JPH0648755Y2 - Coin type non-aqueous electrolyte secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a coin-type non-aqueous electrolyte secondary battery.

[Outline of device]

The present invention relates to a coin type non-aqueous electrolyte secondary battery, and more particularly to a coin type non-aqueous electrolyte secondary battery having excellent heavy load discharge characteristics.

[Conventional technology]

A so-called non-aqueous electrolyte battery that uses a non-aqueous electrolyte as the electrolyte is a battery with low self-discharge and excellent storability, especially for electronic wrist watches and semiconductor memory backups that require continuous use for a long period of 5 to 10 years. It is widely used as a power source.

These non-aqueous electrolyte batteries conventionally used are usually primary batteries, but there is a strong demand for rechargeable non-aqueous electrolyte secondary batteries as a power source that can be repeatedly used economically for a long period of time. Research is progressing in various fields. Among them, as a negative electrode active material for negative electrode pellets, a coin type non-aqueous electrolyte secondary battery using a carbon material such as coke or organic polymer fired body that can be doped and dedoped with lithium ions has a high battery voltage. Since it can obtain high energy density, it is expected as a power source for small electronic devices. Less than,
The structure of a conventional coin type non-aqueous electrolyte secondary battery will be described with reference to FIG.

Second showing a cross-sectional view of a conventional coin-type non-aqueous electrolyte secondary battery
In the figure, reference numeral 2 denotes a negative electrode pellet, which is formed by molding a negative electrode active material made of a material such as a carbon material such as coke or organic polymer fired body that can be doped or dedoped with lithium ions. Reference numeral 3 denotes a positive electrode pellet, which is a transition metal oxide such as manganese dioxide or vanadium pentoxide, a complex compound of these oxides and lithium, a transition metal chalcogen compound such as iron fluke, or a chalcogen compound and lithium. The composite compound of and is used as a positive electrode active material, and this is molded.

The negative electrode pellet 2 and the positive electrode pellet 3 are sandwiched by a separator 4 made of a microporous film, and a negative electrode can 5
And it is stored in the positive electrode outer can 6. The positive electrode outer can 6 is caulked at its open end via a sealing gasket 7 to be sealed.

As the electrolytic solution, for example, a non-aqueous electrolytic solution in which a lithium salt is used as an electrolyte and this is dissolved in a non-aqueous solvent (organic solvent) is used.

In the conventional coin type non-aqueous electrolyte secondary battery configured as described above, a stainless steel plate is usually used as the material of the negative electrode can 5 from the viewpoint of cost and sealing performance.
Further, particularly when the deterioration of the operating voltage characteristic during heavy load discharge (hereinafter referred to as heavy load negative discharge characteristic) becomes a problem, at least the contact surface with the negative electrode pellet 2 inside the negative electrode can 5 is plated with gold to obtain a contact resistance value. Has been reduced (for example, JP-A-61-24143).

[Problems to be solved by the device]

In the conventional coin-type non-aqueous electrolyte secondary battery described above, since the stainless steel plate is used for the negative electrode can 5, the presence of the passive oxide film on the surface causes a large contact resistance value with the negative electrode pellet 2. Therefore, the heavy load discharge characteristics were poor.

Further, the method of applying gold plating to the inside of the negative electrode can 5 to improve the heavy load discharge characteristics has been difficult to apply to an actual product in terms of cost.

Therefore, an object of the present invention is to provide a coin-type non-aqueous electrolyte secondary battery using a carbon material capable of doping and dedoping lithium ions as a negative electrode active material for a negative electrode pellet, by a simple and inexpensive method, and under heavy load discharge characteristics. Another object of the present invention is to provide an improved coin type non-aqueous electrolyte secondary battery.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the coin-type non-aqueous electrolyte secondary battery according to the present invention includes a negative electrode pellet and a negative electrode can between the negative electrode pellet and the negative electrode can.
It is provided with a copper layer. The area of the copper layer may be smaller than the inner bottom area of the negative electrode can, and may be equal to or larger than the plane projection area of the negative electrode pellet on the inner bottom surface of the negative electrode can. The thickness of the copper layer is preferably 1 μm or more and 100 μm or less.

