JP6693391B2 - Secondary battery inspection method - Google Patents

Description

  The present invention relates to an inspection method for a secondary battery, and more particularly to an inspection method including a self-discharge inspection step for a secondary battery.

In recent years, from the viewpoint of environmental protection and energy saving, a hybrid vehicle using an engine and a motor as a power source and an electric vehicle using a motor as a power source have been developed and commercialized. A secondary battery capable of repeatedly charging and discharging electricity is an essential technology as an energy source for this hybrid vehicle and electric vehicle.
Generally, as the secondary battery, a secondary battery such as a lithium secondary battery or a nickel secondary battery is used. Among them, the lithium secondary battery has a high operating voltage and is easy to obtain a high output. It is a promising battery and is becoming more and more important as a power source for hybrid vehicles and electric vehicles.
By the way, at the time of manufacturing a lithium secondary battery, in order to exclude an initially defective lithium secondary battery, an inspection for measuring a self-discharge amount of the lithium secondary battery is generally performed.

  As a prior art of such a secondary battery inspection method, there is a secondary battery inspection method and a secondary battery manufacturing method described in Patent Document 1. In the technique of the document, initial charge / discharge is performed on the lithium ion battery (step S11). Next, high temperature aging is performed on the cell. For example, the cell is charged to a high voltage and then kept in an environment of 60 ° C. for 20 hours. As a result, the cell can be stabilized and the initial deterioration can be generated. Moreover, when a metal foreign substance is mixed, the cell can be short-circuited.

  Next, self-discharge of the cell is performed (step S13). For example, the cell is kept under an environment of 20 ° C. for 5 days, and the voltage drop due to self-discharge of the cell is measured. Then, the quality judgment is performed based on the measured voltage drop amount. Even if the short-circuited cell is not energized, the self-discharge amount increases, and the voltage drops. Therefore, a cell whose voltage drop amount is larger than the threshold value is determined as a short-circuit cell. In this way, it was determined whether or not the secondary battery was short-circuited. (In particular, [0021] to [0022] of the same document, FIG. 1).

JP, 2013-84508, A

However, the above-mentioned conventional technique has the following problems. That is, after the initial charging / discharging in step S11, the cells are charged to a high voltage. At this time, if a large number of cells are arranged in a module and high-speed charging is performed with a large current, the cells are placed at different positions in the module. After the end of charging due to the variation in cell temperature, the terminal voltage varied after a lapse of a predetermined time, and as a result, the voltage drop amount due to self-discharge later also varied.
Specifically, as shown in FIG. 5, when high-speed charging is performed with a large current, the amount of heat generated by the cells increases, and as a result, the cells located on the outside where heat is easily dissipated in the jig and the center where heat is easily accumulated. There is a temperature difference with the cell located at. When this module is left under a constant temperature for a predetermined time, as shown in FIG. 6, the cell located in the center has a lower terminal voltage after charging than the cell located outside the jig, As a result, as shown in FIG. 7, the self-discharge amount ΔV also fluctuates due to the fluctuation of the terminal voltage after the end of charging, and therefore, the determination accuracy of the self-discharge amount inspection may decrease. Further, in order to improve the accuracy, it is necessary to spend time on the inspection, which causes a problem that the inspection time becomes long.

  The present invention has been made to solve the problems of the above-described conventional techniques. That is, it is an object of the invention to provide a method for inspecting a secondary battery that can perform a self-discharge inspection with high accuracy and in a short time.

In order to solve the above problems, the method for inspecting a secondary battery of the present invention has the following configuration.
(1) A secondary battery inspection method comprising a self-discharge inspection step of inspecting a self-discharge amount of the secondary battery after an initial charging step of charging the secondary battery, wherein the initial charging step is performed at a predetermined voltage. Up to a charging step of charging a plurality of secondary batteries, after the charging step, a temperature measuring step of measuring a temperature variation between the plurality of secondary batteries, and a temperature variation measured in the temperature measuring step. Based on the experimentally obtained in advance, referring to the relationship between the variation of the temperature and the allowable final voltage of the initial charging step, a final voltage determining step of determining the final voltage of the initial charging step, and until determined the final voltage, again, characterized in that it consists of, a recharging step of charging the plurality of secondary batteries.

