Electrode composition, electrode for secondary battery, secondary battery, electrolyte permeation method, and method for producing secondary battery

Abstract

This electrode composition is for a secondary battery electrode layer and comprises an electrolytic solution. The electrode composition satisfies all of criteria (1) through (4): (1) the composition contains an active substance and an additive but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active substance is 12.0 MPa0.5 or less; (3) the HSP distance (Ra_Elec) between the additive and the electrolytic solution is 14.0 MPa0.5 or less; and (4) the weight average molecular weight (Mw) of the additive is 50,000 or less.

Description

Electrode composition, electrode for secondary battery, secondary battery, electrolyte penetration method, and method for manufacturing secondary battery

[0001] The present invention relates to an electrode composition, an electrode for a secondary battery, a secondary battery, an electrolyte penetration method, and a method for producing a secondary battery.

[0002] Secondary batteries such as lithium-ion batteries are being used in practical applications such as mobile phones, laptop computers, and other portable devices, as well as in hybrid and electric vehicles. To further popularize these devices, there is a demand for higher capacity and power output secondary batteries, and various technologies are being developed to address this demand.

[0003] One way to improve the capacity of secondary batteries is to increase electrode density. By densely packing the active material, more capacity can be obtained. However, increasing electrode density makes it difficult for the electrolyte to penetrate the electrode, resulting in problems such as less capacity than the theoretical value and a deterioration in output characteristics.

[0004] To solve these problems, Patent Document 1 discloses a technique for improving electrolyte permeability by providing grooves on the electrode surface. Patent Document 2 discloses a technique for improving electrolyte permeability by adjusting the particle size and shape of the active material. Furthermore, Patent Document 3 discloses a technique for improving electrolyte permeability by adjusting the electrode density.

[0005] JP 2008-27633 A JP 2012-151088 A JP 2020-053282 A

[0006] However, the method of Patent Document 1 involves a step of pressing the electrode surface with a roller having an uneven surface to form grooves, which necessitates the introduction of new equipment, and while the methods of Patent Documents 2 and 3 show some improvement in permeability, the effect is not sufficient.

[0007] The present invention has been made to solve the above problems, and an object of the present invention is to provide an electrode composition that can be used to produce an electrode having excellent electrolyte permeability.

[0008] The present inventors have arrived at the present invention as a result of extensive research. The present invention relates to any one of the following: An electrode composition for a secondary battery electrode layer containing an electrolytic solution, the electrode composition satisfying all of the following (1) to (4): (1) containing an active material and an additive, but not containing a binder resin; (2) an HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa or less; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

[0009] An electrode composition for a secondary battery electrode layer containing an electrolytic solution, the electrode composition satisfying all of the following (1) to (3): (1) containing an active material, a binder resin, and an additive; (2) an HSP distance (Ra_Act) between the additive and the active material of 12.0 MPa or less; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

[0010] A secondary battery electrode formed by compression molding the electrode composition. A secondary battery comprising the secondary battery electrode.

[0011] A secondary battery including a current collector layer, a secondary battery electrode layer, and a separator layer, which satisfies all of the following (1) to (4): (1) the secondary battery electrode layer contains an active material, an electrolyte solution, and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa. ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

[0012] A secondary battery including a current collector layer, a secondary battery electrode layer, and a separator layer, which satisfies all of the following (1) to (3): (1) the secondary battery electrode layer contains an active material, an electrolyte, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa. ０．５(3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

[0013] A method for permeating an electrode composition with an electrolyte solution, the method satisfying all of the following (1) to (4): (1) the electrode composition contains an active material and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa or less; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

[0014] A method for permeating an electrode composition with an electrolyte solution, the method satisfying all of the following (1) to (3): (1) the electrode composition contains an active material, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa or less; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

[0015] A method for producing a secondary battery, comprising the steps of: permeating an electrolytic solution into a battery unit including a current collector layer, an electrode composition layer, and a separator layer, to obtain a secondary battery electrode layer in which the electrolytic solution is contained in the electrode composition layer, the method comprising the steps of: (1) producing a secondary battery that satisfies all of the following (1) to (4): (1) the electrode composition layer contains an active material and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

[0016] A method for producing a secondary battery, comprising the steps of: permeating an electrolytic solution into a battery unit including a current collector layer, an electrode composition layer, and a separator layer, to obtain a secondary battery electrode layer in which the electrolytic solution is contained in the electrode composition layer, the method comprising the steps of: (1) producing a secondary battery that satisfies all of the following (1) to (3): (1) the electrode composition layer contains an active material, a binder resin, and an additive; and (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa. ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

[0017] According to the present invention, it is possible to provide an electrode composition that can be used to produce an electrode having excellent electrolyte permeability.

[0018] [Electrode Composition] The electrode composition of the present invention includes a first type electrode composition and a second type electrode composition. The first type electrode composition is an electrode composition for a secondary battery electrode layer containing an electrolytic solution, and satisfies all of the following (1) to (4): (1) it contains an active material and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

[0019] The electrode composition of the second embodiment is an electrode composition for a secondary battery electrode layer containing an electrolytic solution, and satisfies all of the following (1) to (3): (1) it contains an active material, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

[0020] The electrode composition of the first type and the electrode composition of the second type differ in the following respects, but are otherwise common to both. The electrode composition of the first type does not contain a binder resin in (1). The electrode composition of the second type contains a binder resin in (1). The electrode composition of the first type is specified to have the weight average molecular weight (Mw) of the additive in (4) be 50,000 or less, but the electrode composition of the second type does not have this requirement. Below, we will explain the points common to the electrode compositions of the first and second types.

[0021] The electrode composition of the present invention is an electrode composition for a secondary battery electrode layer containing an electrolytic solution. The electrode composition of the present invention does not itself contain an electrolytic solution, but by adding an electrolytic solution to the electrode composition, it can be used to form a secondary battery electrode layer. The electrode composition contains an active material and an additive.

[0022] (Active Material) The active material may be a positive electrode active material or a negative electrode active material.

[0023] The positive electrode active material is a composite oxide of lithium and a transition metal {composite oxide containing one type of transition metal (LiCoO ２ , LiNiO ２ , LiAlMnO ４ , LiMnO ２ and LiMn ２ O ４ etc.), composite oxides containing two transition metal elements (e.g., LiFeMnO ４ , LiNi １－ｘ Co ｘ O ２ , LiMn １－ｙ Co ｙ O ２ , LiNi １／３ Co １／３ Al １／３ O ２ and LiNi ０．８ Co ０．１５ Al ０．０５ O ２ ) and composite oxides containing three or more transition metal elements [e.g., LiM ａ M' ｂ M'' ｃ O ２(M, M', and M'' are different transition metal elements, and a + b + c = 1 is satisfied. For example, LiNi ０．８ Co ０．１ Mn ０．１ O ２ , LiNi １／３ Mn １／３ Co １／３ O ２ ) etc.}, lithium-containing transition metal phosphates (e.g., LiFePO ４ , LiCoPO ４ , LiMnPO ４ and LiNiPO ４ ), transition metal oxides (e.g., MnO ２ and V ２ O ５ ), transition metal sulfides (e.g., MoS ２ and TiS ２ ) and conductive polymers (for example, polyaniline, polypyrrole, polythiophene, polyacetylene, poly-p-phenylene, and polyvinylcarbazole), and two or more of them may be used in combination. Note that the lithium-containing transition metal phosphate may be one in which part of the transition metal site is substituted with another transition metal.

