Carbon black, carbon black dispersion, all-solid-state lithium-ion secondary battery using the same, and method for producing carbon black

Abstract

To provide carbon black having high dispersibility and storage stability, and to provide a carbon black dispersion having excellent fluidity and dispersion stability, and a composite slurry having good dispersibility even when mixed with an active material. More specifically, to provide a secondary battery having high output, high capacity, and long life, and an electrode film used therein. [Solution] Bulk density X is 0.02 g / cm 3 More than 0.20g / cm 3 a carbon black for an all-solid-state lithium-ion secondary battery, the carbon black having a Zr content of 3 ppm or more and 500 ppm or less; a carbon black dispersion for an all-solid-state lithium-ion secondary battery, the carbon black comprising the carbon black, a dispersant, and a non-aqueous dispersion medium; an electrode film for an all-solid-state lithium-ion secondary battery, and an all-solid-state lithium-ion secondary battery, each using the carbon black dispersion;

Description

[Technical Field]

[0001] The present invention relates to carbon black, a carbon black dispersion, an all-solid-state lithium ion secondary battery using the same, and a method for producing carbon black. [Background technology]

[0002] In recent years, with the spread of electric vehicles and the miniaturization, weight reduction, and improved performance of mobile phones, secondary batteries with high energy density and even higher capacity are required. Under these circumstances, non-aqueous electrolyte secondary batteries using non-aqueous electrolytes, particularly lithium-ion secondary batteries, are used in many devices because of their high energy density and high voltage characteristics.

[0003] Most of the lithium-ion secondary batteries currently in practical use use flammable organic electrolyte solvents, which pose the risk of electrolyte leakage, fire, and explosion. Therefore, there is a need for the development of highly safe lithium-ion secondary batteries that do not pose these risks.

[0004] As such lithium-ion secondary batteries, development is underway on all-solid-state lithium-ion secondary batteries that use a solid electrolyte with lithium ion conductivity. However, all-solid-state lithium-ion secondary batteries consisting of a solid electrolyte, an electrode active material, and a binder have the problem of low electronic conductivity, which prevents them from demonstrating sufficient battery performance.

[0005] To address this issue, an attempt has been proposed to improve electronic conductivity by adding a conductive additive such as carbon black, as in conventional lithium-ion secondary batteries (Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-5398 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in Patent Document 1, a powdered conductive additive is added and mixed with a solid electrolyte, and therefore the conductive additive particles are not sufficiently crushed, and sufficient electronic conductivity cannot be ensured. The problem to be solved by the present invention is to provide carbon black having high dispersibility and storage stability, and also to provide a composite slurry having excellent fluidity and dispersion stability of a carbon black dispersion liquid and good dispersibility even when mixed with an active material. More specifically, the object is to provide a secondary battery having high electronic conductivity and a long life, and an electrode film used therein. [Means for solving the problem]

[0008] Therefore, the inventors of the present invention have conducted extensive research to solve the above problems, and have found that the bulk density X is 0.02 g / cm 3 More than 0.20g / cm 3 The present inventors have found that by using carbon black having a Zr content of 3 ppm or more and 500 ppm or less, it is possible to realize a composition for an all-solid-state lithium ion secondary battery in a uniform composite state free from agglomerations and foreign matter, and that the battery performance of an all-solid-state lithium ion secondary battery using the carbon black as an electrode is improved, thereby completing the present invention.

[0009] That is, the present invention includes the following embodiments: The embodiments of the present invention are not limited to the following.

[0010] [1] Bulk density X is 0.02 g / cm 3 More than 0.20g / cm 3 and a Zr content of 3 ppm or more and 500 ppm or less.

[0011] [2] A carbon black dispersion for an all-solid-state lithium-ion secondary battery, comprising the carbon black according to [1], a dispersant, and a non-aqueous dispersion medium.

[0012] [3] A carbon black resin composition for an all-solid-state lithium-ion secondary battery, comprising the carbon black dispersion according to [2] and a binder resin.

[0013] [4] A composite slurry for an all-solid-state lithium ion secondary battery, comprising the carbon black dispersion according to [2], a binder resin, a solid electrolyte, and an active material.

[0014] [5] An electrode film for an all-solid-state lithium ion secondary battery formed from the composite slurry according to [4].

[0015] [6] A secondary battery comprising a positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode has the electrode film according to [5].

[0016] [7] A method for manufacturing a carbon black having a bulk density X of 0.02 g / cm3, comprising: a step of dry-treating carbon black using a treatment device containing a metal or ceramic medium; the dry-treating method being a pass type, a circulation type, or a batch type; and 3 More than 0.20g / cm 3 and a Zr content of 3 ppm or more and 500 ppm or less.

[0017] [8] The method for producing carbon black for all-solid-state lithium-ion secondary batteries according to [7], wherein a rate of change between the bulk density X after the dry treatment and the bulk density X' before the dry treatment is 10% or more and 1000% or less. Bulk density change rate (%) = (X / X'-1) x 100

[0018] [9] The method for producing carbon black for all-solid-state lithium-ion secondary batteries according to [7] or [8], wherein a rate of change between the powder resistance value Re after the dry treatment and the powder resistance value Re' before the dry treatment is 1% or more and 20% or less. Powder resistance change rate (%) = (Re / Re'-1) x 100

[0019]

[10] A method for producing a carbon black dispersion for an all-solid-state lithium-ion secondary battery, comprising the steps of: mixing the carbon black obtained by the production method according to any one of [7] to [9] with a dispersant and a non-aqueous dispersion medium; and dispersing the carbon black. [Effects of the Invention]

[0020] The present invention can provide carbon black having high dispersibility and storage stability, a carbon black dispersion having excellent fluidity and dispersion stability, and a composite slurry having good dispersibility even when mixed with an active material. Furthermore, it can provide a secondary battery having high electronic conductivity and a long life, and an electrode film used therein. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 shows the carbon black of Example 2 by SEM. [Figure 2] FIG. 2 is a diagram showing the carbon black of Comparative Example 1 by SEM. [Figure 3] FIG. 3 is a diagram showing the carbon black of Comparative Example 2 by SEM. DETAILED DESCRIPTION OF THE INVENTION

[0022] In this specification, carbon black may be abbreviated as "CB." In this specification, carbon black dispersion may be referred to as "CB dispersion" or simply as "dispersion."

[0023] Carbon black The carbon black of this embodiment has a bulk density X of 0.02 g / cm 3 and the Zr content is 3 ppm or more and 500 ppm or less. This results in a carbon black with excellent dispersibility, and a carbon black dispersion using this carbon black can achieve both flowability and storage stability.

[0024] The bulk density X of CB contributes to the wettability of the liquid medium, and when CB is processed using a dry grinding device or the like, it can be used as an index of the degree of processing of the CB.

[0025] In particular, when using CB as a conductive material in battery applications, one of the most important factors is to utilize the CB's unique structure in the CB dispersion. When improving the wettability of CB in a liquid medium by dry processing or the like, if the processing intensity is too high, the formation of CB aggregates is promoted, and as a result, the CB cannot be sufficiently dissolved in the non-aqueous solvent, which may result in a decrease in conductivity. In addition, while it is possible to disperse the CB aggregates with high intensity, the resulting dispersion may have poor storage stability due to the collapse of the CB structure itself. When the bulk density of CB is 0.02 g / cm 3 More than 0.20g / cm 3 By keeping the CB content at or below 100%, it is possible to appropriately control the strength of CB aggregation, the size of the aggregates, etc. Furthermore, the CB can be dispersed appropriately in a non-aqueous solvent without collapsing its structure, and the required conductivity can be maintained. Therefore, by forming an electrode film using this dispersion, a well-developed conductive network can be formed in the electrode film.

[0026] The bulk density X of CB is 0.02 g / cm 3 or more, preferably 0.04 g / cm 3 More preferably, it is 0.05 g / cm or more. 3 That's all. Also, 0.20 g / cm 3 or less, preferably 0.14 g / cm 3 or less, more preferably 0.13 g / cm 3 or less, and particularly preferably 0.12 g / cm 3 The following is the result.

[0027] The bulk density X of CB in the present invention is the loose bulk density when loosely packed. The bulk density X can be determined by allowing CB to freely fall into an open-top container of a predetermined capacity until it overflows, leaving it to stand, leveling off the CB powder that has risen on the upper surface with a leveling plate, measuring the mass of the CB, and dividing the mass by the volume of the container.

