JP2012221782A - 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: A manufacturing method of a nonaqueous electrolyte secondary battery comprises: an electrode body formation step of forming an electrode body having a positive electrode and a negative electrode; and a self-discharge step of self-discharging the nonaqueous electrolyte secondary battery including the electrode body and a battery case housing the electrode body by leaving the battery unattended for a prescribed period. In the electrode body formation step (step S1), there is formed an electrode body whose capacity ratio (B/A) of a capacity A of the positive electrode to a capacity B of the negative electrode is less than or equal to 1.4. In the self-discharge step (step S6), the battery unattended is left for the prescribed period under a temperature environment of 20°C or lower.

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 producing a nonaqueous electrolyte secondary battery (for example, electrode body forming process or assembly process), conductive foreign matters such as metal powder may be mistakenly mixed in the battery (in the electrode body). . When such a battery is used, dendrites derived from conductive foreign matter are generated and an internal short circuit occurs (the positive electrode and the negative electrode electrically insulated by the separator are electrically connected through the dendrite). There is.

  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

  By the way, in recent years, nonaqueous electrolyte secondary batteries having a positive / negative electrode capacity ratio (B / A) of 1.4 or more have been developed. By setting the positive / negative electrode capacity ratio (B / A) to 1.4 or more, the internal resistance of the battery can be reduced, and Li is deposited on the negative electrode surface during charging (particularly during high-rate charging). This can be suppressed.

  However, when the capacity ratio (B / A) of the positive and negative electrodes is 1.4 or more, the method of Patent Document 1 has a large variation in the amount of change (decrease) in battery voltage, and conductive foreign matter is mixed in. There is a possibility that the existing battery (the battery in which the internal short circuit occurs) cannot be accurately detected. Specifically, variation in the amount of battery voltage (amount of decrease) between normal batteries (which does not contain conductive foreign matter and does not cause internal short-circuiting) becomes extremely large. There is a possibility that it cannot be accurately detected whether or not a short circuit has occurred. Specifically, among the normal batteries, the battery with a large voltage drop during the leaving period has the same voltage drop as the battery in which an internal short circuit has occurred (a battery with a small voltage drop during the leaving period) In some cases, there was no clear difference in voltage drop (battery voltage difference ΔVbc) between these batteries. For this reason, there is a possibility that a battery in which an internal short circuit has occurred cannot be accurately detected.

  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. .

  According to one embodiment of the present invention, an electrode body forming step for forming an electrode body having a positive electrode and a negative electrode, and a nonaqueous electrolyte secondary battery in which the electrode body and the nonaqueous electrolyte are contained in a battery case are left for a predetermined period. Thus, in the method of manufacturing a non-aqueous electrolyte secondary battery comprising a self-discharge step of self-discharging the battery, in the electrode body forming step, a capacity ratio between the capacity A of the positive electrode and the capacity B of the negative electrode ( A method of manufacturing a non-aqueous electrolyte secondary battery in which an electrode body having a B / A) of 1.4 or more is formed and the battery is left in the self-discharge step at a temperature environment of 20 ° C. or lower for a predetermined period of time. is there.

  The above-described manufacturing method includes a self-discharge process in which a non-aqueous electrolyte secondary battery in which an electrode body and a non-aqueous electrolyte are accommodated in a battery case is left for a predetermined period to self-discharge the battery. In this self-discharge step, the battery voltage obtained by subtracting the leaving end voltage value Vc, which is the battery voltage value when the battery is left for a predetermined period, from the leaving start voltage value Vb, which is the battery voltage value when starting to leave the battery, is determined. If the difference ΔVbc is greater than or equal to a predetermined threshold, it is determined that an internal short circuit has occurred in the battery. A battery determined to have an internal short circuit is removed, for example, as a defective product (for example, discarded).

  Further, in the above-described manufacturing method, in the electrode body forming step, an electrode body having a capacity ratio (B / A) between the positive electrode capacity A and the negative electrode capacity B of 1.4 or more is manufactured. By setting the capacity ratio (B / A) of the positive and negative electrodes to 1.4 or more, the internal resistance of the battery can be reduced, and Li can be formed on the negative electrode surface during charging (particularly during high rate charging). Precipitation can be suppressed.

  By the way, in the conventional method (for example, Patent Document 1), when a battery including an electrode body having a positive / negative electrode capacity ratio (B / A) of 1.4 or more is self-discharged, a normal battery (internal short circuit does not occur). Even between the batteries, the variation in the amount of change (decrease amount) in the battery voltage increased, and it was not possible to accurately detect whether an internal short circuit occurred. Specifically, a battery with a large battery voltage change amount among normal batteries has a voltage drop amount similar to that of an internal short-circuited battery (a battery with a small battery voltage change amount). In some cases, there was no clear difference in the voltage drop (battery voltage difference ΔVbc). For this reason, a battery in which an internal short circuit has occurred cannot be detected with high accuracy.

  The reason why the variation (the amount of decrease) in the battery voltage varies greatly is considered as follows. In a non-aqueous electrolyte secondary battery in which the capacity ratio (B / A) of the positive and negative electrodes is increased to 1.4 or more, SEI (Solid Electrolyte Interface) generation reaction is easily promoted on the negative electrode surface during the self-discharge period. As a result, the amount of change (decrease amount) in battery voltage tends to increase. For this reason, the difference in the amount of change (decrease amount) in the battery voltage between the batteries tends to increase, and as a result, the variation in the amount of change (decrease amount) in the battery voltage increases.

  On the other hand, in the above-described manufacturing method, the battery is left for a predetermined period in a temperature environment of 20 ° C. or lower in the self-discharge process. A non-aqueous electrolyte secondary battery having a positive / negative electrode capacity ratio (B / A) increased to 1.4 or more is allowed to stand in a temperature environment of 20 ° C. or less and self-discharge, thereby allowing normal batteries to The variation in the battery voltage change amount (decrease amount) can be reduced. As a result, a clear difference appears in the voltage drop amount (battery voltage difference ΔVbc) between the normal battery and the internal short-circuit battery. Thereby, the battery in which the internal short circuit has arisen can be detected accurately.

