Slurry composition for secondary battery positive electrode, secondary battery positive electrode, and secondary battery

Abstract

The present application provides a slurry composition for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery. The slurry composition for a positive electrode of a secondary battery includes a positive electrode active material, a conductive material, a binding material, and a dispersant including at least two components of component A including at least one of an aryl carboxylate, a fatty acid ester, and a phosphoric acid ester, component B including a silicone oil, and component C including an N-vinylpyrrolidone-vinyl carboxylate polymer. The slurry composition for a positive electrode described in the present application has excellent dispersibility, and can produce a positive electrode for a secondary battery and a secondary battery that can exhibit good high-temperature characteristics.

Description

Technical Field

[0001] This application belongs to the field of new energy technology, specifically relating to a slurry composition for a secondary battery positive electrode and its application, a composite material layer for a secondary battery positive electrode, a positive electrode for a secondary battery, and a secondary battery. Background Technology

[0002] With the rapid development of secondary batteries, especially lithium-ion batteries, they have been widely used in many fields. In the manufacturing process of lithium-ion batteries, the stability of the slurry is one of the important indicators of its properties. The stability of the slurry directly affects its storage time; the more stable the slurry, the more continuous the production process can be. At the same time, the stability of the slurry also significantly affects the coating effect. The more stable the slurry, the more stable the coating process, the more stable the coating surface density, and the more stable and consistent the performance of the prepared battery.

[0003] However, currently, the positive electrode slurry for lithium secondary batteries generally uses polyvinylidene fluoride (PVDF) as a binder. The interaction between PVDF molecular chains and positive electrode particles is unstable, leading to a decrease in slurry stability and the occurrence of defects such as gelation, incomplete coating, slope, and burrs, which affect the performance of the battery. Summary of the Invention

[0004] The problem the invention aims to solve

[0005] In this context, to further improve the battery characteristics of a secondary battery, it is generally required that the electrode active materials be well dispersed in the slurry composition to form a uniform electrode composite layer. Therefore, the object of this application is to provide a slurry composition for the positive electrode of a secondary battery that exhibits excellent dispersibility and can be used to manufacture a secondary battery with good high-temperature characteristics. Furthermore, the object of this application is to provide a positive electrode for manufacturing a secondary battery with good high-temperature characteristics, and a secondary battery with good high-temperature characteristics.

[0006] To solve all or part of the above-mentioned technical problems, one of the objectives of this application is to provide a slurry composition for the positive electrode of a secondary battery, comprising a positive electrode active material, a conductive material, and a binder material. The slurry composition for the secondary battery further comprises a dispersant, which comprises at least two components selected from component A, component B, or component C. Component A comprises at least one of aryl carboxylic acid ester, fatty acid ester, and phosphate ester. Component B comprises silicone oil. Component C comprises an N-vinylpyrrolidone-vinyl carboxylic acid ester polymer.

[0007] The second objective of this application is to provide the application of the above-mentioned slurry composition for secondary battery positive electrode in the preparation of composite material layer for secondary battery positive electrode, positive electrode for secondary battery, or secondary battery.

[0008] The third objective of this application is to provide a composite material layer for a secondary battery positive electrode, wherein the composite material layer is formed from a slurry composition for a secondary battery positive electrode as described in any of the above technical solutions.

[0009] The third objective of this application is to provide a positive electrode for a secondary battery, which is formed from a slurry composition for a secondary battery positive electrode as described in any of the above technical solutions.

[0010] The fourth objective of this application is to provide a secondary battery, including a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode includes the positive electrode for secondary batteries described in the above technical solutions.

[0011] Solution for solving the problem

[0012] The purpose of this application is to advantageously solve all or part of the above-mentioned problems. The slurry composition for the positive electrode of a secondary battery according to this application is characterized by comprising a positive electrode active material, a conductive material, a binder, and a dispersant. The dispersant comprises at least two components selected from component A, component B, or component C. Component A comprises at least one of aryl carboxylic acid esters, fatty acid esters, and phosphate esters; component B comprises silicone oil; and component C comprises an N-vinylpyrrolidone-vinyl carboxylic acid polymer. The positive electrode slurry composition having the above-described composition exhibits excellent dispersibility, and secondary batteries with a positive electrode formed using this positive electrode slurry composition can exhibit good high-temperature characteristics.

[0013] Here, the slurry composition for the positive electrode of the secondary battery of this application preferably includes at least two of the above-mentioned dispersant components A, B, or C. Component A includes at least one of aryl carboxylic acid esters, fatty acid esters, and phosphate esters; component B includes silicone oil; and component C includes an N-vinylpyrrolidone-vinyl carboxylic acid ester polymer. This is because a single component is unstable during charge and discharge at high temperatures and is prone to decomposition. When any two components are used in combination, they stabilize the structure through hydrogen bonding, thereby reducing the thickness expansion of the secondary battery with a positive electrode formed using this slurry composition, and thus further improving the high-temperature characteristics of the secondary battery.

[0014] In this application, the conductive material in the slurry composition for the positive electrode of a secondary battery preferably comprises a fibrous conductive carbon material. This is because if the slurry composition for the positive electrode comprises a fibrous conductive carbon material as the conductive material, the internal resistance of the secondary battery having a positive electrode formed using this slurry composition can be significantly reduced, thereby further improving the high-temperature characteristics of the secondary battery.

[0015] In addition, fibrous conductive carbon materials are usually prone to agglomeration and have poor dispersibility. However, since the positive electrode slurry composition of this application has the composition specified above, it is able to achieve good dispersibility.

[0016] Furthermore, the slurry composition for the positive electrode of the secondary battery of this application preferably contains 5% by mass or more and 100% by mass or less of the aforementioned conductive material. This is because if the slurry composition for the positive electrode contains the fibrous conductive carbon material in the aforementioned specified proportion, good dispersibility can be obtained, and the high-temperature characteristics of the secondary battery having a positive electrode formed using the slurry composition for the positive electrode can be further improved.

[0017] Furthermore, the slurry composition for the positive electrode of the secondary battery of this application preferably contains component A in an amount of 10% by mass or more and 50% by mass or less of the dispersant. This is because if the slurry composition for the positive electrode contains component A in an amount within the above-mentioned range, the dispersibility of the slurry composition for the positive electrode can be further improved, and the high-temperature characteristics of the secondary battery having a positive electrode formed using the slurry composition for the positive electrode can be further improved.

[0018] Furthermore, the slurry composition for the positive electrode of the secondary battery of this application preferably contains component B in an amount of 10% by mass or more and 80% by mass or less of the dispersant. This is because if the slurry composition for the positive electrode contains component B in an amount within the above range, not only can the slurry composition for the positive electrode have better dispersibility, but a secondary battery with better high-temperature characteristics can also be obtained.

