Paste for secondary battery as well as preparation method and application of paste

Abstract

The invention discloses paste for a secondary battery as well as a preparation method and application of the paste. The paste for the secondary battery is prepared from the following components in parts by mass: 1 to 10 parts of conductive additive, 0.02 to 1 part of polymer, 88 to 98 parts of dispersion medium and 0.0001 to 1 part of compound A, the compound A has one or more of structures from formula 1 to formula 4. By adding the specific compound A into the paste for the secondary battery, the transmission efficiency of lithium ions can be remarkably enhanced, and by applying the paste for the secondary battery to the secondary battery, the internal resistance of the secondary battery can be reduced, and the cycle characteristic of the battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a paste for secondary batteries, a preparation method and application thereof. BACKGROUND

[0002] In the prior art, secondary batteries such as lithium ion secondary batteries have been widely used in various fields due to their small size, light weight and high energy density, and the ability to be repeatedly charged and discharged. In particular, in recent years, the importance of lithium ion secondary batteries as a core energy device for electric vehicles (EV) and hybrid electric vehicles (HEV) has become increasingly prominent, and the market has put forward higher requirements for the performance improvement thereof. In view of this, in order to further improve the performance of secondary batteries such as lithium ion secondary batteries, the industry has carried out in-depth improvement research on battery components including electrodes.

[0003] In the technical field of secondary batteries, the structure of an electrode generally includes a current collector and an electrode composite material layer, i.e. a positive electrode composite material layer or a negative electrode composite material layer, formed on the current collector. Traditionally, in the process of preparing these electrode composite material layers, a dispersion material composed of a polymer is used to uniformly disperse a conductive additive in a dispersion medium, thereby preparing a paste suitable for secondary batteries. Subsequently, the paste for secondary batteries is mixed with an electrode active material to prepare a slurry for secondary battery electrodes. By further processing the slurry to remove the dispersion medium therein, the desired electrode composite material layer can be formed.

[0004] For the application of carbon nanomaterials with high aspect ratio (such as carbon nanotubes) or large specific surface area (such as graphene) in the electrode composite material layer, although such carbon nanomaterials have excellent conductivity, their easy aggregation property leads to dispersion difficulty, which in turn affects the good formation of the electrode composite material layer. In the traditional method, although the addition of a polymer can assist in dispersing these carbon nanomaterials, the non-conductive nature of the polymer itself increases the internal resistance of the battery, thereby adversely affecting the performance of the battery.

[0005] Therefore, it is an urgent problem for those skilled in the art to develop a paste for secondary batteries that can reduce the resistance of the battery for application in the technical field of secondary batteries. SUMMARY

[0006] Therefore, the present application provides a paste for secondary batteries, which can be used to prepare an electrode composite material layer containing a polymer and effectively reduce the internal resistance of the secondary battery.

[0007] The present application provides a paste for a secondary battery, comprising, in mass parts: 1 to 10 parts of a conductive aid, 0.02 to 1 part of a polymer, 88 to 98 parts of a dispersion medium, and 0.0001 to 1 part of a compound A;

[0008] The compound A has one or more of the structures of Formula 1 to Formula 4;

[0009]

[0010] wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 each independently is C1 to C 30 alkyl, C2 to C 30 alkenyl, C4 to C 30 dienyl, C4 to C 30 alkynediyl, C1 to C 20 alkoxy, C5 to C 24 cycloalkyl, C6 to C 24 aryl, C3 to C 10 cycloalkenyl, C5 to C8 cycloalkadienyl, halogen-substituted C5 to C 24 aryl, halogen-substituted C5 to C 24 alkyl, or trimethylsilyl.

[0011] The paste for a secondary battery described in the present application includes a compound A. In some specific implementations, the R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 each independently is C6 to C 10 alkyl, C6 to C 10 alkenyl, C6 to C 10 dienyl, C6 to C 10 alkoxy, C6 to C 10 cycloalkyl, C6 to C 10 aryl, C6 to C 10 cycloalkenyl, C6 to C 10cycloalkenyl, halogen or trimethylsilyl. The mass fraction of the compound A is 0.0001 parts to 1 part, which can be 0.0001 parts, 0.0005 parts, 0.001 parts, 0.005 parts, 0.01 parts, 0.05 parts, 0.1 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 0.95 parts, 0.98 parts, 1 part.

[0012] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 The alkyl group in the groups R1, R2, R3, R4, R5, R6, R7, R8, R9, R 30 is typically understood to mean a linear or branched C1-C 24 alkyl group, preferably a C1-C8alkyl group, more preferably a C1-C8alkyl group. C1-C8alkyl includes, for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, t-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, neopentyl, 1-ethylpropyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl, 1-ethyl-2-methylpropyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl and n-octadecyl.

[0013] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 The alkenyl group in the groups R1, R2, R3, R4, R5, R6, R7, R8, R9, R 30 is typically understood to mean a C2-C 30 alkenyl group, preferably a C2-C8alkenyl group. More preferably, the alkenyl group is vinyl or allyl.

[0014] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 The dienyl group in the groups R1, R2, R3, R4, R5, R6, R7, R8, R9, R 30dialkyl, preferably C4-C 30 dialkyl. More preferably, the dialkyl group is butadienyl or pentadienyl.

[0015] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 The alkyl groups in the above-mentioned groups of radicals are typically understood as meaning C1-C 1- C1-C 20 alkyl, preferably C1-C 10 alkyl, more preferably methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, n-pentyl and n-hexyl.

[0016] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 The aryl groups in the above-mentioned groups of radicals are typically understood as meaning C5-C 24 aryl, preferably C6-C 14 aryl, more preferably C6-C 12 aryl. Examples of C6-C 24 aryl groups are phenyl, o-tolyl, p-tolyl or m-tolyl, naphthyl, phenanthryl, anthryl and fluorenyl.

[0017] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 The heteroaryl groups in the above-mentioned groups of radicals have the same definition as given above for aryl groups, with the exception that one or more of the skeletal carbon atoms are replaced by a heteroatom selected from the group consisting of nitrogen, sulfur and oxygen. Examples of such heteroaryl groups are pyridyl, oxazolyl, benzofuranyl, dibenzofuranyl and quinolyl.

[0018] All of the above-mentioned alkyl, alkenyl, dialkyl and alkoxy groups can be unsubstituted or mono- or poly-substituted, for example by C6-C 24 aryl, preferably phenyl (in the case of alkyl groups, this leads, for example, to aralkyl groups, preferably phenylalkyl groups), halogen, preferably fluorine, chlorine or bromine groups.

[0019] Both the aryl and the heteroaryl groups are unsubstituted or mono- or poly-substituted, for example by straight-chain or branched C1-C 30Alkyl groups, halogens, preferably fluorine, chlorine, or bromine, sulfonates (SO3Na), straight-chain or branched C1-C 30 alkoxy, preferably methoxy or ethoxy, hydroxy, NH2 or N(R")2 group, wherein R" is further a straight-chain or branched C1-C group. 30 Alkyl or C5-C 24 Aryl, or other C6-C 24 Aryl or heteroaryl substitution results in diaryl, preferably biphenyl or naphthyl, heteroarylaryl, arylheteroaryl, or diheteroaryl. These C5-C 24 The aryl or heteroaryl substituents are either unsubstituted or mono- or polysubstituted by all of the aforementioned substituents.

[0020] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 R 12 R 13 R 14 The cycloalkyl group in the group should typically be understood to refer to C3-C 20 Cycloalkyl, preferably C3-C8 cycloalkyl, more preferably cyclopentyl and cyclohexyl.

[0021] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 R 12 R 13 R 14 The cycloalkenyl groups in the group are the same or different, have a C=C double bond in the cyclic skeleton and are typically C5-C8 cycloalkenyl, preferably cyclopentenyl and cyclohexenyl.

[0022] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 R 12 R 13 R 14 The cyclodienyl groups in the group are the same or different, have two C=C double bonds in the cyclic skeleton and are typically C5-C8 cyclodienyl groups, preferably cyclopentadienyl and cyclohexadienyl groups.

[0023] The aforementioned cycloalkyl, cycloalkenyl, and cyclodienyl groups are also unsubstituted or mono- or polysubstituted, for example, by straight-chain or branched C1-C groups. 30 Alkyl groups (resulting in so-called aryl groups), halogens, preferably fluorine, chlorine, or bromine, sulfonates (SO3Na), straight-chain or branched C1-C 30 alkoxy, preferably methoxy or ethoxy, hydroxy, NH2 or NR2" group, wherein R" is further a straight-chain or branched C1-C group.30 alkyl or C5-C 24 aryl, or substituted by C5-C 24 aryl or -heteroaryl, which in turn are either unsubstituted or mono- or poly- substituted by all substituents mentioned above.

