WO2006025601A1

WO2006025601A1 - Positive electrode material composition for lithium secondary battery

Info

Publication number: WO2006025601A1
Application number: PCT/JP2005/016467
Authority: WO
Inventors: Alan Vallee; Paul-Andre Lavoie; Kazuhiko Murata; Teruki Matsushita; Keiichiro Mizuta; Kazuo Takei; Hironobu Hashimoto
Original assignee: Nippon Shokubai Co., Ltd.
Priority date: 2004-09-03
Filing date: 2005-09-01
Publication date: 2006-03-09
Also published as: JPWO2006025601A1

Abstract

Disclosed is a positive electrode material composition for lithium secondary batteries which does not cause deterioration in the battery performance of a lithium secondary battery using a positive electrode which is produced from the positive electrode material composition even though the composition contains a polymer, an electrode active material and a conductive assistant beforehand. Specifically disclosed is a positive electrode material composition for lithium secondary batteries essentially containing a polymer, an electrode active material and a conductive assistant which is characterized by further containing one or more antioxidantsselected from the group consisting of amine antioxidants, phosphorus antioxidants and phenothiazine antioxidants.

Description

Description Positive electrode material composition for lithium secondary battery

The present invention relates to a positive electrode material composition used for producing a lithium secondary battery. Background art

The positive electrode used in the lithium secondary battery includes a polymer that constitutes the matrix, an electrolyte salt (lithium salt) that helps transfer lithium ions, an electrode active material for storing lithium ions, and electron transfer. In general, a composition obtained by mixing (mixing) a conductive auxiliary agent of the present invention and, if necessary, a solvent is generally used as a material, and in the past, such a composition has been formed as a material. Various batteries using the positive electrode have been proposed (see, for example, Patent Documents 1 to 4). Specifically, the positive electrode is manufactured by a method of extruding the composition as described above or a method of solution casting and devolatizing a solvent. In the production of S, it was usual to carry out the steps of mixing a polymer, an electrolyte salt, an electrode active material, a conductive auxiliary agent and the like, and a step of forming the obtained mixture. That is, the polymer serving as the raw material of the positive electrode, the electrolyte salt, the electrode active material, and the conductive auxiliary agent are mixed immediately before the formation of the positive electrode, and each raw material used in producing the positive electrode is usually individual Were procured.

[Patent Document 1] Special Table 2 0 0 2-5 3 5 2 3 5

[Patent Document 2] US Patent No. 5 7 5 5 9 8 5

[Patent Document 3] International Publication No. 0 3 Z 7 5 3 7 5 Breadlet

[Patent Document 4] International Publication No. 0 3 0 9 2 0 1 7 Breadlet Disclosure of the Invention Problems to be Solved by the Invention

However, in consideration of the simplification of the process at the time of positive electrode production, etc., among the above-mentioned raw materials of positive electrode, the one prepared by mixing (kneading) the electrode active material and the conductive auxiliary agent in advance into the matrix is procured. There is something to be done. However, when such a procurement form is adopted, there is a problem that the battery performance is significantly inferior to the case where a battery is manufactured using a positive electrode obtained by individually procuring each raw material and mixing (kneading) immediately before molding. Happened. Therefore, the problem to be solved by the present invention is that although the polymer, the electrode active material and the conductive auxiliary agent are contained in advance, the battery performance of the lithium secondary battery using the produced positive electrode is An object of the present invention is to provide a positive electrode material composition for a lithium secondary battery which does not decrease. Means to solve the problem

The present inventors diligently studied to solve the above-mentioned problems. As a result, polymer, electrode While mixing (kneading) the active material and the conductive aid (especially when melt kneading under high temperature), or while being mixed (kneaded) before being used for molding, while being stored for a fixed period for transportation or storage Although the molecular weight of the matrix polymer is slightly decreased, and the decrease in molecular weight of this polymer is not a problem in other applications other than the cathode material application, but the lithium secondary battery In the positive electrode materials used for this purpose, we have found that it is a factor that adversely affects battery performance. Then, based on this finding, during mixing (kneading) of the polymer, the electrode active material, and the conductive auxiliary, or while being stored for a certain period for transportation, storage, etc. before mixing (kneading) and before being used for molding. As a result of various investigations on means for suppressing the molecular weight reduction of the resulting polymer to an extent not affecting the battery performance, a specific antioxidant is contained in the positive electrode material composition containing the polymer, the electrode active material and the conductive aid. In the case of a lithium secondary battery using a positive electrode made of a positive electrode material composition containing such a specific antioxidant, the battery performance is not deteriorated. After confirming, the present invention was completed.