[0028] A specific method for measuring bulk density X is to allow CB powder to freely fall into a 30 ml stainless steel cylindrical container, remove any excess mass from the top of the container, and then calculate the mass of the CB powder and divide it by the volume of the container. To break up any agglomerates formed during storage of the CB powder, a sufficient amount of sample for the test is passed through a 0.5 mm sieve to allow the resulting sample to flow freely into the measurement container until it overflows.

[0029] The Zr content in the CB of this embodiment is 3 ppm or more and 500 ppm or less. It is preferably 400 ppm or less, more preferably 300 ppm or less, and even more preferably 200 ppm or less. It is also preferably 4 ppm or more and more preferably 5 ppm or more. From the viewpoint of weakening the van der Waals forces between CB structures and further improving the dispersion stability of the CB, the Zr content in the CB is preferably 5 ppm or more, even more preferably 10 ppm or more, even more preferably 15 ppm or more, and may be 20 ppm or more, 30 ppm or more, or 40 ppm or more. For example, the Zr content in the CB is preferably 5 ppm or more and 500 ppm or less, more preferably 10 ppm or more and 300 ppm or less, and even more preferably 15 ppm or more and 200 ppm or less. Within these ranges, the dispersion stability of the CB dispersion can be further improved, resulting in further improved battery performance.

[0030] The Zr content of CB can be measured by inductively coupled plasma (ICP) optical emission spectroscopy.

[0031] Furthermore, the zirconium (Zr) contained in CB, detected as elemental zirconium by ICP atomic emission spectrometry, may be from materials (e.g., milling media) used in pretreatment processes such as dry processing of CB, from wear of disperser components, or by adding a zirconium-containing compound such as zirconia (zirconium oxide) to CB. The Zr content of CB can be adjusted by adjusting the type of media, additives / coatings, and dry processing conditions (e.g., time, intensity, and processing temperature) used in the dry milling equipment. Furthermore, the Zr content in CB can be partially reduced by centrifugal separation, taking advantage of the difference in specific gravity between CB and Zr. Zr has excellent toughness and heat resistance, and most zirconia exists at a size that cannot be separated from CB. Therefore, it is difficult to completely remove Zr once it is mixed in at any stage of the manufacturing process, from CB pretreatment to CB dispersions, CB resin compositions containing them, composite slurries, and ultimately secondary batteries. Therefore, it is important to appropriately control the Zr content of CB using the above-mentioned methods, especially for secondary battery applications. The carbon black of the present invention has excellent effects because it is a carbon black composition containing Zr.

[0032] Although the reason why the dispersibility of CBs improves when the bulk density X and Zr content are both within the specified ranges is unclear, it is speculated as follows. It is speculated that the presence of Zr weakens the van der Waals forces between CBs, thereby improving the dispersion stability of the CBs. A Zr content of 3 ppm or more eliminates the need for strong force to uniformly disperse the CBs, which form a structure through van der Waals forces, and suppresses increases in the powder resistivity of the CBs and the volume resistivity of the electrode containing the CBs. Furthermore, a Zr content of 500 ppm or less prevents excessive Zr from inhibiting the adsorption of the dispersant to the CBs, resulting in an unstable dispersion. It also suppresses decreases in discharge capacity due to Zr adhesion to the active material. More preferably, the Zr content is 5 ppm or more and 500 ppm or less. Meanwhile, as mentioned above, bulk density contributes to the wettability of the liquid medium to the carbon black. By appropriately controlling the bulk density, the CBs can be uniformly and effectively dispersed while maintaining a certain level of CB structure, resulting in the formation of a well-developed conductive network. By keeping both the bulk density and the Zr content within the specified ranges, it is possible to maximize the electrical conductivity inherent to CB while achieving both the dispersibility and stability over time of CB.

[0033] <Method of manufacturing carbon black> The CB of this embodiment is not limited by its manufacturing method and can be specified by its physical property values. CB can be prepared by pretreating CB manufactured according to a standard manufacturing method or a conventionally known CB. The pretreatment method for CB is not particularly limited, and may include surface treatment using chemicals or heat treatment. Furthermore, one or more pretreatment methods may be used in combination, but at least pulverization is preferred. The physical properties of carbon black can be controlled by optimizing the pulverization conditions.

[0034] For example, the CB of this embodiment can be obtained by pulverizing CB having readily available physical properties. The pulverization process may be either wet pulverization or dry pulverization, and pulverization media may be used. Dry pulverization is preferred because it is easier to control the physical properties of the CB, and dry pulverization using pulverization media is more preferred. The pulverization media may be made of metal or ceramic materials, and are not particularly limited. The components fed into the pulverizer may be untreated CB alone, or optional components such as lubricants, dispersants, and surface treatment agents may be added. Dry pulverization is preferred, but if necessary, a liquid medium may be fed into the pulverizer together with the untreated CB. Note that the pulverization of CB in this specification is not limited to breaking down CB particles into smaller particles, but also includes a state in which bulky CB is compacted by applying pressure using media or the like to reduce voids, as shown in FIG. 1.

[0035] When using a grinding device, the treatment may be performed using any of the batch, pass, and circulation methods. However, due to the ease of control of the physical properties of CB, pass or circulation methods are preferred, with circulation being more preferred. The batch method is a method in which treatment is performed using only the dispersing device itself without using piping or the like. The pass method is a method in which the grinding device itself is equipped with a tank that supplies CB via piping and a tank that receives CB, and the CB passes through the grinding device itself. The circulation method is a method in which the CB that has passed through the dispersing device itself is returned to the tank that supplies CB and treated while circulating. In both methods, the longer the treatment time, the more the grinding process progresses, so the pass or circulation can be repeated until the desired state is achieved, and the treatment volume can be increased by changing the tank size or treatment time. Specific examples of grinding devices include bead mills, ball mills, and attrition mills, with ball mills and attrition mills being considered batch treatments. Examples of pass or circulation grinding devices include a dry continuous grinding device equipped with a horizontal cylindrical tank and a high-speed rotating arm that stirs the grinding media. When zirconia beads are used as the grinding media, it is preferable to use a pass-type or circulation-type dry continuous grinding device in order to adjust the Zr content of the CB to an appropriate range.

[0036] In a pass-type or circulation-type milling process, the desired CB can be obtained by controlling the mass (flow rate) of CB fed into the mill per unit time, the processing time, the peripheral speed, the type, diameter, and amount of milling media, the milling temperature, and other factors. In one example, a circulating bead mill is used to feed the CB raw material and perform dry milling. Methods for controlling the milling temperature include cooling with a cooling jacket attached to the milling chamber body, cooling outside the bead mill system, and a combination of these. From the perspective of cooling efficiency, cooling with a cooling jacket attached to the milling chamber body is preferred. The milling temperature can be measured by installing a thermometer in any piping. Specifically, it can be confirmed by measuring the powder outlet temperature using a thermometer installed at the outlet of the bead mill.

[0037] When dry grinding is performed using grinding media, the grinding media are preferably made of ceramic materials, with zirconia being more preferred, to prevent the incorporation of metal impurities such as iron into the CB and to enhance grinding strength. The grinding media diameter is preferably 1 mm or more, more preferably 3 mm or more, and even more preferably 5 mm or more. A grinding media diameter of at least the above range increases the collision energy with the CB, thereby improving dry grinding efficiency. Furthermore, the grinding media diameter is preferably 15 mm or less, more preferably 10 mm or less, and even more preferably 8 mm or less. A grinding media diameter of at most the above range reduces wear due to collisions between grinding media. Repeated use of grinding media used in dry grinding of CB can cause wear and cracking, which can lead to poor dispersion and contamination. Therefore, it is preferable to classify and clean the grinding media before use. When using zirconia beads as grinding media, the bead diameter should be greater than 5 mm and less than 10 mm to more appropriately adjust the Zr content of the CB. When two or more types of beads with significantly different diameters are used in combination, the beads collide with each other and wear, which can easily lead to a large amount of Zr being mixed into the CB, so it is best to keep the bead diameter within ±1 mm. This tendency is exacerbated in dry milling bead mills, so when using a bead mill, it is preferable to use one type of zirconia beads, and it is even more preferable to keep the bead diameter of the zirconia beads within ±1 mm.

