JP2015125977A - Method for charging/discharging secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress temperature rising during charging/discharging, in a method for charging/discharging secondary battery bringing a probe pin in contact with an electrode terminal.SOLUTION: In a method for charging/discharging a secondary battery of the present invention, a probe pin is brought into contact with an electrode of a battery, pulse conduction 47 is caused between the electrode and the probe pin, and charging/discharging 52 of the battery is performed after pulse conduction 47. Contact resistance between the probe pin and the electrode is reduced by pulse conduction 47. As a result, temperature rising during charging/discharging 52 can be suppressed. Charging/discharging 52 is preferably performed while the probe pin is pressed to the electrode with a larger load than a load during pulse conduction 47.

Description

  The present invention relates to a method for manufacturing a secondary battery, and more particularly to a charge / discharge method.

  A battery charging / discharging method is known in which charging / discharging is performed by bringing a contact portion of a contact means into contact with an electrode of a battery (Patent Document 1). The method of Patent Document 1 is characterized in that a film or dust on the electrode surface is removed by a configuration in which the contact portion is pressed against the electrode and the contact portion is slid with respect to the electrode.

JP 2003-151644 A

  As another aspect of the charging / discharging method, there is a method of charging / discharging by contacting a probe pin with each of a positive electrode and a negative electrode terminal of a secondary battery as a contact means for passing an electric current. As shown in FIG. 1, the secondary battery is charged and discharged by bringing the pin 20 into contact with the battery electrode 25 on one of the positive and negative terminals.

  In FIG. 1, when the current 40 flowing through the pin 20 increases (current levels 41-43, see FIG. 2), a large amount of heat is generated in the contact resistance R between the electrode 25 and the pin 20 from the charge / discharge start point 49.

  The objective of this invention is suppressing the temperature rise at the time of charging / discharging in the charging / discharging method of the secondary battery which makes a probe pin and an electrode terminal contact.

  In the secondary battery charging / discharging method of the present invention, the probe pin is brought into contact with the electrode of the battery, pulse energization is performed between the electrode and the probe pin, and the battery is charged / discharged after the pulse energization. The contact resistance between the probe pin and the electrode is reduced by the pulse energization. For this reason, the temperature rise at the time of charging / discharging can be suppressed.

  In the charging / discharging method of the secondary battery in which the probe pin and the electrode terminal are brought into contact with each other, the temperature rise during charging / discharging can be suppressed.

It is a schematic diagram showing the contact of an electrode and a probe pin. It is a graph showing the relationship between an electric current, heat_generation | fever, and time. It is a graph which shows the charging / discharging method concerning embodiment. It is a graph showing the relationship between the temperature of the probe pin concerning embodiment, and the reciprocal number of Young's modulus. It is an enlarged view of the contact part before the pulse electricity supply concerning embodiment. It is an enlarged view of a contact part after pulse energization concerning an embodiment. It is a graph showing the relationship between the electric current concerning a comparative example, heat_generation | fever, and time. It is a graph showing the relationship between the contact resistance concerning a comparative example, and a load. It is a graph showing the relationship between the contact resistance concerning an Example, and the frequency | count of charging / discharging. It is a photograph showing the tip shape of the probe pin before pulse energization. It is a photograph showing the tip shape of the probe pin after charge and discharge in an example. It is a graph showing the relationship between the contact resistance concerning a comparative example, and the frequency | count of charging / discharging. It is a photograph showing the tip shape of the probe pin after charge and discharge in a comparative example. It is a graph showing the contact resistance concerning an Example and a comparative example.

  Hereinafter, embodiments and examples will be described with reference to the drawings. In all the drawings, equivalent components are denoted by the same reference numerals, and description thereof will be omitted as appropriate. FIG. 1 shows a state in which a current 40 for energization, pulse energization, or charge / discharge flows due to contact between an electrode 25 that is a positive electrode terminal or a negative electrode terminal of a secondary battery and a pin 20 that is a probe pin.

  As shown in FIG. 1, the energization or the pulse energization may be such that the current 40 flows from the pin 20 toward the electrode 25, or may flow in the direction opposite to the current 40. The tip of the pin 20 is a contact portion 21. The contact portion 21 side of the pin 20 has a tapered shape. Such a tapered shape acts as a concentrated resistance Rc when the current 40 flows.