That is, the positive electrode material composition for a lithium secondary battery according to the present invention is a composition for a positive electrode material that essentially comprises a polymer, an electrode active material and a conductive auxiliary, and is an amine antioxidant, a phosphorus antioxidant And at least one antioxidant selected from the group consisting of phenothiazine-based antioxidants. Effect of the invention

The positive electrode material composition for a lithium secondary battery of the present invention contains in advance a polymer, an electrode active material and a conductive support agent, so that the process at the time of manufacturing the positive electrode can be simplified. It is possible to prevent the battery performance of the lithium secondary battery using the positive electrode from being degraded. BEST MODE FOR CARRYING OUT THE INVENTION

The positive electrode material composition for a lithium secondary battery according to the present invention (hereinafter sometimes referred to simply as “positive electrode material composition”) will be described in detail below, but the scope of the present invention is bound by these descriptions. However, other than the following examples, modifications can be made as appropriate without departing from the spirit of the present invention.

The positive electrode material composition for a lithium secondary battery of the present invention is a composition that essentially includes a polymer, an electrode active material, and a conductive additive. As described above, since the composition of the present invention contains a polymer necessary as a positive electrode material, an electrode active material and a conductive auxiliary agent, there is an advantage that the process in manufacturing the positive electrode can be simplified.

The polymer which is an essential component of the positive electrode material composition is not particularly limited as long as it is usually used as a matrix of a positive electrode material for a lithium secondary battery, and is an ion conductive polyether polymer. Is preferred. In particular, it is preferable that the polymer is an ethylene oxide-based polymer in that the battery performance as a positive electrode material can be further improved. The ethylene oxide-based polymer suitable as the polymer is, for example, ethylene oxide. The following general formula (1):

(In the formula (1), R i and R a (where R a is a C1-C16 alkyl group, a cycloalkyl group, a aryl group, an aryl group, a (meth) acryloyl group and an alkenyl group Or a single CH ₂ —O—R e — R a group (R e has one (CH ₂ —CH ₂ —O) p — structure (P is 0 to 10). integer)))

It can obtain by polymerizing the monomer mixture which makes essential a substituted oxylan compound shown by these. The monomer mixture may contain other monomers in addition to ethylene oxide and the substituted alkoxy compound. The proportion of each monomer in the monomer mixture is not particularly limited and may be appropriately set.

Examples of substituted oxisilane compounds represented by the above structural formula (1) include propylene oxide, butylene oxide, 1,2 _ epoxypentane, 1,2 _ epoxyhexane, 1,2 epoxy octane, cyclohexenoxide and styrene oxide. Or methyl glycidyl ether, cetyl dalysidyl ether, ethylene glycol methyl dalysyl ether, and the like. Also, assuming that the substituent is a crosslinkable substituent, it is possible to use, for example, epoxy butene, 3,4-epoxy 1 1 1 penten, 1, 2-epoxy 1 5, 9-cyclododecadiene, 3, 4- Epoxy-1-vinylcyclohexene, 1,2-epoxy-5-cyclooctene, glycidyl acrylate, glycidyl methacrylate, glycidyl sorbate and glycidyl 1-4-hexanoate, or, vinyl glycidyl ether, aryl glycidyl Ether, 4-Buulchix hexyl glycidyl ether, a- Tenorepini nole glycidno leece one-nore, Cyclohexene / Remethinole glycidino reate / Re, 4-Vinyl benzyl glycidyl ether, 4-Aryl benzyl Glycidyl ether, aryl glycidyl ether, ethylene glycol paryl glycidyl Ether, ethylene glycol vinyl glycidyl ether, diethylene glycol paryl glycidyl ether, diethylene glycol vinyl glycidyl ether, triethylene glycol palyl glycidyl ether, triethylene glycol vinyl dalysyl ether, oligo ethylene glycol gallyl glycidyl ether and oligo ethylene Examples include dalicol vinyl dalysidyl ether. The number of substituted oxylan compounds may be one or two or more.

In order to obtain the ethylene oxide-based polymer, the monomer mixture may be polymerized while being stirred in a solvent. The method for such polymerization is not particularly limited, but preferred examples include a solution polymerization method and a precipitation polymerization method. Among them, the solution polymerization method is more preferable because it has excellent productivity. A solution polymerization method in which polymerization is performed while supplying each monomer as a raw material to a previously charged solvent is particularly preferable because of safety such as easy removal of heat of reaction. In the above polymerization, a commonly used polymerization initiator, An agent or the like may be added and used.

Examples of the solvent include aromatic hydrocarbon solvents such as benzene, toluene, xylene, and ethylbenzene; and aliphatic hydrocarbons such as heptane, octane, n-hexane, n-pentane, and 2, 2, 4-trimethylpentane. Aliphatic hydrocarbon solvents such as cyclohexane and methyl cyclohexane; ether solvents such as jetyl ether, dibutyl ether and methyl butyl ether; solvents of ethylene diallyl dialkyl ethers such as dimethoxetane; THF Organic solvents which do not contain active hydrogen such as hydroxyl groups such as cyclic ether solvents such as (tetrahydrofuran) and dioxan; etc. are preferable, and toluene and xylene are more preferable. Furthermore, that the solvent is an organic solvent that does not contain water at all avoids the problem that hydroxide and the like generated by the reaction of water and metal ions become an insulating layer and the cycle characteristics of the battery are degraded. It is preferable to do it.