[0038] In the pass-type or circulation-type grinding process, the desired CB can be easily obtained by adjusting the peripheral speed and processing time. The specific values ​​vary depending on the scale of the processing equipment, but as an example, in the case of a processing equipment with a grinding chamber capacity of 10 L, the desired CB can be easily obtained by setting the processing time to 1 to 5 hours and the peripheral speed to 4 to 5 m / s. As an example, the bulk density of the CB before processing is 0.01 to 0.05 g / cm. 3 g / cm 3 It is preferable to use CB of this type because it is easy to obtain the desired CB.

[0039] Here, we will explain in detail the necessity and effects of CB pretreatment, particularly dry treatment. When the bulk density of CB is low, the bulkiness of the CB results in poor wettability with the dispersion medium, which can lead to poor handling, increased dispersion viscosity, and reduced uniformity. Furthermore, the composite slurry produced using such a CB dispersion also becomes highly viscous and non-uniform, potentially reducing the coatability and uniformity of the electrode film. On the other hand, if the bulk density becomes too high through pretreatment, etc., the preparation of the CB dispersion (specifically, its ease of preparation and wettability with the dispersion medium) tends to be easier and the finished viscosity of the dispersion tends to be lower. However, this also causes CB aggregation, increasing the proportion of coarse CB that is difficult to disintegrate, making it difficult to form an appropriate conductive network in the electrode film. Pretreatment, etc., partially compacts the CB structure, improving wettability with the dispersion medium. Furthermore, high-intensity dispersion to break down the aggregated coarse CB particles can also disrupt the CB structure, making it difficult to form a well-developed conductive network and potentially resulting in poor conductivity. Furthermore, if the viscosity of the composite slurry is too low, migration can occur during the drying process during electrode film fabrication, potentially resulting in nonuniform electrode films. Furthermore, if the CB is pretreated to an extent that its bulk density is too high, the Zr may inhibit the adsorption of the dispersant onto the CB, and there is also the risk of Zr adhering to the active material, resulting in a decrease in discharge capacity. In light of these issues, by appropriately controlling both the bulk density and the Zr content, we can achieve a CB dispersion with excellent dispersibility, stability, and conductivity. Furthermore, electrode films with well-developed conductive networks can be obtained, resulting in secondary batteries with high output, high capacity, and long life.

[0040] The bulk density of CB is 0.02 g / cm 3 ~0.20g / cm 3 By adjusting the Zr content of the CB to within the range of 3 ppm to 500 ppm, the CB of the present invention having excellent performance can be obtained.

[0041] Furthermore, the present inventors have found that when dry treatment is used as a pretreatment for CB, it is necessary to improve the wettability to a certain level while maintaining the structure of the CB to a certain extent. Therefore, they have found that CB with excellent dispersibility and electrical conductivity can be obtained by setting the bulk density X of the CB and the Zr content of the CB within the above ranges as indicators for determining the degree of treatment of the CB, in other words, the end point of the dry treatment of the CB.

[0042] That is, when dry treatment is employed as the pretreatment of CB, the pretreatment is carried out while controlling the bulk density X of the CB and the Zr content of the CB. The dry treatment conditions for CB are preferably adjusted appropriately by evaluating the dispersibility of the CB dispersion and the conductivity of the composite slurry and electrode film using the same. However, for the reasons mentioned above, the bulk density X and the Zr content may be measured during the dry treatment and used directly as indicators for obtaining the desired treatment state.

[0043] The rate of change between the bulk density X after dry-milling and the bulk density X' before dry-milling is preferably 10% or more and 1000% or less, more preferably 10% or more and 200% or less, and even more preferably 10% or more and 105% or less. By keeping the rate of change in bulk density within the above range, it is possible to obtain CB that exhibits better dispersibility and high conductivity. The rate of change in bulk density can be calculated using the following formula: Bulk density change rate (%) = (X / X'-1) x 100

[0044] The rate of change between the powder resistivity Re after dry milling and the powder resistivity Re' before dry milling is preferably 1% to 100%, more preferably 2% to 75%, and even more preferably 3% to 50%. By keeping the rate of change in powder resistivity within the above range, a CB exhibiting better dispersibility and high conductivity can be obtained. The rate of change in powder resistivity can be calculated using the following formula: Powder resistance change rate (%) = (Re / Re'-1) x 100

[0045] The CB before dry pulverization is not particularly limited. The average particle size is preferably 10 to 100 nm, more preferably 15 to 75 nm, and even more preferably 20 to 50 nm. The particle size within the above range has the advantage of facilitating the formation of a conductive path when mixed with an active material. The average particle size refers to the average particle size of primary particles. Furthermore, the CB before dry pulverization has a bulk density of 0.001 g / cm. 3 ~0.18g / cm 3 is preferred, and 0.005 g / cm 3 ~0.16g / cm 3 More preferably, 0.01 g / cm 3 ~0.15g / cm 3 The oil absorption of CB before dry pulverization is not particularly limited, but if the oil absorption is high, a solvent may be added to the CB to an extent that the powder state is maintained during dry processing.

[0046] <<Carbon black dispersion>> The CB dispersion of this embodiment contains the above-mentioned CB, a dispersant, and a non-aqueous dispersion medium. Details of the CB are as described above.

[0047] <Dispersant> The CB dispersion contains a dispersant. There are no particular limitations on the dispersant, but one that can stabilize the dispersion of CB in the CB dispersion is preferred. While either a resin-type dispersant or a surfactant can be used as the dispersant, resin-type dispersants are preferred because they have a strong adsorption power to CB and provide good dispersion stability. Depending on the properties required for the dispersion of CB, an appropriate type of dispersant can be used in an appropriate amount.

[0048] As the resin-type dispersant, a (meth)acrylic polymer, a polymer derived from an ethylenically unsaturated hydrocarbon, a cellulose derivative, a copolymer thereof, or the like can be used.

[0049] Examples of polymers derived from ethylenically unsaturated hydrocarbons include polyvinyl alcohol resins, polyvinylpyrrolidone resins, polyacrylonitrile resins, nitrile rubbers, styrene rubbers, etc. Examples of polyvinyl alcohol resins include polyvinyl alcohol, modified polyvinyl alcohols having functional groups other than hydroxyl groups (e.g., acetyl groups, sulfo groups, carboxy groups, carbonyl groups, amino groups), polyvinyl alcohols modified with various salts, other anion- or cation-modified polyvinyl alcohols, and polyvinyl acetals (polyvinyl acetoacetal, polyvinyl butyral, etc.) modified with aldehydes (acetoacetal-modified, butyral-modified, etc.). Polyacrylonitrile resins may be polyacrylonitrile homopolymers, polyacrylonitrile copolymers, or modified versions thereof. Preferred examples include polyacrylonitrile resins having at least one selected from the group consisting of active hydrogen groups such as hydroxyl groups, carboxyl groups, primary amino groups, secondary amino groups, and mercapto groups, basic groups, and alkyl groups derived from (meth)acrylic acid alkyl esters or α-olefins. For example, the acrylonitrile copolymer described in JP 2020-163362 A can be used. Nitrile rubbers include acrylonitrile butadiene rubber and hydrogenated acrylonitrile butadiene rubber. Styrene rubbers include styrene-butadiene random or block copolymers and their hydrogenated products, styrene-butadiene-styrene block copolymers and their hydrogenated products, and styrene-ethylene-butylene-styrene block copolymers and their hydrogenated products. Examples of the cellulose derivatives include cellulose acetate, cellulose butyrate, cyanoethyl cellulose, ethylhydroxyethyl cellulose, nitrocellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, carboxymethyl cellulose, and copolymers thereof.In addition, dispersants described in International Publication No. 2008 / 108360, JP 2018-192379, JP 2019-087304, JP 2020-011934, and JP 2009-026744 may be used, but are not limited to these. In particular, methyl cellulose, ethyl cellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyacrylonitrile homopolymer, polyacrylonitrile copolymer, and hydrogenated acrylonitrile butadiene rubber are preferred. Polymers in which other substituents have been introduced into a portion of these polymers, modified polymers, etc. may also be used.

[0050] The weight-average molecular weight of the resin-type dispersant is preferably 500,000 or less, more preferably 300,000 or less, from the viewpoint of the affinity balance between the CB (dispersed material) and the non-aqueous dispersion medium, and from the viewpoint of resistance to the electrolyte. It is also preferably 3,000 or more, more preferably 5,000 or more. The resin-type dispersant may be used alone or in combination of two or more. The weight-average molecular weight is the weight-average molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC).