[0024] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 The halogen radicals in the R1, R2, R3, R4, R5, R6, R7, R8, R9, R

[0025] Particularly preferred R1, R2, R3groups having formula 1 are trialkyl, tricycloalkyl, triaryl, trialkylaryl, triarylalkyl, diarylmonoalkyl, diarylmonocycloalkyl, dialkylmonoaryl, dialkylmonocycloalkyl or dicycloalkylmonoaryl phosphines, wherein all the above mentioned groups in turn are either unsubstituted or mono- or poly- substituted by the above mentioned substituents.

[0026] Particularly preferred R1, R2, R3groups wherein the R' groups are identical or different and each is phenyl, cyclohexyl, cyclohexenyl, cyclopentyl, cyclopentadienyl, phenylsulfonate or cyclohexylsulfonate.

[0027] Most preferably, the phosphine having formula 1 in the compounds A of the present application is PPh3, P(p-Tol)3, P(o-Tol)3, PPh(CH з )2, P(CF3)3, P(p-FC6H4)3, P(p-CF з C6H4)3, P(C6H4-SO з Na)3, P(CH2C6H4-SO3Na)3, P(i-Pr)3, P(CHCH3(CH2CH3))3, P(Cp)3, P(Cy)3, P(Np)3, P(C6H5CH2)(C6H5)2, P(NCCH2CH2)(C6H5), P[(CH)3C]2Cl, P[(CH)3C](CH3), P(i-Bu)(biph), P(C6H 11 )2Cl, P(CH3)(OCH2CH3)2, P(CH2=CHCH2)3, P(C4H3O)3, P(CH2OH)3, P(m-CH3OC6H4)3, P(C6F5)3, P[(CH3)3Si]3, P[(CH3O)3C6H2]3, wherein Cp is cyclopentyl, Np is neopentyl, Cy is cyclohexyl, Ph is phenyl, Tol is tolyl, biph is biphenyl, Bu is butyl and Pr is propyl. Triphenylphosphine and tricyclohexylphosphine are particularly preferred.

[0028] In the diphosphines of formula 3, m is 0 or 1, preferably 1.

[0029] Within the structure of formula 3, X is a straight-chain or branched-chain alkanediyl, alkenediyl or alkynediyl group, preferably a straight-chain or branched-chain C1-C8 alkanediyl, C2-C6 alkenediyl or C2-C6 alkynediyl group. 20 alkanediyl, C2-C6 alkenediyl or C2-C6 alkynediyl group. 20 alkanediyl, C2-C6 alkenediyl or C2-C6 alkynediyl group. 20 alkanediyl, C2-C6 alkenediyl or C2-C6 alkynediyl group. 20 alkanediyl, C2-C6 alkenediyl or C2-C6 alkynediyl group.

[0030] C1-C8 alkanediyl is a straight-chain or branched-chain alkanediyl group having from 1 to 8 carbon atoms. Particularly preferred is a straight-chain or branched-chain alkanediyl group having from 1 to 6 carbon atoms, especially a straight-chain or branched-chain alkanediyl group having from 2 to 4 carbon atoms. Preferred are methylene, ethylene, propylene, propane-1,2-diyl, propane-2,2-diyl, butane-1,3-diyl, butane-2,4-diyl, pentane-2,4-diyl or 2-methylpentane-2,4-diyl.

[0031] C2-C6 alkenediyl is a straight-chain or branched-chain alkenediyl group having from 2 to 6 carbon atoms. Preferred is a straight-chain or branched-chain alkenediyl group having from 2 to 4 carbon atoms, more preferably a straight-chain or branched-chain alkenediyl group having from 2 to 3 carbon atoms. Preferred are vinylene, propenylene, prop-1-ene-1,2-diyl or but-2-ene-1,4-diyl.

[0032] C2-C6 alkynediyl is a straight-chain or branched-chain alkynediyl group having from 2 to 6 carbon atoms. Preferred is a straight-chain or branched-chain alkynediyl group having from 2 to 4 carbon atoms, more preferably a straight-chain or branched-chain alkynediyl group having from 2 to 3 carbon atoms. Preferred are ethynediyl or propynediyl.

[0033] Particularly preferred diphosphines of formula 3 are C12PCH2CH2PC12, (C6H 11 )PCH2P(C6H 11(C6H5)2PCH=CHP(C6H5)2, (C6F5)P(CH2)P(C6F5)2, (C6H5)2P(CH)2P(C6H5)2, (C6H5)2P(CH2)5P(C6H5)2, (C6H5)2P(CH2)4P(C6H5)2, (C6H5)P(CH2)4P(C6H5)2, (C6H5)2PCH(CH3)CH(CH3)P(C6H5)2, and (C6H5)PCH(CH3)CH2P(C6H5)2.

[0034] Specific diphosphines which can also be used according to the present application include (1,5-bis(diphenylphosphino)pentane, 1,4-bis(diphenylphosphino)butane, 1,3-bis(diphenylphosphino)propane, 1,2-bis(diphenylphosphino)ethane) are also disclosed in Chem. Eur. J. 2008, 14, 9491-9494.

[0035] In some specific implementations, the compound A has any one of the structures of Formula 5 to Formula 17;

[0036]

[0037] The compound A content is determined by gas chromatography.

[0038] The conductive aid includes, but is not limited to, one or more of carbon nanotubes, carbon black, carbon nanohorns, carbon fibers, graphene, carbon non-woven sheet, metal fibers or metal foil, and the present application does not have special requirements for the selection of the conductive aid; the composition of the paste for secondary batteries is carefully designed to ensure its excellent performance. Specifically, the content of the conductive aid is set to 1 to 10 parts by mass, and this proportion range can ensure that the conductive aid fully plays its conductive role in the electrode composite layer. The conductive aid, the polymer and the compound A show excellent operability within the content proportion range specified in the present application. This not only makes the preparation process of the paste for secondary batteries more smooth, but also can significantly improve the production efficiency of the electrode slurry prepared from the paste when forming the electrode composite layer. The mass fraction of the conductive aid is 1 to 10 parts, which can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts.

[0039] The carbon nanotube (CNT) used can be a single-walled CNT or a multi-walled CNT, and its form can include a bundle type and / or a tangled type. Further, the average diameter of the CNT is preferably controlled to be in a range of 0.5 nm or more and 200 nm or less. Such a diameter range contributes to uniform dispersion of the CNT in the paste and to improvement in the electrical conductivity of the electrode composite layer.

[0040] Further, the average length of the CNT is also preferably controlled to be in a range of 1 μm or more and 1000 μm or less. An appropriate length ensures that the CNT forms an effective conductive network in the electrode composite layer, thereby improving the electrochemical performance of the battery.

[0041] To accurately measure the average diameter and the average length of the CNT, the CNT can be observed using a transmission electron microscope (TEM). Specifically, 50 CNTs are randomly selected from the obtained TEM image, and the diameter (outer diameter) and the length of each of the CNTs are measured, and then the arithmetic mean of the measured values is calculated as the average diameter and the average length of the CNT.

[0042] In addition to the carbon nanotube (CNT), other known conductive aids that can be incorporated in the electrode of the secondary battery can also be used. These conductive aids include, but are not limited to, carbon black (e.g., acetylene black, Ketjen black (registered trademark), furnace black, etc.), carbon nanohorn, vapor-grown carbon fiber, milled carbon fiber obtained by pulverizing a polymer fiber after sintering, single-layer or multi-layer graphene, and carbon nonwoven sheet obtained by sintering a nonwoven fabric composed of a polymer fiber, and the like. In addition, fibers or foils of various metals, and the like can also be used as the conductive aid. In actual use, one of these conductive aids can be used alone, or two or more of them can be used in combination to adjust the performance of the electrode according to the specific needs.

[0043] When the above other conductive aids are used in combination with the CNT, a conductive path can be more favorably formed in the electrode composite layer obtained from the paste, thereby improving the electrical conductivity and further reducing the internal resistance of the secondary battery. This combined use contributes to optimization of the structure and the performance of the electrode, satisfying the high demand for the electrical conductivity of the high-performance secondary battery.

[0044] In the preparation of the paste for the secondary battery, the content ratio of the conductive aid is an important parameter. With the mass of the paste for the secondary battery as 100 parts by mass, the content ratio of the conductive aid is preferably controlled to be 1 part by mass or more, more preferably 2 parts by mass or more, and further preferably 3 parts by mass or more, and at the same time, the upper limit thereof is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, further preferably 5 parts by mass or less, and particularly preferably 4 parts by mass or less.

[0045] When the content ratio of the conductive aid is 1 part by mass or more, the solid content concentration of the slurry for electrode prepared using the paste can be effectively increased, and thus the productivity of the electrode composite layer formed from the slurry for electrode can be improved. On the other hand, if the content ratio of the conductive aid is controlled to be 10 parts by mass or less, the viscosity of the paste can be prevented from excessively increasing, and thus the convenience of the operability can be sufficiently ensured.

[0046] The content ratio of the carbon nanotube (CNT) in the paste for secondary battery is preferably the same as the content ratio of the conductive aid, that is, 1 part by mass or more, more preferably 2 parts by mass or more, and further preferably 3 parts by mass or more, and the upper limit is 10 parts by mass or less, more preferably 8 parts by mass or less, further preferably 5 parts by mass or less, and particularly preferably 4 parts by mass or less, based on 100 parts by mass of the paste for secondary battery.