The weight average molecular weight (Mw) of the polymer is not particularly limited, but is preferably 2 0 0 0 5-0 0 0 0 0 0, more preferably 3 0 0 0 0 0 3 0 0 , 0 0 0, and more preferably 4.0, 0 0 0 to 2 0 0, 0 0 0. If the weight average molecular weight is less than 20, 00, there is a risk that tack will occur when forming into a positive electrode, while if it exceeds 500, the forming itself becomes difficult, Processability and handling may be reduced.

The molecular weight distribution (MwZMn) of the polymer is not particularly limited, but is preferably 3 or less, more preferably 2 or less. When the molecular weight distribution exceeds 3, there is a risk that tackiness may occur when the molded product is made into a positive electrode, or the handling property may be deteriorated.

The electrode active material, which is an essential component of a positive electrode material composition, enables charge and discharge by reversibly inserting and desorbing lithium ions, and is usually used to form a positive electrode. No particular limitation is imposed on the material, and examples thereof include lithium vanadium complex oxide, lithium cobalt complex oxide, lithium manganese complex oxide, lithium nickel complex oxide and the like, among which L ix V y O z (however, x, y and z are independent of each other, and 0 <x≤2, y = (mx + 2 z) / n, and z = (mx + ny) / 2 , M is a valence number of Li, n is a real number satisfying valence number of V of 4 or more.) Lithium which has excellent performance of high capacity and high voltage. Particularly preferred is that a positive electrode capable of producing a secondary battery can be obtained. Yes. The electrode active material may be only one type, or two or more types.

The proportion of the electrode active material in the positive electrode material composition is not particularly limited, but is preferably, for example, 0.1 to 50 times by weight the polymer, and more preferably 0.3 to 2 times. It is preferable to be 0 times, more preferably 0.5 to 10 times. If the amount of the electrode active material is too small, the function as the positive electrode may not be sufficiently exhibited. On the other hand, if the amount of the electrode active material is too large, molding may be difficult.

The conductive auxiliary agent, which is an essential component of the positive electrode material composition, is not particularly limited as long as it is generally used to form a positive electrode, and examples thereof include acetylene black, ketjen black, Graphite, etc. Can be mentioned. The conductivity assistant may be only one kind or two or more kinds.

The proportion of the conductive auxiliary agent in the positive electrode material composition is not particularly limited. The amount is preferably 0.1 to 20 parts by weight, more preferably 1 to 15 parts by weight with respect to 100 parts by weight of the extremely active material. If the amount of the conductive additive is too small, the conductivity of the positive electrode may be insufficient. On the other hand, if the amount of the conductive additive is too large, molding may be difficult.

The positive electrode material composition of the present invention contains one or more antioxidants selected from the group consisting of amine antioxidants, phosphorus antioxidants and phosphine oxides antioxidants. Thereby, it is possible to suppress the decrease in molecular weight of the polymer to a range not affecting the battery performance, and to prevent the battery performance of the lithium secondary battery using the manufactured positive electrode from being degraded. In the present invention, in particular, it is preferable that the above-mentioned antioxidant is an amine-based antioxidant and a phosphorus-based antioxidant from the viewpoint that molecular weight reduction can be effectively suppressed with a small amount.

Examples of the amine-based antioxidants include bis (4_t-butylphenyl) phamine, poly (2,2 and 4 trimethyl 1, 2 2 dihydroquinoline), 6-ethoxy and 1,2 2 -dich 2 , 2,4 _ trimethylquinoline, reaction product of diphenylamine and acetone, 1-(N-phenylamino) mononaphthalene, diphenylamine derivative, dialkyl diphenyl lamines, N, N, mono diphenyl mono p-pheni radiamine, mixed gyalyl _ p-phenylenediamine, N-phenyl-one N, monoisopropyl-one-p-phenylediamine, N, N'-di- 2-naphthyl-one-p-phenylediamine, etc. —T_butylphenyl) amine is preferred. The amine antioxidant may be one type alone, or two or more types.

Examples of the above-mentioned phosphorus-based antioxidants include trififnyl phosphate, diphenyl isodecyl phosphate, phenyl diisodecyl phosphate, and 4,4′-butylidene bis.