[0024] Examples of the negative electrode active material include carbon-based materials [graphite (graphite, artificial graphite, natural graphite), non-graphitizable carbon (hard carbon), amorphous carbon, burned resins (e.g., phenolic resins, furan resins, etc., which are burned and carbonized), cokes (e.g., pitch coke, needle coke, petroleum coke, etc.), and carbon fibers], silicon-based materials [silicon, silicon oxide (SiO ｘ), silicon-carbon composites (carbon particles whose surfaces are coated with silicon and / or silicon carbide, silicon particles or silicon oxide particles whose surfaces are coated with carbon and / or silicon carbide, and silicon carbide, etc.) and silicon alloys (silicon-aluminum alloys, silicon-lithium alloys, silicon-nickel alloys, silicon-iron alloys, silicon-titanium alloys, silicon-manganese alloys, silicon-copper alloys, silicon-tin alloys, etc.), conductive polymers (e.g., polyacetylene and polypyrrole), metals (tin, aluminum, zirconium, titanium, etc.), metal oxides (titanium oxide and lithium-titanium oxide, etc.), metal alloys (e.g., lithium-tin alloys, lithium-aluminum alloys, lithium-aluminum-manganese alloys, etc.), and mixtures of these with carbon-based materials. When the electrode active material is a negative electrode active material, artificial graphite or natural graphite is preferably used as the negative electrode active material. When the negative electrode active material is graphite, the shape is not particularly limited, and examples include spherical graphite and scaly graphite.

[0025] The content of the active material in the electrode composition is not particularly limited, but from the viewpoint of increasing the electrode density and battery capacity, a high content of the active material is preferred, and a content of 90 to 95% by weight is preferred.

[0026] (Additive) The additive is a compound that satisfies the following conditions: (2) The HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa. ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less. ０．５ The electrode composition of the first embodiment further satisfies the condition "(4) the weight average molecular weight (Mw) of the additive is 50,000 or less," which will be described later.

[0027] The HSP distance is determined from the Hansen solubility parameter (HSP value) for two substances for which the HSP distance is to be determined. The HSP value is an index that takes into account the polarity of physical properties by dividing the Hildebrand solubility parameter (SP value) into three components: the dispersion force term δD, the polar term δP, and the hydrogen bond term δH. ２ = δD ２ +δP ２ +δH ２The HSP distance between two substances is expressed by the following formula, where δD, δP, and δH of the two substances are (δD1, δP1, δH1) and (δD2, δP2, δH2), respectively. HSP distance = SQRT(4 x (δD1 - δD2) ２ + (δP1-δP2) ２ + (δH1-δH2) ２ ) HSP distance refers to the distance between two points when the HSP value is considered as a coordinate in three-dimensional space, and the smaller the HSP distance (the closer the HSP values ​​are), the more easily the two substances will dissolve.

[0028] The HSP value of a substance can be calculated by inputting the structural formula into HSPiP (Hansen Solubility Parameters in Practice) software. Alternatively, values ​​in the HSPiP database or literature values ​​may be used.

[0029] In addition to these methods, HSP values ​​can also be determined experimentally. A target component is dispersed in a solvent with a known HSP value, and the dispersibility of the component in that specific solvent is evaluated. To evaluate dispersibility, the target component for which HSP is to be determined is dispersed in the solvent, the absorption spectrum is measured, and the absorbance values ​​are recorded at 10-second intervals for 20 minutes (measurement wavelength: 632 nm). The dispersion index (DISP) is calculated by dividing the absorbance at 20 minutes by the absorbance at the start of measurement. The obtained dispersion index is used to evaluate dispersibility in each solvent based on the following evaluation criteria: 1: DISP = 0.30 or more; 2: DISP = 0.20 or more but less than 0.30; 3: DISP = 0.15 or more but less than 0.20; 4: DISP = 0.10 or more but less than 0.15; 5: DISP = less than 0.10. The HSP value of the target component can be calculated by inputting the evaluation results of dispersibility in each solvent into HSPiP.

[0030] The solvent used in the method for determining the HSP value may be any of toluene, N-methylpyrrolidone (NMP), diethyl carbonate, dimethylformamide, 1,4-dioxane, hexane, cyclohexane, methanol, ethanol, acetone, acetonitrile, methyl ethyl ketone (MEK), and the like.

[0031] The HSP values ​​of the active material and additive constituting the electrode composition are determined, and the HSP distance between the additive and the active material is determined from the HSP values ​​(more precisely, δD, δP, and δH of the active material and additive, respectively). The electrode composition of the present invention has an HSP distance (Ra_Act) between the additive and the active material of 12.0 MPa. ０．５ The HSP distance between the additive and the active material is 4.0 MPa. ０．５ It is preferable that the HSP distance between the additive and the active material is 4.0 MPa or more. ０．５ If the HSP distance is less than 1 / 2 mm (if the HSP distance between the additive and the active material is small), the compatibility between the additive and the active material is high, so that the surface of the active material is corroded by the additive, and the electrode layer may become brittle when formed into an electrode layer.

[0032] Although the electrolyte is not a component of the electrode composition, the electrode composition contains the electrolyte and is used as a secondary battery electrode layer, and the HSP distance between the additive and the electrolyte is determined in relation to the electrolyte contained in the electrode composition. The HSP values ​​of the additive and the electrolyte are determined, and the HSP distance between the additive and the electrolyte is calculated from the HSP values ​​(more precisely, δD, δP, and δH of the additive and the electrolyte, respectively). The electrode composition of the present invention has a (Ra_Elec) between the additive and the electrolyte of 14.0 MPa. ０．５ The HSP distance between the additive and the electrolyte is 12.0 MPa. ０．５ The lower limit of the HSP distance between the additive and the electrolyte is not particularly limited, but is preferably 1.0 MPa or less. ０．５ It is preferable that this is equal to or greater than this.

[0033] The additive is not particularly limited as long as it is a compound that can satisfy the requirements (2) and (3) regarding the HSP distance, and specific examples include the following compounds: (A1) Alkylene oxide adduct of alkyl alcohol (A2) Alkylene oxide adduct of alkylene glycol (A3) Glycol ethers (A4) Alkylene oxide adduct of bisphenols (A5) Ester compounds (A6) Amine compounds (A7) Alcohols

[0034] (A1) Alkylene oxide adduct of alkyl alcohol The alkylene oxide preferably contains ethylene oxide. The alkylene oxide may also contain alkylene oxides other than ethylene oxide. Examples of alkylene oxides other than ethylene oxide include propylene oxide and butylene oxide. Hereinafter, alkylene oxide may be abbreviated as AO, ethylene oxide as EO, propylene oxide as PO, and butylene oxide as BO.

[0035] The alkylene oxide may be a combination of ethylene oxide and propylene oxide, a combination of ethylene oxide and butylene oxide, or a combination of ethylene oxide, propylene oxide and butylene oxide. When the alkylene oxide is composed of multiple types of alkylene oxides, the addition form may be random addition or block addition.

[0036] The molar ratio of ethylene oxide in the alkylene oxide is preferably 85% or more based on the total number of moles of alkylene oxide. The alkylene oxide may consist solely of ethylene oxide. That is, the molar ratio of ethylene oxide in the alkylene oxide may be 100% based on the total number of moles of alkylene oxide. The molar ratio of ethylene oxide in the alkylene oxide may be 85 to 100%, 87 to 100%, 92 to 100%, 85 to 87%, 85 to 92%, or 87 to 92%.

[0037] The average number of moles of alkylene oxide added in the alkylene oxide adduct of alkyl alcohol is preferably 2 to 40. The average number of moles of alkylene oxide added may be 3 to 20, or may be 4 to 10. When there are multiple types of alkylene oxides, the number of moles of alkylene oxide added is the total number of moles of the multiple types of alkylene oxides added.

