Composition for forming electrode, additive, and gelation inhibitor

Abstract

An electrode-forming composition containing a compound having a ring structure and an unsaturated bond, a positive electrode active material, a binder, and a solvent, the compound having dissociative protons in the molecule, the proton dissociation energy of the compound being less than 1504.7 (kJ / mol), and the bond dissociation energy of the compound being less than 452.61 (kJ / mol).

Description

Technical Field

[0001] This invention relates to an electrode forming composition, an additive, and a gelation inhibitor. Furthermore, this invention relates to an electrode layer, a secondary battery, a method for manufacturing an electrode forming composition, and a method for inhibiting gelation of the electrode forming composition. Background Technology

[0002] Lithium-ion rechargeable batteries have high energy density per unit weight and volume, which helps to make electronic devices smaller and lighter. In recent years, as a countermeasure for zero emissions in automobiles, the popularization of electric vehicles has accelerated, seeking further improvements in resistance, lifespan, capacity, safety, and cost.

[0003] Lithium-ion secondary batteries typically have a three-layer structure consisting of a positive electrode, a separator, and a negative electrode, containing an electrolyte. The positive and negative electrodes are manufactured by mixing active materials, conductive materials, and a binder, and then coating the resulting electrode slurry onto a current collector. Currently, the mainstream method for manufacturing the negative electrode involves coating a negative electrode slurry onto a copper foil (which serves as the current collector) and drying it. The mainstream method for manufacturing the positive electrode involves preparing a positive electrode slurry using an organic solvent such as N-methyl-2-pyrrolidone as a solvent, and then coating the resulting positive electrode slurry onto an aluminum foil (which serves as the current collector).

[0004] As positive electrode active materials for lithium-ion secondary batteries, inorganic compounds such as transition metal oxides and transition metal chalcogenides containing alkali metals are known to provide a battery voltage of around 4V. Among these, highly alkaline positive electrode active materials containing nickel and manganese are used in large quantities to obtain high-capacity lithium-ion secondary batteries.

[0005] For example, Li x NiO2, representing high-nickel cathode active material, is an attractive cathode material with high discharge capacitance. However, its surface contains residues from raw materials or alkaline components such as LiOH, Li2O, LiHCO3, and Li2CO3 generated from proton exchange reactions with moisture or carbon dioxide in the air.

[0006] When using such positive electrode active materials, the electrode slurry thickens or gels, gradually losing its fluidity. If the electrode slurry loses its fluidity, it is not only difficult to obtain a uniform coating thickness, but in some cases, coating may not be possible at all, resulting in material waste.

[0007] The main reason is believed to be that during the manufacturing process of the positive electrode, the alkaline components present on the surface of the positive electrode active material, in the presence of trace amounts of moisture, promote the defluorination and hydrogenation reaction of fluorinated adhesives represented by polyvinylidene fluoride (PVdF), which has a vinylidene fluoride structure, used as adhesives.

[0008] Furthermore, alkaline components can corrode the aluminum foil typically used as the positive electrode, thereby increasing the battery's resistance. Additionally, these alkaline components may react with the electrolyte within the battery, further increasing resistance and potentially shortening its lifespan.

[0009] The aforementioned thickening and gelation can be suppressed by controlling the moisture content of the raw materials and electrode slurry in a dry environment. However, large-scale equipment is required in the series of mass production processes from preparing the electrode slurry to manufacturing the battery. In addition, the increased cost and environmental impact caused by the use of large amounts of electricity become problems.

[0010] To address this problem, for example, Patent Document 1 discloses a technique for preparing electrode slurry (positive electrode material slurry) in a manner that does not exhibit strong alkalinity even when dispersed in water, thereby suppressing gelation of the electrode slurry. However, the method described in Patent Document 1 requires not only strict pH management to prepare the electrode slurry in a manner that does not exhibit strong alkalinity, but also involves the following process: temporarily dispersing the positive electrode active material in water, filtering out the positive electrode active material from the dispersion, and then drying it. As a result, this leads to complex operations and a reduced yield. Furthermore, the aforementioned processing may also cause a decrease in the performance of the positive electrode active material itself.

[0011] Furthermore, Patent Document 2 reports a technique that uses ultra-high molecular weight (weight-average molecular weight of 2.2 million or more) compounds such as polyethylene oxide to bind water through interactions with it (e.g., hydrogen bonds), thereby inhibiting the reaction between the alkaline component of the positive electrode active material and water, and thus suppressing thickening and gelation. However, ultra-high molecular weight polymers with strong thickening effects have operational problems such as time-consuming and costly homogeneous dissolution processes in solvents, and difficulty in producing high-concentration solutions. In addition, the high water-binding capacity of the aforementioned ultra-high molecular weight polymers means that the polymer itself may introduce water; to prevent this, strict management of the pre-drying process is required.

[0012] Patent documents 3 and 4 propose adding organic or inorganic acids to the positive electrode of a lithium-ion secondary battery to suppress gelation of the electrode slurry (positive electrode paste). In patent document 3, maleic acid, citrate, and malonic acid are used in the positive electrode paste, while in patent document 4, acetic acid, phosphoric acid, and sulfuric acid are used in the electrode slurry (positive electrode paste). However, using acid to neutralize alkali requires a large amount of addition, which may result in a decrease in battery energy density and an increase in battery resistance. Furthermore, there is a problem that the acid may corrode the electrode fabrication apparatus. Additionally, the high acidity of the organic and inorganic acids in this method may cause a neutralization reaction with lithium ions in the active material, potentially leading to problems related to battery performance degradation.

[0013] Patent document 5 reports a method that uses fluorine gas to treat the positive electrode active material, immobilizing residual LiOH into LiF, thereby preventing gelation and suppressing gas generation. However, fluorine gas is highly toxic and difficult to handle. Furthermore, the LiF produced as a byproduct increases the internal resistance of the battery, reduces capacity, and causes further capacity reduction due to corrosion of the positive electrode active material caused by fluorine gas. Moreover, there are problems such as residual fluorine reacting with trace amounts of moisture present in the active material and electrolyte to produce hydrogen fluoride, which easily leads to cycle degradation.

[0014] Patent document 6 reports the removal of unreacted lithium hydroxide and impurities derived from raw materials by washing with an aqueous solution containing lithium salt. However, there are problems with the increased environmental impact caused by the wastewater discharged during washing and the associated costs of wastewater treatment.

[0015] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2000-90917 Patent Document 2: Japanese Patent Application Publication No. 2019-121471 Patent Document 3: Japanese Patent Application Publication No. 9-306502 Patent Document 4: Japanese Patent Application Publication No. 10-79244 Patent Document 5: Japanese Patent Application Publication No. 2006-286240 Patent Document 6: International Publication No. 2017 / 034001 Summary of the Invention

[0016] The problem that the invention aims to solve Based on the above, the present invention aims to provide an electrode forming composition, an additive for the electrode forming composition, and a gelation inhibitor, wherein the electrode forming composition inhibits thickening and gelation by a simple method, thereby improving storage stability. Furthermore, the present invention aims to provide an electrode layer using the electrode forming composition, a secondary battery, a method for manufacturing the electrode forming composition, and a method for inhibiting gelation of the electrode forming composition.

[0017] Solution for solving the problem The inventors conducted in-depth research to solve the aforementioned problems and found that the problems could be solved, thus completing the present invention with the following main objectives.

[0018] That is, the present invention includes the following.

[0019] [1] An electrode forming composition comprising a compound having a ring structure and unsaturated bonds, a positive electrode active material, a binder, and a solvent, wherein the compound has dissociable protons within the molecule, the proton dissociation energy of the compound is less than 1504.7 (kJ / mol), and the bond dissociation energy of the compound is less than 452.61 (kJ / mol).

[0020] [2] The electrode forming composition according to [1], wherein the positive electrode active material comprises a polycrystalline first positive electrode active material and a single-crystal second positive electrode active material.

[0021] [3] According to the electrode forming composition of [2], wherein the first positive electrode active material is a lithium-containing transition metal oxide particle having a layered rock salt structure, and the microcrystal size of the lithium-containing transition metal oxide particle, based on the diffraction peak of the (104) plane obtained by X-ray diffraction pattern using a CuKα radiation source, is 20 nm or more and less than 500 nm as determined by the Scherrer formula.

[0022] [4] The electrode forming composition according to [2] or [3], wherein the second positive electrode active material is a lithium-containing transition metal oxide particle having a layered rock salt structure, wherein the diffraction peak of the lithium-containing transition metal oxide particle based on the (104) plane obtained by X-ray diffraction pattern using a CuKα radiation source has a crystallite size of 50 nm or more and less than 800 nm as determined by the Scherrer formula.