  As shown in FIG. 1, the pin 20 can come into contact with the coating 26 on the surface 27 side of the electrode 25 through the contact portion 21. The film 26 is an oxide film generated from the surface of the terminal metal portion 24. The film 26 has a film resistance Rf. The terminal metal part 24 is a main body of the electrode 25 and is electrically connected to a current collector of the secondary battery (not shown). A current 37 flowing through the electrode 25 is a current continuing from the current 40.

As shown in FIG. 1, the contact resistance R is generated in the contact area between the electrode 25 and the pin 20. As shown in the following formula (1), the contact resistance R is a resistance including the concentrated resistance Rc and the film resistance Rf described above.

R = Rc + Rf (1)

The concentrated resistance Rc is an electrical resistance represented by the following formula (2). ρ is a specific electrical resistance of the contact portion 21. a is the radius of the contact area S between the contact portion 21 and the surface 27. n is the number of contact surfaces between the contact portion 21 and the surface 27. The number of contact surfaces is the number of contacts between the contact portion 21 and the film 26 in FIG.

Rc = ρ / (2 · a · n) (2)

The film resistance Rf is an electric resistance represented by the following formula (3). ρf is the resistivity of the film 26. d is the thickness of the coating 26. a is as described above.

Rf = (ρf · d) / (π · a ² ) (3)

  In FIG. 1, the charge / discharge and current directions are as follows. As shown in FIG. 1, the current 40 flows from the electrode 25 toward the pin 20. If the electrode 25 is a positive electrode, FIG. 1 represents the charging of the battery. In the case of battery discharge, current flows from the electrode 25 toward the pin 20 at the positive electrode. If the electrode 25 is a negative electrode, FIG. 1 represents the discharge of the battery. In the case of charging the battery, current flows from the electrode 25 toward the pin 20 at the negative electrode.

  In this embodiment, pulse energization is performed between the electrode 25 and the pin 20, and the battery is charged and discharged after the pulse energization. The contact resistance between the pin 20 and the electrode 25 is reduced by pulse energization. For this reason, the temperature rise at the time of charging / discharging can be suppressed.

  The graph of FIG. 2 represents a general relationship between current, heat generation, and time. In the graph of FIG. 2, the current level 41 is 10 times the current level 44, the current level 42 is 3 times, and the current level 43 is twice the current value.

  When the current value of the current 40 flowing through the pin 20 shown in FIG. 1 increases (current level 41-43), heat generation at the contact resistance R (FIG. 1) increases. When the contact resistance R (generates heat, the battery may be adversely affected, or the coated wire of the wiring connected to the battery may be melted.

  The graph of FIG. 3 shows the charge / discharge method of this embodiment. In this embodiment, pulse energization 47 is performed. The current value curve 45 shows the time change of the current value on the left vertical axis. The load curve 55 shows the time change of the load on the right vertical axis.

  At time 0 shown in FIG. 3, a load 56 necessary for the contact between the pin 20 and the electrode 25 in FIG. Next, at the pulse start point 46, the current value of the current 40 is set to the pulse current value 50, and pulse energization 47 is performed. The pulse energization 47 ends at a pulse end point 48. During the energization of the pulse, the pulse current value 50 may be kept constant.

  Next, as shown in FIG. 3, at the pressurization start point 57, the pin 20 in FIG. 1 is pressed against the electrode 25 with the load 58. The load 58 is also a load at the time of subsequent charge / discharge 52. The load 58 is preferably larger than the load 56 at the time of pulse energization 47. In other words, it is preferable to perform charge / discharge 52 by increasing the load 56 applied between the pin 20 and the electrode 25 to the load 58 after the pulse energization 47.

  In this manner, after the pulse end point 48 and before the charge / discharge start point 49, the surface of the electrode 25 is slid without sliding on the contact portion 21 at a pressurization start point 57 without increasing the load. The coating 26 on the 27 side can be removed or pushed away (see FIG. 1).

  The load 58 is preferably 4 times or less of the load 56, more preferably 1.4 times or less. According to this aspect, the wear of the pin 20 can be suppressed.

  Next, at the charge / discharge start point 49, the charge / discharge 52 is started by causing the current 40 to flow at the charge / discharge current value 51. The pulse current value 50 is preferably larger than the charge / discharge current value 51. For convenience, the charge / discharge current value 51 is shown in the same direction as the pulse current value 50 in the graph. The directions of the currents may be opposite to each other.

  For example, it is assumed that the pulse current value 50 is the current 40 (FIG. 1) that flows from the pin 20 toward the electrode 25. On the other hand, the charge / discharge current value 51 may be a current flowing from the electrode 25 toward the pin 20 in the opposite direction to the current 40 (see FIG. 1). The current 40 is assumed to be a current that flows in the opposite direction from the electrode 25 toward the pin 20. On the other hand, the charge / discharge current value 51 may be a current 40 flowing from the pin 20 toward the electrode 25 (see FIG. 1).

