JP7170563B2 - Positive electrode for coin-shaped non-aqueous electrolyte secondary battery, coin-shaped non-aqueous electrolyte secondary battery using the same, and method for manufacturing positive electrode for coin-shaped non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a positive electrode for a coin-shaped non-aqueous electrolyte secondary battery, a coin-shaped non-aqueous electrolyte secondary battery using the same, and a method for manufacturing a positive electrode for a coin-shaped non-aqueous electrolyte secondary battery.

In a coin-type non-aqueous electrolyte secondary battery in which a pellet-shaped electrode is housed in a battery can, a structure using a fluororesin such as polytetrafluoroethylene (PTFE) as a binding agent for the electrode is known (for example, See Patent Document 1).
Patent Document 1 describes a non-aqueous electrolyte battery having a positive electrode and a negative electrode, an electrolytic solution made of an organic solvent in which a supporting salt is dissolved, a separator, a sealing gasket, and a positive electrode can and a negative electrode can. In this non-aqueous electrolyte battery, the positive electrode is composed of a pressure-molded body obtained by pressure-molding a positive electrode mixture containing a positive electrode active material, a conductive agent, and a binder.

The PTFE is known to be thermally, chemically, and electrically stable, and a binder made of PTFE is used in the form of powder, and other powders such as active materials and conductive aids are used. By kneading with the material, the PTFE particles become fine fibrous, and each powder material can be bound with a large binding force (see Patent Document 2).

Patent Document 2 discloses a binder consisting of an aqueous dispersion containing PTFE fine particles as a kneaded material for electrodes. Patent Literature 2 describes that adding a nonionic surfactant to an aqueous dispersion and kneading the mixture turns the PTFE fine particles into fibers, thereby producing a large binding force.

JP 2006-147159 A JP-A-2000-160118

Conventionally, when producing a pellet-shaped electrode for a battery, an active material, a conductive agent, and a binder are mixed to produce granular secondary particles, and the secondary particles are filled in a mold. Press molding is common.
However, since the above binder made of PTFE is chemically stable but has a strong binding force, when the positive electrode is molded into a pellet, there is a risk that the mold will not fill easily. There is a problem that the releasability from the mold is deteriorated.

In view of such conventional problems, the present invention provides a positive electrode for a coin-shaped non-aqueous electrolyte secondary battery that contains a mixture exhibiting stable physical properties and a lubricant so that it can be easily released from a mold during molding. It is an object of the present invention to efficiently provide a coin-shaped non-aqueous electrolyte secondary battery having the positive electrode, and to provide a method for manufacturing a positive electrode for a coin-shaped non-aqueous electrolyte secondary battery.

(1) In order to solve the above problems, a positive electrode for a coin-shaped nonaqueous electrolyte secondary battery according to one aspect of the present invention includes a positive electrode active material made of a transition metal composite oxide, a conductive aid, and the positive electrode active material. and a granular mixture containing a binder made of one or more of fluororesin or polyvinylidene fluoride in addition to the conductive aid, and a lubricant made of hydrophobic silica, comprising the mixture and the lubricant It consists of a pellet-shaped compression molded body.

By using a binder composed of one or more of fluororesin and polyvinylidene fluoride, an effective bonding state between the positive electrode active material and the conductive aid can be obtained. Therefore, when a battery having a positive electrode of this structure is constructed, a sufficient discharge capacity and a large current can be supplied.
In addition to the mixture exhibiting stable physical properties, it contains a lubricant composed of hydrophobic silica, so that it is possible to ensure good releasability from the mold during molding. In addition, it is also excellent in fillability with respect to molds.

(2) In order to solve the above problems, a positive electrode for a coin-shaped non-aqueous electrolyte secondary battery according to one aspect of the present invention is such that the particle size of the granular mixture is 75 to 500 μm, and the specific surface area of the lubricant is is 90 to 130 m ² /g, and the mass ratio of the lubricant to the total mass of the mixture is 0.5 to 2% by mass.

Since it contains a suitable amount of lubricant in a mass ratio of 0.5 to 2% by mass with respect to the total mass of the mixture, it has excellent mold filling properties and excellent release properties from the mold after molding. . In addition, when the particle size of the granular mixture is in the range of 75 to 500 μm, it is possible to obtain a compact that is sufficiently compacted during molding.
Therefore, it is possible to efficiently obtain a positive electrode that does not lose its shape, crack, or the like when it is released from the mold, and the yield of positive electrode production is improved.
Further, when a battery having a positive electrode of this structure is constructed, a battery capable of supplying a sufficient discharge capacity and a large current can be provided.

