JP2013080652A - Secondary battery manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery manufacturing method that allows a worker to easily decide whether or not the impregnation state of an electrolyte to the inside of an electrode body has reached a permissible degree, and makes it possible to manufacture a secondary battery with a long lifetime and high performance.SOLUTION: A secondary battery manufacturing method according to the invention uses a conductive substance as a battery case, inserts an electrode body to which positive and negative terminal members are connected into the battery case, makes a state in which part of the positive and negative terminal members is projected out of the battery case and at least one of the positive and negative terminal members is not directly electrically connected to the case, injects an electrolyte into the battery case, obtains a value of resistance between a part projecting out of the terminal member not directly electrically connected to the battery case and the battery case, and moves to a next step if the obtained value of resistance indicates a predefined upward inclination relative to a value right after injection of the electrolyte.

Description

  The present invention relates to a method for manufacturing a secondary battery in which an electrode body and an electrolytic solution are enclosed in a battery case. More specifically, the present invention relates to a method of manufacturing an electrolyte secondary battery that can determine the completion of the impregnation of the electrolyte in the battery case in the battery case after the injection and can appropriately complete the battery. .

  The process of manufacturing a secondary battery includes a process of injecting an electrolytic solution into the battery case after the manufactured electrode body is inserted into the battery case. At this time, it is required that the electrolytic solution permeate appropriately between the electrode bodies. However, since the electrolytic solution and the electrode body are sealed in the battery case, the state of the liquid injection cannot be visually confirmed from the outside of the battery case.

  On the other hand, Patent Document 1 discloses a technique for determining the state of electrolyte injection by measuring the impedance between the positive terminal and the negative terminal of the battery. In this document, since this impedance decreases as the infusion progresses, it is described that the state of the infusion can be monitored by repeating the infusion and defoaming by pressurization / depressurization while measuring the impedance. And when the obtained impedance falls to a reference value, it is said that the battery has good battery characteristics.

Japanese Patent Application Laid-Open No. 2004-313143

  However, as shown in FIG. 5 of this document, the impedance value measured in the above-described conventional manufacturing method is greatly reduced immediately after the start of liquid injection, and the degree of subsequent reduction is moderate. Become. The reference value, which is the timing of the end of injection, is a position where a little time has passed since the decrease gradually slowed. That is, there is a problem that it is difficult to determine whether or not the reference value has been reached because it must be performed within a small range of change.

  Furthermore, in this document, only the determination up to the end of the injection is made. For example, in a large secondary battery mounted on an automobile or the like, the electrolyte is appropriately impregnated in the electrode body after the injection. It is necessary to wait until. This is because the width of the electrode body is large, and it takes time for the electrolytic solution to impregnate to the center of the electrode body. If the initial charge is performed in a state where the electrolyte is not sufficiently impregnated, the electrode reaction proceeds non-uniformly, so that the SOC unevenness of the electrode, the coating unevenness, etc. may occur, and the internal resistance of electricity may locally vary. The secondary battery thus configured has a problem that it has a short life.

  The degree of impregnation can also be determined by a method similar to the method described in Patent Document 1 above. That is, the internal resistance of the battery after injecting the electrolyte is measured, and the degree of impregnation is judged based on the change. This is because the internal resistance of the battery decreases as the impregnation progresses. However, when the impregnated state is saturated, the amount of change in the internal resistance of the battery becomes extremely small, and precise determination is difficult.

  The present invention has been made to solve the problems of the conventional method for manufacturing a secondary battery. In other words, the problem is that it is easy to determine whether the state of impregnation of the electrolyte in the electrode body has reached an acceptable level, and it is possible to manufacture a long-life, high-performance secondary battery. Another object of the present invention is to provide a method for manufacturing a secondary battery.

