JP2020087903A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide a nonaqueous electrolyte secondary battery which is arranged so that a sufficient discharge capacity can be achieved even when it is compact in size, and which can supply a large current.SOLUTION: A nonaqueous electrolyte secondary battery 1 comprises a positive electrode 10, a negative electrode 20, an electrolyte solution 50 containing a supporting electrolyte and an organic solvent, and a separator 30, which are encased in a housing container 2 including a positive electrode can 12 and a negative electrode can 22. The positive electrode 10 contains a positive electrode active material consisting of lithium cobalt oxide, a conductive assistant and a binder. The negative electrode 20 contains a negative electrode active material consisting of lithium titanate, a conductive assistant consisting of graphite and a binder. The negative electrode 20 includes the conductive assistant by 7 mass% or more and less than 10 mass% to a total mass of the negative electrode 20.SELECTED DRAWING: Figure 1

Description

The present invention relates to a non-aqueous electrolyte secondary battery.

A non-aqueous electrolyte secondary battery such as a lithium secondary battery is used in a power supply unit of electronic devices, a power storage unit that absorbs fluctuations in power generation of a power generator, and the like. Examples of the lithium secondary battery include so-called CTL batteries using lithium cobalt oxide (LiCoO ₂ ) as a positive electrode active material and lithium titanate (Li ₄ Ti ₅ O ₁₂ ) as a negative electrode active material (for example, , Patent Document 1).

Since the CTL battery as described above has a high operating voltage of 2 V or more and a high capacity, it is widely used for power supplies such as watches having various functions such as alarms and various small electronic devices. ing.

JP, 7-335261, A

In addition to the operating voltage and the discharge capacity, the CTL battery as described above is also required to have a discharge characteristic capable of supplying a large current to various electronic devices equipped with the CTL battery. However, in particular, in a small size CTL battery for a watch, there is a problem that a discharge characteristic capable of supplying a sufficiently large current cannot be obtained only by increasing the capacity. On the other hand, when a large current is secured by reducing the resistance by increasing the amount of the conductive agent contained in the electrode, there is a problem that a sufficient discharge capacity cannot be obtained.

The present invention has been made in view of the above problems, and provides a non-aqueous electrolyte secondary battery that can obtain a sufficient discharge capacity and can supply a large current even in a small size. With the goal.

The inventors of the present invention have made extensive studies to solve the above problems. As a result, using lithium cobalt oxide as the positive electrode active material, in the configuration using lithium titanate as the negative electrode active material, the conductive auxiliary agent contained in the negative electrode is graphite, and by optimizing its content, The inventors have found that even a small-sized battery can obtain a discharge characteristic capable of supplying a large current while ensuring a sufficient discharge capacity, and completed the present invention.

That is, in the non-aqueous electrolyte secondary battery of the present invention, a positive electrode, a negative electrode, an electrolytic solution containing a supporting salt and an organic solvent, and a separator are housed in a housing container composed of a positive electrode can and a negative electrode can. A non-aqueous electrolyte secondary battery, wherein the positive electrode includes a positive electrode active material made of lithium cobalt oxide, a conductive auxiliary agent, and a binder, and the negative electrode is made of a negative electrode active material made of lithium titanate and graphite. And a binder, and the negative electrode contains the conductive auxiliary in an amount of 7% by mass or more and less than 10% by mass based on the total mass of the negative electrode.

According to the present invention, lithium cobalt oxide is used as the positive electrode active material, lithium titanate is used as the negative electrode active material, and the content of the conductive additive made of graphite contained in the negative electrode is defined in the above range. The current flow in the negative electrode becomes good while ensuring a sufficient capacity. This makes it possible to obtain a sufficient discharge capacity and supply a large current even with a small size.

Further, in the non-aqueous electrolyte secondary battery having the above structure, it is more preferable that the negative electrode contains the conductive additive in an amount of 8 to 9 mass% with respect to the total mass of the negative electrode.
By setting the content of the conductive additive in the negative electrode within the above range, sufficient discharge capacity can be more effectively ensured, and the current flow in the negative electrode also becomes better. As a result, even with a small size, a sufficient discharge capacity can be obtained and a larger current can be supplied.

Further, in the non-aqueous electrolyte secondary battery having the above structure, it is preferable that the binder contained in the positive electrode is made of a fluororesin.
Further, it is more preferable that the binder contained in the positive electrode is made of polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE).

By forming the binder contained in the positive electrode from the above-mentioned fluororesin, the binder can effectively connect the positive electrode active material and the conductive additive. As a result, a sufficient discharge capacity is more effectively secured, and the current flow in the negative electrode is also improved, so that even with a small size, a sufficient discharge capacity can be obtained, and a larger current can be obtained. Can be supplied.

Further, in the non-aqueous electrolyte secondary battery having the above configuration, it is preferable that the average particle diameter (D50) of the conductive additive contained in the positive electrode is smaller than the average particle diameter (D50) of the positive electrode active material.
Furthermore, in the above structure, the average particle diameter (D50) of the conductive additive contained in the positive electrode is 55 to 67% of the average particle diameter (D50) of the positive electrode active material. preferable.

By making the average particle diameter (D50) of the conductive additive contained in the positive electrode smaller than the average particle diameter (D50) of the positive electrode active material, the contact area between the positive electrode active material and the conductive auxiliary increases, Since the internal resistance of the battery can be reduced, the heavy load characteristic, that is, the discharge characteristic at a large current is further improved.
Furthermore, when the average particle diameter (D50) of the conductive additive is within the above range with respect to the average particle diameter (D50) of the positive electrode active material, the internal resistance of the battery can be reduced more effectively, The effect of improving the heavy load characteristics of is more remarkably obtained.

Further, in the non-aqueous electrolyte secondary battery having the above structure, the specific surface area of the conductive additive contained in the positive electrode is preferably 13 to 425 m ² /g.

Since the specific surface area of the conductive additive contained in the positive electrode is in the above range, the contact area between the positive electrode active material and the conductive additive is increased, and the internal resistance of the battery can be reduced, so that the heavy load characteristics are further improved. improves.