  The reason why the variation in the battery voltage change amount (decrease amount) can be reduced is considered as follows. By setting the environmental temperature at which the battery is left to be 20 ° C. or less, it is considered that the SEI generation reaction during the self-discharge period can be suppressed, and thereby the change amount (decrease amount) of the battery voltage can be reduced. As a result, it is considered that the variation in the battery voltage change amount (decrease amount) can be reduced.

  Furthermore, the method for manufacturing a non-aqueous electrolyte secondary battery includes a capacity measuring step for measuring part or all of the battery capacity for the battery that has finished the self-discharge step, and in the self-discharge step, A non-aqueous electrolyte secondary battery manufacturing method in which the battery is allowed to stand for the predetermined period in a temperature environment within a range of 10 to 20 ° C is preferable.

  The manufacturing method described above includes a capacity measuring step of measuring part or all of the battery capacity of the battery that has finished the self-discharge process. This capacity | capacitance measurement process is a process for confirming whether the coating amount of a positive mix layer and a negative mix layer is appropriate. Specifically, when the coating amount of the electrode mixture layer (the positive electrode mixture layer and the negative electrode mixture layer) is greatly deviated from the reference value (excess or excessive), the battery capacity deviates greatly from the reference value ( Will be out of tolerance). Therefore, in the capacity measurement step, it is determined whether a part or all of the measured values of the battery capacity are within the allowable range. If the measured value is outside the allowable range, the battery is coated with the electrode mixture layer. It is determined that the work is defective. A battery determined to be defective in coating is removed, for example, as a defective product (for example, discarded).

  However, in the case of a battery including an electrode body with a positive / negative electrode capacity ratio (B / A) of 1.4 or more, after self-discharge in the self-discharge process, when the battery capacity is measured in the capacity measurement process, a normal battery ( Even between batteries in which the coating amount of the electrode mixture layer is an appropriate amount), the battery capacity varies greatly, and it is sometimes impossible to accurately detect a coating defective battery. That is, the battery capacity may fluctuate (decrease) greatly during the self-discharge process (during the standing period), and as a result, the battery capacity may vary greatly.

  As a result of studies by the present inventor, it has been found that when the battery is left under a temperature environment higher than 20 ° C. in the self-discharge process, particularly, the battery capacity varies greatly. In addition, it has been found that when the battery is left in a temperature environment lower than 10 ° C. in the self-discharge process, the battery capacity varies greatly.

  On the other hand, in the manufacturing method described above, the battery is left for a predetermined period in a temperature environment within a range of 10 to 20 ° C. in the self-discharge process. For non-aqueous electrolyte secondary batteries having a positive / negative electrode capacity ratio (B / A) as large as 1.4 or more, the battery standing temperature (environmental temperature) in the self-discharge process should be within the range of 10 to 20 ° C. As a result, it is possible to suppress the variation in battery capacity during the self-discharge period (during the leaving period). Thereby, in the capacity | capacitance measurement process after a self-discharge process, a coating defect battery can be detected accurately.

  The reason why the variation in battery capacity increases when the battery is left in a temperature environment higher than 20 ° C. in the self-discharge process is considered as follows. In a non-aqueous electrolyte secondary battery in which the capacity ratio (B / A) of the positive and negative electrodes is increased to 1.4 or more, the SEI formation reaction is easily promoted on the surface of the negative electrode during the self-discharge process (during the standing period) (accordingly) , Li is likely to be consumed), and along with this, the battery capacity may be greatly reduced. As a result, it is considered that the variation in battery capacity tends to increase.

  Furthermore, in any one of the above non-aqueous electrolyte secondary battery manufacturing methods, in the electrode body forming step, the non-aqueous electrolyte secondary battery for producing an electrode body having the capacity ratio (B / A) of 1.7 or more is prepared. A secondary battery manufacturing method is preferable.

In the above-described manufacturing method, in the electrode body forming step, an electrode body is produced in which the capacity ratio (B / A) between the positive electrode capacity A and the negative electrode capacity B is 1.7 or more. By setting the capacity ratio (B / A) of the positive and negative electrodes to 1.7 or more, the internal resistance of the battery can be reduced, and Li can be formed on the negative electrode surface during charging (particularly during high rate charging). Precipitation can be effectively suppressed.
However, when a conventional method (for example, Patent Document 1) is used, in a non-aqueous electrolyte secondary battery in which the capacity ratio (B / A) of positive and negative electrodes is increased to 1.7 or more, in particular, the amount of change in battery voltage ( There was a tendency for the variation in the amount of decrease to increase.

  On the other hand, in the manufacturing method described above, as described above, the battery is left for a predetermined period in a temperature environment of 20 ° C. or lower in the self-discharge process. Thereby, it is possible to reduce the variation in the change amount (decrease amount) of the battery voltage during the self-discharge period (during the leaving period) between the normal batteries. As a result, a clear difference appears in the voltage drop amount (battery voltage difference ΔVbc) between the normal battery and the internal short-circuit battery. As a result, even for a non-aqueous electrolyte secondary battery in which the capacity ratio (B / A) of the positive and negative electrodes is increased to 1.7 or more, it is possible to accurately detect a battery in which an internal short circuit occurs.

  Note that the positive / negative electrode capacity ratio (B / A) is preferably 1.9 or less. This is because when the capacity ratio (B / A) of the positive and negative electrodes is larger than 1.9, the amount of Li consumed by the SEI generation reaction increases, and the battery capacity decreases.

  Furthermore, in any one of the above non-aqueous electrolyte secondary battery manufacturing methods, an initial charge / discharge step of initially charging / discharging the non-aqueous electrolyte secondary battery before the self-discharge step, and the initial charge / discharge step It is preferable to provide a method for producing a non-aqueous electrolyte secondary battery comprising: an aging process in which the battery that has finished is aged at a predetermined temperature for a predetermined time.

  About a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery can be activated by performing an initial charging / discharging process and an aging process prior to a self-discharge process. Therefore, in the self-discharge step, the activated nonaqueous electrolyte secondary battery can be self-discharged to detect a battery in which an internal short circuit has occurred.

  By the way, in the process of producing a nonaqueous electrolyte secondary battery (for example, electrode body forming process or assembly process), conductive foreign matters such as metal powder may be mistakenly mixed in the battery (in the electrode body). . In such a battery, dendrite derived from conductive foreign matters such as metal powder is generated in the aging process, 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. Connected).