[0023] [5] The electrode forming composition according to [3] or [4], wherein the lithium-containing transition metal oxide particles having a layered rock salt structure in the first positive electrode active material are of the general formula Li a Ni （1－x－y） Co x M 1y M 2 z O2 (where M is in the formula) 1 It means that at least one of the groups consisting of Mn and Al is selected, M 2 The term refers to crystalline metal oxide particles selected from at least one of the group consisting of Zr, Ti, Mg, B, W and V, where 1.00≤a≤1.50, 0.00≤x≤0.50, 0.00≤y≤0.50, and 0.000≤z≤0.020.

[0024] [6] The electrode forming composition according to [4] or [5], wherein the lithium-containing transition metal oxide particles having a layered rock salt structure in the second positive electrode active material are of the general formula Li a Ni （1－x－y） Co x M 1 y M 2 z O2 (where M is in the formula) 1 It means that at least one of the groups consisting of Mn and Al is selected, M 2 The term refers to crystalline metal oxide particles selected from at least one of the group consisting of Zr, Ti, Mg, B, W and V, where 1.00≤a≤1.50, 0.00≤x≤0.50, 0.00≤y≤0.50, and 0.000≤z≤0.020.

[0025] [7] An electrode forming composition according to any one of [1] to [6], wherein the ring structure is an aromatic ring.

[0026] [8] An electrode forming composition according to any one of [1] to [7], wherein the compound has heteroatoms.

[0027] [9] An electrode forming composition according to any one of [1] to [8], wherein the positive electrode active material comprises a metal oxide containing Ni.

[0028]

[10] An electrode forming composition according to any one of [1] to [9], wherein the positive electrode active material contains Ni, and the Ni content in the positive electrode active material is 30% by mass or more and 61% by mass or less.

[0029]

[11] An electrode forming composition according to any one of [1] to

[10] , wherein the solvent is an aprotic solvent.

[0030]

[12] An electrode forming composition according to any one of [1] to

[11] , wherein the adhesive is a fluorine-based adhesive.

[0031]

[13] An electrode forming composition according to any one of [1] to

[12] , wherein the electrode forming composition further comprises a conductive additive.

[0032]

[14] An electrode layer obtained from an electrode forming composition as described in any one of [1] to

[13] .

[0033]

[15] A secondary battery having an electrode layer as described in

[14] .

[0034]

[16] A method for manufacturing an electrode forming composition, wherein the electrode forming composition is manufactured as described in any one of [1] to

[13] , the method comprising: mixing the compound, the binder, the solvent, a polycrystalline first positive electrode active material and a single-crystal second positive electrode active material.

[0035]

[17] The method for manufacturing an electrode forming composition according to

[16] wherein the mass ratio of the first positive electrode active material to the second positive electrode active material in the electrode forming composition (first positive electrode active material: second positive electrode active material) is 2:8 to 8:2.

[0036]

[18] An additive is an additive for an electrode forming composition comprising a polycrystalline first positive electrode active material, a single crystal second positive electrode active material, a binder and a solvent, wherein the additive has intramolecularly dissociable protons with a proton dissociation energy of less than 1504.7 (kJ / mol) and a bond dissociation energy of less than 452.61 (kJ / mol).

[0037]

[19] A gelation inhibitor is a gelation inhibitor of an electrode forming composition comprising a polycrystalline first positive electrode active material, a single-crystal second positive electrode active material, a binder and a solvent, wherein the gelation inhibitor has a dissociable proton in the molecule with a proton dissociation energy of less than 1504.7 (kJ / mol) and a bond dissociation energy of less than 452.61 (kJ / mol).

[0038]

[20] A method for suppressing gelation, which is a method for suppressing gelation of an electrode forming composition comprising a polycrystalline first positive electrode active material, a single-crystal second positive electrode active material, a binder and a solvent, wherein the electrode forming composition is in a state containing a compound having protons that are dissociable within the molecule, the proton dissociation energy being less than 1504.7 (kJ / mol) and the bond dissociation energy being less than 452.61 (kJ / mol).

[0039] Invention Effects According to the present invention, an electrode forming composition, an additive for the electrode forming composition, and a gelation inhibitor are provided, wherein the electrode forming composition inhibits thickening and gelation by a simple method, thereby improving storage stability. Furthermore, according to the present invention, an electrode layer using the electrode forming composition and a secondary battery, as well as a method for manufacturing the electrode forming composition and a method for inhibiting gelation of the electrode forming composition, are provided. Attached Figure Description

[0040] Figure 1 This is a graph for additives A1-A27, a1-a12, and a25, where the proton dissociation energy is plotted on the horizontal axis and the bond dissociation energy on the vertical axis. Detailed Implementation

[0041] (Composition for electrode formation) The electrode forming composition of the present invention comprises at least a compound having a ring structure and unsaturated bonds (hereinafter sometimes referred to as "specific compound"), a positive electrode active material, a binder, and a solvent.

[0042] The composition for electrode forming may also contain other components.

[0043] A specific compound has protons that can dissociate within its molecule.

[0044] The proton dissociation energy of a certain compound is less than 1504.7 (kJ / mol).

[0045] The bond dissociation energy of a specific compound is less than 452.61 (kJ / mol).

[0046] The electrode forming composition of the present invention is not prone to thickening or gelation, exhibits high storage stability, and is preferably used for forming positive electrode for secondary batteries. When manufacturing secondary batteries equipped with electrodes made using the aforementioned composition, the following advantages are expected: improved quality and yield due to the improved storage stability of the composition; cost reduction and reduced environmental impact due to the high concentration of solid components; and suppression of battery degradation caused by alkaline components, which contributes to reducing the manufacturing cost of secondary batteries and improving battery characteristics.

[0047] Electrode-forming compositions containing two positive electrode active materials (particularly a polycrystalline first positive electrode active material and a monocrystalline second positive electrode active material) are more prone to thickening and gelation. In one embodiment of the electrode-forming composition of the present invention, by adding a specific compound to an electrode-forming composition containing two positive electrode active materials (particularly a polycrystalline first positive electrode active material and a monocrystalline second positive electrode active material), thickening and gelation of the composition that is more prone to thickening and gelation can be suppressed.

[0048] The mechanisms of thickening and gelation, as well as the mechanisms by which their inhibitory effects are manifested, are still uncertain. The inventors believe that one of the reasons is that by adding a specific compound to the composition for electrode formation, the specific compound deactivates the free radicals generated in the composition that promote thickening and gelation.

[0049] If a compound possesses a dissociation proton, meaning its proton dissociation energy is low, the compound readily releases protons. These released protons are easily reduced by a single electron, generating hydrogen radicals. Conversely, if a compound has a low bond dissociation energy, it is prone to free radicalization. This can be illustrated as shown below. Hydrogen radicals can react, for example, with adhesives that are free radicalized due to the presence or generation of alkaline components in the composition (e.g., radical coupling). When the free radicals of the adhesive are deactivated through the above-described reaction, the thickening and gelling reactions of the adhesive are inhibited. As a result, it is believed that the thickening and gelling of the composition can be inhibited, thus improving storage stability. However, these are presumptions, and the present invention is not limited to these mechanisms.

[0050] By suppressing the thickening and gelation of the electrode forming composition, a homogeneous positive electrode layer can be formed. Furthermore, the concentration of solid components in the electrode slurry can be increased, reducing the cost and environmental impact of manufacturing energy storage devices. Moreover, it can suppress corrosion of aluminum foil, commonly used as a current collector, originating from alkaline components, and the degradation of battery characteristics caused by reactions with the electrolyte.

[0051] <Specific Compound> The specific compound is one that has a ring structure and unsaturated bonds.

[0052] A specific compound has protons that can dissociate within its molecule.

[0053] The proton dissociation energy of a certain compound is less than 1504.7 (kJ / mol).

[0054] The bond dissociation energy of a specific compound is less than 452.61 (kJ / mol).

[0055] It should be noted that certain compounds may have ring structures and unsaturated bonds, but the presence or absence of ring structures and unsaturated bonds is not important in terms of whether the invention achieves its intended effects.

[0056] The ring structure of a specific compound can be either an aliphatic ring or an aromatic ring.

[0057] Furthermore, the ring structure possessed by a particular compound can be a hydrocarbon ring or a heterocycle.

[0058] A particular compound may or may not have heterocycles.

[0059] A particular compound may or may not have an aromatic ring.

[0060] The unsaturated bonds in a particular compound can be either double bonds or triple bonds.

[0061] The unsaturated bonds in a particular compound can also be unsaturated bonds that form a ring structure.

[0062] For example, benzene is a compound with a cyclic structure and three unsaturated bonds.

[0063] Examples of double bonds include: carbon-carbon double bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, carbon-sulfur double bonds, and nitrogen-nitrogen double bonds.

[0064] Examples of triple bonds include carbon-carbon triple bonds and carbon-nitrogen triple bonds.

[0065] There is no particular restriction on the number of unsaturated bonds in a specific compound; it can be one or more.