(3-Methyl _ 6-t-butylphenylditridecyl) phosphate,

Cyclic neopentane tetrayl bis (octadecyl phosphate), tris (nonphenyl phenyl phosphate), tris (mono (or di) noyl phenyl) phosphate, diisodecyl pentaerythritol diphosphate, 9, 10-Dihydro 1 9-Oxa 1 1 0-Phosphaphenanthrene 1 1 0-Oxide, 1 0-(3, 5-Di-t-butyl-1- 4-hydroxybenzyl) 1 9, 1 0- Dihydro 1 9 1 Oxa 1 1 0 _ Phosphaphenanthrene _ 1 0 0-Oxide, 1 0-Decipheral 9, 1 0-Dihydro _ 9-Oxa 1 1 0-Phosphaphenanthrene 1 0 0-Oxide , Tris (2, 4-di-t-butylphenyl) phosphite, cyclic neopentanetetrayl bis (2, 4-di-t-butylphenyl) phosphate, cyclic Cu neopentane tetrayl bis (2,6-di-tert-butyl-4-methylphenyl) phosphate, 2,2-methylenebis (4,6-di-tert-butylphenyl) octyl phosphite etc. are mentioned, among these In particular, cyclic neopentanetetraylbis (2,6-di-tert-butyl-4-methylphenyl) phosphite is preferred. The phosphorus-based antioxidant may be only one type, or two or more types.

Examples of the phenothiazine-based antioxidants include phenothiazine, 10-methinoleph enothiazine, 2-methylphenothiazine, 2 _ trifluoromethylphenothiazine etc. Among these, phenothiazine is particularly preferable. . The phenothiazine-based antioxidant may be only one type or two or more types.

Although the ratio of the antioxidant to the positive electrode material composition is not particularly limited, for example, It is preferably 100 to 50000 ppm, and more preferably 500 to 20000 ppm, relative to poly (poly) (solid content). If the amount of the antioxidant is too small, the decrease in the molecular weight of the polymer can not be sufficiently suppressed, and the battery performance of the lithium secondary battery using the manufactured positive electrode may be insufficient, If the amount of the antioxidant is too large, the antioxidant acts as a plasticizer to cause deterioration in the physical properties of the polymer, or lithium ions react with the antioxidant in the battery, resulting in a decrease in battery performance. May cause

The positive electrode material composition of the present invention preferably also contains a lithium salt as an electrolyte salt required to form a positive electrode. The lithium salt is not particularly limited as long as it is generally used to form a positive electrode, and is not particularly limited. For example, fluorine ion, chlorine ion, bromine ion, iodine ion, heptafluoropropyl Sulfonate ion, bis (trifluoromethanesulfonyl) imide ion, bis (heptafluoropropylsulfonyl) ion, trifluorosulfonate ion, tetrafluoroboronate ion, nitrate ion, As F _6— , PF ₆ , stearyl sulfonate ion, octyl sulfonate ion, dodecylbenzene sulfonate ion, naphthalene sulfonate ion, dodecyl naphthalene sulfonate ion, and 7,7,8,8-tetracyano-p-quinodi Anions selected from the group consisting of methane ions, L i ions and Ranaru salts and the like. These inter _{alia, L i BF 4, L i} PF 6, L i CF 3 S_〇 _{_{_{3, L i C 4 F 9}}} S0 3, L i N (CF 3 S 0 2) 2, L i N (C 2 F ₆ S0 ₂ ) ₂ is more preferred. The electrolyte salt may be only one kind or two or more kinds.

Although the ratio of the electrolyte salt in the positive electrode material composition is not particularly limited, for example, when the polymer is a polyether polymer, the total number of moles of ether oxygen in the polyether polymer, and the mole of the electrolyte salt It is preferable that the value of the number be 1 to 36, more preferably 3 to 33, and still more preferably 6 to 30. If the amount of the electrolyte salt is too small, the ion conductivity will be insufficient and the electrical characteristics will be lowered. On the other hand, if the amount of the electrolyte salt is too large, the ion conductivity improvement effect will not appear if the amount exceeds a certain level. Addition, which is disadvantageous in cost.

The positive electrode material composition of the present invention may contain a solvent. The solvent is one that is finally removed by means such as devolatilization when it is molded into a positive electrode, but by including the solvent in the composition, it becomes possible to form an electrolyte salt etc. The component which is hardly soluble in the polymer can be dissolved in a solvent to facilitate mixing of the components, or the viscosity can be adjusted so as to be easy to handle during transportation / storage and the like. The solvent is not particularly limited, and examples thereof include those mentioned above as solvents which can be used to obtain the above-mentioned ethylene oxide-based polymer. The proportion of the solvent in the positive electrode material composition is not particularly limited, and may be set as appropriate. When the polymer is obtained by a polymerization method using a solvent as in the case of the ethylene oxide-based polymer described above, since the polymerization reaction solution contains a solvent, the polymerization reaction solution is used as it is as a positive electrode material. It may be mixed as a component of the composition, or after the solvent is once removed from the polymerization reaction solution, another solvent may be added as a component of the positive electrode material composition.