[0038] The alkyl alcohol constituting the alkylene oxide adduct of alkyl alcohol is preferably a saturated alkyl alcohol from the viewpoint of suppressing deterioration of battery performance due to side reactions that may occur during charging and discharging. The alkyl group of the alkyl alcohol may be linear or branched.

[0039] The number of carbon atoms in the alkyl group of the alkyl alcohol is not particularly limited, and is preferably 1 to 20. Examples of alkyl alcohols having 1 to 20 carbon atoms include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, 2-ethylhexanol, isodecanol, and isotridecanol.

[0040] Specific examples of alkylene oxide adducts of alkyl alcohols include heptaethylene glycol monoisodecyl ether, tetraethylene glycol monopentadecyl ether, nonaethylene glycol monododecyl ether, and nonaethylene glycol monomethyl ether.

[0041] (A2) Alkylene oxide adduct of alkylene glycol The alkylene oxide can be the same as (A1), and the addition method and combination of alkylene oxides can be the same as (A1). The molar ratio of ethylene oxide in the alkylene oxide is preferably 85% or more based on the total number of moles of alkylene oxide. The alkylene oxide may be ethylene oxide alone. That is, the molar ratio of ethylene oxide in the alkylene oxide may be 100% based on the total number of moles of alkylene oxide. The alkylene glycol is preferably ethylene glycol, and is preferably an ethylene oxide adduct of ethylene glycol (polyethylene glycol).

[0042] The average number of moles of alkylene oxide added in the alkylene oxide adduct of alkylene glycol is preferably 2 to 40. The average number of moles of alkylene oxide added may be 3 to 20, or may be 4 to 10. Specific examples of the alkylene oxide adduct of alkylene glycol include tetraethylene glycol (number of moles of ethylene oxide added: 4), octaethylene glycol (number of moles of ethylene oxide added: 8), and heptapropylene glycol (number of moles of propylene oxide added: 7).

[0043] (A3) Glycol Ethers The alkylene glycol unit in the glycol ethers is preferably ethylene glycol or propylene glycol, and more preferably ethylene glycol. The number of repeating alkylene glycol units is preferably 3 to 20, and may be 4 to 15. Specific examples of glycol ethers include triethylene glycol dimethyl ether, hexaethylene glycol tribenzyl phenyl ether, and tetradecaethylene glycol tribenzyl phenyl ether.

[0044] (A4) Alkylene oxide adduct of bisphenols These are compounds obtained by adding alkylene oxide to bisphenols. The alkylene oxides that can be used are the same as those in (A1), and the addition method and combination of alkylene oxides can also be the same as those in (A1). Examples include EO adducts of bisphenol A, PO adducts of bisphenol A, and BO adducts of bisphenol A. The average number of moles of alkylene oxide added may be 1 to 20, or 1 to 5. A specific example of an alkylene oxide adduct of bisphenols is an EO 2-mol adduct of bisphenol A.

[0045] (A5) Ester Compounds These include carboxylic acid esters, phosphate esters, etc., and examples thereof include monoesters, diesters, triesters, etc. Specific examples of the ester compounds include methyl n-octanoate, methyl tetradecanoate, glycerin stearate, and phosphate triesters (such as tris(2-chloro-1-methylethyl)phosphate).

[0046] (A6) Amine Compounds Examples of the amine compounds include saturated cyclic monoamines (for example, alicyclic amines (monoamines containing a saturated cyclic hydrocarbon group) {e.g., cyclobutylamine, cyclopentylamine, cyclohexylamine, cycloheptylamine, dicyclohexylamine, N-methylcyclohexylamine, trimethylcyclohexylamine, aminomethylcyclohexane, 1-cyclohexylethylamine, etc.}, saturated heterocyclic monoamines {e.g., morpholine, piperidine, etc.}, and unsaturated cyclic monoamines (monoamines containing an unsaturated cyclic hydrocarbon group) (e.g., aromatic amines {e.g., aniline, anisidine, toluidine, trimethylaniline, etc.}, unsaturated heterocyclic monoamines {e.g., pyrrole, azepine, azonine, etc.}). Of these, cyclohexylamine is preferred.

[0047] (A7) Alcohols Examples of alcohols include aliphatic alcohols, aromatic alcohols, and aromatic aliphatic alcohols. Aliphatic alcohols are preferred, and the number of carbon atoms in the aliphatic group moiety is not particularly limited, but may be 1 to 20, or may be 10 to 20. A specific example of the alcohol is hexadecanol.

[0048] The content of the additive is preferably 0.001 to 2% by weight based on the weight of the electrode composition, and when the content of the additive is in this range, the effect of including the additive can be more suitably exhibited.

[0049] (Electrolyte) As the electrolyte, an electrolyte for a secondary battery can be used, and an electrolyte containing a non-aqueous solvent that can be used in a lithium ion battery can be preferably used. The electrolyte has an HSP distance (Ra_Elec) of 14.0 MPa with respect to the additive contained in the electrode composition. ０．５ Use the following:

[0050] The solvent contained in the electrolytic solution can be a non-aqueous solvent used in known electrolytic solutions, such as a lactone compound, a cyclic or chain carbonate ester, a chain carboxylic acid ester, a cyclic or chain ether, a phosphate ester, a nitrile compound, an amide compound, a sulfone, a sulfolane, or a mixture thereof.

[0051] Examples of lactone compounds include lactone compounds having a five-membered ring (such as γ-butyrolactone and γ-valerolactone) and a six-membered ring (such as δ-valerolactone).

[0052] Examples of cyclic carbonates include propylene carbonate (PC), ethylene carbonate (EC), and butylene carbonate (BC). Examples of chain carbonates include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate.

[0053] Examples of the chain carboxylic acid ester include methyl acetate, ethyl acetate, propyl acetate, and methyl propionate.

[0054] Examples of cyclic ethers include tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, and 1,4-dioxane. Examples of chain ethers include dimethoxymethane and 1,2-dimethoxyethane.

[0055] Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, ethyl dimethyl phosphate, diethylmethyl phosphate, tripropyl phosphate, tributyl phosphate, tri(trifluoromethyl phosphate), tri(trichloromethyl phosphate), tri(trifluoroethyl phosphate), 2-ethoxy-1,3,2-dioxaphospholan-2-one, 2-trifluoroethoxy-1,3,2-dioxaphospholan-2-one, and 2-methoxyethoxy-1,3,2-dioxaphospholan-2-one.

[0056] Examples of nitrile compounds include acetonitrile, etc. Examples of amide compounds include DMF, etc. Examples of sulfones include dimethyl sulfone and diethyl sulfone, etc.

[0057] These solvents may be used alone or in combination of two or more. The mixed solvent is preferably a mixed solvent of ethylene carbonate and diethyl carbonate, a mixed solvent of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate, or a mixed solvent of ethylene carbonate and propylene carbonate.

[0058] The electrolyte contained in the electrolytic solution may be any electrolyte used in known electrolytic solutions, such as LiPF ６ , LiBF ４ , LiSbF ６ , LiAsF ６ , LiClO ４ and LiN(FSO ２ ) ２ Lithium salts of inorganic anions such as LiN(CF ３ SO ２ ) ２ , LiN(C ２ F ５ SO ２ ) ２ and LiC(CF ３ SO ２ ) ３ Among these, LiPF ６ (lithium hexafluorophosphate), LiFSI (lithium bis(fluorosulfonyl)imide), etc. can be preferably used.

[0059] The concentration of the electrolyte in the electrolytic solution is not particularly limited, but is preferably 0.3 to 5.0 mol / L, more preferably 0.5 to 2.0 mol / L, and even more preferably 0.8 to 1.5 mol / L.