  On the other hand, in the manufacturing method of the above-mentioned nonaqueous electrolyte secondary battery, the self-discharge process is provided after the aging process. In addition, in the self-discharge process, as described above, it is possible to accurately detect a battery in which an internal short circuit has occurred. Therefore, in the above manufacturing method, a battery in which an internal short circuit has occurred in the aging process can be appropriately detected.

It is a perspective view of the nonaqueous electrolyte secondary battery concerning an embodiment. It is a perspective view of the positive electrode of the nonaqueous electrolyte secondary battery. It is a perspective view of the negative electrode of the nonaqueous electrolyte secondary battery. It is an expanded sectional view of the same negative electrode, 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. The graph which shows the relationship between the leaving temperature (environment temperature of a self-discharge process) and the maximum difference (size of variation) of battery voltage difference ΔVbc for a battery having a positive / negative electrode capacity ratio (B / A) value of 1.8. It is. It is a graph which shows the relationship between leaving temperature (environment temperature of a self-discharge process) and the maximum difference (size of variation) of battery voltage difference (DELTA) Vbc about the battery from which the value of positive / negative electrode capacity ratio (B / A) differs. It is a graph which shows the relationship between a leaving temperature (environment temperature of a self-discharge process) and battery capacity variation about the battery which made the value of positive / negative electrode capacity ratio (B / A) 1.8. It is a graph which shows the relationship between standing temperature (environment temperature of a self-discharge process) and battery capacity variation about the battery from which the value of positive / negative electrode capacity ratio (B / A) differs. It is a graph which shows the relationship between the value of positive / negative electrode capacity ratio (B / A) and the ratio of average battery capacity (ratio with respect to the battery of positive / negative electrode capacity ratio 1.2).

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 130, a negative electrode 120, and a separator 150. The separator 150 is made of polyethylene, and is interposed between the positive electrode 130 and the negative electrode 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 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.

  In addition, a plate-like positive electrode current collecting member 191 bent in a crank shape is welded to the positive electrode 130 of the electrode body 110 (see FIG. 1). Further, the negative electrode 120 is welded with a plate-shaped negative electrode current collecting member 192 bent in a crank shape. 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 strip-shaped positive electrode 130 and a negative electrode 120 are wound in a flat shape via a strip-shaped separator 150 (see FIG. 1). Specifically, the strip-shaped positive electrode 130, the negative electrode 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 (see FIGS. 1 to 4). . In this electrode body 110, the positive electrode mixture layer 131 of the positive electrode 130 and the negative electrode mixture layer 121 of the negative electrode 120 are opposed to each other with the separator 150 interposed therebetween (see FIG. 4).

As shown in FIG. 2, the positive electrode 130 has a strip shape extending in the longitudinal direction DA. The positive electrode current collector plate 138 made of aluminum foil and strips extending in the longitudinal direction DA on both main surfaces of the positive electrode current collector plate 138. And two positive electrode mixture layers 131, 131 disposed on the surface. The positive electrode mixture layer 131 includes a positive electrode active material 137, a conductive material made of acetylene black, and PVdF (binder) in a weight ratio of 88: 10: 2. Note that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ is used as the positive electrode active material 137.

  Further, as shown in FIG. 3, the negative electrode 120 includes a negative electrode current collector plate 128 made of a copper foil in a strip shape extending in the longitudinal direction DA, and both main surfaces 128F and 128F of the negative electrode current collector plate 128 in the longitudinal direction. It has two negative electrode mixture layers 121 and 121 arranged in a strip shape extending to DA. The negative electrode mixture layer 121 includes a negative electrode active material 127, SBR (styrene butadiene rubber), CMC, and (carboxymethylcellulose) 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 mixture 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 mixture layer 121 includes a facing portion 122 that faces the positive electrode mixture layer 131 through the separator 150, and a separator 150. It consists of the non-facing part 123 in which the opposing positive mix layer 131 does not exist. Specifically, the negative electrode mixture layer 121 has a larger area than the positive electrode mixture layer 131, and the non-opposing portion 123 is positioned around the opposed portion 122. Note that the position of the boundary between the non-facing portion 123 and the facing portion 122 in the negative electrode mixture layer 121 is determined when the electrode body 110 is formed by winding the negative electrode 120, the separator 150, and the positive electrode 130. Further, in FIG. 4, for reference, the positions of the positive electrode 130 and the separator 150 when the electrode body 110 is formed are indicated by a two-dot chain line.

  In the present embodiment, the capacity ratio of the capacity A of the positive electrode 130 and the capacity B of the negative electrode 120 (negative electrode capacity B / positive electrode capacity A) is 1.4 or more. By setting the positive / negative electrode capacity ratio (B / A) to 1.4 or more, the internal resistance of the battery can be reduced, and Li is deposited on the negative electrode surface during charging (particularly during high-rate charging). This can be suppressed. The capacity ratio (B / A) between the positive electrode capacity A and the negative electrode capacity B is the capacity ratio between the positive electrode mixture layer 131 and the facing portion 122 of the negative electrode mixture layer 121. This capacity ratio is adjusted by increasing or decreasing the thickness of the negative electrode mixture layer 121 (opposing portion 122) (that is, the amount of negative slurry applied later).

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 S1 (electrode body forming step), the electrode body 110 having the positive electrode 130 and the negative electrode 120 is formed. Specifically, first, the positive electrode active material 137, acetylene black, and PVdF (binder) are mixed at a weight ratio of 88: 10: 2, and NMP (solvent) is mixed therewith to form a positive electrode slurry. Was made. Next, this positive electrode slurry was applied to the surface of a positive electrode current collector plate 138 made of aluminum foil, dried, and then pressed. Thereby, the positive electrode 130 was obtained.

  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 coated 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 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 mixture 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 metal oxide insulating layer 129 can be formed by applying this paste to the surface of the negative electrode mixture layer 121 and drying it. Note that the thickness of the metal oxide insulating layer 129 is preferably 2 to 8 μm.