The positive electrode material composition of the present invention may further contain, if necessary, an antioxidant other than the above-mentioned essential antioxidant (for example, a general-purpose phenol-based antioxidant), an antioxidant, a light stabilizer, and a lubricant. Additives such as antistatic agent, reinforcing agent, and filler, as appropriate, as long as the effects of the present invention are not impaired You may contain. In addition, the positive electrode material composition may contain, for example, a component contained in a polymerization reaction solution obtained by polymerization when obtaining the polymer.

The positive electrode material composition of the present invention may be in any form such as solution, slurry solution, paste, particles, pellets, fine particles, lumps of desired shape, etc., the polymer, the electrode active material And it can obtain by mixing or kneading each component mentioned above which makes the above-mentioned conductive support agent essential, and devolatilizing or granulating as needed. Also, for example, a solvent may be added again to a composition obtained by granulation once and obtained in the form of particles or pellets to obtain a composition in the form of a solution or a slurry solution.

The method of mixing or kneading the above-described components essentially containing the polymer, the electrode active material, and the conductive auxiliary agent is not particularly limited as long as a conventionally known method is adopted, but the positive electrode material composition is not particularly limited. It is preferable that the polymer, the electrode active material, and the conductive auxiliary be uniformly mixed, and it is desirable to adopt a mixing method or a kneading method capable of uniformly mixing these three components.

When the water content in the positive electrode material composition of the present invention is too large, when the positive electrode formed by molding the composition is used in a battery, the water formed by the reaction of water, metal ion, etc. Although it is not preferable that the material etc. becomes the insulating layer and the cycle characteristics of the battery may be deteriorated, it is not preferable to contain a suitable amount of water in order to obtain good formability when forming the composition into a positive electrode. Sometimes it is better to keep it. In this case, specifically, the water content in the composition is preferably 0.5 to 5%, more preferably 0.1 to 0.8% with respect to the polymer. For the composition, although it varies depending on the composition etc., preferably it is 0.01% to 2%, more preferably 0.5% to 0.5%. As a method of adjusting the water content in the composition to the above-mentioned range, for example, the composition is obtained through devolatilization, water is also removed together with the solvent at the time of devolatilization, or conversely, water is removed while removing. It may be adjusted by volatilization, or may be adjusted by dehumidifying (humidifying) after volatilization.

The positive electrode material composition of the present invention is preferably a coating or molding composition. The positive electrode material composition of the present invention is used for preparation of a positive electrode, and the force of coating to form a film-like positive electrode is for example formed into a desired shape by extrusion and the like to obtain a positive electrode. When the positive electrode material composition is used as a composition for coating or molding, the solvent is added by adjusting the amount thereof so as to obtain an optimum viscosity according to the apparatus used for coating or molding, or the solvent is subjected to devolatilization. The content of the solvent in the composition may be adjusted by adjusting the processing temperature (such as the temperature at the time of mixing and kneading).

The positive electrode material composition of the present invention has a weight-average molecular weight reduction ratio (D _Mw ) of the polymer in the composition defined below of not more than 20% after being left for 0.5 hours, and left for 1 hour It is preferable that it is 30% or less later. More preferably, the reduction rate (D _Mw ) after standing for 0.5 hours is 15% or less, and the reduction rate (D _Mw ) after standing for 1 hour is 20% or less.

The reduction rate of weight average molecular weight of the polymer in the composition (D _Mw ): The weight average molecular weight of the polymer in the composition when left to stand under an air atmosphere at 120 ° C. for a certain period of time is Mw. Mw weight average molecular weight of the polymer in the composition before placing. When you

D _Mw (%) [(Mw.-Mw) / Mw ₀ ] XI 0 0

Is a value represented by If composition decrease rate of the thus 0.5 hours after standing (D _Mw) and left for 1 hour after the reduction rate (D _Mw) is in a range described above, regardless of the storage method, after transportation and storage Even when a positive electrode material is produced and a lithium secondary battery is produced using the positive electrode material, good battery performance can be exhibited. In the present invention, as described above, the above-mentioned decrease is caused by containing at least one antioxidant selected from the group consisting of amine antioxidants, phosphorus antioxidants and phenothiazine antioxidants. Rates can be easily achieved.

In the positive electrode material composition of the present invention, the components required for the positive electrode material are compounded on the surface as needed, for example, in the case of containing no electrolyte salt, and then the positive electrode is formed by the usual method. It can be done. The lithium battery produced by the usual method using the positive electrode obtained in this manner is excellent in various battery performances such as short test and cycle characteristics. Example

EXAMPLES The present invention will be more specifically described below by Examples and Comparative Examples, but the present invention is not limited thereto. Hereinafter, unless stated otherwise, “% by weight” is described as “%” and “weight part” is described as “part”.