  As shown in FIG. 3, the time required for the pulse energization 47 is preferably shorter than the time required for charging / discharging after the charging / discharging start point 49. This is because the pulse energization 47 causes a temperature rise in the contact resistance R (FIG. 1) when the pulse energization 47 takes a long time.

  As shown in FIG. 3, in this embodiment, every time a desired charge / discharge is performed, pulse energization 47 is performed once, and then a load is applied to the pin 20 (FIG. 1) at the pressurization start point 57. Therefore, the resistance value of the contact resistance R (FIG. 1) between the pin 20 and the electrode 25 is suppressed, and heat generation (FIG. 2) is suppressed.

  In addition, the pulse energization 47 (FIG. 3) reduces the Young's modulus of the surface 27 (FIG. 1) of the electrode 25 and makes the surface 27 soft. For this reason, the contact area S of the contact part 21 (FIG. 1) and the surface 27 increases.

The contact area S is an area represented by the following formula (4). F represents the load applied to the pin 20 at the time of charging / discharging.

S = [(3 · F / 4) · {(1−ν ₁ ² ) / E ₁ + ((1−ν ₂ ² ) / E ₂ )}
/ {(1 / R ₁ ) + (1 / R ₂ )}] ^2/3 (4)

In the formula (4), the load F is the magnitude of the load 56 in the pulse energization 47 (FIG. 3).

The Poisson ratio ν ₁ is the Poisson ratio of the contact portion 21 in FIG. The Poisson ratio ν ₂ is the Poisson ratio of the film 26 in FIG. The Young's modulus E ₁ is the Young's modulus of the contact portion 21 in FIG. Young's modulus E ₂ is the Young's modulus of the film 26 in FIG. 1. R ₁ is the length of the radius of the contact surface when the contact surface 21 in FIG. 1 is assumed to be a circle. R ₂ is the length of the radius of the contact surface when the contact surface 26 in FIG. 1 is assumed to be a circle.

From the above formulas (1) to (4), it can be seen that it is effective to increase the number n of contact surfaces of the above formula (2) as a condition for suppressing the contact resistance R. It can also be seen that Young's modulus E ₁ and E ₂ , that is, a small Young's modulus and a large load F are necessary to satisfy such conditions. Therefore, it is effective to generate heat by pulse energization as a method of reducing the Young's modulus of the contact portion 21 or the surface 27 (FIG. 1) as in this embodiment.

  Further, as shown in FIG. 3, pulse energization 47 is performed, and charge / discharge is started in a state where the contact area S is increased (charge / discharge start point 49), so that the current 40 is concentrated in the concentrated resistance Rc (FIG. 1). Can also be suppressed. For this reason, the resistance value of the contact resistance R (FIG. 1) is reduced.

  The effect | action which the charge method of this embodiment suppresses the heat_generation | fever of a secondary battery is further considered using the graph of FIG. Such a graph represents the relationship between the temperature of the pin 20 (FIG. 1) shown in FIG. 1 and the reciprocal of the Young's modulus of the pin 20. That is, the temperature increases as the Young's modulus increases. On the other hand, as described above, an increase in temperature can be suppressed by a decrease in Young's modulus. It is considered that this is because the decrease in Young's modulus is to reduce the resistance value of the contact resistance R (FIG. 1).

  FIG. 5 is an enlarged view of the contact portion 21 (FIG. 1) before the pulse start point 46 (FIG. 3). As described above, the pulse energization 47 (FIG. 3) is performed while applying the load 56 (FIG. 3) between the pin 20 and the electrode 25 (FIG. 1). The surface of the contact portion 21 and the surface 27 of the coating 26 (FIG. 1) are more undulating than those after pulse energization (FIG. 6).

  FIG. 6 is an enlarged view of the contact portion 21 (FIG. 1) after the pulse energization 47 (FIG. 3). The surface of the contact portion 21 and the surface 27 (FIG. 1) are less undulated than those before the pulse energization (FIG. 5). Such a state is opposite to the increase in the number n of the contact surfaces described above.

  On the other hand, in the configuration described in Patent Document 1, the electrode is worn by sliding the contact portion 21. On the other hand, in the method of this embodiment, since sliding is not essential, the electrode 25 is hardly worn.

