Method for producing negative electrode composition for secondary battery

Abstract

A method for producing a negative electrode active material for a secondary battery according to exemplary embodiments of the present invention comprises the steps of: introducing a negative electrode active material powder and a first binder powder into a mixer; introducing a first solvent into the mixer and performing first mixing to form a preliminary negative electrode composition; and after the formation of the preliminary negative electrode composition, introducing a second binder powder into the mixer and performing second mixing to form a negative electrode composition.

Description

Method for producing a negative electrode composition for a secondary battery

[0001] The disclosure of the present application relates to a method for producing a negative electrode composition for a secondary battery, a negative electrode for a secondary battery produced using the same, and a secondary battery including the same.

[0002] Secondary batteries, which can be repeatedly charged and discharged, are widely used as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptops, thanks to the advancements in the information and communication and display industries. Furthermore, battery packs containing secondary batteries are being developed and applied as power sources for eco-friendly vehicles such as electric vehicles.

[0003] Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, and nickel-hydrogen batteries. Among these, lithium secondary batteries are being actively developed and applied due to their high operating voltage and energy density per unit weight, and their advantages in charging speed and weight reduction.

[0004] Recently, as the scope of secondary battery applications expands, development of manufacturing methods for secondary battery anodes with higher reliability and process stability is underway. For example, the resistance, adhesive strength, and lifespan characteristics of the anode and secondary battery can deteriorate depending on factors such as the order of raw material input and the type of raw material used during the anode manufacturing process.

[0005] According to one aspect of the present disclosure, a method for producing a negative electrode composition for a secondary battery having improved dispersibility, stability, and adhesiveness and reduced resistance can be provided.

[0006] According to one aspect of the present disclosure, a negative electrode for a secondary battery having improved stability and lifespan characteristics and reduced resistance can be provided.

[0007] According to one aspect of the present disclosure, a secondary battery having improved stability and lifespan characteristics and reduced resistance can be provided.

[0008] A method for manufacturing a negative electrode composition for a secondary battery according to embodiments of the present disclosure includes introducing negative electrode active material powder and a first binder powder into a mixer, introducing a first solvent, performing a first mixing to form a preliminary negative electrode composition, and then introducing a second binder powder into the mixer and performing a second mixing to form a negative electrode composition.

[0009] In some embodiments, the negative active material powder and the first binder powder may be introduced into the operating mixer to form a powder mixture, and then the first solvent may be introduced.

[0010] In some embodiments, the step of forming the preliminary cathode composition and the step of forming the cathode composition may further include a step of introducing a second solvent into the mixer.

[0011] In some embodiments, the second binder powder may be fed into the mixer in two or more divided portions.

[0012] In some embodiments, the total content of the first solid component in the preliminary cathode composition may be 65 wt% to 75 wt%.

[0013] In some embodiments, the total content of the second solid content, which is a solid content in the preliminary cathode composition into which the second solvent is added, may be 3 wt% to 9 wt% less than the total content of the first solid content.

[0014] In some embodiments, the first binder powder and the second binder powder may each independently comprise a compound comprising a repeating unit represented by the following chemical formula 1:

[0015] [Chemical Formula 1]

[0016]

[0017] In the above chemical formula 1, M1 and M2 are each independently Na or Li, at least one of R1 to R4 is a group represented by the following chemical formula 2, the others are each independently H or a group represented by the following chemical formula 2, and n is an integer.

[0018] [Chemical Formula 2]

[0019]

[0020] In the above chemical formula 2, R5 is -CH0, -CH2CHO, -COCH3, or -CH2COCH3, and *- indicates a bonding position bonded to oxygen.

[0021] In some embodiments, the first binder powder and the second binder powder may each independently contain, or may not contain, a compound including a repeating unit represented by the following chemical formula 3 in an amount of 20 wt% or less, based on the total content of each binder powder:

[0022] [Chemical Formula 3]

[0023]

[0024] In the above chemical formula 3, M4 and M5 are each independently Na or Li, and n is an integer.

[0025] In some embodiments, the negative active material may include at least one selected from the group consisting of artificial graphite and natural graphite.

[0026] In some embodiments, the first solvent and the second solvent may each independently include at least one selected from the group consisting of water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, and t-butanol.

[0027] In some embodiments, in the step of forming the negative electrode composition, at least one of a third solvent and a third binder may be further added to the mixer after the second mixing, and the negative electrode composition may be formed by a third mixing.

[0028] In some embodiments, the third solvent may be introduced into the mixer, and then the third binder may be introduced and mixed to form the negative electrode composition.

[0029] In some embodiments, the first viscosity, which is the viscosity of the first binder powder, may be 200 cP to 6500 cP.

[0030] In some embodiments, the second viscosity, which is the viscosity of the second binder powder, may be 1500 cP to 9500 cP.

[0031] In some embodiments, the first viscosity may be between 500 cP and 3500 cP.

[0032] In some embodiments, the second viscosity may be 3000 cP to 7000 cP.

[0033] In some embodiments, the ratio of the second viscosity to the first viscosity may be 1 to 10.

[0034] In some embodiments, the ratio of the second viscosity to the first viscosity may be 1 to 6.

[0035] A negative electrode for a secondary battery according to embodiments of the present disclosure comprises: a negative electrode current collector; and a negative electrode active material layer formed from a negative electrode composition manufactured by the above-described manufacturing method, the negative electrode current collector being disposed on at least one surface thereof.

[0036] A secondary battery according to embodiments of the present disclosure includes the above-described negative electrode for a secondary battery; and a positive electrode opposite the negative electrode.

[0037] According to one embodiment of the present disclosure, a negative electrode composition for a secondary battery having improved dispersibility, stability, and adhesiveness and reduced resistance can be manufactured.

[0038] According to one embodiment of the present disclosure, the life characteristics and output characteristics of a negative electrode for a secondary battery manufactured using the negative electrode composition can be improved.

[0039] According to one embodiment of the present disclosure, the life characteristics and output characteristics of a secondary battery including the negative electrode can be improved.

[0040] The method for manufacturing the negative electrode composition for a secondary battery of the present disclosure, the negative electrode, and the secondary battery can be widely applied in green technology fields such as electric vehicles, battery charging stations, and other fields utilizing batteries, such as solar power generation and wind power generation. The method for manufacturing the negative electrode composition for a secondary battery of the present disclosure, the negative electrode, and the secondary battery can be used in eco-friendly electric vehicles, hybrid vehicles, etc., which suppress air pollution and greenhouse gas emissions and thus prevent climate change.

[0041] FIG. 1 is a schematic flowchart illustrating a method for manufacturing a negative electrode composition for a secondary battery according to exemplary embodiments.

[0042] FIG. 2 is a schematic flowchart illustrating a method for manufacturing a negative electrode composition for a secondary battery according to other exemplary embodiments.

[0043] Figures 3 and 4 are schematic plan views and cross-sectional views, respectively, showing secondary batteries according to exemplary embodiments.

[0044] Figure 5 is an internal image of a stirrer that was photographed while manufacturing a cathode composition according to Comparative Example 1.

[0045] Embodiments of the present disclosure provide a method for manufacturing an anode composition for a secondary battery (hereinafter, abbreviated as "anode composition"). An anode composition manufactured using the method for manufacturing the anode composition is provided. A secondary battery manufactured using the anode composition is also provided.

[0046] Hereinafter, embodiments of the present disclosure will be described in detail. However, these are merely exemplary and the present disclosure is not limited to the specific embodiments described as examples.

[0047]

[0048] <Method for producing a cathode composition>

[0049] FIG. 1 is a schematic flowchart illustrating a method for manufacturing a negative electrode composition for a secondary battery according to exemplary embodiments.

[0050] Referring to FIG. 1, a negative electrode active material powder and a first binder powder are introduced into a mixer (e.g., step S10), a first solvent is introduced into the mixer, and a first mixing is performed (e.g., step S20) to form a preliminary negative electrode composition.

[0051] For example, the above mixer may utilize an automatic mixer driven by current.

[0052] The above mixer can be driven at the above constant speed through changes in the maximum driving current until the cathode slurry production is completed.

[0053] For example, the first binder powder can be introduced in a solid state.

[0054] In exemplary embodiments, the first binder powder and the first solvent are not introduced into the mixer in the form of a binder solution in which they are mixed in advance.

[0055] In some embodiments, the first solvent may begin to be added before the addition of the negative active material powder and the first binder powder is completed. For example, the first solvent may begin to be added together with the first binder powder when the addition of the first binder powder is 3 / 4 complete, but is not limited thereto.

[0056] In some embodiments, the negative active material powder and the first binder powder may be introduced into the operating mixer to form a powder mixture, and then the first solvent may be introduced. For example, the mixer may be set and operated at a constant speed (e.g., maximum speed), and the negative active material powder and the first binder powder may be introduced into the operating mixer. Thereafter, the first solvent may be introduced into the operating mixer to perform the first mixing.

[0057] Accordingly, the phenomenon of solvent shock, in which swelling occurs on the surface of the aggregated first binder powder and the first solvent cannot penetrate, can be further suppressed. As a result, the dispersibility of the negative active material and the first binder, as well as the lifespan characteristics of the secondary battery, can be further improved, and internal resistance can be reduced.

[0058] For example, the introduction of the first solvent may be performed 1 to 20 seconds after the introduction of the negative active material powder and the first binder powder is completed. Within this range, the solvent impact phenomenon described above can be sufficiently improved.

[0059] In some embodiments, the total content of the first solid component in the preliminary cathode composition may be 65 wt% to 75 wt%.

[0060] For example, the first mixing may be performed at 20°C to 60°C.

[0061] In one embodiment, the first mixing may be performed by a kneading process. For example, the preliminary cathode composition may be formed in a kneading form.

[0062] The above-described negative active material powder (hereinafter abbreviated as "negative active material") may include a material capable of adsorbing and desorbing lithium ions. For example, the negative active material may be a carbon-based material such as crystalline carbon, amorphous carbon, carbon composite, or carbon fiber; lithium metal; lithium alloy; silicon (Si)-containing material, or tin (Sn)-containing material. These may be used alone or in combination of two or more.

[0063] The above amorphous carbon may include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), etc.

[0064] The above crystalline carbon may include graphitic carbon such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc.

[0065] The lithium metal may include pure lithium metal and / or lithium metal having a protective layer formed thereon for suppressing dendrite growth, etc. In one embodiment, a lithium metal-containing layer deposited or coated on an anode current collector may be used as the anode active material layer. In one embodiment, a lithium thin film layer may be used as the anode active material layer.

[0066] Elements included in the above lithium alloy include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, indium, etc. These may be used alone or in combination of two or more.

[0067] The above silicon-containing material can provide increased capacity characteristics. The above silicon-containing material is Si, SiO x (0 <x<2), 금속 도핑된 SiO x (0 <x<2), 실리콘-탄소 복합체 등을 포함할 수 있다.

[0068] The above metal may include lithium and / or magnesium, and the metal-doped SiO x (0 <x<2)는 금속 실리케이트를 포함할 수 있다.

[0069] In some embodiments, the negative electrode active material may include, for example, 5 wt% to 15 wt% of silicon-based active material particles, based on the total weight of the negative electrode active material, and may include, for example, 9 wt% to 13 wt%.