(3) The positive electrode for a coin-shaped non-aqueous electrolyte secondary battery according to one aspect is characterized in that the positive electrode active material comprises a lithium-transition metal composite oxide.
(4) The positive electrode for a coin-shaped non-aqueous electrolyte secondary battery according to the above aspect is characterized in that the positive electrode active material is made of lithium cobalt oxide.
(5) A coin-shaped non-aqueous electrolyte secondary battery according to the present embodiment includes the positive electrode for a coin-shaped non-aqueous electrolyte secondary battery according to any one of (1) to (4).

If the positive electrode active material is made of lithium cobalt oxide, it is possible to construct a battery with a positive electrode capable of supplying a sufficient discharge capacity and a large amount of current. However, a stable battery can be provided.

(6) In the method for manufacturing a positive electrode for a coin-shaped non-aqueous electrolyte secondary battery according to the present embodiment, a positive electrode active material made of a transition metal composite oxide, a conductive aid, and in addition to the positive electrode active material and the conductive aid, , fluororesin or polyvinylidene fluoride, a binder consisting of at least one of them is mixed, water is added, granulated to form a granular mixture having a particle size of 75 to 500 μm, and the granular mixture is hydrophobic It is characterized by adding a lubricant composed of polysilica, mixing the mixture, and forming pellets by compression molding.

(7) In the production method of this embodiment, the specific surface area of the lubricant is 90 to 130 m ² /g, and the mass ratio of the lubricant to the total mass of the mixture is 0.5 to 2% by mass. Addition of a lubricant is preferred.
(8) In the production method of this embodiment, it is preferable to use a lithium-transition metal composite oxide as the positive electrode active material.
(9) In the manufacturing method of the present embodiment, lithium cobaltate is preferably used as the positive electrode active material.

According to this aspect, by using a binder made of fluororesin or polyvinylidene fluoride, an effective bonding state between the positive electrode active material and the conductive aid can be obtained. Therefore, when a battery having a positive electrode of this structure is constructed, a sufficient discharge capacity and a large current can be supplied. Moreover, since it contains a lubricant made of hydrophobic silica in addition to the mixture, it is possible to improve both the mold filling property and the release property, and it is easy to manufacture a positive electrode that does not have defects such as cracks. can be made.
In particular, if the structure contains a suitable amount of lubricant in a mass ratio of 0.5 to 2% by mass with respect to the total mass of the mixture, it has excellent mold filling properties and mold releasability. An excellent positive electrode can also be obtained.

According to the production method of the present embodiment, a positive electrode active material and a conductive agent are mixed with a binder made of at least one of fluororesin and polyvinylidene fluoride, water is added, and the particles are granulated to have a particle size of 75 to 75. A 500 μm granular mixture can be formed. Then, a lubricant made of hydrophobic silica is added to this granular mixture, mixed, and compression-molded to form pellets.
According to this production method, the positive electrode for the coin-shaped non-aqueous electrolyte secondary battery can be obtained with a good yield without causing cracks or the like, since the molded article can be easily separated from the mold due to good releasability. be able to.

FIG. 1 is a cross-sectional view schematically showing a non-aqueous electrolyte secondary battery that is one embodiment of the present invention.

An example of a non-aqueous electrolyte secondary battery, which is one embodiment of the present invention, will be given and its configuration will be described in detail with reference to FIG.
In the following description, as a button-type or coin-type electrochemical cell, a lithium-ion secondary battery (hereinafter simply referred to as "battery"), which is a type of non-aqueous electrolyte secondary battery, will be taken as an example. The non-aqueous electrolyte secondary battery described below is specifically a non-aqueous electrolyte secondary battery in which an active material used as a positive electrode or a negative electrode and an electrolyte are housed in a container.
In addition, in the drawings used for the following explanation, the scale of each member is appropriately changed in order to make each member recognizable, so the relative sizes of each member are limited to those shown in the drawings. Of course not.

A non-aqueous electrolyte secondary battery 1 of the present embodiment shown in FIG. 1 is a so-called coin (button) type battery. This non-aqueous electrolyte secondary battery 1 is arranged in a storage container 2 between a positive electrode 10 capable of intercalating/releasing lithium ions, a negative electrode 20 capable of intercalating/releasing lithium ions, and between the positive electrode 10 and the negative electrode 20. and an electrolyte (electrolyte solution) 50 containing at least a supporting salt and an organic solvent.
More specifically, the non-aqueous electrolyte secondary battery 1 of this embodiment includes a bottomed cylindrical positive electrode can 12 and an opening 12 a of the positive electrode can 12 , which is fixed with a gasket 40 interposed therebetween. and a lidded cylindrical (hat-shaped) negative electrode can 22 that forms an accommodation space in the bottom. By crimping the periphery of the opening 12a of the positive electrode can 12 inward, that is, toward the negative electrode can 22 side, the storage container 2 that seals the storage space is configured.