  A method for manufacturing a secondary battery according to the present invention for the purpose of solving this problem is a method for manufacturing a secondary battery in which an electrode body and an electrolytic solution are enclosed in a battery case. The electrode body to which the positive and negative terminal members are connected is inserted into the battery case, a part of the positive and negative terminal members protrudes outside the battery case, and at least one of the positive and negative terminal members is connected to the battery case. The battery is not directly connected, injecting electrolyte into the battery case, and obtaining the resistance value between the battery case and the part of the terminal member that is not directly connected to the battery case. When the acquired resistance value shows a predetermined upward tendency with respect to the value immediately after the injection of the electrolyte, the process proceeds to the next step.

  According to the method for manufacturing a secondary battery of the present invention, when an electrode body is put into a battery case and assembled, a part of positive and negative terminal members connected to the electrode body protrudes to the outside of the battery case. Immediately after injecting the electrolyte into the battery case, a liquid electrolyte is accumulated around the electrode body. If the battery case has conductivity, the terminal member is brought into conduction with the battery case through the electrode body and the electrolytic solution. If there is no conduction path through only the conductor between the terminal member and the battery case, the resistance value between the terminal member and the battery case is the electrolyte solution remaining in the liquid around the electrode body. It will correspond to the amount of. Therefore, by measuring the resistance value between the terminal member and the battery case from the outside of the battery case, the state of impregnation with the electrolytic solution can be grasped. In particular, the resistance value varies greatly depending on the presence or absence of the electrolyte solution that is in direct contact with the electrode body. As a result, it is possible to easily determine whether or not the state of impregnation of the electrolyte in the electrode body has reached an acceptable level, and a secondary battery capable of producing a long-life and high-performance secondary battery. It is a manufacturing method.

Furthermore, in the present invention, the battery case has a flat rectangular shape, and at least one of the positive and negative terminal members protrudes to a position within 1/3 of the longitudinal end of the upper surface of the battery case, and the battery Targeting a flat secondary battery that is not directly connected to the case, the resistance value is obtained so that one terminal member is above the other end in the longitudinal direction of the upper surface of the battery case. It is desirable to carry out between the one terminal member and the battery case with the case tilted.
In this way, the present invention can also be applied to an electrolyte in which the liquid level allowed to remain in liquid form outside the electrode body in the battery case is above the bottom surface of the electrode body. This is because it is possible to prevent the electrolytic solution from coming into direct contact with the terminal member located above by inclining. The angle to be inclined may be an angle at which the maximum amount of electrolyte that is allowed to remain is not in direct contact with the terminal member on top.

  According to the method for manufacturing a secondary battery of the present invention, it is possible to easily determine whether or not the state of impregnation of the electrolyte in the electrode body has reached an acceptable level, and have a long life and high performance. Can be manufactured.

It is a schematic block diagram which shows the secondary battery which concerns on this form. It is a schematic block diagram which shows the secondary battery in which impregnation is not completed. It is a graph which shows the relationship between impregnation time and resistance between terminal cases. It is a graph which shows the relationship between impregnation time and battery resistance. It is explanatory drawing which shows the secondary battery provided with the clearance. It is explanatory drawing which shows a mode that a secondary battery is inclined and it determines.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a manufacturing method for manufacturing a secondary battery such as a lithium ion secondary battery.

  As shown in FIG. 1, the secondary battery 10 according to this embodiment is configured such that an electrode body 20 is enclosed with an electrolyte solution 13 in a battery case 11. The battery case 11 has a box-shaped member 11a that is open on one side and a lid member 11b that seals the open side. In this embodiment, the battery case 11 has a flat rectangular shape that is flat in the depth direction of this figure. Similarly, the electrode body 20 is also formed flat.

  The lid member 11b is provided with a liquid injection port 15 for injecting the electrolytic solution 13 after the battery case 11 is assembled. The injection port 15 is sealed after the injection of the electrolytic solution 13 is completed. The battery case 11 of this embodiment is formed of a conductive material such as metal. Moreover, the electrolyte solution 13 is generally used for a lithium ion secondary battery. For example, a nonaqueous electrolyte solution containing lithium salt or an ion conductive polymer is suitable.