[Example 1]

Stirring blades ("Super blend wings" manufactured by Sumitomo Heavy Industries, Ltd.), warm water jacket, air in 100 L reactor equipped with an addition port are replaced with nitrogen gas, and then the reactor is Antioxidant (Bis (4 1 t butyl phenyl) ァ amine: made by Seiyaku Chemical Co., Ltd. “Stearer STARJ” 47. 5 g, Phosphorus-based antioxidant (cyclic neopentane tetrayl bis (2, 6-di-t) Butyl-1-methylphenyl) Phosphate: "Adekastab PEP- 36" made by Asahi Denka Co., Ltd. 47. 5 g, 30.8 kg of toluene, a mixture of an electrode active material and a conductive aid ("Litlated vnd um oxide / carbonblend" US 39.6 kg of A VESTOR LLC were sequentially added. After that, the mixture of electrode active material and conductive aid left in the hopper and piping is flushed with 5 kg of toluene into the reactor, and then the inner blade rotation 75 rpm, outer blade rotation, at normal temperature and pressure for 30 minutes. Stir at 29 rpm and mix uniformly. Then, while stirring at an inner blade rotation of 75 rpm and an outer blade rotation of 29 rpm, a polymer (ethylene oxide “butylene oxide copolymer: weight average molecular weight (Mw) 124, 000, molecular weight distribution (MwZMn) 1. 4) After adding 42.4 kg of the toluene solution (solid content 45%), raise the temperature with a warm water jacket and stir for an additional 2 hours after reaching the internal temperature of 50 ° C to obtain a uniform slurry. The positive electrode material composition was obtained as a solution.

About 1 g of a slurry solution of the obtained positive electrode material composition is placed in an anolomi cup, and 3 pieces of them are put in a dryer of 120 and taken out after 0.5 hours and 1 hour respectively. , And samples. Then, add acetonitrile to each sample so that the concentration of the polymer is 1%, dissolve it, centrifuge at 2000 rpm for 3 minutes, and analyze the supernatant using the GPC apparatus (“HCL_8120” manufactured by TOSOH 1) The weight average molecular weight of the polymer in the sample was determined from a calibration curve prepared using a standard molecular weight sample of polyethylene oxide. As the eluent, water / acetonitrile ( _vo 1 ratio) = 50/50 was used. And Mw the initial weight-average molecular weight of the polymer (124, 000). And the weight average molecular weight of the polymer in the sample is Mw Then, based on the following formula, the rate of decrease in molecular weight relative to the initial weight average molecular weight of the polymer (120,000) was calculated. The results are shown in Table 1.

Molecular weight reduction rate (%) = [(Mw. 1 Mw) ZMw ₀ ] X 100

On the other hand, a pressure reduction line is connected to the reactor while maintaining the internal temperature of the reactor containing the slurry solution of the obtained positive electrode material composition at 50 to 53 ° C. 6. 7 to 13.3 k P a A reduced pressure of (50 to 100 mmHg) was applied, and 29 kg of toluene was distilled off to obtain a slurry solution having a solid content of about 70%. Next, after replacing the air in the KRC kneader main body with nitrogen gas, the internal temperature is set to 90 ° C while rotating the kneader at 38 rpm, and the reactor is transferred to the kneader main body through the gear pump. The slurry solution was fed and degassed under reduced pressure of 34.7 kPa (26 OmmHg) to distill off toluene. Then, a belt cooler was connected to the outlet of the kneader, and the strand extruded from the outlet of the kneader was cooled and received in the pad, and the pad was left at room temperature for 12 hours or more to dry. At this time, from the belt cooler to the pad was covered with a hood to replace the air inside with nitrogen gas throughout the process including drying. Next, using a strand cutter, cover the entire apparatus with a hood and cut the strands into pellets by local evacuation while putting the pellets in a tumble dryer and vacuum drying at room temperature for 12 hours or more. The positive electrode material composition of

The obtained pellet-like positive electrode material composition was left to stand in air at 20 ° C., taken out for an elapsed time shown in Table 2, and used as a sample. Then, add acetonitrile to each sample so that the polymer concentration becomes 1%, stir thoroughly with a Tutch mixer and shaker to dissolve the polymer content, and then filter with a non-aqueous solution (0.45 m). The insoluble matter was filtered, and the obtained filtrate was analyzed by a GPC apparatus ("HCL_8120" manufactured by Tosoh Corporation), and the weight average molecular weight of the polymer in the sample was determined from a calibration curve prepared using a standard molecular weight sample of polyethylene oxide. . As the eluent, water / acetonitrile (v o 1 ratio) = 50/50 was used. And Mw the initial weight average molecular weight of the polymer (124, 000). Assuming that the weight average molecular weight of the polymer in the sample is Mw, the molecular weight reduction rate with respect to the initial weight average molecular weight of the polymer (124, 000) was calculated based on the following formula. The results are shown in Table 2.