In the non-aqueous electrolyte secondary battery 1 of the present embodiment, the positive electrode 10 includes a positive electrode active material made of a lithium transition metal oxide such as lithium cobaltate (LiCoO ₂ ), a conductive aid, and a binder (binder). In this battery, the negative electrode 20 includes a negative electrode active material such as lithium titanate, a conductive aid made of graphite, and a binder.
The lithium transition metal oxide used as the positive electrode active material may be lithium nickelate (LiNiO ₂ ), lithium titanate (Li ₄ Ti ₅ O ₁₂ ), lithium manganate (Li ₄ Mn ₅ O ₁₂ ), or the like. good. Further, the negative electrode active material may be silicon (Si), Si oxide (SiO), lithium titanate (Li ₄ Ti ₅ O ₁₂ ), carbon (C), lithium-aluminum (Li-Al) alloy, or the like. .
The detailed structure of each part of the non-aqueous electrolyte secondary battery 1 will be described below.

A positive electrode 10 provided on the positive electrode can 12 side and a negative electrode 20 provided on the negative electrode can 22 side are arranged facing each other via a separator 30 in the storage space sealed by the storage container 2 . is filled.
Moreover, as shown in FIG. 1 , the gasket 40 is narrowly inserted along the inner peripheral surface of the positive electrode can 12 and is connected to the outer periphery of the separator 30 to hold the separator 30 .
Moreover, the positive electrode 10 , the negative electrode 20 and the separator 30 are impregnated with an electrolyte (electrolyte solution) 50 filled in the storage container 2 .

In the non-aqueous electrolyte secondary battery 1 of the example shown in FIG. It is electrically connected to the inner surface of the negative electrode can 22 . In the present embodiment, the non-aqueous electrolyte secondary battery 1 including the positive electrode current collector 14 and the negative electrode current collector 24 as illustrated in FIG. Instead, for example, a configuration in which the positive electrode can 12 also serves as a positive electrode current collector and the negative electrode can 22 also serves as a negative electrode current collector may be adopted.

The non-aqueous electrolyte secondary battery 1 of the present embodiment is roughly configured as described above, so that lithium ions move from one of the positive electrode 10 and the negative electrode 20 to the other, thereby accumulating (charging) an electric charge. A battery that can release (discharge) an electric charge.

(Positive can and negative can)
In the present embodiment, the positive electrode can 12 constituting the storage container 2 is, as described above, formed in a bottomed cylindrical shape and has a circular opening 12a in plan view. As a material for such a positive electrode can 12, conventionally known materials can be used without any limitation. For example, stainless steel such as NAS64 can be exemplified.

Further, as described above, the negative electrode can 22 is configured in a lidded cylindrical shape (hat shape), and the tip portion 22a thereof is configured to enter the positive electrode can 12 through the opening 12a. Similar to the material of the positive electrode can 12, conventionally known stainless steel can be used as the material of the negative electrode can 22. For example, SUS304-BA can be used. Further, for the negative electrode can 22, for example, a clad material obtained by press-contacting copper, nickel, or the like to stainless steel can be used.

As shown in FIG. 1, the cathode can 12 and the anode can 22 are fixed by crimping the periphery of the opening 12a of the cathode can 12 toward the anode can 22 with a gasket 40 interposed therebetween. For this reason, the non-aqueous electrolyte secondary battery 1 is hermetically held in a state in which the housing space is formed. Therefore, the maximum inner diameter of the positive electrode can 12 is set larger than the maximum outer diameter of the negative electrode can 22 .

The plate thickness of the metal plate material used for the positive electrode can 12 and the negative electrode can 22 is generally about 0.1 to 0.3 mm. It can be configured as a degree.

In the example shown in FIG. 1, the tip portion 22a of the negative electrode can 22 has a folded shape, but the present invention is not limited to this. It is also possible to apply the present invention to a shape that does not have.

Non-aqueous electrolyte secondary batteries to which the configuration described in detail in the present embodiment can be applied include, for example, 920 size (outer diameter φ9.0 mm), which is a general size of coin-type non-aqueous electrolyte secondary batteries. 5 mm×height 2.0 mm), 621 size (external diameter φ6.8 mm×height 2.1 mm), and batteries of various sizes.

(gasket)
As shown in FIG. 1 , the gasket 40 is formed in an annular shape along the inner peripheral surface of the positive electrode can 12 , and the front end portion 22 a of the negative electrode can 22 is arranged inside the annular groove 41 .
Further, for example, the material of the gasket 40 is preferably a resin having a heat distortion temperature of 230° C. or higher. If the heat distortion temperature of the resin material used for the gasket 40 is 230° C. or higher, heat is generated when the non-aqueous electrolyte secondary battery 1 is used or stored in a high-temperature environment, or when the non-aqueous electrolyte secondary battery 1 is in use. Even if this occurs, it is possible to prevent the electrolyte 50 from leaking due to significant deformation of the gasket.