  The electrode body 20 of this embodiment is formed by winding a positive electrode plate and a negative electrode plate as shown in FIG. 2 of Japanese Patent Application Laid-Open No. 2007-053055, for example. In addition, a separator for insulating the two is disposed between the positive electrode plate and the negative electrode plate. The positive electrode plate, the negative electrode plate, and the separator may be general ones that have been conventionally used.

  The positive electrode plate is formed, for example, by forming a positive electrode active material layer on both surfaces of an aluminum foil. The positive electrode active material layer includes a positive electrode mixture of a positive electrode active material capable of occluding and releasing lithium ions. For example, a lithium-containing metal oxide kneaded with a binder and a dispersion solvent is preferable. is there. For example, the negative electrode plate is obtained by forming a negative electrode active material layer on both surfaces of a copper foil. The negative electrode active material layer includes a negative electrode mixture of a negative electrode active material capable of occluding and releasing lithium ions. For example, a layer containing a carbon material or the like is preferable.

  As shown in FIG. 1, a positive electrode terminal 21 and a negative electrode terminal 22 are connected to the electrode body 20 of this embodiment. The positive electrode terminal 21 is connected to the positive electrode current collector plate 24 (a portion of the positive electrode plate where the aluminum foil is exposed) inside the battery case 11, and a part thereof is disposed outside the battery case 11. . The negative electrode terminal 22 is connected to the negative electrode current collector plate 25 (a portion of the negative electrode plate where the copper foil is exposed) inside the battery case 11, and a part thereof is disposed outside the battery case 11. .

  The secondary battery 10 of this embodiment is usually arranged with the lid 11b facing up. The electrode body 20 is wound so that the positive electrode current collector plate 24 and the negative electrode current collector plate 25 are exposed at both ends in the horizontal direction. Each of the positive electrode terminal 21 and the negative electrode terminal 22 is connected to the exposed portion, and is disposed so as to protrude upward from the lid member 11b.

  Note that both the positive terminal 21 and the negative terminal 22 are insulated from the lid member 11 b, and there is no place that is in contact with or conductive with any part of the battery case 11. The electrode body 20 itself is also covered with a separator at its outermost periphery, and is not directly connected to the battery case 11. Here, being not directly conducting means that it is not in direct contact or connected through a conductive structure. Even conduction through the electrolyte is not excluded.

  In addition, what was shown in FIG. 1 is the secondary battery 10 of the state which the electrolyte solution 13 was impregnated suitably in the electrode body 20, and was completed. That is, the electrolytic solution 13 penetrates between the electrode plates of the electrode body 20 and is further soaked in the electrode active material and the like, and the amount of the liquid solution remaining in the battery case 11 and outside the electrode body 20 is very small. The liquid level L1 of the electrolytic solution 13 is substantially equal to the lowermost part of the electrode body 20.

  On the other hand, FIG. 2 shows the secondary battery 10 in which the injection of the electrolytic solution 13 has been completed but not impregnated, and the liquid level L2 of the electrolytic solution 13 is the lowest part of the electrode body 20. It is in a considerably higher position. That is, the secondary battery 10 in FIG. 2 is in a state where the positive electrode terminal 21 and the negative electrode terminal 22 are immersed in the liquid electrolyte solution 13 inside the battery case 11.

  The inventor found that the difference in the state of the secondary battery 10 between FIG. 1 and FIG. 2 is the resistance value through the electrolytic solution 13 between the electrode terminal (positive electrode terminal 21 or negative electrode terminal 22) and the battery case 11. It was found that it can be grasped as a difference. Hereinafter, the resistance value between the electrode terminal and the battery case 11 through the electrolytic solution 13 is referred to as a resistance between terminal cases.

  That is, the resistance value between the electrode terminal and the battery case 11 depends on the contact area between the electrode terminal (or the electrode current collector connected thereto) and the electrolyte solution 13, particularly whether or not they are in direct contact. It was very different. For example, as shown in FIG. 2, the resistance measurement unit 30 is used to measure the resistance value between the electrode terminal and the battery case 11, so that the impregnation is performed when the acquired resistance value shows a predetermined upward tendency. Was found to be complete.

