JP5345300B2 - Composite cathode material for lithium ion battery and battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite positive electrode material for a lithium ion battery particularly excelling in high-rate discharge performance of the battery; and slurry, a positive electrode and a battery using it. <P>SOLUTION: This composite positive electrode material for a lithium ion battery contains (a) a positive electrode active material, (b) a conductive substance having a primary particle diameter of 10-100 nm and/or (c) a fibrous conductive substance having a fiber diameter of 1 nm to 1 &mu;m, and (d) a conductive substance having an aspect ratio of 2-50. The composite positive electrode material for a lithium ion battery is obtained by mixing the conductive substance of (d) with a composition containing the positive electrode active material of (a), the conductive substance of (b) and/or the conductive substance of (c), which composition is obtained by dispersing the positive electrode active material of (a), the conductive substance of (b) and/or the conductive substance of (c) in a solvent to a state where they are forcibly dispersed, and thereafter coagulating them. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a positive electrode active material, a composite positive electrode material for a lithium ion battery containing a conductive material, and a slurry, a positive electrode and a battery using the same.

  In recent years, electric vehicles, hybrid vehicles, fuel cell vehicles, and the like have attracted attention against the background of soaring petroleum resources and the growing global environmental protection movement, and some of them have been put into practical use. In these drive systems, a secondary battery is indispensable as an auxiliary power source and the like, and a high-power secondary battery that can cope with sudden start / acceleration of an automobile is desired. Moreover, a secondary battery with a high energy density is desired from the viewpoint of weight load on the vehicle and improvement in fuel consumption. From such a background, a lithium ion secondary battery that has the highest energy density among the secondary batteries and can exhibit high output is promising.

  In a lithium ion secondary battery, an electrolytic solution containing a lithium salt in a non-aqueous solvent is used, and a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material are separated via a separator. . In the positive electrode, since the conductivity of the positive electrode active material itself is low, a conductive material such as carbon black is added to improve the conductivity.

Generally, the positive electrode as described above is manufactured by applying and drying a slurry obtained by mixing an active material such as LiMn ₂ O _4, a conductive material such as carbon black, a binder, and a solvent onto a metal foil as a current collector. Is done. As a result, the fine structure of the positive electrode has a structure in which particles of a positive electrode active material having low conductivity and particles of a conductive material having a smaller particle diameter are dispersed and bonded.

  In the positive electrode of a lithium ion secondary battery, lithium is occluded in the positive electrode active material at the time of discharge. At that time, discharge proceeds by the action of lithium ions diffusing to the positive electrode side and electrons conducted from the positive electrode current collector. . Further, at the time of charging, electrons and ionized lithium are released from the positive electrode active material. For this reason, it is very important to select a conductive material with high conductivity and a fine composite structure of a positive electrode active material and a conductive material as factors affecting battery characteristics, particularly high-speed discharge performance (high output). It becomes.

  For these reasons, several attempts have been made to improve the fine composite structure related to the positive electrode. For example, Patent Document 1 discloses a positive electrode material in which a positive electrode active material and a conductive material are mixed and a surface of the positive electrode active material is coated at a coverage of 15% or more by a dry method of applying compressive shear stress. Proposed. Further, it is disclosed that graphite having a particle diameter of 1 to 20 μm is added when a positive electrode is produced using this.

  In Patent Document 2, an attempt is made to improve the conductive path by adding carbon fiber to the positive electrode active material.

  Further, Patent Document 3 proposes a positive electrode formed of a composite material obtained by adding and mixing both carbon black and carbon fiber to a positive electrode active material. Patent Document 4 discloses that a composite material in which both spherical graphite and fibrous carbon are added to and mixed with the positive electrode active material reduces the resistance by covering the surface of the positive electrode active material with spherical graphite, Forming a conductive path between materials is disclosed.

JP 2004-14519 A JP 2004-103392 A JP 2004-179019 A JP 11-345507 A

  However, in the positive electrode material disclosed in Patent Document 1, it is difficult to control the coverage, and the conductive material is likely to be densely coated on the surface of the positive electrode active material, so that the Li ion path is blocked. High-speed discharge performance is difficult to improve. Moreover, although the electroconductivity of the positive electrode active material is improved by the coating, the electroconductivity of the positive electrode obtained is not sufficient, and it has been found that the effect of improving the electroconductivity is not so great even when graphite is used in combination.

  Moreover, since the carbon fiber described in Patent Document 2 generally has poor contact efficiency with the positive electrode active material, sufficient performance cannot be obtained with respect to the conductivity of the positive electrode.

  Furthermore, since the positive electrode disclosed in Patent Document 3 is formed using a slurry in which carbon black, carbon fiber, a positive electrode active material, and a binder are dry mixed and then a solvent is added and dispersed in the solvent, the positive electrode active material It has been found that the fine composite structure in which the conductive material and the conductive material are not properly arranged cannot be formed, and the obtained positive electrode does not exhibit sufficient performance with respect to the high-speed discharge performance.

  Further, as disclosed in Patent Document 4, even if an attempt is made to form a conductive path between positive electrode active materials coated with spheroidal graphite by fibrous carbon, the aspect ratio of the fibrous carbon (Example of Patent Document 4) In general, 75 is used), so that it is difficult to dispose properly between the positive electrode active materials (particularly difficult with dry mixing), and a positive electrode active material having no appropriate pore capacity is obtained. It has been found that the high-speed discharge performance is insufficient.

  Accordingly, an object of the present invention is to provide a composite positive electrode material for a lithium ion battery excellent in high-speed discharge performance of the battery, and a slurry, a positive electrode and a battery using the same.

  The inventors of the present invention have prepared a composition obtained by aggregating a positive electrode active material and a specific conductive material in a solvent until they are forcibly dispersed, and a conductive material having a specific aspect ratio. The composite positive electrode material obtained by mixing has been found to improve particularly the high-speed discharge performance of the battery, and the present invention has been completed.

  That is, the present invention includes (a) a positive electrode active material, (b) a conductive material having a primary particle diameter of 10 to 100 nm, and / or (c) a fibrous conductive material having a fiber diameter of 1 nm to 1 μm, And (d) a composite positive electrode material for a lithium ion battery containing a conductive material having an aspect ratio of 2 to 50, wherein the positive electrode active material of (a), the conductive material of (b), And / or the conductive material of (c) is dispersed to a state where it is forcibly dispersed and then agglomerated to obtain the positive electrode active material of (a), the conductive material of (b) and / or (c). It is related with the composite positive electrode material for lithium ion batteries obtained by mixing the composition containing these conductive substances, and the conductive substance of (d). In addition, the various physical-property values in this invention are values specifically measured by the method as described in an Example.

  Furthermore, the present invention relates to a slurry, a positive electrode and a battery using the composite positive electrode material for lithium ion battery as described above.

  ADVANTAGE OF THE INVENTION According to this invention, the composite positive electrode material for lithium ion batteries which is excellent in the high-speed discharge performance of a battery, a slurry using this, a positive electrode, and a battery can be provided.

  That is, according to the present invention, the primary particles of the positive electrode active material are adhered to the surface of the positive electrode active material by aggregation after forced dispersion, or the composite particles having a structure of being wrapped with the aggregate of primary particles are formed. It is considered that the contact between the active material and the conductive material is increased, and electrons are sufficiently conducted to the surface of the positive electrode active material through the conductive material, thereby improving the conductivity. Further, by mixing a conductive material having a specific aspect ratio (for example, carbon black in a daisy chain) into the composite particle and interposing it between the composite particles, while forming a sufficient conductive path, It is considered that the permeation becomes smooth and a structure excellent in ion diffusion of Li ions is obtained. As a result, it is considered that a higher current can be passed during discharge than in a conventional Li ion secondary battery, and a Li ion battery excellent in high-speed discharge characteristics can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail.

“Composite cathode materials for lithium-ion batteries”
The composite positive electrode material for lithium ion batteries of the present invention (hereinafter referred to as “composite positive electrode material”) includes (a) a positive electrode active material, and (b) a conductive material having a primary particle size of 10 to 100 nm, and / or (c 1) A fibrous conductive material having a fiber diameter of 1 nm to 1 μm, and (d) a conductive material having an aspect ratio of 2 to 50.

  The composite positive electrode material of the present invention is obtained by dispersing the positive electrode active material of (a), the conductive material of (b), and / or the conductive material of (c) in a solvent until the state is forcibly dispersed. A composition containing the positive electrode active material (a) obtained by agglomeration, the conductive material (b) and / or the conductive material (c), and the conductive material (d) Is obtained. As a rough structure of the composite positive electrode material, for example, composite particles formed by attaching the conductive material (b) and / or the conductive material (c) to the surface of one or more positive electrode active materials (a) And a structure in which the conductive material (d) is interposed between the composite particles.

  In the composite positive electrode material of the present invention, “composite particles” in a form in which a conductive substance is in contact with the surface of the positive electrode active material can be formed. This composite particle has two modes. The first mode is obtained by adhering primary particles of a conductive material on the surface of a positive electrode active material. The second mode is a method in which a positive electrode active material is applied to a conductive material. Are encased in an aggregate of primary particles. In the present invention, a composite particle in which the first aspect and the second aspect are combined is preferable. In this case, a composite structure in which the composite particle of the first aspect is wrapped with an aggregate of primary particles of a conductive material is formed.

  The conductive material and the positive electrode active material are aggregates of unit particles that are chemically stable in a solvent, and are forcibly ultrasonicated in the solvent, preferably with an ultrasonic wave having a frequency of 15 to 25 kHz and an output of 100 to 500 W. By dispersing, it is considered that the particles are dispersed to a state close to unit particles. This unit particle is referred to as “primary particle” in the present invention.