[0047] When the content ratio of the CNT is 1 part by mass or more, the solid content concentration of the slurry for electrode can be increased, and thus the productivity of the electrode composite layer can be improved. If the content ratio is controlled to be 10 parts by mass or less, the viscosity of the paste can be kept moderate, and thus the operability can be facilitated. Such content setting is helpful to sufficiently exhibit the conductivity of the CNT while maintaining the good processability of the paste.

[0048] The polymer includes an alkylene structural unit and a nitrile group monomer unit, and includes 10 parts by mass to 50 parts by mass of the nitrile group monomer unit and 15 parts by mass to 85 parts by mass of a conjugated diene monomer unit. If the polymer has the above composition, the internal resistance of the secondary battery can be further reduced, and the cycle characteristics can be improved. In addition, the "monomer unit" of the polymer means "a structural unit derived from a monomer in a polymer obtained using the monomer". Furthermore, in the present application, the structure and content of each monomer unit in the polymer can be determined by infrared spectroscopy and 1 H-NMR, and the like. The parts by mass of the polymer is 0.02 parts to 1 part, and can be 0.02 parts, 0.03 parts, 0.05 parts, 0.07 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 0.95 parts, or 1 part.

[0049] The dispersion medium includes, but is not limited to, a small molecule compound having a pyrrolidone ring skeleton and an N-methyl substituent. There is no particular limitation on the selection of the dispersion medium, but a polar organic solvent capable of dissolving the aforementioned polymer is preferably used. Specifically, the dispersion medium includes, but is not limited to, one or more of acetonitrile, N-methylpyrrolidone, cyclopentanone, N,N-dimethylacetamide, dimethylformamide, dimethyl sulfoxide, methylformamide, methyl ethyl ketone, or furfural. After comprehensively considering factors such as operation convenience and safety, N-methylpyrrolidone is regarded as a preferred choice. In addition, the dispersion medium can be used alone or in combination of two or more as needed. The mass fraction of the dispersion medium is 88 parts to 98 parts, and can be 88 parts, 89 parts, 90 parts, 91 parts, 92 parts, 93 parts, 94 parts, 95 parts, 96 parts, 97 parts, or 98 parts.

[0050] The polymer includes hydrogenated nitrile rubber; the polymer includes 10 mass parts to 50 mass parts of a nitrile monomer unit, 15 mass parts to 85 mass parts of a conjugated diene monomer unit;

[0051] The hydrogenation degree of the conjugated diene monomer unit in the polymer is 90% to 100%.

[0052] In the paste for secondary batteries of the present application, the polymer used needs to have the function of effectively dispersing the conductive auxiliary agent in the dispersion medium, i.e., used as a dispersing material, and there is no particular limitation on such a polymer. In addition, when an electrode composite material layer is prepared on a current collector by using the paste for secondary batteries, the polymer can also function as a binding material to ensure that each component in the electrode composite material layer does not fall off.

[0053] Specifically, the polymer that can be used includes, but is not limited to, acrylic rubber (ACM), polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), nitrile rubber (NBR), and hydrogenated nitrile rubber (HNBR). These polymers can be used alone or in combination of two or more as needed.

[0054] Among the above-mentioned polymers, in view of improving the stability of the paste, reducing the internal resistance of the secondary battery, and enhancing the cycle characteristics, polyvinylpyrrolidone, polyvinylidene fluoride, nitrile rubber, and hydrogenated nitrile rubber are preferred, nitrile rubber and hydrogenated nitrile rubber are more preferred, and hydrogenated nitrile rubber is further preferred.

[0055] The "hydrogenation degree" can be determined according to the method described in SH / T 1762-2008. The hydrogenation degree of the conjugated diene in the polymer is preferably 90-100%, more preferably 95-100%, and further preferably 99-100%.

[0056] The polymer preferably contains at least one selected from a nitrile group-containing monomer unit and a conjugated diene monomer unit. More preferably, the polymer contains both a nitrile group-containing monomer unit and a conjugated diene monomer unit. In addition, the polymer can contain other structural units in addition to the nitrile group-containing monomer unit and the conjugated diene monomer unit.

[0057] Nitrile group-containing monomer unit: As the nitrile group-containing monomer that can form the nitrile group-containing monomer unit, an α,β-ethylenically unsaturated nitrile monomer is included. Specifically, there is no particular limitation on the selection of the α,β-ethylenically unsaturated nitrile monomer, as long as it is an α,β-ethylenically unsaturated compound having a nitrile group. For example, acrylonitrile, methacrylonitrile, and α-alkyl acrylonitrile (such as α-ethyl acrylonitrile, etc.) can be used. These monomers can be used alone or two or more of them can be used in combination. Of these, acrylonitrile is preferred. When the total structural units in the polymer are taken as 100 parts by mass, the proportion of the nitrile group-containing monomer unit in the total structural units contained in the polymer is preferably set to 10 parts by mass or more, more preferably 13 parts by mass or more, and further preferably 18 parts by mass or more; and at the same time, it is preferably set to 50 parts by mass or less, more preferably 40 parts by mass or less, and further preferably 36 parts by mass or less.

[0058] If the proportion of the nitrile group-containing monomer unit in the total structural units is 10 parts by mass or more, the polymer can be well dissolved in a dispersion medium such as N-methylpyrrolidone, thereby improving the dispersing ability of the polymer. As a result, the conductive aid can be well dispersed, and the stability of the paste can be improved. Further, an electrode composite layer in which the conductive aid is uniformly dispersed can be formed, and the internal resistance of the secondary battery can be further reduced. On the other hand, if the proportion of the nitrile group-containing monomer unit in the total structural units is controlled to 40 parts by mass or less, the excessive swelling of the polymer caused by the electrolyte solution can be effectively suppressed, and the cycle characteristics of the secondary battery can be further improved.

[0059] The conjugated diene monomer unit includes one or more of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, or 1,3-pentadiene. These monomers can be used alone or two or more of them can be used in combination.

[0060] In the present application, the so-called "conjugated diene monomer unit" also includes a structural unit obtained by further hydrogenation treatment of a monomer unit in a polymer obtained from a conjugated diene monomer (i.e., a hydrogenated product monomer unit).

[0061] Of the above-mentioned conjugated diene monomers, 1,3-butadiene and isoprene are preferred. In other words, as the conjugated diene monomer unit, a 1,3-butadiene unit, an isoprene unit, a 1,3-butadiene hydrogenated product unit, and an isoprene hydrogenated product unit are preferred.

[0062] Here, the proportion of the conjugated diene monomer unit in the polymer, based on 100 parts by mass of the total structural units, is preferably 15 parts by mass or more, more preferably 20 parts by mass or more, further preferably 25 parts by mass or more, and particularly preferably 30 parts by mass or more. Meanwhile, it is preferably 85 parts by mass or less, and more preferably 70 parts by mass or less. When the proportion of the conjugated diene monomer unit in the total structural units is 15 parts by mass or more, the electrode formed from the electrode slurry containing the polymer can have sufficient flexibility. When the proportion is 70 parts by mass or less, the polymer can be well dissolved in a dispersion medium such as N-methylpyrrolidone, thereby improving the dispersing ability of the polymer. Thus, the conductive aid can be well dispersed, and the stability of the paste can be improved. Furthermore, when the proportion of the conjugated diene monomer unit in the total structural units is between 15 parts by mass and 70 parts by mass, the internal resistance of the secondary battery can be further reduced, and the cycle characteristics can be significantly improved.

[0063] The other structural units are not particularly limited and include structural units derived from known monomers that can be copolymerized with the above-described nitrile group-containing monomer and the conjugated diene monomer. Specifically, as the other structural units, there are no particular limitations, and monomer units such as a hydrophilic group-containing monomer unit, an aromatic vinyl monomer unit, and a (meth)acrylate monomer unit can be preferably cited.

[0064] As the hydrophilic group-containing monomer that can form the hydrophilic group-containing monomer unit, a polymerizable monomer having a hydrophilic group is included. Specifically, as the hydrophilic group-containing monomer, monomers having a carboxylic acid group, monomers having a sulfonic acid group, monomers having a phosphoric acid group, and monomers having a hydroxyl group are included.

[0065] As the monomer having a carboxylic acid group, a monocarboxylic acid and a derivative thereof, a dicarboxylic acid and an anhydride thereof, and the like are included.

[0066] As the monocarboxylic acid, one or more of acrylic acid, methacrylic acid, or crotonic acid is included.

[0067] As the monocarboxylic acid derivative, one or more of 2-ethylacrylic acid, isocrotonic acid, α-acetyloxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, or β-diaminoacrylic acid is included.

[0068] As the dicarboxylic acid, one or more of maleic acid, fumaric acid, or itaconic acid can be cited.