[0019] Furthermore, the slurry composition for the positive electrode of the secondary battery of this application preferably contains component C in an amount of 1% by mass or more and 50% by mass or less of the dispersant. This is because if the slurry composition for the positive electrode contains component C in an amount within the above range, not only can the slurry composition for the positive electrode have better dispersibility, but a secondary battery with better high-temperature characteristics can also be obtained.

[0020] Furthermore, the slurry composition for the positive electrode of the secondary battery in this application preferably has a shear rate of 10 s. -1 The ratio (η0 / η1) of the viscosity η0 at a shear rate of 1000 s⁻¹ to the viscosity η1 at a shear rate of 1000 s⁻¹ is more than 2 and less than 20. This is because if the η0 / η1 of the positive electrode slurry composition is within the above range, the coatability of the positive electrode slurry composition becomes good when it is coated onto a current collector to form a positive electrode composite material layer, thus enabling the good manufacture of both the positive electrode and the secondary battery.

[0021] Furthermore, the purpose of this application is to advantageously solve the aforementioned problems. The positive electrode for secondary batteries of this application is characterized by being formed using any of the aforementioned secondary battery positive electrode slurry compositions. Using a positive electrode obtained using any of the aforementioned secondary battery positive electrode slurry compositions can impart excellent high-temperature characteristics to the secondary battery.

[0022] Furthermore, the purpose of this application is to advantageously solve the aforementioned problems. The secondary battery of this application is characterized by having a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode is the aforementioned positive electrode for a secondary battery. In this way, the secondary battery having the aforementioned positive electrode for a secondary battery as its positive electrode exhibits excellent high-temperature characteristics.

[0023] Invention Effects

[0024] This application provides a slurry composition for the positive electrode of a secondary battery that exhibits excellent dispersibility and can be used to manufacture secondary batteries with good high-temperature characteristics.

[0025] Furthermore, according to this application, it is possible to provide a positive electrode capable of manufacturing a secondary battery with good high-temperature characteristics, and a secondary battery with good high-temperature characteristics. Detailed Implementation

[0026] Embodiments of this application are described in detail below. However, these embodiments are exemplary, and this application is not limited thereto.

[0027] Here, the slurry composition for the positive electrode of a secondary battery of this application can be used to obtain the positive electrode of a secondary battery such as a lithium-ion secondary battery (e.g., the positive electrode for a secondary battery of this application). Specifically, the slurry composition for the positive electrode of this application can be used, for example, to form a positive electrode composite material layer in a positive electrode for a secondary battery. Furthermore, the secondary battery of this application is characterized by having a positive electrode for a secondary battery formed using the slurry composition for the positive electrode of this application.

[0028] Slurry composition for positive electrode of secondary battery

[0029] The slurry composition for the positive electrode of a secondary battery disclosed in this application comprises a positive electrode active material, a conductive material, a binder, and a dispersant. The dispersant comprises at least two components selected from component A, component B, or component C. Component A comprises at least one of aryl carboxylic acid esters, fatty acid esters, and phosphate esters; component B comprises silicone oil; and component C comprises an N-vinylpyrrolidone-vinyl carboxylate polymer. Because the slurry composition for the positive electrode of a secondary battery disclosed in this application employs the aforementioned composition, it enables secondary batteries with a positive electrode formed using this slurry composition to exhibit excellent high-temperature characteristics.

[0030] Positive electrode active material

[0031] As the positive electrode active material for lithium-ion secondary batteries, materials capable of absorbing and releasing lithium are typically used. Specifically, this may include lithium and one or more composite oxides of metals selected from cobalt, manganese, nickel, and combinations thereof. As a specific example, compounds represented by one or more of the following chemical formulas can be used: Li a A 1-b X bD2(0.90≤a≤1.8,0≤b≤0.5);Li a A 1-b X b O 2-c D c (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);Li a HAVE BEEN 1-b X b O 2-c D c (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);Li a HAVE BEEN 2-b X b O 4-c D c (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);Li a Ni 1-b-c Co b X c D α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.5,0<d≤2);Li a Ni 1-b- c Co b X c O 2-α T α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0<α<2);Li a Ni 1-b-c Co b X c O 2-α T2(0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0<α<2);Li a Ni 1-b-c Mr b X c D α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0<α≤2);Li a Ni 1-b-c Mr b X c O 2-α T α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0<α<2);Li a Ni 1-b-c Mr b X c O 2-αT2 (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni b E c G d O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1); Li a Ni b Co c Mn d GeO2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); QO2; QS2; LiQS2; V2O5; LiV2O5; LiZO2; LiNiVO4; Li (3-f) J2(PO4)3 (0≤f≤2); Li (3-f) Fe2(PO4)3 (0≤f≤2); Li a FePO4 (0.90≤a≤1.8).

[0032] In the above chemical formulas, A is selected from Ni, Co, Mn and combinations thereof; X is selected from Al, Ni, Co, Mn, Cr, Fe, Nb, Mg, Sr, V, rare earth elements and combinations thereof; D is selected from O, F, S, P and combinations thereof; E is selected from Co, Mn and combinations thereof; T is selected from F, S, P and combinations thereof; G is selected from Al, Cr, Mn, Fe, Nb, Mg, La, Ce, Sr, V and combinations thereof; Q is selected from Ti, Mo, Mn and combinations thereof; Z is selected from Cr, V, Fe, Sc, Y and combinations thereof; J is selected from V, Cr, Mn, Co, Ni, Cu and combinations thereof.

[0033] The compound may have a coating layer on the surface, or it may be mixed with another compound having a coating layer. The coating layer may include at least one coating element compound selected from oxides, hydroxides, hydroxyoxides, oxycarbonates, and hydroxycarbonates of the coating element. The compound used for the coating layer may be amorphous or crystalline. The coating element included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Nb, Zr, or mixtures thereof. The coating layer can be formed by using these elements in the compound in a manner that does not negatively affect the properties of the positive electrode active material. For example, the method may include any coating method (e.g., spraying, dipping, etc.), but since it is well known to those skilled in the art, it is not described in more detail here.

[0034] In addition, there are no particular limitations on the amount and particle size of the positive electrode active material, and it can be the same as the positive electrode active material that has been used all along.