As the positive electrode active material of (a), any conventionally known material can be used. For example, a Li · Mn composite oxide such as LiMn ₂ O _4, a Li · Co composite oxide such as LiCoO ₂ , or LiNiO _2. Li · Ni-based composite oxides such as LiFeFe _2, etc., and Li _x CoO ₂ , Li _x NiO ₂ , MnO ₂ , LiMnO ₂ , Li _x Mn ₂ O ₄ , Li _{x Mn 2-y O 4,} α-V 2 O 5, TiS 2 and the like. Of these, LiMn ₂ O ₄ , LiCoO ₂ , and LiNiO ₂ are preferable and LiMn ₂ O ₄ is more preferable from the viewpoint of excellent thermal stability, capacity, and output characteristics.

  The primary particle diameter of the positive electrode active material of (a) is preferably 0.1 μm or more, more preferably 0.2 μm or more, and still more preferably 0.00 μm or more, from the viewpoint of safety and stability of the positive electrode active material and cycle characteristics. It is preferably 3 μm or more, and is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 2 μm or less from the viewpoints of composite aggregating property, reactivity, and fast discharge in the aggregating step. From the above viewpoints, 0.1 to 10 μm is preferable, 0.2 to 5 μm is more preferable, and 0.3 to 2 μm is even more preferable.

  The conductive substance (b) is a conductive substance having a primary particle diameter of 10 to 100 nm, and forms composite particles when combined with the positive electrode active material (a).

  As the conductive substance (b), a carbonaceous material is preferable, and examples thereof include artificial or natural graphite powder in addition to carbon black. Among these, carbon black is preferable from the viewpoint of adhesion to the positive electrode active material after forced dispersion, contact property, conductivity, and the like.

  Carbon black is produced by any of the following methods: thermal black method, decomposition method such as acetylene black method, channel black method, gas furnace black method, oil furnace black method, pine smoke method, lamp black method, etc. However, furnace black, acetylene black, and ketjen black (registered trademark) are preferably used from the viewpoint of conductivity, and ketjen black is more preferable. These may be used alone or in combination of two or more.

  About the electroconductive substance of (b), there exists a tendency for the aspect of the composite particle obtained by combining with the positive electrode active material of (a) to differ by the difference in the structure structure. Carbon black exists in a state where particles are fused (called an aggregate, conceptually like a bunch of grapes), and the degree of development of this aggregate is called a structure.

Since carbon black suitable for the first embodiment is preferably deposited in the form of primary particles on the surface of the positive electrode active material, it is preferable that the carbon black has a relatively unstructured structure. Specifically, DBP (dibutyl phthalate) carbon black absorption is less than 200cm ³ / 100g is preferred.

  As the conductive material (b) suitable for the first embodiment, the primary particle size of the conductive material is the primary particle size of the positive electrode active material from the viewpoint of effectively attaching the conductive material to the surface of the positive electrode active material. It is preferably smaller, preferably 1/5 or less of the primary particle diameter of the positive electrode active material, more preferably 1/10 or less, and even more preferably 1/15 or less. In particular, when carbon black is used, the primary particle diameter is preferably 1/5 or less, more preferably 1/10 or less, and even more preferably 1/15 or less of the primary particle diameter of the positive electrode active material.

  The primary particle size of the conductive material, preferably carbon black, is 10 to 100 nm, preferably 15 to 80 nm, more preferably from the viewpoint of ease of forced dispersion and adhesion to the positive electrode active material. 20-50 nm. Carbon black having such a primary particle diameter can be more reliably attached to the surface of the positive electrode active material by being finely divided, and the volume resistivity can be further reduced.

  The composite particles according to the first aspect have a structure in which the conductive material as described above is attached to the positive electrode active material. The coverage of the conductive material on the surface of the positive electrode active material is determined between the conductive material and the positive electrode active material. It can be easily controlled by the content ratio, the particle size ratio, and the like. This coverage is preferably 5% or more, more preferably 10% or more from the viewpoint of reducing the volume resistivity, and preferably 80% or less, preferably 70% or less from the viewpoint of suitable diffusion of lithium ions. More preferably, from the viewpoint of reduction in volume resistivity and suitability for lithium ion diffusion, 5 to 80% is preferable, and 10 to 70% is more preferable.

On the other hand, since the carbon black suitable for the second embodiment preferably has a structure that easily encloses the positive electrode active material, carbon black having a relatively developed structure is preferable. Specifically, DBP absorption amount of carbon black 200~800cm ³ / 100g is preferably used.

  The conductive material (b) suitable for the second embodiment is preferably self-aggregating carbon black, and the primary particle diameter measured with a scanning electron microscope is preferably from the viewpoint of ease of primary dispersion. It is 10 nm or more, more preferably 15 nm or more, and further preferably 20 nm or more. Further, from the viewpoint of ease of reaggregation after dispersion, it is preferably 100 nm or less, more preferably 80 nm or less, and even more preferably 50 nm or less.

  In the present invention, in forming the composite particles in the second aspect, the conductive substance (b) and / or the conductive substance (c) is a conductive substance having self-aggregation property in a solvent. Is preferred. Such a conductive substance having self-aggregating property may be any conductive substance having a property of self-aggregating by forcibly dispersing in a solvent used for dispersion and then allowing to stand. Carbon black having carbon fiber having self-aggregation property, fibrous carbon such as carbon nanotube (CNT), and the like (the conductive material (c) will be described later).

As the carbon black having self-aggregation property, a carbon black having a large structure that can be aggregated by including the positive electrode active material is preferable. The size of the carbon black structure can be determined from the DBP absorption amount. From the viewpoint of improving the penetration of the electrolyte and favoring the diffusion of Li ions, the DBP absorption amount of the carbon black used is preferably 200 cm ³ / 100g or more, more preferably 250 cm ³ / 100g or more, still more preferably 300 cm ³ / 100g or more. Further, from the viewpoint of not lowering the electrode density, DBP absorption amount is preferably from 800 cm ^{3/100 g,} more preferably not more than 700 cm 3/100 ^g, more preferably less 600 cm 3/100 g, Taken together this aspect, 200～800Cm ³ / 100g is preferable, 250-700cm < ³ > / 100g is more preferable, 300-600cm < ³ > / 100g is still more preferable.

  The content of the conductive material (b) is preferably 0.2 parts by weight or more with respect to 100 parts by weight of the positive electrode active material from the viewpoint of suitably forming the composite particles of the first or second aspect. More preferably, it is 0.5 parts by weight or more, and still more preferably 1 part by weight or more. Moreover, from the viewpoint of the balance between the volume resistivity and the total pore volume ratio, it is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, still more preferably 5 parts by weight or less. 2-20 weight part is preferable, 0.5-10 weight part is more preferable, and 1-5 weight part is still more preferable.

  In the present invention, when forming composite particles combining the first aspect and the second aspect, the carbon black suitable for the first aspect and the carbon black suitable for the second aspect or the conductivity of (c) It is preferable to use in combination with the active substance. As a result, composite particles in which the composite particles of the first aspect are wrapped with an aggregate of primary particles of the conductive material are formed. That is, in this aspect, carbon black suitable for the first aspect is deposited on the surface of the positive electrode active material of (a), and this is applied to an aggregate of carbon black primary particles suitable for the second aspect and / or Or the composite particle which the conductive substance of (c) wrapped is formed.

  The conductive material (c) is suitably used for forming the composite particles of the second aspect, and the conductive material is preferably fibrous carbon. As the fibrous carbon, fibrous carbon having a structure in which fibers are intertwined and aggregated in a threadball shape is preferable, and such carbon is dispersed by applying a dispersing agent or mechanical stress in the presence of a positive electrode active material. Then, by stopping the dispersion, self-aggregation is performed while taking in the positive electrode active material when self-aggregating, and the composite particles of the second aspect can be formed.

As the fibrous carbon which is a conductive substance of (c), carbon fiber made from a polymer represented by polyacrylonitrile (PAN), pitch-based carbon fiber made from pitch, carbon nanotube (one piece of graphite) Surface, that is, a shape formed by winding a graphene sheet into a cylindrical shape (Particles of Fine Particle Engineering, Vol. I, P651, Fuji Techno System Co., Ltd.), a vapor-grown carbon fiber that uses hydrocarbon gas as a raw material ( For example, so-called narrowly defined carbon nanotubes (hereinafter referred to simply as carbon nanotubes) obtained by VGCF (registered trademark), arc discharge method, laser evaporation method, chemical vapor deposition method, etc. are preferably used. . From the viewpoint of constructing more conductive paths, fibrous carbon having a small fiber diameter is preferable, and VGCF and carbon nanotubes are preferably used. Among them, carbon nanotubes are preferably used. The carbon nanotube is, for example, an arc discharge method in which a graphite electrode is evaporated by arc discharge under an atmospheric gas such as He, Ar, CH ₄ , or H ₂ , and graphite containing a metal catalyst such as Ni, Co, Y, or Fe. An arc discharge method in which electrodes are evaporated by arc discharge, a YAG laser is applied to graphite mixed with a metal catalyst such as Ni-Co, Pd-Rd, and the laser is sent to an electric furnace heated to about 1200 ° C. with an Ar air stream. It can be obtained by an evaporation method, a HiPCO method in which pentacarbonyl iron (Fe (CO) ₅ ) is used as a catalyst, and carbon monoxide is thermally decomposed at high pressure. As for the aspect ratio of the carbon nanotube, for example, the smaller the concentration ratio of the hydrocarbon (benzene or the like) and the atmospheric gas such as hydrogen gas, the smaller the diameter of the generated carbon nanotube and the larger the aspect ratio. In addition, the shorter the reaction time, the thinner the carbon nanotubes that are produced, and the higher the aspect ratio.