The operation and effect of the secondary battery inspection method of the present invention having the above configuration will be described.
(1) A secondary battery inspection method comprising a self-discharge inspection step of inspecting a self-discharge amount of the secondary battery after an initial charging step of charging the secondary battery, wherein the initial charging step is performed at a predetermined voltage. Up to a charging step of charging a plurality of secondary batteries, after the charging step, a temperature measuring step of measuring a temperature variation between the plurality of secondary batteries, and a temperature variation measured in the temperature measuring step. Based on the experimentally obtained in advance, referring to the relationship between the variation of the temperature and the allowable final voltage of the initial charging step, a final voltage determining step of determining the final voltage of the initial charging step, and And a recharging step of charging the plurality of secondary batteries again up to the determined final voltage , so that the self-discharge test can be accurately performed in a short time.

FIG. 4 is a process diagram schematically showing a method for inspecting a secondary battery of the present invention. It is a process diagram which shows the detail of an initial charging process. It is a figure which shows for each environmental temperature about the terminal voltage in temperature 25 degreeC, and the change of the terminal voltage from the terminal voltage in temperature 25 degreeC when leaving a lithium ion battery under each environmental temperature of 10 degreeC-35 degreeC. . It is a figure which shows the relationship between temperature difference (DELTA) T and the permissible final voltage. It is a figure which shows the temperature of each lithium ion battery before charge and after charge. It is a figure showing the terminal voltage of each lithium-ion battery after a lapse of a predetermined time. It is a figure which shows the relationship between the terminal voltage after charge and the self-discharge amount.

(Embodiment 1)
Hereinafter, a method for inspecting a secondary battery of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a process diagram schematically showing a method for inspecting a secondary battery of the present invention.
In the figure, an inspection step 10 for implementing the inspection method for a secondary battery includes an initial charging step 11, a high temperature aging step 12, a self-discharge inspection step 13, a voltage adjustment step 14, and a shipping inspection step 15.
In the initial charging step 11, a lithium ion battery (not shown) is initially charged. In the initial charging step 11, a plurality of lithium ion batteries are arranged in the jig and simultaneously charged at high speed with a high current. The details of the initial charging step 11 will be described later.

  In the high temperature aging step 12, the lithium ion battery whose initial charging is completed in the initial charging step 11 is held for a predetermined time in a high temperature environment. As a result, the lithium-ion battery can be stabilized and the initial deterioration can be generated. Further, when a metallic foreign matter is mixed, the lithium ion battery can be short-circuited.

  In the self-discharge inspection step 13, the terminal voltage of the lithium-ion battery after the high temperature aging step 12 is measured, and the lithium-ion battery is measured based on the measured self-discharge amount ΔV (voltage decrease amount of the terminal voltage) of the lithium-ion battery. The quality of the battery is determined.

  In the voltage adjustment step 14, the terminal voltage of the lithium ion battery is adjusted again, and then various inspections are performed in the shipping inspection step 15, and a plurality of lithium ion batteries that have passed these inspections are combined. Installed in vehicles and used as an energy source.

FIG. 2 is a process diagram showing details of the initial charging process.
That is, the initial charging step 11 includes an initial charging step 111, a temperature measuring step 112, a final voltage determining step 113, and a recharging step 114.
In the initial charging step 111, the lithium ion battery is initially charged, a plurality of lithium ion batteries are arranged in the jig, and at the same time, high speed charging with a high current is performed. Then, when the terminal voltage of the lithium-ion battery reaches 3.7 V, for example, the initial charging step 111 ends. In the present embodiment, the terminal voltage at which the initial charging step 111 ends is set to 3.7V, but the present invention is not limited to this, and an appropriate voltage of 3.8V or less may be set. it can.

  In the temperature measurement step 112, the temperatures of the plurality of lithium ion batteries arranged in the jig are measured, and the difference temperature between the highest temperature and the lowest temperature of the measured lithium ion batteries is measured. , The temperature difference ΔT is obtained for a plurality of the lithium ion batteries. This temperature difference ΔT corresponds to the temperature variation of the present invention.