[0035] conductive materials

[0036] There are no particular limitations on the conductive material as long as it is conductive. Particle-shaped conductive carbon materials such as carbon black, graphite, and carbon flakes; fibrous conductive carbon materials such as carbon fibers, carbon nanotubes, and vapor-grown carbon fibers; and fibers and foils of various metals can be used as conductive materials. From the viewpoint of effectively reducing the internal resistance of the secondary battery, it is preferable to use at least fibrous conductive carbon materials as conductive materials, more preferably a combination of carbon black and fibrous conductive carbon materials, even more preferably a combination of acetylene black and fibrous conductive carbon materials, and particularly preferably a combination of acetylene black and carbon nanotubes.

[0037] These can be used individually or in combination of two or more.

[0038] Furthermore, the total content of conductive material in the slurry composition for the positive electrode of a secondary battery is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, even more preferably 1 part by mass or more, particularly preferably more than 3 parts by mass, preferably 10 parts by mass or less, and more preferably 8 parts by mass or less, relative to 100 parts by mass of positive electrode active material. This is because if the total content of conductive material is at or above the aforementioned lower limit, the internal resistance can be further reduced effectively in a secondary battery having a positive electrode formed using the slurry composition for the positive electrode, and the high-temperature characteristics can be further improved. Furthermore, if the total content of conductive material is at or below the aforementioned upper limit, a decrease in the dispersibility of the slurry composition for the positive electrode can be prevented.

[0039] fibrous conductive carbon materials

[0040] As a fibrous conductive carbon material, a fibrous conductive carbon material containing carbon nanotubes is preferred. This is because if a fibrous conductive carbon material containing carbon nanotubes is used, the high conductivity of the carbon nanotubes can better reduce the internal resistance of the secondary battery, further improving its high-temperature performance.

[0041] Furthermore, in this application, the "fibrous conductive carbon material" is defined as having an aspect ratio (long diameter / short diameter) of 5 or more. Moreover, the aspect ratio of the fibrous conductive carbon material is preferably greater than 10. Furthermore, the "aspect ratio" can be determined by observing the material using a SEM (scanning electron microscope), measuring the maximum diameter (long diameter) and the fiber diameter (short diameter) in the direction orthogonal to the maximum diameter for any fibrous conductive carbon material, and calculating the ratio of the long diameter to the short diameter (long diameter / short diameter).

[0042] Furthermore, when using fibrous conductive carbon materials containing carbon nanotubes, the carbon nanotubes used in the fibrous conductive carbon material are not particularly limited, and single-layer carbon nanotubes and / or multi-layer carbon nanotubes can be used. Moreover, from the viewpoint of reducing the manufacturing cost of the cathode slurry composition, at least multi-layer carbon nanotubes can be used. Additionally, commercially available fibrous conductive carbon materials are readily available.

[0043] Here, the average fiber diameter of the fibrous conductive carbon material is preferably 0.5 nm or more, more preferably 1 nm or more, generally less than 1 μm, preferably 200 nm or less, more preferably 100 nm or less, and even more preferably 30 nm or less. This is because if the average fiber diameter of the fibrous conductive carbon material is at or above the aforementioned lower limit, the excellent conductivity of the fibrous conductive carbon material can be fully utilized, suppressing the increase in the internal resistance of the secondary battery, and thus enabling the secondary battery to exhibit better high-temperature characteristics. Furthermore, if the average fiber diameter of the fibrous conductive carbon material is below the aforementioned upper limit, the fibrous conductive carbon material is better stored in the positive electrode slurry composition, for example, when the positive electrode slurry composition is coated onto the current collector to form a positive electrode composite material layer, the coating properties are better, and the high-temperature characteristics of the secondary battery can be further improved.

[0044] Furthermore, in this application, the "average fiber diameter" can be determined by measuring the diameter of more than 100 randomly selected fibrous conductive carbon materials using SEM (scanning electron microscopy) or TEM (transmission electron microscopy) as the number average diameter. Particularly when the diameter of the fibrous conductive carbon materials is small, observation using TEM is preferred. Moreover, the average fiber diameter of the fibrous carbon nanostructure can be adjusted by changing the manufacturing method and conditions of the fibrous conductive carbon materials, or by combining multiple fibrous conductive carbon materials obtained by different manufacturing methods.

[0045] Average fiber length

[0046] Furthermore, the average fiber length of the fibrous conductive carbon material is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 3 μm or more, preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 30 μm or less. This is because if the average fiber length of the fibrous conductive carbon material is at or above the aforementioned lower limit, the excellent conductivity of the fibrous conductive carbon material can be fully utilized, suppressing the increase in the internal resistance of the secondary battery, thus enabling the secondary battery to exhibit better high-temperature characteristics. Furthermore, if the average fiber length of the fibrous conductive carbon material is below the aforementioned upper limit, the fibrous conductive carbon material can be stored more effectively in the positive electrode slurry composition. Furthermore, if the average fiber length of the fibrous conductive carbon material is below the aforementioned upper limit, for example, when the positive electrode slurry composition is coated onto a current collector to form a positive electrode composite material layer, the coatability is better, and the flexibility of the formed positive electrode composite material layer is improved, resulting in further improvement in the high-temperature characteristics of the secondary battery.

[0047] Adhesive material

[0048] Here, any adhesive material that can be used in a secondary battery is acceptable, and there are no particular limitations. For example, a polymer obtained by polymerizing a monomer composition containing monomers that exhibit adhesive properties (synthetic polymers, such as addition polymers obtained by addition polymerization) can be used as an adhesive material. Examples of such polymers include: aliphatic conjugated diene / aromatic vinyl copolymers (polymers mainly containing aliphatic conjugated diene monomer units and aromatic vinyl monomer units), acrylic polymers (polymers mainly containing (meth)acrylate monomer units), fluorinated polymers (polymers mainly containing fluorinated monomer units), acrylic / acrylamide copolymers (polymers mainly containing (meth)acrylic acid units and (meth)acrylamide units), and acrylonitrile polymers (polymers mainly containing (meth)acrylonitrile units). One of these can be used alone, or two or more can be combined in any ratio. Moreover, aliphatic conjugated diene / aromatic vinyl copolymers, acrylic / acrylamide copolymers, and acrylonitrile polymers are preferred among these. Preferably, it includes one or more of polyvinylidene fluoride (PVDF), polyacrylate (PAA), and polyacrylonitrile (PAN), more preferably polyvinylidene fluoride (PVDF), polyacrylate (PAA), or polyacrylonitrile (PAN).

[0049] Among them, aliphatic conjugated diene monomers capable of forming aliphatic conjugated diene monomer units in aliphatic conjugated diene / aromatic vinyl copolymers, aromatic vinyl monomers capable of forming aromatic vinyl monomer units in aliphatic conjugated diene / aromatic vinyl copolymers, (meth)acrylate monomers capable of forming (meth)acrylate monomer units in acrylic polymers, and fluorinated monomers capable of forming fluorinated monomer units in fluorinated polymers can be used.