  In the present invention, considering the formation mechanism of the composite particles of the second aspect as described above, the aspect ratio of the fiber diameter (W) to the fiber length (L) of the fibrous carbon, that is, L / W is important. The aspect ratio of the fibrous carbon is preferably 50 or more, more preferably 100 or more, further preferably 200 or more from the viewpoint of conductivity, and preferably 20,000 or less from the viewpoint of the dispersibility of the fibrous carbon. More preferably, it is 5000 or less, More preferably, it is 1000 or less, Comprising the said viewpoint, 50-20,000 are preferable, 100-5000 are more preferable, 200-500 are still more preferable.

  That is, the fibrous carbon having an aspect ratio of 50 to 20000 generally has high self-aggregation property, and has a high ability to self-aggregate and produce aggregated particles by being forcedly dispersed in a solvent and then left standing. Can be suitably used.

  In that case, the fiber length of fibrous carbon becomes like this. Preferably it is 50 nm or more, More preferably, it is 500 nm or more, More preferably, it is 1 micrometer or more. Moreover, from the viewpoint of the smoothness of the surface of the positive electrode produced using the composite positive electrode material of the present invention, it is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 10 μm or less. 50 nm to 50 μm is preferable, 500 nm to 30 μm is more preferable, and 1 to 10 μm is still more preferable.

  The fiber diameter of the fibrous carbon is 1 nm to 1 μm, preferably 1 to 500 nm, more preferably 1 to 300 nm from the viewpoint of making more contact with the surface of the positive electrode active material and establishing a conductive path.

  The content of the conductive material (c) is preferably 0.2 parts by weight or more, more preferably 100 parts by weight or more with respect to 100 parts by weight of the positive electrode active material, from the viewpoint of effectively expressing the self-aggregating force in the aggregation process. 0.5 parts by weight or more, more preferably 1 part by weight or more. Moreover, from the viewpoint of the balance between the volume resistivity and the total pore volume ratio, it is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, still more preferably 5 parts by weight or less. 2-20 weight part is preferable, 0.5-10 weight part is more preferable, and 1-5 weight part is still more preferable.

  When the composite particles are formed using the conductive material (b) and / or the conductive material (c), the total content of the conductive material is from the viewpoint of improving conductivity (reducing volume resistivity), Preferably it is 0.2 weight part or more with respect to 100 weight part of positive electrode active materials, More preferably, it is 0.5 weight part or more, More preferably, it is 1 weight part or more. Further, from the viewpoint of the energy density of the composite particles, it is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and still more preferably 15 parts by weight or less. Preferably, 0.5-30 weight part is more preferable, and 1-15 weight part is still more preferable.

  In the present invention, both the first aspect and the second aspect have an effect of smoothing the flow of electrons to the positive electrode active material. In particular, the second aspect promotes the movement of electrons. Of course, it is preferable from the viewpoint of hardly inhibiting the diffusion of Li ions. Furthermore, the composite particle which combined the 1st aspect and the 2nd aspect by using a self-aggregating electroconductive substance when forming the composite particle of a 1st aspect is more preferable.

  As a method for forming the composite particles as described above, when using a conductive material having low self-aggregation property, a solvent is used from a slurry obtained by dispersing in a solvent until at least the positive electrode active material and the conductive material are forcibly dispersed. The composite particles containing the positive electrode active material and the conductive material can be obtained.

  Further, when using a self-aggregating conductive material, at least a dispersion step in which a self-aggregating conductive material and a positive electrode active material are dispersed in a solvent and forcedly dispersed in the solvent; The composite particles can be formed by a method including an aggregating step of aggregating the active substance together with the positive electrode active material in a solvent to obtain aggregated particles.

  In the present invention, the “forced dispersion state” means that when the slurry is sampled and diluted to a predetermined concentration and the average particle size is measured with a particle size distribution measurement device without delay, the average particle size is the primary particle of the positive electrode active material. The dispersion state is within 130% of the diameter (from the viewpoint of comparison with the primary particle diameter of the positive electrode active material, a specific measurement method will be described later in the measurement method of the primary particle diameter of the positive electrode active material). That is, in this state, the measured average particle size approaches the primary particle size of the positive electrode active material by shifting from the initial aggregated state to the forcedly dispersed state (the dispersion state of the conductive material is also reflected in this measured value). It is possible to grasp the state of forced dispersion from this phenomenon.

  As a solvent used for dispersion, N-methyl-2-pyrrolidone (NMP, boiling point 202 ° C.), dimethylformamide (DMF, boiling point 153 ° C.), dimethylacetamide (boiling point 165 ° C.), methyl ethyl ketone (boiling point 79.5 ° C.), tetrahydrofuran (Boiling point 66 ° C.), acetone (boiling point 56.3 ° C.), ethanol (boiling point 78.3 ° C.), ethyl acetate (boiling point 76.8 ° C.) and the like are preferably used. Among these, when obtaining composite particles in a slurry state, NMP having a high boiling point is preferably used as a solvent, and when obtaining in a dry particle state, methyl ethyl ketone or ethanol having a low boiling point is preferred.

  The boiling point of the solvent is preferably 250 ° C. or lower, more preferably 100 ° C. or lower, and further preferably 80 ° C. or lower, from the viewpoint of ease of drying. In particular, when using a conductive substance with low self-aggregation property or when obtaining composite particles in a dry particle state, the boiling point of the solvent is preferably 100 ° C. or lower.

  The amount of the solvent used is preferably 50 parts by weight or more, more preferably 100 parts by weight or more with respect to 100 parts by weight of the positive electrode active material of (a), from the viewpoint of effectively dispersing the conductive material, the positive electrode active material, and the like. preferable. Further, from the viewpoint of complexity of drying of the solvent, the amount is preferably 1000 parts by weight or less, more preferably 800 parts by weight or less, and taking the above viewpoints together, 50 to 1000 parts by weight is preferable, and 100 to 800 parts by weight is more preferable. .

  Examples of the disperser used for dispersion include an ultrasonic disperser, a stirring disperser, a high-speed rotary shear disperser, a mill disperser, a high-pressure jet disperser, and the like. In this case, an ultrasonic disperser and a high-pressure jet disperser are preferably used.

  A mill type disperser is preferably used as a disperser with a pulverizing action. Note that a conductive material may be prepared in advance by wet pulverization or dry pulverization, and dispersed in a solvent.

  The method using the dispersant is particularly effective for suitably dispersing the conductive material. When a dispersant is used, an anionic, nonionic or cationic surfactant, or a polymer dispersant can be used as the dispersant, but a polymer dispersant is preferably used from the viewpoint of dispersion performance.

  Although various compounds can be used as the polymer dispersant, a polycarboxylic acid polymer dispersant having a plurality of carboxyl groups in the molecule and a polyamine polymer dispersant having a plurality of amino groups in the molecule A polymer dispersant having a plurality of amide groups in the molecule and a polymer dispersant containing a plurality of polycyclic aromatic compounds in the molecule are preferred.

  Examples of the polyamine polymer dispersant include comb polymers in which a polyester is grafted to a polyamine such as polyalkyleneamine, polyallylamine, and N, N-dimethylaminoethyl methacrylate.

  Examples of polycarboxylic acid-based polymer dispersants include copolymers of (meth) acrylic acid and (meth) acrylic acid esters, various amines such as maleic anhydride copolymer and alkylamine, and amidated and esterified products of alcohols, Examples thereof include polycarboxylic acid polyesters such as poly (meth) acrylic acid copolymers and comb polymers grafted with polyalkylene glycol. In the present specification, (meth) acrylic acid refers to acrylic acid or methacrylic acid.

  Polymer dispersants with multiple amide groups in the molecule include polyamides obtained by condensation reactions, polyvinylpyrrolidone, poly N, N-dimethylacrylamide copolymers, and comb polymers in which polyesters or polyalkylene glycols are grafted. Etc.

  Examples of the polymer dispersant containing a polycyclic aromatic compound include copolymers of vinyl monomers having a pyrene or quinacridone skeleton and various monomers. The above dispersants can be used alone or in admixture of two or more dispersants.

  In the case of using a dispersant, the amount of the dispersant added is 0.1 to 20% by weight with respect to 100 parts by weight of the object to be dispersed (positive electrode active material + conductive material in the present invention) from the viewpoint of suitably dispersing. Part is preferable, and 0.5 to 10 parts by weight is more preferable.

  In the step of forming composite particles, the solvent is removed from the slurry obtained by the dispersion as described above to obtain composite particles. The removal of the solvent from the slurry can be performed by heat evaporation, distillation under reduced pressure, spray drying, freeze drying, or the like.

  Alternatively, composite particles can be formed by aggregating a conductive material together with a positive electrode active material in a solvent to obtain aggregated particles. In this agglomeration process, self-aggregating conductive materials are likely to self-aggregate. Therefore, by stopping the disperser, self-aggregation is promoted, and a slurry containing aggregated particles is obtained. In order to further increase the ratio, a method of obtaining a powder of aggregated particles by distilling off the solvent and forcibly aggregating can be used.

  The average particle size of the composite particles is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more, from the viewpoint of appropriately ensuring the pore volume of the composite particles. In addition, from the viewpoint of the surface property of the positive electrode obtained using the present composite particles, preferably 20 μm or less, more preferably 15 μm or less, and further preferably 10 μm or less. From the above viewpoints, 0.1 to 20 μm is preferable. 0.5 to 15 μm is more preferable, and 1 to 10 μm is still more preferable.