[0070] In exemplary embodiments, the negative active material may include at least one selected from the group consisting of artificial graphite and natural graphite. Accordingly, output characteristics may be improved and costs may be reduced.

[0071] In exemplary embodiments, the first binder powder may comprise carboxymethylcellulose and / or a salt thereof comprising a hemiacetal functional group derived from a hemiacetal reaction of at least one of the free hydroxyl groups with an aldehyde compound.

[0072] The above first binder powder may include a product formed by a reaction of at least one free hydroxyl group (-OH) of carboxymethyl cellulose (CMC) and / or a salt thereof with an aldehyde compound to form an acyclic hemiacetal (hereinafter, abbreviated as a hemiacetal reaction). The metal included in the salt may be an alkali metal, and may be, for example, lithium, sodium, calcium, or the like.

[0073] Specifically, the above-mentioned free hydroxyl group and the -CHO group of the above-mentioned aldehyde compound react to form a direct bond between one hydroxyl group and one ether bond (-O-) on the same carbon.

[0074] A group containing carbon in which one hydroxyl group and one ether bond (-O-) are formed by the above hemiacetal reaction can be defined as an acyclic hemiacetal functional group (hereinafter, may be abbreviated as hemiacetal functional group). That is, the product may be carboxymethylcellulose and / or a salt thereof in a form in which the hydroxyl group participating in the above hemiacetal reaction is replaced by the above hemiacetal functional group.

[0075] For example, the carboxymethyl cellulose and / or salt thereof containing the hemiacetal functional group can be prepared by mixing and heating CMC and / or salt thereof etherified only with methyl carboxylic acid and / or salt thereof and an aldehyde compound. The aldehyde compound may include a monoaldehyde compound and / or a dialdehyde compound. The aldehyde compound may include, for example, glyoxal, methyl glyoxal, etc.

[0076] Carboxymethylcellulose or a salt thereof containing the above hemiacetal functional group can be represented, for example, by the following chemical formula A.

[0077] [Chemical Formula A]

[0078]

[0079] In the above chemical formula A, the CMC represents a repeating unit constituting the main chain of carboxymethyl cellulose or a salt thereof, and the functional group bonded to the CMC represents a hemiacetal functional group. The R may be, for example, an alkyl group, or an alkyl group including an aldehyde group or a ketone group at the terminal, etc.

[0080] Compared to a composition using only CMC and / or a salt thereof in which the hydroxyl group is not substituted by the hemiacetal functional group described above, the negative electrode composition according to the embodiments of the present disclosure can more effectively improve the dispersibility of negative electrode active materials in the negative electrode composition by including a compound including the hemiacetal functional group due to the repulsive force between ether bonds. Accordingly, the life characteristics and low resistance characteristics of a secondary battery including a negative electrode to which the negative electrode composition manufactured by the above manufacturing method is applied can be improved.

[0081] In some embodiments, the first binder powder may include a compound comprising a repeating unit represented by the following chemical formula 1.

[0082] [Chemical Formula 1]

[0083]

[0084] In the above chemical formula 1, M1 and M2 are each independently Na or Li, at least one of R1 to R4 is a group represented by the following chemical formula 2, the others are each independently H or a group represented by the following chemical formula 2, and n is an integer.

[0085] [Chemical Formula 2]

[0086]

[0087] In the above chemical formula 2, R5 is -CH0, -CH2CHO, -COCH3, or -CH2COCH3, and *- indicates a bonding position bonded to oxygen.

[0088] In some embodiments, R5 in the above formula 2 may be -CH0 or -COCH3.

[0089] In some embodiments, the hemiacetal functional group may be, for example, a group represented by the following chemical formula A-1 or A-2.

[0090]

[0091] In the above chemical formula A-1 or A-2, *- indicates a bonding position where the hemiacetal functional group is bonded to the main chain of carboxymethylcellulose or its salt, and is the same as the position where the free hydroxyl group was bonded before the hemiacetal reaction proceeded.

[0092] Accordingly, the first binder powder may include at least one compound selected from the group consisting of compounds in which any one, two, three or four of R1 to R4 are a group represented by the chemical formula 2.

[0093] The above M1 and the above M2 may be identical to each other.

[0094] In the above chemical formula 1, -OCH2COOM1 and -OCH2COOM2, M1 and M2 can each exist in the form of carboxylic acid salts by ionic bonding, and -OCH2COO - M1 + and -OCH2COO - M2 + can exist in the form of

[0095] The above n may be, for example, 300 to 15000 or 500 to 10000.

[0096] In some embodiments, one or two of R1 to R4 may be a group represented by the above formula 2, and the remainder may be H.

[0097] In some embodiments, at least one of R2 and R4 may be a group represented by the above formula 2, and the other may be H.

[0098] In some embodiments, the first binder powder may include a compound in which among R1 to R4 in the chemical formula 1, R2 is a group represented by the chemical formula 2, and the remainder is H. The first binder powder may be, for example, a compound in which among R1 to R4, R2 is a group represented by the chemical formula 2, and the remainder is H.

[0099] In some embodiments, the first binder powder may include a compound in which R2 among R1 to R4 is a group represented by the above chemical formula 2 and the rest are H; and a compound in which R4 among R1 to R4 is a group represented by the above chemical formula 2 and the rest are H.

[0100] The compound including the repeating unit represented by the above chemical formula 1 may be, for example, a compound represented by the following chemical formula 1-1, but is not limited thereto.

[0101] [Chemical Formula 1-1]

[0102]

[0103] In the above chemical formula 1-1, M1, M 2, R1 to R4 and n refer to the contents described above in chemical formula 1. R E1 and R E2 are each independently H or CH2COOM3, M3 is Na or Li, and n is an integer. For example, R E1 is hydrogen and R E2 It can be CH2COOM3.

[0104] As a non-limiting example, M1 to M3 may be identical to each other.

[0105] In some embodiments, the first binder powder and the second binder powder may each independently include at least one of carboxymethylcellulose and a salt thereof, wherein the degree of substitution (DS) of a hydroxyl group by methylcarboxylic acid or a salt thereof is 0.6 or less and the weight average molecular weight is 3,000,000 g / mol or more. The term “degree of substitution” as used herein may represent the average number of substituted carboxymethyl groups per molecule of anhydrous glucose.

[0106] Even when carboxymethyl cellulose and / or its salt having the above-described substitution range and weight average molecular weight range is used as a binder, the dispersibility of the first and second binder powders can be improved and both the life characteristics and low resistance characteristics of the secondary battery can be improved by the above-described method for producing the negative electrode composition.

[0107] In some embodiments, the degree of substitution may be 0.4 to 0.6, and the weight average molecular weight may be 3,000,000 g / mol to 5,000,000 g / mol. Accordingly, excessive increase in the viscosity of the negative electrode slurry may be further suppressed, and the life characteristics and low resistance characteristics of the secondary battery may be further improved.

[0108] In some embodiments, the first solvent may include at least one selected from the group consisting of water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, and t-butanol.

[0109] FIG. 2 is a schematic flowchart illustrating a method for manufacturing a negative electrode composition for a secondary battery according to other exemplary embodiments.

[0110] In some embodiments, a step of introducing a second solvent into the mixer may be further included between the step of forming the preliminary negative electrode composition and the step of forming the negative electrode composition (e.g., step S30). Accordingly, the solid content of the preliminary negative electrode composition can be appropriately reduced, thereby preventing the solvent impact phenomenon described above and suppressing the formation of solid lumps within the mixer. Accordingly, the life characteristics and low resistance characteristics of the secondary battery can be improved.

[0111] In some embodiments, the second solvent may comprise the same type of solvent as the first solvent.

[0112] In some embodiments, the total content of the second solid content, which is a solid content in the preliminary negative electrode composition into which the second solvent is added, may be 3 wt% to 9 wt% less than the total content of the first solid content. In this way, the total content of the solid content of the preliminary negative electrode composition may decrease depending on the addition of the second solvent.

[0113] For example, the total content of the second solid component may be reduced by 3% to 9% or 3% to 5% compared to the total content of the first solid component. Within this range, the formation of binder aggregates in the second mixing described below may be further suppressed, and the lifespan characteristics of the secondary battery may be further improved.

[0114] For example, the total content of the second solid may be 56 wt% to 72 wt%.

[0115] In exemplary embodiments, after forming the preliminary negative electrode composition, a second binder powder may be added to the mixer and a second mixing may be performed to form the negative electrode composition (e.g., step S40). In one embodiment, the second mixing may be performed through a kneading process.

[0116] In some embodiments, the second binder may be fed into the mixer in two or more divided portions. For example, the second binder may be fed in two to ten divided portions, or two to seven divided portions, or two to five divided portions. Accordingly, the dispersibility and adsorption properties of the second binder powder included in the negative electrode composition may be further improved. A secondary battery including a negative electrode formed from the negative electrode composition may achieve improved output characteristics and lifespan characteristics.

[0117] For example, the second binder powder may be introduced in a solid state.

[0118] In some embodiments, the first binder powder and the second binder powder may each independently comprise a compound including a repeating unit represented by Chemical Formula 1. The first binder powder and the second binder powder may be the same or different from each other.

[0119] In some embodiments, the first binder powder and the second binder powder may comprise the same compound.

[0120] In some embodiments, the first binder powder and the second binder powder may each independently contain, or may not contain, 20 wt% or less of a compound including a repeating unit represented by the following Chemical Formula 3, based on the total content of each binder powder. For example, the first binder powder may contain, or may not contain, 20 wt% or less of a compound including a repeating unit represented by the following Chemical Formula 3, based on the total content of each binder powder, and the second binder powder may contain, or may not contain, 20 wt% or less of a compound including a repeating unit represented by the following Chemical Formula 3, based on the total content of each binder powder.

[0121] [Chemical Formula 3]

[0122]

[0123] In the above chemical formula 3, M4 and M5 are Na or Li, and n is an integer. The n may be, for example, 300 to 15000 or 500 to 10000.

[0124] The compound including the repeating unit represented by the above chemical formula 3 may be, for example, a compound represented by the following chemical formula 3-1, but is not limited thereto.

[0125] [Chemical Formula 3-1]

[0126]

[0127] In the above chemical formula 3-1, M4 and M5 are each independently Na or Li, and R E3 and R E4 One of them is H and the other is CH2COOM6, M6 is Na or Li, and n is an integer. The n can be, for example, 300 to 15000 or 500 to 10000. For example, R E3 is H and R E4 It can be CH2COOM6.

[0128] As a non-limiting example, M4 to M6 may be identical to each other.

[0129] In one embodiment, the first and second binder powders may contain 80 to 100 wt% of a compound including a repeating unit represented by the chemical formula 1 based on the total content of each binder powder.

[0130] For example, the second mixing can be performed at 20°C to 60°C.

[0131] In some embodiments, the first viscosity, which is the viscosity of the first binder powder measured in an aqueous solution having a concentration of 1.2 wt%, may be from 200 cP to 6500 cP. The first viscosity may be, for example, from 300 cP to 6000 cP, from 400 cP to 4000 cP, or from 500 cP to 3000 cP.