[0069] As the dicarboxylic acid derivative, one or more of methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, maleic acid methallyl ester, maleic acid diphenyl ester, maleic acid nonyl ester, maleic acid decyl ester, maleic acid dodecyl ester, maleic acid stearyl ester, or maleic acid fluoralkyl ester is included.

[0070] As the anhydride of dicarboxylic acid, one or more of maleic anhydride, acrylic anhydride, methyl maleic anhydride, or dimethyl maleic anhydride is included.

[0071] Further, as the monomer having a carboxylic acid group, an anhydride that generates a carboxylic acid group by hydrolysis can also be used.

[0072] In addition, monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, diethyl itaconate, monobutyl itaconate, dibutyl itaconate, and the like of monoesters and diesters of α,β-ethylenically unsaturated polycarboxylic acids can also be included.

[0073] As the monomer having a sulfonic acid group, vinyl sulfonic acid, methyl vinyl sulfonic acid, (methyl)allyl sulfonic acid, styrene sulfonic acid, (methyl)acrylic acid-2-sulfonic acid ethyl ester, 2-acrylamido-2-methylpropane sulfonic acid, 3-allyloxy-2-hydroxypropane sulfonic acid, and the like are included. In addition, in the present application, "(methyl)acrylic acid" is acrylic acid and / or methacrylic acid. Further, "(methyl)allyl" means allyl and / or methallyl.

[0074] As the monomer having a phosphoric acid group, one or more of phosphoric acid-2-(methyl)acryloyloxyethyl ester, phosphoric acid methyl-2-(methyl)acryloyloxyethyl ester, or phosphoric acid ethyl-(methyl)acryloyloxyethyl ester is included. In addition, "(methyl)acryloyl" means acryloyl and / or methacryloyl.

[0075] As the monomer having a hydroxyl group, ethylenically unsaturated alcohols such as (methyl)allyl alcohol, 3-buten-1-ol, 5-hexen-1-ol; alkyl esters of ethylenically unsaturated carboxylic acids such as acrylic acid-2-hydroxyethyl ester, acrylic acid-2-hydroxypropyl ester, methacrylic acid-2-hydroxyethyl ester, methacrylic acid-2-hydroxypropyl ester, maleic acid di-2-hydroxyethyl ester, maleic acid di-4-hydroxybutyl ester, itaconic acid di-2-hydroxypropyl ester; and the like of general formula: CH2=CR1-COO-(C q H 2q O) p-H (in the formula, p represents an integer of 2 to 9, q represents an integer of 2 to 4, and R1represents a hydrogen atom or a methyl group) ; mono(meth)acrylates of dihydroxy esters of dicarboxylic acids such as 2-hydroxyethyl-2'-(meth)acryloyloxy phthalate, 2-hydroxyethyl-2'-(meth)acryloyloxy succinate, and the like; vinyl ethers such as 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, and the like; mono(meth)allyl ethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl ether, (meth)allyl-2-hydroxypropyl ether, (meth)allyl-3-hydroxypropyl ether, (meth)allyl-2-hydroxybutyl ether, (meth)allyl-3-hydroxybutyl ether, (meth)allyl-4-hydroxybutyl ether, (meth)allyl-6-hydroxyhexyl ether, and the like; polyoxyalkylene glycol mono(meth)allyl ethers such as diethylene glycol mono(meth)allyl ether, dipropylene glycol mono(meth)allyl ether, and the like; mono(meth)allyl ethers of (poly)alkylene glycols such as glycerol mono(meth)allyl ether, (meth)allyl-2-chloro-3-hydroxypropyl ether, (meth)allyl-2-hydroxy-3-chloropropyl ether, and the like; mono(meth)allyl ethers of polyhydric phenols such as eugenol, isoeugenol, and the like, and halogen-substituted and hydroxy-substituted products thereof; (meth)allyl thioethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl thioether, (meth)allyl-2-hydroxypropyl thioether, and the like; and the like.

[0076] These hydrophilic group-containing monomers can be used alone or in combination of two or more. Among these, from the viewpoint of improving the adhesion of the electrode composite layer and further reducing the internal resistance of the secondary battery, a monomer having a carboxylic acid group is preferred, and acrylic acid or methacrylic acid is more preferred.

[0077] As the aromatic vinyl monomer that can form an aromatic vinyl monomer unit, styrene, styrene sulfonic acid and salts thereof, α-methylstyrene, butoxystyrene, and vinyl naphthalene, and the like are included. These can be used alone or in combination of two or more. Among these, styrene is preferred.

[0078] As the (meth)acrylate monomer that can form a (meth)acrylate monomer unit, one or more of (meth)acrylic acid alkyl esters, (meth)acrylic acid perfluoroalkyl esters, or polyethylene glycol-based acrylates are included.

[0079] As the (meth)acrylic acid alkyl ester, there are included methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate, and the like alkyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, glycidyl methacrylate, and the like alkyl methacrylate.

[0080] As the (meth)acrylic acid perfluoroalkyl ester, there are included 2-(perfluorobutyl)ethyl acrylate, 2-(perfluoropentyl)ethyl acrylate, 2-(perfluorohexyl)ethyl acrylate, 2-(perfluorooctyl)ethyl acrylate, 2-(perfluorononyl)ethyl acrylate, 2-(perfluorodecyl)ethyl acrylate, 2-(perfluorododecyl)ethyl acrylate, 2-(perfluorotetradecyl)ethyl acrylate, 2-(perfluorohexadecyl)ethyl acrylate, and the like 2-(perfluoroalkyl)ethyl acrylate; 2-(perfluorobutyl)ethyl methacrylate, 2-(perfluoropentyl)ethyl methacrylate, 2-(perfluorohexyl)ethyl methacrylate, 2-(perfluorooctyl)ethyl methacrylate, 2-(perfluorononyl)ethyl methacrylate, 2-(perfluorodecyl)ethyl methacrylate, 2-(perfluorododecyl)ethyl methacrylate, 2-(perfluorotetradecyl)ethyl methacrylate, 2-(perfluorohexadecyl)ethyl methacrylate, and the like 2-(perfluoroalkyl)ethyl methacrylate, and the like.

[0081] As the polyethylene glycol-based acrylate, there are included polyethylene glycol acrylate, polyethylene glycol methacrylate, methoxypolyethylene glycol acrylate, methoxypolyethylene glycol methacrylate, ethoxypolyethylene glycol acrylate, ethoxypolyethylene glycol methacrylate, butoxypolyethylene glycol acrylate, butoxypolyethylene glycol methacrylate, ethylhexyloxypolyethylene glycol acrylate, ethylhexyloxypolyethylene glycol methacrylate, and the like, the number of repeating units being 1, 2, 3, 4, 5, 6, 7, or 8, preferably 2, 3, 4, 5, 6, 7, or 8, more preferably 3, 4, 5, 6, 7, or 8, and most preferably 3.

[0082] The method of preparing the polymer is not particularly limited, and the polymer can be prepared, for example, by polymerizing a monomer composition containing the above-described monomers, and optionally performing hydrogenation.

[0083] Here, the content ratio of each monomer in the monomer composition can be determined according to the content ratio of each monomer unit in the polymer.

[0084] The polymerization method is not particularly limited, and any one of a solution polymerization method, a suspension polymerization method, a bulk polymerization method, an emulsion polymerization method, and the like can be used. In each polymerization method, a known emulsifier, a polymerization initiator can be used as needed. The method including hydrogenation is not particularly limited, and a general method using a catalyst (for example, refer to US5057581, CN 104271607B, EP-A-0134023, and JP2015 / 086268) can be used.

[0085] Content ratio of the polymer: In some specific embodiments, the content ratio of the polymer in the paste for secondary batteries is strictly controlled as a percentage by mass with respect to the entire paste. Specifically, when the mass of the entire paste is 100 parts by mass, the ratio is preferably not less than 0.02 parts by mass to ensure that the conductive aid can be well dispersed, thereby improving the stability of the paste; more preferably, the ratio is not less than 0.06 parts by mass; further preferably, not less than 0.08 parts by mass; particularly preferably, the ratio should be not less than 0.14 parts by mass. At the same time, in order to sufficiently reduce the internal resistance of the secondary battery, the content ratio of the polymer is preferably not more than 1 part by mass; more preferably, not more than 0.5 parts by mass; further preferably, not more than 0.4 parts by mass. In summary, the content ratio of the polymer in the paste for secondary batteries is preferably between 0.02 parts by mass and 1 part by mass, more preferably between 0.06 parts by mass and 0.5 parts by mass, further preferably between 0.08 parts by mass and 0.4 parts by mass, and particularly preferably not less than 0.14 parts by mass and not more than the upper limit value.

[0086] As other ingredients, the paste for secondary batteries can also contain other various auxiliary ingredients. For example, a viscosity modifier, a reinforcing material, an antioxidant, a surfactant, and an electrolyte additive having a function of inhibiting decomposition of the electrolyte, and the like can be used in combination. These auxiliary ingredients can be selected from the types known in the art. In actual applications, these other ingredients can be used alone or in combination of two or more according to specific needs to achieve the best formulation effect. In addition, it should be particularly pointed out that the paste for secondary batteries of the present application does not generally contain an electrode active material, i.e., a positive electrode active material or a negative electrode active material.