[0051] Commercially available polyvinyl alcohol resins include Kuraray Poval (polyvinyl alcohol resin manufactured by Kuraray), Gohsenol, Gohsenex (polyvinyl alcohol resin manufactured by Nippon Synthetic Chemical Industry), Denka Poval (polyvinyl alcohol resin manufactured by Denka), and J-Poval (polyvinyl alcohol resin manufactured by Nippon Acetate Poval Corporation), and various grades are available. Modified polyvinyl alcohols having various functional groups are also available. Polyvinyl alcohols synthesized by known synthesis methods may also be used. Specific examples of commercially available polyvinylpyrrolidone resins include Luvitec K17 (K value: 15.0 to 19.0, low molecular weight), K30 (K value: 27.0 to 33.0), K90 (K value: 88.0 to 92.0), K90HM (K value: 92.0 to 96.0, high molecular weight) (manufactured by BASF Japan), K15, K30, K90, K120 (manufactured by ISP), polyvinylpyrrolidone K30 (K value: 27.0 to 33.0), K90 (K value: 88.0 to 96.0) (manufactured by Nippon Shokubai), and PVP. Examples include K12 (K value 10-14), K15 (K value 13-19), K30 (K26-K35), K60 (K value 50-62), and K90 (K value 88-100) (manufactured by DSP Gokei Food & Chemical). To prevent an increase in viscosity, the polyvinylpyrrolidone preferably has a K value of 150 or less, more preferably a K value of 100 or less, and even more preferably a K value of 85 or less. Commercially available nitrile rubbers include Therban (hydrogenated nitrile rubber manufactured by Arlanxeo), Baymod (nitrile rubber manufactured by Arlanxeo), Zetpole (hydrogenated nitrile rubber manufactured by Nippon Zeon), and Nipole NBR (nitrile rubber manufactured by Nippon Zeon), and various grades with different nitrile ratios, hydrogenation rates, molecular weights, etc. are available. Furthermore, those synthesized by known synthesis methods may also be used. Commercially available styrene rubbers include Nipol NS (SBR manufactured by Zeon), TAIPOL SEBS (SEBS manufactured by TSRC), Septon (hydrogenated SEBS manufactured by Kuraray), Tufprene (SBS manufactured by Asahi Kasei), and other trade names, and various grades with different styrene ratios, hydrogenation rates, molecular weights, etc. Alternatively, rubbers synthesized by known synthesis methods may be used.

[0052] Surfactants may be used in place of or in addition to the resin-type dispersants described above. Surfactants are classified into anionic, cationic, amphoteric ionic surfactants and nonionic surfactants.

[0053] The CB dispersion may further contain a base. The inclusion of a base in the CB dispersion is preferable because it enhances the wettability of the CB in the dispersion medium, improving dispersibility or dispersion stability. The base to be added can be at least one selected from the group consisting of inorganic bases, inorganic metal salts, organic bases, and organic metal salts. The total amount of these bases is preferably 0.001 to 0.1 mass% and more preferably 0.005 to 0.05 mass% relative to the total amount of the CB dispersion. Adding too much base can cause corrosion of the dispersion device and / or the inside of the battery. The water content of the added base is preferably less than 5 mass%, more preferably less than 3 mass%, and even more preferably less than 2 mass%. If the added base contains a large amount of water, the adsorption of the dispersant to the CB may be reduced, making it difficult to maintain the CB in a stable state in the non-aqueous dispersion medium. By setting the water content within the above range, it is possible to prevent the problem of gelling of the composite slurry produced by mixing with the active material, or the problem of moisture remaining in the positive electrode causing deterioration of the positive electrode due to the generation of acids such as HF. The problem of moisture remaining in the positive electrode causing deterioration of the positive electrode due to the generation of acids such as HF is also a problem. Furthermore, the presence of moisture in alkali metal hydroxides such as LiOH can easily cause gelling of the paste containing the positive electrode active material during positive electrode preparation, making electrode formation difficult.

[0054] Examples of inorganic bases and inorganic metal salts include chlorides, hydroxides, carbonates, nitrates, sulfates, phosphates, borates, and ammonium hydroxide of alkali metals or alkaline earth metals. Among these, hydroxides or alkoxides of alkali metals or alkaline earth metals are preferred from the viewpoint of easy supply of cations. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of alkaline earth metal hydroxides include calcium hydroxide and magnesium hydroxide. Among these, it is more preferable to use at least one selected from the group consisting of lithium hydroxide, sodium hydroxide, and potassium hydroxide. The metal contained in the inorganic base may be a transition metal.

[0055] Examples of organic bases include primary, secondary, and tertiary amine compounds (e.g., alkylamines and aminoalcohols) having 1 to 40 carbon atoms, which may have a substituent, and organic hydroxides. Examples of primary alkylamines having 1 to 40 carbon atoms, which may have a substituent, include alkylamines such as propylamine, butylamine, isobutylamine, octylamine, 2-ethylhexylamine, and laurylamine; aminoalcohols such as 2-aminoethanol and 3-aminopropanol; and 3-ethoxypropylamine. Examples of secondary alkylamines having 1 to 40 carbon atoms, which may have a substituent, include alkylamines such as dibutylamine, diisobutylamine, N-methylhexylamine, and dioctylamine, and aminoalcohols such as 2-methylaminoethanol. Examples of tertiary alkylamines having 1 to 40 carbon atoms, which may have a substituent, include alkylamines such as triethylamine, tributylamine, N,N-dimethylbutylamine, N,N-diisopropylethylamine, dimethyloctylamine, trioctylamine, and dimethyldecylamine, triethanolamine, and 2-(dimethylamino)ethanol. The organic hydroxide is a salt containing an organic cation and a hydroxide ion. Examples of the organic hydroxide include trimethyl-2-hydroxyethylammonium hydroxide, tetramethylammonium hydroxide, trimethylphenylammonium hydroxide, 3-trifluoromethyl-phenyltrimethylammonium hydroxide, and benzyltrimethylammonium hydroxide. Among these, from the viewpoint of the action on CB, it is more preferable to use at least one selected from the group consisting of 2-aminoethanol, 3-aminopropanol, triethanolamine, and trimethyl-2-hydroxyethylammonium hydroxide.

[0056] Examples of organic metal salts include alkali metal alkoxides and alkali metal acetates. Examples of alkali metal alkoxides include lithium methoxide, lithium ethoxide, lithium propoxide, lithium t-butoxide, lithium n-butoxide, sodium methoxide, sodium ethoxide, sodium propoxide, sodium t-butoxide, sodium n-butoxide, potassium methoxide, potassium ethoxide, potassium propoxide, potassium t-butoxide, and potassium n-butoxide. Among these, sodium t-butoxide is preferred from the viewpoint of easy supply of cations. The metal contained in the organic base may be a transition metal.

[0057] <Water content of carbon black dispersion> The carbon black dispersion of the present invention is used in an all-solid-state lithium-ion secondary battery. As described above, the all-solid-state lithium-ion battery uses a solid electrolyte having lithium ion conductivity as the electrolyte. Since the solid electrolyte is characterized by hydrolysis or the like caused by moisture, resulting in a decrease in ionic conductivity, the carbon black dispersion used in the all-solid-state lithium-ion secondary battery is required to contain as little moisture as possible. Therefore, the water content of the carbon black dispersion of the present invention is preferably 1000 ppm or less, more preferably 500 ppm or less, and most preferably 100 ppm or less.

[0058] Methods for adjusting the water content of the carbon black dispersion within the preferred range include known methods such as reducing the water content of the raw materials used, using a low-polarity solvent as the solvent, preparing the dispersion in a low-water environment, distilling the dispersion after preparation, and removing water by adding a dehydrating agent or blowing dry gas into the dispersion.

[0059] <Non-aqueous dispersion medium> The CB dispersion contains a non-aqueous dispersion medium as a dispersion medium. The non-aqueous dispersion medium in the present invention is preferably low-polar. Examples of low-polarity solvents in the present invention include non-polar solvents and solvents with a relative dielectric constant of less than 10 and / or a solubility of less than 1 g per 100 g of water at 20°C.

[0060] Examples of low polarity solvents that can be used include alkane solvents such as heptane and pentane, ester solvents such as butyl butyrate and butyl valerate, ketone solvents such as dibutyl ketone and diisobutyl ketone, and aromatic solvents such as toluene and tetralin.