[0050] dispersant

[0051] The slurry composition for the positive electrode of the secondary battery disclosed in this application contains a dispersant comprising at least two components selected from component A, component B, or component C. Component A comprises at least one of aryl carboxylic acid esters, fatty acid esters, and phosphate esters; component B comprises silicone oil; and component C comprises an N-vinylpyrrolidone-vinyl carboxylic acid polymer. Using a single component will not result in good dispersibility of the positive electrode slurry composition. A single component is unstable during charge-discharge processes at high temperatures and is prone to decomposition. When any two components are used in combination, they stabilize the structure through hydrogen bonding, thereby reducing the thickness expansion of the secondary battery with a positive electrode formed using this positive electrode slurry composition, and thus further improving the high-temperature characteristics of the secondary battery.

[0052] Component A above includes at least one of aryl carboxylic acid esters, fatty acid esters, and phosphate esters.

[0053] The aforementioned aryl carboxylic acid esters can be esters formed by monohydric or polyhydric alcohols with 1-10 carbon atoms and phthalic acid. For example, they can be one or more of dimethyl phthalate, diethyl phthalate, dipropyl phthalate, dibutyl phthalate, dipentyl phthalate, dihexyl phthalate, diheptyl phthalate, dioctyl phthalate, dinonyl phthalate, and didecyl phthalate.

[0054] The aforementioned fatty acid esters can be esters formed by a monohydric alcohol or polyhydric alcohol having 1-10 carbon atoms and a monohydric or polycarboxylic acid having 3-12 carbon atoms. For example, they can be one or more of the following: diethyl adipate, dipropyl adipate, dibutyl adipate, dipentyl adipate, dihexyl adipate, diheptyl adipate, dioctyl adipate, diisooctyl adipate, diethyl sebacate, dipropyl sebacate, dibutyl sebacate, dipentyl sebacate, dihexyl sebacate, diheptyl sebacate, and dioctyl sebacate.

[0055] The aforementioned phosphate ester can be an ester formed by a monohydric alcohol or polyhydric alcohol with 1-10 carbon atoms and phosphoric acid, for example, it can be one or more of tricresyl phosphate, trioctyl phosphate, tributyl phosphate, and triphenyl phosphate. Preferably, the phthalate is dibutyl phthalate (DBP) and / or dioctyl phthalate (DOP), the phosphate ester is tricresyl phosphate (TCP) and / or trioctyl phosphate (TOP), and the fatty acid ester is dioctyl sebacate (DOS) and / or dioctyl adipate (DOA).

[0056] Furthermore, the proportion of component A in the dispersant is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. This is because if the dispersant contains component A at or above the aforementioned lower limit, the dispersibility of the positive electrode slurry composition is improved, resulting in better coatability when, for example, the positive electrode slurry composition is coated onto a current collector to form a positive electrode composite material layer. Furthermore, if the dispersant contains component A at or below the aforementioned upper limit, the dispersibility and viscosity stability of the positive electrode slurry composition are improved, resulting in better coatability when, for example, the positive electrode slurry composition is coated onto a current collector to form a positive electrode composite material layer. Moreover, if the proportion of component A in the dispersant is within the aforementioned range, the high-temperature characteristics of the secondary battery can be further improved.

[0057] Component B above includes silicone oil, for example, dimethyl polysiloxane (INCI name: dimethyl silicone oil), dimethyl polysiloxane with hydroxyl-terminated groups (INCI name: polydimethylsiloxane alcohol), methylphenyl polysiloxane, decamethylcyclopentasiloxane, dodecylcyclohexasiloxane, silicone oil, polyether-modified siloxane, high-polymer siloxane with an average degree of polymerization of 650-10000, amino-modified siloxane, betaine-modified siloxane, alkyl-modified siloxane, alkoxy-modified siloxane, mercapto-modified siloxane, carboxyl-modified siloxane, fluorine-modified siloxane, etc.

[0058] Among the above, examples of amino-modified siloxanes include: aminopropylmethylsiloxane-dimethylsiloxane copolymer (INCI name: aminopropyldimethylsiloxane), aminoethylaminopropylsiloxane-dimethylsiloxane copolymer (INCI name: amino-terminated dimethylsiloxane), and aminoethylaminopropylmethylsiloxane-dimethylsiloxane copolymer (INCI name: trimethylsilylamino-terminated dimethylsiloxane), etc.

[0059] Furthermore, the proportion of component B in the dispersant is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. This is because if the dispersant contains component B at or above the aforementioned lower limit, the dispersibility of the positive electrode slurry composition can be improved, and it can play a role in inhibiting the decomposition of component A during high-temperature charge and discharge, thereby further improving the high-temperature characteristics of the secondary battery.

[0060] Component C mentioned above includes N-vinylpyrrolidone-vinyl carboxylic acid ester polymers, such as N-vinylpyrrolidone-vinyl acetate, N-vinylpyrrolidone-vinyl propionate, and N-vinylpyrrolidone-vinyl butyrate. Component C forms numerous hydrogen bonds with components A or B, playing a significant role in maintaining the structural stability of components A or B at high temperatures. The proportion of component C in the dispersant is preferably 1% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. This is because if the dispersant contains component B at or above the aforementioned lower limit, the dispersibility of the positive electrode slurry composition can be improved, inhibiting the decomposition of components A or B during high-temperature charge-discharge processes, and further improving the high-temperature characteristics of the secondary battery.

[0061] Other ingredients

[0062] In addition to the components mentioned above, the slurry composition for the positive electrode of a secondary battery may also contain other components. Furthermore, other components that may be included in the positive electrode slurry composition include, for example, reinforcing materials, leveling agents, viscosity modifiers, electrolyte additives, and any other components. These components are not particularly limited as long as they do not affect the battery reaction; known components can be used, and these components may be used individually or in combination of two or more in any ratio.

[0063] solvent

[0064] There are no particular limitations on the solvent used as a slurry composition for the positive electrode of a secondary battery; known storage media such as water or N-methylpyrrolidone (NMP) can be used.

[0065] Preparation method of slurry composition for positive electrode

[0066] The slurry composition for the positive electrode of a secondary battery can be prepared by storing the above-mentioned components simultaneously or in any order in a solvent. Specifically, the slurry composition for the positive electrode can be prepared by mixing the above-mentioned components and solvent using a ball mill, sand mill, bead mill, or planetary mixer.