[0132] In some embodiments, the second viscosity, which is the viscosity of the second binder powder measured in an aqueous solution having a concentration of 1.2 wt%, may be from 1500 cP to 9500 cP. The second viscosity may be, for example, from 2000 cP to 9000 cP, from 3000 cP to 6000 cP, or from 3000 cP to 5000 cP.

[0133] The first and second viscosities of the first and second binder powders refer to viscosities measured in an aqueous solution state at a concentration of 1.2 wt%. The first and second viscosities can be measured, for example, at room temperature. In this case, the aqueous solution at a concentration of 1.2 wt% can be formed by dissolving the first binder powder or the second binder powder in water at a concentration of 1 wt%, respectively.

[0134] In some embodiments, the ratio of the second viscosity to the first viscosity may be 1 to 10. For example, the ratio of the second viscosity to the first viscosity may be 1 to 8, 1 to 6, or 1 to 3. Accordingly, the first binder and the second binder included in the negative electrode composition may be more uniformly dispersed.

[0135] In some embodiments, in the step of forming the negative electrode composition, after the second mixing, at least one of a third solvent and a third binder may be added to the mixer and the negative electrode composition may be formed by the third mixing.

[0136] The third solvent refers to the description above regarding the first solvent or the second solvent. The third solvent may include the same type of solvent as the first solvent.

[0137] In some embodiments, the third solvent and the third binder may not be introduced into the mixer together.

[0138] In some embodiments, the third solvent may be added to the mixer, and then the third binder may be added to perform the third mixing.

[0139] For example, the third solvent may be added to the mixer while it is running after the second mixing to dilute it. After adding the third solvent, mixing may be performed for 10 to 60 minutes, but is not limited thereto.

[0140] The third binder may include a styrene-butadiene rubber (SBR) binder, a styrene-acrylate binder, a polyacrylic acid binder, a poly(3,4-ethylenedioxythiophene, PEDOT) binder, etc. These may be used alone or in combination of two or more.

[0141] The input form of the above third binder can be input in solid or liquid form and is not particularly limited.

[0142] As a non-limiting example, additional components such as a conductive agent, a thickener, a dispersant, etc. that can be further added to the cathode composition may be added to the mixer at any time before or after the first mixing or before or after the second mixing.

[0143] By adjusting the amount of the above-described components, the solid content or viscosity of the cathode composition can be controlled according to the technical purpose.

[0144] The solid content of the above cathode composition may be, for example, 40 wt% to 65 wt%, 45 wt% to 63 wt%, 50 wt% to 61 wt%, 52 wt% to 60 wt%, 53 wt% to 60 wt%, or 56 wt% to 60 wt%.

[0145] For example, based on the total content of the solid content included in the negative electrode composition, the total amount of the negative electrode active material can be appropriately adjusted within a range of 80 wt% to 98.9 wt%, the total amount of the binder can be appropriately adjusted within a range of 1.0 wt% to 10 wt%, for example, 1.1 wt% to 10 wt%, and the total amount of other components such as the conductive material can be appropriately adjusted within a range of 0.1 wt% to 10 wt%.

[0146] The viscosity of the above cathode composition at 23°C may be, for example, 6000 cP to 15000 cP, 7000 cP to 13000 cP, 8000 cP to 11000 cP, 8500 cP to 10000 cP, or 9000 cP to 9500 cP.

[0147] In some embodiments, the total content of the first binder and the second binder may be 1.5 wt% to 5 wt%. For example, the total content of the first and second binders may be 2 wt% to 5 wt%, or 3 wt% to 5 wt%. According to the manufacturing method according to the embodiments of the present disclosure, the amount of binder powder added can be increased without agglomeration of the negative electrode active material and / or binder powders, and thus the life characteristics and electrode adhesiveness of the negative electrode and secondary battery can be further improved. In addition, even when the negative active material includes a silicon-based active material, the change in cell thickness and swelling phenomenon that occur due to repeated charging and discharging of the secondary battery can be further suppressed. In some embodiments, the content of the first binder powder among the total weight of the first binder powder and the second binder powder is 30 wt% to 90 wt%, and may be, for example, 60 wt% to 90 wt% or 70 wt% to 80 wt%.

[0148] Based on the total weight of the first and second binder powders, the content of the second binder powder is 10 wt% to 70 wt%, for example, 10 wt% to 40 wt% or 20 wt% to 30 wt%.

[0149] Accordingly, the resistance of the secondary battery can be further reduced and its life characteristics can be further improved.

[0150] In exemplary embodiments, the maximum driving current of the mixer in the first mixing may be greater than the maximum driving current of the mixer in the second mixing. Accordingly, the maximum performance of the mixer can be achieved while the operating stability of the mixer and the dispersibility of the negative electrode composition can be further improved.

[0151] The maximum driving current of the above mixer may refer to the maximum value of the driving current of the mixer that changes depending on the input material while the driving speed of the mixer is maintained at a constant speed (e.g., maximum driving speed).

[0152] For example, a mixer manufactured by Primix may be used as the above mixer. As a non-limiting example, the mixer may be a 2000L class PD mixer, Planetary Despa & Mixer, etc.

[0153] In one embodiment, the driving speed of the mixer may be constant, for example, in the first mixing and the second mixing.

[0154] For example, the maximum driving current of the mixer can be changed by controlling the input amounts and input ratios of the first binder powder and the second binder powder, the input amounts and input time of the first solvent, the second solvent, and / or the third solvent, the viscosity and solid content of the mixture, etc.

[0155] In some embodiments, the difference (△C = C1-C2) between the maximum driving current (C1) of the mixer in the first mixing and the maximum driving current (C2) of the mixer in the second mixing may be, for example, 10 A to 130 A. △C may be, for example, 20 A to 100 A, 30 A to 80 A, or 40 A to 60 A. Accordingly, the dispersibility of the negative electrode composition may be further improved.

[0156] In some embodiments, for example, the maximum driving current of the mixer in the first mixing may be 180 A to 220 A.

[0157] In some embodiments, for example, the maximum driving current of the mixer in the second mixing may be 80 A to 160 A.

[0158]

[0159] <Cathode for secondary batteries and secondary batteries>

[0160] Figures 3 and 4 are schematic plan views and cross-sectional views, respectively, illustrating secondary batteries according to exemplary embodiments. For example, Figure 4 is a cross-sectional view taken along line I-I' of Figure 3 in the thickness direction.

[0161] The structures illustrated in FIGS. 3 and 4 are examples for convenience of explanation, and the structure of the secondary battery according to embodiments of the present disclosure is not limited thereto.

[0162] Referring to FIGS. 3 and 4, the secondary battery may include a negative electrode (130) manufactured using the above-described negative electrode composition and a positive electrode (100) opposite the negative electrode (130).

[0163] The cathode (130) can be formed using a cathode composition manufactured by the above-described manufacturing method.

[0164] For example, a method for manufacturing a negative electrode for a secondary battery including the above-described manufacturing method may be provided. The method for manufacturing a negative electrode for a secondary battery may include applying the above-described negative electrode composition to at least one surface of a negative electrode current collector (125), drying, and rolling.

[0165] The cathode (130) can be formed by applying the cathode composition to at least one surface of the cathode current collector (125), drying, and rolling.

[0166] The positive electrode (100) may include a positive electrode current collector (105) and a positive electrode active material layer (110) formed on at least one surface of the positive electrode current collector (105).

[0167] The positive electrode current collector (105) may include stainless steel, nickel, aluminum, titanium, or an alloy thereof. The positive electrode current collector (105) may also include aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. For example, the thickness of the positive electrode current collector (105) may be 10 μm to 50 μm.

[0168] The positive electrode active material layer (110) may include a positive electrode active material. The positive electrode active material may include a compound capable of reversibly intercalating and deintercalating lithium ions.

[0169] According to exemplary embodiments, the positive electrode active material may include a lithium-nickel metal oxide. The lithium-nickel metal oxide may further include at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0170] In some embodiments, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or crystal structure represented by the following chemical formula 4.

[0171] [Chemical Formula 4]

[0172] Li x Ni a M b O 2+z

[0173] In chemical formula 4, 0.9≤x≤1.2, 0.5≤a≤0.99, 0.01≤b≤0.5, -0.5≤z≤0.1 may be satisfied. As described above, M may include Co, Mn, and / or Al.

[0174] The chemical structure represented by Chemical Formula 4 represents the bonding relationship included in the layered structure or crystal structure of the positive electrode active material and does not exclude other additional elements. For example, M includes Co and / or Mn, and Co and / or Mn can serve as the main active element of the positive electrode active material together with Ni. Chemical Formula 4 is provided to express the bonding relationship of the above main active elements and should be understood as a formula encompassing the introduction and substitution of additional elements.

[0175] In one embodiment, auxiliary elements may be further included in addition to the main active element to enhance the chemical stability of the positive electrode active material or the layered structure / crystal structure. The auxiliary elements may be incorporated into the layered structure / crystal structure to form bonds, and in this case, it should be understood that they are also included within the chemical structure range represented by Chemical Formula 4.

[0176] The auxiliary element may include at least one selected from the group consisting of, for example, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, and Zr. The auxiliary element may also function as an auxiliary active element that contributes to the capacity / output activity of the positive electrode active material together with Co or Mn, for example, Al.

[0177] For example, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or crystal structure represented by the following chemical formula 4-1.

[0178] [Chemical Formula 4-1]

[0179] Li x Ni a M1 b1 M2 b2 O 2+z

[0180] In Chemical Formula 4-1, M1 may include Co, Mn, and / or Al. M2 may include the auxiliary elements described above. In Chemical Formula 4-1, 0.9≤x≤1.2, 0.5≤a≤0.99, 0.01≤b1+b2≤0.5, -0.5≤z≤0.1 may be satisfied.

[0181] The above-described positive electrode active material may further include a coating element or doping element. For example, elements substantially identical to or similar to the above-described auxiliary elements may be used as the coating element or doping element. For example, the above-described elements may be used singly or in combination of two or more.

[0182] The above coating element or doping element may be present on the surface of the lithium-nickel metal oxide particle, or may penetrate through the surface of the lithium-nickel metal composite oxide particle and be included in the bonding structure represented by the above chemical formula 4 or chemical formula 4-1.

[0183] The above positive electrode active material may include a nickel-cobalt-manganese (NCM) lithium oxide. In this case, an NCM lithium oxide with an increased nickel content may be used.

[0184] Ni can be provided as a transition metal associated with the output and capacity of a lithium secondary battery. Therefore, by employing a high-content (High-Ni) composition as described above in the positive electrode active material, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0185] However, as the Ni content increases, the long-term storage stability and lifespan stability of the cathode or secondary battery may relatively deteriorate, and side reactions with the electrolyte may also increase. However, according to exemplary embodiments, the inclusion of Co can maintain electrical conductivity, while improving lifespan stability and capacity retention characteristics through Mn.

[0186] The content of Ni (e.g., the mole fraction of nickel among the total moles of nickel, cobalt, and manganese) in the NCM-based lithium oxide may be 0.5 or more, 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the content of Ni may be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0187] In some embodiments, the positive electrode active material may include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate (LFP)-based active material (e.g., LiFePO4).