Molecular weight reduction rate (◦ /.) = [(Mw.-Mw) / Mw ₀ ] 100

[Examples 2 to 3]

In Example 2, the amounts of amine-based antioxidant and phosphorus-based antioxidant were changed to 19 g of amine-based antioxidant and 19 g of phosphorus-based antioxidant, respectively, and in Example 3, amine-based antioxidant 9 5 g, except that the phosphorus-based antioxidant was changed to 95 g, in the same manner as in Example 1, a positive electrode material composition was obtained as a uniform slurry solution.

Using the slurry solution of the obtained positive electrode material composition, the weight average molecular weight of the polymer in the sample was determined in the same manner as in Example 1. And the molecular weight reduction rate with respect to the initial weight average molecular weight (124, 000) of the polymer was calculated. The results are shown in Table 1.

Comparative Example 1

A positive electrode material composition was obtained as a uniform slurry solution in the same manner as in Example 1 except that the amine antioxidant and the phosphorus antioxidant were not used.

Using the slurry solution of the obtained positive electrode material composition, the weight average molecular weight of the polymer in the sample was determined in the same manner as in Example 1. And the initial weight average molecular weight of the polymer (124, 00 The molecular weight reduction rate was calculated with respect to 0). The results are shown in Table 1.

Comparative Example 2

Amine based antioxidant 47. 5 g and phosphorus based antioxidant 47. 5 g, a phenolic antioxidant (4, 4, monobutylidene bis (6-t-peptyl 3-methylphenol): AP A positive electrode material composition was obtained as a uniform slurry solution in the same manner as in Example 1 except that 95 g of "Yoshinox BB" manufactured by Corporation was used.

On the other hand, in the same manner as in Example 1, a pellet-like positive electrode material composition was obtained using the obtained slurry solution of the positive electrode material composition.

The obtained pellet-like positive electrode material composition is left in air at 20 ° C., taken out for an elapsed time shown in Table 2, and used as a sample as a sample in the same manner as in Example 1 to determine the weight average molecular weight of the polymer in the sample. I asked. Then, the molecular weight reduction rate was calculated relative to the initial weight average molecular weight of the polymer. The results are shown in Table 2.

[Example 4]

After replacing the air in a 100 L reactor (this reactor is called “Reactor A”) equipped with Max Blend wings, a hot water jacket, and an addition port with nitrogen gas, the hot water jacket temperature is raised to 70 ° C. Polymer kept warm and preheated to 80 ° C. (Ethylene oxynobutylene oxide copolymer: weight average molecular weight (Mw) 124, 000, molecular weight distribution (Mw / Mn) 1. 4 42. 4 kg of the toluene solution (solid content 45%) was added. Next, while stirring at a blade rotation of 90 rpm, 4, 08 kg of lithium bis (trifluoromethane sulfone) imid (L i N (CF ₃ S 0 ₂ ) ₂ ) was introduced as a lithium salt from the hopper into the reactor. . Thereafter, the lithium salt remaining in the hopper and the piping was washed with 4 kg of toluene into the reactor, and stirred at an internal temperature of 70 and a blade rotation of 90 rpm for 2 hours.

Next, air in a 100 L reactor (this reactor is referred to as “Reactor B”) equipped with a stirring blade (“Super blend wing”, Sumitomo Heavy Industries, Ltd.), a warm water jacket, and an addition port. The reactor is replaced with a phenol-based antioxidant (4, 4'-butylidebibis (6-t-butyl-1-methylphenol): AP Co., Ltd. "Yoshinox BB") 95 g, toluene 22 39. 6 kg of a mixture of an electrode active material and a conductive additive ("Lithated vandi um oxide / carbon blend", manufactured by US AVE STOR LLC) was sequentially added. After that, the mixture of electrode active material and conductive support left in the hopper and piping is flushed with 4.5 kg of toluene into the reactor, and then the inner blade rotation 75 rpm, normal temperature and pressure for 30 minutes, outer blade Stir at 29 rpm and mix uniformly.

Next, while stirring the inside of the reactor B with the inner blade rotation 75 rpm and the outer blade rotation 29 rpm, the piping of the reactor A is made via the piping previously attached to connect the reactor A and the reactor B. After all the contents (mixed solution of polymer and lithium salt) were charged into reactor B, the temperature was raised with a warm water jacket and stirring was carried out at 50 for 2 hours to obtain a precursor composition as a uniform slurry solution. The

Next, 100 parts of the precursor composition and 32 parts of a 0.25% solution of an acetonitrile solution of an amine-based antioxidant (bis (4-t heptylphenyl) ミン amamine: Steara 1 S TAR manufactured by Seiei Chemical Co., Ltd.) The mixture was stirred at normal temperature with a magnetic stirrer until the antioxidant was dissolved, to obtain a positive electrode material composition as a uniform slurry solution.