Examples of materials for the gasket 40 include polypropylene resin (PP), polyphenyl sulfide (PPS), polyethylene terephthalate (PET), polyamide, liquid crystal polymer (LCP), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin. (PFA), polyetheretherketone resin (PEEK), polyethernitrile resin (PEN), polyetherketone resin (PEK), polyarylate resin, polybutylene terephthalate resin (PBT), polycyclohexanedimethylene terephthalate resin, polyether Plastic resins such as sulfone resins (PES), polyaminobismaleimide resins, polyetherimide resins, and fluorine resins such as polytetrafluoroethylene (PTFE) and ethylene-tetrafluoroethylene (ETFE) can be used. Among these, the use of any one of PP, PPS, and PEEK for the gasket 40 can prevent the gasket from significantly deforming during use or storage in a high-temperature environment, and can seal the non-aqueous electrolyte secondary battery. It is preferable from the viewpoint of further improving the properties.

Also, the gasket 40 can be suitably used by adding glass fiber, mica whisker, fine ceramic powder, or the like to the above material in an amount of 30% by mass or less. By using such a material, it is possible to prevent the electrolyte solution 50 from leaking due to significant deformation of the gasket due to high temperatures.

Further, the inner surface of the annular groove of the gasket 40 may be coated with a sealing agent. As such a sealing agent, asphalt, epoxy resin, polyamide resin, butyl rubber adhesive, or the like can be used. Also, the sealant is applied to the inside of the annular groove 41 and then dried before use.

The gasket 40 is sandwiched between the positive electrode can 12 and the negative electrode can 22, and at least a portion of the gasket 40 is compressed. 1 can be reliably sealed and the gasket 40 is not broken.

(Electrolytes)
The non-aqueous electrolyte secondary battery 1 of the present embodiment uses an electrolyte (electrolyte solution) 50 containing at least an organic solvent and a supporting salt. In the case of the electrolytic solution 50, the organic solvent is any one of propylene carbonate (PC), which is a cyclic carbonate solvent, ethylene carbonate (EC), which is a cyclic carbonate solvent, and ethyl methyl carbonate (EMC), which is a chain carbonate solvent, or A mixed solvent is preferably used. Alternatively, an ionic liquid or a solid electrolyte may be used as the electrolyte.
In the case of the electrolytic solution, a supporting salt is usually dissolved in a non-aqueous solvent such as an organic solvent.

As the supporting salt used in the electrolytic solution 50, a known Li compound that is added as a supporting salt to the electrolytic solution in the non-aqueous electrolyte secondary battery can be used, and is not particularly limited. For example, in consideration of thermal stability, lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate, lithium bisperfluoromethylsulfonylimide, lithium bisperfluoroethylsulfonylimide, lithium bistrifluoro methanesulfonimide (Li(CF ₃ SO ₂ ) ₂ N) and the like. Among these, it is particularly preferable to use Li(CF ₃ SO ₂ ) ₂ N or LiPF ₆ as the supporting salt, since the heat resistance of the electrolytic solution is enhanced and the decrease in capacity at high temperatures can be suppressed.
In addition, the supporting salt may be used alone or in combination of two or more.

The content of the supporting salt in the electrolytic solution 50 can be determined in consideration of the type of the supporting salt and the type of the positive electrode active material described later. 1.8 mol/L is more preferred, and approximately 1.5 mol/L is particularly preferred.
If the concentration of the supporting salt in the electrolytic solution 50 is too high or too low, the electrical conductivity may decrease and the battery characteristics may be adversely affected. The amount is preferably regulated within the above range.

(positive electrode)
In the non-aqueous electrolyte secondary battery 1 of the present embodiment, as an example of the positive electrode 10, a mixture containing a positive electrode active material made of lithium cobaltate (LiCoO ₂ ), a conductive aid, and a binder (binder) , a lubricant can be used.

A positive electrode active material made of lithium cobalt oxide is used for the positive electrode 10, and the negative electrode ₂₀ , which will be described later, contains lithium titanate _{( Li4Ti5O12} ) as a negative electrode active material. Also, a CTL battery with a high capacity can be configured.
The positive electrode active material is preferably the combination described above, but other lithium-transition metal composite oxides listed in the description of the positive electrode 10 described above may also be used.

When a lithium transition metal oxide such as lithium cobalt oxide is used as the positive electrode active material, it is granulated as described below to form a granular mixture having a particle size of about 75 to 500 μm, and a lubricant is added and then pelletized. It is preferable to mold into a shape.
The particle size (D50) of the lithium cobalt oxide used in preparing the granular mixture is not particularly limited, but is preferably 2 to 20 μm, more preferably 4 to 8 μm, for example.
In addition, the "particle diameter (D50) of the positive electrode active material" in the present invention means a particle diameter measured by a laser diffraction method and a median diameter.