[0060] Since the HSP value of an electrolyte solution largely depends on the type of solvent, the HSP value can be calculated based on the type of solvent without considering the influence of the electrolyte. When a mixed solvent is used as the solvent, the average of the HSP values ​​of each solvent (δD, δP, and δH) based on the volume ratio of each solvent is used as each term of the HSP value of the mixed solvent.

[0061] (Binder Resin) The electrode composition of the first type does not contain a binder resin, while the electrode composition of the second type contains a binder resin. The binder resin will be described below. Substances that can be used as additives may include substances known as binder resins, but in this specification, binder resins are substances that are distinguished from additives.

[0062] Binder resins are resins used in lithium-ion batteries, and examples thereof include starch, polyvinylidene fluoride, polyvinyl alcohol, polyvinylpyrrolidone, polytetrafluoroethylene, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyethylene, and polypropylene. When an electrode composition contains these substances, it is considered to contain a binder resin. Furthermore, these substances are not included in the additives of the present invention, even if the relationship between the HSP distance from the active material and the HSP distance from the electrolyte satisfies the requirements of the present invention.

[0063] Furthermore, many binder resins have a weight-average molecular weight (Mw) exceeding 50,000. From this perspective, the first type of electrode composition, which does not contain a binder resin, is specified to satisfy the requirement of "(4) the weight-average molecular weight (Mw) of the additive is 50,000 or less." The weight-average molecular weight of the additive may be a molecular weight determined based on the structural formula of the additive, and when determined by measurement, it can be measured by gel permeation chromatography under the following conditions, for example. Apparatus: "Waters Alliance 2695" [manufactured by Waters] Column: "Guard column Super H-L" (1 column), "TSKgel Super H2000, TSKgel Super H3000, TSKgel Super H4000 (all manufactured by Tosoh Corporation) connected together (1 column each)" Sample solution: 0.25 wt% tetrahydrofuran solution Solution injection amount: 10 μl Flow rate: 0.6 ml / min Measurement temperature: 40°C Detector: refractive index detector Reference material: standard polyethylene glycol

[0064] On the other hand, since the electrode composition of the second embodiment is specified to contain a binder resin, it may contain a substance having a weight-average molecular weight of more than 50,000. When the electrode composition contains a binder resin, the content of the binder resin is preferably more than 0 wt % and not more than 6.0 wt % based on the weight of the electrode composition.

[0065] The electrode composition of the present invention may contain a conductive additive. Examples of the conductive additive include metals (aluminum, stainless steel (SUS), silver, gold, copper, titanium, etc.), carbon (graphite (flaky graphite (UP)), carbon black (acetylene black, ketjen black, furnace black, channel black, thermal lamp black, etc.), and carbon nanofibers (CNF), etc.), and mixtures thereof. Acetylene black is preferred as the conductive additive. Note that carbon-based materials are used as both negative electrode active materials and conductive additives. In this application, materials with a volume average particle diameter of 10.0 μm or more are considered negative electrode active materials, and materials with a volume average particle diameter of less than 10.0 μm are considered conductive additives.

[0066] The electrode composition of the present invention has an HSP distance between the active material and the additive of 12.0 MPa. ０．５ Since the HSP distance between the additive and the electrolyte is 14.0 MPa or less, the active material and the additive have good compatibility, and the surface of the active material is in a state where it is surface-treated with the additive. ０．５ The following is a description of the conditions, which stipulate that the additive and the electrolyte have a good compatibility relationship. Therefore, the electrolyte can easily penetrate into the electrode composition. Therefore, the electrode composition of the present invention is an electrode composition that can be used to produce electrodes with excellent electrolyte permeability. Furthermore, the electrode composition of the present invention has excellent electrolyte permeability even when the electrode density is increased, and therefore is an electrode composition that can be used to produce high-energy density electrodes without reducing production capacity.

[0067] Furthermore, the HSP distance between the active material and the additive is 4.0 MPa. ０．５ If the above is the case, an electrode composition can be obtained that can produce an electrode having good properties in terms of electrode brittleness.

[0068] [Secondary Battery Electrode and Secondary Battery] The secondary battery electrode of the present invention is an electrode for a secondary battery obtained by compression molding the electrode composition of the present invention. As the electrode composition of the present invention, either the electrode composition of the first form or the electrode composition of the second form may be used. The method for compression molding the electrode composition is not particularly limited, but methods such as roll pressing and pressing with a press machine can be used. The electrode density of the secondary battery electrode obtained by compression molding the electrode composition is 1.0 to 2.0 g / cm ３ It is preferable that the electrode density defined here means the density in a state where the electrolyte solution has not been impregnated into the electrode composition. Furthermore, a secondary battery comprising the above-described secondary battery electrode of the present invention is also the secondary battery of the present invention. In this secondary battery of the present invention, the configuration other than that of the secondary battery electrode of the present invention is not particularly limited.

[0069] [Secondary Battery] The secondary battery of the present invention includes the secondary battery including the secondary battery electrode of the present invention described above, as well as the following first and second types of secondary batteries. The first type of secondary battery corresponds to the electrode composition of the first type, and the second type of secondary battery corresponds to the electrode composition of the second type.

[0070] The secondary battery of the first embodiment is a secondary battery including a current collector layer, a secondary battery electrode layer, and a separator layer, and satisfies all of the following (1) to (4): (1) the secondary battery electrode layer contains an active material, an electrolyte solution, and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

[0071] The secondary battery of the second embodiment is a secondary battery including a current collector layer, a secondary battery electrode layer, and a separator layer, and satisfies all of the following (1) to (3): (1) the secondary battery electrode layer contains an active material, an electrolyte, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

[0072] The above-mentioned provisions (2) to (4) in the secondary batteries of the first and second embodiments are the same as the provisions (2) to (4) in the electrode composition of the present invention. The secondary batteries of the first and second embodiments include a secondary battery electrode layer. In (1), it is specified that the secondary battery electrode layer contains an electrolytic solution.

[0073] The secondary battery electrode layer is a layer containing an electrolyte solution in the electrode composition of the first and second embodiments. The secondary battery electrode layer can contain a sufficient amount of electrolyte solution in a short time due to the good electrolyte solution permeability of the electrode composition of the first and second embodiments. Because the secondary battery electrode layer can contain a sufficient amount of electrolyte solution in a short time, the secondary batteries of the first and second embodiments can be produced in a short time and can extract a capacity close to the theoretical value.

[0074] Other components of the secondary battery than the secondary battery electrode layer include a current collector layer and a separator layer. As the current collector layer and separator layer, a current collector and separator that can be used in a typical lithium ion secondary battery can be used.

[0075] The secondary battery of the present invention can be used as a secondary battery for use in mobile phones, personal computers, hybrid vehicles, electric vehicles, stationary power sources, and the like.

[0076] [Electrolyte Solution Penetration Method] The electrolyte solution penetration method of the present invention includes the following first and second embodiments. The first embodiment corresponds to the method of penetrating an electrolyte solution into the electrode composition of the first embodiment, and the second embodiment corresponds to the method of penetrating an electrolyte solution into the electrode composition of the second embodiment.

[0077] The first embodiment of the electrolyte solution penetration method is a method of permeating an electrode composition with an electrolyte solution, and is an electrolyte solution penetration method that satisfies all of the following (1) to (4): (1) the electrode composition contains an active material and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

[0078] The second embodiment of the electrolyte solution penetration method is a method of permeating an electrode composition with an electrolyte solution, and satisfies all of the following requirements (1) to (3): (1) the electrode composition contains an active material, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

[0079] In any of the electrolyte solution penetration methods, the means for penetrating the electrode composition with the electrolyte solution is not particularly limited, and any one of a spray coater, a dispenser, a die coater, and a roll coater may be used. Alternatively, after assembling the components constituting the battery, such as the electrode composition, the current collector, and the separator, and sealing them with a sealing member, the electrolyte solution may be injected into the electrode composition through an injection port provided in the sealing member, thereby penetrating the electrode composition with the electrolyte solution.