[0087] The present application also provides a method for preparing a paste for secondary batteries, comprising:

[0088] The conductive aid, the polymer, the dispersion medium, and the compound A are mixed to obtain a paste for a secondary battery.

[0089] The paste for a secondary battery can be obtained by a specific preparation method. The preparation method can further include the following steps: a process of subjecting the raw material CNT to acid treatment (acid treatment process); a process of subjecting the raw material CNT subjected to acid treatment to alkali treatment (alkali treatment process); a process of washing the raw material CNT subjected to alkali treatment to obtain CNT having a predetermined property (surface-treated CNT) (washing process); and a process of mixing the conductive aid including the surface-treated CNT with the polymer and the dispersion medium (mixing process). The manufacturing method of the paste for a secondary battery according to the present application can efficiently manufacture the paste for a secondary battery containing carbon nanotubes.

[0090] The CNT is mixed with the polymer, the dispersion medium, the compound A, and other conductive aids and / or other components as needed. The present application does not make a specific limitation on the specific mixing method in the mixing process. In actual operation, a common mixing device such as a disperser, a mill, a kneader, etc. can be used to complete this process. These mixing devices can effectively mix various raw materials uniformly, thereby ensuring that the finally manufactured paste for a secondary battery has excellent performance.

[0091] The present application also provides a slurry for a positive electrode of a secondary battery, which includes 90 to 99 parts by mass of a positive electrode active material and 1 to 10 parts by mass of the paste for a secondary battery as described above or the paste for a secondary battery manufactured according to the above-described preparation method.

[0092] In some specific embodiments, the positive electrode active material includes, but is not limited to, one or more of lithium-containing cobalt oxide, lithium manganate, lithium-containing nickel oxide, lithium-containing composite oxide of Co-Ni-Mn, lithium-containing composite oxide of Ni-Mn-Al, lithium-containing composite oxide of Ni-Co-Al, olivine-type lithium iron phosphate, olivine-type lithium manganese phosphate, olivine-type lithium manganese iron phosphate, Li2MnO3-LiNiO2 solid solution, lithium-excess spinel compound, Li[Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 ]O2 or LiNi 0.5 Mn 1.5 O4, and the present application does not make a specific requirement on the positive electrode active material.

[0093] The present application also provides a positive electrode for a secondary battery, which is obtained by coating the above-described slurry for a positive electrode of a secondary battery on the surface of a current collector and drying the same.

[0094] The positive electrode of the positive electrode composite layer formed of the slurry for a positive electrode of a secondary battery can reduce the internal resistance of the secondary battery and make the secondary battery exhibit excellent cycle characteristics. Furthermore, in order to favorably solve the above-described problems, the positive electrode for a secondary battery of the present application has a positive electrode composite layer formed of any one of the above-described slurry for a positive electrode of a secondary battery. According to the positive electrode having a positive electrode composite layer formed of any one of the above-described slurry for a positive electrode, the internal resistance of the secondary battery can be reduced. Moreover, in order to favorably solve the above-described problems, the secondary battery of the present application is characterized by having the above-described positive electrode for a secondary battery. The internal resistance of the secondary battery having the above-described positive electrode is reduced.

[0095] Here, the positive electrode active material is a substance that performs electron transfer in the positive electrode of a secondary battery. Moreover, for example, in the case where the secondary battery is a lithium ion secondary battery, as the positive electrode active material, a substance that can absorb and release lithium ions is generally used.

[0096] In addition, the following is described taking the case where the slurry for a positive electrode of a secondary battery is a slurry for a positive electrode of a lithium ion secondary battery as an example, but the present application is not limited to the following example.

[0097] Moreover, as the positive electrode active material for a lithium ion secondary battery, there is no particular limitation, and examples include lithium cobalt oxide (LiCoO2), lithium manganate (LiMn2O4), lithium nickel oxide (LiNiO2), lithium-containing composite oxides of Co-Ni-Mn (for example, Li[Co α Mn β Ni γ ]O2, α+β+γ=1), lithium-containing composite oxides of Ni-Mn-Al, lithium-containing composite oxides of Ni-Co-Al, olivine-type lithium iron phosphate (LiFePO4), olivine-type lithium manganese phosphate (LiMnPO4), olivine-type lithium manganese iron phosphate (LiMn x Fe 1-x PO4) (0X<1), Li2MnO3-LiNiO2-based solid solutions, Li 1+x Mn 2-x O4 (0X<2) indicating a lithium-excess spinel compound, Li[Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 ]O2, LiNi 0.5 Mn 1.5 O4, and the like, which are known positive electrode active materials.

[0098] In addition, the particle diameter of the positive electrode active material is not particularly limited and can be the same as that of a conventional positive electrode active material. Furthermore, the positive electrode active material can be used alone or in combination with two or more kinds.

[0099] Moreover, the proportion of the positive electrode active material contained in the slurry for a positive electrode of a secondary battery is not particularly limited, and is preferably 90 to 99 parts when the total solid content in the slurry for a positive electrode of a secondary battery is taken as 100 parts by mass.

[0100] The slurry for a positive electrode of a secondary battery of the present application can be prepared by mixing the above-mentioned positive electrode active material and the above-mentioned paste for a secondary battery. The method of mixing is not particularly limited, and a general mixing device such as a disperser, a mill, a kneader, or the like can be used.

[0101] The positive electrode for a secondary battery of the present application has a positive electrode composite layer formed using the above-mentioned slurry for a positive electrode of a secondary battery.

[0102] For example, the positive electrode for a secondary battery of the present application can be formed by applying the above-mentioned slurry for a positive electrode of a secondary battery to the surface of a current collector to form a coating film, and then drying the formed coating film. The positive electrode for a secondary battery has a positive electrode composite layer formed from the dried product of the above-mentioned slurry for a positive electrode of a secondary battery, and generally contains a positive electrode active material, CNT, and a polymer, and optionally contains other conductive aids and / or other components. In addition, each component contained in the positive electrode composite layer is a component contained in the above-mentioned slurry for a positive electrode, and the proportion of each component is generally the same as the proportion in the above-mentioned slurry for a positive electrode of a secondary battery.

[0103] Moreover, the positive electrode for a secondary battery of the present application has a positive electrode composite layer formed from the above-mentioned slurry for a positive electrode, and therefore, by using the positive electrode of the present application, the internal resistance of a secondary battery can be reduced and the secondary battery can exhibit excellent cycle characteristics.

[0104] The method of producing a positive electrode for a secondary battery includes, in one preferred embodiment, the positive electrode for a secondary battery of the present application can be produced by the following steps of: first, applying the above-mentioned slurry for a positive electrode of a secondary battery to a current collector (coating step); and then, drying the slurry for a positive electrode of a secondary battery applied to the current collector to form a positive electrode composite layer on the current collector (drying step).

[0105] Coating step: As the method of applying the above-mentioned slurry for a positive electrode to a current collector, there is no particular limitation, and a known method can be used. Specifically, as the method of application, a doctor blade method, a dip method, a reverse roll coating method, a direct roll coating method, a gravure method, a squeeze method, a brush coating method, or the like can be used. At this time, the slurry can be applied to only one side of the current collector, or the slurry can be applied to both sides. The thickness of the slurry film on the current collector after application and before drying can be appropriately set according to the thickness of the positive electrode composite layer obtained by drying.

[0106] Here, as the current collector to be coated with the positive electrode slurry, a material having conductivity and electrochemical durability can be used. Specifically, as the current collector, a current collector composed of, for example, iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, or the like can be used. In addition, the above-described materials can be used singly or in combination of two or more in any ratio.

[0107] Drying step: As a method for drying the positive electrode slurry on the current collector, there is no particular limitation, and known methods can be used, and drying methods using warm air, hot air, low-humidity air, vacuum drying methods, drying methods using irradiation of infrared rays, electron rays, or the like can be cited. By drying the slurry on the current collector as such, a positive electrode composite material layer can be formed on the current collector, and a positive electrode having a current collector and a positive electrode composite material layer can be obtained.

[0108] In addition, after the drying step, the positive electrode composite material layer can be subjected to a pressurization treatment using a mold press or a roll press, or the like. By the pressurization treatment, the adhesion of the positive electrode composite material layer to the current collector can be improved. Furthermore, in the case where the positive electrode composite material layer contains a polymer having curability, it is preferable to cure the above-described polymer after the formation of the positive electrode composite material layer.

[0109] The present application also provides a secondary battery including the above-described positive electrode for secondary battery.

[0110] The secondary battery of the present application has the above-described positive electrode for secondary battery of the present application. More specifically, the secondary battery of the present application generally has a positive electrode, a negative electrode, an electrolyte, and a separator, and the positive electrode is the above-described positive electrode for secondary battery.

[0111] Furthermore, the secondary battery of the present application has a reduced internal resistance and excellent cycle characteristics because the above-described positive electrode of the present application is used.