Further, in the non-aqueous electrolyte secondary battery having the above configuration, in the electrolytic solution, the organic solvent is propylene carbonate (PC) which is a cyclic carbonate solvent, ethylene carbonate (EC) which is a cyclic carbonate solvent, and a chain carbonate. A mixed solvent containing ethyl methyl carbonate (EMC) which is a solvent is preferable.

As in the above configuration, by using the organic solvent used for the electrolytic solution as a mixed solvent of the above compositions, a sufficient discharge capacity can be obtained in a wide temperature range, and a large current can be supplied. ..
Specifically, first, it is possible to obtain a large discharge capacity by using PC and EC having a high dielectric constant and a high solubility of a supporting salt as the cyclic carbonate solvent. Further, since PC and EC have high boiling points, for example, an electrolytic solution that is hard to volatilize even when used or stored in a high temperature environment can be obtained. Further, by using PC having a melting point lower than that of EC as EC as a cyclic carbonate solvent, it is possible to improve low-temperature characteristics. Further, low temperature characteristics are improved by using EMC having a low melting point as the chain carbonate solvent.

Further, in the non-aqueous electrolyte secondary battery having the above-mentioned configuration, the organic solvent may have a volume ratio of a mixture ratio of the propylene carbonate (PC), the ethylene carbonate (EC) and the ethyl methyl carbonate (EMC) of {PC: It is more preferable that EC:EMC}=1 to 5:1 to 5:6 to 12.

As in the above configuration, by defining the blending ratio of the organic solvent used in the electrolytic solution within an appropriate range, a sufficient discharge capacity can be obtained in a wide temperature range and a large current can be supplied.

Further, in the non-aqueous electrolyte secondary battery having the above structure, it is preferable that the supporting salt of the electrolytic solution is lithium hexafluorophosphate (LiPF ₆ ).
By using the above-mentioned lithium compound as the supporting salt used in the electrolytic solution, the heat resistance of the electrolytic solution can be increased and the decrease in capacity at high temperature can be suppressed.

Further, in the non-aqueous electrolyte secondary battery having the above structure, the separator may be made of polypropylene resin.
By forming the separator from polypropylene resin, which is a porous polymer material, while ensuring sufficient mechanical strength, a separator having a large ion permeability can be obtained, so that the internal resistance of the non-aqueous electrolyte secondary battery is It is reduced and the discharge capacity is further improved.

According to the non-aqueous electrolyte secondary battery of the present invention, as described above, lithium cobalt oxide is used as the positive electrode active material and lithium titanate is used as the negative electrode active material, respectively, and further, a conductive auxiliary made of graphite contained in the negative electrode is used. By defining the content of the agent to be 7% by mass or more and less than 10% by mass, a sufficient capacity is ensured and the flow of current in the negative electrode becomes good. This makes it possible to obtain a sufficient discharge capacity and supply a large current even with a small size.

FIG. 1 is a sectional view schematically showing a non-aqueous electrolyte secondary battery that is an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a non-aqueous electrolyte secondary battery that is an embodiment of the present invention, in which the content of a conductive auxiliary agent made of graphite in the negative electrode and the voltage after 10 seconds from the start of discharge are shown. It is a graph which shows a relationship. FIG. 3 is a diagram for explaining an example of a non-aqueous electrolyte secondary battery that is an embodiment of the present invention, in which the content of a conductive auxiliary agent made of graphite in the negative electrode and the voltage from the start of discharge become 1.4V. It is a graph which shows the relationship with time to. FIG. 4 is a diagram for explaining an example of the non-aqueous electrolyte secondary battery according to the embodiment of the present invention, in which the content of the conductive additive made of graphite in the negative electrode and the voltage from the start of discharge becomes 1.2V. It is a graph which shows the relationship with time to.

Hereinafter, an example of the non-aqueous electrolyte secondary battery according to the embodiment of the present invention will be described, and the configuration thereof will be described in detail with reference to FIG. The non-aqueous electrolyte secondary battery described in the present invention is specifically a non-aqueous electrolyte secondary battery in which an active material used as a positive electrode or a negative electrode and an electrolytic solution are contained in a container.

[Non-aqueous electrolyte secondary battery]
The 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 between a positive electrode 10 capable of occluding and releasing lithium ions, a negative electrode 20 capable of occluding and releasing lithium ions, and a positive electrode 10 and a negative electrode 20 in a storage container 2. And the electrolytic solution 50 containing at least a supporting salt and an organic solvent.
More specifically, the non-aqueous electrolyte secondary battery 1 of the present embodiment has a bottomed cylindrical positive electrode can 12, and a positive electrode can 12 fixed to the opening 12 a of the positive electrode can 12 with a gasket 40 interposed therebetween. And a negative electrode can 22 having a cylindrical shape (a hat shape) with a lid that forms a storage space between them, and the storage space is sealed by caulking the periphery of the opening 12a of the positive electrode can 12 to the inside, that is, the negative electrode can 22 side. The storage container 2 is provided.

In addition, in the non-aqueous electrolyte secondary battery 1 of the present embodiment, the positive electrode 10 includes a positive electrode active material made of lithium cobalt oxide, a conductive additive, and a binder, and the negative electrode 20 is made of a negative electrode active material made of lithium titanate. This is a so-called CTL battery including a substance, a conductive auxiliary agent made of graphite, and a binder. Then, in the non-aqueous electrolyte secondary battery 1, the negative electrode 20 is configured to include the conductive additive in an amount of 7% by mass or more and less than 10% by mass with respect to the total mass of the negative electrode 20.

In the storage space hermetically sealed by the storage container 2, the positive electrode 10 provided on the positive electrode can 12 side and the negative electrode 20 provided on the negative electrode can 22 face each other with the separator 30 in between, and the electrolytic solution 50 is filled. Has been done.
Further, as shown in FIG. 1, the gasket 40 is inserted along the inner peripheral surface of the positive electrode can 12, is connected to the outer periphery of the separator 30, and holds the separator 30.
Further, the positive electrode 10, the negative electrode 20, and the separator 30 are impregnated with the electrolytic solution 50 filled in the storage container 2.