[0080] In the electrolyte solution penetration method of the present invention, since the electrolyte solution permeability into the electrode composition is good, the work of impregnating the electrode composition with the electrolyte can be completed in a short time, and the workability when obtaining a secondary battery electrode layer is good. The work time (penetration time) for impregnating the electrode composition with the electrolyte solution varies depending on the type of electrolyte solution, the size of the secondary battery, etc., but can be, for example, 300 minutes or less.

[0081] [Method for manufacturing secondary battery] The method for manufacturing a secondary battery of the present invention includes a first embodiment of a method for manufacturing a secondary battery and a second embodiment of a method for manufacturing a secondary battery. The first embodiment of a method for manufacturing a secondary battery corresponds to the method for manufacturing a secondary battery by permeating an electrolyte solution into the electrode composition of the first embodiment, and the second embodiment of an electrolyte solution permeation method corresponds to the method for manufacturing a secondary battery by permeating an electrolyte solution into the electrode composition of the second embodiment.

[0082] A first embodiment of the method for producing a secondary battery includes a step of permeating an electrolytic solution into a battery unit including a current collector layer, an electrode composition layer, and a separator layer to obtain a secondary battery electrode layer in which the electrolytic solution is contained in the electrode composition layer, and the method for producing a secondary battery satisfies all of the following (1) to (4): (1) the electrode composition layer contains an active material and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

[0083] A second embodiment of the method for producing a secondary battery includes a step of permeating an electrolytic solution into a battery unit including a current collector layer, an electrode composition layer, and a separator layer to obtain a secondary battery electrode layer in which the electrolytic solution is contained in the electrode composition layer, and the method for producing a secondary battery satisfies all of the following (1) to (3): (1) the electrode composition layer contains an active material, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

[0084] In any of the methods for manufacturing a secondary battery, the means for permeating the battery unit including the electrode composition layer with the electrolyte solution is not particularly limited, and any one of a spray coater, a dispenser, a die coater, and a roll coater may be used. When permeating the battery unit with the electrolyte solution, the electrode composition may be permeated with the electrolyte solution to form a secondary battery electrode layer, and then the current collector layer and the separator layer may be combined to form a battery unit including the secondary battery electrode layer. Alternatively, the current collector layer, the electrode composition layer, and the separator layer may be combined, and then the electrode composition layer may be permeated with the electrolyte solution to form a secondary battery electrode layer, to form a battery unit including the secondary battery electrode layer.

[0085] In the method for producing a secondary battery of the present invention, since the electrolyte permeability into the electrode composition is good, the work of permeating the electrolyte into the electrode composition can be completed in a short time, and the workability when obtaining a secondary battery electrode layer is good. The work time (permeation time) for permeating the electrolyte into the electrode composition varies depending on the type of electrolyte, the size of the secondary battery, etc., but can be, for example, 300 minutes or less.

[0086] The present specification discloses the following:

[0087] The present disclosure (1) provides an electrode composition for a secondary battery electrode layer containing an electrolytic solution, which satisfies all of the following (1) to (4): (1) contains an active material and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa.０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

[0088] The present disclosure (2) provides an electrode composition for a secondary battery electrode layer containing an electrolytic solution, which satisfies all of the following (1) to (3): (1) the electrode composition contains an active material, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

[0089] In the present disclosure (3), the HSP distance (Ra_Act) between the additive and the active material is 4.0 MPa. ０．５ The electrode composition according to the present disclosure (1) or (2) is as described above.

[0090] The present disclosure (4) is a method for manufacturing a battery in which the HSP distance (Ra_Elec) between the additive and the electrolyte is 12.0 MPa. ０．５ The electrode composition is described in any one of the following (1) to (3) of the present disclosure.

[0091] The present disclosure (5) is the electrode composition according to any one of the present disclosures (1) to (4), wherein the additive is an alkylene oxide adduct of an alkyl alcohol or an alkylene oxide adduct of an alkylene glycol.

[0092] The present disclosure (6) is the electrode composition according to the present disclosure (5), wherein the alkyl alcohol is a saturated alkyl alcohol.

[0093] The present disclosure (7) is the electrode composition according to any one of the present disclosures (1) to (6), wherein the active material is at least one selected from the group consisting of a composite oxide containing at least one transition metal element, artificial graphite, and natural graphite.

[0094] The present disclosure (8) is the electrode composition according to any one of the present disclosures (1) to (7), wherein the solvent of the electrolyte solution is a mixed solvent of ethylene carbonate and diethyl carbonate, a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate, or a mixed solvent of ethylene carbonate and propylene carbonate.

[0095] The present disclosure (9) is an electrode for a secondary battery obtained by compression molding the electrode composition according to any one of the present disclosures (1) to (8).

[0096] The present disclosure (10) is a secondary battery including the electrode for a secondary battery according to the present disclosure (9).

[0097] The present disclosure (11) is a secondary battery including a current collector layer, a secondary battery electrode layer, and a separator layer, and satisfies all of the following (1) to (4): (1) the secondary battery electrode layer contains an active material, an electrolyte solution, and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

[0098] The present disclosure (12) is a secondary battery including a current collector layer, a secondary battery electrode layer, and a separator layer, and the secondary battery satisfies all of the following (1) to (3): (1) the secondary battery electrode layer contains an active material, an electrolyte, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

[0099] The present disclosure (13) is a method for permeating an electrode composition with an electrolyte solution, which satisfies all of the following (1) to (4): (1) the electrode composition contains an active material and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa; ０．５(3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

[0100] The present disclosure (14) is a method for permeating an electrode composition with an electrolyte solution, which satisfies all of the following (1) to (3): (1) the electrode composition contains an active material, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa or less; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

[0101] The present disclosure (15) is a method for manufacturing a secondary battery, which includes a step of permeating an electrolytic solution into a battery unit including a current collector layer, an electrode composition layer, and a separator layer to obtain a secondary battery electrode layer in which the electrolytic solution is contained in the electrode composition layer, and which satisfies all of the following (1) to (4): (1) the electrode composition layer contains an active material and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

[0102] The present disclosure (16) is a method for manufacturing a secondary battery, which includes a step of permeating an electrolytic solution into a battery unit including a current collector layer, an electrode composition layer, and a separator layer to obtain a secondary battery electrode layer in which the electrolytic solution is contained in the electrode composition layer, and which satisfies all of the following (1) to (3): (1) the electrode composition layer contains an active material, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

[0103] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples unless it deviates from the gist of the present invention. Unless otherwise specified, parts mean parts by weight and % means % by weight.

[0104] (Preparation of Additives 1 to 21) The following Additives 1 to 21 were prepared. (Additive 1) Methyl n-octanoate (reagent: manufactured by Tokyo Chemical Industry Co., Ltd.) was used as Additive 1. (Additive 2) Methyl tetradecanoate (reagent: manufactured by Tokyo Chemical Industry Co., Ltd.) was used as Additive 2. (Additive 3) Glycerin and stearic acid (molar ratio: 1 / 1) were added to xylene to initiate the esterification reaction (xylene content: 50 wt% of the total). Polymerization was carried out under reflux, and water produced in the esterification reaction was removed together with xylene. The amount of xylene removed was added, and the polymerization was continued until no more water was produced. After the reaction, the xylene was removed using a vacuum dryer to obtain a solid glycerin stearate, which was used as Additive 3.