The content of the positive electrode active material in the positive electrode 10 is determined in consideration of the discharge capacity required for the non-aqueous electrolyte secondary battery 1, and is preferably in the range of 50 to 95% by mass, for example. If the content of the positive electrode active material is equal to or higher than the lower limit of the preferred range, a sufficient discharge capacity can be easily obtained, and if it is equal to or lower than the preferred upper limit, the positive electrode 10 can be easily molded.

The positive electrode 10 contains a conductive aid (hereinafter, the conductive aid used in the positive electrode 10 may be referred to as a "positive conductive aid").
Examples of positive electrode conductive aids include carbonaceous materials such as graphite, furnace black, ketjen black, and acetylene black.
As for the positive electrode conductive aid, one of the above may be used alone, or two or more thereof may be used in combination.
Also, the content of the positive electrode conductive aid in the positive electrode 10 is preferably 4 to 40% by mass, more preferably 7 to 20% by mass. If the content of the positive electrode conductive aid is at least the lower limit value of the preferable range, sufficient conductivity can be easily obtained. In addition, it becomes easy to shape|mold when shape|molding an electrode in a pellet form. On the other hand, when the content of the positive electrode conductive additive in the positive electrode 10 is equal to or less than the upper limit value of the preferable range, the positive electrode 10 can easily obtain a sufficient discharge capacity.

The positive electrode 10 contains a binder (hereinafter, the binder used for the positive electrode 10 may be referred to as a "positive electrode binder").
The positive electrode binder is preferably made of fluororesin such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF).
By using PTFE as the positive electrode binder, the fibrous PTFE can effectively bond the positive electrode active material and the conductive aid.
In addition, by using PVDF as the positive electrode binder, the positive electrode binder wraps the positive electrode active material and pulls the conductive aid, so that the positive electrode active material and the conductive aid are effectively bonded. Therefore, by using PTFE or PVDF as the positive electrode binder, a sufficient discharge capacity can be obtained and a large current can be supplied. From the viewpoint of obtaining the above effects more remarkably, it is more preferable to use PTFE as the positive electrode binder.
Moreover, the positive electrode binder may be used alone or in combination of two of the above. The content of the positive electrode binder in the positive electrode 10 can be, for example, 1 to 20% by mass.

As the lubricant, a lubricant that suppresses adhesion between particles can be selected, and a lubricant made of hydrophobic silica such as hydrophobic fumed silica can be used. Hydrophobic fumed silica is a type of hydrophobic silica whose surface is treated with various silanes such as dimethylchlorosilane, and has a specific surface area (BET) of 90 to 130 m ² /g. By adding a small amount of the above-mentioned lubricant, the granular mixture becomes a state in which it can slide somewhat in the mold, and the releasability after molding is improved.
The hydrophobic silica used in the present embodiment is not limited to hydrophobic fumed silica, and may be silica produced by an arc method other than fumed silica (flame method silica).

The content of the lubricant in the positive electrode 10 can be in the range of 0.5 to 2.0% by mass relative to the total mass of the mixture. If the content of the lubricant is less than 0.5% by mass, releasability from the mold deteriorates. Moreover, the fillability into the mold also deteriorates. If the content of the lubricant exceeds 2.0% by mass, the amount of the active material in the electrode is relatively reduced, making it difficult to obtain sufficient characteristics (capacity) when used as a battery. For this reason, it is desirable that the amount of the lubricant to be added is as low as possible, even within the above range.

The size of the positive electrode 10 is determined according to the size of the non-aqueous electrolyte secondary battery 1 .
The thickness of the positive electrode 10 is also determined according to the size of the non-aqueous electrolyte secondary battery 1. If the non-aqueous electrolyte secondary battery 1 is a coin type for various electronic devices, for example, the thickness It is formed to have a thickness of about 300 to 1000 μm.

"Manufacturing method of positive electrode"
In order to manufacture the positive electrode 10, water is added to a mixture of the positive electrode active material having the particle size described above, the conductive aid and the binder in the amounts described above, and the resulting mixture is granulated to obtain particles having a particle size of 75 to 500 μm. A granular positive electrode mixture is obtained. The positive electrode 10 can be obtained by putting a mixture obtained by adding and mixing a predetermined amount of lubricant to this positive electrode mixture into a mold and molding the mixture under pressure into a pellet shape in the mold.
The pressure during the pressure molding is determined in consideration of the type of the positive electrode conductive aid and the like, and can be, for example, 0.2 to 5 ton/cm ² .