In the non-aqueous electrolyte secondary battery 1 of the example shown in FIG. 1, the positive electrode 10 is electrically connected to the inner surface of the positive electrode can 12 via the positive electrode current collector 14, and the negative electrode 20 is connected to the negative electrode current collector 24. It is electrically connected to the inner surface of the negative electrode can 22 through. 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 illustrated in FIG. 1 is described as an example, but the present invention is not limited thereto. Instead, for example, the positive electrode can 12 may also serve as the positive electrode current collector, and the negative electrode can 22 may also serve as the negative electrode current collector.

The non-aqueous electrolyte secondary battery 1 of the present embodiment is configured as described above, so that lithium ions move from one of the positive electrode 10 and the negative electrode 20 to the other to accumulate (charge) charges. It is capable of discharging (discharging) charges.

(Positive electrode can and negative electrode can)
In the present embodiment, as described above, the positive electrode can 12 that constitutes the storage container 2 has a bottomed cylindrical shape and has the circular opening 12a in a plan view. As a material for such a positive electrode can 12, any conventionally known material can be used without any limitation, and examples thereof include stainless steel such as NAS64.

As described above, the negative electrode can 22 is configured in a cylindrical shape (hat shape) with a lid, and the tip end portion 22a thereof is configured to enter the positive electrode can 12 through the opening 12a. Like the material of the positive electrode can 12, the material of the negative electrode can 22 may be conventionally known stainless steel, and for example, SUS304-BA or the like can be used. In addition, for the negative electrode can 22, for example, a clad material formed by pressing stainless steel with copper, nickel, or the like can be used.

As shown in FIG. 1, the positive electrode can 12 and the negative electrode can 22 are fixed by caulking the periphery of the opening 12a of the positive electrode can 12 to the negative electrode can 22 side with the gasket 40 interposed therebetween, and the non-water can The electrolyte secondary battery 1 is hermetically held in the state where the accommodation space is formed. Therefore, the maximum inner diameter of the positive electrode can 12 is 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. For example, the average plate thickness of the entire positive electrode can 12 and the negative electrode can 22 is 0.20 mm. It can be configured as a degree.

In addition, in the example shown in FIG. 1, the tip 22a of the negative electrode can 22 has a folded shape, but the invention is not limited to this, and for example, a folded shape in which the end surface of the metal plate material is the tip 22a is used. The present invention can be applied to a shape that does not have any.

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

(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 tip portion 22 a of the negative electrode can 22 is arranged inside the annular groove 41.
Further, it is preferable that the gasket 40 is made of a resin having a heat distortion temperature of 230° C. or higher, for example. If the heat deformation temperature of the resin material used for the gasket 40 is 230° C. or higher, heat will be generated when the non-aqueous electrolyte secondary battery 1 is used or stored in a high temperature environment or during use of the non-aqueous electrolyte secondary battery 1. Even if it occurs, it is possible to prevent the electrolyte 50 from leaking due to the significant deformation of the gasket.

Examples of the material of the gasket 40 include polypropylene resin (PP), polyphenyl sulfide (PPS), polyethylene terephthalate (PET), polyamide, liquid crystal polymer (LCP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin. (PFA), polyether ether ketone resin (PEEK), polyether nitrile resin (PEN), polyether ketone resin (PEK), polyarylate resin, polybutylene terephthalate resin (PBT), polycyclohexane dimethylene terephthalate resin, polyether Examples include plastic resins such as sulfone resin (PES), polyaminobismaleimide resin, polyetherimide resin, and fluororesin. Among these, using any one of PP, PPS, and PEEK for the gasket 40 can prevent the gasket from being significantly deformed during use or storage in a high-temperature environment, thus sealing the non-aqueous electrolyte secondary battery. It is preferable from the viewpoint of further improving the property.

Further, as the gasket 40, a material obtained by adding glass fiber, michai whiskers, ceramic fine powder, or the like to the above material in an amount of 30% by mass or less can also be suitably used. By using such a material, it is possible to prevent the gasket from being significantly deformed due to high temperature and the electrolyte solution 50 from leaking.

Further, a sealant may be further applied to the inner surface of the annular groove of the gasket 40. As such a sealant, asphalt, epoxy resin, polyamide resin, butyl rubber adhesive, etc. can be used. The sealing agent is applied to the inside of the annular groove 41 and then dried.

The gasket 40 is sandwiched between the positive electrode can 12 and the negative electrode can 22, and at least a part thereof is in a compressed state. However, the compression rate at this time is not particularly limited, and the non-aqueous electrolyte secondary battery is not limited. The range may be such that the inside of 1 can be reliably sealed and the gasket 40 does not break.

(Electrolyte)
The nonaqueous electrolyte secondary battery 1 of the present embodiment uses, as the electrolytic solution 50, one containing at least an organic solvent and a supporting salt. The electrolytic solution 50 contains, as organic solvents, 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. It is preferable to use a mixed solvent consisting of
Such an electrolytic solution is usually composed of a supporting salt dissolved in a non-aqueous solvent such as an organic solvent, and its characteristics are determined in consideration of the heat resistance and viscosity required of the electrolytic solution.

In the present embodiment, the organic solvent used in the electrolytic solution 50 is a mixed solvent containing PC, EC which is a cyclic carbonate solvent, and EMC which is a chain carbonate solvent, so that it is sufficient in a wide temperature range. The non-aqueous electrolyte secondary battery 1 capable of obtaining a discharge capacity and supplying a large current can be realized.
Specifically, first, it is possible to obtain a large discharge capacity by using PC and EC having a high dielectric constant and a high solubility of a supporting salt as the cyclic carbonate solvent. Further, since PC and EC have high boiling points, for example, an electrolytic solution that is hard to volatilize even when used or stored in a high temperature environment can be obtained.
Further, by using PC having a melting point lower than that of EC as EC as a cyclic carbonate solvent, it is possible to improve low-temperature characteristics.
Further, low temperature characteristics are improved by using EMC having a low melting point as the chain carbonate solvent.

The cyclic carbonate solvent has a structure represented by the following (Chemical Formula 1), and includes, for example, propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), trifluoroethylene carbonate (TFPC), chloro. Examples thereof include ethylene carbonate (ClEC), trifluoroethylene carbonate (TFEC), difluoroethylene carbonate (DFEC) and vinylene carbonate (VEC). In the present embodiment, in particular, from the viewpoint of facilitating the formation of a film on the negative electrode 20 on the electrode and improving the low temperature characteristics, and further improving the capacity retention ratio at high temperatures, the following (Chemical formula 1) It is preferable to use two types of PC and EC as the cyclic carbonate solvent having a structure represented by.