  In this embodiment, the capacity ratio (negative electrode capacity B / positive electrode capacity A) of the positive electrode capacity A and the negative electrode capacity B is 1.4 or more. Note that the value of the capacity ratio (B / A) between the positive electrode capacity A and the negative electrode capacity B is the capacity ratio between the positive electrode mixture layer 131 and the facing portion 122 of the negative electrode mixture layer 121. This capacity ratio is adjusted by increasing or decreasing the thickness of the negative electrode mixture 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 120 and the positive electrode 130. The separator 150, the negative electrode 120, the separator 150, and the positive electrode 130 are stacked in this order so that the positive electrode mixture layer 131 of the positive electrode 130 faces the facing portion 122 of the negative electrode mixture layer 121 of the negative electrode 120 through the separator 150. Wind (see FIG. 4). In this way, a wound electrode body 110 was formed.

Next, the process proceeds to step S2 (assembly process), and a battery in which the electrode body 110 and the non-aqueous electrolyte 160 are housed in the battery case 180 is manufactured.
Specifically, the negative electrode current collecting member 192 is welded to the negative electrode 120 (negative electrode current collecting plate 128), and the positive electrode current collecting member 191 is welded to the positive electrode 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 S3 (battery restraint process) (see FIG. 5), and the nonaqueous electrolyte secondary battery produced in the above assembly process (step S2) 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 S4 (initial charging / discharging process) (refer FIG. 5), and charge / discharge is performed about the nonaqueous electrolyte secondary battery 100 of the state (state shown in FIG. 6) restrained by the pressing jigs 30 and 40. . Specifically, charging is performed at a constant current of 1 C (5 A) until the battery voltage value reaches 4.1 V, and then charging is performed while the battery voltage value is maintained at 4.1 V. The charging current value is 0.1 A. When it drops to, charging ends. Next, the battery is discharged at a constant current of 1 C until the battery voltage reaches 3.92V. Next, the battery is charged with a constant current of 1 C until the battery voltage value reaches 3.97 V, and then charged while holding the battery voltage value at 3.97 V. When the charging current value decreases to 0.1 A To finish charging.

  Note that 1C is a current value at which discharge is completed in 1 hour after a battery having a rated capacity value (nominal capacity value) is discharged at a constant current. 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 S5 (aging process), and the nonaqueous electrolyte secondary battery 100 in the restraint state (state shown in FIG. 6) after the initial charge / discharge (the process of step S4) is set to a predetermined temperature (for example, 60 ° C.). ) And aged for a certain time (for example, 20 hours).

  By the way, in step S1 (electrode body forming process) and assembly process (step S2), metal powder (such as Cu powder) may be mixed in the electrode body 110 by mistake. In such a battery, in the aging process, dendrites derived from metal powder are generated and an internal short circuit occurs (the positive electrode 130 and the negative electrode 120 that are electrically insulated by the separator 150 are electrically connected through the dendrite). Sometimes. For this reason, in step S6 (self-discharge process) 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 S6 (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 S5) is completed for a predetermined period (for example, 10 days). Let it self-discharge by leaving it alone.

  In step S6 (self-discharge process), the battery voltage value when the non-aqueous electrolyte secondary battery 100 is left standing (left standing voltage value Vb) and the battery voltage value when the predetermined period is left standing (leaving end) Voltage value Vc). Further, in step S6 (self-discharge process), a battery voltage difference ΔVbc (= Vb−Vc) obtained by subtracting the leaving end voltage value Vc from the leaving start voltage value Vb is calculated, and the battery voltage difference ΔVbc is equal to or greater than a predetermined threshold 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.

  In a battery in which an internal short circuit has occurred, since the amount of self-discharge due to neglect is larger than a battery in which an internal short circuit has not occurred (normal battery), the battery voltage value becomes smaller, and the battery voltage difference ΔVbc before and after the neglect is also growing. Therefore, based on the battery voltage difference ΔVbc before and after being left, it can be determined whether or not an internal short circuit has occurred in the battery. Therefore, in step S6 (self-discharge process), it is determined whether or not an internal short circuit has occurred in the nonaqueous electrolyte secondary battery 100 depending on whether or not the battery voltage difference ΔVbc is equal to or greater than a predetermined threshold value Tbc. A battery determined to have an internal short circuit is removed as a defective product (for example, discarded).

  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.

  By the way, in the conventional method (for example, Patent Document 1), when a battery including an electrode body having a positive / negative electrode capacity ratio (B / A) of 1.4 or more is self-discharged, a normal battery (internal short circuit does not occur). Even among the batteries, the variation in the battery voltage change amount (decrease amount) became large, and the battery in which an internal short circuit occurred could not be detected with high accuracy. Specifically, a battery with a large battery voltage change amount among normal batteries has a voltage drop amount similar to that of an internal short-circuited battery (a battery with a small battery voltage change amount). In some cases, there was no clear difference in the voltage drop (battery voltage difference ΔVbc). For this reason, a battery in which an internal short circuit has occurred cannot be detected with high accuracy.

  In contrast, in the self-discharge process (step S6) of the present embodiment, the battery 100 is left for a predetermined period in a temperature environment of 20 ° C. or lower. By allowing the non-aqueous electrolyte secondary battery 100 having a positive / negative electrode capacity ratio (B / A) value of 1.4 or more to stand in a temperature environment of 20 ° C. or less and self-discharge, The variation in the battery voltage change amount (decrease amount) can be reduced. As a result, a clear difference appears in the voltage drop amount (battery voltage difference ΔVbc) between the normal battery and the internal short-circuit battery. Thereby, the battery in which the internal short circuit has arisen can be detected accurately.

  The reason why the variation in the battery voltage change amount (decrease amount) can be reduced is considered as follows. By setting the environmental temperature at which the battery 100 is left to 20 ° C. or less, it is possible to suppress the SEI generation reaction during the self-discharge period (during the stand-by period), thereby reducing the battery voltage change amount (reduction amount). I think I can do it. As a result, it is considered that the variation in the battery voltage change amount (decrease amount) can be reduced.

  Next, the process proceeds to step S7 (capacity measurement step), and the battery capacity of the non-aqueous electrolyte secondary battery 100 determined in step S6 that no internal short-circuit has occurred (normal) in a temperature environment of 25 ° C. taking measurement.

