JP2000260482A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a defective circuit voltage in a shipment inspection so as to improve battery quality by connecting all the batteries in the corresponding lot in parallel after initial charging for matching open circuit voltages with each other. SOLUTION: A negative electrode using carbon applied to a copper foil as a negative electrode active material and a positive electrode using lithium cobaltate as a positive electrode active material are wounded several times via a separator into a roll-shaped group of components. Constant current charging is finished when a battery voltage reaches 4.1 V. Subsequently, all the batteries in the same production lot are connected in parallel so as to be left standing, and the battery voltage match each other. After again is carried out further, an open circuit voltage inspection is carried out and only a secondary battery with a defective open circuit voltage is rejected. In this way, variation of an open circuit voltage is reduced, and a secondary battery causing minor internal short circuit can be easily selected so as to be removed. Alternatively, matching of voltage may be carried out by performing parallel connection in aging or after aging.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a secondary battery.

[0002]

2. Description of the Related Art In general, a secondary battery is manufactured by inserting a component group consisting of a positive electrode, a negative electrode, and a separator into a battery case, injecting an electrolytic solution, and closing the opening with a sealing lid or the like. The secondary battery is charged with a constant current to complete the charging when it reaches a certain voltage, or is charged at a constant voltage when the secondary battery reaches a certain voltage. Charging is completed by charging (CVCC). After that, to stabilize the quality of the rechargeable battery, it is aged for a certain period under certain conditions, and after the final inspection,
Shipped as a product. Also, after connecting at least two or more rechargeable batteries in parallel, hold and charge at a constant voltage, then connect in series, discharge at a constant current for a fixed time,
A technique of discharging a constant current to a constant voltage for each individual battery is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-74492.

[0003]

However, in the above-described initial charging, a part of the electrode plate inside the secondary battery is not charged uniformly, or the ambient temperature of the charged battery varies depending on each battery. Due to variations in the accuracy of the charging equipment and the like, the variation in the open circuit voltage immediately after the completion of the initial charging is large, and the state is maintained and expanded even after the aging is completed. Furthermore, during aging, if metal impurities or the like in the positive electrode exist, they become metal ions on the positive electrode and elute into the electrolytic solution, become metal on the negative electrode and precipitate in dendrite form, And a small internal short circuit may occur. In such a secondary battery, if the voltage before the occurrence of a micro short-circuit is distributed in a direction having a higher variation, it is difficult to eliminate defective products at the time of the final inspection, and to improve quality. Was an obstacle.

An object of the present invention is to improve the quality of a secondary battery in an initial charging step of the secondary battery in order to cope with such a problem.

[0005]

In order to solve the above-mentioned problems, the present invention is characterized in that after the initial charging is completed, all the lots are connected in parallel so that the open circuit voltages of the whole lots are equalized. By using the present invention, it is easy to select an open circuit voltage defect in a shipping inspection, and the quality of a battery is improved.

[0006]

Embodiments of the present invention will be described below.

As shown in FIG. 1, a negative electrode formed by coating carbon foil as a negative electrode active material with carbon and a positive electrode using lithium cobalt oxide as a positive electrode active material are spirally wound a plurality of times with a separator interposed therebetween. This is referred to as a winding configuration group 1. Then, the component group 1 is inserted into a battery case 2 made of a nickel-plated steel plate, the negative electrode lead 3 is connected to the inner bottom of the battery case 2, and the positive electrode lead 4 is connected to the sealing lid 5. Next, an electrolyte is injected, and the opening of the battery case 2 is sealed with the sealing lid 5. 6
Denotes an upper insulating plate of the constituent group 1, and 7 denotes a lower insulating plate of the constituent group 1. A groove 8 is provided near the opening of the battery case 2, and the sealing lid 5 is placed in the groove 8, and the opening of the battery case 2 is swaged.

Next, the battery is charged with a constant current and the battery voltage is 4.1 V
The charging is completed at the stage when the value reaches. After that, all the batteries of the same production lot are connected in parallel and left to keep the battery voltage constant. Further, after aging, an open-circuit voltage test is performed, and only the secondary battery having a bad open-circuit voltage is excluded. As a specific example of the cylindrical lithium secondary battery of the present embodiment, the diameter of the battery case 2 is 17.9 m.
m, the inner diameter of the groove 8 is 15.0 mm, when open, 5.0 mm from the groove to the battery opening end, 63.2 mm from the battery case bottom to the battery opening end, and the outer diameter of the component group is 1 mm.
The length is 7.0 mm and the length is 58.2 mm.

Here, as the cylindrical lithium ion secondary battery, a secondary battery was manufactured using the one shown in FIG.
Initial charging was performed by the charging method shown in Table 1, and then aging was performed at normal temperature and normal humidity for one month to obtain a conventional secondary battery. Initial charging was performed in the same manner as the conventional secondary battery, and a secondary battery connected in parallel for 1 hour after the initial charging was designated as secondary battery A. Further, a secondary battery in which the voltage adjustment by the parallel connection was performed for one hour during the aging period without performing the voltage adjustment by the parallel connection after the initial charging was designated as a secondary battery B. Further, unlike the secondary battery B, a secondary battery C in which voltage adjustment by parallel connection was performed for one hour after aging was completed was designated as a secondary battery C.

[0010]

[Table 1]

Each of the conventional secondary batteries and the secondary batteries A, B and C according to the embodiments of the present invention has a variation (σ) in the number of test batteries and the average value of the open circuit voltage. Are shown in Tables 2, 3, 4 and 5, respectively.

[0012]

[Table 2]

[0013]

[Table 3]

[0014]

[Table 4]

[0015]

[Table 5]

According to the results shown in Tables 2 and 3, after the initial charge, all the secondary batteries of the corresponding lot are connected in parallel, so that the open-circuit voltage, which has been varied, is leveled. It can be seen that the variation is small. Also,
After aging is completed, set the inspection standard with the average value ± 3σ,
Non-defective products in the range were stored for one month at room temperature and normal humidity, and an inspection standard was set again with an average value of ± 3σ to perform an open circuit voltage inspection. Table 2 and Table 3 show the results.
As shown in FIG. 1, 1% of the defects were detected in the conventional secondary battery, and it was found that the defects were not completely detected in the inspection after aging. On the other hand, no defect was detected in the secondary battery A according to the present invention, and it was found that the defect could be discharged by the inspection after aging.

Further, as shown in Tables 4 and 5, it has been found that the same result can be obtained even when the parallel connection is performed and the voltage is adjusted during the aging period or after the aging period is completed.

When the above study was conducted on other secondary battery systems, it was found that similar effects could be obtained.

[0019]

As is apparent from the above description, according to the present invention, it is possible to reduce the variation of the open circuit voltage and to easily select and remove a secondary battery having a small internal short circuit. Therefore, a highly reliable secondary battery with stable quality can be supplied.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a cylindrical lithium ion secondary battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Constituent group 2 Battery case 3 Negative electrode lead 4 Positive electrode lead 5 Sealing lid 6 Upper insulating plate 7 Lower insulating plate 8 Groove

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Okada 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A rechargeable battery characterized in that all the lots are connected in parallel after the initial charge so that the open circuit voltages are uniform.