[0105] (Additive 4) An alkylene oxide adduct of alkyl alcohol produced by adding ethylene oxide (EO) to isodecanol was obtained as Additive 4. The average number of moles of EO added was 7.0, and the compound was named heptaethylene glycol monoisodecyl ether. (Additive 5) An alkylene oxide adduct of alkyl alcohol produced by adding ethylene oxide (EO) to pentadecyl alcohol was obtained as Additive 5. The average number of moles of EO added was 4.0, and the compound was named tetraethylene glycol monopentadecyl ether. (Additive 6) An alkylene oxide adduct of alkyl alcohol produced by adding ethylene oxide (EO) to dodecanol was obtained as Additive 6. The average number of moles of EO added was 9.0, and the compound was named nonaethylene glycol monododecyl ether.

[0106] (Additive 7) Tetraethylene glycol (reagent: manufactured by Tokyo Chemical Industry Co., Ltd.) was used as Additive 7. (Additive 8) Octaethylene glycol (reagent: manufactured by Tokyo Chemical Industry Co., Ltd.) was used as Additive 8. (Additive 9) An alkylene oxide adduct of alkyl alcohol produced by adding ethylene oxide (EO) to methanol was obtained as Additive 9. The average number of moles of EO added was 9.0, and the compound name was nonaethylene glycol monomethyl ether.

[0107] (Additive 10) Triethylene glycol dimethyl ether (reagent: manufactured by Tokyo Chemical Industry Co., Ltd.) was used as Additive 10. (Additive 11) An alkylene oxide adduct of alkyl alcohol produced by adding ethylene oxide (EO) to tribenzylphenol was obtained as Additive 11. The average number of moles of EO added was 6.0, and the compound was named hexaethylene glycol tribenzyl phenyl ether. (Additive 12) An alkylene oxide adduct of alkyl alcohol produced by adding ethylene oxide (EO) to tribenzylphenol was obtained as Additive 12. The average number of moles of EO added was 14.0, and the compound was named tetradecaethylene glycol tribenzyl phenyl ether.

[0108] (Additive 13) Cyclohexylamine (reagent: manufactured by Tokyo Chemical Industry Co., Ltd.) was used as additive 13. (Additive 14) An alkylene oxide adduct of alkyl alcohol produced by adding ethylene oxide (EO) to bisphenol A was obtained as additive 14. The average number of moles of EO added was 2.0, and the compound was called an EO 2 mole adduct of bisphenol A. (Additive 15) Tris(2-chloro-1-methylethyl) phosphate (reagent: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as additive 15.

[0109] (Additive 16) An alkylene oxide adduct of alkyl alcohol produced by adding propylene oxide (PO) to propylene glycol was obtained as Additive 16. The average number of moles of PO added was 6.0, and the compound name was heptapropylene glycol. (Additive 17) Hexadecanol (reagent: manufactured by Tokyo Chemical Industry Co., Ltd.) was used as Additive 17. (Additive 18) Triethylene glycol (reagent: manufactured by Tokyo Chemical Industry Co., Ltd.) was used as Additive 18.

[0110] (Additive 19) Ethylene glycol monomethyl ether (reagent: manufactured by Tokyo Chemical Industry Co., Ltd.) was used as additive 19. (Additive 20) Trimethylolpropane (reagent: manufactured by Tokyo Chemical Industry Co., Ltd.) was used as additive 20. (Additive 21) N-(hydroxymethyl)methacrylamide (reagent: manufactured by Tokyo Chemical Industry Co., Ltd.) was used as additive 21.

[0111] (Preparation of Electrolytes 1 to 4) The following substances were all prepared as reagents (manufactured by Tokyo Chemical Industry Co., Ltd.). (Electrolyte 1) Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of EC:DEC = 1:1, and lithium hexafluorophosphate (LIPF) was added. ６ ) was dissolved to a concentration of 1 M to prepare electrolyte solution 1. (Electrolyte solution 2) Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of EC:EMC:DEC = 2:4:4, and lithium hexafluorophosphate (LIPF ６ ) was dissolved to a concentration of 1 M to prepare electrolyte solution 2. (Electrolyte solution 3) Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of EC:EMC:DEC = 3:5:2, and lithium hexafluorophosphate (LIPF ６ ) was dissolved to a concentration of 1 M to prepare electrolyte solution 3. (Electrolyte solution 4) Ethylene carbonate (EC) and propylene carbonate (PC) were mixed in a volume ratio of EC:PC = 1:1, and lithium hexafluorophosphate (LIPF ６ ) was dissolved to a concentration of 1M to prepare electrolyte solution 4.

[0112] (Preparation of negative electrode active materials) The following negative electrode active materials were prepared. Graphite 1: artificial graphite (FSN-1, manufactured by Shanshan China Co., Ltd., volume average particle diameter (D50): 15.3 μm) Graphite 2: spherical graphite (CGR 12R, manufactured by Nippon Graphite Industries Co., Ltd., volume average particle diameter: 10.6 μm)

[0113] (Calculation of HSP Value of Negative Electrode Active Material: Graphite 1) The dispersibility of graphite 1 in various solvents was evaluated by the following method. 20 mL of a solvent with a known solubility parameter and 0.04 g of graphite 1 were placed in a Maruemu Co., Ltd. No. 7 screw tube, and a stirrer was added. The mixture was stirred at 400 rpm for 30 minutes to prepare a suspension. The suspension was then left to stand in a constant temperature bath at 25°C for 12 hours to prepare a dispersion for measurement. The solvents with known solubility parameters were toluene, N-methylpyrrolidone (NMP), diethyl carbonate, dimethylformamide, 1,4-dioxane, hexane, cyclohexane, methanol, ethanol, acetone, acetonitrile, and methyl ethyl ketone (MEK). The solubility parameters of these solvents were determined by reference to the HSPiP database. Also, 20 mL of each solvent was placed in a Maruemu Co., Ltd. No. 7 screw tube, and similarly left to stand in a constant temperature bath at 25°C for 12 hours to prepare a reference solvent.

[0114] Baseline measurements were performed using an ultraviolet-visible-near-infrared spectrophotometer (UV-3600i Plus, Shimadzu Corporation) in a reference solvent. The measurement dispersion corresponding to the reference solvent was then stirred in a screw tube for more than 1 minute, and while stirring in a fully dispersed state, 1000 μL each was transferred to a quartz cell containing a stir bar four times with a micropipette, and used as a measurement cell. The measurement cell was set in a holder with a stirrer, stirred for 30 seconds, and the measurement of the absorption spectrum was started at the same time as stopping the stirring, and the absorbance value was recorded at 10-second intervals for 20 minutes (measurement wavelength: 632 nm). The dispersion index (DISP) was calculated as "absorbance after 20 minutes (A20) / absorbance at the start of measurement (A0)". The obtained dispersion index was used to evaluate the dispersibility in each solvent based on the following evaluation criteria.

[0115] (Evaluation criteria) 1: DISP = 0.30 or more 2: DISP = 0.20 or more and less than 0.30 3: DISP = 0.15 or more and less than 0.20 4: DISP = 0.10 or more and less than 0.15 5: DISP = less than 0.10 The HSP value of graphite 1 was calculated from the evaluation results of the dispersibility of graphite 1 in a solvent by inputting the results into HSPiP. The evaluation results of dispersibility used to calculate the HSP value of graphite 1 are shown in Table 1.

[0116]

[0117] (Calculation of HSP value of negative electrode active material: graphite 2) The HSP value of graphite 2 was also calculated in the same manner as for graphite 1. Of the solvents with known solubility parameters used to calculate the HSP value of graphite 1, hexane was not used, and other solvents were used instead. The other procedures were the same as for graphite 1. The evaluation results of dispersibility used to calculate the HSP value of graphite 2 are shown in Table 2.