In the final voltage determining step 113, based on the temperature difference ΔT obtained in the temperature measuring step 112, the final voltage (final charging voltage) of the lithium ion battery in the initial charging step 11 is referred to with reference to FIG. A plurality of lithium ion batteries is determined.
FIG. 3 shows the terminal voltage at a temperature of 25 ° C. and the change in the terminal voltage from the terminal voltage at a temperature of 25 ° C. for each environmental temperature when the lithium ion battery is left under each environmental temperature of 10 ° C. to 35 ° C. FIG.
According to FIG. 3, the higher the terminal voltage of the lithium-ion battery at the temperature of 25 ° C., the less the influence of the environmental temperature on the lithium-ion battery (the change of the terminal voltage from the terminal voltage of the lithium-ion battery at the temperature of 25 ° C. is small. ), And what was experimentally obtained based on this is the relationship between the temperature difference ΔT and the allowable end voltage shown in FIG.

That is, in the initial charging step 11, it is necessary to charge up to 3.8 V as a final voltage in order to dissolve foreign matters in the next high temperature aging step 12.
In this case, based on FIG. 4, 3.8 V (or a voltage higher than that) is determined as the final voltage up to the temperature difference ΔT6 ° C. Further, when the temperature difference ΔT obtained in the temperature measuring step 112 is, for example, 8 ° C., 3.9 V (or a voltage higher than that) is determined as the final voltage based on FIG. In this way, based on the temperature difference ΔT obtained in the temperature measurement step 112, the final voltage corresponding to the temperature difference ΔT of 3.8 V or more is determined as the final charging voltage.

  In the recharging step 114, the plurality of lithium ion batteries are recharged to the final voltage based on the final voltage determined in the final voltage determining step 113. As described above, in the present embodiment, since the plurality of lithium ion batteries are each charged to the final voltage determined based on the temperature difference ΔT obtained in the temperature measurement step 112, the terminal voltage of the lithium ion battery is charged. Therefore, the variation in the self-discharge amount due to the variation can be reduced. Therefore, in the self-discharge inspection step 13, the quality of the lithium ion battery can be accurately determined in a short time.

  The above-described present embodiment is merely an example and does not limit the present invention. Therefore, the present invention is naturally capable of various improvements and modifications without departing from the scope of the invention. For example, in the present embodiment, in the final voltage determination step 113, the final voltage is determined based on FIG. 4, but the final voltage is not limited to this. For example, the final voltage of the lithium ion battery is determined based on the characteristics shown in FIG. The final voltage may be calculated after the temperature sensitivity is calculated. Further, if the temperature difference ΔT obtained in the temperature measuring step 112 is out of the allowable range, a fan for cooling the lithium ion battery may be provided to cool the high temperature lithium ion battery. .. Furthermore, in the present embodiment, in the temperature measuring step 112, the temperature difference ΔT of each lithium ion battery is obtained by measuring the temperature of all the lithium ion batteries, but the present invention is not limited to this. Instead, for example, the lithium-ion battery is divided into a plurality of areas, the temperature of one or a plurality of lithium-ion batteries is measured for each area, the temperature difference ΔT is determined, and the final voltage is determined. The lithium ion battery may be recharged on the basis of the final voltage determined in the above.

10 Inspection Step 11 Initial Charge Step 111 Initial Charge Step 112 Temperature Measurement Step 113 Final Voltage Determination Step 114 Recharge Step 12 High Temperature Aging Step 13 Self-Discharge Inspection Step 14 Voltage Adjustment Step 15 Shipping Inspection Step

Claims (1)

After the initial charging step of charging the secondary battery, a secondary battery inspection method comprising a self-discharge inspection step of inspecting the self-discharge amount of the secondary battery,
The initial charging step is
A charging step of charging a plurality of secondary batteries to a predetermined voltage,
After the charging step, a temperature measuring step of measuring temperature variations among the plurality of secondary batteries,
Based on the variation of the temperature measured in the temperature measurement step, the initial charging is performed with reference to the relation between the variation of the temperature and the allowable final voltage of the initial charging step, which is experimentally obtained in advance. A final voltage determining step of determining a final voltage of the process,
Until determined the final voltage, again, a recharging step of charging the plurality of secondary batteries,
A method for inspecting a secondary battery, comprising:

Images