[0066] A specific compound is composed of, for example, hydrogen and at least one of the nonmetallic elements from Group IVA to Group VIIA. Examples of nonmetallic elements from Group IVA to Group VIIA include: boron, carbon, silicon, nitrogen, phosphorus, oxygen, sulfur, halogens, etc.

[0067] Certain compounds may or may not contain heteroatoms. Examples of heteroatoms include: oxygen, nitrogen, phosphorus, silicon, sulfur, and halogen atoms. Examples of halogen atoms include: fluorine, chlorine, iodine, and bromine atoms.

[0068] For example, in the case where a particular compound has heteroatoms, the heteroatoms in the particular compound are at least any one of oxygen, sulfur, and nitrogen atoms.

[0069] For example, in the case of a particular compound having heteroatoms, the heteroatoms in that particular compound are only nitrogen atoms.

[0070] The specific compound differs from the solvent used in this invention. In this respect, the specific compound is, for example, a solid at room temperature. In this invention, "solid at room temperature" means having a melting point above 25°C at one atmosphere.

[0071] There are no particular restrictions on the molecular weight of a specific compound; for example, it can be 60–1000, 60–700, 100–700, or 100–350.

[0072] The number of protons, which are the dissociative property of a particular compound, is not particularly limited; it can be one or more.

[0073] If the proton dissociation energy can be calculated, it can be said that the compound has protons that are capable of dissociation.

[0074] The proton dissociation energy of a specific compound is less than 1504.7 (kJ / mol), or it can be below 1489.6 (kJ / mol) or below 1474.5.

[0075] There are no particular restrictions on the lower limit of the proton dissociation energy. For example, the proton dissociation energy can be above 1254.0 (kJ / mol), above 1300.0 (kJ / mol), or above 1345.9 (kJ / mol).

[0076] The method for calculating the proton dissociation energy is as follows.

[0077] [Methods for calculating proton dissociation energy] Using B3LYP as the generalized function and 6-31+G(d) as the basis function, the most stable ground state structure of the target molecule (HA) in vacuum is calculated, and its total energy E(HA) is determined. Furthermore, for the dissociation of a dissociative proton (H) from the target molecule (HA),... ＋ The anion formed by ) (A － Using B3LYP as the functional and 6-31+G(d) as the basis function, calculate its most stable structure in the vacuum ground state and its total energy E(A). － Therefore, the proton dissociation energy ΔE, as defined by equation (a), can be calculated. pd (Unit: kJ / mol).

[0078] (a) ΔE pd = [E(A)] － ) + E(H ＋ )] - E(HA) However, protons (H ＋ Since protons do not have electrons, their total energy cannot be evaluated through quantum chemical calculations. Therefore, the total energy E(H) of a proton here is... ＋ The value of is set to 0 kJ / mol. It should be noted that for a molecule containing protons with multiple dissociation properties, only the first stage of proton dissociation is considered. The total energy E(A) of the anion after proton dissociation is... － The proton dissociation energy is calculated by finding the smallest proton dissociation position.

[0079] The bond dissociation energy of a specific compound is less than 452.61 (kJ / mol), or it can be below 445.20 (kJ / mol) or below 437.78 (kJ / mol).

[0080] There are no particular restrictions on the lower limit of the bond dissociation energy. For example, the bond dissociation energy can be above 250.00 (kJ / mol), above 276.33 (kJ / mol), or above 302.65 (kJ / mol).

[0081] The method for calculating bond dissociation energy is as follows.

[0082] [Methods for calculating bond dissociation energy] For a neutral radical (A·) formed by the detachment of a hydrogen radical (H·) from a target molecule, using B3LYP as the functional and 6-31+G(d) as the basis function, its most stable structure in the ground state under vacuum is calculated, and its total energy E(A·) is calculated. Furthermore, for the hydrogen radical (H·), also using B3LYP as the functional and 6-31+G(d) as the basis function, the total energy E(H·) is calculated. Using the value of E(HA) obtained through the calculation of the proton dissociation energy, the bond dissociation energy ΔE, defined by equation (b), is then calculated. bd (Unit: kJ / mol).

[0083] (b) ΔE bd =[E(A·)+E(H·)]-E(HA) It should be noted that the molecule in question has multiple hydrogen atoms, but only hydrogen removal from one site is considered. The bond dissociation energy is calculated for the total energy E(A·) of the neutral free radical obtained through hydrogen removal, which is the smallest removal site.

[0084] An example of a specific compound is shown. The content of a specific compound in the electrode forming composition is not particularly limited, but is preferably 0.001 to 4% by mass in the solid component, more preferably 0.001 to 2% by mass, even more preferably 0.001 to 0.5% by mass, even more preferably 0.001 to 0.3% by mass, and particularly preferably 0.001 to 0.2% by mass.

[0085] Furthermore, a further preferred lower limit for the content of the specific compound is 0.01% by mass in the solid components. By setting the content of the specific compound within the above range, gelation of the composition for electrode forming can be effectively suppressed, and the battery characteristics of the obtained battery can also be maintained. It should be noted that, in this invention, the solid components refer to components other than the solvent constituting the composition (the same applies below).

[0086] Furthermore, the content of a specific compound in the electrode forming composition is preferably 0.001 to 4 parts by mass relative to 100 parts by mass of the positive electrode active material, more preferably 0.001 to 2 parts by mass, even more preferably 0.001 to 0.5 parts by mass, even more preferably 0.001 to 0.3 parts by mass, and particularly preferably 0.001 to 0.2 parts by mass.

[0087] By setting the content of the specific compound within the above range, the gelation of the composition for electrode forming can be effectively suppressed, and the battery characteristics of the obtained battery can also be maintained.

[0088] Furthermore, the content of a specific compound in the electrode forming composition is preferably 0.1 to 50 parts by weight relative to 100 parts by weight of the binder, more preferably 0.1 to 30 parts by weight, and even more preferably 0.1 to 20 parts by weight.

[0089] By setting the content of the specific compound within the above range, the gelation of the composition for electrode forming can be effectively suppressed, and the battery characteristics of the obtained battery can also be maintained.

[0090] Furthermore, when the electrode forming composition contains a conductive additive, the content of a specific compound in the electrode forming composition is preferably 0.1 to 50 parts by mass relative to 100 parts by mass of the conductive additive, more preferably 0.1 to 30 parts by mass, and even more preferably 0.1 to 20 parts by mass.

[0091] <Positive Electrode Active Material> There are no particular restrictions on its use as a positive electrode active material.

[0092] As a positive electrode active material, considering the need to further increase battery capacity while minimizing the use of rare metals and reducing costs, it is preferable to include S, Fe, or Ni, more preferably 30% by mass or more of S, Fe, or Ni. When considering further reducing the use of rare metals to obtain a battery with a longer lifespan, it is even more preferable to include 35% by mass or more of Fe or Ni, and even more preferably 45% by mass or more of Fe or Ni. Furthermore, there is no particular upper limit, and it is typically 61% by mass or less.

[0093] Electrode-forming compositions containing positive electrode active materials with high nickel content have a strong tendency to thicken and gel. Therefore, considering the ability to suppress thickening and gelation in electrode-forming compositions containing positive electrode active materials with high nickel content, it is preferable that the positive electrode active material contains Ni, more preferably 30% by mass or more, and particularly preferably 40% by mass or more. There is no particular limit to the upper limit of the Ni content in the positive electrode active material; for example, the Ni content can be 61% by mass or less.

[0094] As a positive electrode active material, it can be appropriately selected from various active materials that have been used in electrodes for secondary batteries. For example, in the case of lithium secondary batteries and lithium-ion secondary batteries, chalcogenides that can absorb / release lithium ions, lithium-ion-containing chalcogenides, polyanionic compounds, elemental sulfur and their compounds, etc., can be used.

[0095] Examples of lithium-ion-containing chalcogenides include: LiNiO2, Li x Ni y M 1－y O2 (M represents at least one metallic element selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, 0.05≤x≤1.10, 0.3≤y≤1.0), Li a Ni （1－x－y） Co x M 1 y M 2 z O2 (M) 1 It means that at least one of the groups consisting of Mn and Al is selected, M 2 It means that it is selected from at least one of the group consisting of Zr, Ti, Mg, B, Zr, Si, W and V, and 1.00≤a≤1.50, 0.00≤x≤0.50, 0.00≤y≤0.50, 0.000≤z≤0.020, etc.

[0096] Examples of polyanionic compounds include: LiFePO4, Li a Mn b Fe c D d PO4 (1.00≤a≤1.15, 0.01≤b≤0.99, 0.01≤c≤0.99, 0.00≤d≤0.10, where D is selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb and Zn, and at least a portion of them have an olivine structure), etc.

[0097] Examples of sulfur compounds include sulfur, Li2S, FeS2, TiS2, MoS2, and erythrine.

[0098] These positive electrode active materials can be used alone, or in combination of two or more.