[0067] Positive electrode for secondary batteries

[0068] The positive electrode for secondary batteries of this application is characterized in that it is formed using any of the aforementioned slurry compositions for secondary batteries, and generally has a structure in which a positive electrode composite material layer formed using the aforementioned positive electrode slurry composition is formed on the current collector. Furthermore, since the positive electrode for secondary batteries of this application is obtained using the aforementioned specified positive electrode slurry composition, when used as a positive electrode in a secondary battery, it enables the secondary battery to exhibit excellent high-temperature characteristics.

[0069] current collector

[0070] As a current collector, materials that are both conductive and electrochemically durable can be used. Specifically, current collectors can be made of metals such as aluminum, iron, copper, nickel, stainless steel, titanium, tantalum, gold, and platinum. Furthermore, one of the above materials can be used alone, or two or more can be combined in any ratio.

[0071] Positive electrode composite material layer

[0072] The positive electrode composite material layer is formed by the following processes: coating a slurry composition for a secondary battery positive electrode (coating process) and drying the coated slurry composition for a secondary battery positive electrode (drying process).

[0073] Coating process

[0074] There are no particular limitations on the method for coating a secondary battery positive electrode slurry composition onto a current collector, and known methods can be used. Specifically, coating methods include blade coating, dip coating, reverse roller coating, direct roller coating, gravure printing, extrusion, and brush coating. In this case, the positive electrode slurry composition can be coated only on one side of the current collector or on both sides. Furthermore, the thickness of the positive electrode slurry composition film on the current collector before drying can be appropriately set according to the thickness of the positive electrode composite layer obtained after drying.

[0075] Drying process

[0076] There is no particular limitation on the method for drying the positive electrode slurry composition coated on the current collector; known methods can be used, such as drying methods based on warm air, hot air, low-humidity air, vacuum drying, and drying methods based on irradiation by infrared rays, electron beams, etc. By drying the positive electrode slurry composition coated on the current collector in this way, a positive electrode composite material layer can be formed on the current collector, resulting in a positive electrode having a current collector and a positive electrode composite material layer.

[0077] Furthermore, after the drying process, the positive electrode composite material layer can be pressurized using methods such as die pressing or roller pressing. This pressurization process improves the adhesion between the positive electrode composite material layer and the current collector. In this case, if the positive electrode composite material layer is formed using the slurry composition for secondary battery positive electrodes of this application, a positive electrode with excellent flexibility even after pressurization can be obtained.

[0078] Secondary batteries

[0079] Furthermore, the secondary battery of this application is characterized by having a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode is the aforementioned positive electrode for the secondary battery of this application. Additionally, the negative electrode can be a known negative electrode. Moreover, since the secondary battery of this application has the aforementioned positive electrode for the secondary battery of this application as its positive electrode, it exhibits excellent high-temperature characteristics.

[0080] Furthermore, the following example illustrates the case where the secondary battery is a lithium-ion secondary battery, but this application is not limited to the example described below.

[0081] negative electrode

[0082] The negative electrode can typically be a known negative electrode. The composition of the negative electrode is well known to those skilled in the art. Generally, the negative electrode includes a conductive substrate and a negative electrode material coated or filled onto the conductive substrate. The negative electrode material includes a negative electrode active material and a binder. The negative electrode active material is not particularly limited and can use conventional lithium-intercalating and releasing negative electrode active materials, such as carbon materials or silicon-based materials. The carbon material is selected from one or more of the following: non-graphitized carbon, graphite, or carbon or pyrolytic carbon obtained by high-temperature oxidation of polyacetylenic polymers, coke, sintered organic polymers, and activated carbon. The sintered organic polymer can be a product obtained by sintering and carbonizing phenolic resins, epoxy resins, etc. The silicon-based material includes silicon oxides or silicon carbides.

[0083] The type and content of the negative electrode binder are well known to those skilled in the art, and may include one or more of fluorinated resins and polyolefin compounds such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, hydroxyethyl cellulose, and polyvinyl alcohol. The negative electrode material may also include a conductive agent to increase the conductivity of the electrode and reduce the internal resistance of the battery. The conductive agent is not particularly limited and may be one or more of conventional negative electrode conductive agents in the art, such as carbon black, nickel powder, and copper powder. The negative electrode conductive substrate may be a conventional negative electrode conductive substrate used in lithium-ion batteries, such as stamped metal, metal foil, mesh metal, or foamed metal. In a specific embodiment of the present invention, copper foil is used as the negative electrode conductive substrate.

[0084] The negative electrode can be prepared using conventional methods. For example, the negative electrode material can be mixed with a solvent, coated onto the conductive substrate, dried, and then rolled or not rolled to obtain the negative electrode. The methods and conditions for drying and rolling are well known to those skilled in the art.

[0085] diaphragm

[0086] There are no particular limitations on the type of separator, and examples include: microporous membranes using polyolefin-based resins (polyethylene, polypropylene, polybutene, polyvinyl chloride); microporous membranes using resins such as polyethylene terephthalate, polycyclic olefins, polyethersulfone, polyamide, polyimide, polyimide amide, polyaramid, polycyclic olefins, nylon, and polytetrafluoroethylene; woven or nonwoven fabrics using polyolefin fibers; and aggregates of particles formed from insulating materials. Among these, microporous membranes using polyolefin-based resins are preferred from the perspective of reducing the overall membrane thickness, thereby increasing the ratio of electrode composite material layers within the secondary battery and thus increasing the capacity per unit volume. Microporous membranes made from polyethylene resin are more preferred.

[0087] electrolyte

[0088] As an electrolyte, an organic electrolyte in which the supporting electrolyte is dissolved in an organic solvent is typically used. As the supporting electrolyte, lithium salts can be used, for example, in lithium-ion secondary batteries. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, C4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, and (C2F5SO2)NLi. Among these, LiPF6, LiClO4, and CF3SO3Li are preferred because they readily dissolve in solvents and exhibit high degrees of dissociation. Furthermore, one electrolyte can be used alone, or two or more can be used in combination. Since there is a general tendency for higher dissociation degrees of supporting electrolytes to result in higher lithium-ion conductivity, the lithium-ion conductivity can be adjusted according to the type of supporting electrolyte.

[0089] As for the organic solvent used in the electrolyte, there are no particular limitations as long as it can dissolve and support the electrolyte. For example, in lithium-ion secondary batteries, carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butyl carbonate (BC), and methyl ethyl carbonate (EMC) are preferred; esters such as γ-butyrolactone, methyl formate, ethyl acetate, propyl propionate, and ethyl propionate are preferred; ethers such as 1,2-dimethoxyethane and tetrahydrofuran are preferred; and sulfur-containing compounds such as sulfolane and dimethyl sulfoxide are preferred. Mixtures of these solvents can also be used. Among these, carbonates are preferred because they have a high dielectric constant and a wide stable potential range. Since there is a general tendency for lower viscosity solvents to have higher lithium-ion conductivity, the lithium-ion conductivity can be adjusted according to the type of solvent. Furthermore, the concentration of the electrolyte in the electrolyte can be appropriately adjusted.