However, in the above (Chemical formula 1), R1, R2, R3, and R4 represent any of hydrogen, fluorine, chlorine, an alkyl group having 1 to 3 carbon atoms, and a fluorinated alkyl group. In addition, R1, R2, R3, and R4 in the above (Chemical formula 1) may be the same or different.

In the present embodiment, as described above, by using PC and EC having high permittivity and high solubility of supporting salt as the cyclic carbonate solvent, sufficient discharge capacity can be obtained and large current can be supplied. Will be possible. In addition, since PC and EC have high boiling points, an electrolytic solution that is hard to volatilize even when used or stored in a high temperature environment can be obtained. Furthermore, by using PC, which has a lower melting point than EC as the cyclic carbonate solvent, mixed with EC, excellent low-temperature characteristics can be obtained.

The chain carbonate solvent has a structure represented by the following (Chemical Formula 2), and includes, for example, ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl propyl carbonate (MPC), Examples include ethyl propyl carbonate (EPC) and trifluoromethyl ethyl carbonate (TFMEC). In the present invention, in particular, from the viewpoint of securing sufficient discharge capacity and supply of large current, and improving the low temperature characteristics, the chain carbonate solvent having a structure represented by the following (Chemical formula 2) has a low melting point. It is preferable to employ EMC.

However, in the above (Chemical formula 2), R5 and R6 each represent hydrogen, fluorine, chlorine, an alkyl group having 1 to 3 carbon atoms, or a fluorinated alkyl group. R5 and R6 may be the same or different.

In this embodiment, as described above, excellent low-temperature characteristics are obtained by using EMC having a low melting point as the chain carbonate solvent. Further, since EMC has a low viscosity, the electric conductivity of the electrolytic solution is improved. Furthermore, since EMC is chemically stable, the effect of improving the pressure resistance of the non-aqueous electrolyte secondary battery can be obtained.

In the electrolytic solution 50, the mixing ratio of each solvent in the organic solvent is not particularly limited, but, for example, {PC:EC:EMC}=1-5:1-5:6-12 in volume ratio. Is preferred. Further, the above volume ratio is more preferably in the range of {PC:EC:EMC}=2 to 4:2 to 4:7 to 11, and generally {PC:EC:EMC}={1:1:. 3} is most preferable.
When the blending ratio of the organic solvent is in the above range, sufficient discharge capacity can be obtained in a wide temperature range and a large current can be supplied more remarkably as described above.

Specifically, if the mixing ratio of propylene carbonate (PC), which is a cyclic carbonate solvent, is at least the lower limit of the above range, a sufficient discharge capacity can be obtained by mixing PC with EC having a lower melting point than EC and using EC. And the effect of improving the low temperature characteristics can be obtained. Further, since PC and EC have high boiling points, for example, an electrolytic solution that is hard to volatilize even when used or stored in a high temperature environment can be obtained.
On the other hand, PC has a lower permittivity than EC and cannot increase the concentration of the supporting salt. Therefore, if the content is too high, it may be difficult to obtain a large discharge capacity. It is preferable to limit to the upper limit of the above range or less.

Further, when the blending ratio of ethylene carbonate (EC), which is a cyclic carbonate solvent, in the organic solvent is at least the lower limit of the above range, the dielectric constant of the electrolytic solution 50 and the solubility of the supporting salt are increased, and the nonaqueous electrolyte electrolyte It is possible to obtain a large discharge capacity as a secondary battery.
On the other hand, EC has poor electric conductivity due to its high viscosity, and its low melting point may lower its low temperature characteristics due to its high melting point. Therefore, its compounding ratio should be below the upper limit of the above range. It is preferable to limit.

Further, in the organic solvent, if the compounding ratio of ethyl methyl carbonate (EMC) which is a chain carbonate solvent is not less than the lower limit of the above range, the low melting point EMC is contained in the organic solvent in a predetermined amount, so that the low temperature The effect of improving the characteristics is remarkably obtained.
Further, since EMC has a low viscosity, the electrical conductivity of the electrolytic solution 50 is improved and a large discharge capacity can be obtained.
Furthermore, since EMC is chemically stable, the effect of improving the pressure resistance of the non-aqueous electrolyte secondary battery can be obtained.
On the other hand, if the content of EMC is too large, it may be difficult to obtain a large discharge capacity. Therefore, it is preferable to limit the blending ratio to the upper limit of the above range or less.

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

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, and is preferably 1 to 2 mol/L, and 1.2 to 1.8 mol/L is more preferable, and about 1.5 mol/L is particularly preferable.
If the concentration of the supporting salt in the electrolytic solution 50 is too high or too low, the conductivity may decrease and the battery characteristics may be adversely affected. The amount is preferably regulated within the above range.

As will be described later in detail, the non-aqueous electrolyte secondary battery 1 of the present embodiment uses lithium cobalt oxide as a positive electrode active material and lithium titanate as a negative electrode active material, and further contains a conductive auxiliary agent contained in the negative electrode. By limiting the content to the optimum range and using the electrolytic solution 50 having the above composition, a sufficient discharge capacity can be obtained in a wide temperature range and a large current can be supplied.

(Positive electrode)
In the non-aqueous electrolyte secondary battery 1 of the present embodiment, the positive electrode 10 includes a positive electrode active material made of lithium cobalt oxide (LiCoO ₂ ), a conductive auxiliary agent, and a binder.

By using a positive electrode active material made of lithium cobalt oxide for the positive electrode 10 and a negative electrode 20 described later containing lithium titanate (Li ₄ Ti ₅ O ₁₂ ) as the negative electrode active material, the operating voltage is as high as 2 V or higher. Also, a high capacity CTL battery can be constructed.

When lithium cobalt oxide is used as the positive electrode active material, the particle diameter (D50) is not particularly limited, and is preferably 2 to 10 μm, more preferably 4 to 8 μm.
If the particle size (D50) of the positive electrode active material is less than the lower limit of the above preferred range, it becomes difficult to handle because the reactivity increases when the non-aqueous electrolyte secondary battery is exposed to a high temperature, and the upper limit is exceeded. If it exceeds, the discharge rate may decrease.
The “particle diameter (D50) of the positive electrode active material” in the present invention means a particle diameter measured using a laser diffraction method and means a median diameter.