[0188] In some embodiments, the positive electrode active material may include, for example, an LLO (Li rich layered oxide) / OLO (Over Lithiated Oxide) active material, a Mn-rich active material, a Co-less active material, etc. having a chemical structure or crystal structure represented by Chemical Formula 5. These may be used alone or in combination of two or more.

[0189] [Chemical Formula 5]

[0190] p[Li2MnO3]·(1-p)[Li q JO2]

[0191] In chemical formula 5, 0 <p<1이고, 0.9≤q≤1.2이며, J는 Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg 및 B 중 적어도 하나의 원소를 포함할 수 있다.

[0192] The positive electrode active material can be mixed in a solvent to prepare a positive electrode slurry. The positive electrode slurry can be coated on at least one surface of a positive electrode current collector (105), and then dried and rolled to prepare a positive electrode active material layer (110). The coating can include methods such as gravure coating, slot die coating, multilayer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, and casting. The positive electrode active material layer (110) can further include a binder and optionally can further include a conductive material and / or a thickener.

[0193] As the above solvent, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. can be used.

[0194] The above binder may include polyvinylidenefluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylonitrile, polymethylmethacrylate, acrylonitrile butadiene rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), etc. These may be used alone or in combination of two or more.

[0195] In one embodiment, a PVDF-based binder may be used as the positive electrode binder. In this case, the amount of binder used to form the positive electrode active material layer (110) may be reduced, while the amount of positive electrode active material may be relatively increased. Accordingly, the output characteristics and capacity characteristics of the secondary battery may be improved.

[0196] The conductive material may be added to enhance the conductivity and / or mobility of lithium ions or electrons of the positive electrode active material layer (110). For example, the conductive material may include a carbon-based conductive material such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), carbon fiber, etc., and / or a metal-based conductive material including a perovskite material such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc. These may be used alone or in combination of two or more.

[0197] The positive electrode slurry may further include a thickener and / or a dispersant. In one embodiment, the positive electrode slurry may include a thickener such as carboxymethyl cellulose (CMC).

[0198] A cathode composition can be manufactured by a manufacturing method according to exemplary embodiments.

[0199] The negative electrode (130) may include a negative electrode current collector (125) and a negative electrode active material layer (120) formed using a negative electrode composition manufactured by a manufacturing method according to exemplary embodiments, and disposed on at least one surface of the negative electrode current collector (125). The negative electrode composition manufactured by the manufacturing method according to exemplary embodiments may have a negative electrode slurry form. The negative electrode active material layer (120) may be formed by applying and drying the above-described negative electrode composition on at least one surface of the negative electrode current collector (125), and may be formed, for example, by applying, drying, and rolling the above-described negative electrode composition.

[0200] For example, the negative electrode current collector (125) may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, etc. These may be used alone or in combination of two or more. For example, the thickness of the negative electrode current collector (125) may be 10 μm to 50 μm.

[0201] The negative electrode active material layer (120) may include the above-described negative electrode active material. For example, the negative electrode active material may include a plurality of negative electrode active material particles.

[0202] After the above-described negative electrode composition is coated / deposited on a negative electrode current collector (125), drying and rolling can be performed to manufacture a negative electrode active material layer (120). The coating can include methods such as gravure coating, slot die coating, multilayer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, and casting. The negative electrode active material layer (120) can optionally further include a conductive agent, a thickener, and the like.

[0203] The above-described materials that can be used in manufacturing the anode (100) as the above-described conductive agent and thickener can be used.

[0204] In exemplary embodiments, a separator (140) may be interposed between the anode (100) and the cathode (130). The separator (140) may be configured to prevent electrical short-circuiting between the anode (100) and the cathode (130) and to allow ion flow. For example, the thickness of the separator may be 10 μm to 20 μm.

[0205] For example, the separator (140) may include a porous polymer film or a porous nonwoven fabric.

[0206] The above porous polymer film may include a polyolefin polymer such as an ethylene polymer, a propylene polymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer. These may be used alone or in combination of two or more.

[0207] The above porous nonwoven fabric may include high-melting-point glass fibers, polyethylene terephthalate fibers, etc.

[0208] The separator (140) may include a ceramic material. For example, inorganic particles may be coated on the polymer film or dispersed within the polymer film to improve heat resistance.

[0209] The separator (140) may have a single-layer or multi-layer structure including the above-described polymer film and / or non-woven fabric.

[0210] According to exemplary embodiments, an electrode cell is defined by an anode (100), a cathode (130), and a separator (140), and a plurality of electrode cells may be stacked to form an electrode assembly (150) in the form of, for example, a jelly roll. For example, the electrode assembly (150) may be formed through winding, stacking, z-folding, stack-folding, etc. of the separator (140).

[0211] An electrode assembly (150) may be housed together with an electrolyte within a case (160) to define a lithium secondary battery. According to exemplary embodiments, a non-aqueous electrolyte may be used as the electrolyte.

[0212] The non-aqueous electrolyte contains a lithium salt as an electrolyte and an organic solvent, and the lithium salt is, for example, Li+ X - is expressed as and the anion of the lithium salt (X - ) as F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - Examples include:

[0213] Examples of the organic solvent include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate, diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, ethylpropyl carbonate, dipropyl carbonate, vinylene carbonate, methylacetate (MA), ethyl acetate (EA), n-propylacetate (n-PA), 1,1-dimethylethyl acetate (DMEA), methyl propionate (MP), ethyl propionate (EP), fluoroethyl acetate (FEA), difluoroethyl acetate (DFEA), trifluoroethyl acetate (TFEA), dibutyl ether, Tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (DEGDME), dimethoxyethane, tetrahydrofuran (THF), 2-methyltetrahydrofuran, ethyl alcohol, isopropyl alcohol, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, gamma-butyrolactone, and propylene sulfite can be used. These can be used alone or in combination of two or more.

[0214] The above non-aqueous electrolyte may further include additives. The additives may include, for example, cyclic carbonate compounds, fluorine-substituted carbonate compounds, sultone compounds, cyclic sulfate compounds, cyclic sulfite compounds, phosphate compounds, borate compounds, etc. These may be used alone or in combination of two or more.

[0215] The above cyclic carbonate compound may include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), etc.

[0216] The above fluorine-substituted cyclic carbonate compound may include fluoroethylene carbonate (FEC), etc.

[0217] The above sultone compounds may include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, etc.

[0218] The above cyclic sulfate compound may include 1,2-ethylene sulfate, 1,2-propylene sulfate, etc.

[0219] The above cyclic sulfite compound may include ethylene sulfite, butylene sulfite, etc.

[0220] The above phosphate compound may include lithium difluoro bis-oxalato phosphate, lithium difluoro phosphate, etc.

[0221] The above borate compound may include lithium bis(oxalate) borate, etc.

[0222] In some embodiments, a solid electrolyte may be used instead of the non-aqueous electrolyte described above. In this case, the lithium secondary battery may be manufactured in the form of an all-solid-state battery. Furthermore, a solid electrolyte layer may be placed between the positive electrode (100) and negative electrode (130) instead of the separator (140) described above.

[0223] The solid electrolyte may include a sulfide-based electrolyte. As a non-limiting example, the sulfide-based electrolyte may include Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-LiCl-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (m, n are positive numbers, Z is Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , (p, q are positive numbers, M is P, Si, Ge, B, Al, Ga, or In), Li7-xPS6-xCl x (0≤x≤2), Li7-xPS6-xBr x (0≤x≤2), Li7-xPS6-xI x (0≤x≤2) etc. These can be used alone or in combination of two or more.

[0224] In one embodiment, the solid electrolyte may include an oxide-based amorphous solid electrolyte, such as, for example, Li2O-B2O3-P2O5, Li2O-SiO2, Li2O-B2O3, Li2O-B2O3-ZnO, etc.

[0225] As illustrated in FIGS. 2 and 3, electrode tabs (positive electrode tabs and negative electrode tabs) may protrude from the positive electrode collector (105) and negative electrode collector (125) belonging to each electrode cell and extend to one side of the case (160). The electrode tabs may be fused together with the one side of the outer case (160) to form electrode leads (positive electrode leads (107) and negative electrode leads (127)) that extend or are exposed to the outside of the outer case (160).

[0226] The above lithium secondary battery can be manufactured in a cylindrical, square, pouch or coin shape using, for example, a can.

[0227]

[0228] The embodiments of the present disclosure described above include the following aspects and can be implemented through at least one of the following aspects.

[0229] A method for manufacturing a negative electrode composition for a secondary battery according to a first aspect of the present disclosure comprises: adding a negative electrode active material powder and a first binder powder to a mixer, adding a first solvent, and performing a first mixing to form a preliminary negative electrode composition; and after forming the preliminary negative electrode composition, adding a second binder powder to the mixer, and performing a second mixing to form a negative electrode composition.

[0230] In the first aspect, according to the second aspect, the negative active material powder and the first binder powder may be introduced into the operating mixer to form a powder mixture, and then the first solvent may be introduced.

[0231] In the first aspect or the second aspect, according to the third aspect, between the formation of the preliminary negative electrode composition and the formation of the negative electrode composition, a second solvent may be further introduced into the mixer.

[0232] In any one of the first to third aspects, according to the fourth aspect, the second binder powder can be divided and fed into the mixer two or more times.

[0233] In any one of the first to fourth aspects, according to the fifth aspect, the total content of the first solid content in the preliminary negative electrode composition may be 65 wt% to 75 wt%.

[0234] In the fifth aspect, according to the sixth aspect, the total content of the second solid content, which is a solid content in the preliminary cathode composition into which the second solvent is added, may be 3 wt% to 9 wt% less than the total content of the first solid content.

[0235] In any one of the first to sixth aspects, according to the seventh aspect, the first binder powder and the second binder powder may each independently include a compound including a repeating unit represented by the chemical formula 1.

[0236] In the seventh aspect, according to the eighth aspect, the first binder powder and the second binder powder may each independently contain, or may not contain, a compound including a repeating unit represented by the chemical formula 3 in an amount of 20 wt% or less based on the total content of each binder powder.

[0237] In any one of the first to eighth aspects, according to the ninth aspect, the negative active material may include at least one selected from the group consisting of artificial graphite and natural graphite.

[0238] In any one of the first to ninth aspects, according to the tenth aspect, the first solvent and the second solvent may each independently include at least one selected from the group consisting of water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, and t-butanol.

[0239] In any one of the first to tenth aspects, according to the eleventh aspect, in forming the negative electrode composition, after the second mixing, at least one of a third solvent and a third binder is further added to the mixer, and the negative electrode composition can be formed by performing a third mixing.

[0240] In the above eleventh aspect, according to the twelfth aspect, after the third solvent is introduced into the mixer, the third binder is introduced and the third mixing is performed to form the negative electrode composition.

[0241] In any one of the first to twelfth aspects, according to the thirteenth aspect, the first viscosity, which is the viscosity of the first binder powder, may be 200 cP to 6500 cP.

[0242] In any one of the first to thirteenth aspects, according to the fourteenth aspect, the second viscosity, which is the viscosity of the second binder powder, may be 1500 cP to 9500 cP.

[0243] In the 13th aspect or the 14th aspect, according to the 15th aspect, the first viscosity may be 500 cP to 3500 cP.