  This capacity measurement process (step S7) is a process for confirming whether or not the coating amounts of the positive electrode mixture layer 131 and the negative electrode mixture layer 121 in step S2 (assembly process) are appropriate. Specifically, when the coating amount of the electrode mixture layer (the positive electrode mixture layer 131 and the negative electrode mixture layer 121) is greatly deviated from the reference value (excessive or too small), the battery capacity is greatly increased from the reference value. It will deviate (out of the allowable range). Therefore, in the capacity measurement step (step S7), it is determined whether or not the measured value of the battery capacity is within the allowable range. If the measured value is outside the allowable range, the battery is in contact with the electrode mixture layer (positive electrode composite). It is determined that the material layer 131 and the negative electrode mixture layer 121) are poorly coated (the amount of coating is inappropriate).

  Specifically, first, the battery 100 is charged with a constant current of 1 C (5 A) until the battery voltage value reaches 4.1 V (SOC 100%), and then the battery voltage value is maintained at 4.1 V. Charging is performed, and charging is terminated when the charging current value decreases to 0.1 A. Next, the battery 100 is discharged at a constant current of 1 C until the battery voltage value reaches 3.0 V (SOC 0%). The amount of electricity discharged Q1 at this time is measured as the battery capacity. A battery whose discharge electricity quantity Q1 (battery capacity) is out of the allowable range is determined as a coating failure and is removed as a defective product (for example, discarded).

In step S7 (capacity measurement step), the nonaqueous electrolyte secondary battery 100 remains in a state of being restrained by the pressing jigs 30 and 40 (the state shown in FIG. 7).
Also, SOC is an abbreviation for State Of Charge.

  Next, the process proceeds to step S8 (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 capacity measurement process (step S7) is completed. taking measurement. 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 S9 (restraint cancellation | release process), and the restraint state of the nonaqueous electrolyte secondary battery 100 which finished the internal resistance measurement process (step S8) 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.

Example 1
In Example 1, in step S1 (electrode body forming step), the capacity ratio (negative electrode capacity B / positive electrode capacity A) of the positive electrode capacity A and the negative electrode capacity B is 1.7 or more (specifically, 1.8 An electrode body 110 was prepared. By setting the capacity ratio (B / A) of the positive and negative electrodes to 1.7 or more, the internal resistance of the battery can be reduced, and Li can be formed on the negative electrode surface during charging (particularly during high rate charging). Precipitation can be effectively suppressed.
In the self-discharge process (step S6), the environmental temperature in which the battery 100 is left is set to a temperature within the range of 10 to 20 ° C. (specifically, 20 ° C.).

(Self-discharge test)
Next, the self-discharge test will be described. This self-discharge test was conducted in order to investigate the relationship between the standing temperature (environment temperature of the self-discharge process) and the variation in the amount of change (decrease amount) in the battery voltage during the self-discharge period (during the standing period).

  Specifically, first, 140 batteries that have undergone the above-described steps S1 to S5 are prepared. In step S1, the capacity ratio of the positive electrode capacity A and the negative electrode capacity B (negative electrode capacity B / positive electrode capacity A) is set to 1.8 as in the first embodiment. These batteries were divided into seven groups of 20 pieces, and the self-discharge was performed by leaving the batteries to stand for 10 days with different stand temperatures (environmental temperatures in the self-discharge process) for each group.

  Specifically, the 20 batteries of the first group were self-discharged by being left for 10 days in a temperature environment of 5 ° C. (standing temperature). The 20 batteries of the second group self-discharged by being left for 10 days in a temperature environment of 10 ° C. The 20 batteries of the third group self-discharged by being left for 10 days in a temperature environment of 15 ° C. The 20 batteries of the fourth group were self-discharged by being left for 10 days in a temperature environment of 20 ° C. The 20 batteries of the fifth group self-discharged by being left for 10 days in a temperature environment of 22 ° C. Sixth group of 20 batteries were self-discharged by being left for 10 days in a temperature environment of 25 ° C. The 20 batteries of the seventh group self-discharged by being left for 10 days in a temperature environment of 30 ° C.

In this self-discharge test, in each group (thus, each leaving temperature), for each battery, the battery voltage value at the time of starting to stand (leaving start voltage value Vb) and when the standing for 10 days is finished. The battery voltage value (standby end voltage value Vc) was measured. Further, a battery voltage difference ΔVbc (= Vb−Vc) obtained by subtracting the leaving end voltage value Vc from the leaving start voltage value Vb was calculated. In each group (each standing temperature), the value of the battery voltage difference ΔVbc of the battery having the smallest battery voltage difference ΔVbc is subtracted from the value of the battery voltage difference ΔVbc of the battery having the largest battery voltage difference ΔVbc. A value (this value is referred to as the maximum difference of the battery voltage difference ΔVbc) was calculated. These results are shown in the graph of FIG.
In addition, it has confirmed that all the 140 batteries which performed the self-discharge test are normal batteries in which the internal short circuit has not arisen.

  FIG. 7 shows the difference between the standing temperature (environment temperature of the self-discharge process) and the maximum difference (size of variation) of the battery voltage difference ΔVbc for a battery having a positive / negative electrode capacity ratio (B / A) value of 1.8. It is a graph which shows a relationship. It can be said that the greater the maximum difference of the battery voltage difference ΔVbc, the greater the variation in the battery voltage change amount (decrease amount) during the self-discharge period (during the standing period).

  Accordingly, when the results shown in FIG. 7 are examined, when the battery is left to self-discharge in a temperature environment of 20 ° C. or lower, the amount of change in battery voltage (battery voltage difference ΔVbc) during the self-discharge period (during the leave period). It can be seen that the maximum difference is extremely small. That is, when the leaving temperature is set to 20 ° C. or less, the variation in the battery voltage change amount (battery voltage difference ΔVbc) is reduced between normal batteries.

  On the other hand, when the battery is left to self-discharge in a temperature environment higher than 20 ° C., the maximum difference in the amount of change in battery voltage (battery voltage difference ΔVbc) during the self-discharge period (during the storage period) may increase. Recognize. That is, when the leaving temperature is higher than 20 ° C., the variation in the battery voltage change amount (battery voltage difference ΔVbc) increases even between normal batteries.

  From the above results, the non-aqueous electrolyte secondary battery in which the capacity ratio (B / A) of the positive and negative electrodes is increased to 1.8 is left to stand in a temperature environment of 20 ° C. or lower to be self-discharged. It can be said that variation in the amount of change (decrease amount) can be reduced.