  As shown in FIG. 1, in the example and the comparative example, the pin 20 was pressed against the electrode 25 and brought into contact. In the example, as in the embodiment, as shown in FIG. 3, the pulse energization 47 was performed before the pressurization start point 57 was reached. In each Example, the load 56 (FIG. 3) at the time of pulse energization (pulse energization 47, FIG. 3) was 500 g (Table 1).

  As shown in Table 1, in Examples 1 to 3, the current value of the pulse current (pulse current value 50, FIG. 3) was set to 10 to 30A. The pulse time from the pulse start point 46 to the pulse end point 48 (FIG. 3) was 1 second. As shown below, the pulse time was 1 to 20 seconds in each Example (Table 1).

  As shown in Table 1, Examples 4 and 5 were the same as Example 2 except that the pulse times were 10 and 20 seconds, respectively. As shown in Table 1, Examples 4 and 5 were the same as Example 2 except that the pulse times were 10 and 20 seconds, respectively.

  As shown in FIG. 3, a load 58 was applied after the pulse energization 47 at the passage of the pressurization start point 57. Thereafter, in this example, discharging was performed as charging / discharging 52 (FIG. 3). The load 58 at the time of discharge was 500-2000g (Table 1).

  The load 58 during discharge in Examples 6 and 7 was 700 g, which is smaller than the load during discharge of the comparative example, but larger than that during pulse energization. The load during discharge in Example 8 was 500 g, which was smaller than the load during discharge in Comparative Example and Examples 6 and 7. The load during discharge in Example 8 was equivalent to that during pulse energization. Discharging was performed at 20 A for 10 seconds.

  The column of contact resistance in Table 1 shows the resistance value (Ω) of the above-described contact resistance R (FIG. 1). The contact resistance was measured by a method of measuring with a pseudo four-terminal measurement circuit using a milliohm high tester after pressurization. The numerical values in the table are expressed as relative values when the resistance value of the comparative example is 1.

  The temperature column in Table 1 indicates the temperature (° C.) of the thinnest portion (the portion that generates the most heat) of the probe pin after 10 s energization. The numerical values in the table are expressed as relative values when the temperature of the thinnest portion (the portion that generates the most heat) of the probe pin of the comparative example is 1.

  The column of wear in Table 1 shows the wearability of the contact portion 21 (FIG. 1) after repeating a predetermined number of cycles and charge / discharge in terms of the amount of wear.

  The column of evaluation represents a scale when adopting as a charge / discharge method judged from durability and temperature characteristics. -Indicates that it is worth adopting, but its value is equivalent to that of the comparative example. + Indicates that the value to adopt is high. ++ indicates that the value to be adopted is very high.

  The graph of FIG. 7 shows the charge / discharge method of the comparative example. In the comparative example, unlike the example, pulse energization was not performed. The current value curve 65 shows the time change of the absolute value of the current value on the left vertical axis. The load curve 60 shows the time change of the load on the right vertical axis.

  In the comparative example, the pin 20 (FIG. 1) was pressed against the electrode 25 (FIG. 1) at the pressurization start point 57. At this time, in order to suppress heat generation during energization, it is necessary to make the pressing load 61 (FIG. 7) larger than the load 58 (FIG. 3) in the embodiment. Further, in the comparative example, when charging / discharging 52 is started from the stage where the contact area is small (FIG. 5), current concentration occurs and the temperature is likely to rise.

  On the other hand, as shown in FIG. 3, in Examples 6-8, the load 58 at the time of charging / discharging could be made smaller than the load 61 (FIG. 7) (Table 1). This is because the contact resistance R (FIG. 1) can be suppressed by the pulse energization 47 (FIG. 3) as described above. In Examples 6 to 8, since the pin 20 was pressed against the electrode 25 with a smaller load than that of the comparative example during charging and discharging, the durability life of the pin 20 could be extended.

  FIG. 8 is a graph showing the relationship between the resistance value of the contact resistance R (FIG. 1) and the load 61 (FIG. 7) according to the comparative example. The rhombus represents the relationship between the contact resistance and the load in the comparative example. The triangle represents the relationship between the contact resistance and the load in Example 7 (pulse energization 20A, 10 seconds, pressure 700 g).

  As shown in FIG. 8, the resistance value decreased as the load increased. For this reason, the load 61 at the time of discharge was made larger than the load 58 of an Example in anticipation of reduction of contact resistance R (FIG. 1) (FIG. 7). On the other hand, the pin 20 (FIG. 1) was easily worn (Table 1).