[0099] Among the above-mentioned positive electrode active materials, the general formula Li is preferred. a Ni （1－x－y） Co x M 1 y M 2 z O2 (where M is in the formula) 1 It means that at least one of the groups consisting of Mn and Al is selected, M 2 It means that at least one is selected from the group consisting of Zr, Ti, Mg, B, W and V, and 1.00≤a≤1.50, 0.00≤x≤0.50, 0.00≤y≤0.50, 0.000≤z≤0.020).

[0100] x can be 0.01≤x≤0.30 or 0.03≤x≤0.20.

[0101] y can be 0.01≤x≤0.30 or 0.03≤x≤0.20.

[0102] x + y can be either 0.02 ≤ (x + y) ≤ 0.40 or 0.05 ≤ (x + y) ≤ 0.30.

[0103] Li a Ni （1－x－y） Co x M 1 y M 2 z The Ni content in O2 is preferably 30% by mass or more, preferably 40% by mass or more, more preferably 45% by mass or more, and particularly preferably 47% by mass or more. There is no particular limitation on the upper limit of the Ni content; for example, the Ni content can be 61% by mass or less.

[0104] These active substances can be used alone or in combination of two or more.

[0105] Electrode-forming compositions containing two positive electrode active materials (particularly a polycrystalline first positive electrode active material and a monocrystalline second positive electrode active material) are more prone to thickening and gelation. By adding specific compounds to electrode-forming compositions containing two positive electrode active materials (particularly a polycrystalline first positive electrode active material and a monocrystalline second positive electrode active material), thickening and gelation of the compositions that are more prone to thickening and gelation can be suppressed. From this perspective, the positive electrode active material preferably comprises a polycrystalline first positive electrode active material and a monocrystalline second positive electrode active material.

[0106] The first positive electrode active material of the polycrystalline material is, for example, lithium-containing transition metal oxide particles with a layered rock salt structure. The microcrystal size of the lithium-containing transition metal oxide particles, which is the first positive electrode active material, is, for example, greater than 20 nm and less than 500 nm, determined by the Scherrer formula based on the diffraction peaks of the (104) plane obtained by X-ray diffraction pattern using a CuKα radiation source.

[0107] The second positive electrode active material of the single crystal is, for example, lithium-containing transition metal oxide particles with a layered rock salt structure. The microcrystal size of the lithium-containing transition metal oxide particles as the second positive electrode active material, based on the diffraction peaks of the (104) plane obtained by X-ray diffraction pattern using a CuKα radiation source, determined by the Scherrer formula, is, for example, 50 nm or more and less than 800 nm.

[0108] For example, the crystallite size of the first positive electrode active material and the crystallite size of the second positive electrode active material satisfy the following relationship (X).

[0109] x1<(τ2)-(τ1)≤x2 Formula (X) τ1: The crystallite size (nm) of the first positive electrode active material.

[0110] τ2: Crystalline particle size (nm) of the second positive electrode active material.

[0111] x1 is 0nm, preferably 10nm, more preferably 30nm, and particularly preferably 70nm.

[0112] x2 is 400nm, preferably 350nm, more preferably 300nm, and particularly preferably 250nm.

[0113] The grain size can be determined, for example, as described below.

[0114] [X-ray diffraction measurement] X-ray diffraction patterns of the positive electrode active material were obtained using a CuKα radiation source (45 kV, 40 mA) radiating at a wavelength of 1.5418 Å, collected using an X'Pert Pro MPD (PANaltical). The apparatus consisted of a 0.02 radian Soler slit, a 10 mm irradiation area automatically variable divergence slit, and a 1 / 2° antiscattering slit on the incident side, and an 8 mm antiscattering slit and a 0.02 radian Soler slit on the receiving side. The goniometer radius was 240 mm. In XRD, the diffraction pattern was obtained in the range of 10–100° (2θ) with a step size of 0.013° / scan and a step time of 250 seconds.

[0115] The crystallite size of the positive electrode active material is calculated using the known Scherrer formula, based on the diffraction angle of the peak of the (104) plane obtained from the X-ray diffraction pattern and the full width at half maximum (FWHM) obtained by subtracting the inherent full width at half maximum of the device.

[0116] [Sherlock Formula] τ: Crystalline size (in nm).

[0117] (Crystallite size refers to the average size of a regular (crystalline) domain that can be below the size of crystal grains.)

[0118] K: Scherrer constant (K = 0.9).

[0119] λ: X-ray wavelength (CuKα = 0.15418 nm).

[0120] β: FWHM.

[0121] θ: 1 / 2 of the diffraction angle 2θ of the diffraction peak belonging to the (104) plane.

[0122] At 44.5 ± 1° of the X-ray diffraction pattern, the peak assigned to the (104) plane of the crystal structure with space group R-3m was observed.

[0123] The inherent full width at half maximum (FWHM) of the device is 47.3° obtained using Si powder (NIST, SRM640f).

[0124] When the positive electrode active material comprises a polycrystalline first positive electrode active material and a monocrystalline second positive electrode active material, the mass ratio of the first positive electrode active material to the second positive electrode active material (first positive electrode active material: second positive electrode active material) in the electrode forming composition is not particularly limited, but is preferably 2:8 to 8:2, more preferably 4:6 to 8:2, and particularly preferably 4:6 to 7:3.

[0125] The content of the positive electrode active material in the electrode forming composition is not particularly limited, but is preferably 88.0 to 99.949% by mass in the solid component, more preferably 88.0 to 99.899% by mass, and even more preferably 95.0 to 99.0% by mass.

[0126] <Adhesive> As an adhesive, it can be appropriately selected from well-known materials without particular restrictions. Examples include: fluorinated adhesives, polyimide, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, polyethylene, and polypropylene. These are non-aqueous adhesives.

[0127] Examples of fluorinated adhesives include: polyvinylidene fluoride (PVdF); polytetrafluoroethylene (PTFE); and copolymers comprising at least one monomer selected from the group consisting of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene.

[0128] From the perspective of improving the storage stability of the electrode forming composition, fluorinated binders are preferred. Furthermore, the aforementioned fluorinated binders are preferably modified with polar functional groups such as carboxyl and hydroxyl groups. It should be noted that the aforementioned polar functional groups can be confirmed by the presence or absence of a distinct peak detected in the range of 10–15 ppm during measurements using a nuclear magnetic resonance (NMR) apparatus.

[0129] Adhesives can be used alone or in combination of two or more.

[0130] There is no particular limitation on the weight-average molecular weight (Mw) of the adhesive, but from the perspective of improving the adhesion between the current collector and the electrode layer, it is 600,000 to 3,000,000, preferably 700,000 to 2,000,000, and more preferably 700,000 to 1,500,000.

[0131] It should be noted that the weight-average molecular weight is a converted value of polystyrene obtained using gel permeation chromatography (GPC).

[0132] The content of binder in the electrode forming composition is not particularly limited. From the viewpoint of suppressing costs and obtaining high energy density, it is preferably 0.05 to 8% by mass in the solid component, more preferably 0.05 to 5% by mass, even more preferably 0.05 to 4% by mass, even more preferably 0.1 to 3% by mass, particularly preferably 0.2 to 2% by mass, and most preferably 0.3 to 1.5% by mass.

[0133] <Solvent> There are no particular limitations on the solvent; for example, solvents that have been conventionally used to prepare compositions for electrode formation can be listed.

[0134] Examples of solvents include water and organic solvents.

[0135] Examples of organic solvents include: ethers, halogenated hydrocarbons, amides, ketones, alcohols, aliphatic hydrocarbons, aromatic hydrocarbons, glycol ethers, glycols, carbonates, and other organic solvents.

[0136] Examples of ethers include tetrahydrofuran (THF), diethyl ether, and 1,2-dimethoxyethane (DME).

[0137] Examples of halogenated hydrocarbons include dichloromethane, chloroform, and 1,2-dichloroethane.

[0138] Examples of amides include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP).

[0139] Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

[0140] Examples of alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, and tert-butanol.

[0141] Examples of aliphatic hydrocarbons include n-heptane, n-hexane, and cyclohexane.

[0142] Examples of aromatic hydrocarbons include benzene, toluene, xylene, and ethylbenzene.

[0143] Examples of glycol ethers include: ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and propylene glycol monomethyl ether.

[0144] Examples of glycols include ethylene glycol and propylene glycol.

[0145] Examples of carbonates include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0146] Other organic solvents that can be used include: γ-butyrolactone, dimethyl sulfoxide (DMSO), dioxolane, sulfolane, etc.

[0147] Furthermore, the organic solvent can be either a protic solvent or an aprotic solvent, with an aprotic solvent being preferred.

[0148] As an aprotic solvent, it can be polar or non-polar.

[0149] As a nonprotic solvent, amides, ketones, and carbonates are preferred, with amides being more preferred.

[0150] These solvents can be used alone, or in combination of two or more.