  The resistance measuring unit 30 according to this embodiment includes a power source and an ammeter, and applies a voltage to both ends to obtain a resistance value from the relationship between the current value and the voltage value of the flowing current. The transition of the resistance value is, for example, as shown in FIG. In this example, the resistance value continued to be 0.1 kΩ or less immediately after the end of the injection, and the resistance value increased rapidly from about 1000 minutes after the injection. Note that the impregnation time of 0 minutes on the horizontal axis in this figure indicates the time immediately after the prescribed amount of the electrolyte solution 13 has been poured into the battery case 11.

  That is, as shown in FIG. 2, in the state where the electrode body 20 is immersed in the electrolytic solution 13, electrons are exchanged between the electrode terminal and the electrolytic solution 13 in contact with the electrode terminal, so that current can be relatively freely supplied. It can flow. Therefore, the resistance between terminal cases is small. On the other hand, when the liquid electrolyte solution 13 that is not impregnated decreases, the electrolyte solution 13 that is in direct contact with the electrode terminals decreases, making it difficult to exchange electrons. As a result, the resistance between terminal cases gradually increases.

  Then, as shown in FIG. 1, the liquid electrolyte solution 13 that is not impregnated becomes very small. In particular, when the electrode body 20 is not immersed in the electrolyte solution 13, the electrolyte solution 13 that is in direct contact with the electrode terminal is There will be no direct exchange of electrons. Therefore, the resistance between the terminal cases increases rapidly. That is, in the result of FIG. 3, the times A to C are in a state where the impregnation is not yet completed (the state shown in FIG. 2), and the times D and E are the states where the impregnation is completed (the state shown in FIG. 1). It corresponds. In any state, the electrolytic solution 13 and the battery case 11 are in wide contact with each other on the bottom surface, and the resistance therebetween is small.

  The results of FIG. 3 were measured with the secondary battery 10 standing up with the lid 11b up as shown in FIG. 1 and FIG. In the secondary battery 10 of this embodiment, when the impregnation is completed in this arrangement, the liquid surface of the electrolytic solution 13 becomes the same height as the lowermost surface of the electrode body 20. When the measurement is performed in this arrangement, the resistance measurement unit 30 is arranged between the negative electrode terminal 22 and the battery case 11 as shown in FIG. Even when the resistance measurement unit 30 was placed between the measurement results, the results were almost the same.

  The manufacturing method of the secondary battery 10 is as follows. First, the electrode body 20, the electrolytic solution 13, the battery case 11 and the like as described above are prepared. Then, the electrode body 20 is sealed in the battery case 11 to assemble the secondary battery, and the electrolytic solution 13 is injected. Further, the resistance between the terminal cases is measured using the resistance measuring unit 30 shown in FIG. Whether or not the impregnation is completed is determined based on whether or not the measured value shows a predetermined upward tendency. For example, if the resistance between the terminal cases exceeds a predetermined value, it is determined that the impregnation is completed. The threshold value may be acquired by experiment.

  Alternatively, since the value of the resistance between the terminal cases increases rapidly from a certain point in time, a threshold value is set for the difference from the previous time or the rate of increase, and it can be determined by whether or not the threshold value is exceeded. Alternatively, it may be determined how many times the initial resistance value (for example, it may be an average up to about time C). Even such a determination depending on the initial resistance value is included in “predetermined”. That is, the criteria for determination are not limited to those determined before the start of measurement, but may be those determined by the determination even after the start of measurement. If it is determined that the impregnation is completed, the process proceeds to the next step. The next process includes an initial charging process of the secondary battery, but the initial charging is not always performed immediately after the impregnation is completed. Then, the secondary battery 10 is completed.