At the time of granulation, for example, the particles of lithium cobaltate are mixed with the above conductive agent powder and binder in a predetermined ratio, water is added in an amount of about 10 to 30% with respect to the total weight of the mixture, and the whole is mixed with a mixer. It can be granulated by kneading for about minutes to several tens of minutes. After this granulation treatment, the granules are dried to obtain granular granules having a particle size of about 75 to 500 μm.
After granulation, the dried granules also contain fine particles of less than 75 μm, so the dried granules are sieved for the purpose of removing these fine particles. , to obtain a granular mixture having a particle size of about 75 to 500 μm.

If the particle size of the granulated mixture is less than 75 μm, there is a problem that when the mixture is supplied to the mold, the pipe becomes clogged with the finely powdered mixture, making it impossible to supply the mixture.
If the particle size of the granular material mixture exceeds 500 μm, the amount of the material mixture filled in the mold will vary, causing a problem of increased weight variation of the positive electrode.

Lubricant is added and mixed in a mass ratio of 0.5 to 2% by mass with respect to the total mass of the granular mixture, put into a mold, and pressurized with the above-described predetermined pressure to obtain a pellet-shaped positive electrode 10. can be manufactured.

By adding a lubricant with a mass ratio of 0.5 to 2.0% by mass relative to the mass of the mixture before pouring it into the mold, the injection efficiency is improved, and the mixture can be smoothly poured into every corner of the mold. can be filled. Moreover, when the positive electrode 10 is removed from the mold after molding, the positive electrode 10 can be removed with good releasability. Therefore, the positive electrode 10 can be safely removed from the mold without causing defects such as cracks in the mold. Therefore, the yield in manufacturing the positive electrode 10 can be improved.

As the positive electrode current collector 14, a conventionally known one can be used, and examples thereof include a conductive resin adhesive using carbon as a conductive filler.

(negative electrode)
In the non-aqueous electrolyte secondary battery 1 of the present embodiment, an example of the negative electrode 20 includes a negative electrode active material made of lithium titanate (Li ₄ Ti ₅ O ₁₂ ), a conductive aid made of graphite, and a binder. use things

By using a negative electrode active material made of lithium titanate for the negative electrode 20 and using a positive electrode active material made of lithium cobaltate as the positive electrode 10, the operating voltage is as high as 2 V or higher and the capacity is high. A CTL battery can be constructed. Although the above-described combination of the negative electrode active materials is desirable, other materials listed in the description of the negative electrode 20 described above may be used.

When lithium titanate is used as the negative electrode active material, its particle size (D50) is not particularly limited, and is preferably 3 to 7 μm, more preferably 4 to 6 μm, for example.
If the particle size (D50) of the negative electrode active material is less than the lower limit of the preferred range, the reactivity of the non-aqueous electrolyte secondary battery increases when exposed to high temperatures, making it difficult to handle. , the discharge rate may decrease.

The content of the negative electrode active material in the negative electrode 20 is determined in consideration of the discharge capacity required for the non-aqueous electrolyte secondary battery 1, and is preferably 50% by mass or more, more preferably 60 to 80% by mass.
In the negative electrode 20, if the content of the negative electrode active material made of the above material is equal to or higher than the lower limit of the preferred range, a sufficient discharge capacity can easily be obtained. Cheap.

The negative electrode 20 contains graphite as a conductive aid (hereinafter, the conductive aid used in the negative electrode 20 may be referred to as a “negative conductive aid”) in an amount of 7% by mass or more and 10% by mass with respect to the total mass of the negative electrode 20. Including less than The non-aqueous electrolyte secondary battery 1 of the present embodiment uses lithium cobaltate as a positive electrode active material in the positive electrode 10 and lithium titanate as a negative electrode active material in the negative electrode 20. Further, graphite (a conductive agent) contained in the negative electrode is used. By limiting the content of the non-aqueous electrolyte secondary battery 1 to the above range, the current flow in the negative electrode is improved while ensuring a sufficient capacity for the non-aqueous electrolyte secondary battery 1 . As a result, even with a small size, it is possible to obtain a sufficient discharge capacity and supply a large current.

Note that if the content of graphite (conductive assistant) in the negative electrode 20 is less than 7% by mass, the conductivity is lowered and the discharge current characteristics are also lowered.
On the other hand, when the content of graphite (conductive assistant) in the negative electrode 20 is 10% by mass or more, the content of the negative electrode active material in the negative electrode 20 is relatively decreased, resulting in a decrease in discharge capacity.
Further, from the viewpoint of obtaining the above effect more remarkably, the content of the conductive aid made of graphite in the negative electrode 10 is more preferably in the range of 8 to 9% by mass with respect to the total mass of the negative electrode 20. preferable.