[0151] The adhesive can be dissolved or dispersed in these solvents as needed. Preferred solvents in this case include: water, NMP, DMSO, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, THF, dioxolane, sulfolane, DMF, DMAc, etc. The appropriate solvent should be selected based on the type of adhesive; NMP is preferred for non-water-soluble adhesives such as PVdF, while water is preferred for water-soluble adhesives.

[0152] The concentration of the solid components in the electrode forming composition is appropriately set considering factors such as the coatability of the composition and the thickness of the formed electrode, and is typically 60 to 92% by mass, preferably 65 to 90% by mass, and more preferably 70 to 85% by mass.

[0153] <Other Ingredients> Other components that may be contained in the composition for forming electrodes include, for example, conductive additives and dispersants.

[0154] <<Conductive Additives>> Conductive additives are used, for example, to improve conductivity.

[0155] There are no particular limitations on its use as a conductive additive; examples include carbon materials and conductive polymers.

[0156] Examples of carbon materials include: graphite, carbon black, acetylene black (AB), vapor-grown carbon fibers, carbon nanotubes (CNTs), carbon nanotubes, and graphene.

[0157] Examples of conductive polymers include: polyaniline, polypyrrole, polythiophene, polyacetylene, and polybenzoxene.

[0158] Conductive additives can be used alone or in combination of two or more.

[0159] The content of the conductive additive in the electrode forming composition is not particularly limited, but is preferably 0.05 to 5% by mass in the solid component, more preferably 0.05 to 4% by mass, even more preferably 0.1 to 3% by mass, and even more preferably 0.2 to 2% by mass. Good conductivity can be obtained by setting the content of the conductive additive within the above range.

[0160] The composition for electrode formation, for example, does not contain graphene.

[0161] When the composition for forming the electrode contains graphene, the content of graphene as a conductive additive is not particularly limited, but is preferably 45% by mass or less, more preferably 40% by mass or less, and particularly preferably 10% by mass or less.

[0162] <<Dispersant>> Dispersants are used, for example, to improve the dispersibility of positive electrode active materials, conductive additives, and other substances.

[0163] As a dispersant, for example, it can be appropriately selected from substances that have been used as dispersants for conductive carbon materials such as CNTs.

[0164] From the perspective of battery stability, nonionic polymers are preferred as dispersants.

[0165] Examples of nonionic polymers include polyvinylpyrrolidone (PVP) and polymers containing at least one functional group selected from the group consisting of nitrile, hydroxyl, carbonyl, amino, sulfonyl, and ether groups.

[0166] Examples of such functionalized polymers include: polyvinyl alcohol, polyacrylonitrile, polylactic acid, polyester, polyimide, polyphenyl ether, polyphenylsulfone, polyethyleneimide, polyaniline, etc.

[0167] As a dispersant, polymers containing pyrrolidone structures or nitrile groups are preferred, and polyvinylpyrrolidone and polyacrylonitrile are more preferred.

[0168] Dispersants can be used alone or in combination of two or more.

[0169] The content of the dispersant in the electrode forming composition is not particularly limited, but is preferably 0.001 to 0.5% by mass in the solid component, more preferably 0.001 to 0.3% by mass, and even more preferably 0.001 to 0.2% by mass. Furthermore, a further preferred lower limit for the content of the dispersant is 0.01% by mass in the solid component.

[0170] Furthermore, when considering the adhesion between the obtained electrode layer and the current collector, the total amount of the specific compound and dispersant in the solid composition is preferably 0.001 to 1% by mass, more preferably 0.01 to 1% by mass.

[0171] The viscosity of the composition for electrode formation is appropriately set considering factors such as the coating method and the thickness of the formed electrode. It is typically around 100–2,000,000 mPa·s, preferably around 300–1,000,000 mPa·s, and more preferably around 400–800,000 mPa·s. The above viscosity values ​​were measured using an E-type viscometer at 25°C.

[0172] The electrode forming composition of the present invention can be obtained by mixing the above-described components. It should be noted that, when including any component other than the additive of the present invention (i.e., the gelation inhibitor (specific compound), the positive electrode active material, and the binder, the additive (i.e., the gelation inhibitor) and the positive electrode active material can be mixed together with any component, or the two components can be mixed beforehand and then mixed with any component. The effects of the present invention can be achieved in any of these methods.

[0173] (Electrode layer) The electrode layer of the present invention is obtained from the electrode forming composition of the present invention.

[0174] As a method for forming an electrode layer, one example is to apply an electrode forming composition onto a substrate to form a coating film, and then dry it. This method is not particularly limited, and various conventionally known methods can be used. Specific examples of coating methods include: various printing methods such as offset printing and screen printing, blade coating, dip coating, spin coating, bar coating, slot coating, inkjet coating, and mold coating.

[0175] Furthermore, when drying the coating, either natural drying or heated drying can be used; from the viewpoint of manufacturing efficiency, heated drying is preferred. When heated drying is performed, the temperature is preferably 50–400°C, more preferably 70–150°C.

[0176] The thickness of the electrode layer is not particularly limited, but is preferably 0.01 to 1000 μm, and more preferably 5 to 300 μm.

[0177] It should be noted that in secondary batteries, when the electrode layer is used as a separate electrode, it is preferable to set its film thickness to be 10 μm or more.

[0178] (electrode) The electrodes of the present invention have, for example, an electrode layer of the present invention on at least one side of a substrate serving as a current collector.

[0179] Examples of substrates used for electrodes include: metal substrates such as platinum, gold, iron, stainless steel, copper, aluminum, and lithium; alloy substrates composed of any combination of these metals; oxide substrates such as indium tin oxide (ITO), indium zinc oxide (IZO), and antimony tin oxide (ATO); and carbon substrates such as glassy carbon, pyrolytic graphite, and carbon felt.

[0180] The thickness of the substrate is not particularly limited, but is preferably 1 to 100 μm, more preferably 3 to 30 μm, and particularly preferably 5 to 25 μm.

[0181] The electrodes can also be pressed as needed. The pressing method can use commonly employed methods, with die pressing and roller pressing being particularly preferred. Furthermore, the pressing pressure is not particularly limited, but is preferably 1 kN / cm or more, more preferably 2 kN / cm or more, and particularly preferably 5 kN / cm or more. Moreover, the upper limit of the pressing pressure is not particularly limited, but the pressing pressure is preferably 50 kN / cm or less.

[0182] (Secondary battery) The secondary battery of the present invention includes the electrode layer of the present invention.

[0183] The secondary battery of the present invention includes, for example, the electrodes of the present invention.

[0184] A secondary battery, for example, includes at least one pair of positive and negative electrodes, a separator sandwiched between these electrodes, and an electrolyte. The positive electrode is the electrode of this invention.

[0185] There are no particular limitations on the materials used for membranes; for example, glass fiber, cellulose, porous polyolefins, polyamides, polyesters, etc. can be listed.

[0186] As an electrolyte, it can be any type of liquid or solid, and it can also be any type of aqueous or non-aqueous system. From the viewpoint of being able to easily exert full performance in practical applications, an electrolyte solution composed of electrolyte salts and solvents is preferred.

[0187] Examples of electrolyte salts include: lithium salts such as LiPF6, LiBF4, LiN(SO2F)2, LiN(C2F5SO2)2, LiAsF6, LiSbF6, LiAlF4, LiGaF4, LiInF4, LiClO4, LiN(CF3SO2)2, LiCF3SO3, LiSiF6, and LiN(CF3SO2)(C4F9SO2); metal iodides such as LiI, NaI, KI, CsI, and CaI2; iodide salts of quaternium compounds; iodide salts and perchlorates of tetraalkylammonium compounds; and metal bromides such as LiBr, NaBr, KBr, CsBr, and CaBr2.

[0188] These electrolyte salts can be used alone or in combination of two or more.

[0189] As a solvent, there are no particular limitations as long as it dissolves the electrolyte salt without causing corrosion or decomposition of the battery components, thus degrading their performance.

[0190] As solvents, for example, non-aqueous solvents include cyclic esters such as ethylene carbonate, propylene carbonate, butyl carbonate, and γ-butyrolactone; ethers such as tetrahydrofuran and dimethoxyethane; chain esters such as methyl acetate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; and nitrile solvents such as acetonitrile.

[0191] These solvents can be used alone, or in combination of two or more.

[0192] Furthermore, inorganic solid electrolytes such as sulfide-based solid electrolytes and oxide-based solid electrolytes, as well as organic solid electrolytes such as polymer-based solid electrolytes, are preferred as solid electrolytes. By using these solid electrolytes, all-solid-state batteries that do not require an electrolyte can be obtained.

[0193] Examples of sulfide-based solid electrolytes include: Li2S-SiS2-lithium compounds (here, the lithium compound is at least one selected from the group consisting of Li3PO4, LiI and Li4SiO4), Li2S-P2O5, Li2S-B2S5, Li2S-P2S5-GeS2 and other thio-LISICON materials.