  The conductive material (d) is a conductive material having an aspect ratio of 2 to 50, and has a structure interposed between the composite particles. When a carbon fiber having an aspect ratio larger than this range is used instead of the conductive material of (d), the diffusion of lithium ions becomes insufficient, and the carbon fiber becomes difficult to be properly disposed between the composite particles, The positive electrode obtained tends to have insufficient high-speed discharge performance.

  As the conductive material (d), carbon black having a structure structure is preferable. Carbon black having an aspect ratio in such a range can suitably form voids for the diffusion of Li ions due to the development of the structure structure, and can form a conductive path between the composite particles. It is considered possible.

  The following can be used as such carbon black. Carbon black may have an agglomerated structure in which the primary particles are branched in an irregular chain in which a number of primary particles are connected. When such particles are observed with a scanning electron microscope, the aspect ratio of the longest diameter (L) and the shortest diameter (W), that is, L / W becomes important.

  The aspect ratio of the conductive substance (d) is 2 or more, preferably 3 or more, more preferably 3.5 or more from the viewpoint of the conductivity of the composite positive electrode material, and from the viewpoint of making lithium ion diffusion suitable. , 50 or less, preferably 20 or less, more preferably 10 or less. Taking the above viewpoints together, the aspect ratio is 2 to 50, preferably 3 to 20, and more preferably 3.5 to 10.

Carbon black having a high aspect ratio generally has a large DBP absorption because it has an agglomerated structure. Therefore, DBP absorption amount of carbon black having a structure structure is preferably 100 cm ^3/100 g or more, more preferably 120 cm ^3/100 g or more, more preferably 150 cm ^3/100 g or more. Further, from the viewpoint of not lowering the electrode density ^is preferably not more than 400 cm 3/100 ^g, more preferably not more than ^{300cm 3 / 100g, 200cm 3 /} 100g or less are more preferred. When the said viewpoint is put together, 100-400 cm < ³ > / 100g is preferable, 120-300 cm < ³ > / 100g is more preferable, 150-200 cm < ³ > / 100g is still more preferable.

The specific surface area of carbon black is preferably 20 m ³ / g or more, more preferably 30 m ³ / g or more, still more preferably 40 m ³ / g or more, from the viewpoint of securing an appropriate pore capacity of the positive electrode. From the viewpoint of appropriately suppressing the volume and ensuring compactness, 2000 m ³ / g or less is preferable, 500 m ³ / g or less is more preferable, and 100 m ³ / g or less is more preferable. When the said viewpoint is put together, 20-2000 m < ³ > / g is preferable, 30-500 m < ³ > / g is more preferable, 40-100 m < ³ > / g is still more preferable.

  As the carbon black having the above-described structure structure, carbon black having the above physical properties can be used among the carbon blacks used as the conductive material (b). More specifically, the furnace method conductive carbon black that pyrolyzes raw material hydrocarbons by the combustion heat of crude oil and gas to produce carbon black, ketjen black obtained by heavy oil gasification process, and acetylene gas are heated. Examples include acetylene black obtained by decomposition, such as Ketjen Black EC manufactured by Lion, Vulcan XC-72 manufactured by Cabot, Printex L6 manufactured by Degussa, Printex XE2, and the like.

  The particle size of the carbon black having a structure structure is represented by the average particle size (aggregated particle size) of aggregates formed by connecting primary particles, and a laser diffraction / scattering type particle size distribution analyzer LA750 (manufactured by Horiba) is used. It is determined by measuring the particle size distribution used. The average particle size is preferably 0.05 to 10 μm from the viewpoint of the conductivity of the positive electrode and the smoothness of the coating film when the positive electrode material is applied to form a coating film, and is preferably 0.08. -5 μm is more preferable, and 0.1-2 μm is still more preferable.

  The blending amount of the conductive material (d) is preferably 2 parts by weight or more, more preferably 100 parts by weight with respect to 100 parts by weight of the positive electrode active material, from the viewpoint of reducing volume resistivity by forming a conductive path of the positive electrode to be obtained. It is 4 parts by weight or more, more preferably 8 parts by weight or more. Further, from the viewpoint of increasing the energy density of the composite positive electrode material, it is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and still more preferably 15 parts by weight or less. When the said viewpoint is put together, 2-50 weight part is preferable, 4-30 weight part is more preferable, and 8-15 weight part is still more preferable.

  From the viewpoint of reducing the volume resistance of the composite positive electrode material, the total amount of the conductive substances (b) to (d) is preferably 3 parts by weight or more with respect to 100 parts by weight of the positive electrode active material of (a). Preferably it is 5 weight part or more, More preferably, it is 10 weight part or more. Further, from the viewpoint of increasing the energy density of the composite positive electrode material, it is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and still more preferably 15 parts by weight or less. Preferably, 5-30 weight part is more preferable, and 10-15 weight part is still more preferable.

  The volume resistivity of the composite positive electrode material of the present invention is preferably 5 Ω · cm or less, more preferably 3 Ω · cm or less, still more preferably 2 Ω · cm or less, from the viewpoint of improving high-speed discharge characteristics.

  The total pore capacity after distilling off the solvent of the composite positive electrode material of the present invention is preferably 0.8 cc / g or more, more preferably 0.9 cc / g or more, and still more preferably, from the viewpoint of improving fast discharge performance. From the viewpoint of appropriately securing the energy density of the positive electrode, it is preferably 25 cc / g or less, more preferably 10 cc / g or less, and even more preferably 5 cc / g or less. When the said viewpoint is put together, Preferably it is 0.8-25 cc / g, More preferably, it is 0.9-10 cc / g, More preferably, it is 1-5 cc / g. By setting it as such a total pore volume, it is thought that the diffusion of Li ion can be made smooth. On the other hand, the lithium-ion battery positive electrode slurry of the present invention contains the composite positive electrode material of the present invention as described above and a binder. The positive electrode for a lithium ion battery of the present invention contains the composite positive electrode material of the present invention as described above and a binder.

  Although the positive electrode active material (a) and the conductive materials (b) to (d) have been described above, the present invention optionally contains other positive electrode materials as necessary. be able to. These are not particularly limited, and conventionally known ones can be widely applied. These will be described below.

  Other positive electrode materials that can be used in the composite positive electrode material for lithium ion batteries of the present invention include a binder, an electrolyte supporting salt (lithium salt) for increasing ion conductivity, a polymer gel or a solid electrolyte (host polymer, electrolysis). Liquid, etc.). In the case of using a polymer gel electrolyte for the battery electrolyte layer, it is sufficient that a conventionally known binder, a conductive material for enhancing electronic conductivity, and the like are included. Salt etc. may not be included. Even when a solution electrolyte is used for the battery electrolyte layer, the positive electrode material may not contain a host polymer, an electrolytic solution, a lithium salt, or the like as a raw material of the polymer electrolyte.

  As the binder, any conventional binder used for forming a positive electrode can be used, but polyvinylidene fluoride, polyamideimide, polytetrafluoroethylene, polyethylene, polypropylene, polymethyl methacrylate, and the like can be preferably used.

  The polymer gel electrolyte includes a solid polymer electrolyte having ion conductivity and an electrolyte used in a conventionally known non-aqueous electrolyte lithium ion battery, and further has lithium ion conductivity. A structure in which a similar electrolyte solution is held in a non-polymeric skeleton is also included.

  Here, the electrolytic solution (electrolyte supporting salt and plasticizer) contained in the polymer gel electrolyte is not particularly limited, and various conventionally known electrolytic solutions can be appropriately used.

For example, inorganic acid anion salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C 2 _F 5 _{SO 2)} selected from organic acid anion salts such as 2 _N, wherein at least one lithium salt (electrolyte support salt), propylene carbonate, cyclic carbonates such as ethylene carbonate; dimethyl carbonate , Chain carbonates such as methyl ethyl carbonate and diethyl carbonate; ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-dibutoxyethane; γ-butyrolactone, etc. Lactones; Nitto such as acetonitrile Lyls; esters such as methyl propionate; amides such as dimethylformamide; plasticizers such as aprotic solvents (organic solvents) in which at least one or more selected from methyl acetate and methyl formate are mixed ) Can be used. However, it is not necessarily limited to these.

  Examples of the solid polymer electrolyte having ion conductivity include known solid polymer electrolytes such as polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof.

  For example, polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), etc. are used as the polymer having no lithium ion conductivity used in the polymer gel electrolyte. it can. However, it is not necessarily limited to these.

  Note that PAN, PMMA, etc. are in a class that has almost no ionic conductivity, and therefore can be a polymer having the above ionic conductivity, but here, they are used for a polymer gel electrolyte. This is exemplified as a polymer having no lithium ion conductivity.

As an electrolyte support salt to increase the ionic conductivity, for _{example, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anion salts such as, Li ( An organic acid anion salt such as CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, or a mixture thereof can be used. However, it is not necessarily limited to these.

  The ratio (mass ratio) between the host polymer and the electrolytic solution in the polymer gel electrolyte may be determined according to the purpose of use, but is in the range of 2:98 to 90:10.

  In the composite positive electrode material of the present invention, the amount of the binder other than the active material and the conductive material, the polymer electrolyte (host polymer, electrolytic solution, etc.), the lithium salt, and the like are used for the purpose of the battery (emphasis on output, energy, etc.), It should be determined in consideration of ionic conductivity.

  When the slurry for a lithium ion battery positive electrode of the present invention contains a solvent, any conventional solvent used for forming a positive electrode can be used as the solvent, such as those used for forming a composite positive electrode material. .

