight of the primer composition.

13. In paragraph 9, A primer composition wherein the solid content weight of the dispersant is 1 wt% to 5 wt% based on the total weight of the primer composition.

14. In paragraph 9, A primer composition wherein the polyvinyl compound comprises polyvinylpyrrolidone having a weight average molecular weight of 37,000 g / mol to 50,000 g / mol.

15. Whole house; A primer layer formed on at least one surface of the above-mentioned collector; and It includes a positive electrode active material layer formed on the primer layer, The above primer layer comprises a primer composition according to claim 1, The above primer layer includes a fifth conductive material having an average particle diameter of less than 5 ㎛, The above positive electrode active material layer includes a first positive electrode active material having an average particle diameter of less than 5 ㎛, Anode satisfying the following equation 1: [Formula 1] 5% < (X1 / A1) × 100 < 35% The above A1 is the average particle diameter (㎛) of the first positive electrode active material, and the above X1 is the average particle diameter (㎛) of the fifth conductive material.

16. In paragraph 15, The above A1 is an anode having a diameter of 0.6 ㎛ or more and 1.8 ㎛ or less.

17. In paragraph 15, A positive electrode, wherein the first positive electrode active material comprises lithium iron oxide.

18. In paragraph 15, The fifth challenge material is an anode containing carbon black.

19. In paragraph 15, An anode in which the solid content weight of the fifth conductive material is 3 wt% to 15 wt% relative to the total weight of the primer layer.

20. In paragraph 15, The anode is one having an adhesive strength of 15 gf / 20mm or more and 30 gf / 20mm or less according to the following measurement method: [measurement method] 1) The above anode is punched to 20 mm × 120 mm to manufacture a specimen. 2) After attaching double-sided tape to the slide glass, attach the above specimen and press it after rolling it back and forth 10 times using a 2 kg roller. 3) Using a universal testing machine, the adhesive strength at which the specimen is peeled off from the slide glass is measured after pulling at a speed of 300 mm / min. At this time, the measurement section is 50 mm, and the measurement angle between the slide glass and the specimen is 90°.