The content of the positive electrode active material in the positive electrode 10 is determined in consideration of the discharge capacity and the like required for the non-aqueous electrolyte secondary battery 1, and for example, the range of 50 to 95 mass% is preferable. When the content of the positive electrode active material is at least the lower limit value of the above preferred range, sufficient discharge capacity is easily obtained, and when it is at most the preferred upper limit value, the positive electrode 10 is easily molded.

The positive electrode 10 contains a conductive auxiliary agent (hereinafter, the conductive auxiliary agent used for the positive electrode 10 may be referred to as “positive electrode conductive auxiliary agent”).
Examples of the positive electrode conduction aid include carbonaceous materials such as graphite, furnace black, Ketjen black, and acetylene black.
As the positive electrode conduction aid, one type of the above may be used alone, or two or more types may be used in combination.
Further, the content of the positive electrode conductive additive in the positive electrode 10 is preferably 4 to 40% by mass, more preferably 10 to 25% by mass. When the content of the positive electrode conduction aid is at least the lower limit value of the above preferred range, sufficient conductivity is easily obtained. In addition, when the electrode is molded into a pellet shape, it becomes easy to mold. On the other hand, when the content of the positive electrode conductive additive in the positive electrode 10 is equal to or lower than the upper limit value of the preferable range, the positive electrode 10 is likely to have a sufficient discharge capacity.

The average particle diameter (D50) of the conductive additive contained in the positive electrode 10 is not particularly limited, but it is preferably smaller than the average particle diameter (D50) of the positive electrode active material.
Furthermore, the average particle diameter (D50) of the conductive additive contained in the positive electrode 10 is more preferably 55 to 67% of the average particle diameter (D50) of the positive electrode active material.

By setting the average particle diameter (D50) of the conductive auxiliary agent included in the positive electrode 10 to be smaller than the average particle diameter (D50) of the positive electrode active material, the contact area between the positive electrode active material and the conductive auxiliary agent increases. .. As a result, the internal resistance of the battery is reduced, so that the effect of further improving the heavy load characteristic, that is, the discharge characteristic at a large current is obtained.
Furthermore, the average particle diameter (D50) of the conductive additive contained in the positive electrode 10 is within the above range with respect to the average particle diameter (D50) of the positive electrode active material, so that the internal resistance of the battery is more effective. The effect of improving the heavy load characteristics can be more remarkably obtained.
The “average particle diameter (D50) of the conductive additive” in the present invention is a particle diameter measured by a laser diffraction method and means a median diameter.

The specific surface area of the conductive additive contained in the positive electrode 10 is preferably 13 to 425 m ² /g. When the specific surface area of the conductive additive contained in the positive electrode 10 is within the above range, the contact area between the positive electrode active material and the conductive auxiliary becomes large as in the above. As a result, the internal resistance of the battery can be reduced, and the effect of further improving the heavy load characteristics can be obtained.

The positive electrode 10 contains a binder (hereinafter, the binder used for the positive electrode 10 may be referred to as “positive electrode binder”).
As the positive electrode binder, a conventionally known substance can be used, and for example, a binder made of fluororesin can be used.
The positive electrode binder is preferably polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE). By using PVDF as the positive electrode binder, the positive electrode binder has an effect of pulling the conductive auxiliary agent while wrapping the positive electrode active material, so that the positive electrode active material and the conductive auxiliary agent are effectively bound to each other. Further, by using PTFE for the positive electrode binder, the positive electrode active material and the conductive auxiliary agent are effectively bound by the fibrous PTFE. Therefore, by using PVDF or PTFE as the positive electrode binder, a sufficient discharge capacity can be obtained and a large current can be supplied. From the viewpoint that such an effect is more remarkably obtained, it is more preferable to use PTFE as the positive electrode binder.

As the positive electrode binder, one of the above may be used alone, or two types may be used in combination.
The content of the positive electrode binder in the positive electrode 10 may be, for example, 1 to 20 mass %.

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

The positive electrode 10 can be manufactured by a conventionally known manufacturing method.
For example, as a method of manufacturing the positive electrode 10, a positive electrode active material and, if necessary, a positive electrode conductive additive and/or a positive electrode binder are mixed to form a positive electrode mixture, and the positive electrode mixture is added to an arbitrary shape. A method of pressure molding may be mentioned.
The pressure at the time of pressure molding is determined in consideration of the kind of the positive electrode conductive additive, and can be set to, for example, 0.2 to 5 ton/cm ² .

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

(Negative electrode)
In the non-aqueous electrolyte secondary battery 1 of the present embodiment, as the negative electrode 20, one containing a negative electrode active material made of lithium titanate (Li ₄ Ti ₅ O ₁₂ ), a conductive auxiliary agent made of graphite, and a binder. To use.

By using a negative electrode active material made of lithium titanate for the negative electrode 20 and a positive electrode active material made of lithium cobalt oxide as the positive electrode 10, the operating voltage is as high as 2 V or more and the capacity is high. A CTL battery can be constructed.

When lithium titanate is used as the negative electrode active material, the particle diameter (D50) is not particularly limited and is preferably 3 to 7 μm, more preferably 4 to 6 μm.
If the particle size (D50) of the negative electrode active material is less than the lower limit of the above preferred range, it becomes difficult to handle because the reactivity increases when the non-aqueous electrolyte secondary battery is exposed to high temperatures, and the upper limit is also exceeded. If it exceeds, 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 and the like 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 at least the lower limit value of the above preferred range, sufficient discharge capacity is easily obtained, and if it is at most the upper limit value, the negative electrode 20 is molded. Cheap.

The negative electrode 20 contains graphite as a conductive auxiliary agent (hereinafter, a conductive auxiliary agent used for the negative electrode 20 may be referred to as “a negative electrode conductive auxiliary agent”) in an amount of 7% by mass to 10% by mass based on the total mass of the negative electrode 20. Including less than. The non-aqueous electrolyte secondary battery 1 of the present embodiment uses lithium cobalt oxide 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, respectively, and further includes graphite (conductivity assistant) contained in the negative electrode. By limiting the content of the agent) within the above range, the current flow in the negative electrode becomes good while ensuring a sufficient capacity as the non-aqueous electrolyte secondary battery 1. This makes it possible to obtain a sufficient discharge capacity and supply a large current even with a small size.