The negative electrode 20 contains a binder (hereinafter, the binder used for the negative electrode 20 may be referred to as "negative electrode binder").
Examples of negative electrode binders include polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PA), polyimide (PI), and polyimideamide (PAI). It is preferable to use

Moreover, one type of negative electrode binder may be used alone, or two or more types may be used in combination. When PA is used as the negative electrode binder, it is preferable to adjust the PA to pH 3 to 10 in advance. For adjusting the pH in this case, for example, an alkali metal hydroxide such as lithium hydroxide or an alkaline earth metal hydroxide such as magnesium hydroxide can be used.
The content of the negative electrode binder in the negative electrode 20 is, for example, 1 to 20% by mass.
The size and thickness of the negative electrode 20 are the same as those of the positive electrode 10 .
That is, the thickness of the negative electrode 20 is determined according to the size of the non-aqueous electrolyte secondary battery 1. If the non-aqueous electrolyte secondary battery 1 is a coin type for various electronic devices, for example, the thickness It is formed to have a thickness of about 300 to 1000 μm.

As a method of manufacturing the negative electrode 20, for example, the above material is used as the negative electrode active material, and if necessary, a negative electrode conductive aid and/or a negative electrode binder are mixed to prepare a negative electrode mixture, and this negative electrode mixture is prepared. A method of pressure-molding into an arbitrary shape can be adopted.
In this case, the pressure during pressure molding is determined in consideration of the type of the negative electrode conductive aid, etc., and can be, for example, 0.2 to 5 tons/cm ² .

Also, the negative electrode current collector 24 can be configured using the same material as the positive electrode current collector 14 . For example, a conductive resin adhesive using carbon as a conductive filler can be exemplified.

(separator)
The separator 30 is interposed between the positive electrode 10 and the negative electrode 20, and an insulating film having high ion permeability, excellent heat resistance, and predetermined mechanical strength is used.
As the separator 30, any material that has been conventionally used as a separator for non-aqueous electrolyte secondary batteries and that satisfies the above characteristics can be applied without any limitation. Examples include alkali glass, borosilicate glass, quartz glass, lead glass, and the like. glass, polypropylene (PP), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyethylene terephthalate (PET), polyamideimide (PAI), polyamide, polyimide (PI), aramid, cellulose, fluororesin, ceramics, etc. Examples include nonwoven fabrics and fibers made of resin. As the separator 30, among the above, those made of a porous polymer material such as polypropylene (PP) resin can provide a separator having a high ion permeability while ensuring sufficient mechanical strength. It is particularly preferable because the internal resistance of the secondary battery is reduced and the discharge capacity is further improved.
The thickness of the separator 30 is determined in consideration of the size of the non-aqueous electrolyte secondary battery 1, the material of the separator 30, etc., and can be, for example, about 5 to 300 μm.

[Use of non-aqueous electrolyte secondary battery]
As described above, the non-aqueous electrolyte secondary battery 1 of the present embodiment can obtain a sufficient discharge capacity and can supply a large current even if it is small in size. It is suitable for use as a power supply for watches with various functions such as and various small electronic devices.

As described above, according to the non-aqueous electrolyte secondary battery 1 configured using the positive electrode 10 according to the embodiment of the present invention, lithium cobaltate is used as the positive electrode active material in the positive electrode 10, and lithium cobalt oxide is used as the negative electrode active material in the negative electrode 20. Since lithium titanate is used, it is possible to obtain a sufficient discharge capacity and supply a large current even with a small size while securing a sufficient capacity as a non-aqueous electrolyte secondary battery. be possible.
Furthermore, in the above-described structure, since the granular mixture constituting the positive electrode 10 is molded with a lubricant in a suitable range of 0.5 to 2%, the mixture can be smoothly put into the mold. , and excellent releasability when the molded product is taken out after molding. Therefore, it is possible to reliably obtain the positive electrode 10 as a non-defective product free from cracks or the like at the time of demolding.
For this reason, the inclusion of the lubricant in a suitable range of 0.5 to 2% contributes to the improvement of the yield when manufacturing the positive electrode 10 in the form of pellets.

As a positive electrode mixture, 90% by mass of lithium cobalt oxide (LiCoO ₂ ), 8.0% of graphite powder (SP-270 manufactured by Nippon Graphite Co., Ltd.), and 2.0% of polytetrafluoroethylene (PTFE) were mixed, and the mass ratio was 20%. of water was added, stirred and mixed with a mixer, and dried.
By this stirring and mixing treatment, mixed particles of fine particles having a particle size of less than 75 μm and granules having a particle size of 75 to 500 μm were obtained. A mixture consisting of granular granules having a particle size of 75 to 500 μm was selected from the mixed particles by sieving.