[0112] Negative electrode: As the negative electrode for secondary battery which can be used in the secondary battery of the present application, there is no particular limitation, and known negative electrodes used in the production of secondary batteries can be used. For example, such a negative electrode can be a negative electrode formed by forming a negative electrode composite material layer on a current collector by a known production method, or the like.

[0113] Electrolyte: As the electrolyte, an organic electrolyte in which a supporting electrolyte is dissolved in an organic solvent can be generally used. For example, as the supporting electrolyte of a lithium ion secondary battery, a lithium salt can be used. As the lithium salt, for example, LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, C4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, (C2F5SO2)NLi, and the like can be exemplified. Among them, LiPF6, LiClO4, CF3SO3Li are preferred because of high dissociation degree due to easy solubility in a solvent, and LiPF6is particularly preferred. In addition, the electrolyte can be used singly or in combination of two or more kinds in any ratio. Generally, there is a tendency that the higher the dissociation degree of the supporting electrolyte, the higher the lithium ion conductivity, and thus the lithium ion conductivity can be adjusted depending on the kind of the supporting electrolyte.

[0114] As the organic solvent used in the electrolyte, there is no particular limitation as long as it can dissolve the supporting electrolyte, and for example, carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and ethyl methyl carbonate (EMC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; and the like can be preferably used. In addition, a mixed solution of these solvents can be used. Among them, carbonates are preferred because of high dielectric constant and wide stable potential region. In addition, the concentration of the electrolyte in the electrolyte can be appropriately adjusted. Furthermore, a known additive can be added to the electrolyte.

[0115] Separator: As the separator, there is no particular limitation. Among them, from the viewpoint that the film thickness of the entire separator can be made thin, and thus the capacity per unit volume can be improved by increasing the ratio of the electrode active material in the secondary battery, a microporous film composed of a polyolefin-based (polyethylene, polypropylene, polybutene, polyvinyl chloride) resin, a PVDF film, and a nanofibril film are preferred, and the surface of the above film can be coated with inorganic or organic matter.

[0116] Further, the secondary battery can be produced by, for example, superimposing the positive electrode and the negative electrode with a separator interposed therebetween, winding, folding, or the like, as needed, in accordance with the shape of the battery, placing them in a battery container, injecting an electrolyte into the battery container, and sealing. In the electrochemical element of the present application, the above-described positive electrode for electrochemical element is used. In addition, in the electrochemical element of the present application, in order to prevent an increase in internal pressure of the secondary battery, overcharge and discharge, and the like, a fuse, a PTC element, a porous metal mesh, a guide plate, or the like can be provided as needed. The shape of the secondary battery can be, for example, any one of a coin type, a button type, a sheet type, a cylindrical type, a square type, and a flat type.

[0117] The present application can significantly enhance the transport efficiency of lithium ions by adding a specific compound A to a paste for secondary battery, and can reduce the internal resistance of a secondary battery and improve the cycle characteristics of the battery by applying the paste for secondary battery to the secondary battery. DETAILED DESCRIPTION

[0118] It should be understood that the expression "one or more of" includes each of the objects recited after the expression and various combinations of two or more of the recited objects, individually, unless otherwise understood from the context and usage. The expression "and / or" in connection with three or more recited objects should be understood to have the same meaning, unless otherwise understood from the context.

[0119] Further, the numerical ranges and parameters given in the description of the application are approximate values, and the relevant values in the specific examples have been presented as precisely as possible. However, any numerical value inherently contains a standard deviation due to the individual test method. Therefore, unless otherwise explicitly stated, all ranges, numbers, values and percentages used in the present disclosure are modified by "about". Here, "about" generally means within plus or minus 10%, 5%, 1% or 0.5% of a particular value or range.

[0120] The present application provides a paste for secondary battery, comprising, in mass parts: 1 to 10 parts of a conductive aid, 0.02 to 1 part of a polymer, 88 to 98 parts of a dispersion medium, and 0.0001 to 1 part of a compound A;

[0121] The compound A has one or more of the structures of Formula 1 to Formula 4;

[0122]

[0123] wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R14 Each of the following is independently an alkyl group from C1 to C30, an alkenyl group from C2 to C30, a dienyl group from C4 to C30, an alkoxy group from C1 to C20, a cycloalkyl group from C5 to C24, an aryl group from C6 to C24, a cycloalkenyl group from C3 to C10, a cyclodienyl group, a halogen-substituted aryl group, a halogen-substituted alkyl group, or a trimethylsilyl group.

[0124] This application demonstrates that by adding a specific compound A to a secondary battery paste, the lithium-ion transport efficiency can be significantly enhanced. Applying the secondary battery paste to secondary batteries can reduce the internal resistance of the secondary batteries and improve their cycle characteristics.

[0125] The present application is further illustrated below with reference to embodiments. The scope of protection of the present application is not limited to the following embodiments.

[0126] Example 1

[0127] This embodiment provides a paste for secondary batteries, a slurry for the positive electrode of secondary batteries, a positive electrode for secondary batteries, and a secondary battery.

[0128] Preparation of the hydrogenation catalyst RuHCl(CO)(IMes)(PPh3): The catalyst was prepared according to the method described by Fogg et al. (Organometallics 2005, 24, 1056-1058) via the reaction of RuHCl(CO)(PPh3)3 (purchased from Alfar Aesar) with IMes as follows: A solution of IMes (188 mg, 0.62 mmol) in 8 mL toluene was added to a suspension of RuHCl(CO)(PPh3)3 (420 mg, 0.44 mmol) in 8 mL toluene. The solution was stirred at 22 °C for 3 h. The solution was then concentrated to approximately 0.5 mL under vacuum, treated with 20 mL of hexane, and cooled to -35 °C using a cold ethanol bath. A yellow-orange microcrystalline precipitate was obtained, which was filtered off, washed three times with 5 mL of cold hexane, and dried under vacuum. The yield obtained was approximately 0.25 g (77%) in the form of orange crystals with a single FTIR peak (CO) at 1913 cm⁻¹ (reference, 1913 cm⁻¹, in Nujol, Fogg et al., Organometallics 2005, 24, 1056-1058).

[0129] Preparation of the polymer: In a reaction vessel with a content of 1 L, 100 parts of ion exchange water, and 36 parts of acrylonitrile, 64 parts of 1,3-butadiene as monomers, 2.9 parts of sodium dodecylbenzenesulfonate as an emulsifier, 0.35 parts of potassium chloride as a stabilizer, and 0.5 parts of tertiary dodecyl mercaptan (TDDM) as a molecular weight regulator were added, and emulsion polymerization was performed at 5-10°C in the presence of 0.24 parts of cumene hydroperoxide as a polymerization initiator to copolymerize the above monomers.

[0130] At the time when the polymerization conversion rate reached 70-80%, 0.5 parts of hydroxylamine sulfate per 100 parts of monomers were added to stop the polymerization. Subsequently, heating was performed, and water vapor distillation was performed at about 70°C under reduced pressure to recover the residual monomers, and then 2 parts of alkylated phenol as an anti-aging agent were added to obtain a water dispersion of the polymer.

[0131] The water dispersion of the polymer was flocculated using ethanol, and the obtained solid rubber was dried.

[0132] The dried solid rubber was cut and used to prepare an NBR chlorobenzene solution having a solid content of 9% using chlorobenzene.

[0133] Hydrogenation: In a high-pressure reaction vessel with a content of 1 L, a butyl nitrile rubber (NBR) chlorobenzene solution having a solid content of 9% was added, and 0.06 phr of a catalyst was added per 100 parts of NBR, 9 MPa of hydrogen gas, 800 rpm of stirring, 138°C of reaction for 5 h, and the hydrogenation degree reached 99%.

[0134] The detailed hydrogenation procedure is as follows:

[0135] (1) The solution was charged into a 1 L autoclave and sparged with nitrogen for 20 minutes to remove dissolved oxygen.

[0136] (2) The catalyst was dissolved in a sufficient amount of deaerated chlorobenzene (MCB) under nitrogen protection.

[0137] (3) After heating the autoclave to the desired temperature, the catalyst solution was rapidly introduced into the autoclave by applying hydrogen pressure. Then, the hydrogen pressure was increased to the desired value.

[0138] (4) Samples were taken at intervals for FT-IR testing to monitor the hydrogenation degree.

[0139] (5) After completing the hydrogenation of NBR, the solution was cooled and the pressure was released.

[0140] (6) The polymer solution was flocculated using ethanol, and the obtained solid rubber was dried.

[0141] Analysis test of the polymer: The degree of hydrogenation was measured by FT-IR: The spectra of the nitrile rubber before, during and after the hydrogenation reaction were recorded on a PerkinElmer Spectrum 100 FT-IR spectrometer. A solution of the (hydrogenated) nitrile rubber in MCB was cast onto a KBr disk and dried to form a film for testing. The degree of hydrogenation was determined by FT-IR analysis according to the SH / T 1762-2008 method.