[0244] In any one of the 14th aspect to the 15th aspect, according to the 16th aspect, the second viscosity may be 3000 cP to 7000 cP.

[0245] In any one of the 14th to 16th aspects, according to the 17th aspect, the ratio of the second viscosity to the first viscosity may be 1 to 10.

[0246] In the 17th aspect, according to the 18th aspect, the ratio of the second viscosity to the first viscosity may be 1 to 6.

[0247] A negative electrode for a secondary battery according to the 19th aspect of the present disclosure comprises: a negative electrode current collector; and a negative electrode active material layer formed from a negative electrode composition manufactured by a method for manufacturing a negative electrode composition according to any one of the first to eighteenth aspects, and disposed on at least one surface of the negative electrode current collector.

[0248] A secondary battery according to the 20th aspect of the present disclosure comprises a negative electrode for a secondary battery according to the 19th aspect; and a positive electrode opposite to the negative electrode.

[0249]

[0250] Hereinafter, embodiments of the present disclosure will be further described with reference to specific experimental examples. The examples and comparative examples included in the experimental examples are merely illustrative of the present disclosure and do not limit the scope of the appended claims. It will be apparent to those skilled in the art that various changes and modifications to the examples are possible within the scope and technical idea of ​​the present disclosure, and it is also natural that such changes and modifications fall within the scope of the appended claims.

[0251]

[0252] Manufacturing example

[0253] Manufacturing Example 1

[0254] 250 g of CMC-Na (weight average molecular weight: 1,500,000, degree of substitution (DS): 0.9), 3.5 g of methylglyoxal, and 0.5 g of oxalic acid were added to 500 g of ethanol solution, stirred at 60°C for 180 minutes, and dried to prepare a binder powder (hereinafter referred to as compound A powder).

[0255] The compound A powder was a compound powder containing a repeating unit represented by the chemical formula 1. The compound A is a compound in which M1 and M2 in the chemical formula 1 are Na, R2 among R1 to R4 is a group represented by the chemical formula 2, the remainder is H, and R5 in the chemical formula 2 is CH3.

[0256] The above compound A powder was dissolved in water to prepare an aqueous solution having a concentration of 1.2 wt%, and the viscosity of the aqueous solution measured at 25°C using a viscometer (Brookfield's DV2T viscometer (RV3 spindle), 30 rpm) was 3000 cP.

[0257] Manufacturing Example 2

[0258] A binder powder (hereinafter referred to as compound B powder) was prepared by the same method as in Manufacturing Example 1, except that an equivalent amount of glyoxal was added instead of methylglyoxal.

[0259] The above compound B powder was a compound powder containing a repeating unit represented by the above chemical formula 1. The above compound B is a compound in which M1 and M2 in the above chemical formula 1 are Na, R2 among R1 to R4 is a group represented by the above chemical formula 2, the rest are H, and R5 in the above chemical formula 2 is H.

[0260] The viscosity measured by the same method as in Manufacturing Example 1 was 3000 cP, except that the above compound B powder was dissolved in water to prepare an aqueous solution with a concentration of 1.2 wt%.

[0261] Manufacturing Example 3

[0262] 250 g of CMC-Na (weight average molecular weight: 100,000, degree of substitution (DS): 0.9), 3.5 g of methylglyoxal, and 0.5 g of oxalic acid were added to 500 g of ethanol solution, stirred at 60°C for 180 minutes, and dried to prepare a binder powder (hereinafter referred to as compound C powder). The compound C powder was a compound powder containing a repeating unit represented by the chemical formula 1.

[0263] The viscosity measured by the same method as in Manufacturing Example 1 was 200 cP, except that the above compound C powder was dissolved in water to prepare an aqueous solution with a concentration of 1.2 wt%.

[0264] Manufacturing Example 4

[0265] 250 g of CMC-Na (weight average molecular weight: 300,000, degree of substitution (DS): 0.9), 3.5 g of methylglyoxal, and 0.5 g of oxalic acid were added to 500 g of ethanol solution, stirred at 60°C for 180 minutes, and dried to prepare a binder powder (hereinafter referred to as compound D powder). The compound D powder was a compound powder containing a repeating unit represented by the chemical formula 1.

[0266] The viscosity measured by the same method as in Manufacturing Example 1 was 500 cP, except that the above compound D powder was dissolved in water to prepare an aqueous solution with a concentration of 1.2 wt%.

[0267] Manufacturing Example 5

[0268] 250 g of CMC-Na (weight average molecular weight: 800,000, degree of substitution (DS): 0.9), 3.5 g of methylglyoxal, and 0.5 g of oxalic acid were added to 500 g of ethanol solution, stirred at 60°C for 180 minutes, and dried to prepare a binder powder (hereinafter referred to as compound E powder). The compound E powder was a compound powder including a repeating unit represented by the chemical formula 1.

[0269] The viscosity measured by the same method as in Manufacturing Example 1 was 1000 cP, except that the above compound E powder was dissolved in water to prepare an aqueous solution with a concentration of 1.2 wt%.

[0270] Manufacturing Example 6

[0271] 250 g of CMC-Na (weight average molecular weight: 1,200,000, degree of substitution (DS): 0.9), 3.5 g of methylglyoxal, and 0.5 g of oxalic acid were added to 500 g of ethanol solution, stirred at 60°C for 180 minutes, and dried to prepare a binder powder (hereinafter referred to as compound F powder).

[0272] The above compound F powder was a compound powder containing a repeating unit represented by the above chemical formula 1.

[0273] The viscosity measured by the same method as in Manufacturing Example 1 was 1500 cP, except that the above compound F powder was dissolved in water to prepare an aqueous solution with a concentration of 1.2 wt%.

[0274] Manufacturing Example 7

[0275] 250 g of CMC-Na (weight average molecular weight: 1,800,000, degree of substitution (DS): 0.9), 3.5 g of methylglyoxal, and 0.5 g of oxalic acid were added to 500 g of ethanol solution, stirred at 60°C for 180 minutes, and dried to prepare a binder powder (hereinafter referred to as compound G powder).

[0276] The above compound G powder was a compound powder containing a repeating unit represented by the above chemical formula 1.

[0277] The viscosity measured by the same method as in Manufacturing Example 1 was 6000 cP, except that the above compound G powder was dissolved in water to prepare an aqueous solution with a concentration of 1.2 wt%.

[0278] Manufacturing Example 8

[0279] 250 g of CMC-Na (weight average molecular weight: 2,000,000, degree of substitution (DS): 0.9), 3.5 g of methylglyoxal, and 0.5 g of oxalic acid were added to 500 g of ethanol solution, stirred at 60°C for 180 minutes, and dried to prepare a binder powder (hereinafter referred to as compound H powder).

[0280] The above compound H powder was a compound powder containing a repeating unit represented by the above chemical formula 1.

[0281] The viscosity measured by the same method as in Manufacturing Example 1 was 9000 cP, except that the above compound H powder was dissolved in water to prepare an aqueous solution with a concentration of 1.2 wt%.

[0282] Manufacturing Example 9

[0283] CMC-Na 250 g (weight average molecular weight: 5,000,000, degree of substitution (DS): 0.4), methylglyoxal 3.5 g, and oxalic acid 0.5 g were added to 500 g of ethanol solution, stirred at 60°C for 180 minutes, and dried to prepare a binder powder (hereinafter referred to as compound J powder).

[0284] The compound J powder above was a compound powder including a repeating unit represented by the chemical formula 1 above. The compound J is a compound in which M1 and M2 in the chemical formula 1 above are Na, R2 among R1 to R4 is a group represented by the chemical formula 2 above, the remainder is H, and R5 in the chemical formula 2 above is CH3.

[0285] Manufacturing Example 10

[0286] A binder powder (hereinafter referred to as compound K powder) was prepared by the same method as in Manufacturing Example 9, except that an equivalent amount of glyoxal was added instead of methylglyoxal.

[0287] The compound K powder above was a compound powder including a repeating unit represented by the chemical formula 1 above. The compound K is a compound in which M1 and M2 in the chemical formula 1 above are Na, R2 among R1 to R4 is a group represented by the chemical formula 2 above, the remainder is H, and R5 in the chemical formula 2 above is H.

[0288] Manufacturing Example 11

[0289] A binder powder (hereinafter referred to as compound L powder) was prepared by the same method as in Manufacturing Example 1, except that 250 g of CMC-Na (weight average molecular weight: 3,000,000, degree of substitution (DS): 0.6) was used.

[0290] Manufacturing Example 12

[0291] A binder powder (hereinafter referred to as compound M powder) was prepared by the same method as in Manufacturing Example 1, except that 250 g of CMC-Na (weight average molecular weight: 4,000,000, degree of substitution (DS): 0.5) was used.

[0292] Manufacturing Example 13

[0293] A binder powder (hereinafter referred to as compound N powder) was prepared by the same method as in Manufacturing Example 1, except that 250 g of CMC-Na (weight average molecular weight: 5,000,000, degree of substitution (DS): 0.3) was used.

[0294] Manufacturing Example 14

[0295] A binder powder (hereinafter referred to as compound O powder) was prepared by the same method as in Manufacturing Example 1, except that 250 g of CMC-Na (weight average molecular weight: 6,000,000, degree of substitution (DS): 0.4) was used.

[0296]

[0297] Example

[0298] Example 1

[0299] (1) Preparation of cathode composition

[0300] The planetary mixer of the mixer (Primix, 2000L class PD mixer) was set and maintained at the maximum operating speed, and natural graphite as a negative active material, carbon black as a conductive material, and compound A powder as a first binder powder were added to the mixer at a weight ratio of 98.9:0.5:0.6 (step S10).

[0301] Thereafter, water was added as the first solvent to the mixer and the first mixing was performed to form a preliminary negative electrode composition in the form of a dough (step S20). The total content of the first solid component, which is the solid component in the preliminary composition, was 70 wt%.

[0302] Water was added as a second solvent to the above mixer to lower the solid content of the preliminary cathode composition by about 5% (step S30).

[0303] In the above mixer, the same amount of compound A powder as the compound A powder added in step S10 was added as a second binder powder and mixed a second time (step S40).

[0304] After the second mixing, water was added as a third solvent to the mixer to dilute, and then SBR was added as a third binder and mixed a third time to prepare a slurry-type negative electrode composition.

[0305] Based on the total solid content of the manufactured cathode composition, the total content of natural graphite, carbon black, and compound A powder was 98.5 wt%, and the content of SBR was 1.5 wt%.

[0306] Based on the total content of the solid content in the negative electrode composition, the total content of the first and second binder powders, i.e., the total content of the compound A, was 1.2 wt%. The weight ratio of the first binder powder and the second binder powder was 1:1.

[0307] (2) Manufacturing of secondary batteries

[0308] The above negative electrode composition was coated, dried, and rolled on a copper current collector to manufacture a negative electrode.

[0309] LiNi as positive electrode active material 0.8 Co 0.1 Mn 0. A slurry-type positive electrode composition was prepared by mixing O2, carbon black as a conductive agent, and PVDF as a binder in a mass ratio of 95:3:2. The positive electrode slurry was coated, dried, and rolled onto an aluminum current collector to prepare a positive electrode.