[0194] Examples of oxide-based solid electrolytes include Li5La3M2O, an oxide with a garnet-type structure. 12 (M=Nb, Ta), Li7La3Zr2O 12 These are collectively referred to as LISICON, oxyacid salts based on the γ-Li3PO4 structure, perovskite type, and Li, collectively referred to as LIPON. 3.3 PO 3.8 N 0.22 Sodium / aluminum oxide, etc.

[0195] Examples of polymeric solid electrolytes include: polyethylene oxide materials, and polymeric compounds obtained by polymerizing or copolymerizing monomers such as hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, ethylene, propylene, acrylonitrile, vinylidene chloride, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, styrene, and vinylidene fluoride.

[0196] It should be noted that the aforementioned polymeric solid electrolytes may contain supporting salts and plasticizers. Examples of supporting salts include lithium (fluorosulfonylimide). Examples of plasticizers include succinic anionyl nitrile.

[0197] Batteries manufactured using the electrode forming composition of the present invention exhibit superior battery characteristics compared to conventional secondary batteries, even with less binder (e.g., fluoropolymer binder).

[0198] There are no particular restrictions on the form or type of electrolyte of the secondary battery. Any form of secondary battery, such as lithium-ion secondary battery, nickel-metal hydride battery, manganese battery, or air battery, can be used, with lithium-ion secondary battery being preferred.

[0199] There are no particular restrictions on the lamination method or production method of secondary batteries.

[0200] When applied to coin-type batteries, the electrodes of the present invention can be punched into a specified disc shape for use. For example, a lithium-ion secondary battery can be manufactured as follows: an electrode (negative electrode) is provided on a cover with a gasket and spacer welded to it, a separator of the same shape impregnated with electrolyte is overlapped on the electrode, and the electrode (positive electrode) of the present invention is further overlapped from above with the electrode layer facing down, a casing and a gasket are placed, and the battery is sealed with a coin battery riveting machine.

[0201] (Method for manufacturing composition for electrode formation) The method for manufacturing the electrode forming composition of the present invention is a method for manufacturing the electrode forming composition of the present invention.

[0202] The method for manufacturing the electrode forming composition of the present invention includes mixing a specific compound, a binder, a solvent, and a positive electrode active material. There are no particular limitations on the mixing order of these substances.

[0203] One embodiment of the method for manufacturing the electrode forming composition of the present invention includes mixing a specific compound, a binder, a solvent, a polycrystalline first positive electrode active material, and a single-crystal second positive electrode active material. The mixing order of these substances is not particularly limited.

[0204] The mass ratio of the first positive electrode active material to the second positive electrode active material in the electrode forming composition (first positive electrode active material: second positive electrode active material) is not particularly limited, but is preferably 2:8 to 8:2, more preferably 4:6 to 8:2, and particularly preferably 4:6 to 7:3.

[0205] (Additives and gelation inhibitors) The additive of the present invention is an additive for an electrode forming composition comprising a positive electrode active material, a binder, and a solvent.

[0206] The gelation inhibitor of the present invention is a gelation inhibitor of an electrode forming composition comprising a positive electrode active material, a binder, and a solvent. The gelation inhibitor inhibits gelation of the electrode forming composition by adding it to the electrode forming composition comprising the positive electrode active material, the binder, and the solvent.

[0207] The additives and gelation inhibitors are the specific compounds described above. Examples and preferred examples of these compounds can be listed in the description of the specific compounds described above.

[0208] Examples and preferred examples of positive electrode active materials can be cited in the description of the positive electrode active material containing the components of the electrode forming composition of the present invention.

[0209] Examples and preferred examples of adhesives can be cited in the description of the adhesives containing the components of the electrode forming composition of the present invention.

[0210] Examples and preferred examples of solvents can be cited in the description of solvents containing components of the electrode forming composition of the present invention.

[0211] The electrode forming composition using additives and gelation inhibitors may also contain other components. Examples and preferred examples of other components are given in the description of other components contained in the electrode forming composition of the present invention.

[0212] (Methods and applications for inhibiting gelation) The method for inhibiting gelation of the present invention is a method for inhibiting the gelation of an electrode forming composition comprising a positive electrode active material, a binder, and a solvent. In the method for inhibiting gelation, the electrode forming composition is in a state containing a specific compound.

[0213] The use of the present invention is the use of a specific compound for suppressing gelation of an electrode forming composition comprising a positive electrode active material, a binder, and a solvent.

[0214] Examples and preferred examples of specific compounds can be cited as examples and preferred examples listed in the description of the specific compounds above.

[0215] Examples and preferred examples of positive electrode active materials can be cited in the description of the positive electrode active material containing the components of the electrode forming composition of the present invention.

[0216] Examples and preferred examples of adhesives can be cited in the description of the adhesives containing the components of the electrode forming composition of the present invention.

[0217] Examples and preferred examples of solvents can be cited in the description of solvents containing components of the electrode forming composition of the present invention.

[0218] The electrode forming composition used in the method of inhibiting gelation may also contain other components. Examples and preferred examples of other components are given in the description of other components contained in the electrode forming composition of the present invention.

[0219] Example The present invention will be described in more detail below with examples and comparative examples, but the present invention is not limited to the following examples.

[0220] The proton dissociation energy and bond dissociation energy of the additives used in the embodiments and comparative examples of the present invention were calculated by quantum chemical calculations using the following method. As the quantum chemical calculation program, Gaussian 16, a software for molecular orbital calculations manufactured by Gaussian Corporation, was used, and the calculations were performed using the density functional theory (DFT) method.

[0221] [Methods for calculating proton dissociation energy] Using B3LYP as the generalized function and 6-31+G(d) as the basis function, the most stable ground state structure of the target molecule (HA) in vacuum is calculated, and its total energy E(HA) is determined. Furthermore, for the dissociation of a dissociative proton (H) from the target molecule (HA),... ＋ The anion formed by ) (A － Using B3LYP as the functional and 6-31+G(d) as the basis function, calculate its most stable structure in the vacuum ground state and its total energy E(A). － Therefore, the proton dissociation energy ΔE, as defined by equation (a), can be calculated. pd (Unit: kJ / mol).

[0222] (a) ΔE pd = [E(A)] － ) + E(H ＋ )] - E(HA) However, protons (H ＋ Since protons do not have electrons, their total energy cannot be evaluated through quantum chemical calculations. Therefore, the total energy E(H) of a proton here is... ＋ The value of is set to 0 kJ / mol. It should be noted that for a molecule containing protons with multiple dissociation properties, only the first stage of proton dissociation is considered. The total energy E(A) of the anion after proton dissociation is... － The proton dissociation energy is calculated by finding the smallest proton dissociation position.

[0223] [Methods for calculating bond dissociation energy] For a neutral radical (A·) formed by the detachment of a hydrogen radical (H·) from a target molecule, using B3LYP as the functional and 6-31+G(d) as the basis function, its most stable structure in the ground state under vacuum is calculated, and its total energy E(A·) is calculated. Furthermore, for the hydrogen radical (H·), also using B3LYP as the functional and 6-31+G(d) as the basis function, the total energy E(H·) is calculated. Using the value of E(HA) obtained through the calculation of the proton dissociation energy, the bond dissociation energy ΔE, defined by equation (b), is then calculated. bd (Unit: kJ / mol).

[0224] (b) ΔE bd =[E(A·)+E(H·)]-E(HA) It should be noted that the molecule in question has multiple hydrogen atoms, but only hydrogen removal from one site is considered. The bond dissociation energy is calculated for the total energy E(A·) of the neutral free radical obtained through hydrogen removal, which is the smallest removal site.

[0225] The apparatus used in this embodiment is described below.

[0226] (1) Rotation / revolution type mixer: THINKY Corporation, Awatori Rentaro atmospheric pressure type ARE-310.

[0227] (2) Drying chamber: Nihon Spindle Manufacturing Co., Ltd.

[0228] (3) Rheometer (Condition 1): Anton Paar, MCR302, under the conditions of clamp: CP40-1, measurement gap: 0.08 mm, and measurement temperature: 25℃, with one side moving at 0.01→1000 sec. －1 Shear viscosity was measured while scanning the shear rate. The viscosity of the slurry was measured at 100 sec. －1 The value below.

[0229] (4) Rheometer (Condition 2): Anton Paar, MCR302e, under the conditions of fixture: PP50, measurement gap: 0.08 mm, and measurement temperature: 25 °C, with one side moving at 0.01→1000 sec. －1 Shear viscosity was measured while scanning the shear rate. The viscosity of the slurry was measured at 100 sec. －1 The value below.

[0230] (5) Roller press: Takumi Giken Co., Ltd., SA-602.

[0231] (6) X-ray diffraction apparatus: PANaltical, X'Pert Pro MPD.