[0142] Then, N-methylpyrrolidone to which water was added was added to the hydrogenated nitrile rubber solid as the polymer, to obtain a N-methylpyrrolidone solution of the hydrogenated nitrile rubber having a solid content concentration of 8%.

[0143] The paste for secondary batteries was prepared by adding 1 part of carbon nanotubes (CNT), 0.25 parts (solid content equivalent amount) of the N-methylpyrrolidone solution of the hydrogenated nitrile rubber obtained in the present example, and 0.002 parts of the compound A (Formula 5) to 98 parts of N-methylpyrrolidone as a dispersion medium, stirring with a disperser (3000 rpm, 60 minutes), and then mixing for 1 hour at a peripheral speed of 8 m / sec using a bead mill using zirconia beads of 1 mm in diameter, thereby manufacturing a paste for secondary batteries. In addition, the results of measurement of the paste using a rheometer (manufactured by Anton Paar, "MCR302") were a viscosity of 49000 mPa-s at a temperature of 25°C and a shear rate of 0.1 s -1 , and a value of the solid content concentration of 4.8%. The stability of the paste for secondary batteries was evaluated. The results are shown in Table 1.

[0144] Preparation of a slurry for a positive electrode of a secondary battery: 100 parts of a lithium iron phosphate-based active material having a layered structure (LiFeP04, volume average particle diameter: 1 μm) as a positive electrode active material and an appropriate amount of N-methylpyrrolidone as a dispersion medium were added to the paste for secondary batteries obtained in the present example, and stirred with a disperser (3000 rpm, 20 minutes), to prepare a slurry for a positive electrode of a secondary battery. In addition, the amount of N-methylpyrrolidone was adjusted so that the viscosity of the obtained slurry for a positive electrode at 60 rpm was in the range of 3000 to 4000 mPa-s.

[0145] Preparation of a positive electrode for a secondary battery: An aluminum foil having a thickness of 20 μm was prepared as a current collector. The slurry for a positive electrode obtained in the present example was applied to one side of the aluminum foil using a doctor blade coater so that the dry unit area weight was 20 mg / cm 2 , and dried at 90°C for 20 minutes, dried at 120°C for 20 minutes, and then heat-treated at 60°C for 10 hours, to obtain a positive electrode raw material. The positive electrode raw material was calendered using a roll press, to produce a positive electrode composite layer (density: 3.2 g / cm 3) and an aluminum foil. Then, the sheet-shaped positive electrode was cut into a width of 48.0 mm and a length of 47 cm to produce a positive electrode for a lithium-ion secondary battery.

[0146] Preparation of a slurry for a secondary battery negative electrode: A mixture of 90 parts of spherical artificial graphite (volume average particle diameter: 12 μm) as a negative electrode active material and 10 parts of SiO x (1 part of a styrene butadiene polymer as a negative electrode binder, 1 part of carboxymethyl cellulose as a thickening agent, and an appropriate amount of water as a dispersion medium) was stirred with a planetary mixer to prepare a slurry for a secondary battery negative electrode.

[0147] Preparation of a secondary battery negative electrode: Next, a copper foil having a thickness of 15 μm was prepared as a current collector. The above-obtained slurry for a secondary battery negative electrode was applied to one side of the copper foil so that the dry coating amount became 10 mg / cm 2 at 60°C for 20 minutes and at 120°C for 20 minutes. Then, the negative electrode raw material was obtained by heat treatment at 150°C for 2 hours. The negative electrode raw material was calendered using a roll press to produce a sheet-shaped negative electrode composed of a negative electrode composite material layer having a density of 1.6 g / cm 3 at 60°C for 20 minutes and at 120°C for 20 minutes. Then, the negative electrode raw material was obtained by heat treatment at 150°C for 2 hours. The negative electrode raw material was calendered using a roll press to produce a sheet-shaped negative electrode composed of a negative electrode composite material layer having a density of 1.6 g / cm

[0148] Method for preparing a secondary battery: The above-obtained positive electrode for a lithium-ion secondary battery and the negative electrode for a lithium-ion secondary battery were wound with a 20-mm-diameter core so that the electrode composite material layers faced each other with a separator (a microporous polypropylene film) having a thickness of 15 μm interposed therebetween to obtain a wound body. Then, the obtained wound body was compressed at a speed of 10 mm / sec from one direction until the thickness became 4.5 mm. In addition, the compressed wound body had a top view elliptical shape, and the ratio of the major axis to the minor axis (major axis / minor axis) was 7.7.

[0149] In addition, an electrolyte (a 1.0 M LiPF6 solution (solvent: a mixed solution in which 5 mass% of fluoroethylene carbonate was added to a mixed solvent of ethylene carbonate / methyl ethyl carbonate = 3 / 7 (mass ratio), and 2 volume% of vinyl ethylene carbonate was added as an additive)) was prepared.

[0150] Then, the compressed jelly-roll was placed in an aluminum laminate case together with 3.2 g of electrolyte solution. Then, a nickel lead was connected to a prescribed position of the negative electrode for a lithium ion secondary battery, and an aluminum lead was connected to a prescribed position of the positive electrode for a lithium ion secondary battery, and then the opening of the case was heat-sealed to obtain a lithium ion secondary battery. The lithium ion secondary battery was a pouch having a width of 35 mm, a height of 60 mm, and a thickness of 5 mm, and the nominal capacity of the battery was 700 mAh.

[0151] Example 2

[0152] This example provides a paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery, which are different from those of Example 1 in that 0.0015 parts of Compound A (Formula 5) is added when the paste for a secondary battery is prepared; the preparation method of the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as that of Example 1.

[0153] Example 3

[0154] This example provides a paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery, which are different from those of Example 1 in that 0.006 parts of Compound A (Formula 5) is added when the paste for a secondary battery is prepared; the preparation method of the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as that of Example 1.

[0155] Example 4

[0156] This example provides a paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery, which are different from those of Example 1 in that 0.002 parts of Compound A (Formula 6) is added when the paste for a secondary battery is prepared; the preparation method of the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as that of Example 1.

[0157] Example 5

[0158] This example provides a paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery, which are different from those of Example 1 in that 0.002 parts of Compound A (Formula 7) is added when the paste for a secondary battery is prepared; the preparation method of the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as that of Example 1.

[0159] Example 6

[0160] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, with the exception that 0.002 parts of compound A (formula 8) is added when preparing the paste for a secondary battery; the method of preparing the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as in Example 1.

[0161] Example 7

[0162] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, with the exception that 1 part of compound A (formula 5) is added when preparing the paste for a secondary battery; the method of preparing the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as in Example 1.

[0163] Example 8

[0164] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, with the exception that 0.0001 parts of compound A (formula 5) is added when preparing the paste for a secondary battery; the method of preparing the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as in Example 1.

[0165] Example 9

[0166] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, with the exception that 0.1 parts of compound A (formula 5) is added when preparing the paste for a secondary battery; the method of preparing the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as in Example 1.

[0167] Example 10

[0168] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, with the exception that 0.001 parts of compound A (formula 5) is added when preparing the paste for a secondary battery; the method of preparing the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as in Example 1.

[0169] Example 11

[0170] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, which differ from those of Example 1 in that, in the preparation of the polymer, 28 parts of acrylonitrile, 40 parts of 1,3-butadiene, and 32 parts of butyl acrylate are used as monomers; and the preparation methods of the paste for a secondary battery, the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery are the same as those of Example 1.

[0171] Example 12

[0172] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, which differ from those of Example 1 in that the amount of the surface-treated CNT is changed from 1 part to 1.75 parts, and the amount of the polymer is changed from 0.5 parts to 0.125 parts; and the preparation methods of the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery are the same as those of Example 1.

[0173] Example 13

[0174] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, which differ from those of Example 1 in that the amount of the surface-treated CNT is changed from 1 part to 3.75 parts, and the amount of the polymer is changed from 0.5 parts to 0.375 parts; and the preparation methods of the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery are the same as those of Example 1.

[0175] Example 14

[0176] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, which differ from those of Example 1 in that 0.002 parts of triallylphosphine (Formula 9) is added as Compound A; and the preparation methods of the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery are the same as those of Example 1.

[0177] Example 15

[0178] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, which differ from those of Example 1 in that 0.002 parts of tris(2-furyl)phosphine (Formula 10) is added as Compound A; and the preparation methods of the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery are the same as those of Example 1.

[0179] Example 16

[0180] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, with the exception that 0.002 parts of trimethyl phosphite (Formula 11) is added as the compound A; the method of producing the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as in Example 1.

[0181] Example 17

[0182] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, with the exception that 0.002 parts of trimethyl phosphite (Formula 11) is added as the compound A; the method of producing the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as in Example 1.

[0183] Example 18

[0184] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, with the exception that 0.002 parts of trimethyl phosphite (Formula 11) is added as the compound A; the method of producing the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as in Example 1.

[0185] Example 19

[0186] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, with the exception that 0.002 parts of trimethyl phosphite (Formula 11) is added as the compound A; the method of producing the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as in Example 1.