  The viscosity of the slurry is preferably 1000 cps or more, more preferably 2000 cps or more, from the viewpoint of the thickness of the obtained electrode. Moreover, from a viewpoint of the applicability | paintability to a collector, 15000 cps or less is preferable and 10,000 cps or less is more preferable.

  The solid content concentration of the slurry is preferably 20% by weight or more and more preferably 35% by weight or more from the viewpoint of preferable slurry viscosity. Moreover, from a viewpoint of preferable slurry viscosity, 60 weight% or less is preferable and 45 weight% or less is more preferable.

  Next, the composite positive electrode material according to the present invention can be widely applied to positive electrodes for lithium ion batteries and lithium ion batteries. In the lithium ion battery, expansion and contraction is small, and a sufficient effect can be obtained with a small amount of conductive material that satisfies the above requirements. Further, since the positive electrode for a lithium ion battery is composed of a current collector and a positive electrode active material layer constituting the lithium ion battery described below, these will be described in the following description of the lithium ion battery. . However, in the case of a bipolar lithium ion battery, the lithium ion positive electrode is a bipolar electrode.

  That is, the battery to which the composite positive electrode material of the present invention can be applied is a lithium ion battery that can be expected to have high output and high capacity. Such a battery can achieve a high energy density and a high output density, and can be suitably used as a drive power source for vehicles, and can also be sufficiently applied to a lithium ion battery for portable devices such as a mobile phone. Therefore, in the following description, a lithium ion battery using the composite positive electrode material of the present invention will be described, but it should not be limited to these.

  That is, the lithium ion battery that is the subject of the present invention may be any lithium ion battery that uses the composite positive electrode material of the present invention described above, and the other constituent elements should not be limited at all. For example, when the lithium ion battery is distinguished by usage pattern, it can be applied to any usage pattern of a primary battery and a secondary battery. When the lithium ion battery is distinguished by its form and structure, it can be applied to any conventionally known form and structure such as a stacked (flat) battery and a wound (cylindrical) battery. Also, when viewed in terms of the electrical connection form (electrode structure) in a lithium ion battery, it is applicable to both non-bipolar (internal parallel connection type) batteries and bipolar (internal series connection type) batteries described above. To get.

  In the bipolar battery, a single cell voltage is higher than that of a normal battery, and a battery having excellent capacity and output characteristics can be configured. Since the polymer battery does not cause liquid leakage, it is advantageous in that a non-aqueous battery having no problem of liquid junction and having high reliability and excellent output characteristics can be formed with a simple configuration. In addition, by adopting a laminated (flat) battery structure, long-term reliability can be secured by a sealing technique such as simple thermocompression bonding, which is advantageous in terms of cost and workability.

  Accordingly, in the following description, a non-bipolar non-aqueous electrolyte lithium ion secondary battery and a bipolar non-aqueous electrolyte lithium ion secondary battery using the composite positive electrode material of the present invention will be described with reference to the drawings. However, it should never be limited to these. That is, there are no restrictions on the constituent elements other than the electrode materials described above.

  FIG. 2 shows a schematic cross-sectional view of a non-bipolar flat (stacked) nonaqueous electrolyte lithium ion secondary battery. In the lithium ion secondary battery 31 shown in FIG. 2, a positive electrode current collector is obtained by using a laminate film in which a polymer-metal is combined with a battery exterior material 32 and bonding the entire peripheral portion thereof by heat fusion. A negative electrode active material layer 37 is formed on both surfaces of the positive electrode plate having the positive electrode active material layer 34 formed on both surfaces of the electrode 33, the electrolyte layer 35, and the negative electrode current collector 36 (one side for the lowermost layer and the uppermost layer of the power generation element). In addition, the power generation element 38 in which the negative electrode plates are stacked is housed and sealed. In addition, the positive electrode (terminal) lead 39 and the negative electrode (terminal) lead 40 that are electrically connected to the electrode plates (positive electrode plate and negative electrode plate) are connected to the positive electrode current collector 33 and the negative electrode current collector 36 of each electrode plate. It is attached by sonic welding, resistance welding, or the like, and has a structure that is sandwiched between the heat fusion parts and exposed to the outside of the battery outer packaging material 32.

FIG. 3 is a schematic cross-sectional view schematically showing the entire structure of a bipolar nonaqueous electrolyte lithium ion secondary battery (hereinafter also simply referred to as a bipolar battery).
As shown in FIG. 3, in the bipolar battery 41, a positive electrode active material layer 43 is provided on one side of a current collector 42 composed of one or more sheets, and a negative electrode active material layer 44 is provided on the other side. In addition, the positive electrode active material layer 43 and the negative electrode active material layer 44 of the bipolar electrode 45 adjacent to each other with the electrolyte layer 46 interposed therebetween are opposed to each other.

  That is, in the bipolar battery 41, a plurality of bipolar electrodes 45 having the positive electrode active material layer 43 on one surface of the current collector 42 and the negative electrode active material layer 44 on the other surface are disposed via the electrolyte layer 46. The electrode laminate (bipolar battery main body) 47 has a laminated structure. Further, the uppermost layer and the lowermost layer electrodes 45a and 45b of the electrode laminate 47 in which a plurality of such bipolar electrodes 45 and the like are laminated may not have a bipolar electrode structure, and are necessary for the current collector 42 (or terminal plate). A structure in which the positive electrode active material layer 43 or the negative electrode active material layer 44 only on one side may be arranged. In the bipolar battery 41, positive and negative electrode leads 48 and 49 are joined to current collectors 42 at both upper and lower ends, respectively.

  Note that the number of stacked bipolar electrodes 45 (including the electrodes 45a and 45b) is adjusted according to a desired voltage. Further, in the bipolar battery 41, the number of lamination of the bipolar electrode 45 may be reduced if a sufficient output can be secured even if the battery is made as thin as possible. Further, in the bipolar battery 41 of the present invention, in order to prevent external impact and environmental degradation during use, the electrode laminate 47 portion is sealed under reduced pressure in a battery exterior material (exterior package) 50, and electrode leads 48, It is preferable that 49 be taken out of the battery exterior material 50.

  The basic configuration of the bipolar battery 41 can be said to be a configuration in which a plurality of stacked single battery layers (single cells) are connected in series. This bipolar type non-aqueous electrolyte lithium ion secondary battery is basically the same as the non-bipolar type non-aqueous electrolyte lithium ion secondary battery described above except that its electrode structure is different. The elements are summarized below.

[Current collector]
The current collector that can be used in the present invention is not particularly limited, and conventionally known current collectors can be used. For example, aluminum foil, stainless steel (SUS) foil, nickel-aluminum clad material, copper-aluminum clad material, SUS-aluminum clad material, or a plated material of a combination of these metals can be preferably used. Further, a current collector in which a metal surface is coated with aluminum may be used. Moreover, you may use the electrical power collector which bonded 2 or more metal foil depending on the case. When the composite current collector is used, as a material for the positive electrode current collector, for example, a conductive metal such as aluminum, an aluminum alloy, SUS, or titanium can be used, but aluminum is preferable.

  On the other hand, as the material of the negative electrode current collector, for example, conductive metals such as copper, nickel, silver, and SUS can be used, and SUS and nickel are preferable. Further, in the composite current collector, the positive electrode current collector and the negative electrode current collector may be electrically connected to each other directly or via a conductive intermediate layer made of a third material. In addition to the flat plate (foil), the positive electrode current collector and the negative electrode current collector are constituted by a lath plate, that is, a plate in which a mesh space is formed by expanding a plate with a cut. Can also be used.

  Although the thickness of a collector is not specifically limited, Usually, it is about 1-100 micrometers.

[Positive electrode active material layer]
Here, as a constituent material of the positive electrode active material layer, the composite positive electrode material of the present invention is used, and since it has already been described, description thereof is omitted here.

  The thickness of the positive electrode active material layer is not particularly limited, and should be determined in consideration of the purpose of use of the battery (output importance, energy importance, etc.) and ion conductivity. The thickness of a general positive electrode active material layer is about 1 to 500 μm, and if it is within this range, it can be sufficiently used in the present invention.

[Negative electrode active material layer]
The negative electrode active material layer includes a negative electrode material active material. In addition to this, conductive aids to enhance electronic conductivity, binders, electrolyte supporting salts (lithium salts) to enhance ionic conductivity, polymer gels or solid electrolytes (host polymers, electrolytes, etc.), etc. Can be. Except for the type of the negative electrode active material, the content is basically the same as that already described as the “composite positive electrode material for a lithium ion battery” of the present invention, and the description is omitted here.

  As a negative electrode active material, the negative electrode active material used also in a conventionally well-known solution-type lithium ion battery can be used. Specifically, a negative electrode mainly composed of at least one selected from carbon materials such as natural graphite, artificial graphite, amorphous carbon, coke and mesophase pitch carbon fiber, graphite, and hard carbon which is amorphous carbon. Although it is desirable to use an active material, it is not particularly limited. In addition, a metal oxide (particularly a transition metal oxide, specifically titanium oxide), a composite oxide of a metal (particularly a transition metal, specifically titanium) and lithium, or the like can also be used.

  Furthermore, the electrolyte contained in the negative electrode active material layer may contain a film forming material. Thereby, the capacity | capacitance fall accompanying the charging / discharging cycle of a battery can be suppressed. The film forming material is not particularly limited, and for example, a conventionally known material such as a film forming material described in JP-A-2000-123880 can be used.

  The thickness of the negative electrode active material layer is not particularly limited, and should be determined in consideration of the intended use of the battery (output importance, energy importance, etc.) and ion conductivity. The thickness of a general negative electrode active material layer is about 1 to 500 μm, and if it is within this range, it can be sufficiently used in the present invention.