[0232] [X-ray diffraction measurement] X-ray diffraction patterns of the positive electrode active material were obtained using a CuKα radiation source (45 kV, 40 mA) radiating at a wavelength of 1.5418 Å, collected using an X'Pert Pro MPD (PANaltical). The apparatus consisted of a 0.02 radian Soler slit, a 10 mm irradiation area automatically variable divergence slit, and a 1 / 2° antiscattering slit on the incident side, and an 8 mm antiscattering slit and a 0.02 radian Soler slit on the receiving side. The goniometer radius was 240 mm. In XRD, the diffraction pattern was obtained in the range of 10–100° (2θ) with a step size of 0.013° / scan and a step time of 250 seconds.

[0233] The crystallite size of the positive electrode active material is calculated using the known Scherrer formula, based on the diffraction angle of the peak of the (104) plane obtained from the X-ray diffraction pattern and the full width at half maximum (FWHM) obtained by subtracting the inherent full width at half maximum of the device.

[0234] [Sherlock Formula] τ: Crystalline size (in nm).

[0235] (Crystallite size refers to the average size of a regular (crystalline) domain that can be below the size of crystal grains.)

[0236] K: Scherrer constant (K = 0.9).

[0237] λ: X-ray wavelength (CuKα = 0.15418 nm).

[0238] β: FWHM.

[0239] θ: 1 / 2 of the diffraction angle 2θ of the diffraction peak belonging to the (104) plane.

[0240] At 44.5 ± 1° of the X-ray diffraction pattern, the peak assigned to the (104) plane of the crystal structure with space group R-3m was observed.

[0241] The inherent full width at half maximum (FWHM) of the device is 47.3° obtained using Si powder (NIST, SRM640f).

[0242] The raw materials used in this embodiment are as follows.

[0243] <Positive Electrode Active Material> S-800 is used as the first positive electrode active material in polycrystalline materials. T81RS is used as the second positive electrode active material in single crystal materials.

[0244] S-800: Lithium nickel manganese cobalt oxide (LiNi0.8 Co 0.1 Mn 0.1 O2, polymorphic, manufactured by Ningbo Ronbay New Energy Technology Co., Ltd., Ni ratio: 50% by mass, crystallite size determined by X-ray diffraction: 97 nm.

[0245] T81RS: Lithium nickel manganese cobalt oxide (LiNi 0.8 Co 0.1 Mn 0.1 O2, single crystal, manufactured by Hunan Shanshan Energy Technology Co., Ltd., Ni ratio: 50% by mass, crystallite size determined by X-ray diffraction: 296 nm.

[0246] <Adhesive> Solef-5130: Polyvinylidene fluoride (PVdF), manufactured by Solvay.

[0247] <Conductive additives> AB: DENKA BLACK (registered trademark) Li100 (high purity acetylene black), manufactured by Denka Corporation.

[0248] <Solvent> NMP: N-methyl-2-pyrrolidone, manufactured by Nippon Refine Co., Ltd.

[0249] <Additives A1 to A27 and a1 to a25> Use the additives listed in Tables 1-1 and 1-2 below.

[0250] The additives listed in Table 1-1 are those used in the examples.

[0251] The additives listed in Table 1-2 are those used in the comparative examples.

[0252] Furthermore, the presence or absence of dissociation protons, proton dissociation energies, and bond dissociation energies of these additives are shown in Tables 1-1 and 1-2. Moreover, for additives A1-A27, a1-a12, and a25, a graph is created by plotting the proton dissociation energy on the horizontal axis and the bond dissociation energy on the vertical axis. Figure 1 . The names of the manufacturers listed in Tables 1-1 and 1-2 are as follows.

[0253] Company F: FUJIFILM Wako Pure Chemical Co., Ltd.

[0254] Company T: Tokyo Chemical Industry Co., Ltd.

[0255] Company S: Shin-Etsu Chemical Co., Ltd.

[0256] Company C: NIPPON CARBIDE INDUSTRIES Co., Ltd.

[0257] Company B: BASF

[0258] Company AD: ADEKA Corporation

[0259] Company A: Aldrich

[0260] It should be noted that X-12-1214A (trade name) of A5 is a silane coupling agent with a benzotriazole structure manufactured by Shin-Etsu Chemical Co., Ltd.

[0261] Irganox3114 (trade name) of A-21 is 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione manufactured by BASF Corporation.

[0262] IrganoxMD1024 (trade name) of A-22 is 2',3-bis[[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propanoyl]]propionohydrazide manufactured by BASF Corporation.

[0263] ADK STAB AO-40 (trade name) of A-23 is 6,6'-di-tert-butyl-4,4'-butylidene-bis-m-cresol manufactured by ADEKA Corporation.

[0264] ADK STAB AO-80 (trade name) of A-24 is 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propanoyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5.5]undecane manufactured by ADEKA Corporation

[0265] In addition, the water-soluble hydroxymethylated melamine (Nikaresin S176: trade name) of a7 is a water-soluble hydroxymethylated melamine manufactured by NIPPON CARBIDE INDUSTRIES Co., Ltd.

[0266] · Preparation of the composition for forming a positive electrode (electrode paste) [Examples 1 to 15, Comparative Examples 2 to 25] For each of additives A1 to A15 and additives a1 to a24, a 5% by mass NMP solution (additive solution) was prepared. Next, in a drying chamber, the positive electrode active material, binder powder, conductive additive, additive solution, NMP, and water were mixed using a rotation / revolutionary mixer, with the composition ratios shown in Tables 2-1, 2-3, and 2-4, to obtain the electrode slurry. The total amount of each prepared slurry was 100g, the solid content was set at 73% by mass, and the solvent composition of the slurry was adjusted to NMP / H2O (mass ratio) = 95 / 5. It should be noted that the water was added intentionally to create a slurry with a high water content.

[0267] [Examples 16-19, Comparative Example 26] The positive electrode active material, binder powder, conductive additive, additives, NMP, and water were mixed in a drying chamber using a rotary / revolutionary mixer, with the composition ratios shown in Tables 2-2 and 2-4, to obtain the electrode slurry. The total amount of each slurry was 100g, with a solid content of 73% by mass, and the solvent composition was adjusted to NMP / H2O (mass ratio) = 95 / 5. It should be noted that the water was added intentionally to create a high water content in the slurry.

[0268] [Example 20] Regarding additive A2, a 5% by mass NMP solution (additive solution) was prepared. In a drying chamber, the positive electrode active material, binder powder, conductive additive, additive solution, NMP, and water were mixed using a rotary / revolutionary mixer to achieve the composition ratios shown in Table 2-2, thereby obtaining the electrode slurry. The total amount of the prepared slurry was 100g, with a solid content of 71% by mass, and the solvent composition was adjusted to NMP / H2O (mass ratio) = 95 / 5. It should be noted that the water was added intentionally to create a high water content in the slurry.

[0269] [Example 21] Regarding additive A2, a 5% by mass NMP solution (additive solution) was prepared. In a drying chamber, the positive electrode active material, binder powder, conductive additive, additive solution, NMP, and water were mixed using a rotary / revolutionary mixer to achieve the composition ratios shown in Table 2-2, thereby obtaining the electrode slurry. The total amount of the prepared slurry was 100g, with a solid content of 73.5% by mass, and the solvent composition was adjusted to NMP / H2O (mass ratio) = 95 / 5. It should be noted that the water was added intentionally to create a high water content in the slurry.

[0270] [Examples 22-28] For each of additives A20 to A26, a 5% by mass NMP solution (additive solution) was prepared. Next, in a drying chamber, the positive electrode active material, binder powder, conductive additive, additive solution, NMP, and water were mixed using a rotation / revolutionary mixer to obtain the electrode slurry, with the composition ratios shown in Table 2-2. The total amount of each prepared slurry was 100g, the solid content was set at 73.5% by mass, and the solvent composition of the slurry was adjusted to NMP / H2O (mass ratio) = 98.5 / 1.5. It should be noted that the water was added intentionally to create a slurry with a high water content.

[0271] [Example 29] The positive electrode active material, binder powder, conductive additive, additives, NMP, and water were mixed in a drying chamber using a rotary / revolutionary mixer to obtain the electrode slurry, with the composition ratios shown in Table 2-2. The total amount of the prepared slurry was 100g, the solid content was set at 73.5% by mass, and the solvent composition of the slurry was adjusted to NMP / H2O (mass ratio) = 98.5 / 1.5. It should be noted that the water was added intentionally to create a slurry with a high water content.

[0272] [Comparative Example 1] The positive electrode active material, binder powder, conductive additive, NMP, and water were mixed in a drying chamber using a rotary / revolutionary mixer, with the composition ratios shown in Table 2-3, to obtain the electrode slurry. The total amount of the prepared slurry was 100g, with a solid content of 73% by mass, and the solvent composition was adjusted to NMP / H2O (mass ratio) = 95 / 5. It should be noted that the water was added intentionally to create a slurry with a high water content.