Using the slurry solution of the obtained positive electrode material composition, the weight average molecular weight of the polymer in the sample was determined in the same manner as in Example 1. Then, the molecular weight reduction rate was calculated with respect to the initial weight average molecular weight (1 2 4 0 0 0) of the polymer. The results are shown in Table 1.

[Example 5]

In the same manner as Example 4, a precursor composition was obtained.

Next, a precursor composition 100 parts and an amine antioxidant (bis (4 t-butylphenyl) amine: 1 part of 0.5% acetonetonitrile solution of 0.51% acetylene) manufactured by Seiyaku Chemical Co., Ltd. Phosphorus antioxidant (cyclic neopentane tetrayl bis (2, 6-di-t-1-1-1-1 methyl phenyl) Phosphate: 0.5% acetonitrile of Asahi Denka "Adekastab PEP-3 6" The solution 16 was stirred at normal temperature with a magnetic stirrer until the antioxidant was dissolved, to obtain a positive electrode material composition as a uniform slurry solution.

Comparative Example 3

A precursor composition was obtained in the same manner as in Example 4, and the precursor composition was used as a positive electrode material composition.

Using the slurry solution of the obtained positive electrode material composition, the weight average molecular weight of the polymer in the sample was determined in the same manner as in Example 1. And the initial weight average molecular weight of the polymer (1 2 4, 0 0

The molecular weight reduction rate was calculated with respect to 0). The results are shown in Table 1.

【table 1】

* 1: The amount of antioxidant was expressed as a percentage of the solid content of the polymer

【Table 2】

Battery performance>

With regard to the positive electrode material compositions obtained in the above-described Examples and Comparative Examples, the positive electrode material compositions obtained in Examples 4 and 5 and Comparative Example 3 are used as they are in Examples 1 to 3 and Comparative Examples 1 and 2. With respect to the positive electrode material composition obtained in the above, it is preferable that lithium bis (trifuro reomethanesulfone) imid (L i N (CF ₃ S 0 ₂ ) ₂ ) be contained as the electrolyte salt in an amount of 7% by weight in the composition. In addition to the above, they were uniformly mixed and then immediately molded to prepare a positive electrode. Then, a lithium battery was produced using the positive electrode, and the performance (short test and cycle characteristics) of the obtained battery was compared. As a result, any battery based on the positive electrode material composition stored in each example It exhibited better performance than the battery based on the positive electrode material composition stored in each of the comparative examples. Industrial applicability

The positive electrode material composition for a lithium secondary battery according to the present invention is suitably used as a material for producing a positive electrode of a lithium secondary battery.

Claims

The scope of the claims

1. A composition for a positive electrode material essentially comprising a polymer, an electrode active material and a conductive auxiliary, which is selected from the group consisting of an amine-based antioxidant, a phosphorus-based antioxidant and a phenothiazine-based antioxidant. The positive electrode material composition for lithium secondary batteries characterized by including the above antioxidant.

2. The positive electrode material composition for a lithium secondary battery according to claim 1, wherein the antioxidant is an amine-based antioxidant and a phosphorus-based antioxidant.

3. The positive electrode material composition for a lithium secondary battery according to claim 1, which is a composition for coating or molding.

4. The positive electrode material composition for a lithium secondary battery according to any one of claims 1 to 3, wherein the polymer, the electrode active material, and the conductive support agent are uniformly mixed.

5. The positive electrode material composition for a lithium secondary battery according to any one of claims 1 to 4, which further contains a lithium salt as an electrolyte salt.

6. Decrease of weight average molecular weight of polymer in composition defined below (D _Mw ) Force 0.5% or less after leaving for 20 hours, and 30% or less after leaving for 1 hour The positive electrode material composition for a lithium secondary battery according to any one of claims 1 to 5.

Decreasing rate of weight average molecular weight of polymer in the composition (D _Mw ): The weight average molecular weight of the polymer in the composition when left to stand in an air atmosphere at 120 ° C. for a certain period of time is Mw. Mw weight average molecular weight of the polymer in the previous composition. When you

D _Mw (%) = [(Mw _0- Mw) / Mw ₀ ] X 100

Is a value represented by

7. The electrode active material is: L i X V y O z (where x, y and z are independent of each other, and 0 <x≤2, y = (mx + 2z) Zn, and z = (mx + ny) / 2 (however, m is a valence number of Li and n is a valence number of V and is a real number of 4 or more.) 6. A positive electrode material composition for a lithium secondary battery according to any one of 6 to 7.

8. The positive electrode material composition for a lithium secondary battery according to any one of claims 1 to 7, wherein the polymer is an ionically conductive polyether polymer.