[0310] The 43 positive electrode sheets and the 44 negative electrode sheets were notched to a predetermined size, stacked, and a separator (polyethylene, 25 ㎛ thick) was interposed between the positive and negative electrodes to form an electrode cell. Then, the tab portions of the positive and negative electrodes were welded. The welded positive electrode / separator / negative electrode assembly was placed in a pouch and sealed on three sides except for the electrolyte injection portion. At this time, the part with the electrode tab was included in the sealing portion. The electrolyte was injected through the electrolyte injection portion, and the electrolyte injection portion was also sealed, followed by impregnation for 12 hours or more to manufacture a secondary battery.

[0311] The electrolyte was prepared using a 1M LiPF6 solution prepared using a mixed solvent of EC / EMC (25 / 75; volume ratio), to which 1 wt% of vinylene carbonate (VC) and 0.5 wt% of 1,3-propenesultone (PRS) were added based on the total weight of the solution.

[0312] Pre-charging was performed on the above lithium secondary battery at a current (5 A) corresponding to 0.25 C for 36 minutes. Degassing was performed after 1 hour, aging was performed for more than 24 hours, and then chemical charge / discharge was performed (charge condition CC-CV 0.2 C 4.2 V 0.05 C CUT-OFF, discharge condition CC 0.2 C 2.5 V CUT-OFF).

[0313] Example 2

[0314] A negative electrode composition and a secondary battery were manufactured by the same method as Example 1, except that the second solvent was not added to the mixer (step S30 was excluded) and the compound A powder was added in five portions in the second mixing (step S40).

[0315] Example 3

[0316] A negative electrode composition and a secondary battery were manufactured by the same method as in Example 1, except that an equivalent amount of compound B powder was used instead of compound A powder.

[0317] Example 4

[0318] A negative electrode composition and a secondary battery were manufactured by the same method as in Example 1, except that an equivalent amount of artificial graphite was used instead of natural graphite as the negative electrode active material.

[0319] Example 5

[0320] A negative electrode composition and a secondary battery were manufactured by the same method as in Example 1, except that an equivalent amount of non-etherified CMC-Na powder (referred to as Compound I powder, a compound including a repeating unit represented by Chemical Formula 3) was used instead of Compound A powder. In Chemical Formula 3, M4 and M5 are Na.

[0321] The viscosity measured by the same method as in Preparation Example 1 was 3000 cP, except that the above compound I powder was dissolved in water to prepare an aqueous solution with a concentration of 1.2 wt%.

[0322] Example 6

[0323] A negative electrode composition and a secondary battery were manufactured by the same method as in Example 1, except that the same amount of compound I powder used in Example 5 was used instead of compound A powder, and the same amount of artificial graphite was used instead of natural graphite as the negative electrode active material.

[0324] Example 7

[0325] A negative electrode composition and a secondary battery were manufactured by the same method as Example 1, except that the second solvent was not added to the mixer (step S30 was excluded).

[0326] Examples 8 to 17

[0327] A negative electrode composition and a secondary battery were manufactured by the same method as Example 1, except that the first binder powder and the second binder powder were changed to the types of compound powders according to Table 1 below.

[0328] Comparative Example 1 (Binder powder added at once)

[0329] A negative electrode composition and a secondary battery were manufactured by the same method as in Example 1, except that steps S10 to S40 in Example 1 were combined into one and all of the components introduced into the mixer at each step were introduced together, that is, introduced and mixed at once.

[0330] The mixing time after all of the above-described ingredients were added to the mixer at once was the same as the total mixing time in each of steps S10 to S40 of Example 1.

[0331] Comparative Example 2 (Divisional injection of binder solution)

[0332] In steps S10 and S20 of Example 1, a negative electrode composition and a secondary battery were manufactured by the same method as in Example 1, except that after the negative electrode active material and the conductive material were added to the mixer, a first binder solution prepared by mixing the first binder powder (compound A powder) with the first solvent in advance was added and mixed (corresponding to the first mixing), and in steps S30 and S40, a second binder solution prepared by mixing the second binder powder (compound A powder) with the second solvent in advance was added and mixed (corresponding to the second mixing).

[0333] Comparative Example 3 (Binder solution injected at once)

[0334] The steps in Comparative Example 2 were combined into one, and all the components introduced into the mixer at each step were introduced together, i.e., introduced and mixed at once, except that a negative electrode composition and a secondary battery were manufactured by the same method as in Comparative Example 2.

[0335] The mixing time after all of the above-described ingredients were added to the mixer at once was the same as the total mixing time in each of steps S10 to S40 of Example 1.

[0336] Types of binder powders and viscosity (cP) based on aqueous solution at 1.2% concentration First binder First viscosity Second binder Second viscosity Example 1 Compound A3000 Compound A3000 Example 2 Compound A3000 Compound A3000 Example 3 Compound B3000 Compound B3000 Example 4 Compound A3000 Compound A3000 Example 5 Compound I3000 Compound I3000 Example 6 Compound I3000 Compound I3000 Example 7 Compound A3000 Compound A3000 Example 8 Compound D500 Compound A3000 Example 9 Compound E1000 Compound A3000 Example 10 Compound F1500 Compound A3000 Example 11 Compound A3000 Compound G6000 Example 12 Compound A3000 Compound H9000 Example 13 Compound C200 Compound A3000 Example 14 Compound D500 Compound F1500 Example 15 Compound G6000 Compound A3000 Example 16 Compound G6000 Compound G6000 Example 17 Compound A3000 Compound F1500 Comparative Example 1 Compound A3000 Compound A3000 Compound A3000 Comparative Example 2 Compound A3000 Compound A3000 Comparative Example 3 Compound A3000 Compound A3000

[0337]

[0338] Example 18

[0339] At step S10, the planetary mixer of the mixer (Primix, 2000L-class PD mixer) was set and maintained at the maximum operating speed, and artificial graphite and SiO as negative active materials, the compound A powder as the first binder powder, and carbon nanotubes (CNTs) as a conductive material were added to the mixer at a weight ratio of 86.8:10:0.75:0.5, and the solid content was adjusted as follows. Except for this, a negative electrode composition and a secondary battery were manufactured by the same method as in Example 1.

[0340] Based on the total content of the solid content in the above negative electrode composition, the total content of artificial graphite, SiO, compound A powder, and carbon nanotubes (CNT) was 98.8 wt%, and the content of SBR was 1.2 wt%. In addition, based on the total content of the solid content in the above negative electrode composition, the total content of the first and second binder powders, i.e., the total content of the compound A, was 1.5 wt%.

[0341] Example 19

[0342] In the above step S10, artificial graphite and SiO as negative active materials, the compound A powder as a first binder powder, and carbon nanotubes (CNTs) as a conductive material were added to the mixer in a weight ratio of 85.3:10:1.5:0.5, and in the step S40, the compound A powder was added in an equal amount as a second binder powder, so that the total content of artificial graphite, SiO, compound A powder, and carbon nanotubes (CNTs) was 98.8 wt% based on the total content of solids in the negative electrode composition, and the content of SBR was 1.2 wt%, except that an negative electrode composition and a secondary battery were manufactured by the same method as in Example 18.

[0343] Based on the total content of the solid content in the above negative electrode composition, the total content of the first and second binder powders, i.e., the total content of the compound A, was 3 wt%.

[0344] Example 20

[0345] In the above step S10, artificial graphite and SiO as negative active materials, the compound A powder as a first binder powder, and carbon nanotubes (CNTs) as a conductive material were introduced into the mixer in a weight ratio of 83.3:10:2.5:0.5, and in the step S40, the compound A powder was introduced in an equal amount as a second binder powder, so that the total content of artificial graphite, SiO, compound A powder, and carbon nanotubes (CNTs) was 98.8 wt% based on the total content of solids in the negative electrode composition, and the content of SBR was 1.2 wt%, except that an negative electrode composition and a secondary battery were manufactured by the same method as in Example 18.

[0346] Based on the total content of the solid content in the above negative electrode composition, the total content of the first and second binder powders, i.e., the total content of the compound A, was 5 wt%.

[0347] Example 21

[0348] In step S10, the planetary mixer of the mixer (Primix, 2000L-class PD mixer) was set and maintained at the maximum operating speed, and natural graphite, artificial graphite, and SiO as negative active materials, the compound J powder as the first binder powder, and carbon nanotubes (CNTs) as a conductive material were introduced into the mixer at a weight ratio of 48:48:3:0.4:0.2, the compound J powder was used as the second binder powder, and the solid content was adjusted as follows. Except for this, a negative electrode composition and a secondary battery were manufactured by the same method as in Example 1.

[0349] Based on the total solid content of the above cathode composition, the total content of natural graphite, artificial graphite, SiO, compound J powder, and carbon nanotubes (CNT) was 98.8 wt%, and the content of SBR was 1.2 wt%.

[0350] Example 22

[0351] A negative electrode composition and a secondary battery were manufactured by the same method as Example 21, except that the second solvent was not added to the mixer (step S30 was excluded) and the compound J powder was added in five portions in the second mixing (step S40).

[0352] Example 23

[0353] A negative electrode composition and a secondary battery were manufactured by the same method as in Example 21, except that an equivalent amount of compound K powder was used instead of compound J powder.

[0354] Example 24

[0355] A negative electrode composition and a secondary battery were manufactured by the same method as Example 21, except that the second solvent was not added to the mixer (step S30 was excluded).

[0356] Example 25

[0357] A negative electrode composition and a secondary battery were manufactured by the same method as Example 21, except that compound L powder was used as the first and second binder powders.

[0358] Example 26

[0359] A negative electrode composition and a secondary battery were manufactured by the same method as Example 21, except that the compound M powder was used as the first and second binder powders.

[0360] Example 27

[0361] A negative electrode composition and a secondary battery were manufactured by the same method as Example 21, except that compound N powder was used as the first and second binder powders.

[0362] Example 28

[0363] A negative electrode composition and a secondary battery were manufactured by the same method as Example 21, except that compound O powder was used as the first and second binder powders.

[0364] Example 29 (First binder content among the first and second binders: 30 wt%)

[0365] At step S10, the planetary mixer of the mixer (Primix, 2000L-class PD mixer) was set and maintained at the maximum operating speed, and natural graphite as an anode active material, carbon black, and compound A powder as a first binder powder were added to the mixer at a weight ratio of 99.14:0.5:0.36, and the solid content was adjusted as follows. Except that this was done in the same manner as in Example 1 to manufacture a cathode composition and a secondary battery.

[0366] Based on the total solid content of the above negative electrode composition, the total content of natural graphite, carbon black, and compound A powder was 98.5 wt%, and the content of SBR was 1.5 wt%. In addition, the weight ratio of natural graphite, carbon black, first binder powder, and second binder powder after the second mixing in step S40 was 98.3:0.5:0.36:0.84.

[0367] Example 30 (content of first binder among first and second binders: 40 wt%)

[0368] A negative electrode composition and a secondary battery were manufactured by the same method as Example 29, except that the weight ratio of natural graphite, carbon black, first binder powder, and second binder powder after the second mixing was 98.3:0.5:0.48:0.72.

[0369] Example 31 (First binder content among the first and second binders: 60 wt%)

[0370] A negative electrode composition and a secondary battery were manufactured by the same method as Example 29, except that the weight ratio of natural graphite, carbon black, first binder powder, and second binder powder after the second mixing was 98.3:0.5:0.72:0.48.