[0061] The non-aqueous dispersion medium is preferably an ester solvent, a ketone solvent, or an aromatic solvent, from the viewpoint of the solubility of the dispersant or binder resin, the wettability of the CB to the dispersion medium, and the water content of the dispersion.

[0062] The CB dispersion may contain optional components such as wetting agents, wetting penetrants, leveling agents, and other additives as needed, as long as the objectives of the present invention are not impaired. The optional components can be added at any timing, such as before preparing the CB dispersion, during mixing, after mixing, or a combination thereof.

[0063] Since the inclusion of optional components does not impair the object of the present invention and the CB dispersion is substantially free of active materials, the content of CB and dispersant in the CB dispersion is 60% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the non-volatile components of the CB dispersion, i.e., the solid content of the CB dispersion, and may be 100% by mass or less.

[0064] The dispersion of the present invention can contain carbon nanotubes as other conductive materials other than CB. The carbon nanotubes are preferably contained in the CB dispersion within a range that does not impair the effects of the present invention. Preferably, it is 5% by mass or less, and more preferably 3% by mass or less, based on the total mass of the CB dispersion. If the above range is satisfied, even if carbon nanotubes are contained, the dispersion state of CB can be controlled and high dispersibility and fluidity can be maintained better.

[0065] The stage of adding carbon nanotubes to the CB dispersion is not particularly limited and may be before, after, simultaneously with, or a combination of these, the addition of CB. As another example of the method for producing a CB dispersion containing carbon nanotubes, there is a method of adding carbon nanotubes before, after, simultaneously with, or a combination of these, the addition of a binder resin to the CB dispersion. In this method, it is preferable that the carbon nanotubes are added in a state where the CB is dispersed in the CB dispersion. Alternatively, a combination of these methods may be used. That is, carbon nanotubes may be further added before, after, simultaneously with, or a combination of these, the addition of a binder resin to the CB dispersion containing carbon nanotubes.

[0066] <Method for producing CB dispersion> The CB dispersion of the present embodiment is characterized by including a step of mixing and dispersing the above CB, a dispersant, and a non-aqueous dispersion medium. For example, it is preferable to produce by performing a dispersion treatment on CB, a dispersant, and a non-aqueous dispersion medium using a dispersion device to finely disperse them. The dispersion device used for performing such a treatment is not particularly limited. Note that the dispersion treatment may arbitrarily adjust the addition timing of the materials used and may be a multi-stage treatment of two or more times.

[0067] Examples of dispersing devices used to disperse CB include kneaders, two-roll mills, three-roll mills, planetary mixers, ball mills, horizontal bead mills, vertical bead mills, annular bead mills, attritors, high-shear mixers, high-pressure homogenizers, and ultrasonic homogenizers. Among these, a high-shear mixer, a horizontal bead mill, or a combination of these is preferred to finely disperse CB in the CB dispersion and obtain favorable dispersibility. In particular, a high-shear mixer is preferably used in the initial dispersion step to promote wetting of the CB and disintegrate coarse particles, followed by the use of a bead mill disperser to disperse the CB while maintaining its structure.

[0068] Dispersion methods using a dispersing device include batch dispersion, pass dispersion, and circulation dispersion. Any of these methods may be used, or two or more methods may be combined. Batch dispersion is a method in which dispersion is performed using only the dispersing device itself, without using piping or the like. Because it is easy to handle, it is preferred for small-scale production. Pass dispersion is a dispersion method in which the dispersing device itself is equipped with a tank that supplies the dispersion liquid via piping and a tank that receives the dispersion liquid, and the dispersion passes through the dispersing device itself. Furthermore, circulation dispersion is a method in which the dispersion liquid that has passed through the dispersing device itself is returned to the tank that supplies the dispersion liquid and dispersed while circulating. In both methods, the longer the processing time, the more the dispersion progresses; therefore, the pass or circulation can be repeated until the desired dispersion state is achieved, and the processing volume can be increased by changing the tank size or processing time. Pass dispersion is preferred over circulation dispersion because it is easier to achieve a uniform dispersion state. Circulation dispersion is preferred over pass dispersion because the operation and production equipment are simpler. In the dispersion step, the disintegration of aggregated particles, the loosening, wetting, stabilization, etc. of the conductive material proceed sequentially or simultaneously, and the final dispersion state differs depending on how these steps proceed, so it is preferable to control the dispersion state in each dispersion step by using various evaluation methods. For example, the control can be performed by the methods described in the Examples.

[0069] The dispersing device used to disperse the CB dispersion may be equipped with a heat exchanger or a coolant supply mechanism for cooling the CB dispersion. By pre-cooling the CB dispersion or crude dispersion that has reached a high temperature after dispersion, it is possible to suppress the generation of bubbles in the CB dispersion and also to suppress the remaining solid content on the walls of the dispersion tank, etc. The liquid temperature of the CB dispersion is not particularly limited, but is preferably controlled to 25 to 75°C, and more preferably 30 to 65°C.

[0070] <<Carbon black resin composition>> The carbon black resin composition of this embodiment may contain the carbon black dispersion and a binder resin. Details of the carbon black dispersion are as described above. That is, the carbon black resin composition may contain carbon black, a dispersant, a non-aqueous dispersion medium, and a binder resin. The carbon black resin composition may further contain an optional component. Details are as described above. The carbon black resin composition can be used as a resin composition for an all-solid-state lithium-ion secondary battery.

[0071] The binder resin is not particularly limited as long as it is typically used as a binder resin for paints, and can be appropriately selected depending on the purpose. The binder resin may be a resin that bonds between substances such as active materials, CB, and other conductive materials. Examples of binder resins include homopolymers or copolymers containing ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinyl pyrrolidone, etc. as structural units; polyurethane resins, polyester resins, phenolic resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicone resins, and fluororesins; cellulose resins such as carboxymethyl cellulose or salts thereof; elastomers such as hydrogenated or non-hydrogenated styrene-butadiene rubber and fluororubber; and conductive resins such as polyaniline and polyacetylene. Modified versions of these resins and copolymers of these resins may also be used. The binder resin may be used alone or in combination of two or more. Among these, when used as a binder resin for the positive electrode of a secondary battery, homopolymers or copolymers having fluorine atoms in the molecule, such as polyvinylidene fluoride, polyvinyl fluoride, polytetrafluoroethylene, and modified products and copolymers thereof, are preferred in terms of durability. Furthermore, when used as a binder resin for the negative electrode of a secondary battery, CMC (carboxymethyl cellulose or its salt), hydrogenated or non-hydrogenated styrene-butadiene rubber, polyacrylic acid, and the like, which have good adhesion, are preferred.

[0072] In the CB resin composition, the binder resin content is preferably 0.5 to 30 mass %, more preferably 0.5 to 25 mass %, based on the total amount of nonvolatile components of the CB resin composition.

[0073] The CB resin composition is preferably obtained by adding a binder resin to a CB dispersion and mixing them. The binder resin may be used in the form of a solution (varnish) in which the binder resin is pre-dispersed or dissolved in a dispersion medium or the like, or in a state without a dispersion medium. It is more preferable to use the binder resin in the form of a solution in which the binder resin is pre-dispersed or dissolved. Pre-dispersion or dissolution prevents insufficient dissolution of the binder resin and aggregation of the CB dispersion, making it possible to provide a uniform CB resin composition. The form of the binder resin is not particularly limited and may be, for example, pellets, powder, granules, flakes, chunks, chopped fibers, or the like.

[0074] There are no particular limitations on the method for adding the binder resin to the CB dispersion, but it is preferable to add the binder resin while stirring the CB dispersion using a stirring device. There are no particular limitations on the stirring device, but a disper (stirring blade) or the like is generally used. There are various types of stirrers, such as propeller-type and turbine-type, and there are no particular limitations on their shape as long as they can stir the CB resin composition homogeneously. The stirring speed can be adjusted appropriately by adjusting the size and rotation speed of the stirring blade. There are no particular limitations on the stirring speed as long as it is within the range allowed by the actual operating process.