  The inventor has confirmed the effect of the present invention through experiments. In this experiment, a battery having an initial capacity of 30 Ah was manufactured under the following conditions. As the positive electrode material, a ternary system of Ni / Mn / Co was used. Graphite was used as the negative electrode material. As the separator, a three-layer separator of PP / PE / PP was used. These were wound to form the electrode body 20, sealed in the battery case 11, and injected with the electrolytic solution 13.

  In this experiment, five secondary batteries having the same configuration were prepared, and the same process was performed up to the injection. Thereafter, the time for leaving for impregnation (impregnation time) was varied, and initial charging was performed immediately after the end of each impregnation time. When the initial charging is completed, the secondary battery is completed. Thereafter, a cycle test was performed as described later, and the performance of each secondary battery was compared. The impregnation time was 5 points indicated by A to E in FIG. In the following description, the secondary battery is represented by the sign of the time at which the initial charging is started, such as battery A and battery B.

  In this experiment, a secondary battery that can be determined to be impregnated when the resistance between the terminal cases exceeds 1.0 kΩ is used. That is, in the battery D and the battery E, initial charging was performed after it was determined that the impregnation was completed in this embodiment. On the other hand, the batteries A, B, and C were subjected to initial charging before it was determined that the impregnation was completed. In the same way, the initial charging was performed until the current value reached 0.1 A at 4.1 Vcccc (constant current constant voltage) 15 A (corresponding to 0.5 C). Then, it was left to stand for 24 hours in an environment of 60 ° C., and was aged. Thus, five types of secondary batteries were completed.

  In addition, when the secondary battery manufactured on the same conditions was determined with the battery resistance which is the conventional determination method, the result as shown in FIG. 4 was obtained. The battery resistance is an electrical resistance value between the positive terminal 21 and the negative terminal 22. In the conventional determination method, when the battery resistance falls below a predetermined value, it is determined that the impregnation is completed. For example, in FIG. 4, it was determined that the impregnation was completed when the battery resistance was less than 0.73 mΩ. Therefore, in the conventional determination method, battery A was not determined to be impregnated, but batteries B to E were determined to be impregnated. Note that A to E in FIG. 4 correspond to the same impregnation time as A to E in FIG.

And the cycle test of the battery A-the battery E was done, and the battery characteristic was evaluated by the capacity maintenance rate. The evaluation procedure is as follows.
First, charging up to 0.1 A at 4.1 Vcccc15A and discharging to 3.0 V at cc (constant current) 15 A were performed, and the discharge capacity by this discharge was taken as the initial capacity of the battery.
Subsequently, in an environment of 0 ° C., charging for 1.5 hours at 4.1 V cccv30A (1C) and discharging until it dropped to 2.5 V at cc30A were taken as one cycle, and 1000 cycles were repeated.
Subsequently, the capacity was checked under the same conditions as when the initial capacity was obtained. The ratio of the battery capacity obtained as a result to the initial capacity was defined as the capacity maintenance ratio.

  The results of the experiment are shown in Table 1 above. In this cycle test, batteries A to C could not be said to have a sufficient capacity retention rate. Battery D and Battery E had appropriate capacity maintenance rates. That is, the batteries D and E were good secondary batteries, but the batteries A to C were not good.

  This result was consistent with the determination of this embodiment in which it was determined that batteries A to C were not completely impregnated. On the other hand, in the determination of the comparative example, it was determined that the battery other than the battery A was completed, and did not match the result of the capacity maintenance rate. Therefore, it was confirmed that the determination result by the determination method of this embodiment is appropriate.

  If the method for measuring the resistance between the terminal cases is as shown in FIGS. 5 and 6, the change in the value of the resistance between the terminal cases can be obtained more clearly. FIG. 5 shows an example in which a clearance h is provided between the electrode body 20 and the battery case 11. As the impregnation of the electrolytic solution 13 proceeds, the liquid level of the electrolytic solution 13 decreases and enters the range of the clearance h. That is, the size relationship between the battery case 11 and the electrode body 20 or the injection amount of the electrolytic solution 13 may be set so as to be like this. In this way, when the impregnation is completed, the contact area between the liquid portion of the electrolytic solution 13 and the electrode terminal (the positive electrode terminal 21 or the negative electrode terminal 22) is further smaller than the example of FIG. Therefore, completion of impregnation can be clearly determined.