[Electrolyte layer]
The present invention can be applied to any of (a) a separator impregnated with an electrolytic solution, (b) a polymer gel electrolyte, and (c) a polymer solid electrolyte depending on the purpose of use.

(A) Separator soaked with electrolyte As the electrolyte that can be soaked in the separator, the same electrolyte as that already contained in the polymer gel electrolyte (electrolyte salt and plasticizer) can be used. Therefore, although description here is omitted, if a suitable example of the electrolytic solution is shown, as the electrolyte, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ Using at least one of N and Li (C ₂ F ₅ SO ₂ ) ₂ N, the solvent is ethylene carbonate (EC), propylene carbonate, diethyl carbonate (DEC), dimethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxy. Ethane, 1,2-diethoxyethane, tetrahydrofuran, 1,3-dioxo The concentration of the electrolyte is adjusted to 0.5 to 2 mol / liter by dissolving at least one kind of ethers consisting of styrene and γ-butyllactone and dissolving the electrolyte in the solvent. The present invention should not be limited to these.

  The separator is not particularly limited, and a conventionally known separator can be used. For example, a porous sheet made of a polymer that absorbs and holds the electrolytic solution (for example, a polyolefin microporous material). Separator, etc.), a nonwoven fabric separator, etc. can be used. The polyolefin microporous separator having the property of being chemically stable to an organic solvent has an excellent effect that the reactivity with the electrolyte (electrolytic solution) can be kept low.

  Examples of the material of the porous sheet such as the polyolefin-based microporous separator include a laminate having a three-layer structure of polyethylene (PE), polypropylene (PP), and PP / PE / PP.

  As the material of the nonwoven fabric separator, for example, conventionally known materials such as cotton, rayon, acetate, nylon, polyester, polypropylene, polyethylene such as polyethylene, polyimide, and aramid can be used. Depending on strength, etc., they are used alone or in combination.

  Further, the bulk density of the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte. That is, if the bulk density of the nonwoven fabric is too large, the proportion of the non-electrolyte material in the electrolyte layer becomes too large, which may impair the ionic conductivity in the electrolyte layer.

  The thickness of the separator (including the non-woven separator) cannot be unambiguously defined because it varies depending on the usage, but it can be used for motor-driven secondary batteries such as electric vehicles (EV) and hybrid electric vehicles (HEV). In use, it is desirable to be 5 to 200 μm. When the thickness of the separator is within such a range, it is possible to suppress increase in retention and resistance. In addition, there is an effect of securing mechanical strength in the thickness direction and ensuring high output performance because it is desirable to prevent a short circuit caused by fine particles entering the separator and to narrow the space between the electrodes for high output. . In addition, when a plurality of batteries are connected, the electrode area increases, so that it is desirable to use a thick separator in the above range in order to increase the reliability of the battery.

  It is desirable that the fine pore diameter of the separator (polyolefin-based microporous separator or the like) is 1 μm or less (usually a pore diameter of about several tens of nm). Due to the fact that the average diameter of the micropores in the separator is within the above range, the “shutdown phenomenon” that the separator melts due to heat and the micropores close quickly occurs, resulting in higher reliability during abnormalities, resulting in heat resistance. Has the effect of improving. In other words, when the battery temperature rises due to overcharging (in an abnormal state), the “shutdown phenomenon” that the separator melts and closes the micropores occurs quickly, so that the positive electrode (+) of the battery (electrode) Li ions cannot pass through to the negative electrode (−) side, and no further charge is possible. As a result, overcharging cannot be performed and overcharging is eliminated. As a result, the heat resistance (safety) of the battery is improved, and it is possible to prevent gas from being released and the heat fusion part (seal part) of the battery exterior material from being opened. Here, the average diameter of the micropores of the separator is calculated as an average diameter obtained by observing the separator with a scanning electron microscope or the like and statistically processing the photograph with an image analyzer or the like.

  The porosity of the separator (such as a polyolefin microporous separator) is preferably 20 to 65%. The separator's porosity is within the above range, preventing output from being reduced due to the resistance of the electrolyte (electrolyte), and preventing the short circuit caused by fine particles penetrating the separator's pores (micropores). It has the effect of securing both sexes. Here, the porosity of the separator is a value obtained as a volume ratio from the density of the raw material resin and the density of the separator of the final product.

  Moreover, from the viewpoint of ensuring good electrolyte retention and separator strength, the nonwoven fabric separator preferably has a porosity of 50 to 90%.

  The amount of the electrolytic solution impregnated in the separator may be impregnated to the range of the liquid retention capacity of the separator, but may be impregnated beyond the liquid retention capacity range. This can prevent impregnation of the electrolyte from the electrolyte layer by injecting a resin into the electrolyte seal portion, and therefore can be impregnated as long as the electrolyte layer can be retained. The electrolyte can be impregnated in the separator by a conventionally known method, for example, the electrolyte can be completely sealed after being injected by a vacuum injection method or the like.

(B) Polymer gel electrolyte and (c) Polymer solid electrolyte As the polymer gel electrolyte and polymer solid electrolyte, the polymer described in the section “Composite cathode material for non-aqueous electrolyte lithium ion battery” of the present invention described above is used. Since the same thing as a gel electrolyte and a polymer solid electrolyte can be used, description here is abbreviate | omitted.

  The electrolyte layers (a) to (c) may be used in one battery.

  In addition, the polymer electrolyte may be included in the polymer gel electrolyte layer, the positive electrode active material layer, and the negative electrode active material layer, but the same polymer electrolyte may be used, or different polymer electrolytes may be used depending on the layer. Good.

  The thickness of the electrolyte layer constituting the battery is not particularly limited. However, in order to obtain a compact battery, it is preferable to make it as thin as possible within a range in which the function as an electrolyte can be ensured, and the thickness of the electrolyte layer is preferably 5 to 200 μm.

[Insulation layer]
The insulating layer is mainly used in the case of a bipolar battery. This insulating layer is formed around each electrode for the purpose of preventing adjacent collectors in the battery from contacting each other and short-circuiting due to slight unevenness at the end of the laminated electrode. It is. In this invention, you may provide an insulating layer around an electrode as needed. When this is used as a vehicle driving or auxiliary power source, it is necessary to completely prevent a short circuit (liquid drop) due to the electrolytic solution. Furthermore, vibrations and impacts on the battery are loaded for a long time. Therefore, from the viewpoint of prolonging battery life, it is desirable to install an insulating layer in order to ensure longer-term reliability and safety, and to provide a high-quality, large-capacity power supply. .

  As the insulating layer, any insulating layer may be used as long as it has insulating properties, sealing performance against falling off of the solid electrolyte, sealing performance against moisture permeation from the outside (sealing performance), heat resistance under battery operating temperature, etc. Epoxy resin, rubber, polyethylene, polypropylene, polyimide and the like can be used, but epoxy resin is preferable from the viewpoint of corrosion resistance, chemical resistance, ease of production (film forming property), economy and the like.

[Positive electrode and negative electrode terminal plate]
The positive electrode and the negative electrode terminal plate may be used as necessary. For example, in the case of a bipolar lithium ion battery, depending on the laminated (or wound) structure, the electrode terminal may be directly taken out from the outermost current collector. In this case, the positive electrode and the negative electrode terminal plate are not used. It is also good (see FIG. 3).

  When using positive and negative terminal plates, in addition to having a function as a terminal, it is better to be as thin as possible from the viewpoint of thinning, but the laminated electrode, electrolyte and current collector all have mechanical strength. Since it is weak, it is desirable to have strength sufficient to sandwich and support them from both sides. Furthermore, it can be said that the thickness of the positive electrode and the negative electrode terminal plate is usually preferably about 0.1 to 2 mm from the viewpoint of suppressing the internal resistance at the terminal portion.

  As materials for the positive electrode and the negative electrode terminal plate, materials used in a conventionally known lithium ion battery can be used. For example, aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof can be used. Aluminum is preferably used from the viewpoints of corrosion resistance, ease of production, economy, and the like.

  The material of the positive electrode terminal plate and the negative electrode terminal plate may be the same material or different materials. Furthermore, the positive electrode and the negative electrode terminal plate may be a laminate of different materials.

[Positive electrode and negative electrode lead]
Regarding the positive electrode and the negative electrode lead, not only the bipolar type but also the same type of lead used in a conventionally known lithium ion battery that is not bipolar type can be used. In addition, the part taken out from the battery exterior material (battery case) does not affect the product (for example, automobile parts, especially electronic devices, etc.) by contacting with peripheral devices or wiring and leaking electricity. It is preferable to coat with a heat-resistant insulating heat-shrinkable tube or the like.

[Battery exterior material (battery case)]
Lithium-ion batteries, not limited to bipolar type, contain the entire battery stack or battery winding body, which is the battery body, in a battery case or battery case in order to prevent external impact and environmental degradation during use. It is desirable to do. From the viewpoint of weight reduction, a polymer-metal composite laminate film in which both surfaces of metals (including alloys) such as aluminum, stainless steel, nickel, and copper are covered with an insulator such as a polypropylene film (preferably a heat-resistant insulator). For example, it is preferable that the battery stack is housed and sealed by joining a part or all of the peripheral part thereof by heat fusion using a conventionally known battery exterior material.