When the content of graphite (conductivity auxiliary agent) in the negative electrode 20 is less than 7% by mass, the conductivity is lowered and the discharge current characteristic is also lowered.
On the other hand, when the content of graphite (conductivity auxiliary agent) 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, and the discharge capacity is reduced.
Further, from the viewpoint that the above-mentioned action is more remarkably obtained, the content of the conductive auxiliary agent made of graphite in the negative electrode 10 is more preferably in the range of 8 to 9 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 the negative electrode binder include polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), polyacrylic acid (PA), carboxymethyl cellulose (CMC), polyimide (PI), and polyimide amide (PAI). Among them, PA It is preferable to use acrylic polymers such as

The negative electrode binder may be used alone or in combination of two or more. When PA is used as the negative electrode binder, it is preferable to adjust the pH of 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 mass %.

The size and thickness of the negative electrode 20 are the same as the size and thickness of the positive electrode 10.

As a method for producing the negative electrode 20, for example, the above material is used as a negative electrode active material, and a negative electrode conductive additive and/or a negative electrode binder is mixed as necessary to prepare a negative electrode mixture, and this negative electrode mixture is prepared. A method of press-molding the agent into an arbitrary shape can be adopted.
The pressure at the time of pressure molding in this case is determined in consideration of the type of the negative electrode conductive additive, and can be, for example, 0.2 to 5 ton/cm ² .

Further, the negative electrode current collector 24 can be made of the same material as the positive electrode current collector 14.

(Separator)
The separator 30 is an insulating film that is interposed between the positive electrode 10 and the negative electrode 20, has a large ion permeability, is excellent in heat resistance, and has a predetermined mechanical strength.
As the separator 30, a separator that is conventionally used for a non-aqueous electrolyte secondary battery and that is made of a material satisfying the above characteristics can be applied without any limitation, and examples thereof include alkali glass, borosilicate glass, quartz glass, and lead glass. Glass, polypropylene (PP), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polyamide imide (PAI), polyamide, polyimide (PI), aramid, cellulose, fluororesin, ceramics, etc. Examples include non-woven fabrics and fibers made of resin. Among the above, as the separator 30, a separator made of a porous polymer material such as polypropylene (PP) resin can be used to obtain a separator having a large 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, and the like, and may be, for example, about 5 to 300 μm.

[Applications 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 preferably used for power supplies such as watches having various functions such as, and various small electronic devices.

[Effect]
As described above, according to the non-aqueous electrolyte secondary battery 1 of the embodiment of the present invention, lithium cobalt oxide is used as the positive electrode active material in the positive electrode 10, and lithium titanate is used as the negative electrode active material in the negative electrode 20, respectively. Further, the content of the conductive additive made of graphite contained in the negative electrode 20 is specified to be 7% by mass or more and less than 10% by mass. As a result, a sufficient capacity as a non-aqueous electrolyte secondary battery is ensured, and the current flow in the negative electrode 20 is improved, so that a sufficient discharge capacity can be obtained even with a small size and a large size. It becomes possible to supply electric current.

Next, examples of the present invention will be shown to explain the present invention more specifically. Note that the scope of the present invention is not limited by the present embodiment, and the non-aqueous electrolyte secondary battery according to the present invention can be appropriately modified and implemented within a range not changing the gist of the present invention. is there.

[Experimental Examples 1 to 6]
In Experimental Examples 1 to 6, coin-type non-aqueous electrolyte secondary batteries as shown in FIG. 1 were produced as non-aqueous electrolyte secondary batteries. In this example, lithium cobalt oxide (LiCoO ₂ ) was used as the positive electrode active material and lithium titanate (Li ₄ Ti ₅ O ₁₂ ) was used as the negative electrode active material, and the outer diameter was 6 in the cross-sectional view shown in FIG. A coin-type (621 size) non-aqueous electrolyte secondary battery (lithium secondary battery) having a thickness of 0.8 mm and a thickness of 2.1 mm was produced and the discharge characteristics were evaluated.

(Preparation of battery)
As the positive electrode 10, first, commercially available lithium cobalt oxide (LiCoO ₂ ) is used, graphite is used as a conduction aid, polytetrafluoroethylene (PTFE) is used as a binder, and lithium cobalt oxide:graphite:PTFE=93:6:1 (mass). The mixture was mixed at a ratio of (ratio) to obtain a positive electrode mixture.
Next, 35 mg of the obtained positive electrode mixture was pressure-molded with a pressure of ² ton/cm ² , and was pressure-molded into a disk-shaped pellet having a diameter of 4.0 mm.

Next, the obtained pellets (positive electrode 10) are adhered to the bottom surface 12c of the positive electrode can 12 made of stainless steel (NAS64:t=0.20 mm) using a conductive resin adhesive containing carbon, and these are adhered. The positive electrode unit was obtained by integrating. Then, this positive electrode unit was dried under reduced pressure in the air at 120° C. for 11 hours.
Then, the sealing agent was applied to the inner surface of the opening 12a of the positive electrode can 12 in the positive electrode unit.

Next, as the negative electrode 20, first, commercially available lithium titanate (Li ₄ Ti ₅ O ₁₂ ) was prepared as a negative electrode active material, and graphite was used as a conductive agent in this negative electrode active material, and an acrylic polymer (Wako Pure as a binder). HW105) manufactured by Yakuhin Kogyo Co., Ltd. was mixed to obtain a negative electrode mixture. At this time, the mixing ratios {lithium titanate:graphite:acrylic polymer} were {97:2:1} (graphite: 2%; Experimental Example 1) and {95:4:1} (mass ratios), respectively. Graphite: 4%; Experimental Example 2), {93:6:1} (Graphite: 6%; Experimental Example 3), {90:8:2} (Graphite: 8%; Experimental Example 4), {88:10 :2} (graphite: 10%; Experimental example 5) and {86:12:2} (graphite: 12%; Experimental example 6).
Then, each 26 mg of the obtained negative electrode mixture was pressure-molded with a pressing force of ² ton/cm ² , and was pressure-molded into a disk-shaped pellet having a diameter of 3.8 mm.