[0090] Battery assembly

[0091] Furthermore, the secondary battery of this application is not particularly limited and can be manufactured using known assembly methods. Specifically, the secondary battery of this application can be manufactured, for example, by winding, folding, or otherwise shaping the obtained positive electrode, negative electrode, and separator into a battery shape, placing them in a battery container, injecting electrolyte into the battery container, and sealing it. Here, to prevent the internal pressure of the secondary battery from rising, overcharging, or over-discharging, overcurrent protection components such as fuses and PTC elements, porous metal mesh, and conductive plates can also be provided as needed. In addition, the shape of the secondary battery can be any of the following: coin-shaped, button-shaped, sheet-shaped, cylindrical, square, or flat.

[0092] Example

[0093] The present application is described in detail below based on embodiments, but the present application is not limited to these embodiments. In addition, in the following description, unless otherwise specified, "%" and "parts" are used to indicate quantities based on mass.

[0094] The viscosity, viscosity ratio, dispersibility and coatability of the slurry composition for the positive electrode of secondary batteries, the flexibility of the positive electrode, and the high-temperature characteristics of lithium-ion secondary batteries were determined and evaluated using the following methods.

[0095] (1) Dispersion

[0096] The dispersibility of the slurry composition for the positive electrode of the secondary battery described in this application was measured using a fineness meter (groove depth: 0 μm to 100 μm) according to JIS K5600-2-5. The dispersibility was then evaluated according to the following criteria.

[0097] According to the above measurements, the smaller the particle size, the higher the storage capacity and the better the dispersibility of the slurry composition for the positive electrode of secondary batteries. In Table 1, A, B, C, and D in the "Dispersibility" column represent:

[0098] A: Particle size less than 30μm

[0099] B: Particle size is greater than 30μm and less than 50μm

[0100] C: Particle size greater than 50μm and less than 70μm

[0101] D: Particle size is 70μm or larger

[0102] (2) Coating properties

[0103] In this application, the coatability of the slurry composition for the positive electrode of a secondary battery is evaluated by using the smoothness index of the positive electrode composite material layer formed by the positive electrode slurry composition.

[0104] Specifically, a positive electrode composite material layer is formed on a current collector using a positive electrode slurry composition. For the positive electrode raw material having this positive electrode composite material layer before roll pressing, a smoothness index is calculated from the thickness (layer thickness), and the smoothness index is used for evaluation. More specifically, firstly, the layer thickness is measured at 10 arbitrary points within 2 cm from both ends of the positive electrode raw material before roll pressing, and the average value (average thickness of the ends) is calculated. In addition, similarly, the layer thickness is measured at 10 arbitrary points within 2 cm from the center of the positive electrode raw material before roll pressing to both sides, and the average value (average thickness of the central portion) is calculated. Then, the smoothness index (i.e., the percentage of the absolute value of the difference between the average layer thickness at the ends and the average layer thickness at the central portion to the average layer thickness at the central portion) is calculated according to the following formula (1), and the smoothness index is used for evaluation based on the following criteria.

[0105] Smoothness index (%) = (|average layer thickness at the ends - average layer thickness in the center| / average layer thickness in the center) × 100…(1)

[0106] A lower smoothness index indicates higher smoothness of the cathode composite layer and better coatability of the cathode slurry composition. In Table 1, A, B, and C in the "Coatability" column represent:

[0107] A: Smoothness index less than 3%

[0108] B: Smoothness index is above 3% and less than 8%.

[0109] C: Smoothness index is above 8%

[0110] (3) Softness

[0111] The flexibility of the cathode material is evaluated by examining the presence and absence of cracks and fractures in the cathode material before roll pressing. Specifically, the state of cracks and fractures in the cathode material is observed according to the evaluation criteria in JIS K5600-8-4 as shown below.

[0112] The more difficult it is to observe cracks and fissures, the better the flexibility of the positive electrode. In Table 1, A, B, C, D, and E in the "Flexibility" column represent:

[0113] A: Even if it's magnified twice, it won't be perceptible to the eye.

[0114] B: A 2x increase can be visually perceived on less than 5% of the surface.

[0115] C: It can be barely recognized with normal corrected vision.

[0116] D: It can be clearly identified with normal corrected vision.

[0117] E: Typically refers to a large fracture with a width of 1 mm.

[0118] (4)High temperature characteristics

[0119] After electrolyte injection, the fabricated lithium-ion secondary batteries were left to stand at 25°C for 5 hours. Then, they were charged at 0.2C using a constant current method at 25°C until the cell voltage reached 3.65V, followed by aging at 60°C for 12 hours. Next, they were discharged at 0.2C using a constant current method at 25°C until the cell voltage reached 3.00V. Then, they were charged using a constant current-conversion ... Then, the battery was discharged at a constant current of 0.2C until the cell voltage reached 3.00V, and the discharge capacity at this point was denoted as CY. The high-temperature capacity retention rate, expressed as (CY / CX)×100 (%), was calculated and evaluated using the following benchmarks. A higher high-temperature capacity retention rate indicates less degradation of the lithium-ion secondary battery under high-temperature storage (i.e., better high-temperature storage characteristics). In Table 1, A, B, C, and D in the "High-Temperature Performance" column represent:

[0120] A: High-temperature capacity retention rate is over 90%.

[0121] B: High-temperature capacity retention rate is above 85% and less than 90%.

[0122] C: High-temperature capacity retention is above 80% and below 85%.

[0123] D: High-temperature capacity retention rate is less than 80%.

[0124] Example 1

[0125] Preparation of slurry composition for positive electrode

[0126] 97 parts of lithium cobalt oxide (4.5VLCO, Xiamen Tungsten New Energy) as the positive electrode active material, 1 part of dispersant (30 wt% component A01, 70 wt% component B01), 1 part of polyvinylidene fluoride, and 1 part of acetylene black were added to a dual planetary mixer equipped with a storage tank. The powder was mixed at 25°C for 20 minutes. Then, N-methylpyrrolidone (NMP) solvent was added to adjust the solid content and slurry viscosity, and the mixture was mixed for another 20 minutes to obtain a storage solution. The obtained storage solution was degassed under reduced pressure to obtain a slurry composition for the positive electrode of a lithium-ion secondary battery. The dispersibility of the obtained positive electrode slurry composition was then evaluated according to the above method. The results are shown in Table 1.