[0118]

[0119] (Preparation of Positive Electrode Active Material) The following positive electrode active material was prepared. NCM: NCM811 RL-08-D3 (manufactured by Umicore) with a LiNi composition ０．８ Co ０．１ Mn ０．１ O ２

[0120] (Calculation of HSP Value of Positive Electrode Active Material: NCM) The HSP value of NCM, which is a positive electrode active material, was calculated in the same manner as for graphite 1. Table 3 shows the evaluation results of dispersibility used to calculate the HSP value of NCM.

[0121]

[0122] The solubility parameters of graphite 1, graphite 2, and NCM calculated based on the results shown in Tables 1, 2, and 3 above are shown in Table 4.

[0123]

[0124] (Examples 1 to 55, Comparative Examples 1 to 39, Graphite 1 was used) (Preparation of Negative Electrode with Additive) 2.0 parts by weight of AB (acetylene black: “Denka Black Li100”, manufactured by Denka Co., Ltd., average particle size of primary particles: 35 nm) as a conductive additive, 3.0 parts by weight of CMC (carboxymethyl cellulose) as a binder resin, and 40.0 parts by weight of ion-exchanged water were stirred at 2000 rpm for 5 minutes using a planetary stirring type mixing kneader {Awatori Rentaro [manufactured by Thinky Corporation]}.

[0125] Next, 3.0 parts by weight of SBR (styrene butadiene rubber) as a binder resin was added, and the mixture was stirred for 5 minutes at 2000 rpm using a mixer. To the resulting dispersion, 91.0 parts by weight of graphite 1 as a negative electrode active material, 1.0 part by weight of additive, and 60.0 parts by weight of ion-exchanged water were added, and the mixture was stirred for 5 minutes at 2000 rpm using a mixer to prepare a slurry for a negative electrode active material layer.

[0126] The resulting negative electrode active material layer slurry was applied to one side of a current collector (copper foil) using an applicator with a clearance set to 150 μm in the atmosphere, pre-dried overnight in a draft, and then further dried under reduced pressure (1.3 kPa) at 100 °C for 2 hours to obtain an electrode sheet. Sixteen 16 mm diameter electrodes were punched out near the center of the electrode sheet. This operation was repeated multiple times, and three of the resulting electrodes were used as electrodes (negative electrodes) for simple electrode brittleness testing. The remaining electrodes were pressed twice in a press at 1.5 MPa for 3 seconds to prepare evaluation electrodes (negative electrodes). Each negative electrode was prepared for Additives 1 to 21.

[0127] (Preparation of Negative Electrode without Additive) An electrode (negative electrode) for simple electrode brittleness testing and an electrode (negative electrode) for evaluation were prepared in the same manner as the negative electrode with additive, except that 92.0 parts by weight of graphite 1 was used and no additive was added.

[0128] <Calculation of electrode density> The weight and thickness of the current collector and the evaluation electrode were measured after pressing twice at 1.5 MPa for 3 seconds using a press machine, and the electrode density (g / cm) was calculated using the following formula. ３ ) = (evaluation electrode weight (g) - current collector weight (μg) × 10 －３ ) / (0.8 ２ × 3.14 × ((evaluation electrode thickness (μm) − current collector thickness (μm)) × 10－４ ))

[0129] <Simple electrode brittleness test> An electrode for the simple electrode brittleness test was dropped freely onto a piece of white paper from a height of 30 cm. This was performed on three electrodes for the simple electrode brittleness test, and the electrodes were evaluated according to the following criteria: ◯: 0 pieces of electrode stuck to the white paper ×: 1 or more pieces of electrode stuck to the white paper

[0130] <Electrolyte penetration test> The electrode density (g / cm ３ ) maximum and minimum difference is 0.03 (g / cm ３ Three electrodes were selected so that the electrode density (g / cm) of the evaluation electrode was within the range of 0.01 to 0.01. ３ ) was recorded. A stainless steel M3 flat washer (manufactured by ESCO) was placed at the center of each electrode, and 20 μL of electrolyte was dropped into the hole in the washer. The time until the droplet in the washer completely disappeared from the electrode surface was recorded in units of 1 second, and the arithmetic mean value was taken as the electrolyte penetration time (penetration rate: min). An electrolyte penetration test was conducted for each of electrolytes 1 to 4.

[0131] <Capacity retention rate after severe test> Preparation of negative electrode half-cell for capacity retention rate severe test ３ ) maximum and minimum difference is 0.03 (g / cm ３ Three electrodes were selected so that the electrode density (g / cm) of the evaluation electrode was within the range of 0.01 to 0.01. ３ The negative electrode, a separator [product name "#3501" manufactured by Celgard Inc.], and a lithium foil were stacked in this order from the negative electrode side, an electrolyte solution was injected, and then the resultant was vacuum laminated to prevent oxygen from entering, thereby preparing a negative electrode half cell for a severe capacity retention test.

[0132] Negative Electrode Half-Cell Charge / Discharge Test At 25°C, a charge / discharge measuring device "HJ-SD8" [manufactured by Hokuto Denko Corporation] was used to evaluate the capacity retention rate of the negative electrode half-cell for the severe test by the following method. The cell was charged to 0 V at a current of 0.05 C using a constant current charging method (also referred to as CC mode), and after a 10-minute pause, it was discharged to 1.5 V at a current of 0.05 C. The discharged capacity at this time was defined as [1-cycle discharge capacity (mAh)]. Charge / discharge was performed again under the same conditions, and the discharged capacity at this time was defined as [2-cycle discharge capacity (mAh)]. Next, the cell was charged to 0 V at a current of 0.1 C, and after a 10-minute pause, it was discharged to 1.5 V at a current of 0.1 C. The discharged capacity at this time was defined as [3-cycle discharge capacity (mAh)]. Further, the electrodes were charged to 0 V at a current of 0.5 C, and after a 10-minute pause, discharged to 1.5 V at a current of 0.1 C. The discharged capacity at this time was designated as the [4-cycle discharge capacity (mAh)]. Finally, the electrodes were charged to 0 V at a current of 1.0 C, and after a 10-minute pause, discharged to 1.5 V at a current of 0.1 C. The discharged capacity at this time was designated as the [5-cycle discharge capacity (mAh)]. The post-stress test capacity retention rate for each of the three electrodes was calculated using the following formula, and the arithmetic mean was designated as the post-stress test capacity retention rate (%) of the evaluation electrode. Post-stress test capacity retention rate (%) = [5-cycle discharge capacity (mAh)] / [2-cycle discharge capacity (mAh)] An electrolyte penetration test was conducted for each of Examples 1 to 17, which used Additives 1 to 17, Comparative Examples 1 to 4, which did not use any additives, and Comparative Examples 5 to 8, which used Additives 18 to 21.

[0133] The evaluation results using graphite 1 are summarized in Tables 5 to 12. Tables 5 and 6 show examples and comparative examples using electrolyte solution 1, Tables 7 and 8 show examples and comparative examples using electrolyte solution 2, Tables 9 and 10 show examples and comparative examples using electrolyte solution 3, and Tables 11 and 12 show examples and comparative examples using electrolyte solution 4. The unit of HSP distance in each table shown below is [MPa ０．５ ].

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[0138]

[0139]

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[0141]

[0142] (Examples 56 to 106, Comparative Examples 40 to 82, Graphite 2 Used) Negative electrodes with and without additives were prepared using graphite 2 instead of graphite 1, and the electrode density was calculated, and a simple electrode brittleness test and electrolyte penetration test were performed. A test for capacity retention rate after a severe test was not performed.