Next, each of the obtained pellets (negative electrode 20) was coated with a conductive resin adhesive containing carbon as a conductive filler on the inner surface of a negative electrode can 22 made of stainless steel (SUS304-BA: t=0.20 mm). It adhered using, and these were integrated and the negative electrode unit was obtained. Thereafter, this negative electrode unit was dried under reduced pressure in the atmosphere under the conditions of 160° C. for 11 hours.

As described above, in the present embodiment, the positive electrode current collector 14 and the negative electrode current collector 24 shown in FIG. 1 are not provided, and the positive electrode can 12 has the function of the positive electrode current collector and the negative electrode can 22 is provided. A non-aqueous electrolyte secondary battery was manufactured as a structure having a function of a negative electrode current collector.

Next, a nonwoven fabric made of polypropylene resin was punched into a disk shape having a diameter of 7 mm to form a separator 30. Then, this separator 30 was placed on the negative electrode 20, and a polypropylene gasket 40 was placed in the opening of the negative electrode can 22.

Next, an organic solvent was prepared according to the following blending ratio (volume %), and a supporting salt was dissolved in this organic solvent to prepare an electrolytic solution. At this time, as the organic solvent, propylene carbonate (PC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) are mixed in a volume ratio of {PC:EC:EMC}={1:1:3}. By doing so, the mixed solvent was adjusted. Moreover, lithium hexafluorophosphate (LiPF ₆ ) was used as a supporting salt to be dissolved in an organic solvent.
Then, the positive electrode can 12 and the negative electrode can 22 were filled with the electrolytic solution 50 prepared by the above procedure in a total amount of 40 μL per one battery.

Next, the negative electrode unit was crimped onto the positive electrode unit so that the separator 30 was in contact with the positive electrode 10. At this time, the caulking tip portion 12b in the opening 12a of the positive electrode can 12 is arranged more inward of the negative electrode can 22 than the tip portion 22a of the negative electrode can 22, and the side surface portion 12d of the positive electrode can 12 has the opening 12a. The caulking process was performed so that a curved surface was formed on the side.

Then, the positive electrode can 12 and the negative electrode can 22 are sealed by fitting the opening of the positive electrode can 12, and then allowed to stand at 25° C. for 7 days to obtain the non-aqueous electrolyte secondary batteries of Experimental Examples 1 to 6. It was made.

(Evaluation of discharge voltage and discharge current)
By performing a test as described below on the non-aqueous electrolyte secondary batteries of Experimental Examples 1 to 6 obtained by the above procedure, the discharge voltage after a predetermined time from the start of discharge and the start of discharge The time from when the voltage dropped to the predetermined voltage was examined and evaluated.
Specifically, first, the obtained non-aqueous electrolyte secondary battery was discharged at a constant current of 1 mA (discharge current) to a voltage of 1.5 V under an environment of 25° C., and then under an environment of 25° C. A voltage of 2.3 V was applied for 48 hours.

Then, under a low temperature environment of −10° C., the battery was discharged at a constant current of 1 mA (discharge current), and the discharge voltage (V) after 10 seconds was examined.
Separately from the above, under a low temperature environment of −10° C., discharge was performed at a constant current of 1 mA (discharge current), and the time until the discharge voltage (V) became 1.4 V and 1.2 V was examined.

Then, the above results are shown in Table 1 below, and the relationship between the graphite (conductivity aid) content in the negative electrode and each discharge voltage or discharge time is shown in the graphs of FIGS. Here, FIG. 2 is a graph showing the relationship between the graphite content in the negative electrode and the voltage 10 seconds after the start of discharge. FIG. 3 is a graph showing the relationship between the graphite content in the negative electrode and the time from the start of discharge until the voltage reaches 1.4V. FIG. 4 is a graph showing the relationship between the graphite content in the negative electrode and the time from the start of discharge until the voltage reaches 1.2V.

(Evaluation of discharge capacity)
The non-aqueous electrolyte secondary batteries of Experimental Examples 1 to 6 obtained by the above procedure were subjected to the following test to measure the capacity when discharged to a predetermined voltage.
Specifically, first, the non-aqueous electrolyte secondary battery was discharged to a voltage of 1.5 V, and then applied at a voltage of 2.3 V for 48 hours in an environment of 25°C.

Thereafter, with respect to the non-aqueous electrolyte secondary batteries of Experimental Examples 1 to 6, the capacity at the time of discharging at a constant current of 1 mA (discharge current) to a voltage of 1.5 V under a low temperature environment of −10° C. was measured. The values are shown in Table 2 below as the discharge capacity (mAh).

[Experimental Examples 7 to 14]
In Experimental Examples 7 to 14, as the positive electrode 10, a commercially available lithium cobalt oxide (LiCoO ₂ ) having an average particle size (D50) of 5.8 μm was used as the positive electrode active material, and the average particle size (D50) and the positive electrode activity were measured. A graphite material having a ratio of the average particle diameter (D50) to the substance and a specific surface area set to the values shown in Table 3 below was used as a conductive additive. Further, polytetrafluoroethylene (PTFE) was used as a binder and mixed at a ratio of lithium cobalt oxide:graphite:PTFE=90:8:2 (mass ratio) to prepare a positive electrode mixture, and a positive electrode 10 was produced.
In Experimental Example 7, since carbon nanotubes made of graphite and having a fiber diameter of 150 nm were used as the conductive additive contained in the positive electrode 10, the average particle size (D50) and the positive electrode active material in Table 3 below were used. In the column of the ratio of the average particle diameter (D50) of, the description is omitted.

Similarly to the above, commercially available lithium titanate (Li ₄ Ti ₅ O ₁₂ ) is used as the negative electrode 20 for the negative electrode active material, and graphite is used as the conductive agent and acrylic polymer (Wako Pure Chemical Industries, Ltd.) as the binder in the negative electrode active material. The thing using the negative electrode mixture which mixed Kogyo Co., Ltd. HW105) was prepared. At this time, the mixing ratio {lithium titanate:graphite:acrylic polymer} was set to {88:10:2} (graphite: 10%) in mass ratio to prepare the negative electrode 20.
Then, except for the above points, a coin type non-aqueous electrolyte secondary battery (lithium secondary battery) as shown in FIG. 1 was produced by the same procedure and conditions as in Experimental Examples 1 to 6.