  FIG. 9 is a graph showing the relationship between the contact resistance R (FIG. 1) and the number of charge / discharge cycles or the number of cycles according to the example. The white circle in the figure represents the contact resistance value with the positive electrode. The black circle in the figure represents the contact resistance value with the negative electrode.

  As shown in FIG. 9, in Example 6-8, the resistance value (Ω) of the contact resistance R (FIG. 1) did not easily increase even when the number of cycles increased. For this reason, in the method of the example, even if the number of cycles was repeated, the amount of generated heat was not easily increased.

  In the example, as described above, the pin 20 was pressed against the electrode 25 (FIG. 1) with a load 58 (FIG. 3) smaller than that of the comparative example. FIG. 10 is a photograph showing the tip shape of the pin 20 before performing pulse energization and charge / discharge in the example. In FIG. 10, the tip 71 of the probe pin is disposed so as to surround the tip of the pin 20, that is, the center 70 of the contact portion 21.

  FIG. 11 is a photograph showing the tip shape of the pin 20 after charging and discharging when a cycle test is performed in a comparative example compared with the example. Compared to FIG. 10, in FIG. 11, the wear was suppressed at the center 70 or the wear was small (Table 1). Further, the observed enlargement of the tip 71 of the probe pin was smaller than the comparative example described later.

  For this reason, in Example 6-8, even if the cycle number became large, it was estimated that the pin 20 (FIG. 1) mentioned above had little abrasion. In addition, it was estimated that the wear was less than that of the comparative example. That is, it was shown that the method according to the above example has an effect of reducing the maintenance frequency of the worn pin 20 (FIG. 1).

  FIG. 12 is a graph showing the relationship between the contact resistance R (FIG. 1) and the number of cycles according to the comparative example. As shown in FIG. 12, as the number of cycles increased, the resistance value of the contact resistance R (FIG. 1) increased. For this reason, in the method of the comparative example, the calorific value increased as the number of cycles increased. The white circle in FIG. 12 represents the contact resistance value of the positive electrode. A black circle represents the contact resistance value of the negative electrode.

  FIG. 13 is a photograph showing the tip shape of the pin 20 after charging and discharging in Comparative Example 7. Compared with FIG. 10, in FIG. 13, the wear progressed or increased at the center 70 (Table 1). Further, the observed enlargement of the tip 71 of the probe pin was larger than in the examples described later.

  In the comparative example, it was estimated that the wear of the pin 20 (FIG. 1) described above further progressed as the number of cycles increased. It was estimated that the wear increased as compared with Examples 6-8. Therefore, it was estimated that the frequency of maintenance of the worn pin 20 (FIG. 1) is higher than that of the example.

  The inventors considered that the tip of the pin 20 was worn by pressing the pin 20 against the electrode 25 (FIG. 1) with a large load 61 (FIG. 7). Further, the inventors considered that the progress of the wear was reflected in the resistance value (Ω) of the contact resistance R (FIG. 1).

  FIG. 14 is a graph showing the resistance value (Table 1) of the contact resistance R (FIG. 1) according to the example and the comparative example. In Example 3, the resistance value of the contact resistance R (FIG. 1) could be particularly suppressed. Example 4 was able to further suppress this resistance value, and Example 5 was the most effective. As described above, in Example 6-8, since the load at the time of discharge was reduced, the durability was further improved (Table 1, wear column).

  As described above, in Example 5, the pulse time was longer than the discharge time. For this reason, as shown in Table 1 and FIG. 14, although the resistance value was low, it was affected by the temperature increased during pulse energization.

  In addition, this invention is not limited to the form of the said Example and Example, It can change suitably in the range which does not deviate from the meaning.

20 pin 21 contact portion 24 terminal metal portion 25 electrode 26 film 27 surface 37 current 40 current 41-44 current level 45 current value curve 46 pulse start point 47 pulse energization 48 pulse end point 49 charge / discharge start point 50 pulse current value 51 charge Discharge current value 52 Charging / discharging 55 Load curve 56 Load 57 Pressurization start point 58 Load 60 Load curve 61 Load 65 Current value curve 70 Center 71 Tip of probe pin

Claims (2)

Touch the probe pin to the battery electrode,
A pulse energization is performed between the electrode and the probe pin,
The battery is charged and discharged after the pulse energization,
Charge / discharge method of secondary battery. The charge / discharge is performed while pressing the probe pin against the electrode with a load larger than that during the pulse energization.
The charging / discharging method of the secondary battery of Claim 1.