[0143] The evaluation results using graphite 2 are summarized in Tables 13 to 20. Tables 13 and 14 show examples and comparative examples using electrolytic solution 1, Tables 15 and 16 show examples and comparative examples using electrolytic solution 2, Tables 17 and 18 show examples and comparative examples using electrolytic solution 3, and Tables 19 and 20 show examples and comparative examples using electrolytic solution 4.

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[0149]

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[0151]

[0152] (Examples 107 to 149, Comparative Examples 83 to 133, NCM used) (Preparation of Positive Electrode with Additive) 1.0 part by weight of additive and 100.0 parts by weight of N-methyl-2-pyrrolidone (NMP) were stirred for 5 minutes at 2000 rpm using a planetary stirring mixer (Awatori Mixer [manufactured by Thinky Corporation]). Next, 3.0 parts by weight of polyvinylidene fluoride (manufactured by Kishida Chemical) as a binder resin was added, and stirring was carried out for 5 minutes at 2000 rpm using the Awatori Mixer.

[0153] Further, 89.0 parts by weight of NCM as a positive electrode active material and 7.0 parts by weight of AB {acetylene black: "Denka Black Li100", manufactured by Denka Co., Ltd.} as a conductive additive were added, and the mixture was stirred at 2000 rpm for 4 minutes using a mixer to prepare a slurry for a positive electrode active material layer.

[0154] The resulting positive electrode active material layer slurry was applied to one side of a current collector (aluminum foil, manufactured by Hosen Co., Ltd.) using an applicator with a clearance set to 150 μm in the atmosphere. The resulting slurry was then pre-dried overnight in a draft chamber, and further dried at 100°C under reduced pressure (1.3 kPa) for 2 hours to obtain an electrode sheet. Sixteen 15 mm diameter electrodes were punched out near the center of the electrode sheet. This operation was repeated multiple times, and three of the resulting electrodes were used as electrodes (positive electrodes) for simple electrode brittleness testing. The remaining electrodes were pressed twice in a press at 4.0 MPa for 3 seconds to prepare evaluation electrodes (positive electrodes). Each positive electrode was prepared for Additives 1 to 21.

[0155] (Preparation of Positive Electrode without Additive) An electrode (positive electrode) for simple electrode brittleness testing and an electrode (positive electrode) for evaluation were prepared in the same manner as in the positive electrode with additive, except that 90.0 parts by weight of NCM was used and no additive was added.

[0156] The electrode (positive electrode) for the simple electrode embrittlement test and the evaluation electrode (positive electrode) were subjected to the same procedures as for the negative electrode, including calculation of electrode density, simple electrode embrittlement testing, and electrolyte penetration testing. Tests for capacity retention after severe testing were not conducted. When calculating electrode density, the formula was adjusted to reflect the difference in the diameter of the punched electrode sheet.

[0157] The evaluation results using NCM are summarized in Tables 21 to 28. Tables 21 and 22 show examples and comparative examples using electrolyte solution 1, Tables 23 and 24 show examples and comparative examples using electrolyte solution 2, Tables 25 and 26 show examples and comparative examples using electrolyte solution 3, and Tables 27 and 28 show examples and comparative examples using electrolyte solution 4.

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[0165]

[0166] From these results, for electrodes using the same active material and electrolyte, the permeation rate in each example where the HSP distance between the active material and the additive and the HSP distance between the electrolyte and the additive were within a predetermined range was faster (shorter permeation time) than in the comparative examples. Regarding electrode density, the electrode density was varied over a relatively wide range in the comparative examples (for example, in comparative examples 1 to 4, the electrode density was varied over a range of 1.53 to 1.64). However, the permeation rate in each example was faster than in any of the comparative examples. Therefore, regardless of electrode density, satisfying the requirements of the present invention demonstrates excellent permeability of the electrolyte. Furthermore, in examples 1 to 17, the battery performance was confirmed (severe testing) for additives 1 to 17, which were effective in permeability, and none of them had a negative effect on battery performance.

[0167] In addition, the HSP distance between the active material and the additive is 4.0 MPa. ０．５ In Examples where the average electrode embrittlement ratio was less than 1.0 (Examples 11, 12, etc.), the compatibility between the additive and the active material was high, so the surface of the active material was corroded by the additive, and the electrode embrittlement was evaluated as x.

Claims

1. An electrode composition for a secondary battery electrode layer containing an electrolytic solution, which satisfies all of the following (1) to (4): (1) contains an active material and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa. ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

2. An electrode composition for a secondary battery electrode layer containing an electrolytic solution, the electrode composition satisfying all of the following (1) to (3): (1) containing an active material, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa. ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

3. The HSP distance (Ra_Act) between the additive and the active material is 4.0 MPa. ０．５ 3. The electrode composition according to claim 1 or 2, wherein the above-mentioned 4. The HSP distance (Ra_Elec) between the additive and the electrolyte is 12.0 MPa. ０．５ 3. The electrode composition according to claim 1, wherein:

5. The electrode composition according to claim 1 or 2, wherein the additive is an alkylene oxide adduct of an alkyl alcohol or an alkylene oxide adduct of an alkylene glycol.

6. The electrode composition of claim 5, wherein said alkyl alcohol is a saturated alkyl alcohol.

7. The electrode composition according to claim 1 or 2, wherein the active material is at least one selected from the group consisting of a composite oxide containing at least one transition metal element, artificial graphite, and natural graphite.

8. The electrode composition according to claim 1 or 2, wherein the solvent of the electrolyte is a mixed solvent of ethylene carbonate and diethyl carbonate, a mixed solvent of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate, or a mixed solvent of ethylene carbonate and propylene carbonate.

9. An electrode for a secondary battery obtained by compression molding the electrode composition according to claim 1 or 2.

10. A secondary battery comprising the electrode for a secondary battery according to claim 9.

11. A secondary battery including a current collector layer, a secondary battery electrode layer, and a separator layer, which satisfies all of the following (1) to (4): (1) the secondary battery electrode layer contains an active material, an electrolyte, and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa. ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

12. A secondary battery including a current collector layer, a secondary battery electrode layer, and a separator layer, which satisfies all of the following (1) to (3): (1) the secondary battery electrode layer contains an active material, an electrolyte, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa. ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

13. A method for impregnating an electrode composition with an electrolyte, the method satisfying all of the following (1) to (4): (1) the electrode composition contains an active material and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa or less; ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

14. A method for permeating an electrode composition with an electrolyte, the method satisfying all of the following (1) to (3): (1) the electrode composition contains an active material, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa. ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

15. A method for manufacturing a secondary battery, comprising a step of permeating an electrolyte solution into a battery unit including a current collector layer, an electrode composition layer, and a separator layer to obtain a secondary battery electrode layer in which the electrolyte solution is contained in the electrode composition layer, wherein the method satisfies all of the following (1) to (4): (1) the electrode composition layer contains an active material and an additive, but does not contain a binder resin; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ (4) The weight average molecular weight (Mw) of the additive is 50,000 or less.

16. A method for manufacturing a secondary battery, comprising a step of permeating an electrolyte solution into a battery unit including a current collector layer, an electrode composition layer, and a separator layer to obtain a secondary battery electrode layer in which the electrolyte solution is contained in the electrode composition layer, wherein the method satisfies all of the following (1) to (3): (1) the electrode composition layer contains an active material, a binder resin, and an additive; (2) the HSP distance (Ra_Act) between the additive and the active material is 12.0 MPa. ０．５ (3) The HSP distance (Ra_Elec) between the additive and the electrolyte is 14.0 MPa or less; ０．５ The following is the result.

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