Further, with respect to the non-aqueous electrolyte secondary batteries of Experimental Examples 7 to 14, similarly to the above, under a 25° C. environment, they were discharged to a voltage of 1.5 V at a constant current of 1 mA (discharge current), and then under a 25° C. environment. , And a voltage of 2.3 V was applied for 48 hours.
Then, under a low temperature environment of −10° C., the battery was discharged at a constant current of 3 mA (discharge current), and the discharge voltage (V) after 10 seconds was examined. The results are shown in Table 3 below.

[Evaluation results]
As shown in Table 1 and the graph of FIG. 2, in a non-aqueous electrolyte secondary battery using lithium cobalt oxide as the positive electrode active material in the positive electrode and lithium titanate as the negative electrode active material in the negative electrode, graphite contained in the negative electrode It can be seen that when the content of is 7% by mass or more, a sufficiently high voltage can be secured, that is, the discharge voltage 10 seconds after the start of discharge at a constant current of 1 mA (discharge current) is about 1.35 V or more. Further, as shown in Table 1 and the graphs of FIGS. 3 and 4, when the content of graphite contained in the negative electrode is 7% by mass or more, the discharge voltage due to discharge at a constant current of 1 mA (discharge current) is It takes about 10 seconds or more for the voltage to drop to 1.4V and about 20 seconds or more for the discharge voltage to drop to 1.2V, and it is possible to secure a predetermined discharge voltage for a long time from the start of discharge at a constant current. Recognize.

Further, as shown in Table 2, it is understood that when the content of graphite contained in the negative electrode is less than 10% by mass, the capacity retention rate after discharge is excellent and a large capacity can be secured.

Further, as shown in Table 3, in Experimental Examples 8 and 9 in which the average particle diameter (D50) of the conductive additive contained in the positive electrode 10 was smaller than the average particle diameter (D50) of the positive electrode active material, It was confirmed that the voltage drop after discharge was small as compared with Experimental Examples 10 to 14 in which the average particle diameter (D50) of the conductive additive was larger than the average particle diameter (D50) of the positive electrode active material.
Further, Experimental Examples 7 to 9 in which the specific surface area of the conductive auxiliary agent included in the positive electrode 10 is 13 m ² /g or more are compared with Experimental Examples 10 to 14 in which the specific surface area of the conductive auxiliary agent is less than 13 m ² /g. It was confirmed that the voltage drop after discharge was small.
Thereby, in the non-aqueous electrolyte secondary battery according to the present invention, particularly when the average particle diameter (D50) or the specific surface area of the conductive additive is limited to a specific range, heavy load characteristics, that is, large current It is clear that the discharge characteristics in 1 are further improved.

From the results of the examples described above, the content of graphite contained in the negative electrode in the non-aqueous electrolyte secondary battery using lithium cobalt oxide as the positive electrode active material in the positive electrode and lithium titanate as the negative electrode active material in the negative electrode, respectively. Is 7% by mass or more and less than 10% by mass, it is clear that sufficient discharge capacity can be obtained and a large current can be supplied.

According to the non-aqueous electrolyte secondary battery of the present invention, by adopting the above configuration, it is possible to obtain a sufficient discharge capacity and supply a large current even with a small size. Therefore, by applying the present invention to, for example, a watch having various functions such as an alarm, and a non-aqueous electrolyte secondary battery used in the fields of various small electronic devices, etc., it contributes to the performance improvement of various devices. It is possible.

1... Non-aqueous electrolyte secondary battery,
2... storage container,
10... Positive electrode,
12... Positive electrode can 12a... Opening,
12b... Caulking tip,
12c...bottom,
12d... Side part 14... Positive electrode current collector,
20... Negative electrode,
22... Negative electrode can,
22a... tip end,
24... Negative electrode current collector,
30...separator,
40... gasket,
41... annular groove,
50... Electrolyte

Claims (11)

A positive electrode, a negative electrode, an electrolytic solution containing a supporting salt and an organic solvent, and a separator, which is a non-aqueous electrolyte secondary battery housed in a housing container configured by a positive electrode can and a negative electrode can,
The positive electrode includes a positive electrode active material made of lithium cobalt oxide, a conductive auxiliary agent, and a binder,
The negative electrode includes a negative electrode active material made of lithium titanate, a conductive auxiliary agent made of graphite, and a binder,
The non-aqueous electrolyte secondary battery, wherein the negative electrode contains the conductive additive in an amount of 7% by mass or more and less than 10% by mass based on the total mass of the negative electrode. The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode contains the conductive additive in an amount of 8 to 9 mass% with respect to the total mass of the negative electrode. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the binder contained in the positive electrode is made of a fluororesin. The non-aqueous electrolyte secondary battery according to claim 3, wherein the binder contained in the positive electrode is made of polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE). The average particle diameter (D50) of the conductive additive contained in the positive electrode is smaller than the average particle diameter (D50) of the positive electrode active material, according to any one of claims 1 to 4. The non-aqueous electrolyte secondary battery described. The average particle size (D50) of the conductive additive contained in the positive electrode is 55 to 67% of the average particle size (D50) of the positive electrode active material. The non-aqueous electrolyte secondary battery described. Any non-aqueous electrolyte secondary battery according to one of claims 1 to 6 in which the specific surface area of the conductive additive included in the positive electrode is characterized in that it is a 13~425m 2 / ^g. In the electrolytic solution, the organic solvent contains 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. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 7, which is a mixed solvent of The mixing ratio of the propylene carbonate (PC), the ethylene carbonate (EC) and the ethyl methyl carbonate (EMC) of the organic solvent is {PC:EC:EMC}=1 to 5:1 to 5: by volume ratio. The non-aqueous electrolyte secondary battery according to claim 8, which is in a range of 6 to 12. The nonaqueous electrolyte secondary battery according to claim 1, wherein the supporting salt of the electrolytic solution is lithium hexafluorophosphate (LiPF ₆ ). The non-aqueous electrolyte secondary battery according to any one of claims 1 to 10, wherein the separator is made of polypropylene resin.

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