[0187] Example 20

[0188] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, with the exception that 0.002 parts of trimethyl phosphite (Formula 11) is added as the compound A; the method of producing the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as in Example 1.

[0189] Example 21

[0190] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, with the exception that 0.002 parts of tetramethyl methylene diphosphonate (Formula 16) is added as the compound A; the method of producing the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as in Example 1.

[0191] Example 22

[0192] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, with the exception that 0.002 parts of tetraethyl ethylene diphosphonate (Formula 17) is added as the compound A; the method of producing the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as in Example 1.

[0193] Comparative Example 1

[0194] A paste for a secondary battery, a slurry for a positive electrode of a secondary battery, a positive electrode for a secondary battery, and a secondary battery are provided in this example, with the exception that no compound A is added; the method of producing the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery is the same as in Example 1.

[0195] The paste for a secondary battery, the slurry for a positive electrode of a secondary battery, the positive electrode for a secondary battery, the negative electrode for a secondary battery, and the secondary battery provided in Examples 1-22 and Comparative Example 1 are subjected to performance testing, with the testing method as follows:

[0196] Stability: Under the conditions of a temperature of 25°C and a rotor rotation speed of 16 RPM, the viscosity of the paste for a secondary battery immediately after production (initial viscosity) is measured using a digital viscometer (manufactured by Shenzhen Kejing Wisdom Technology Co., Ltd., "MSK-SFM-VSSR"). Next, the paste for a secondary battery is stored at room temperature for 1 hour, and then the viscosity is measured under the same conditions as the initial viscosity (viscosity after storage). Then, the value (%) of the viscosity after storage when the initial viscosity is 100% is evaluated according to the following standards. The smaller the change in viscosity, the more excellent the stability of the paste. A: the viscosity after storage is 100% or more and less than 150%; B: the viscosity after storage is 150% or more and less than 200%; C: the viscosity after storage is 200% or more and less than 250%; D: the viscosity after storage is 250% or more.

[0197] Internal resistance: The secondary battery was charged to 3.75 V at 0.5 C (C is a value indicated by the rated capacity (mA) / 1 hour (h)) at 25°C. Then, the internal resistance of the battery was measured with a precision battery internal resistance tester (ANDO ELECTRIC CO., LTD., "HK3560", frequency 1000 Hz). For the obtained resistance value (Ω), the change rate (%) from the value of the comparative example (0% for the comparative example) was calculated, and evaluation was performed in accordance with the following criteria. The smaller the resistance value, the smaller the internal resistance, and the more excellent the output characteristics of the secondary battery. A: resistance reduced by 80.0% or more; B: resistance reduced by 50.0% or more and less than 80.0%; C: resistance reduced by 1.0% or more and less than 50.0%; D: resistance reduced by less than 1.0%, the same as the comparative example, or increased compared to the comparative example.

[0198] Cycle characteristics: The secondary battery was charged to 3.75 V at 0.1 C (C is a value indicated by the rated capacity (mA) / 1 hour (h)) and discharged to 2.0 V at 25°C, and this operation was repeated 3 times. Then, at 25°C, the battery was charged to 3.75 V at 1 C and discharged to 2.0 V at 1 C, and this operation was repeated 150 times. Then, from the discharge capacity at the first time (CO) and the discharge capacity at the 150th time (Cl), the capacity retention rate AC = (Cl / CO) x 100 (%) was calculated, and evaluation was performed in accordance with the following criteria. The higher the value of the capacity retention rate, the less the discharge capacity decreased, and the more excellent the cycle characteristics of the secondary battery. A: the capacity retention rate AC was 80.0% or more; B: the capacity retention rate AC was 60.0% or more and less than 80.0%; C: the capacity retention rate AC was 40.0% or more and less than 60.0%; D: the capacity retention rate AC was less than 40.0%.

[0199] The test results are shown in Tables 1-3. "BA" indicates a butyl acrylate unit.

[0200] Table 1

[0201]

[0202] Table 2

[0203]

[0204] Table 3

[0205]

[0206] As is clear from Tables 1-3, in Examples 1-13 in which the paste for secondary batteries using Compound A was used to produce the positive electrode, the internal resistance of the secondary battery could be reduced and the cycle characteristics could be improved. Furthermore, it was also known that in Examples 1-13, the stability of the paste for secondary batteries was excellent.

[0207] On the other hand, according to Table 1-3, in the comparative example of the paste for secondary batteries not using the compound A, the internal resistance of the secondary battery increased, and in addition, the cycle characteristics decreased. The paste for secondary batteries described above can produce an electrode that can reduce the internal resistance of a secondary battery and cause the secondary battery to exhibit excellent cycle characteristics. The slurry for secondary battery positive electrodes can produce a positive electrode that can reduce the internal resistance of a secondary battery and cause the secondary battery to exhibit excellent cycle characteristics. The secondary battery positive electrode can reduce the internal resistance of a secondary battery and cause the secondary battery to exhibit excellent cycle characteristics. The internal resistance of the secondary battery is reduced and the cycle characteristics are excellent.

[0208] The above description is merely preferred specific embodiments of the present application, but the scope of the present application is not limited thereto. Any person skilled in the art, according to the technical range disclosed in the present application, can make equivalent replacements or changes to the technical solutions and the application concept of the present application within the technical range disclosed in the present application, and all such replacements or changes should be encompassed within the scope of the present application.

Claims

1. A paste for secondary batteries, characterized in that, It comprises, by weight parts: 1 to 10 parts conductive additive, 0.02 to 1 part polymer, 88 to 98 parts dispersion medium and 0.0001 to 1 part compound A; The compound A has one or more of the structures of Formula 1 to Formula 4; Among them, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 R 12 R 13 R 14 Each independently is C1 to C 30 Alkyl, C2 to C 30 alkenyl, C4 to C 30 diene group, C4 to C 30 alkynyl diol, C1 to C 20 alkoxy groups, C5 to C 24 cycloalkyl, C6 to C 24 aryl, C3 to C 10 Cycloalkenyl, C5 to C8 cyclodienyl, halogenated C5 to C8 cycloalkenyl 24 Aryl, halogen-substituted C5 to C 24 Alkyl or trimethylsilyl groups.

2. The paste for secondary batteries according to claim 1, characterized in that, The R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 R 12 R 13 R 14 Each independently is C6 to C 10 Alkyl, C6 to C 10 alkenyl, C6 to C 10 diene group, C6 to C 10 alkoxy groups, C6 to C 10 cycloalkyl, C6 to C 10 aryl, C6 to C 10 Cycloalkenyl, C6 to C 10 Cyclodiene, halogen, or trimethylsilyl.

3. The paste for secondary batteries according to claim 1, characterized in that, The compound A has any one of the structures of Formula 5 to Formula 17; 4. The paste for secondary batteries according to claim 1, characterized in that, The conductive additives include one or more of the following: carbon nanotubes, carbon black, carbon nanotubes, carbon fibers, graphene, carbon nonwoven fabric sheets, metal fibers, or metal foils. The polymer comprises alkylene structural units and nitrile monomer units; The dispersion medium includes one or more of acetonitrile, N-methylpyrrolidone, cyclopentanone, N,N-dimethylacetamide, dimethylformamide, dimethyl sulfoxide, methylformamide, methyl ethyl ketone, or furfural.

5. The paste for secondary batteries according to claim 1, characterized in that, The polymer comprises one or more of acrylic rubber, polyvinylpyrrolidone, polyvinylidene fluoride, nitrile rubber or hydrogenated nitrile rubber; the polymer comprises 10 to 50 parts by mass of nitrile monomer units and 15 to 85 parts by mass of conjugated diene monomer units. The degree of hydrogenation of the conjugated diene monomer units in the polymer is 90% to 100%.

6. A method for preparing a paste for secondary batteries as described in any one of claims 1 to 5, characterized in that, include: A paste for secondary batteries is obtained by mixing conductive additives, polymers, dispersion media and compound A.

7. A slurry for the positive electrode of a secondary battery, characterized in that, The mixture comprises, by weight, 90 to 99 parts of positive electrode active material and 1 to 10 parts of secondary battery paste as described in any one of claims 1 to 5 or secondary battery paste prepared according to the preparation method described in claim 6.

8. The slurry for the positive electrode of a secondary battery according to claim 7, characterized in that, The positive electrode active materials include lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium-containing Co-Ni-Mn composite oxide, lithium-containing Ni-Mn-Al composite oxide, lithium-containing Ni-Co-Al composite oxide, olivine-type lithium iron phosphate, olivine-type lithium manganese phosphate, olivine-type lithium manganese iron phosphate, Li2MnO3-LiNiO2 solid solution, lithium-excess spinel compound, and Li[Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 O2 or LiNi 0.5 Mn 1.5 One or more of O4.

9. A positive electrode for a secondary battery, characterized in that, The secondary battery positive electrode slurry as described in claim 7 or 8 is coated onto the surface of the current collector and dried.

10. A secondary battery, characterized in that, Includes the positive electrode for a secondary battery as described in claim 9.

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