74 mg of this granular mixture was weighed, and 0.5% by mass of a lubricant (hydrophobic fumed silica; R972 manufactured by Nippon Aerosil Co., Ltd.) was added to the total weight of the mixture. A mixture of Example 2 in which 1% by mass of lubricant was added and a mixture of Example 3 in which 2% by mass of lubricant was added and mixed were obtained.
The specific surface area (BET) of the hydrophobic fumed silica used here is 110±20 m ² /g. These mixtures were separately weighed and individually put into a mold, and pressure-molded at a pressure of 6 tons to obtain disk-shaped pellet-shaped positive electrodes (φ 6.3 × t 0.7 mm) of Examples 1, 2, and 3. manufactured.
In addition, without mixing the lubricant, the granules were put into a mold as they were, and pressed under the same conditions as in the above example to produce a positive electrode pellet of Comparative Example 1.
The positive electrodes of Examples 1, 2, and 3 and the positive electrode of Comparative Example 1 were examined for releasability from the mold, and the results are summarized in Table 1 below.

In Table 1, "adhered" means that the molding itself adhered to the tip of the punch. If this adhesion occurs, in the case of continuous production, there is a possibility that the adhering matter will be pressed together with the mixture during the next molding.
As the results shown in Table 1 show, in the case of the positive electrode of Comparative Example 1 in which the mixture to which no lubricant was added was put directly into the mold and pressure-molded, the positive electrode adhered to the mold and was difficult to release. .
In contrast, none of the positive electrodes of Examples 1 to 3 adhered to the mold and could be removed from the mold without any problem.
From the above results, when a positive electrode is molded by putting a granular mixture with a particle size of 75 to 500 μm into a mold, a lubricant is added and mixed in the range of 0.5 to 2.0% by mass before molding. It has become clear that molding can be performed with good releasability.

Regarding the granular mixtures having a particle size of 75 to 500 μm used in Examples 1, 2 and 3, the angle of repose was measured by the method specified in JISR9301-2-2:1999, and was 30° in all cases. .
Since the angle of repose is 30°, it can be judged that the mixture can easily be injected into every corner of the inside of the mold and can easily obtain the desired shape of the molded product.

DESCRIPTION OF SYMBOLS 1... Non-aqueous electrolyte secondary battery, 2... Container, 10... Positive electrode, 12... Positive electrode can,
DESCRIPTION OF SYMBOLS 14... Positive electrode collector, 20... Negative electrode, 22... Negative electrode can, 24... Negative electrode collector,
30... Separator, 40... Gasket, 50... Electrolyte (electrolytic solution).

Claims (9)

A granular mixture comprising a positive electrode active material made of a transition metal composite oxide, a conductive aid, and a binder made of at least one of fluororesin and polyvinylidene fluoride in addition to the positive electrode active material and the conductive aid. A positive electrode for a coin-shaped non-aqueous electrolyte secondary battery, comprising: an agent and a lubricant comprising hydrophobic silica, wherein the positive electrode comprises a pellet-shaped compression-molded body comprising the mixture and the lubricant. The granular mixture has a particle size of 75 to 500 μm, the lubricant has a specific surface area of 90 to 130 m ² /g, and the mass ratio of the lubricant to the total mass of the mixture is 0.5 to 2 masses. %. 3. The positive electrode for a coin-shaped non-aqueous electrolyte secondary battery according to claim 1, wherein said positive electrode active material comprises a lithium transition metal composite oxide. 4. The positive electrode for a coin-shaped non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode active material comprises lithium cobalt oxide. A coin-shaped non-aqueous electrolyte secondary battery comprising the positive electrode for a coin-shaped non-aqueous electrolyte secondary battery according to any one of claims 1 to 4. A positive electrode active material composed of a transition metal composite oxide, a conductive agent, and a binder composed of at least one of fluororesin and polyvinylidene fluoride are mixed, water is added, and granules having a particle size of 75 to 500 μm are granulated. A coin-shaped non-aqueous electrolyte secondary battery characterized by forming a mixture in the form of granules, adding a lubricant made of hydrophobic silica to the mixture in granules, mixing the mixture, and compressing and molding the mixture into pellets. manufacturing method of positive electrode for The specific surface area of the lubricant is 90 to 130 m ² /g, and the lubricant is added so that the mass ratio of the lubricant to the total mass of the mixture is 0.5 to 2% by mass. Item 7. A method for producing a positive electrode for a coin-shaped non-aqueous electrolyte secondary battery according to item 6. 8. The method for producing a positive electrode for a coin-shaped non-aqueous electrolyte secondary battery according to claim 6, wherein a lithium transition metal composite oxide is used as the positive electrode active material. 8. The method for manufacturing a positive electrode for a coin-shaped non-aqueous electrolyte secondary battery according to claim 6, wherein lithium cobaltate is used as the positive electrode active material.

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