[0075] <<Slurry for composite materials for all-solid-state lithium-ion secondary batteries>> The composite slurry of this embodiment may contain the carbon black dispersion, a binder resin, a solid electrolyte, and an active material. The composite slurry of another embodiment may contain the carbon black resin composition and an active material. Details of the carbon black resin composition are as described above. That is, the composite slurry may contain carbon black, a dispersant, a non-aqueous dispersion medium, a binder resin, a solid electrolyte, and an active material. The composite slurry may further contain optional components. Details are as described above. The active material may be either a positive electrode active material or a negative electrode active material. The composite slurry can be used as a composite slurry for an electrode of an all-solid-state lithium-ion secondary battery, and may be either a positive electrode composite slurry for an all-solid-state lithium-ion secondary battery or a negative electrode composite slurry for an all-solid-state lithium-ion secondary battery.

[0076] The composite slurry may contain other optional components as needed, as long as they do not impair the object of the present invention. The optional components can be added at any time, such as before preparing the composite slurry, during mixing, after mixing, or a combination thereof. The optional components may be those described above for the CB resin composition.

[0077] The active material may be a positive electrode active material or a negative electrode active material. In this specification, the positive electrode active material and the negative electrode active material may be simply referred to as "active material." Active materials are materials that are the basis of battery reactions and are broadly classified into positive electrode active materials and negative electrode active materials based on electromotive force. The composite slurry is preferably in a slurry state to improve uniformity and processability.

[0078] <Solid electrolyte> In the present invention, a wide range of solid electrolytes can be used as the solid electrolyte material for all-solid-state lithium ion secondary batteries. Specifically, for example, Li2S-SiS2, Li2S-P2S3, Li2 SExamples of suitable solid electrolytes include sulfide-based solid electrolytes such as LiI-LiS-SiS, LiI-LiS-P2S5, LiI-LiS-P2O5, LiI-LiPO4-P2S5, LiS-P2S5, and LiPS4; and oxide-based solid electrolytes such as LiO-BO-P2O5, LiO-SiO2, LiO-BO, and LiO-BO-ZnO. These solid electrolytes can be used alone or in combination of two or more. In the present invention, sulfide-based solid electrolytes are preferred, and those prepared using a raw material composition containing LiS and P2S5 are more preferred. It is particularly preferred that the molar ratio of LiS to P2S5 in the raw material composition be within the range of LiS:P2S5 = 70:30 to 80:20.

[0079] The content of the solid electrolyte in the composite slurry for an all-solid-state lithium-ion secondary battery is preferably 20 to 80 mass %, more preferably 30 to 70 mass %, and even more preferably 40 to 60 mass %. By including the solid electrolyte in this range, good drying properties of the electrode layer can be obtained.

[0080] <Cathode active material> The positive electrode active material is not particularly limited, but for example, metal compounds such as metal oxides and metal sulfides that can reversibly dope or intercalate lithium ions can be used. For example, lithium manganese composite oxides (e.g., Li x Mn2O4 or Li x MnO2), lithium nickel composite oxides (e.g., Li x NiO2), lithium cobalt composite oxide (Li x CoO2), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2), lithium nickel manganese cobalt composite oxide (e.g., Li x Ni y Co z Mn1-y-z (O2), spinel-type lithium manganese nickel composite oxide (e.g., Li x Mn 2-y Ni y O4), etc., composite oxide powders of lithium and transition metals, lithium phosphate oxide powders having an olivine structure (e.g., Li x FePO4, Li x Fe 1-y Mn y PO4, Li x CoPO4, etc.), manganese oxide, iron oxide, copper oxide, nickel oxide, vanadium oxide (e.g., V2O5, V6O 13 ), etc., transition metal oxide powders such as titanium oxide, iron sulfate (Fe2(SO4)3), transition metal sulfide powders such as TiS2 and FeS, etc. Here, x, y, z are numbers, 0 < x < 1, 0 < y < 1, 0 < z < 1, 0 < y + z < 1. These cathode active materials can also be used alone or in combination of two or more. Among these active materials, in particular, active materials containing Ni and / or Mn (especially when the total amount of Ni and / or Mn in the transition metal is 50 mol% or more) tend to have high basicity due to components derived from raw materials or elution of metal ions, and due to this influence, gelation of the binder resin and deterioration of the dispersion state are likely to occur. Therefore, in the case of a battery containing an active material containing Ni and / or Mn, this embodiment is particularly effective.

[0081] <Negative electrode active material> The negative electrode active material is not particularly limited. For example, metallic Li capable of reversibly doping or intercalating lithium ions, or an alloy thereof, a tin alloy, a silicon alloy negative electrode, Li X TiO2, Li X Fe2O3, Li X Fe3O4, Li XMetal oxide systems such as WO2, conductive polymers such as polyacetylene and poly-p-phenylene, artificial graphite such as highly graphitized carbon materials, or carbonaceous powders such as natural graphite, and resin-fired carbon materials can be used. However, x is a number and 0 < x < 1. These negative electrode active materials can also be used alone or in combination of two or more. In particular, when using a silicon alloy negative electrode, although the theoretical capacity is large, the volume expansion is extremely large. Therefore, it is preferably used in combination with artificial graphite such as highly graphitized carbon materials, or carbonaceous powders such as natural graphite, and resin-fired carbon materials.

[0082] The content of CB in the composite material slurry is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and even more preferably 0.05% by mass or more based on the mass of the active material (assuming the mass of the active material is 100% by mass). Also, it is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. If it exceeds the above range, the filling amount of the active material in the electrode will decrease, leading to a reduction in the battery capacity. If it is below the above range, the conductivity of the electrode and the battery may be insufficient.

[0083] The content of the dispersant in the composite material slurry is preferably 0.01% by mass or more, more preferably 0.02% by mass or more based on the mass of the active material (assuming the mass of the active material is 100% by mass). Also, it is preferably 10% by mass or less, more preferably 5% by mass or less.

[0084] The content of the binder resin in the composite material slurry is preferably 0.1% by mass or more, more preferably 0.3% by mass or more based on the mass of the active material (assuming the mass of the active material is 100% by mass). Also, it is preferably 20% by mass or less, more preferably 10% by mass or less.

[0085] The nonvolatile content in the composite slurry is preferably 40% by mass or more, more preferably 50% by mass or more, based on the mass of the composite slurry (the mass of the composite slurry being 100% by mass), and is preferably 90% by mass or less, more preferably 85% by mass or less.

[0086] A preferred method for preparing the composite slurry is to add a solid electrolyte and an active material to the CB resin composition and stir the mixture. The stirring device used for stirring is not particularly limited. Examples of the stirring device that can be used include a disperser, a homogenizer, and a planetary centrifugal mixer. [Example]

[0087] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples as long as it does not depart from the gist of the invention. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass".

[0088] In the examples and comparative examples, the following CBs were used. Li-250: DENKA BLACK Li-250, average particle size 35nm Li435: Denka BLACK Li-435, average particle size 23 nm VXC72R: CABOT VULCAN XC-72R, average particle size 30 nm

[0089] In the examples and comparative examples, the following dispersants were used. HNBR: Therban 1707 VP (ARLANXEO, hydrogenated nitrile butadiene rubber) PVB: BL-10 (Sekisui Chemical Co., Ltd., polyvinyl butyral) Vinyl chloride and vinyl acetate: Solvine C (Vinyl chloride and vinyl acetate copolymer resin, manufactured by Nissin Chemical Industry Co., Ltd.)

[0090] In the examples and comparative examples, the following solvents were used. Butyl butyrate Cyclohexane ·toluene

[0091] In the examples and comparative examples, the following binder resins were used. ·SBR (styrene butadiene rubber) PVDF (Polyvinylidene Fluoride)

[0092] <cb> The types of CB and the manufacturing conditions are shown in Table 1. The end point indicator for the dry pulverization of CB in the examples was a bulk density of 0.02 g / cm. 3 ~0.20g / cm 3 The Zr content was set to be within the range of 3 ppm to 500 ppm.

[0093] (Example 1: CB1) In a 60 L dynamic mill, 8 mm diameter zirconia beads were used as grinding media at a filling rate of 70%, and 60 kg of Li-250 was supplied as raw material CB at a flow rate of 12 kg / h (hour). The milling process was carried out for 5 hours using a circulation milling method at a peripheral speed of 4 m / s (seconds), yielding CB1. A sample was taken out and found to have a bulk density of 0.08 g / cm. 3 The Zr content was 8 ppm, and it was confirmed that both the bulk density and Zr content were within the specified range, and the treatment process was terminated. During the treatment process, cooling was performed by flowing cooling water (10°C) into the vessel (flow rate 10 L / min) so that the powder temperature at the outlet was 45±10°C.