  In this case, the positive electrode and the negative electrode lead may be structured to be sandwiched between the heat-sealed portions and exposed to the outside of the battery exterior material. In addition, it is preferable to use a polymer-metal composite laminate film having excellent thermal conductivity because heat can be efficiently transmitted from a heat source of an automobile and the inside of the battery can be quickly heated to the battery operating temperature. The polymer-metal composite laminate film is not particularly limited, and a conventionally known film in which a metal film is disposed between polymer films and the whole is laminated and integrated can be used. As specific examples, for example, an outer protective layer made of a polymer film (laminate outermost layer), a metal film layer, a heat-sealing layer made of a polymer film (laminate innermost layer), and the whole is laminated and integrated. The thing which becomes. Specifically, in the polymer-metal composite laminate film used for the exterior material, a heat-resistant insulating resin film is first formed as a polymer film on both surfaces of the metal film, and heat fusion is performed on at least one heat-resistant insulating resin film. An insulating insulating film is laminated. Such a laminate film is heat-sealed by an appropriate method, whereby the heat-welding insulating film portion is fused and joined to form a heat-sealing portion.

  An example of the metal film is an aluminum film. Moreover, as said insulating resin film, a polyethylene tetraphthalate film (heat-resistant insulating film), a nylon film (heat-resistant insulating film), a polyethylene film (heat-bonding insulating film), a polypropylene film (heat-bonding insulating film) ) Etc. can be illustrated. However, the exterior material of the present invention should not be limited to these. In such a laminate film, it is possible to easily and surely join one to one (bag-like) laminate films by heat fusion using a heat fusion insulating film by ultrasonic welding or the like. In order to maximize the long-term reliability of the battery, metal films that are constituent elements of the laminate sheet may be directly joined. Ultrasonic welding can be used to join the metal films by removing or destroying the heat-fusible resin between the metal films.

  The use of the battery of the present invention is not particularly limited, but for example, a notebook personal computer, an electronic book player, a DVD in addition to the use of a drive power source and an auxiliary power source for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, a hybrid fuel cell vehicle, It can be used for electronic devices such as players, portable audio players, video movies, portable TVs, and mobile phones, as well as consumer devices such as cordless vacuum cleaners and cordless power tools. Among these, it is suitably used as a battery for automobiles that require particularly high output.

  Examples and the like specifically showing the present invention will be described below. In addition, the evaluation item in an Example etc. measured as follows.

(1) DBP absorption amount DBP absorption amount was measured based on JISK6217-4.

(2) Average particle size of conductive material and primary particle size of positive electrode active material Using laser diffraction / scattering particle size distribution analyzer LA750 (manufactured by HORIBA, Ltd.), ethanol as a dispersion medium, particle size after 1 minute of ultrasonic irradiation The distribution was measured at a relative refractive index of 1.5 for the conductive material, and the volume median particle size (D50) measured at a relative refractive index of 1.7 for the positive electrode active material was the average particle size of the conductive material. And the primary particle diameter of the positive electrode active material.

(3) Primary particle diameter of carbon black 50 primary particles were extracted from an SEM image taken with a field emission scanning electron microscope (Hitachi S-4000), and the average value obtained by measuring the diameter was defined as the primary particle diameter. .

(4) Fiber diameter and fiber length of fibrous carbon 30 fibers were extracted from an SEM image taken with a field emission scanning electron microscope (S-4000 manufactured by Hitachi), and the average value of the measured fiber diameter was determined as the fiber. The diameter. Moreover, the length of the fiber was measured and averaged to obtain the fiber length.

(5) Aspect ratio of fibrous carbon This was determined by dividing the fiber length of fibrous carbon by the fiber diameter.

(6) Aspect ratio of carbon black 30 carbon black secondary aggregates having a shape in which a number of primary particles are connected from a SEM image taken with a field emission scanning electron microscope (Hitachi S-4000) are extracted. The ratio of the longest diameter (L) to the shortest diameter (W), that is, the average value of L / W was determined as the aspect ratio.

(7) Volume resistivity Based on JIS K 1469, the amount of the powder sample was changed to 0.3 g, the pressure at the time of powder compression was changed to 100 kg / cm ^2, and the electric resistance value of the compressed powder sample compressed into a cylindrical shape was The volume resistivity (electrical resistivity) was calculated from the measured resistance value according to the following formula 1.

Specifically, 0.3 g of a powder sample is filled in a cylindrical container composed of an insulating cylinder (made of Bakelite, outer diameter 28 mm, inner diameter 8 mm) and (−) electrode, and the insulating cylindrical container packed with the sample (+ ) The electrode was inserted and the powder sample was sandwiched, and placed on the press machine base. A force of 100 kg / cm ² was applied to the sample in the cylindrical container by a press machine and compressed. The (+) electrode and the (−) electrode were connected to the input cable for measurement of a digital multimeter, and the electrical resistance value was measured after 3 minutes from the start of compression.

ρ = S / h × R (Formula 1)
Here, ρ is the electrical resistivity (Ω · cm), S is the cross-sectional area (cm ² ) of the sample, h is the filling height (cm) of the sample, and R is the electrical resistance value (Ω).

  The (−) electrode used was made of brass, the electrode surface was 7.8 ± 1 mmφ, and was a pedestal-top electrode with a projection of 5 mm in height, and the (+) electrode was made of brass and the electrode surface Was a rod-like electrode having a length of 7.8 ± 1 mmφ and a length of 60 mm.

(8) Production of Battery 3 parts by weight of polyvinylidene fluoride powder (# 1300, manufactured by Kureha Chemical Co., Ltd.) and 45 parts by weight of NMP were uniformly mixed with 27 parts by weight of the powder sample to prepare a coating paste. The paste was uniformly coated on an aluminum foil (thickness 20 μm) used as a current collector using a coater, and dried at 140 ° C. over 10 minutes. After drying, it was molded into a uniform film thickness with a press machine, and then cut into a predetermined size (20 mm × 15 mm) to obtain a test positive electrode. At this time, the thickness of the electrode active material layer was 25 μm.

A test cell was prepared using the test positive electrode. A metal lithium foil was cut into a predetermined size for the negative electrode, and Celgard # 2400 (manufactured by Celgard) was used as the separator. As the electrolyte, 1 mol / l LiPF ₆ / ethylene carbonate (EC): diethyl carbonate (DEC) (EC: DEC = 1: 1 vol%) was used. The test cell was assembled in a glove box under an argon atmosphere. After the test cell was assembled, it was allowed to stand at 25 ° C. for 24 hours, and then high-speed discharge characteristics were evaluated.

(9) Fast discharge characteristics evaluation After performing constant current charge / discharge on the test cell at 0.2 C, (1) discharge capacity (A) with constant current discharge at 1 C, after constant current charge at 0.5 C Further, (2) the ratio of the discharge capacity (B) discharged at a constant current of 0.5 C and then discharged at a constant current of 60 C was defined as a high-speed discharge characteristic.
High-speed discharge characteristics (%) = B / A × 100

(10) Total pore volume Using a mercury intrusion pore distribution measuring device (pore sizer 9320, manufactured by Shimadzu Corporation), the pore volume in the range of 0.008 μm to 200 μm was measured, and the obtained value was assigned to the total pores. Volume.

(11) Self-aggregation test 2 g of conductive material was added to 500 g of ethanol, and ultrasonic irradiation was carried out for 1 minute at a frequency of 19 kHz and an output of 300 W using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, MODELUS-300T). Then, the ultrasonic irradiation is stopped. Immediately after stopping, about 1 cc was sampled, and without delay, the laser diffraction / scattering particle size distribution analyzer LA750 (manufactured by Horiba) used ethanol as the dispersion medium, and the relative refractive index was 1.5 and the sample solution was not irradiated with ultrasonic waves. The average particle size (A) is measured. Next, after 3 minutes have passed since the ultrasonic irradiation was stopped, the conductive material dispersion was sampled, and the average particle size (B) was measured with the LA750 under the same measurement conditions as the average particle size (A). A substance having a value obtained by dividing the average particle diameter (B) by the average particle diameter (A) was 2 or more was defined as a conductive substance having self-aggregation property.

  The evaluation results at that time are shown in Table 1.

(12) Surface coverage of composite particles SEM-EDS analysis was performed with a field emission scanning electron microscope (S-4000 manufactured by Hitachi) to determine the surface coverage of carbon.

Example 1
Ethanol 100 parts by weight, average particle diameter 2 [mu] m (primary particle size 25 nm) in DBP absorption 155cm ^3/100 g carbon black (manufactured by Tokai Carbon Co., ♯5500) was added 0.4 part by weight, an ultrasonic dispersing machine Was used for dispersion with ultrasonic waves. The dispersion state was a forced dispersion state. To this dispersion, 20 parts by weight of lithium manganate having a primary particle diameter of 0.8 μm was added, and dispersion by ultrasonic waves was further performed. The obtained slurry was evaporated to dryness and solidified to obtain a powder (composite particle I, surface coverage 24%) having fine carbon black adhered to the surface of lithium manganate. Then, the average particle diameter of 1μm to 100 parts by weight of ethanol, the carbon black having an aspect ratio 3.8 (manufactured by Denki Kagaku Kogyo Kabushiki Kaisha, HS-100, DBP absorption amount 140cm ³ /100g)2.1 parts by weight of a T. K. Stir with homodispers. Next, 20.4 parts by weight of composite particle I was added and T.P. K. Mixing with a homodisper, the resulting slurry was evaporated to dryness and solidified to obtain a composite positive electrode material 1. The physical properties of the obtained composite positive electrode material 1 are shown in Table 2.