[0273] [Comparative Example 27] The positive electrode active material, binder powder, conductive additive, NMP, and water were mixed in a drying chamber using a rotary / revolutionary mixer to obtain the electrode slurry, with the composition ratios shown in Table 2-4. The total amount of the prepared slurry was 100g, the solid content was set at 71% by mass, and the solvent composition of the slurry was adjusted to NMP / H2O (mass ratio) = 95 / 5. It should be noted that the water was added intentionally to create a slurry with a high water content.

[0274] [Comparative Example 28] The positive electrode active material, binder powder, conductive additive, NMP, and water were mixed in a drying chamber using a rotary / revolutionary mixer, with the composition ratios shown in Table 2-4, to obtain the electrode slurry. The total amount of the prepared slurry was 100g, with a solid content of 73.5% by mass, and the solvent composition was adjusted to NMP / H2O (mass ratio) = 95 / 5. It should be noted that the water was added intentionally to create a slurry with a high water content.

[0275] [Comparative Example 29] The positive electrode active material, binder powder, conductive additive, NMP, and water were mixed in a drying chamber using a rotary / revolutionary mixer to obtain the electrode slurry, with the composition ratios shown in Table 2-4. The total amount of the prepared slurry was 100g, the solid content was set at 73.5% by mass, and the solvent composition of the slurry was adjusted to NMP / H2O (mass ratio) = 98.5 / 1.5. It should be noted that the water was added intentionally to create a slurry with a high water content.

[0276] For the slurries obtained above, viscosity was measured immediately after preparation using a rheometer (condition 1) or a rheometer (condition 2). Furthermore, after storage at 24 hours / 40°C, the presence or absence of gelation was visually confirmed. For cases without gelation, viscosity was similarly measured using a rheometer (condition 1) or a rheometer (condition 2) to confirm the presence or absence of thickening and gelation tendencies, based on the following criteria. Their evaluations are summarized in the tables. It should be noted that the viscosity of Examples 1-21 and Comparative Examples 1-28 was measured using a rheometer (condition 1), while the viscosity of Examples 22-29 and Comparative Example 29 was measured using a rheometer (condition 2).

[0277] [Judgment Criteria] A: The composition is not gelled and can be used for electrode formation.

[0278] B: The composition gels and cannot be used for electrode formation.

[0279] Viscosity change rate (%) = ((viscosity after storage - initial viscosity) / initial viscosity) × 100 The electrode slurries obtained in Examples 1-29 and Comparative Examples 1-29 were uniformly coated onto aluminum foil (15 μm thick, UACJ Corporation) serving as current collectors using a doctor blade. The slurries were dried at 80°C for 30 minutes to form an active material layer. The electrodes were then fabricated by pressing the foil twice at a linear pressure of 0.25 kN / cm, twice at 1 kN / cm, and twice at 3 kN / cm using a roller press. Four 10 mm diameter disc-shaped electrodes were punched from the obtained positive electrode. The mass of the positive electrode layer (the mass of the punched electrode minus the mass of the electrode formed by punching the uncoated portion to a diameter of 10 mm) and the electrode layer thickness (the thickness of the punched electrode minus the thickness of the substrate) were measured. The electrode density was calculated based on their average value. Evaluations are summarized in the tables below. The “-” in the results of “Viscosity change rate (%)” in Tables 2-3 and 2-4 indicates that gelation occurred due to storage at 24 hours / 40°C, and the viscosity after storage at 24 hours / 40°C could not be determined.

[0280] Based on the results in Tables 2-1 to 2-4 above, it was confirmed that in the electrode forming composition of the present invention containing specific additives with a proton dissociation energy of less than 1504.7 (kJ / mol) and a bond dissociation energy of less than 452.61 (kJ / mol), thickening and gelation are suppressed, and storage stability is improved.

[0281] Therefore, even after a period of time has elapsed since the preparation of the electrode forming composition, the coating properties are not impaired, making it a preferred choice for industrial production of lithium-ion secondary batteries.

Claims

1. An electrode forming composition comprising a compound having a cyclic structure and unsaturated bonds, a positive electrode active material, a binder, and a solvent. The compound has protons that can dissociate within the molecule. The proton dissociation energy of the compound is less than 1504.7 kJ / mol. The bond dissociation energy of the compound is less than 452.61 kJ / mol.

2. The composition for forming an electrode according to claim 1, wherein, The positive electrode active material comprises a polycrystalline first positive electrode active material and a single-crystal second positive electrode active material.

3. The composition for forming an electrode according to claim 2, wherein, The first positive electrode active material is a lithium-containing transition metal oxide particle with a layered rock salt structure. The diffraction peak of the lithium-containing transition metal oxide particle based on the (104) plane obtained by X-ray diffraction pattern using CuKα radiation source has a microcrystal size of more than 20 nm and less than 500 nm as determined by the Scherrer formula.

4. The composition for forming an electrode according to claim 2, wherein, The second positive electrode active material is a lithium-containing transition metal oxide particle with a layered rock salt structure. The diffraction peaks of the lithium-containing transition metal oxide particle based on the (104) plane obtained by X-ray diffraction pattern using a CuKα radiation source, and the microcrystal size determined by the Scherrer formula is greater than 50 nm and less than 800 nm.

5. The composition for forming an electrode according to claim 3, wherein, The lithium-containing transition metal oxide particles with a layered rock salt structure in the first positive electrode active material are of the general formula Li. a Ni （1－x－y） Co x M 1 y M 2 z O2 represents crystalline metallic oxide particles, where M is the crystalline metallic oxide particle. 1 It means that at least one of the groups consisting of Mn and Al is selected, M 2 It means that it is selected from at least one of the group consisting of Zr, Ti, Mg, B, W and V, 1.00≤a≤1.50, 0.00≤x≤0.50, 0.00≤y≤0.50, 0.000≤z≤0.

020.

6. The composition for forming an electrode according to claim 4, wherein, The lithium-containing transition metal oxide particles with a layered rock salt structure in the second positive electrode active material are of the general formula Li. a Ni （1－x－y） Co x M 1 y M 2 z O2 represents crystalline metallic oxide particles, where M is the crystalline metallic oxide particle. 1 It means that at least one of the groups consisting of Mn and Al is selected, M 2 It means that it is selected from at least one of the group consisting of Zr, Ti, Mg, B, W and V, 1.00≤a≤1.50, 0.00≤x≤0.50, 0.00≤y≤0.50, 0.000≤z≤0.

020.

7. The composition for forming an electrode according to claim 1, wherein, The ring structure is an aromatic ring.

8. The composition for forming an electrode according to claim 1, wherein, The compound has heteroatoms.

9. The composition for forming an electrode according to claim 1, wherein, The positive electrode active material contains a metal oxide containing Ni.

10. The composition for forming an electrode according to claim 1, wherein, The positive electrode active material contains Ni, and the Ni content in the positive electrode active material is more than 30% by mass and less than 61% by mass.

11. The composition for forming an electrode according to claim 1, wherein, The solvent is an aprotic solvent.

12. The composition for forming an electrode according to claim 1, wherein, The adhesive is a fluorine-based adhesive.

13. The composition for forming an electrode according to claim 1, wherein, The electrode forming composition further comprises a conductive aid.

14. An electrode layer obtained from an electrode forming composition as described in any one of claims 1 to 13.

15. A secondary battery having an electrode layer as described in claim 14.

16. A method for manufacturing an electrode forming composition, comprising manufacturing the electrode forming composition as described in any one of claims 1 to 13, the method comprising: The compound, the binder, the solvent, the polycrystalline first positive electrode active material, and the single-crystal second positive electrode active material are mixed.

17. The method for manufacturing the electrode forming composition according to claim 16, wherein, The mass ratio of the first positive electrode active material to the second positive electrode active material in the electrode forming composition is 2:8 to 8:

2.

18. An additive comprising an electrode-forming composition containing a polycrystalline first positive electrode active material, a single-crystal second positive electrode active material, a binder, and a solvent. The additive has protons that are dissociable within the molecule, with a proton dissociation energy of less than 1504.7 kJ / mol and a bond dissociation energy of less than 452.61 kJ / mol.

19. A gelation inhibitor, comprising a composition for electrode formation containing a polycrystalline first positive electrode active material, a single-crystal second positive electrode active material, a binder, and a solvent. The gelation inhibitor has a proton with dissociative properties within the molecule, with a proton dissociation energy of less than 1504.7 kJ / mol and a bond dissociation energy of less than 452.61 kJ / mol.

20. A method for inhibiting gelation, comprising an electrode forming composition including a polycrystalline first positive electrode active material, a single-crystal second positive electrode active material, a binder, and a solvent. The electrode forming composition is in a state containing a compound having a proton that is dissociable within the molecule, the proton dissociation energy being less than 1504.7 kJ / mol and the bond dissociation energy being less than 452.61 kJ / mol.

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