  In addition, in comparison with the above test battery (battery with B / A value of 1.8), 140 batteries each having different positive / negative electrode capacity ratio (B / A) values were prepared. . Specifically, a battery having positive and negative electrode capacity ratios (B / A) of 1.2, 1.3, 1.4, 1.6, 1.7, 1.9, and 2.0 is used. 140 pieces were prepared for each. The batteries of each capacity ratio (B / A) are divided into 7 groups of 20 pieces, and the self-discharge is performed by leaving the storage temperature (environment temperature of the self-discharge process) for each group for 10 days. Went. The standing temperature is different from 5 ° C., 10 ° C., 15 ° C., 20 ° C., 22 ° C., 25 ° C., and 30 ° C. as described above.

Also in this self-discharge test, the stand-by start voltage value Vb and the stand-by end voltage value Vc were measured for each battery in each group (thus, each stand temperature). Further, a battery voltage difference ΔVbc (= Vb−Vc) obtained by subtracting the leaving end voltage value Vc from the leaving start voltage value Vb was calculated. In each group (each standing temperature), the value of the battery voltage difference ΔVbc of the battery having the smallest battery voltage difference ΔVbc is subtracted from the value of the battery voltage difference ΔVbc of the battery having the largest battery voltage difference ΔVbc. The value (maximum difference in battery voltage difference ΔVbc) was calculated. These results are shown in the graph of FIG. FIG. 8 also shows the test results of the battery with a positive / negative electrode capacity ratio (B / A) of 1.8.
Moreover, it has confirmed that all the batteries which performed the self-discharge test are normal batteries in which the internal short circuit has not arisen.

FIG. 8 is a graph showing the relationship between the standing temperature (environment temperature of the self-discharge process) and the maximum difference (size of variation) of the battery voltage difference ΔVbc for batteries having different positive / negative electrode capacity ratios (B / A). It is. It can be said that the greater the maximum difference of the battery voltage difference ΔVbc, the greater the variation in the battery voltage change amount (decrease amount) during the self-discharge period (during the standing period).
In FIG. 8, battery data with positive / negative electrode capacity ratio (B / A) value of 1.2 is □, battery data with 1.3 is ◆, and battery data with 1.4 is ●. Battery data with 1.6, ◇ Battery data with 1.7, △, Battery data with 1.8, ◯, Battery data with 1.9, ×, 2.0 Battery data is indicated by ◎.

Here, the result shown in FIG. 8 is examined.
First, the results of a battery having a positive / negative electrode capacity ratio (B / A) value of less than 1.4 (specifically, a battery having B / A values of 1.2 and 1.3) will be examined. It can be seen that in these batteries, the maximum difference in the amount of change in battery voltage (battery voltage difference ΔVbc) during the self-discharge period (during the standing period) is small regardless of the standing temperature. That is, the variation in the battery voltage change amount (battery voltage difference ΔVbc) is small between normal batteries regardless of the leaving temperature. Therefore, when the value of the positive / negative electrode capacity ratio (B / A) is less than 1.4, it is possible to appropriately detect a battery in which an internal short circuit has occurred without being affected by the standing temperature. I understand.

  Next, a battery having a positive / negative electrode capacity ratio (B / A) value of 1.4 or more (specifically, B / A values of 1.4, 1.6, 1.7, 1.8, 1.9 and 2.0) are examined. In these batteries, when left to stand and self-discharge in a temperature environment higher than 20 ° C., the maximum difference in the amount of change in battery voltage (battery voltage difference ΔVbc) during the self-discharge period (during the leave period) increases. I understand that. That is, when the value of the positive / negative electrode capacity ratio (B / A) is 1.4 or more, if the standing temperature is higher than 20 ° C., the amount of change in battery voltage (battery voltage difference) A large variation occurs in ΔVbc).

  On the other hand, when the battery is left to self-discharge in a temperature environment of 20 ° C. or lower, the maximum difference in the amount of change in battery voltage (battery voltage difference ΔVbc) during the self-discharge period (during the leaving period) is reduced. Recognize. That is, when the standing temperature is 20 ° C. or less, even if the value of the positive / negative electrode capacity ratio (B / A) is 1.4 or more, the amount of change in battery voltage (battery voltage) between normal batteries The variation of the difference ΔVbc) is reduced. As can be seen from FIG. 8, in particular, the battery voltage change amount (battery voltage difference ΔVbc) when the standing temperature is 20 ° C. or lower in a battery having a positive / negative electrode capacity ratio (B / A) value of 1.7 or more. The effect of suppressing the variation of is great.

  From the above results, in the case of a battery having a positive / negative electrode capacity ratio (B / A) value of 1.4 or more (particularly in the case of a battery having a capacity of 1.7 or more), the environment in which the battery is self-discharged by being left standing. By setting the temperature (standing temperature) to 20 ° C. or less, it is possible to reduce the variation in the amount of change in battery voltage (battery voltage difference ΔVbc) during normal discharge between the normal batteries. It can be said. Thereby, a clear difference appears in the voltage change amount (battery voltage difference ΔVbc) between the normal battery and the internal short circuit battery. Thereby, the battery in which the internal short circuit has arisen can be detected accurately.

  The reason why the variation in the battery voltage change amount (decrease amount) can be reduced is considered as follows. By setting the environmental temperature at which the battery is left to 20 ° C. or less, it is possible to suppress the SEI generation reaction during the self-discharge period (during the stand-by period), thereby reducing the battery voltage change amount (reduction amount). I believe. As a result, it is considered that the variation in the change amount (decrease amount) in battery voltage can be reduced between normal batteries.

(Investigation of battery capacity variation)
In the conventional method (for example, Patent Document 1), when the capacity ratio (B / A) of positive and negative electrodes is 1.4 or more, after self-discharge in the self-discharge process, the battery capacity is measured in the capacity measurement process. Further, even between normal batteries (batteries in which the coating amount of the electrode mixture layer is an appropriate amount), the battery capacity varies greatly, and it is sometimes impossible to accurately detect defective coating batteries. That is, the battery capacity may fluctuate (decrease) greatly during the self-discharge process (during the standing period), and as a result, the battery capacity may vary greatly.