[Action]

Copper has a Young's modulus of 12.98 × 10 ¹⁰ N · m ^-2 and is a softer metal than stainless steel. Therefore, when the coin-shaped non-aqueous electrolyte secondary battery is assembled by caulking the open end of the positive electrode outer can, the copper layer exhibits excellent adhesiveness with the negative electrode pellet. Therefore, the contact resistance value between the negative electrode pellet and the negative electrode can is reduced, and as a result, the heavy load discharge characteristics are improved.

Further, the coin-type non-aqueous electrolyte secondary battery is charged at a voltage of 3.5 V or more, but under this condition, the copper layer can exist stably on the negative electrode side and is not corroded by the non-aqueous electrolyte. Absent. Moreover, since the copper layer is not corroded even if the charge / discharge cycle is repeated, good heavy load discharge characteristics are not deteriorated.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG. 1 is a sectional view showing a first embodiment of a coin type non-aqueous electrolyte secondary battery of the present invention. First, as the positive electrode active material,
Mix 1 mol of lithium carbonate and 1 mol of cobalt carbonate to 90
LiCoO ₂ was obtained by firing in air at 0 ° C. for 5 hours. This LiCoO
₂ 91 parts by weight, 6 parts by weight of graphite powder as conductive material, polytetrafluoroethylene (PTFE) as binder
The powder 3 parts by weight was mixed homogeneously, and the positive electrode pellet 3 having an outer diameter of 15.5 mm, a height of 0.51 mm and a weight of 0.346 g was produced by compression molding.

On the other hand, as the negative electrode active material, 90 parts by weight of pitch coke powder and 10 parts by weight of PTFE powder as a binder were added and mixed homogeneously, and this was also compression-molded to give an outer diameter of 15.5 mm and a height of 15.5 mm.
A negative electrode pellet 2 having a weight of 0.55 mm and a weight of 0.145 g was prepared.

This negative electrode pellet 2 is placed inside a negative electrode can 5 having a copper foil 1 having a thickness of 5 μm laid on the inner bottom surface, a separator 4 made of a microporous film is laid on the negative electrode can 5, and a plastic sealing gasket 7 is placed on the separator 4 It was put on the upper part through and the electrolyte solution was dripped from above.

Further, the positive electrode pallet 3 described above is placed on this, finally the positive electrode outer can 6 is placed on it, and the opening end is caulked and sealed, and a coin type non-aqueous electrolyte solution having an outer diameter of 20 mm and a height of 1.6 mm. A secondary battery was produced. This is referred to as sample battery 1.

The area of the copper foil 1 was made to coincide with the inner bottom area of the negative electrode can 5. As the electrolytic solution, a nonaqueous electrolytic solution prepared by dissolving LiPF ₆ at a ratio of 1 mol / l in a solvent obtained by mixing propylene carbonate and 1,2-dimethoxyethane at a volume ratio of 1: 1 was used. .

Example 2 Instead of the copper foil having a thickness of 5 μm used in Example 1, a thickness of 10 μm was used.
In order to adjust the height of the battery by using copper foil of μm, the height of the positive electrode pellet is 0.505mm, the weight is 0.343mm.
g, the height of the negative electrode pellet is 0.545 mm, the weight is 0.144 g,
A coin type non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except for the above. This is referred to as sample battery 2.

Example 3 Instead of the copper foil having a thickness of 5 μm used in Example 1, a thickness of 50 μm was used.
In order to adjust the height of the battery by using a copper foil of μm, the height of the positive electrode pellet is 0.485 mm, and the weight is 0.329.
g, the height of the negative electrode pellet is 0.525 mm, the weight is 0.139 g,
A coin type non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except for the above. This is referred to as a sample battery 3.

Example 4 Instead of the copper foil having a thickness of 5 μm used in Example 1, a thickness of 10 μm was used.
In order to adjust the height of the battery by using 0μm copper foil, the height of the positive electrode pellet is 0.460mm, the weight is 0.3mm.
A coin type non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the weight of the negative electrode pellet was 12 g, the height of the negative electrode pellet was 0.500 mm, and the weight was 0.132 g. This is referred to as a sample battery 4.

Comparative Example For comparison, a coin-type non-aqueous electrolyte secondary battery which does not use a copper foil, which is a conventional method, was also manufactured. The positive and negative electrode pellets used at this time were the same as in Example 1, and all were the same as in Example 1 except that no copper foil was used. This was designated as Sample Battery 11.