[0371] Example 32 (First binder content among the first and second binders: 70 wt%)

[0372] A negative electrode composition and a secondary battery were manufactured by the same method as Example 29, except that the weight ratio of natural graphite, carbon black, first binder powder, and second binder powder after the second mixing was 98.3:0.5:0.84:0.36.

[0373] Example 33 (First binder content among the first and second binders: 90 wt%)

[0374] A negative electrode composition and a secondary battery were manufactured by the same method as Example 29, except that the weight ratio of natural graphite, carbon black, first binder powder, and second binder powder after the second mixing was 98.3:0.5:1.08:0.12.

[0375]

[0376] Comparative Example 4 (Binder powder added at once)

[0377] A negative electrode composition and a secondary battery were manufactured by the same method as in Example 18, except that steps S10 to S40 in Example 18 were combined into one and all of the components introduced into the mixer at each step were introduced together, i.e., introduced and mixed at once.

[0378] The mixing time after all of the above-described ingredients were added to the mixer at once was the same as the total mixing time in each of steps S10 to S40 of Example 18.

[0379] Comparative Example 5 (Divisional injection of binder solution)

[0380] In steps S10 and S20 of Example 18, a negative electrode composition and a secondary battery were manufactured by the same method as in Example 18, except that after the negative electrode active material and the conductive material were added to the mixer, a first binder solution prepared by mixing the first binder powder (compound A powder) with the first solvent in advance was added and mixed (corresponding to the first mixing), and in steps S30 and S40, a second binder solution prepared by mixing the second binder powder (compound A powder) with the second solvent in advance was added and mixed (corresponding to the second mixing).

[0381] Comparative Example 6 (Binder solution injected at once)

[0382] The steps in Comparative Example 5 were combined into one, and all the components introduced into the mixer at each step were introduced together, i.e., introduced and mixed at once, except that a negative electrode composition and a secondary battery were manufactured by the same method as in Comparative Example 5.

[0383] The mixing time after all of the above-described ingredients were added to the mixer at once was the same as the total mixing time in each of steps S10 to S40 of Example 18.

[0384] Comparative Example 7 (Binder powder added at once)

[0385] A negative electrode composition and a secondary battery were manufactured by the same method as in Example 21, except that steps S10 to S40 in Example 21 were combined into one and all of the components introduced into the mixer at each step were introduced together, that is, introduced and mixed at once.

[0386] The mixing time after all of the above-described ingredients were added to the mixer at once was the same as the total mixing time in each of steps S10 to S40 of Example 21.

[0387] Comparative Example 8 (Divisional injection of binder solution)

[0388] In steps S10 and S20 of Example 21, a negative electrode composition and a secondary battery were manufactured by the same method as in Example 21, except that after the negative electrode active material and the conductive material were added to the mixer, a first binder solution prepared by mixing the first binder powder (compound J powder) with the first solvent in advance was added and mixed (corresponding to the first mixing), and in steps S30 and S40, a second binder solution prepared by mixing the second binder powder (compound J powder) with the second solvent in advance was added and mixed (corresponding to the second mixing).

[0389] Comparative Example 9 (Binder solution injected at once)

[0390] The steps in Comparative Example 8 were combined into one, and all the components introduced into the mixer at each step were introduced together, i.e., introduced and mixed at once, except that a negative electrode composition and a secondary battery were manufactured by the same method as in Comparative Example 2.

[0391] The mixing time after all of the above-described ingredients were added to the mixer at once was the same as the total mixing time in each of steps S10 to S40 of Example 21.

[0392] Comparative Example 10 (Binder powder added at once)

[0393] A negative electrode composition and a secondary battery were manufactured by the same method as Example 32, except that steps S10 to S40 were combined into one and all of the components introduced into the mixer at each step were introduced together, that is, introduced and mixed at once.

[0394] The mixing time after all of the above-described ingredients were added to the mixer at once was the same as the total mixing time in each of steps S10 to S40 of Example 29.

[0395] Comparative Example 11 (Divisional injection of binder solution)

[0396] A negative electrode composition and a secondary battery were manufactured by the same method as in Example 32, except that in steps S10 and S20, a negative electrode active material and a conductive material were added to the mixer, and then a first binder solution prepared by mixing the first binder powder (compound A powder) with the first solvent in advance was added and mixed (corresponding to the first mixing), and in steps S30 and S40, a second binder solution prepared by mixing the second binder powder (compound A powder) with the second solvent in advance was added and mixed (corresponding to the second mixing).

[0397] Comparative Example 12 (Binder solution injected at once)

[0398] The steps in Comparative Example 2 were combined into one, and all the components introduced into the mixer at each step were introduced together, i.e., introduced and mixed at once, except that a negative electrode composition and a secondary battery were manufactured by the same method as in Comparative Example 2.

[0399] The mixing time after all of the above-described ingredients were added to the mixer at once was the same as the total mixing time in each of steps S10 to S40 of Example 29.

[0400]

[0401] Experimental example

[0402] (1) Measurement of the maximum driving current of the mixer

[0403] In the above-described examples 1 to 7, 18, 21 to 24 and 29, the maximum driving current at step S20 and the maximum driving current at step S40 were measured, respectively.

[0404] The above measurements were made using values ​​measured and displayed on the mixer itself. If necessary, additional components for current measurement may be attached to the mixer to measure the maximum drive current. If the mixer is a dual-motor mixer comprising two motors, the larger of the maximum drive currents measured from each of the two motors can be evaluated as the maximum drive current of the mixer.

[0405] The results are shown in Table 2 below.

[0406] Maximum operating current of the mixer (A) First mixing Second mixing Example 1 200 160 Example 2 200 200 Example 3 190 170 Example 4 200 150 Example 5 220 190 Example 6 210 190 Example 7 200 215 Example 18 200 160 Example 21 200 150 Example 22 200 200 Example 23 180 170 Example 24 190 210 Example 29 190 170

[0407]

[0408] (2) Measurement of negative electrode adhesion

[0409] For the cathodes of the above-described examples and comparative examples, the adhesive strength was measured through a 90° peel test. The measuring equipment used was the DS2-N model from IMADA.

[0410] Specifically, the cathode was cut to a length of 18 mm to prepare a sample. A tape was attached to the sample, and the force (90°) required to remove the tape was measured and expressed in units of N / 18 mm.

[0411] The results are shown in Table 3 below.

[0412]

[0413] (3) Internal resistance measurement

[0414] The internal resistance of the secondary batteries of the above-described examples and comparative examples was measured using a 200A class charger / discharger from Wonik PNE.

[0415] Specifically, a current equivalent to 1C was applied for 10 seconds at SOC50% and the direct current internal resistance (DCIR) was measured.

[0416] The results are shown in Table 3 below.

[0417]

[0418] (4) Capacity maintenance rate evaluation

[0419] For the lithium half-cells of the examples and comparative examples, charging (CC-CV 0.33C 4.2V 0.05C CUT-OFF) and discharging (CC 0.33C 2.5V CUT-OFF) were performed 800 times each in a chamber maintained at 25°C, and the discharge capacity at 800 times was divided by the discharge capacity at 1 time and multiplied by 100 to evaluate the capacity retention rate.

[0420] The results are shown in Table 3 below.

[0421]

[0422] (5) Cell expansion rate evaluation

[0423] Each electrode cell was prepared in the same manner as the method for manufacturing a secondary battery according to Examples 18 to 20 and Comparative Examples 4 to 6 described above.

[0424] A compression jig was prepared and adjusted so that the equipment could apply a uniform force of 500 N. The electrode cell was prepared, positioned on the compression jig, and fixed to prevent movement during charging and discharging.

[0425] In the initial state, the thickness of the cell was measured using a thickness measuring device and set as a reference value.

[0426] The above electrode cell was charged and discharged for 100 cycles under the following conditions.

[0427] 1 cycle (5 min): CC / CV charge (0.5C 4.3V 0.05C CUT-OFF) and CC discharge (1.0C 3.0V CUT-OFF) at room temperature (25℃).

[0428] The charge / discharge equipment was linked to a data collection system to synchronize and record thickness change data in real time, and the rate of change in cell thickness was measured every 5 minutes during charge / discharge. After 100 cycles were completed, the rate of change in thickness was evaluated as the cell expansion rate.

[0429] Thickness change rate (%) = (T2-T1) / T1 x 100

[0430] The above T1 is the thickness of the cell in the initial state, and the above T2 is the thickness of the cell after 100 cycles are completed.

[0431] The results are shown in Table 4 below.

[0432]

[0433] (6) Measurement of degree of substitution

[0434] For each compound used as the first and second binder powders (hereinafter referred to as binder compounds), the degree of substitution by methylcarboxylic acid or its salt was measured as follows in accordance with ASTM D 1439-03.

[0435] Specifically, 1 g of the binder compound was placed in a 500 mL Erlenmeyer flask, 100 mL of distilled water and 25 mL of 0.5 N (normal concentration) NaOH were added to the Erlenmeyer flask, and the mixture was stirred at 120° C. for 30 minutes.

[0436] An excess of NaOH aqueous solution was added to the above Erlenmeyer flask, and back-titrated with 0.5 N HCl. The end point was confirmed using a phenolphthalein indicator, and the degree of substitution was calculated according to the following equations 1 and 2.

[0437] [Formula 1]

[0438] DS = 0.162Y A / (1-0.58Y A )

[0439] [Formula 2]

[0440] A = {(Y B x YC )-(Y D x Y E )} / Y F

[0441] In the above equations 1 and 2, Y A is the equivalent consumed per 1 g of binder compound (mmol / g), Y B is the volume of added NaOH (mL), Y C is the concentration of NaOH aqueous solution (N), Y D is the volume (mL) of HCl used in the back titration, Y E is the concentration of HCl solution (N), Y F is the mass (g) of the binder used.

[0442]

[0443] (7) Weight average molecular weight measurement

[0444] For each compound used as the first and second binder powders, samples treated with GPC (gel permeation chromatography) were analyzed using EcoSEC HLC-8320 GPC from Tosoh, and the weight average molecular weight was measured as follows.

[0445] In the above sample treatment, a sample was prepared by filtering a solution in which the sample was completely dissolved through a 0.45 ㎛ Nylon filter without any separate sample pretreatment.

[0446] The above sample was analyzed under the following analytical equipment / conditions to measure the weight average molecular weight of the binder compound.

[0447] i) Analytical instrument: Tosoh, EcoSEC HLC-8320 GPC

[0448] ii) Detector: RI-detector

[0449] iii) Developing solution: 0.1M NaNO3

[0450] iv) Column: TSKgel GMPWxl (7.8 mm X 300 mm) 2ro

[0451] v) Temperature: 40 ℃

[0452] vi) Flow rate: 1 mL / min

[0453] vii) Sample injection volume: 200 mL, 0.5 mg / mL

[0454] viii) Standard substance: polysaccharide

[0455] ix) Data processing software: EcoSEC software

[0456]

[0457] (8) Measurement of solid content of cathode composition

[0458] For the cathode compositions of the examples and comparative examples, the weight of the cathode composition was measured and dried in an oven.

[0459] The weight of the dried solids was measured.

[0460] The percentage was calculated by dividing the weight of the measured solid by the weight of the measured cathode composition.

[0461]

[0462] (9) Measurement of phase angle of cathode composition

[0463] The cathode composition was maintained at 25℃, and each phase angle was measured using a rheometer (model name: Kinexus rotational, manufacturer: Malvern) as a measuring device. After setting the distance between the circular plates of the rheometer to a constant 1 mm, the cathode composition corresponding to the volume filling the gap was placed and 10 -2 The phase angle was measured while increasing the amplitude by approximately two times in the range of Hz to 102 Hz, and the results at 1 Hz are shown in Table 5 below.

[0464]

[0465] In the 'column' corresponding to the binder (chemical formula) in Table 3 below, the chemical formula indicating the repeating unit contained in each binder compound is described. In addition, the meaning of 'input once' in the 'column' corresponding to the input form means that in the input process of inputting the components for manufacturing the negative electrode composition, each component was input together into a mixer and performed in one step.

[0466]

[0467] Binder (chemical formula) injection form evaluation result Adhesive force (N / 18mm) Internal resistance (mΩ) Capacity retention rate (%) Example 11 Solid, divided injection 0.52 0.97 19 0.4 Example 21 Solid, divided injection 0.48 1.00 9 8 7.7 Example 31 Solid, divided injection 0.50 0.99 2 8 9.2 Example 41 Solid, divided injection 0.37 0.90 7 9 1.1 Example 53 Solid, divided injection 0.40 1.05 3 8 3.2 Example 63 Solid, divided injection 0.37 1.04 2 8 2.5 Example 71 Solid, divided injection 0.46 1.1 1 9 7 8.1 Example 81 Solid, divided injection 0.51 0.94 4 9 0.1 Example 91 Solid, divided Input 0.53 0.94 29 0.6 Example 101 Solid, divided input 0.51 0.94 69 1.6 Example 111 Solid, divided input 0.57 1.00 19 2.2 Example 121 Solid, divided input 0.62 1.05 39 0.5 Example 131 Solid, divided input 0.49 0.96 9 7 8.1 Example 141 Solid, divided input 0.31 1.1 12 8 3.9 Example 151 Solid, divided input 0.50 1.2 9 173.1 Example 161 Solid, divided input 0.59 1.30 87 1.9 Example 171 Solid, divided input 0.33 1.1 6 4 8 1.4 Example 181 Solid, divided input 0.48 1.00 9 8 7.7 Example 191 Solid, divided Input 0.521.08191.2 Example 201 Solid, split input 0.561.09991.5 Example 211 Solid, split input 0.651.01088.1 Example 221 Solid, split input 0.700.97291.5 Example 231 Solid, split input 0.580.98289.0 Example 241 Solid, split input 0.461.11980.7 Example 251 Solid, split input 0.701.08090.9 Example 261 Solid, split input 0.761.09791.0 Example 271 Solid, split input 0.541.12180.1 Example 281 Solid, split input 0.491.08984.5 Example 291 Solid, split Input 0.39 0.97 6 9 1.5 Example 301 Solid, divided input 0.50 0.97 5 9 2.8 Example 311 Solid, divided input 0.51 0.97 2 9 3.9 Example 321 Solid, divided input 0.45 0.97 9 4.3 Example 331 Solid, divided input 0.34 0.96 9 3.5 Comparative example 11 Solid, single input 0.32 1.5 2 36 1.1Comparative Example 21 Liquid, divided injection 0.441.13573.3Comparative Example 31 Liquid, single injection 0.251.76360.7Comparative Example 41 Solid, single injection 0.321.52361.1Comparative Example 51 Liquid, divided injection 0.441.13573.3Comparative Example 61 Liquid, single injection 0.451.12372.7Comparative Example 71 Solid, single injection 0.331.50360.2Comparative Example 81 Liquid, divided injection 0.441.13373.1Comparative Example 91 Liquid, single injection 0.401.14270.2Comparative Example 101 Solid, single injection 0.321.5230.32Comparative Example 111 Liquid, divided injection 0.441.1350.44Comparative Example 121 Liquid, Once invested 0.251.7630.25.

[0468]

[0469] Evaluation Results Cell Expansion Rate (%, @100 cycle) Example 188.0 Example 196.0 Example 206.1 Comparative Example 413.2 Comparative Example 512.0 Comparative Example 613.5

[0470]

[0471] Phase angle(°) Example 2950.1 Example 3053.5 Example 3154.3 Example 3252.4 Example 3350.8 Comparative Example 1030.2 Comparative Example 1143.8 Comparative Example 1231.5

[0472]

[0473] Referring to Tables 2 and 3, in the examples in which the negative active material powder and the first binder powder were first introduced into the mixer, the first solvent was introduced and mixed for the first time, and the second binder powder was introduced and mixed for the second time, the electrode adhesion and capacity retention rate were improved overall and the internal resistance was reduced compared to the comparative examples.

[0474] In Examples 5 and 6, in which a compound including a repeating unit represented by Chemical Formula 3 (non-etherified CMC-Na) was used instead of a compound including a repeating unit represented by Chemical Formula 1 as the first and second binder powders, the electrode adhesion and capacity retention rate were relatively lowered and the internal resistance increased compared to the other examples.

[0475] In Examples 7 and 24, where the maximum driving current of the mixer in the first mixing was smaller than the maximum driving current of the mixer in the second mixing, the electrode adhesion and capacity retention rate were lowered and the internal resistance was increased compared to the Examples.

[0476] Referring to Table 4, the cell expansion rate was evaluated as low for the electrode cells according to Examples 18 to 20, while the cell expansion rate was evaluated as high for the electrode cells according to Comparative Examples 4 to 6.

[0477] Referring to Table 5, it was also found that the phase angles in Examples 29 to 33 were all evaluated to be 45° or higher, indicating improved dispersion between active materials. In Comparative Examples 10 to 12, when the phase angle is less than 45°, it indicates a high degree of aggregation of components within the negative electrode composition.

[0478] In Comparative Examples 1, 4, 7, and 10, where the binder powder was not fed in two stages but in a single stage, the electrode adhesion and capacity retention rate decreased and the internal resistance increased compared to the examples. Fig. 5 is an internal image of a stirrer taken after preparing the negative electrode composition according to Comparative Example 1. Referring to Fig. 5, in Comparative Example 1, the binder powders agglomerated within the binder solution, which caused a solvent impact phenomenon, resulting in a decrease in the negative electrode adhesion, mechanical stability, and processability.

[0479] In Comparative Examples 2, 3, 5, 6, 8 and 9, where a binder solution was used instead of a solid binder powder, the electrode adhesion and capacity retention rate were lowered and the internal resistance increased compared to the examples, and in Comparative Example 3, where the binder solution was introduced in a single step, the electrode adhesion, internal resistance and capacity retention rate were further deteriorated.

Claims

1. A step of adding negative electrode active material powder and first binder powder to a mixer, adding a first solvent, and performing a first mix to form a preliminary negative electrode composition; and A method for producing a negative electrode composition for a secondary battery, comprising the step of forming the above preliminary negative electrode composition, adding a second binder powder to the mixer, and performing a second mixing to form a negative electrode composition.

2. In paragraph 1, A method for producing a negative electrode composition for a secondary battery, comprising: adding the negative active material powder and the first binder powder to the mixer in operation to form a powder mixture, and then adding the first solvent.

3. In paragraph 1, A method for producing a negative electrode composition for a secondary battery, further comprising a step of introducing a second solvent into the mixer between the step of forming the preliminary negative electrode composition and the step of forming the negative electrode composition.

4. In paragraph 1 or paragraph 3, A method for producing a negative electrode composition for a secondary battery, wherein the second binder powder is divided into two or more parts and added to the mixer.

5. In paragraph 3, A method for producing an anode composition for a secondary battery, wherein the total content of the first solid component, which is a solid component in the above-mentioned preliminary anode composition, is 65 wt% to 75 wt%.

6. In paragraph 5, A method for producing an anode composition for a secondary battery, wherein the total content of the second solid content, which is a solid content in the preliminary anode composition into which the second solvent is added, is 3 wt% to 9 wt% less than the total content of the first solid content.

7. In paragraph 1, A method for producing a negative electrode composition for a secondary battery, wherein the first binder powder and the second binder powder each independently include a compound including a repeating unit represented by the following chemical formula 1: [Chemical Formula 1] (In the chemical formula 1 above, M1 and M2 are each independently Na or Li, at least one of R1 to R4 is a group represented by the chemical formula 2 below, the others are each independently H or a group represented by the chemical formula 2 below, and n is an integer) [Chemical formula 2] (In the above chemical formula 2, R5 is -CH0, -CH2CHO, -COCH3, or -CH2COCH3, and *- indicates a bonding position bonded to oxygen).

8. In paragraph 7, A method for producing a negative electrode composition for a secondary battery, wherein the first binder powder and the second binder powder each independently contain, or do not contain, a compound including a repeating unit represented by the following chemical formula 3 in an amount of 20 wt% or less based on the total content of each binder powder: [Chemical Formula 3] (In the above chemical formula 3, M4 and M5 are each independently Na or Li, and n is an integer).

9. In paragraph 1, A method for producing a negative electrode composition for a secondary battery, wherein the negative electrode active material comprises at least one selected from the group consisting of artificial graphite and natural graphite.

10. In paragraph 1, A method for producing a negative electrode composition for a secondary battery, wherein the first solvent and the second solvent each independently comprise at least one selected from the group consisting of water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, and t-butanol.

11. In paragraph 1, A method for producing a negative electrode composition for a secondary battery, wherein, in the step of forming the negative electrode composition, at least one of a third solvent and a third binder is further added to the mixer after the second mixing and a third mixing is performed to form the negative electrode composition.

12. In paragraph 11, A method for producing a negative electrode composition for a secondary battery, comprising: adding the third solvent to the mixer, adding the third binder, and performing the third mixing to form the negative electrode composition.

13. In paragraph 1, A method for producing a negative electrode composition for a secondary battery, wherein the first viscosity of the first binder powder is 200 cP to 6,500 cP.

14. In paragraph 1, A method for producing a negative electrode composition for a secondary battery, wherein the second viscosity, which is the viscosity of the second binder powder, is 1500 cP to 9500 cP.

15. A method for producing a negative electrode composition for a secondary battery, wherein the first viscosity in claim 13 is 500 cP to 3500 cP.

16. A method for producing a negative electrode composition for a secondary battery, wherein the second viscosity in the 14th paragraph is 3000 cP to 7000 cP.

17. In paragraph 14, A method for producing a negative electrode composition for a secondary battery, wherein the ratio of the second viscosity to the first viscosity is 1 to 10.

18. A method for producing a negative electrode composition for a secondary battery, wherein the ratio of the second viscosity to the first viscosity in the 17th paragraph is 1 to 6.

19. Negative current collector; and A negative electrode for a secondary battery, comprising a negative electrode active material layer formed from a negative electrode composition manufactured by the manufacturing method of claim 1, and disposed on at least one surface of the negative electrode current collector.

20. A negative electrode for a secondary battery according to Article 19; and A secondary battery comprising a positive electrode opposite to the negative electrode.

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