Example 2
The average particle diameter of 10μm to Ettal 100 parts by weight (primary particle diameter 34 nm), Ketjen black DBP absorption 495cm ³ / 100g was added 0.4 part by weight, was ultrasonically dispersed using an ultrasonic type disperser. Thereto, 20.4 parts by weight of the composite particles I prepared in Example 1 were added and ultrasonically dispersed. The resulting slurry was evaporated to dryness and solidified to obtain composite particles II. Then, the average particle diameter of 1μm to 100 parts by weight of ethanol, the carbon black having an aspect ratio 3.8 (manufactured by Denki Kagaku Kogyo Kabushiki Kaisha, HS-100, DBP absorption amount 140cm ³ /100g)1.9 parts by weight of a T. K. Stir with homodispers. Next, 20.8 parts by weight of the composite particle II was added. K. Mixing with a homodisper, the resulting slurry was evaporated to dryness and solidified to obtain a composite cathode material 2. Table 2 shows the physical properties of the composite cathode material 2 obtained. Moreover, the scanning electron microscope (SEM) photograph of the obtained composite positive electrode material is shown in FIG.

Example 3
The average particle diameter of 10μm to NMP100 parts by weight (primary particle diameter 34 nm), Ketjen black DBP absorption 495cm ³ / 100g was added 0.4 part by weight, was ultrasonically dispersed using an ultrasonic type disperser. Then an average particle diameter of 2 [mu] m (primary particle size 25 nm), DBP absorption 155cm ^3/100 g carbon black (Tokai Carbon Co., ♯5500) of the ultrasonic dispersion was added 0.4 parts by weight. While irradiating this carbon dispersion with ultrasonic waves, 20 parts by weight of lithium manganate having a primary particle diameter of 0.8 μm was added, and further dispersed by ultrasonic waves to force-dispersed. Thereafter, ultrasonic irradiation was stopped, and ketjen black was self-aggregated in NMP to obtain a slurry containing composite particles III. The average particle diameter of 1μm to this slurry, the carbon black of aspect ratio 3.8 (manufactured by Denki Kagaku Kogyo Kabushiki Kaisha, HS-100, DBP absorption amount 140cm ³ /100g)1.9 parts by weight of a T. K. The mixture was stirred with a homodisper to obtain a slurry containing the composite positive electrode material 3. Although this slurry can be used for forming a positive electrode by adding necessary components in a liquid state, the solvent was distilled off for physical property evaluation to obtain a composite positive electrode material 3. Table 2 shows the physical properties of the composite cathode material 3 obtained.

Example 4
0.4 parts by weight of carbon nanotubes having a fiber diameter of 20 nm, a fiber length of 10 μm, and an aspect ratio of 500 were added to 100 parts by weight of ethanol, and ultrasonically dispersed using an ultrasonic disperser. Thereto, 20.4 parts by weight of the composite particles I prepared in Example 1 were added and ultrasonically dispersed. The obtained slurry was evaporated and dried and solidified to obtain composite particles IV. Next, an average particle diameter of 1μm to 100 parts by weight of ethanol, the carbon black having an aspect ratio 3.8 (manufactured by Denki Kagaku Kogyo Kabushiki Kaisha, HS-100, DBP absorption amount 140cm ³ /100g)1.9 parts by weight of a T. K. Stir with homodispers. Next, 20.8 parts by weight of the composite particle IV was added and T.P. K. Mixing with a homodisper, the resulting slurry was evaporated to dryness and solidified to obtain a composite positive electrode material 4. Table 2 shows the physical properties of the composite cathode material 4 obtained.

Example 5
0.4 parts by weight of VGCF having a fiber diameter of 120 nm, a fiber length of 10 μm, and an aspect ratio of 83 was added to 100 parts by weight of NMP, and ultrasonic dispersion was performed using an ultrasonic disperser. Then an average particle diameter of 2 [mu] m (primary particle size 25 nm), DBP absorption 155cm ^3/100 g carbon black (Tokai Carbon Co., ♯5500) of the ultrasonic dispersion was added 0.4 parts by weight. While irradiating this carbon dispersion with ultrasonic waves, 20 parts by weight of lithium manganate having a primary particle diameter of 0.8 μm was added, and further dispersed by ultrasonic waves to force-dispersed. Thereafter, the ultrasonic irradiation was stopped, VGCF was self-aggregated in NMP, and a slurry containing composite particles V was obtained. The average particle diameter of 1μm to this slurry, the carbon black of aspect ratio 3.8 (manufactured by Denki Kagaku Kogyo Kabushiki Kaisha, HS-100, DBP absorption amount 140cm ³ /100g)1.9 parts by weight of a T. K. The mixture was stirred with a homodisper to obtain a slurry containing the composite positive electrode material 5. Although this slurry can be used in the form of a positive electrode by adding necessary components in a liquid state, the composite positive electrode material 5 was obtained by distilling off the solvent for physical property evaluation. Table 2 shows the physical properties of the composite cathode material 5 obtained.

Example 6
A composite positive electrode material 6 was obtained in the same manner as in Example 2 except that lithium manganate having a primary particle size of 0.5 μm was used. The physical properties of the obtained composite positive electrode material 6 are shown in Table 2.

Example 7
A composite positive electrode material 7 was obtained in the same manner as in Example 1 except that lithium manganate having a primary particle diameter of 1.2 μm was used. Table 2 shows the physical properties of the obtained composite positive electrode material 7.

Example 8
A composite positive electrode material 8 was obtained in the same manner as in Example 2, except that lithium manganate having a primary particle size of 1.2 μm was used. Table 2 shows the physical properties of the obtained composite positive electrode material 8.

Example 9
A composite positive electrode material 9 was obtained in the same manner as in Example 1 except that lithium manganate having a primary particle size of 10 μm was used. Table 2 shows the physical properties of the composite cathode material 9 obtained.

Example 10
A composite positive electrode material 10 was obtained in the same manner as in Example 2, except that lithium manganate having a primary particle size of 10 μm was used. The physical properties of the obtained composite positive electrode material 10 are shown in Table 2.

Example 11
A composite positive electrode material 11 was obtained in the same manner as in Example 1, except that lithium manganate having a primary particle diameter of 1.2 μm and # 3800 (primary particle diameter of 70 nm) manufactured by Tokai Carbon Co., Ltd. were used as carbon black. . The physical properties of the obtained composite positive electrode material 11 are shown in Table 2.

Comparative Example 1
To the primary particle diameter 0.8μm lithium 100 parts by weight of manganese oxide, the average particle diameter of 1 [mu] m (primary particle diameter 25 nm), DBP absorption 140cm ^3/100 g of carbon black (manufactured by Denki Kagaku Kogyo Kabushiki Kaisha, HS-100) of 10 .5 parts by weight were dry-mixed to obtain a comparative positive electrode material 1. Table 2 shows the physical properties of the comparative positive electrode material 1 obtained.

  As the results of Table 2 show, the composite positive electrode materials of Examples 1 to 11 of the present invention have lower volume resistivity and higher pores than Comparative Example 1 in which a conductive material and a positive electrode active material are dry-mixed. It has a capacity and has excellent fast discharge characteristics.

3 is a scanning electron microscope (SEM) photograph of the composite positive electrode material obtained in Example 2. FIG. The cross-sectional schematic of the flat type (stacked type) non-aqueous electrolyte lithium ion secondary battery which is not a bipolar type is shown. 1 is a schematic cross-sectional view schematically showing the overall structure of a bipolar non-aqueous electrolyte lithium ion secondary battery.

Explanation of symbols

31 Non-aqueous electrolyte lithium ion secondary battery that is not bipolar type 32 Battery exterior material 33 Positive electrode current collector 34 Positive electrode active material layer 35 Electrolyte layer 36 Negative electrode current collector 37 Negative electrode active material layer 38 Power generation element 39 Positive electrode (terminal) lead 40 Negative electrode (Terminal) Lead 41 Bipolar non-aqueous electrolyte lithium ion secondary battery (bipolar battery)
42 Current Collector 43 Positive Electrode Active Material Layer 44 Negative Electrode Active Material Layer 45 Bipolar Electrode 45a Uppermost Electrode of Electrode Stack 45b Lowermost Electrode of Electrode Stack 46 Electrolyte Layer 47 Electrode Stack (Bipolar Battery Body)
48 Positive electrode lead 49 Negative electrode lead 50 Battery exterior material (exterior package)

Claims (6)

(A) a positive electrode active material, (b) a conductive material having a primary particle diameter of 10 to 100 nm, and / or (c) a fibrous conductive material having a fiber diameter of 1 nm to 1 μm, and (d) an aspect ratio. Is a composite positive electrode material for a lithium ion battery containing a conductive material of which 2 to 50,
In a solvent, the positive electrode active material (a), the conductive material (b), and / or the conductive material (c) were dispersed to a state where they were forcibly dispersed and then obtained by agglomeration ( obtained by mixing a positive electrode active material of a), a conductive material of (b) and / or a conductive material of (c), and a conductive material of (d),
Composite particles formed by adhering the conductive material (b) and / or the conductive material (c) to the surface of the positive electrode active material (a) or plural (a) are formed between the composite particles. (D) The composite positive electrode material for lithium ion batteries which has the structure where the electroconductive substance interposes. 2. The composite positive electrode for a lithium ion battery according to claim 1, wherein composite particles are formed by adhering the conductive material of (b) to the surface of the positive electrode active material of (a) with a coverage of 5 to 80%. material. The composite positive electrode material for a lithium ion battery according to claim 1 or 2 , wherein the conductive substance (b) and / or the conductive substance (c) is a conductive substance having self-aggregation in a solvent. The slurry for lithium ion battery positive electrodes containing the composite positive electrode material for lithium ion batteries in any one of Claims 1-3 , and a binder. A positive electrode for a lithium ion battery comprising the composite positive electrode material for a lithium ion battery according to any one of claims 1 to 3 and a binder. A lithium ion battery comprising a composite positive electrode material for a lithium ion battery according to any one of claims 1 to 3 and a positive electrode comprising a binder.

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