  Here, a test performed to investigate the battery capacity variation will be described. This self-discharge test is an investigation of the influence of environmental temperature (stand temperature) in the self-discharge process on variations in battery capacity. Specifically, the relationship between the standing temperature in the self-discharge process (environment temperature of the self-discharge process) and the variation in battery capacity measured in the subsequent capacity measurement process was investigated.

  More specifically, first, 140 batteries that have undergone the above-described steps S1 to S5 are prepared. In step S1, the capacity ratio of the positive electrode capacity A and the negative electrode capacity B (negative electrode capacity B / positive electrode capacity A) is set to 1.8 as in the first embodiment. These batteries are divided into 7 groups of 20 pieces each, and, as in the self-discharge test described above, the self-discharge is performed by leaving them to stand for 10 days with different stand-by temperatures (environmental temperatures in the self-discharge process) for each group. Went. As described above, the standing temperature is different for each group from 5 ° C., 10 ° C., 15 ° C., 20 ° C., 22 ° C., 25 ° C., and 30 ° C. In addition, it has confirmed that all the 140 batteries which performed the self-discharge test are normal batteries in which the internal short circuit has not arisen.

  Then, similarly to step S7 (capacity measurement process), the battery capacity of these batteries is measured under a temperature environment of 25 ° C. Specifically, first, each battery is charged with a constant current of 1 C (5 A) until the battery voltage value reaches 4.1 V (SOC 100%), and then the battery voltage value is maintained at 4.1 V. Then, charging is performed, and the charging is terminated when the charging current value is reduced to 0.1A. Next, the battery 100 is discharged at a constant current of 1 C until the battery voltage value reaches 3.0 V (SOC 0%). The amount of electricity discharged Q1 at this time is measured as the battery capacity.

Then, for each group (each standing temperature), the battery of the battery having the smallest discharge electricity amount Q1 (battery capacity) from the value of the battery capacity of the battery having the largest discharge electricity amount Q1 (battery capacity). A value obtained by subtracting the capacity value (this value is referred to as a maximum capacity difference) was calculated. Furthermore, for each group (each standing temperature), an average value of discharge electricity quantity Q1 (battery capacity) (this value is called average battery capacity) is calculated, and the average battery capacity is calculated as shown in the following formula (1). The ratio (%) of the maximum capacity difference with respect to was calculated as an index representing the battery capacity variation.
Battery capacity variation = (maximum capacity difference / average battery capacity) × 100 (%) (1)

  These results are shown in FIG. 9 as a graph showing the relationship between the standing temperature (environment temperature of the self-discharge process) and the battery capacity variation. As described above, all the batteries to be measured are batteries having a positive / negative electrode capacity ratio (B / A) value of 1.8. It has been confirmed that all of these batteries are batteries that are not defective in coating (batteries in which an appropriate amount of the electrode mixture layer is applied).

  From FIG. 9, it can be seen that when the battery is left in a temperature environment higher than 20 ° C. in the self-discharge process, the variation in battery capacity is particularly large. It can also be seen that the battery capacity varies greatly even when the battery is left in a temperature environment lower than 10 ° C. in the self-discharge process.

  On the other hand, in the self-discharge process, when the battery is left in a temperature environment within the range of 10 to 20 ° C., it can be seen that the variation in battery capacity can be reduced. Specifically, as shown in FIG. 9, the same battery capacity variation can be maintained as when the battery capacity is measured before the self-discharge process. That is, when the battery is left in a temperature environment within the range of 10 to 20 ° C., the degree of variation in battery capacity hardly changes during the self-discharge period (during the leaving period).

  From the above results, regarding the non-aqueous electrolyte secondary battery in which the capacity ratio (B / A) of the positive and negative electrodes is increased to 1.8, the battery standing temperature (environment temperature) in the self-discharge process is in the range of 10 to 20 ° C. It can be said that the increase in the battery capacity variation can be suppressed by setting the inside.

  In addition, in comparison with the above test battery (battery with B / A value of 1.8), 140 batteries each having different positive / negative electrode capacity ratio (B / A) values were prepared. . Specifically, as in the above self-discharge test, the capacity ratio (B / A) of the positive and negative electrodes is set to 1.2, 1.3, 1.4, 1.6, 1.7, 1. 140 batteries each having 9 and 2.0 were prepared. The batteries of each capacity ratio (B / A) are divided into 7 groups of 20 pieces, and the self-discharge is performed by leaving the storage temperature (environment temperature of the self-discharge process) for each group for 10 days. Went. The standing temperature is different from 5 ° C., 10 ° C., 15 ° C., 20 ° C., 22 ° C., 25 ° C., and 30 ° C. as described above.

  Then, similarly to step S7 (capacity measurement process), the battery capacity (discharged electric quantity Q1) of these batteries was measured under a temperature environment of 25 ° C. And the value of the battery capacity variation was calculated for each group (each standing temperature) based on the above-described arithmetic expression (1). These results are shown in FIG. 10 as a graph showing the relationship between the standing temperature (environment temperature of the self-discharge process) and the battery capacity variation. FIG. 10 also shows the test results of the battery with a positive / negative electrode capacity ratio (B / A) of 1.8. In addition, it was confirmed that all the batteries tested were batteries with no coating defects (batteries with an appropriate amount of electrode mixture layer applied).

  FIG. 10 is a graph showing the relationship between the standing temperature (environment temperature in the self-discharge process) and the battery capacity variation for batteries having different positive / negative electrode capacity ratio (B / A) values. In FIG. 10, battery data with positive / negative electrode capacity ratio (B / A) value of 1.2 is □, battery data with 1.3 is ◆, and battery data with 1.4 is ●. Battery data with 1.6, ◇ Battery data with 1.7, △, Battery data with 1.8, ◯, Battery data with 1.9, ×, 2.0 Battery data is indicated by ◎.