The sample batteries 1, 2, 3, 4 prepared as described above and
11. Then, the discharge capacity at the 10th cycle when the charge and discharge cycle was repeated 10 times by charging each with a current of 5.7mA and setting the upper limit voltage to 4.0V for 5 hours, and then discharging with a heavy load discharge current of 2.2mA. It was measured. The results are shown in FIG.

As is clear from FIG. 3, the sample batteries 1, 2 and 3 according to the embodiment of the present invention all have a larger discharge capacity and a heavier weight than the sample battery 11 according to the comparative example which does not use the copper foil, which is the conventional method. It can be seen that the load discharge characteristics are excellent. In addition, the sample battery 4 according to the example using the 100 μm thick copper foil has the discharge capacity almost equal to that of the sample battery 11 according to the comparative example because the height and weight of the positive electrode pellets are reduced to adjust the height of the battery. Became 100 μm
It can be said that it is not preferable to increase the thickness of the copper foil beyond that.

Although not described in the examples, the effect of improving the heavy load discharge characteristics is recognized for the copper foil having a thickness of 1 μm or more. However, a copper foil having a thickness of less than 5 μm has low mechanical strength, requires careful handling, and may be torn when the outer peripheral portion is cut.

Therefore, the thickness of the copper foil used in the present invention is 1 μm or more 10
It is preferably 0 μm or less, more preferably 5 μm or more 50
It can be seen that it is preferable that the thickness is less than μm.

As described above, in the present embodiment, the copper foil is described as an example of the copper layer, but in addition, a vacuum thin film forming technique such as copper vapor deposition or ion plating, or a method such as copper plating may be used to form the positive electrode outer can. A copper layer without pinholes may be provided on the inner bottom surface of the. A material obtained by clad copper on a stainless copper plate may be used as the negative electrode can. As the positive electrode active material, a mixture of LiCoO ₂ and graphite powder and PTFE powder was compression molded and used as the positive electrode pallet. Further, it is possible to use a complex compound of these oxides and a chalcogen compound and lithium. As the negative electrode active material, a mixture of pitch coke powder and PTFE powder was compression-molded and used as the negative electrode pellet, but other carbon materials capable of doping and dedoping lithium ions, that is, petroleum-based coke and coal-based coke, Coke material,
An organic polymer fired body obtained by firing an organic polymer in a non-oxidizing atmosphere at 500 ° C or higher, carbon blacks such as acetylene black, graphite, glassy carbon, activated carbon, carbon fiber, and other pyrolyzed carbons of organic substances Can be used as a source. The non-aqueous electrolyte may be, for example, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiC.
Li, LiBr, a lithium salt such as CH ₃ SO ₃ Li or CF ₃ SO ₃ Li is used as an electrolyte, and this is used, for example, as propylene carbonate,
Ethylene carbonate, 1,2-dimethoxyethane, 1,2-
Non-dissolved in a single or mixed organic solvent such as diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile or propionitrile. A water electrolyte can be used.

[Effect of device]

As described above in detail, according to the present invention, by providing a copper layer such as a copper foil between a negative electrode pellet and a negative electrode can, excellent heavy load discharge characteristics are achieved, and even after repeated charge and discharge cycles. It is possible to obtain a coin-type non-aqueous electrolyte secondary battery which has little deterioration in heavy load discharge characteristics and is highly durable.

As a result, the drawback of the conventional coin-type non-aqueous electrolyte secondary battery, the poor heavy load discharge characteristics, particularly the deterioration of the heavy load discharge characteristics when the charge / discharge cycle is repeated, can be performed by a simple and inexpensive method. Since it can be solved, the industrial utility value of the present invention is great.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a coin type non-aqueous electrolyte secondary battery of the present invention, FIG. 2 is a sectional view of a conventional coin type non-aqueous electrolyte secondary battery, and FIG. 3 is a copper foil. It is a figure which shows the relationship between thickness and discharge capacity. 1 ... Copper foil 2 ... Negative electrode pellet 3 ... Positive electrode pellet 4 ... Separator 5 ... Negative electrode can 6 ... Positive electrode outer can 7 ... Sealing gasket

Claims (1)

[Scope of utility model registration request] 1. A coin type non-aqueous electrolyte secondary battery using a carbon material capable of doping and dedoping lithium ions as a negative electrode active material for a negative electrode pellet, wherein a copper layer is provided between the negative electrode pellet and the negative electrode can. A coin-type non-aqueous electrolyte secondary battery comprising: