JP2012221648A - Manufacturing method of nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a nonaqueous electrolyte secondary battery capable of highly accurately detecting a battery in which an internal short-circuit occurred.SOLUTION: In a self-discharge step (step S5), a first voltage value Vb is detected which is a battery voltage value of a battery 100 when a first prescribed time elapses after the battery was left unattended and further a second voltage value Vc is detected which is a battery voltage value of the battery when a second prescribed time elapses after the first voltage value Vb was detected. When a battery voltage difference ΔVbc obtained by subtracting the second voltage value Vc from the first voltage value Vb is greater than or equal to a prescribed threshold value, it is determined that an internal short-circuit occurred in the battery. In particular, the first prescribed time is defined to be from 5 hours to 72 hours and the second prescribed time is defined to be 48 hours or longer, and the first voltage value Vb and the second voltage value Vc are detected.

Description

  The present invention relates to a method for manufacturing a nonaqueous electrolyte secondary battery.

  In recent years, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries have been used as power sources for driving portable electronic devices such as hybrid cars, notebook computers, and video camcorders.

  By the way, in the process of manufacturing a nonaqueous electrolyte secondary battery (for example, an assembly process), conductive foreign matters such as metal powder may be erroneously mixed into the battery (inside the electrode). When such a battery is used, dendrites derived from conductive foreign matter are generated and an internal short circuit occurs (the positive electrode plate and the negative electrode plate electrically insulated by the separator are electrically connected through the dendrite. )Sometimes.

  On the other hand, Patent Document 1 proposes a method for inspecting whether or not conductive foreign matters are mixed in order to prevent such a battery from being shipped (supplied to the market). Specifically, after the battery is assembled, initial charging or the like is performed, and then the battery is left in a temperature environment of 45 ° C. or higher for a predetermined time. Then, the amount of voltage drop during the standing period is measured. That is, a voltage drop amount obtained by subtracting the battery voltage value at the end of leaving from the battery voltage value at the start of leaving is obtained. And when the calculated voltage drop amount is larger than a preset reference value, it is determined that conductive foreign matter is mixed in the battery.

  Patent Document 1 describes that the above method is based on the following principle. When conductive foreign matter exists between the positive and negative electrodes and the separator, if a lithium ion secondary battery is left at an environmental temperature of 45 ° C. or higher for a predetermined time, conductive crystals (dendrites) grow from the conductive foreign matter. proceed. For this reason, since a conductive foreign material penetrates a separator in a short time and causes an internal short circuit, a voltage drop exceeding a normal voltage drop occurs. Therefore, it is described that a battery in which conductive foreign matter is mixed (a battery in which an internal short circuit has occurred) can be detected by the above method.

Japanese Patent Laid-Open No. 2005-158643

  However, when the non-aqueous electrolyte secondary battery is left as it is, it has been found that the battery voltage value greatly decreases and the variation in the amount of voltage decrease is large at the initial stage of the storage (for example, within a period of 5 hours from the start of the storage). . For this reason, as in Patent Document 1, whether or not the voltage drop amount obtained by subtracting the battery voltage value at the end of leaving from the battery voltage value at the start of leaving is larger than a predetermined threshold with reference to the battery voltage value at the start of leaving. Therefore, the method for determining whether or not an internal short circuit has occurred in the battery cannot accurately detect the battery in which the internal short circuit has occurred.

  In more detail, in many cases, the battery with internal short circuit has a larger self-discharge amount due to neglect than the battery without normal short circuit (normal battery). Also grows. However, since the battery voltage value greatly decreases at the initial stage of standing (especially within a period of 5 hours from the start of standing) and the variation in the voltage drop is large, the battery (normal battery) in which no internal short circuit has occurred. In some cases, the amount of voltage drop during the entire leaving period may be the same as that of a battery in which an internal short circuit occurs. Therefore, if the period of the initial stage of standing (in particular, within 5 hours from the start of standing) is included in the measurement period of the voltage drop, which is a short-circuit judgment criterion, a part of the battery (normal battery) in which no internal short-circuiting occurs However, there was a case where a clear difference in voltage drop amount did not appear between the batteries in which an internal short circuit occurred. For this reason, it becomes impossible to accurately detect a battery in which an internal short circuit has occurred.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a method for manufacturing a nonaqueous electrolyte secondary battery that can accurately detect a battery in which an internal short circuit has occurred. .

  One aspect of the present invention is a non-aqueous process comprising a self-discharge step of self-discharging the battery by leaving the non-aqueous electrolyte secondary battery containing the electrode body and the non-aqueous electrolyte in a battery case for a predetermined period of time. In the method for manufacturing an electrolyte secondary battery, the self-discharge step detects a first voltage value Vb that is a battery voltage value of the battery when a first predetermined time has elapsed since the start of the leaving of the battery. Furthermore, the second voltage value Vc, which is the battery voltage value of the battery when the second predetermined time has elapsed since the first voltage value Vb was detected, is detected, and the second voltage value is determined from the first voltage value Vb. When the battery voltage difference ΔVbc obtained by subtracting the value Vc is equal to or greater than a predetermined threshold, it is a step of determining that an internal short circuit has occurred in the battery, and the first predetermined time is set within a range of 5 to 72 hours. The second predetermined time is 48 hours Determined above is a manufacturing method of the nonaqueous electrolyte secondary battery to detect the first voltage value Vb and the second voltage value Vc.

  In the non-aqueous electrolyte secondary battery manufacturing method described above, in the self-discharge process, the first predetermined time is set within a range of 5 to 72 hours, the first voltage value Vb is detected, and the second predetermined time is 48 hours or more. And the second voltage value Vc is detected. That is, the first voltage value Vb, which is the battery voltage value of the battery, is detected when 5 to 72 hours (first predetermined time) have elapsed since the start of the leaving of the battery. Furthermore, when 48 hours or more (second predetermined time) has elapsed since the first voltage value Vb was detected, the second voltage value Vc that is the battery voltage value of the battery is detected. Thereafter, it is determined whether or not the battery voltage difference ΔVbc obtained by subtracting the second voltage value Vc from the first voltage value Vb thus detected is equal to or greater than a predetermined threshold value. It is determined that an internal short circuit has occurred in the battery. According to such a method, a battery in which an internal short circuit has occurred can be detected with high accuracy.

  Specifically, within 5 hours after the start of leaving the battery, the battery voltage value is particularly greatly reduced, and the variation in the voltage drop amount is also large. For this reason, as described above, whether or not the battery voltage difference obtained by subtracting the battery voltage value at the end of leaving from the battery voltage value at the start of leaving is equal to or greater than a predetermined threshold, based on the battery voltage value at the start of leaving. Thus, in the method for determining whether or not an internal short circuit has occurred in the battery, the battery in which the internal short circuit has occurred cannot be accurately detected.

  On the other hand, in the above self-discharge process, when 5 to 72 hours (first predetermined time) have elapsed since the start of leaving the battery, the first voltage value Vb, which is the battery voltage value of the battery, is set. Detect. By detecting the first voltage value Vb when more than 5 hours have passed since the start of the standing, “particularly the period during which the battery voltage value is greatly reduced and the variation in the amount of voltage drop is large (beginning of leaving) Can be excluded from the measurement period of the battery voltage difference ΔVbc, which is a short-circuit determination criterion. Thereby, the above-mentioned problems can be solved.

  In addition, since the battery manufacturing period is required to be as short as possible, it is necessary to shorten the period for which the battery is left as much as possible. On the other hand, by setting the first predetermined time within 72 hours, it is possible to accurately detect a battery in which an internal short circuit has occurred in a short leaving period (for example, within 7 days).

  Further, in the above self-discharge process, when 48 hours or more (second predetermined time) has elapsed since the first voltage value Vb was detected, the second voltage value Vc that is the battery voltage value of the battery is detected. Then, the battery voltage difference ΔVbc is measured. In this way, by measuring the battery voltage difference ΔVbc (= first voltage value Vb−second voltage value Vc) over a period of 48 hours or longer, a battery (normal battery) in which an internal short circuit has not occurred and an internal short circuit are detected. A clear difference appears in the battery voltage difference ΔVbc from the generated battery. For this reason, the battery in which the internal short circuit has arisen can be detected accurately.

  In the above-described self-discharge process, after the second voltage value Vc is detected, the nonaqueous electrolyte secondary battery is left unattended. That is, after detecting the second voltage value Vc, the predetermined period for leaving the battery expires.

  Furthermore, in the method for manufacturing the nonaqueous electrolyte secondary battery, in the self-discharge step, the first predetermined time is set within a range of 24 to 60 hours, and the second predetermined time is set to 60 hours or more. Thus, a non-aqueous electrolyte secondary battery manufacturing method that detects the first voltage value Vb and the second voltage value Vc is preferable.

  As described above, in the period within 5 hours from the start of standing, especially, the battery voltage value greatly decreases and the variation in the voltage decrease amount is large, but the battery voltage value decreases relatively for a while after that. The variation in the voltage drop tends to increase. Specifically, during a period of 24 hours from the start of leaving, the battery voltage value tends to decrease relatively and the variation in voltage decrease tends to increase.

  On the other hand, in the above-described manufacturing method, in the self-discharge process, the first predetermined time is set within a range of 24 to 60 hours, the second predetermined time is set to 60 hours or more, and the first voltage value Vb and the second voltage are set. The voltage value Vc is detected. That is, the first voltage value Vb that is the battery voltage value of the battery is detected when 24 to 60 hours (first predetermined time) have elapsed since the start of the leaving of the battery. Furthermore, when 60 hours or more (second predetermined time) has passed since the first voltage value Vb was detected, the second voltage value Vc, which is the battery voltage value of the battery, is detected.

  As described above, when the first voltage value Vb is detected when 24 hours or more have elapsed since the start of being left, the “period in which the battery voltage value is significantly decreased and the variation in the voltage decrease amount is also increased. (Period within 24 hours from start of standing) ”can be excluded from the measurement period of the battery voltage difference ΔVbc, which is a short-circuit determination criterion. In addition, by setting the first predetermined time within 60 hours, it is possible to accurately detect a battery in which an internal short circuit has occurred in a short standing period (for example, within 7 days).

  Further, in the above self-discharge process, when 60 hours or more (second predetermined time) has elapsed since the first voltage value Vb was detected, the second voltage value Vc, which is the battery voltage value of the battery, is detected. Then, the battery voltage difference ΔVbc is measured. In this way, by measuring the battery voltage difference ΔVbc (= first voltage value Vb−second voltage value Vc) over a period of 60 hours or more, a battery (normal battery) in which no internal short circuit has occurred and an internal short circuit are detected. A clear difference appears in the battery voltage difference ΔVbc from the generated battery. For this reason, the battery in which the internal short circuit has arisen can be detected still more accurately.

  Further, any one of the above non-aqueous electrolyte secondary battery manufacturing methods, wherein, in the self-discharge step, the predetermined period of leaving the battery is left within 7 days. good.

By shortening the “predetermined period” in which the battery is left to within 7 days, the period of the self-discharge process can be shortened, and as a result, the production efficiency of the battery can be improved. In the above-described self-discharge process, as described above, even if the leaving period is shortened to within 7 days, it is possible to accurately detect a battery in which an internal short circuit has occurred. Therefore, according to the manufacturing method described above, it is possible to improve the detection accuracy of the internal short circuit battery while improving the battery production efficiency.
Note that setting the “predetermined period” for leaving the battery to be within 7 days means that the detection of the second voltage value Vc is completed within 7 days after the start of the battery leaving.

It is a perspective view of the nonaqueous electrolyte secondary battery concerning an embodiment. It is a perspective view of the positive electrode plate of the same nonaqueous electrolyte secondary battery. It is a perspective view of the negative electrode plate of the same nonaqueous electrolyte secondary battery. It is an expanded sectional view of the same negative electrode plate, and corresponds to the AA sectional view of FIG. It is a flowchart which shows the flow of the manufacturing method of the nonaqueous electrolyte secondary battery concerning embodiment. It is a perspective view which shows the state which pinched | interposed the battery which finished the assembly | attachment process with the pressing jig, and was made into the restraint state. It is a graph which shows the relationship between a leaving period and a battery voltage variation | change_quantity, Comprising: It is a graph which shows the voltage variation | change_quantity from the time of a leaving start (voltage variation when a 1st predetermined time is set to 0 hours). It is a graph which shows the relationship between a leaving period and a battery voltage variation | change_quantity, Comprising: It is a graph which shows the voltage variation | change_quantity (voltage variation | change_quantity when the 1st predetermined time is set to 36 hours) after 36 hours have passed since the leaving start. is there. It is a graph which shows the minimum difference (DELTA) Vmin (The difference of (DELTA) Vbc of the internal short circuit battery in which (DELTA) Vbc became the maximum, and the normal battery in which (DELTA) Vbc became the minimum) of 1st predetermined time and battery voltage difference (DELTA) Vbc.

First, the nonaqueous electrolyte secondary battery 100 manufactured by the manufacturing method of this embodiment will be described.
As shown in FIG. 1, the nonaqueous electrolyte secondary battery 100 is a lithium ion secondary battery that includes an electrode body 110 and a battery case 180 that houses the electrode body 110. The electrode body 110 includes a positive electrode plate 130, a negative electrode plate 120, and a separator 150. The separator 150 is made of polyethylene, and is interposed between the positive electrode plate 130 and the negative electrode plate 120 to separate them. The separator 150 is impregnated with a non-aqueous electrolyte 160 having lithium ions.

  The battery case 180 is made of aluminum and has a rectangular parallelepiped shape. The battery case 180 has a battery case main body 181 and a sealing lid 182. Among these, the battery case main body 181 has a bottomed rectangular box shape. Note that an insulating film (not shown) made of a resin and bent in a box shape is interposed between the battery case main body 181 and the electrode body 110. The battery case 180 has a pair of wide side surfaces 180b and 180c facing away from each other. The wide side surface 180b is a surface facing the front side in FIG. 1, and the wide side surface 180c is a surface facing the back side in FIG. 1 (a surface located on the back side of the wide side surface 180b).

  The sealing lid 182 has a rectangular plate shape, closes the opening of the battery case body 181, and is welded to the battery case body 181. A rectangular plate-shaped safety valve 197 is sealed on the sealing lid 182.

  Further, a plate-like positive electrode current collecting member 191 bent in a crank shape is welded to the positive electrode plate 130 of the electrode body 110 (see FIG. 1). Further, a plate-like negative electrode current collecting member 192 bent in a crank shape is welded to the negative electrode plate 120. Of the positive electrode current collecting member 191 and the negative electrode current collecting member 192, the positive electrode terminal portion 191A and the negative electrode terminal portion 192A located at the respective tips penetrate the sealing lid 182 and protrude from the lid surface 182A. Insulating members 195 made of electrically insulating resin are interposed between the positive electrode terminal portion 191A and the sealing lid 182 and between the negative electrode terminal portion 192A and the sealing lid 182, respectively.

In addition, the non-aqueous electrolyte 160 is composed of LiPF ₆ as a solute in a mixed organic solvent in which ethylene carbonate (EC), methyl ethyl carbonate (MEC), and dimethyl carbonate (DMC) are adjusted to a volume ratio of 3: 4: 3. Is a non-aqueous electrolyte to which is added. The concentration of LiPF ₆ in the non-aqueous electrolyte 160 is 1 mol / L.

  The electrode body 110 is a wound electrode body in which a belt-like positive electrode plate 130 and a negative electrode plate 120 are wound into a flat shape via a belt-like separator 150 (see FIG. 1). Specifically, the strip-shaped positive electrode plate 130, the negative electrode plate 120, and the separator 150 extending in the longitudinal direction DA are wound in the longitudinal direction DA to form a wound electrode body 110 (FIGS. 1 to 4). reference). In the electrode body 110, the positive electrode active material layer 131 of the positive electrode plate 130 and the negative electrode active material layer 121 of the negative electrode plate 120 face each other with the separator 150 interposed therebetween (see FIG. 4).

  As shown in FIG. 2, the positive electrode plate 130 has a belt-like shape extending in the longitudinal direction DA. The positive electrode current collector plate 138 made of aluminum foil and both main surfaces of the positive electrode current collector plate 138 extend in the longitudinal direction DA. It has two positive electrode active material layers 131 and 131 arranged in a strip shape. The positive electrode active material layer 131 includes a positive electrode active material 137, a conductive material made of acetylene black, PEO (polyethylene oxide), and CMC (carboxymethylcellulose) in a weight ratio of 88: 10: 1: 1. Yes.

Note that as the positive electrode active material 137, Li _x MO ₂ (M is Ni, or in addition to Ni as a main component, Al, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Mg, 1.04 ≦ X ≦ 1.15) containing at least one of Ga, Zr, and Si is used. In addition, carbon layers 139 are provided on both surfaces of the aluminum foil forming the positive electrode current collector plate 138. The carbon layer 139 contains acetylene black and polyvinylidene fluoride in a weight ratio of 3: 7.

  Further, as shown in FIG. 3, the negative electrode plate 120 is formed on a negative electrode current collector plate 128 made of a copper foil in a strip shape extending in the longitudinal direction DA, and on both main surfaces 128 F and 128 F of the negative electrode current collector plate 128. It has two negative electrode active material layers 121 and 121 arranged in a strip shape extending in the direction DA. The negative electrode active material layer 121 includes the negative electrode active material 127, SBR (styrene butadiene rubber), CMC, and (carboxymethyl cellulose) in a weight ratio of 98: 1: 1.

  In addition, as the negative electrode active material 127, a material in which particles of the negative electrode active material are composed of graphite and amorphous carbon (for example, a surface of graphite covered with amorphous carbon) is used. A metal oxide insulating layer 129 is provided on the surface of the negative electrode active material layer 121. The metal oxide insulating layer 129 contains aluminum oxide (alumina) and polyvinylidene fluoride in a weight ratio of 95: 5.

  As shown in FIGS. 3 and 4 (AA cross-sectional view of FIG. 3), the negative electrode active material layer 121 includes a facing portion 122 that faces the positive electrode active material layer 131 through the separator 150, and a separator 150. It consists of a non-facing portion 123 where the facing positive electrode active material layer 131 does not exist. Specifically, the negative electrode active material layer 121 has a larger area than the positive electrode active material layer 131, and the non-opposing portion 123 is positioned around the opposing portion 122. Note that the position of the boundary between the non-facing portion 123 and the facing portion 122 in the negative electrode active material layer 121 is determined when the electrode body 110 is formed by winding the negative electrode plate 120, the separator 150, and the positive electrode plate 130. In FIG. 4, for reference, the positions of the positive electrode plate 130 and the separator 150 when the electrode body 110 is formed are indicated by a two-dot chain line.

Next, the manufacturing method of the nonaqueous electrolyte secondary battery according to the present embodiment will be described. FIG. 5 is a flowchart showing a flow of a manufacturing method of the nonaqueous electrolyte secondary battery according to the present embodiment.
First, in step S <b> 1 (assembly process), a battery in which the electrode body 110 and the nonaqueous electrolyte solution 160 are housed in the battery case 180 is manufactured. Specifically, first, the positive electrode active material 137, acetylene black, PEO (polyethylene oxide), and CMC (carboxymethylcellulose) are mixed at a weight ratio of 88: 10: 1: 1, and water (solvent) is mixed therewith. Were mixed to prepare a positive electrode slurry. Next, this positive electrode slurry was applied to the surface of a positive electrode current collector plate 138 made of aluminum foil (having a carbon layer 139 on the surface), dried, and then pressed. Thereby, the positive electrode plate 130 was obtained.

  A carbon layer 139 is formed in advance on the surface of the aluminum foil that forms the positive electrode current collector plate 138. The carbon layer 139 contains acetylene black and polyvinylidene fluoride in a weight ratio of 3: 7. By providing the carbon layer 139 on the surface of the aluminum foil, when the positive electrode slurry is applied, contact between the positive electrode slurry (being alkaline) and the aluminum foil constituting the positive electrode current collector plate 138 can be prevented. Thereby, corrosion of the aluminum foil which comprises the positive electrode current collecting plate 138 can be prevented. The thickness of the carbon layer 139 is preferably 1 to 5 μm.

  Moreover, the negative electrode active material 127, SBR (styrene butadiene rubber), CMC, and (carboxymethylcellulose) were mixed in water in the ratio of 98: 1: 1 (weight ratio), and the negative electrode slurry was produced. Next, this negative electrode slurry was applied on both main surfaces 128F of the negative electrode current collector plate 128 made of copper foil, dried, and then pressed. Thereby, the negative electrode plate 120 was obtained.

  The negative electrode active material 127 can be produced, for example, as follows. Spherical shaped graphite and pitch (petroleum pitch) are mixed and fired. By this firing, the pitch (petroleum pitch) becomes amorphous carbon. Thereafter, the fired body is pulverized, whereby the negative electrode active material 127 (graphite surface coated with amorphous carbon) can be obtained.

Note that as the negative electrode active material 127, it is preferable to use a negative electrode active material in which the ratio of amorphous carbon (amorphous carbon content) is in the range of 2.5 to 7.1 wt%. As the negative electrode active material 127, it is preferable to use a negative electrode active material in which the BET specific surface area of the negative electrode active material particles is in the range of 2.8 to 5.2 m ² / g. In the present embodiment, the value of the specific surface area obtained by a known BET method (specifically, the N ₂ gas adsorption method) is adopted as the value of the BET specific surface area.

  A metal oxide insulating layer 129 is formed on the surface of the negative electrode active material layer 121. Specifically, aluminum oxide (alumina) and polyvinylidene fluoride are mixed at a weight ratio of 95: 5, and a solvent is mixed with this to obtain a paste. The paste is applied to the surface of the negative electrode active material layer 121 and dried, whereby the metal oxide insulating layer 129 can be formed. Note that the thickness of the metal oxide insulating layer 129 is preferably 2 to 8 μm.

  In the present embodiment, the capacity ratio between the positive electrode capacity and the negative electrode capacity (negative electrode capacity / positive electrode capacity) is 1.4. Note that the capacity ratio between the positive electrode capacity and the negative electrode capacity (the ratio of the negative electrode capacity to the positive electrode capacity) is the capacity ratio between the positive electrode active material layer 131 and the facing portion 122 of the negative electrode active material layer 121. This capacity ratio can be adjusted by increasing or decreasing the thickness of the negative electrode active material layer 121 (opposing portion 122) (that is, the coating amount of the negative electrode slurry).

  Thereafter, the electrode body 110 is formed by winding the separator 150 between the negative electrode plate 120 and the positive electrode plate 130. Note that the separator 150, the negative electrode plate 120, the separator 150, and the positive electrode plate 130 are disposed so that the positive electrode active material layer 131 of the positive electrode plate 130 faces the facing portion 122 of the negative electrode active material layer 121 of the negative electrode plate 120 through the separator 150. The layers are wound in the order of (see FIG. 4).

  Thereafter, the negative electrode current collecting member 192 is welded to the negative electrode plate 120 (negative electrode current collecting plate 128), and the positive electrode current collecting member 191 is welded to the positive electrode plate 130 (positive electrode current collecting plate 138). Next, after the electrode body 110 welded to the negative electrode current collecting member 192 and the positive electrode current collecting member 191 is inserted into the battery case main body 181, the nonaqueous electrolyte solution 160 is injected. Thereafter, the sealing lid 182 and the battery case main body 181 are welded in a state where the opening of the battery case main body 181 is closed with the sealing lid 182 to complete the assembly of the nonaqueous electrolyte secondary battery.

  Next, the process proceeds to step S2 (battery restraint step) (see FIG. 5), and the nonaqueous electrolyte secondary battery produced in the above assembly step (step S1) is sandwiched between the pressing jigs 30 and 40 to be in a restraint state. (See FIG. 6). Specifically, as shown in FIG. 6, the nonaqueous electrolyte secondary battery 100 is sandwiched between the pressing jigs 30 and 40 so that the wide side surfaces 180 b and 180 c of the battery case 180 are pressed by the pressing jigs 30 and 40. Thus, the nonaqueous electrolyte secondary battery 100 is brought into a restrained state. Specifically, the pressing jig 30 disposed on the wide side surface 180 b side of the battery case 180 and the pressing jig 40 disposed on the wide side surface 180 c side are fastened using the cylindrical rod 51 and the nut 53. Thus, the non-aqueous electrolyte secondary battery 100 is sandwiched between the pressing jigs 30 and 40, and the wide side surfaces 180 b and 180 c of the battery case 180 are pressed with the pressing jigs 30 and 40. Thus, a predetermined load (for example, 400 to 800 kgf) is applied to the battery case 180.

  Next, it progresses to step S3 (initial charge process) (refer FIG. 5), and the nonaqueous electrolyte secondary battery 100 of the state (state shown in FIG. 6) restrained with the pressing jigs 30 and 40 is initially charged. Specifically, charging is performed with a constant current of 1 C (5 A) until the battery voltage value reaches a predetermined charging end voltage value Va, and then charging is performed while the battery voltage value is maintained at Va. When the voltage drops to 1A, the initial charging is terminated. By this initial charging, the nonaqueous electrolyte secondary battery 100 can be activated. In addition, an SEI (film) can be formed on the surface of the negative electrode active material 127.

The charge end voltage value Va is set to, for example, 4.1 V (corresponding to the battery voltage value when SOC is 100%). Here, SOC is an abbreviation for State Of Charge.
Further, 1C is a current value at which the discharge having a rated capacity value (nominal capacity value) is constant-current discharged and discharge is completed in one hour. Since the rated capacity (nominal capacity) of the nonaqueous electrolyte secondary battery 100 is 5.0 Ah, 1C = 5.0 A.

  Next, the process proceeds to step S4 (aging process), and the non-aqueous electrolyte secondary battery 100 in the restraint state (the state shown in FIG. 6) after the initial charge (the process of step S3) (the battery voltage value is Va). Is aged at a predetermined temperature (for example, 50 ° C.) for a certain period of time (for example, 15 hours).

  By the way, in the assembly process (step S1), metal powder (such as Cu powder) may be mixed in the electrode body 110 by mistake. In such a battery, dendrite derived from metal powder is generated in the aging process, and an internal short circuit occurs (the positive electrode plate 130 and the negative electrode plate 120 that are electrically insulated by the separator 150 are electrically connected through the dendrite. Sometimes). For this reason, in step S5 (self-discharge process) to be described later, a battery in which an internal short circuit has occurred is detected so as not to be shipped (removed as a defective product).

  Next, the process proceeds to step S5 (self-discharge process), and the nonaqueous electrolyte secondary battery 100 in the restraint state (state shown in FIG. 6) after aging (the process of step S4) is completed in a temperature environment of 25 ° C. It is self-discharged by leaving it for a predetermined period (for example, 5 days).

  In step S5 (self-discharge process), the battery voltage value (first voltage value Vb) of the battery when the first predetermined time has elapsed since the non-aqueous electrolyte secondary battery 100 is left unattended is detected ( taking measurement. Furthermore, the battery voltage value (second voltage value Vc) of the battery when the second predetermined time has elapsed from when the first voltage value Vb is detected is detected (measured). Then, after detecting the second voltage value Vc, the non-aqueous electrolyte secondary battery 100 is left unattended. That is, after detecting the second voltage value Vc, the predetermined period for leaving the battery expires.

  Further, in step S5 (self-discharge process), a battery voltage difference ΔVbc (= Vb−Vc) obtained by subtracting the second voltage value Vc from the first voltage value Vb is calculated, and the battery voltage difference ΔVbc is equal to or greater than a predetermined threshold value Tbc. It is determined whether or not. When the battery voltage difference ΔVbc is equal to or greater than the threshold value Tbc, it is determined that an internal short circuit has occurred in the battery 100. A battery determined to have an internal short circuit is removed as a defective product (for example, discarded).

  In a battery in which an internal short circuit has occurred, the amount of self-discharge due to neglect is increased compared to a battery in which an internal short circuit has not occurred (a normal battery), so that the battery voltage value decreases and the battery voltage difference ΔVbc also increases. Therefore, as described above, it is possible to determine whether or not an internal short circuit has occurred in the battery based on the battery voltage difference ΔVbc.

  By the way, within 5 hours after starting to leave the battery, the battery voltage value is particularly greatly reduced, and the variation in the voltage drop amount is also large. For this reason, as in the prior art (for example, Patent Document 1), the battery voltage difference obtained by subtracting the battery voltage value at the end of leaving from the battery voltage value at the start of leaving is set to a predetermined value based on the battery voltage value at the start of leaving. According to the method for determining whether or not an internal short circuit has occurred in the battery depending on whether or not it is greater than or equal to the threshold value, the battery in which the internal short circuit has occurred cannot be accurately detected.

  In contrast, in the self-discharge process (step S5) of the present embodiment, the first predetermined time is set within a range of 5 to 72 hours, and the first voltage value Vb is detected. That is, the first voltage value Vb, which is the battery voltage value of the battery, is detected when 5 to 72 hours (first predetermined time) have elapsed since the battery 100 is left unattended. By detecting the first voltage value Vb when more than 5 hours have passed since the start of the standing, “particularly the period during which the battery voltage value is greatly reduced and the variation in the amount of voltage drop is large (beginning of leaving) Can be excluded from the measurement period of the battery voltage difference ΔVbc, which is a short-circuit determination criterion. As a result, the above-described problems can be solved and a battery in which an internal short circuit has occurred can be detected with high accuracy.

  In addition, since the battery manufacturing period is required to be as short as possible, it is necessary to shorten the period for which the battery is left as much as possible. On the other hand, by setting the first predetermined time within 72 hours, it is possible to accurately detect a battery in which an internal short circuit has occurred in a short leaving period (for example, within 7 days).

  In the self-discharge process (step S5) of the present embodiment, the “predetermined period” in which the battery is left is within 7 days (for example, 5 days). By shortening the “predetermined period” in which the battery is left to within 7 days, the period of the self-discharge process can be shortened, and as a result, the production efficiency of the battery can be improved.

In this embodiment, as will be described later, even if the leaving period is shortened to within 7 days, a battery in which an internal short circuit has occurred can be accurately detected. Accordingly, it is possible to improve the detection accuracy of the internal short-circuit battery while improving the battery production efficiency.
Note that setting the “predetermined period” for leaving the battery to be within 7 days means that the detection of the second voltage value Vc is completed within 7 days after the start of the battery leaving.

  Further, in the self-discharge process (step S5) of the present embodiment, the second predetermined time is set to 48 hours or more, and the second voltage value Vc is detected. That is, when 48 hours or more (second predetermined time) has elapsed since the first voltage value Vb was detected, the second voltage value Vc that is the battery voltage value of the battery is detected, and the battery voltage difference ΔVbc is determined. taking measurement. In this way, by measuring the battery voltage difference ΔVbc (= first voltage value Vb−second voltage value Vc) over a period of 48 hours or longer, a battery (normal battery) in which an internal short circuit has not occurred and an internal short circuit are detected. A clear difference appears in the battery voltage difference ΔVbc from the generated battery. For this reason, the battery in which the internal short circuit has arisen can be detected accurately.

  Further, as will be described later, in the self-discharge process (step S5), the first predetermined time is set within a range of 24 to 60 hours to detect the first voltage value Vb, and the second predetermined time is set to 60 hours or more. And the second voltage value Vc is detected to detect the internal short circuit battery with higher accuracy.

  Note that the threshold Tbc is, for example, a value between the battery voltage difference ΔVbc of both batteries obtained by examining the battery voltage difference ΔVbc of a battery in which an internal short circuit has occurred and a battery in which no internal short circuit has occurred. It ’s fine.

  Next, the process proceeds to step S6 (discharge amount measurement step), and the battery voltage value of the nonaqueous electrolyte secondary battery 100 determined that the internal short circuit has not occurred (is normal) in step S5 is a predetermined discharge end. The battery is forcibly discharged until the voltage value Ve is reached. For example, using a known charging / discharging device, the battery 100 is discharged at a constant current of 1 C (5 A) until the battery voltage value of the battery 100 reaches the end-of-discharge voltage value Ve. Further, during the discharge period, the discharge electric quantity Qde of the battery 100 during the period from the battery voltage value to the discharge end voltage value Ve from the predetermined measurement start voltage value Vd is measured. Thereafter, it is determined whether or not the discharge electricity amount Qde is smaller than a predetermined threshold value Tde, and the battery having the discharge electricity amount Qde smaller than the threshold value Tde is removed as a defective product (for example, discarded).

In step S6 (discharge amount measuring step), the measurement start voltage value Vd is set to a value equal to or lower than the leaving end voltage value Vc in the self-discharge step. Further, the discharge end voltage value Ve is set to a value smaller than the measurement start voltage value Vd. In the present embodiment, the discharge end voltage value Ve is set to 3.55 V (corresponding to the battery voltage value when the SOC is 30%). However, the value of the discharge end voltage value Ve is not limited to 3.55V.
In step S6 (discharge amount measuring step), the nonaqueous electrolyte secondary battery 100 remains in the state of being restrained by the pressing jigs 30 and 40 (the state shown in FIG. 6).

  Next, the process proceeds to step S7 (internal resistance measurement process), and the internal resistance (IV resistance) of the nonaqueous electrolyte secondary battery 100 in the restraint state (state shown in FIG. 6) after the discharge amount measurement process (step S6) is completed. Measure. Specifically, the non-aqueous electrolyte secondary battery 100 is charged, and the battery voltage value is set to 3.6 V (SOC 40%). Thereafter, the non-aqueous electrolyte secondary battery 100 is discharged at a constant current of 20 A for 4 seconds, and the battery voltage value Vg at the end of discharge (moment of completion) is measured. Next, a value (= ΔV / 20) obtained by dividing the battery voltage change amount ΔV (= 3.6-Vg) changed by the discharge by the current value 20A is acquired as an IV resistance value (internal resistance value). A battery whose IV resistance value is out of the allowable range is removed as a defective product (for example, discarded).

Then, it progresses to step S8 (restraint cancellation | release process), and the restraint state of the nonaqueous electrolyte secondary battery 100 which finished the internal resistance measurement process (step S7) is cancelled | released. Specifically, the pressing jigs 30 and 40 that have been pressed with the nonaqueous electrolyte secondary battery 100 interposed therebetween are removed. In this way, the nonaqueous electrolyte secondary battery 100 is completed.
In addition, the nonaqueous electrolyte secondary battery 100 of this embodiment is used as a drive power source for a hybrid vehicle or an electric vehicle, for example.

(Leave test)
Next, a description will be given of a standing test performed in order to investigate the conditions (first predetermined time, second predetermined time, etc.) for accurately detecting a battery in which an internal short circuit has occurred in step S5 (self-discharge process). .

  Specifically, first, 40 batteries 100 (normal batteries in which no internal short circuit occurs) are prepared. Among these, about 20 batteries 100, a battery simulating an internal short circuit (hereinafter referred to as an internal short circuit battery) was manufactured by connecting a resistance element of 200 kΩ between the positive terminal part 191A and the negative terminal part 192A. . Thereafter, under the same leaving conditions as in step S5 (self-discharge process), 20 batteries 100 (hereinafter referred to as normal batteries) and 20 internal short-circuited batteries without internal short-circuiting are left to stand, and the voltage from the start of leaving is left. The amount of change was measured. The result is shown in FIG.

  In FIG. 7, the value of the battery having the smallest voltage change amount (reduction amount) among the 20 normal batteries is represented by ● (black circle). In addition, the value of the battery having the largest voltage change amount (decrease amount) among normal batteries is represented by ◯ (white circle). Further, among the internal short-circuit batteries, the value of the battery having the smallest voltage change amount (decrease amount) is represented by ◇ (white rhombus). In addition, the value of the battery with the largest voltage change amount (decrease amount) among the internal short-circuit batteries is represented by ◆ (black rhombus).

  From FIG. 7, it can be seen that, within 5 hours after the battery 100 is left untreated, the battery voltage value particularly decreases greatly and the variation in the voltage decrease amount is also large. For this reason, the leaving period (predetermined period) is set to within 7 days, for example, 5 days, and the battery voltage value at the start of leaving is subtracted from the battery voltage value at the start of leaving with reference to the battery voltage value at the start of leaving. According to the method of determining whether or not an internal short circuit has occurred in the battery depending on whether or not the battery voltage difference is equal to or greater than a predetermined threshold, it is not possible to accurately detect the battery in which the internal short circuit has occurred.

  More specifically, as shown in FIG. 7, when 120 hours (5 days) have passed since the start of standing, a battery having the largest voltage change amount (decrease amount) among normal batteries (indicated by a circle in FIG. 7), Among the internal short-circuit batteries, the battery with the smallest voltage change amount (decrease amount) (indicated by に お い て in FIG. 7) has the same amount of voltage decrease from the start of standing. Therefore, the neglected period (predetermined period) is set to 120 hours (5 days), and the voltage drop from the start of neglect (that is, the battery voltage difference obtained by subtracting the battery voltage value at the end of neglect from the battery voltage value at the start of neglect. ) Is greater than or equal to a predetermined threshold value, the method of determining the presence or absence of an internal short circuit has the largest voltage change amount (decrease amount) among normal batteries and the most voltage change amount among internal short circuit batteries ( It becomes difficult to distinguish from a battery having a small amount of decrease.

  In this way, if the period of initial voltage drop (especially, within 5 hours from the start of leaving) is included in the voltage drop measurement period, which is a short-circuit determination criterion, some normal batteries (those with a large voltage drop) However, the voltage drop amount does not show a clear difference from the voltage drop amount of the internal short circuit battery, and as a result, the internal short circuit battery cannot be accurately detected. For example, some normal batteries (those with a large voltage drop) may be erroneously determined as internal short-circuit batteries.

  On the other hand, the first predetermined time is set within a range of 5 to 72 hours, and the first voltage value Vb is detected (that is, 5 to 72 hours (first predetermined time after the start of leaving the battery 100). ), The first voltage value Vb that is the battery voltage value of the battery is detected), so that “in particular, the battery voltage value is greatly reduced and the variation in the voltage drop amount is large ( The period within 5 hours from the start of standing) can be excluded from the measurement period of the battery voltage difference ΔVbc, which is a short-circuit determination criterion. As a result, the above-described problems can be solved and a battery in which an internal short circuit has occurred can be detected with high accuracy.

  Here, the first predetermined time is set to, for example, 36 hours from the range of 5 to 72 hours, and the first voltage value Vb is detected (that is, when 36 hours have passed since the battery 100 is left unattended). The case where the first voltage value Vb which is the battery voltage value of the battery is detected) will be described. The graph of the battery voltage change amount at this time is shown in FIG.

  In FIG. 8, as in FIG. 7, the value of the battery having the smallest voltage change amount (reduction amount) among the 20 normal batteries is represented by ● (black circle). In addition, the value of the battery having the largest voltage change amount (decrease amount) among normal batteries is represented by ◯ (white circle). In addition, among the internal short-circuit batteries, the value of the battery having the smallest voltage change amount (decrease amount) is represented by ◇ (white rhombus). In addition, the value of the battery with the largest voltage change amount (decrease amount) among the internal short-circuit batteries is represented by ◆ (black rhombus).

As can be seen from a comparison between FIG. 7 and FIG. 8, in FIG. 8, the variation in the voltage drop amount is small in both the normal battery and the internal short-circuit battery, and the difference between the voltage drop amounts clearly appears.
Further, the first predetermined time is set within a range of 5 to 72 hours, and the first voltage value Vb is detected (that is, when 5 to 72 hours have elapsed since the start of leaving the battery 100), When the first voltage value Vb, which is a voltage value, is detected), as shown in FIG. 8, both the normal battery and the internal short-circuit battery have less variation in voltage drop, and the voltage drop between both The difference becomes clear. For this reason, it is possible to accurately detect a battery in which an internal short circuit has occurred by determining the first predetermined time within a range of 5 to 72 hours and detecting the first voltage value Vb.

  Further, from FIG. 8, the second predetermined time is set to 48 hours or more, and the second voltage value Vc is detected (that is, when 48 hours or more have elapsed since the first voltage value Vb was detected) By detecting the second voltage value Vc that is a voltage value) and measuring the battery voltage difference ΔVbc (= first voltage value Vb−second voltage value Vc), between the normal battery and the internal short-circuit battery, It can be seen that a clear difference appears in the battery voltage difference ΔVbc.

  Specifically, in the example shown in FIG. 8, the second voltage value Vc is detected when 48 hours or more have elapsed since the first voltage value Vb was detected (that is, when 84 hours or more have elapsed since the start of leaving). Then, among the normal batteries, the battery having the largest voltage change amount (reduction amount) (indicated by a circle in FIG. 8) and the battery having the smallest voltage change amount (reduction amount) among the internal short-circuit batteries (indicated by ◇ in FIG. 8). ), The difference in battery voltage difference ΔVbc (equal to the difference in voltage change) is 1 mV or more. That is, the difference between the battery voltage difference ΔVbc of the normal battery and the battery voltage difference ΔVbc of the internal short circuit battery is 1 mV or more.

  In the present application, among the normal batteries, the battery voltage difference ΔVbc of the battery having the largest voltage change amount (reduction amount) (indicated by “◯” in FIG. 8) and the voltage change amount (reduction amount) of the internal short-circuit battery are the smallest. The difference from the battery voltage difference ΔVbc of the battery (indicated by ◇ in FIG. 8) is also referred to as the minimum difference ΔVmin of the battery voltage difference ΔVbc.

  For example, when the second voltage value Vc is detected when 84 hours have elapsed since the first voltage value Vb was detected (that is, when 120 hours have elapsed since the start of leaving), the minimum difference ΔVmin of the battery voltage difference ΔVbc is To 1.6 mV. That is, the difference between the battery voltage difference ΔVbc of the normal battery and the battery voltage difference ΔVbc of the internal short circuit battery is 1.6 mV or more.

  Thus, a clear difference appears in the battery voltage difference ΔVbc between the normal battery and the internal short circuit battery, so that the battery in which the internal short circuit has occurred can be detected with high accuracy. In the example shown in FIG. 8, for example, by setting the threshold Tbc to 2 mV, a normal battery and an internal short-circuit battery can be clearly discriminated (a battery having a battery voltage difference ΔVbc of 2 mV or more is identified as an internal short-circuit battery). Therefore, it is possible to accurately detect a battery in which an internal short circuit has occurred.

  When the first predetermined time is set within the range of 5 to 72 hours to detect the first voltage value Vb, and the second predetermined time is set to 48 hours or more to detect the second voltage value Vc, However, as shown in FIG. 8, there is a clear difference in the battery voltage difference ΔVbc between the normal battery and the internal short circuit battery between the normal battery and the internal short circuit battery, and the minimum difference ΔVmin of the battery voltage difference ΔVbc increases. . For this reason, the first predetermined time is set within a range of 5 to 72 hours to detect the first voltage value Vb, and the second predetermined time is set to 48 hours or more to detect the second voltage value Vc, By determining whether or not there is an internal short circuit based on the battery voltage difference ΔVbc (= Vb−Vc), it is possible to accurately detect the battery in which the internal short circuit has occurred.

  Further, based on the result of the above-mentioned neglect test, a graph representing the relationship between the first predetermined time and the minimum difference ΔVmin of the battery voltage difference ΔVbc was created. This is shown in FIG. Note that the data shown in FIG. 9 is data when the second voltage value Vc is detected when 120 hours have elapsed since the start of leaving, with the leaving period being 120 hours (5 days).

  By the way, in order to detect the internal short-circuit battery with high accuracy based on the battery voltage difference ΔVbc (= Vb−Vc), it is preferable that the minimum difference ΔVmin of the battery voltage difference ΔVbc is as large as possible. Specifically, when the minimum difference ΔVmin is 0.8 mV or more, it is possible to accurately distinguish between a normal battery and an internal short-circuit battery. Furthermore, when the minimum difference ΔVmin is 1.0 mV or more, a normal battery and an internal short-circuit battery can be distinguished with extremely high accuracy.

  Therefore, when FIG. 9 is examined, it is found that the minimum difference ΔVmin is 0.8 mV or more when the first predetermined time is in the range of 0.5 to 72 hours. Therefore, it can be said that by detecting the first voltage value Vb by setting the first predetermined time within a range of 5 to 72 hours, it is possible to accurately detect a battery in which an internal short circuit has occurred.

  Further, since the data shown in FIG. 9 is data when the second voltage value Vc is detected when 120 hours have passed since the start of being left standing, the first predetermined time is in the range of 0.5 to 72 hours. The second predetermined time is at least 48 hours. Therefore, it can be said that it is preferable to set the second predetermined time to 48 hours or longer in order to accurately detect a battery in which an internal short circuit has occurred.

  Furthermore, when FIG. 9 is examined, it is found that the minimum difference ΔVmin is 1.0 mV or more when the first predetermined time is in the range of 24 to 60 hours. Therefore, it can be said that a battery having an internal short circuit can be detected with higher accuracy by determining the first predetermined time within a range of 24 to 60 hours and detecting the first voltage value Vb.

  Further, since the data shown in FIG. 9 is data when the second voltage value Vc is detected when 120 hours have passed since the start of leaving, when the first predetermined time is within a range of 24 to 60 hours, 2 The predetermined time is at least 60 hours. Therefore, it can be said that the second predetermined time is preferably 60 hours or more in order to detect the internal short-circuit battery with higher accuracy.

  On the other hand, the data shown in FIG. 9 is data when the “predetermined period” in which the battery is left is within 7 days, specifically, when the “predetermined period” is 120 hours (5 days). Thus, even if the “predetermined period” in which the battery is left is shortened to within 7 days, as described above, the first predetermined time is set within the range of 5 to 72 hours, and the first voltage value Vb is detected. Furthermore, by detecting the second voltage value Vc by setting the second predetermined time to 48 hours or longer, it is possible to accurately detect a battery in which an internal short circuit has occurred (see FIG. 9). Therefore, in the present embodiment, by setting the “predetermined period” during which the battery is left to be within 7 days, the period of the self-discharge process can be shortened, and as a result, the production efficiency of the battery can be improved.

  In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above embodiment, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.

  For example, although step S2 (battery restraint process) and step S8 (restraint release process) are provided in the embodiment, a nonaqueous electrolyte secondary battery may be manufactured without providing these processes. That is, you may make it perform the process of step S3-S7, without pinching the nonaqueous electrolyte secondary battery 100 produced in the assembly | attachment process (step S1) with the pressing jigs 30 and 40, and making it a restraint state.

100 Non-aqueous electrolyte secondary battery (lithium ion secondary battery)
DESCRIPTION OF SYMBOLS 110 Electrode body 120 Negative electrode plate 121 Negative electrode active material layer 127 Negative electrode active material 128 Negative electrode current collecting plate 130 Positive electrode plate 131 Positive electrode active material layer 137 Positive electrode active material 138 Positive electrode current collecting plate 150 Separator 160 Nonaqueous electrolyte solution 180 Battery case

Claims (3)

A non-aqueous electrolyte secondary battery manufacturing method comprising: a self-discharge step of self-discharging the battery by leaving the non-aqueous electrolyte secondary battery containing the electrode body and the non-aqueous electrolyte in a battery case for a predetermined period of time In
The self-discharge process is
The first voltage value Vb, which is the battery voltage value of the battery when the first predetermined time has elapsed since the start of the leaving of the battery, is detected, and further, the second predetermined value from when the first voltage value Vb is detected. A battery voltage difference ΔVbc obtained by subtracting the second voltage value Vc from the first voltage value Vb by detecting the second voltage value Vc that is the battery voltage value of the battery when time has elapsed is equal to or greater than a predetermined threshold value. Is a step of determining that an internal short circuit has occurred in the battery,
The non-aqueous electrolyte secondary that detects the first voltage value Vb and the second voltage value Vc by setting the first predetermined time within a range of 5 to 72 hours and the second predetermined time being 48 hours or more. Battery manufacturing method. It is a manufacturing method of the nonaqueous electrolyte secondary battery according to claim 1,
In the self-discharge process,
A non-aqueous electrolyte secondary that detects the first voltage value Vb and the second voltage value Vc by setting the first predetermined time in a range of 24 to 60 hours and setting the second predetermined time to 60 hours or more. A battery manufacturing method. It is a manufacturing method of the nonaqueous electrolyte secondary battery according to claim 1 or 2,
In the self-discharge step, a method for producing a non-aqueous electrolyte secondary battery, wherein the predetermined period in which the battery is left is within 7 days.

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