[0127] Manufacturing of the positive electrode

[0128] The obtained cathode slurry composition was coated onto a 9μm thick aluminum foil as a current collector, with the dried cathode composite layer having a thickness of approximately 60μm. Next, the aluminum foil coated with the cathode slurry composition was transported in an oven at 60°C and a speed of 0.5m / min for 2 minutes, and then transported in an oven at 120°C for 2 minutes for heat treatment, thereby obtaining the cathode material before roll forming. The coatability of the obtained cathode material before roll forming was then evaluated according to the above method. The results are shown in Table 1.

[0129] Next, the obtained cathode material was calendered using a roll forming process to fabricate a lithium-ion secondary battery cathode with a cathode composite layer thickness of 45 μm. Then, the flexibility of the obtained lithium-ion secondary battery cathode was evaluated according to the method described above. The results are shown in Table 1.

[0130] Manufacturing of negative electrode

[0131] In a dual planetary mixer equipped with a storage device, 97 parts of artificial graphite as the negative electrode active material and 1.0 part of carboxymethyl cellulose as a viscosity modifier (based on solids content) were added, along with an appropriate amount of ion-exchanged water. The mixture was stirred at 25°C for 60 minutes. Then, the solids content was adjusted to 52% using ion-exchanged water, and the mixture was stirred at 25°C for 15 minutes to obtain a mixture. Two parts of a 40% solids content styrene-butadiene copolymer solution and ion-exchanged water were added to the obtained mixture, adjusting the final solids content to 42%, and then stirred for 10 minutes to obtain a storage solution. The obtained storage solution was degassed under reduced pressure to obtain a slurry composition for a lithium-ion secondary battery negative electrode.

[0132] Next, the lithium-ion secondary battery negative electrode slurry composition obtained above is coated onto a copper foil (5 μm thick) serving as the current collector, with a dried negative electrode composite layer thickness of approximately 70 μm. Furthermore, the copper foil coated with the lithium-ion secondary battery negative electrode slurry composition is transported in an oven at 60°C and a speed of 0.5 m / min for 2 minutes, and then transported in an oven at 120°C for 2 minutes for heat treatment, thereby obtaining the negative electrode raw material before roll forming. Then, the obtained negative electrode raw material is calendered using a roll forming process to produce a lithium-ion secondary battery negative electrode with a negative electrode composite layer thickness of 50 μm.

[0133] Manufacturing of lithium-ion secondary batteries

[0134] The lithium-ion secondary battery obtained above is configured with its positive electrode in contact with the aluminum-plastic film outer packaging, with the current collector surface facing it. Furthermore, a single-layer polyethylene separator (65 mm wide, 500 mm long, 7 μm thick, and 53% porosity), manufactured by a dry process, is configured on the surface of the positive electrode composite layer side of the positive electrode. Next, the lithium-ion secondary battery negative electrode obtained above is configured on the separator with the negative electrode composite layer surface facing the separator. Then, a 12% by mass LiPF6 solution is filled into the aluminum-plastic film material as the electrolyte. The electrolyte solvent is a mixed solvent of ethylene carbonate / ethyl methyl carbonate / propylene carbonate / ethyl propionate / propyl propionate = 1 / 1 / 1 / 1 / 1 (mass ratio), and the electrolyte additives are 2% by mass ethylene sulfate and 4% by mass succinate. Finally, heat-sealing is performed at 150°C to seal the opening of the aluminum packaging material, thus manufacturing the lithium-ion secondary battery.

[0135] Furthermore, the high-temperature characteristics of the obtained lithium-ion secondary batteries were evaluated using the methods described above. The results are shown in Table 1.

[0136] Examples 2-17:

[0137] The only difference between Examples 2-17 and Example 1 is that the conductive materials, binders, and dispersants used in Examples 2-17 were changed as shown in Table 1. Otherwise, the preparation of the secondary battery slurry composition, the preparation of the separator, and the manufacture of the negative electrode, positive electrode, and secondary battery were carried out in the same manner as in Example 1. Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0138] Comparative Examples 1-7:

[0139] The only difference between Comparative Examples 1-7 and Example 1 is that the conductive materials, binder, and dispersant used in Comparative Examples 1-7 were changed as shown in Table 1. Otherwise, the preparation of the slurry composition for secondary batteries, the preparation of the separator, and the manufacture of the negative electrode, positive electrode, and secondary battery were carried out in the same manner as in Example 1. Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0140] Table 1. Addition of relevant components and performance test results in Examples 1-17 and Comparative Examples 1-7.

[0141]

[0142]

[0143] The abbreviations for components A and B in Table 1 are shown in Table 2 below. In Table 1, CO1 represents N-vinylpyrrolidone-vinyl acetate polymer. Component A includes at least one of aryl carboxylic acid esters, fatty acid esters, and phosphate esters; component B includes silicone oil; and component C includes N-vinylpyrrolidone-vinyl acetate polymer (CO1). All of these substances are commercially available.

[0144] The abbreviations for components A and B in the dispersant listed in Table 1 and Table 2 have the following meanings:

[0145] Component A abbreviation Component B abbreviation Dimethyl phthalate A01 Polyether modified siloxane B01 Dioctyl adipic acid A02 Dimethylpolysiloxane B02 Dibutyl adipic acid A03 Dodecylcyclohexasiloxane B03 Tributyl phosphate A04 Fluorine-modified siloxanes B04

[0146] The technical solution of this application is analyzed in conjunction with Tables 1 and 2:

[0147] (1) Comparative Example 1 and Comparative Example 1 show that, without the use of a dispersant, the slurry composition for the positive electrode has poor dispersibility and obvious electrode cracks, making it difficult to manufacture the positive electrode and secondary battery.

[0148] (2) Comparing Comparative Examples 1 and 2-7, it can be seen that, compared with not using a dispersant, using a single-component dispersant can improve the dispersion and coating properties of the positive electrode slurry composition to a certain extent. However, the flexibility of the positive electrode prepared using the positive electrode slurry composition is still poor, and the high-temperature performance of the secondary battery assembled with the positive electrode is still poor.

[0149] (3) Comparative Examples 1-17 and 2-7 show that, compared to using a single-component dispersant, the positive electrode slurry composition using at least two dispersant components exhibits significantly superior dispersibility and coatability. The positive electrode prepared with this slurry has better flexibility, and the secondary battery assembled with this positive electrode exhibits significantly better high-temperature performance. Furthermore, it shows excellent effects in binder material systems of polyvinylidene fluoride (PVDF), polyacrylate (PAA), or polyacrylonitrile (PAN). This indicates that when the dispersant contains at least two of components A, B, and C, it can stabilize the structure by forming abundant hydrogen bonds, thereby reducing the thickness expansion of the secondary battery formed from the positive electrode slurry composition and further improving the high-temperature characteristics of the secondary battery.