  Alternatively, as shown in FIG. 6, the secondary battery 10 may be tilted to measure the resistance between the terminal cases. That is, one end side in the longitudinal direction of the lid member 11b is lifted, and the battery case 11 is tilted so that the lid member 11b forms an inclination angle θ with respect to the horizontal plane. In this way, the electrolyte 13 remaining in the battery case 11 and outside the electrode body 20 gathers at the bottom on the other end side in the longitudinal direction of the lid 11b as shown in the figure.

  In the secondary battery 10 of the present embodiment, a positive electrode terminal 21 and a negative electrode terminal 22 protrude near the ends of a flat rectangular and substantially rectangular lid member 11b. Then, when the battery case 11 is erected with the terminals facing upward as shown in FIG. 1, the terminals of both electrodes and the electrode current collectors connected thereto are arranged on both sides in the battery case 11. Therefore, by tilting as described above, the electrode terminal and the electrode current collector plate (the positive electrode terminal 21 and the positive electrode current collector plate 24 in FIG. 6) on the lifted side are not in contact with the electrolytic solution 13. it can.

  Therefore, if the resistance measurement unit 30 measures the resistance value between the lifted electrode terminal and the battery case 11, the completion of impregnation can be clearly determined. In this method, at least one of the positive electrode terminal 21 and the negative electrode terminal 22 protrudes to a position within 1/3 from one end in the longitudinal direction of the lid member 11b and does not directly conduct to the battery case 11. It is particularly effective for those provided in

  6 is determined according to the amount of the electrolytic solution 13 that is allowed to remain in the battery case 11 and outside the electrode body 20 even after the impregnation is completed. With this method, there is no need to provide a clearance h between the electrode body 20 and the battery case 11. In this method, it is desirable to incline only during the measurement of the resistance between terminal cases for determination.

  As described above in detail, according to the determination method of the present embodiment, it can be easily and clearly determined whether or not the impregnation of the electrode body 20 with the electrolytic solution 13 is completed. Therefore, by performing the initial charging after the completion of impregnation can be confirmed by this determination method, a secondary battery having good performance thereafter can be obtained. As a result, it is possible to easily determine whether or not the state of impregnation of the electrolytic solution in the electrode body has reached an acceptable level, and a manufacturing method capable of manufacturing a long-life and high-performance secondary battery. ing.

  In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 10 Secondary battery 11 Battery case 13 Electrolytic solution 20 Electrode body 21 Positive electrode terminal 22 Negative electrode terminal

Claims (2)

In a method for manufacturing a secondary battery in which an electrode body and an electrolyte are enclosed in a battery case,
Use the battery case having conductivity,
The electrode body to which positive and negative terminal members are connected is inserted into the battery case, a part of the positive and negative terminal members protrudes outside the battery case, and at least one of the positive and negative terminal members is the battery case. And is not in direct conduction,
Injecting electrolyte into the battery case,
Obtaining a resistance value between the battery case and a portion projecting outside of the terminal member that is not directly connected to the battery case;
When the acquired resistance value shows a predetermined upward tendency with respect to the value immediately after the injection of the electrolyte, the process proceeds to the next step. In the manufacturing method of the secondary battery according to claim 1,
The battery case has a flat rectangular shape, and at least one of the positive and negative terminal members protrudes to a position within 1/3 from one end in the longitudinal direction of the upper surface of the battery case, and the battery case For flat-type secondary batteries that are not directly connected to
Obtaining the resistance value,
In the state where the battery case is inclined so that the one terminal member is above the other end in the longitudinal direction of the upper surface of the battery case,
A method for producing a secondary battery, wherein the method is performed between the one terminal member and the battery case.

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