[0094] (Examples 2 to 8: CB2 to 8) CB was dry-pulverized in the same manner as in Example 1 under the conditions listed in Table 1 to obtain CB2 to 8. In each treatment step, cooling was performed by flowing cooling water (10°C) into the vessel (flow rate 10 L / min) so that the powder temperature at the outlet was 45±10°C.

[0095] (Example 9: CB9) A glass bottle was charged with 18 parts of Li-250 as the raw material CB and 160 parts of 1.25 mm diameter zirconia beads as media, and the mixture was dispersed in a paint conditioner at a vibration speed of 750 rpm for 0.5 hours. The zirconia beads were filtered off to obtain CB9. The bulk density and Zr content were as shown in Table 1.

[0096] (Example 10: CB10) 18 parts of Li-250, 18 parts of butyl butyrate, and 160 parts of 1.25 mmφ zirconia beads as media were charged into a glass bottle and dispersed for 0.5 hours at a vibration speed of 750 times / minute using a paint conditioner. Although butyl butyrate was added as a solvent, the oil absorption was high and it maintained a powder form. Therefore, like CB9, the zirconia beads were filtered off using a sieve and then dried under reduced pressure at 100 °C to obtain CB10. The bulk density and Zr content were as shown in Table 1.

[0097] (Comparative Example 1: Comparative CB1) The untreated Li-250 without performing a grinding process was used as Comparative CB1.

[0098] (Comparative Example 2: Comparative CB2) A 60 L dynamic mill was charged with zirconia beads having a diameter of 8 mm at a filling rate of 70% as grinding media, and 60 kg of Li-250 was supplied as raw material CB at a flow rate of 12 kg / h. It was processed for 30 hours by a circulating grinding method at a peripheral speed of 4 m / s to obtain Comparative CB2. In the processing step, cooling was performed by flowing cooling water (10 °C) into the vessel (flow rate 10 L / min) so that the outlet powder temperature became 45 ± 10 °C.

[0099] (Comparative Example 3: Comparative CB3) A 60 L dynamic mill was charged with zirconia beads having a diameter of 8 mm at a filling rate of 70% as grinding media, and 60 kg of Li-250 was supplied as raw material CB at a flow rate of 12 kg / h. It was processed for 60 hours by a circulating grinding method at a peripheral speed of 2 m / s to obtain Comparative CB2. In the processing step, cooling was performed by flowing cooling water (10 °C) into the vessel (flow rate 10 L / min) so that the outlet powder temperature became 45 ± 10 °C.

[0100] ≪Physical Properties and Evaluation of CB≫ The physical properties of CB were measured and evaluated by the following method. The obtained results are shown in Table 1.

[0101] <Content of Zr> The Zr content of CB was measured by the following procedure. First, 0.1 ± 0.02 g of CB was placed in a digestion vial, and nitric acid was added thereto, followed by digestion with a microwave sample digestion apparatus. Generation was added to the digestion solution and adjusted to 25 ml, filtered through a membrane filter, and the filtrate was analyzed with an ICP analyzer to determine the Zr content (ppm).

[0102] <Apparent density X of CB> The apparent density was measured according to JIS K 5101-12-1 by the following procedure. First, before measurement, CB was pretreated by vacuum drying at a pretreatment temperature of 305 °C and a pretreatment time of 18 to 21 hours. Next, the aggregates formed during the storage of the CB powder were crushed, and a sufficient amount of the sample for the test was prepared by passing through a 0.5 mm sieve in order to freely flow into the measuring container until it overflows. The prepared CB powder was freely dropped into a 30 ml stainless steel cylindrical container and accommodated. After shaving off the raised part on the upper surface of the container, the mass of the CB powder was determined and divided by the volume of the container to obtain the apparent density (g / cm 3 ).

[0103] <Apparent resistivity of CB> Using a powder resistivity measuring device (manufactured by Nitto Seiko Analytic Co., Ltd.: Loresta GP Powder Resistivity Measurement System MCP-PD-51), with a sample mass of 0.8 g, using a powder probe unit (four-probe ring electrode, electrode interval 5.0 mm, electrode radius 1.0 mm, sample radius 12.5 mm), with the applied voltage limiter set to 90 V, the volume resistivity [Ω·cm] of the conductive powder under various pressures was measured. The value of the powder resistivity of CB at a density of 1 g / cm 3 was evaluated.

[0104] Also, in Table 1, the apparent density change rate is the value obtained by the following formula from the apparent density X after dry grinding and the apparent density X' before dry grinding, and the powder resistivity change rate is the value obtained by the following formula from the powder resistivity Re after dry grinding and the powder resistivity Re' before dry grinding. Apparent density change rate (%) = (X / X' - 1) × 100 Powder resistivity change rate (%) = (Re / Re' - 1) × 100

[0105] [Table 1]

[0106] <Carbon black dispersion> Example 11 A carbon black dispersion was prepared as follows by sequentially adding the materials according to the ingredients and composition shown in Table 2. First, butyl butyrate was placed in a stainless steel jacketed tank and heated to 50°C. HNBR was added while stirring with a disperser, and the mixture was stirred for 1 hour to dissolve the HNBR. Next, CB (CB1) was gradually added while stirring with a disperser. A high-shear mixer (L5M-A, manufactured by Silverson) equipped with a square-hole high-shear screen was used, and batch dispersion was carried out for 5 minutes at a speed of 8,000 rpm. Next, the dispersion liquid was fed from the jacketed tank via a pipe to a bead mill (SC100, manufactured by Nippon Coke Co., Ltd.). The bead diameter was 1.25 mm, the bead filling rate was 60%, the peripheral speed was 10 m / s, and the feed rate was 800 g / min. Carbon black dispersion 1 was obtained.

[0107] (Examples 12 to 28, Comparative Examples 4 to 6) Carbon black dispersions 2 to 18 and comparative carbon black dispersions 1 to 3 were obtained in the same manner as in Example 1, except that the materials, compositions, and dispersion conditions were changed according to Table 2.

[0108] (Method for measuring viscosity of dispersion liquid) Viscosity measurements were performed using a Brookfield viscometer ("BL" manufactured by Toki Sangyo Co., Ltd.) at a dispersion temperature of 25°C. After thoroughly stirring the dispersion with a spatula, the viscosity was immediately measured at a Brookfield viscometer rotor speed of 60 rpm. The rotors used for the measurements were No. 1 for viscosity less than 100 mPa·s, No. 2 for viscosity between 100 and 500 mPa·s, No. 3 for viscosity between 500 and 2000 mPa·s, and No. 4 for viscosity between 2000 and 10000 mPa·s. The lower the viscosity, the better the dispersibility, and the higher the viscosity, the worse the dispersibility.

[0109] (Evaluation of dispersion stability) The dispersion of the present invention also has good storage stability. The storage stability of the dispersion was evaluated by calculating the rate of change in viscosity after storage at 40°C for 7 days, measured in the same manner as above, based on the viscosity of the dispersion immediately after dispersion. The evaluation criteria were as follows: Viscosity change rate less than 5%: ++++ (good) Viscosity change rate: 5% to less than 10%: +++ (usable) Viscosity change rate: 10% to less than 50%: ++ (usable) Viscosity change rate of 50% or more: - (bad, unusable) Solution gels, settles, or separates: (bad, unusable)

[0110] [Table 2]

[0111] <Preparation of Carbon Black Resin Composition> Example 29 3.0 parts of SBR (styrene butadiene rubber) and 15.9 parts of butyl butyrate were weighed out and placed in a plastic container as a binder resin, and the mixture was stirred at 2,000 rpm for 5 minutes using a centrifugal mixer (Thinky ARE-310 Awatori Rentaro) to dissolve the binder resin. Next, 40 parts of CB Dispersion 1 were weighed out and placed in a plastic container, and the mixture was further stirred at 2,000 rpm for 30 seconds using a centrifugal mixer to obtain Carbon Black Resin Composition 1.

[0112] (Examples 30 to 47, Comparative Examples 7 to 9) Carbon black resin compositions 2 to 19 and comparative carbon black resin compositions 1 to 3 were obtained in the same manner as in Example 29, except that the materials and compositions were changed according to Table 3.