[0150] (4) Comparing Examples 3 and 5, and Examples 6 and 7, it can be seen that the dispersibility and coatability of the positive electrode slurry composition containing dispersants of components A, B and C are further improved compared to dispersants containing any two of components A, B and C, thereby further improving the high-temperature performance of the secondary battery prepared therefrom.

[0151] (5) Comparison of Comparative Examples 1-4 and Comparative Examples 5-7 shows that when the conductive material includes carbon nanotubes (CNTs), the high-temperature performance of the prepared secondary battery is better. This is because the slurry composition for the positive electrode containing fibrous conductive carbon material can significantly reduce the internal resistance of the secondary battery assembled with the positive electrode formed therefrom, thus further improving the high-temperature characteristics of the secondary battery.

[0152] (6) Comparing Examples 1 and 4, and Examples 13 and 14, it can be seen that when the dispersant contains two of components A, B and C, the dispersant containing component C has better dispersion and coating performance, and the high-temperature performance of the secondary battery prepared may be better.

[0153] In summary, the positive electrode slurry composition formulated according to the above specifications has excellent dispersibility and coatability, and the secondary battery with the positive electrode formed using the positive electrode slurry composition can exhibit good high-temperature characteristics.

[0154] This application is industrially applicable: According to this application, it is possible to provide a slurry composition for the positive electrode of a secondary battery that exhibits excellent dispersibility and can be used to manufacture secondary batteries with good high-temperature characteristics.

[0155] Furthermore, according to this application, it is possible to provide: a positive electrode capable of manufacturing a secondary battery with good high-temperature characteristics, and a secondary battery with good high-temperature characteristics.

[0156] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A slurry composition for the positive electrode of a secondary battery, comprising a positive electrode active material, a conductive material, and a binder material, characterized in that: The slurry composition further includes a dispersant, which includes component C and further includes component A and / or component B; and the content of component C is 20wt% to 50wt% of the dispersant, the content of component A is 10wt% to 50wt% of the dispersant, and the content of component B is 40wt% to 70wt% of the dispersant. Component A includes at least one of aryl carboxylic acid esters, fatty acid esters, and phosphate esters; component B includes silicone oil, which is selected from one or more of polyether-modified siloxanes, amino-modified siloxanes, betaine-modified siloxanes, alkoxy-modified siloxanes, mercapto-modified siloxanes, and carboxyl-modified siloxanes; and component C is an N-vinylpyrrolidone-vinyl acetate polymer.

2. The slurry composition for the positive electrode of a secondary battery according to claim 1, characterized in that: The content of component A is 15wt% to 40wt% of the dispersant.

3. The slurry composition for the positive electrode of a secondary battery according to claim 2, characterized in that: The content of component A is 20wt% to 30wt% of the dispersant.

4. The slurry composition for the positive electrode of a secondary battery according to claim 1, characterized in that: The conductive material is present in a proportion of 0.1 wt% to 10 wt% of the positive electrode active material.

5. The slurry composition for the positive electrode of a secondary battery according to claim 1, characterized in that: The aryl carboxylic acid esters include one or more of dimethyl phthalate, diethyl phthalate, dipropyl phthalate, dibutyl phthalate, dipentyl phthalate, dihexyl phthalate, diheptyl phthalate, dioctyl phthalate, dinonyl phthalate, and didecyl phthalate; And / or, the fatty acid ester includes one or more of diethyl adipate, dipropyl adipate, dibutyl adipate, dipentyl adipate, dihexyl adipate, diheptyl adipate, dioctyl adipate, diisooctyl adipate, diethyl sebacate, dipropyl sebacate, dibutyl sebacate, dipentyl sebacate, dihexyl sebacate, diheptyl sebacate, and dioctyl sebacate; And / or, the phosphate ester includes one or more of tricresyl phosphate, trioctyl phosphate, tributyl phosphate, and triphenyl phosphate.

6. The slurry composition for the positive electrode of a secondary battery according to claim 5, characterized in that: Component A includes one or more of dibutyl phthalate, dioctyl phthalate, tricresyl phosphate, trioctyl phosphate, dioctyl sebacate, or dioctyl adipate.

7. The slurry composition for the positive electrode of a secondary battery according to claim 1, characterized in that: The amino-modified siloxane includes one or more of aminopropylmethylsiloxane-dimethylsiloxane copolymer, aminoethylaminopropylsiloxane-dimethylsiloxane copolymer, and aminoethylaminopropylmethylsiloxane-dimethylsiloxane copolymer.

8. The slurry composition for the positive electrode of a secondary battery according to claim 1, characterized in that: The conductive material comprises fibrous conductive carbon material.

9. The slurry composition for the positive electrode of a secondary battery according to claim 8, characterized in that: The fibrous conductive carbon material includes carbon nanotubes; and / or, the fibrous conductive carbon material contains 5 wt% to 100 wt% of the conductive material; and / or, the aspect ratio of the fibrous conductive carbon material is greater than 5; and / or, the average fiber diameter of the fibrous conductive carbon material is 0.5 nm to 1 μm. And / or, the average fiber length of the fibrous conductive carbon material is 1 μm to 200 μm.

10. The slurry composition for the positive electrode of a secondary battery according to claim 1, characterized in that: The adhesive material comprises one or more of polyvinylidene fluoride, polyacrylate, and polyacrylonitrile.

11. The slurry composition for the positive electrode of a secondary battery according to claim 1, characterized in that: The dispersant includes component A, component B and component C.

12. The slurry composition for the positive electrode of a secondary battery according to claim 1, characterized in that: The slurry composition for the positive electrode of the secondary battery is subjected to a shear rate of 10 s. -1 The viscosity η0 at a shear rate of 1000 s⁻¹ is related to its viscosity at a shear rate of 1000 s⁻¹. -1 The viscosity η1 ratio is 2~20.

13. The use of the slurry composition for the positive electrode of a secondary battery according to any one of claims 1-12 in the preparation of a composite material layer for the positive electrode of a secondary battery, a positive electrode for a secondary battery, or a secondary battery.

14. A composite material layer for the positive electrode of a secondary battery, characterized in that: The positive electrode composite material layer is formed from the slurry composition for the positive electrode of a secondary battery as described in any one of claims 1 to 12.

15. A positive electrode for a secondary battery, characterized in that: The positive electrode for the secondary battery is formed from the slurry composition for the positive electrode of the secondary battery according to any one of claims 1 to 12.

16. A secondary battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that: The positive electrode includes the positive electrode for a secondary battery as described in claim 15.

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