Here, the result shown in FIG. 10 is examined.
First, the results of a battery having a positive / negative electrode capacity ratio (B / A) value of less than 1.4 (specifically, a battery having B / A values of 1.2 and 1.3) will be examined. It can be seen that in these batteries, when the leaving temperature is 10 ° C. or higher, the battery capacity variation (variation) occurring during the self-discharge period (during the leaving period) is small. On the other hand, when the standing temperature is less than 10 ° C., it can be seen that the battery capacity variation (variation) generated during the self-discharge period (during the standing period) increases. From the above results, when the positive / negative electrode capacity ratio (B / A) is less than 1.4, the standing temperature in the self-discharging process is set to 10 ° C. or more, so that the self-discharging period (during the standing period) It can be seen that the variation in battery capacity can be suppressed, and as a result, it is possible to appropriately detect a defective coating battery in the subsequent capacity measurement step.

  Next, a battery having a positive / negative electrode capacity ratio (B / A) value of 1.4 or more (specifically, B / A values of 1.4, 1.6, 1.7, 1.8, 1.9 and 2.0) are examined. In these batteries, it can be seen that, when the battery is left in a temperature environment higher than 20 ° C. in the self-discharge process, the variation in battery capacity is particularly large. In particular, it can be seen that, in a battery having a positive / negative electrode capacity ratio (B / A) value of 1.7 or more, when the standing temperature is higher than 20 ° C., the variation in battery capacity becomes remarkably large. It can also be seen that the battery capacity varies greatly even when the battery is left in a temperature environment lower than 10 ° C. in the self-discharge process.

  On the other hand, in the self-discharge process, when the battery is left in a temperature environment within the range of 10 to 20 ° C., it can be seen that the variation in battery capacity can be reduced. Specifically, when the battery is left in a temperature environment within the range of 10 to 20 ° C., the degree of variation in battery capacity hardly changes during the self-discharge period (during the leaving period). In particular, in a battery having a positive / negative electrode capacity ratio (B / A) value of 1.7 or more, the effect of suppressing variation in battery capacity by setting the standing temperature in the range of 10 to 20 ° C. is tremendous.

  From the above results, when the positive / negative electrode capacity ratio (B / A) value is 1.4 or more (particularly 1.7 or more), the standing temperature in the self-discharge process is in the range of 10 to 20 ° C. By limiting the battery capacity variation between normal batteries (batteries with an appropriate amount of electrode mixture layer coating) between self-discharge periods (during standing periods), I can say that. As a result, a clear difference appears in the battery capacity (discharged electric quantity Q1) measured in the capacity measurement process between the normal battery and the poorly applied battery, and the defectively applied battery is appropriately detected. Can do.

  The reason why the variation in battery capacity increases when the battery is left in a temperature environment higher than 20 ° C. in the self-discharge process is considered as follows. In the nonaqueous electrolyte secondary battery in which the capacity ratio (B / A) of the positive and negative electrodes is increased to 1.4 or more, the SEI generation reaction on the negative electrode surface is promoted during the self-discharge process (during the standing period). It is easy to be consumed (and therefore Li is easily consumed), and it is considered that the battery capacity may be greatly reduced. As a result, it is considered that the variation in battery capacity tends to increase.

  Further, the relationship between the positive / negative electrode capacity ratio B / A and the battery capacity was investigated. Specifically, among the batteries tested as described above, for each group of batteries subjected to the self-discharge process at a standing temperature of 20 ° C. (for each value of positive / negative electrode capacity ratio B / A) ) Is obtained. Then, with reference to the average battery capacity value of the battery group having a positive / negative electrode capacity ratio B / A value of 1.2 as a reference (100%), this reference is made for each group having a different positive / negative electrode capacity ratio B / A value. The ratio (%) of the average battery capacity to the value was calculated. The result is shown in FIG.

  FIG. 11 shows the relationship between the value of the positive / negative electrode capacity ratio (B / A) and the ratio of the average battery capacity (based on a battery in which the value of the positive / negative electrode capacity ratio B / A is 1.2). From FIG. 11, it can be seen that when the capacity ratio (B / A) of the positive and negative electrodes is in the range of 1.2 to 1.9, there is no significant difference in battery capacity. However, it can be seen that when the capacity ratio (B / A) of the positive and negative electrodes is larger than 1.9, the battery capacity decreases rapidly. It is considered that when the capacity ratio (B / A) of the positive and negative electrodes is larger than 1.9, the amount of Li consumed by the SEI generation reaction increases, and as a result, the battery capacity decreases. From this result, it can be said that the positive / negative electrode capacity ratio (B / A) is preferably 1.9 or less in order to suppress the decrease in battery capacity.

  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 S3 (battery restraint process) and step S9 (restraint release process) are provided in the embodiment, a nonaqueous electrolyte secondary battery may be manufactured without providing these processes. That is, the processing of steps S4 to S8 may be performed without sandwiching the nonaqueous electrolyte secondary battery 100 produced in the assembly process (step S2) between the pressing jigs 30 and 40 and placing them in a restrained state.

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

Claims (4)

An electrode body forming step of forming an electrode body having a positive electrode and a negative electrode;
A non-aqueous electrolyte secondary battery comprising: a non-aqueous electrolyte secondary battery in which the electrode body and the non-aqueous electrolyte are contained in a battery case; In the manufacturing method,
In the electrode body forming step, an electrode body having a capacity ratio (B / A) of the capacity A of the positive electrode and the capacity B of the negative electrode of 1.4 or more is formed,
In the self-discharge step, a non-aqueous electrolyte secondary battery manufacturing method in which the battery is left for the predetermined period in a temperature environment of 20 ° C. or lower. It is a manufacturing method of the nonaqueous electrolyte secondary battery according to claim 1,
A capacity measuring step of measuring part or all of the battery capacity of the battery that has finished the self-discharge step,
In the self-discharge step, the non-aqueous electrolyte secondary battery manufacturing method in which the battery is left for the predetermined period in a temperature environment within a range of 10 to 20 ° C. It is a manufacturing method of the nonaqueous electrolyte secondary battery according to claim 1 or 2,
In the electrode body forming step, a non-aqueous electrolyte secondary battery manufacturing method for manufacturing an electrode body having the capacity ratio (B / A) of 1.7 or more. It is a manufacturing method of the nonaqueous electrolyte secondary battery according to any one of claims 1 to 3,
Before the self-discharge process,
An initial charge / discharge step of initially charging / discharging the non-aqueous electrolyte secondary battery;
An aging process in which the battery that has undergone the initial charge / discharge process is aged at a predetermined temperature for a predetermined time, and a non-aqueous electrolyte secondary battery manufacturing method.

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