[0113] <Evaluation of Carbon Black Resin Composition> The carbon black resin composition of the present invention achieves a good dispersion state and good compatibility with the binder, and also has good storage stability. The storage stability of the carbon black resin composition was evaluated by calculating the rate of change in viscosity after storage at 40°C for 7 days, measured in the same manner as above, relative to the viscosity immediately after preparation. The evaluation results are shown in Table 3. The evaluation criteria were as follows: Viscosity change rate less than 5%: ++++ (good) Viscosity change rate: 5% to less than 10%: +++ (usable) Viscosity change rate: 10% to less than 50%: ++ (usable) Viscosity change rate of 50% or more: - (bad, unusable) Solution gels, settles, or separates: (bad, unusable)

[0114] [Table 3]

[0115] <Preparation of composite slurry and electrode film for all-solid-state lithium-ion secondary batteries> Example 48 8.5 parts of solid electrolyte 1 and 41.8 parts of butyl butyrate were weighed into a plastic container and mixed for 2 minutes at 2,000 rpm using a planetary centrifugal mixer (Thinky's Awatori Rentaro, ARE-310). Next, 40 parts of NMC was added and mixed for 2 minutes at 2,000 rpm using the planetary centrifugal mixer. Next, 9.8 parts of carbon black resin composition 1 was added and mixed for 2 minutes at 2,000 rpm using the planetary centrifugal mixer, yielding positive electrode composite slurry 1 for all-solid-state lithium-ion secondary batteries. The resulting composite slurry was applied to a 20 μm-thick aluminum foil current collector using an applicator, and then dried on a hot plate at 150°C ± 5°C for 25 minutes to produce an electrode with a coating weight per unit area of ​​20 mg / cm. 2 Then, a heat press was used to perform a pressure treatment at 120°C to obtain electrode film 1. The preparation of the electrode slurry and the preparation of the electrode film were carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or less.

[0116] (Examples 49 to 69, Comparative Examples 10 to 12) Except for changing the materials and compositions according to Table 4, composite slurries 2 to 22 and electrode films 2 to 22, comparative composite slurries 1 to 3 and comparative electrode films 1 to 3 were obtained in the same manner as in Example 48.

[0117] <Resistance of positive electrode film for all-solid-state batteries> The volume resistivities of electrode films 1 to 22 and the comparative electrode film were measured by the four-probe method using a Loresta GP (manufactured by Nitto Seiko Analytech Co., Ltd.) in accordance with JIS-K7194. For the resistance measurements, a measurement electrode was used in which the coating substrate used in the preparation of each electrode was changed from aluminum foil to a PET substrate. The relative values ​​(%) based on the volume resistivity of comparative electrode film 1 prepared in Comparative Example 10 were determined and evaluated according to the following criteria. Electrode resistance characteristics criteria: Less than 50%: +++ (Excellent) 50% to less than 70%: ++ (Excellent) 70% to less than 90%: + (Good) 90% to less than 100%: - (bad, unusable) Over 100%:-- (very poor, unusable)

[0118] [Table 4]

[0119] In the examples and comparative examples, the following solid electrolytes were used. ·Solid electrolyte 1: Li3PS4, manufactured by Sigma-Aldrich ·Solid electrolyte 2: SSE-10(Li 10 SnP2S 12 ), manufactured by NEI Corporation

[0120] In the examples and comparative examples, the following active materials were used. Positive electrode active material 1: CellSeed NMC (LiNi 0.6 Co 0.2 Mn 0.2 )O2, manufactured by Nippon Chemical Industry Co., Ltd. Positive electrode active material 2: LFP: HED (trademark) LFP-400 (lithium iron phosphate, manufactured by BASF)

[0121] <Assembly of a cell for evaluating the positive electrode of an all-solid-state secondary battery> (Examples 70 to 91, Comparative Examples 13 to 15) The previously prepared electrode films 1-22 and comparative electrode films 1-3 were punched out to a diameter of 10 mm and used as working electrodes. The working electrode and 50 mg of solid electrolyte 1 powder were placed in a cylindrical container for an all-solid-state battery evaluation cell, in that order, and pressurized at 50 MPa to form a solid electrolyte layer on the working electrode. Metal indium foil and metal lithium foil were placed in that order as counter electrodes on the opposite side of the solid electrolyte layer from the working electrode. The cell was then assembled and secured with bolts, and then tightened using a torque wrench to the specified pressure, yielding evaluation cells 1-22 and comparative evaluation cells 1-3. The assembly of the evaluation cells was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or below.

[0122] <Evaluation of cycle characteristics of positive electrodes in all-solid-state secondary batteries> The fabricated all-solid-state secondary battery positive electrode evaluation cell was placed in a thermostatic chamber at 25°C and subjected to charge / discharge measurements using a charge / discharge device (Hokuto Denko Corporation, SM-8). Constant-current, constant-voltage charging (cutoff current: 0.02C) was performed at a charge rate of 0.2C with a charge cutoff voltage of 4.2V, followed by constant-current discharging at a discharge rate of 0.2C with a discharge cutoff voltage of 2.5V. This procedure was repeated 300 times. 1C was defined as the current value required to charge or discharge the theoretical capacity of the positive electrode in 1 hour. The cycle characteristics can be expressed as the ratio of the 3rd 0.2C discharge capacity to the 300th 0.2C discharge capacity, using the following equation: (Formula 1) Cycle characteristics = 300th 0.2 C discharge capacity / 3rd 0.2 C discharge capacity × 100 (%)

[0123] The cycle characteristics of Evaluation Cells 1 to 22 were calculated as relative values ​​(%) based on the cycle characteristics of Comparative Evaluation Cell 1, and were evaluated according to the following criteria. The results are shown in Table 5. Cycle characteristics criteria: 200% or more: +++ (excellent) 150% to less than 200%: ++ (Excellent) 100% or more but less than 150%: + (Good) Less than 100% (poor):- (poor, unusable)

[0124] [Table 5]

[0125] As shown in Tables 4 and 5, the Examples exhibited superior electrode resistance and battery characteristics compared to the Comparative Examples. It is believed that the carbon material contained in the electrode film of the Examples maintained its structure, allowing for uniform formation of conductive paths within the electrode film, leading to reduced electrode resistance and improved cycle characteristics. On the other hand, in the Comparative Examples, due to the collapse of the structure, excessive aggregation, etc., and the lack of an appropriate amount of Zr, it was not possible to form a stable dispersion state, resulting in non-uniform conductive paths within the electrode, which is believed to have led to increased electrode resistance and worsened cycle characteristics. From the above, it was demonstrated that when the carbon black of the present invention is used, excellent battery characteristics can be exhibited.< / cb>

Claims

1. Bulk density X is 0.02 g / cm ３ 0.20g / cm or more ３ and a Zr content of 3 ppm or more and 500 ppm or less.

2. A carbon black dispersion for an all-solid-state lithium ion secondary battery, comprising the carbon black according to claim 1, a dispersant, and a non-aqueous dispersion medium.

3. A carbon black resin composition for an all-solid-state lithium ion secondary battery, comprising the carbon black dispersion according to claim 2 and a binder resin.

4. A composite slurry for an all-solid-state lithium ion secondary battery, comprising the carbon black dispersion according to claim 2, a binder resin, a solid electrolyte, and an active material.

5. An electrode film for an all-solid-state lithium ion secondary battery formed from the composite slurry according to claim 4.

6. An all-solid-state lithium ion secondary battery comprising a positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode has the electrode film according to claim 5.

7. The method includes a step of dry-treating carbon black using a treatment device including a metal or ceramic medium, the dry treatment being any one of a pass type, a circulation type, and a batch type, and the carbon black after the dry treatment has a bulk density X of 0.02 g / cm. ３ 0.20g / cm or more ３ and a Zr content of 3 ppm or more and 500 ppm or less.

8. 8. The method for producing carbon black for an all-solid-state lithium-ion secondary battery according to claim 7, wherein a rate of change between the bulk density X after the dry treatment and the bulk density X' before the dry treatment is 10% or more and 1000% or less. Bulk density change rate (%) = (X / X'-1) x 100

9. 8. The method for producing carbon black for an all-solid-state lithium-ion secondary battery according to claim 7, wherein a rate of change between a powder resistivity Re after the dry treatment and a powder resistivity Re′ before the dry treatment is 1% or more and 20% or less. Powder resistance change rate (%) = (Re / Re'-1) x 100

10. A method for producing a carbon black dispersion for an all-solid-state lithium-ion secondary battery, comprising: mixing and dispersing the carbon black obtained by the production method according to any one of claims 7 to 9 with a dispersant and a non-aqueous dispersion medium.

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