JP5365866B2 - Method for measuring thermal history of rolled copper foil - Google Patents

Description

  The present invention relates to a method for measuring the thermal history of a rolled copper foil. A rolled copper foil is used for the negative electrode collector of a lithium ion secondary battery, for example. The present invention can be used in a method for measuring the thermal history of such rolled copper foil.

  A lithium ion secondary battery includes, for example, a wound electrode body in which a positive electrode sheet and a negative electrode sheet each coated with an electrode active material on a sheet-like current collector are overlapped and wound via a separator. . A rolled copper foil may be used for the negative electrode current collector of such a lithium ion secondary battery.

  Incidentally, in Japanese Patent Application Laid-Open No. 2008-4462 (Patent Document 1), a copper foil obtained by an electrolysis method is further immersed in an electrolytic bath to deposit copper fine particles on the surface, and both surfaces are roughened. It has been proposed to use a copper foil for a negative electrode current collector of a lithium ion secondary battery. For this electrolytic copper foil, in the X-ray diffraction image, the ratio I (220) / I (200) of the peak intensity I (220) of diffraction by the 220 plane and the peak intensity I (200) of diffraction by the 200 plane is Electrolytic copper foil satisfying the relationship of I (220) / I (200)> 1 is considered preferable.

  Although it is not a technical field related to a lithium ion secondary battery, Japanese Patent Application Laid-Open No. 2003-7710 (Patent Document 2) describes heat treatment conditions applied to a silicon wafer based on the X-ray diffraction intensity ratio of the silicon wafer before and after the heat treatment. A method of determining is disclosed. In addition, in Japanese Patent No. 28673111 (Patent Document 3), the degree of crystallinity of a precipitated crystal that precipitates when a test piece prepared using an unfired ceramic powder having a predetermined particle size as a raw material is heat-treated by an X-ray diffraction method. A method of measuring by changing the X-ray intensity of a crystal is disclosed. Japanese Patent Laid-Open No. 61-175554 (Patent Document 4) discloses a nondestructive inspection method for metal tubes using X-ray diffraction. Japanese Patent Publication No. 3-69973 (Patent Document 5) discloses, as a prior art, a method for performing X-ray diffraction on a steel plate being annealed and feeding back information obtained therefrom to refine the steel plate manufacturing method. Are listed. Japanese Patent Laid-Open No. 2006-348348 (Patent Document 6) uses X-ray diffraction to select a powder-sintered silicon monoxide vapor deposition material used for forming a vapor deposition film of silicon monoxide. Technology is disclosed.

JP 2008-4462 A JP 2003-7710 A Japanese Patent No. 2,867,311 JP-A 61-175554 Japanese Examined Patent Publication No. 3-69973 JP 2006-348348 A

  This inventor is examining the lithium ion secondary battery using the negative electrode sheet which apply | coated the negative electrode active material to the negative electrode collector which consists of rolled copper foil. In the step of obtaining such a negative electrode sheet, for example, a negative electrode active material is applied to a negative electrode current collector made of a rolled copper foil and then dried by exposure to a high temperature atmosphere. The drying process of the negative electrode sheet is performed by passing the belt-shaped negative electrode sheet that is continuously conveyed through a drying furnace. The rolled copper foil used for the negative electrode current collector is exposed to heat in the drying step. When the rolled copper foil is exposed to heat, an impurity layer containing copper oxide may be formed on the surface. The present inventor said that when an impurity layer is excessively formed on a negative electrode current collector made of rolled copper foil, the electric resistance of the negative electrode current collector is increased, and the characteristics of the lithium ion secondary battery may be deteriorated. Thought. And, in the drying process when manufacturing the negative electrode sheet, by controlling the heat applied to the rolled copper foil as the negative electrode current collector, an impurity layer containing copper oxide is excessively formed on the surface of the rolled copper foil I thought that it can be prevented. However, a method for appropriately measuring the heat applied to the negative electrode current collector made of a rolled copper foil in the drying step of the negative electrode sheet has not been established.

  As a method of measuring the thermal history of the negative electrode current collector made of rolled copper foil, for example, there is a method of attaching a thermocouple to the rolled copper foil and measuring the heat actually acting on the rolled copper foil. However, the drying process of the negative electrode sheet is performed by passing the belt-shaped negative electrode sheet conveyed continuously through a drying furnace. For this reason, it is difficult to attach and transport a thermocouple to the negative electrode sheet, and it is difficult to measure the heat actually acting on the rolled copper foil. Therefore, the present invention proposes a more appropriate method for measuring the thermal history of a negative electrode current collector made of rolled copper foil.

  The method for measuring the thermal history of a rolled copper foil according to the present invention includes a peak intensity ratio measuring step for obtaining a peak intensity ratio between the 200 plane and the 220 plane by X-ray diffraction for the rolled copper foil to be inspected, and is obtained in advance. The heat for obtaining the thermal history of the rolled copper foil to be inspected based on the correlation between the peak strength ratio obtained for the rolled copper foil and the thermal history and the peak strength ratio obtained by the peak strength ratio measurement process. A history calculation step. According to the thermal history measuring method of the present invention, the thermal history of the rolled copper foil can be measured from the peak intensity ratio of the rolled copper foil to be inspected.

Further, in a method of manufacturing a lithium ion secondary battery having a negative electrode sheet in which a negative electrode active material is coated on a negative electrode current collector made of rolled copper foil, the 200 surface of the negative electrode current collector obtained by X-ray diffraction, Based on the peak intensity ratio with the 220 plane and the correlation between the peak intensity ratio between the 200 plane and the 220 plane obtained for the negative electrode current collector obtained in advance and the thermal history, the negative electrode current collector You may provide the test process which estimates the received heat quantity and performs quality determination of a negative electrode sheet.
Moreover, it is preferable that the lithium ion secondary battery which has the negative electrode sheet which apply | coated the negative electrode active material to the negative electrode collector which consists of rolled copper foil is manufactured with the said manufacturing method .

  Moreover, the inspection method of the lithium ion secondary battery which concerns on this invention is an inspection method of the lithium ion secondary battery which has the negative electrode sheet which apply | coated the negative electrode active material to the negative electrode collector which consists of rolled copper foil. This lithium ion secondary battery inspection method includes a peak intensity ratio measuring step for obtaining a peak intensity ratio between the 200 plane and the 220 plane in X-ray diffraction for the negative electrode sheet taken out from the lithium ion secondary battery; Based on the correlation between the peak intensity ratio and thermal history obtained for the obtained rolled copper foil, and the peak intensity ratio of the negative electrode sheet obtained in the peak intensity ratio measurement step, it occurred in the lithium ion secondary battery Estimating heat. According to this method for measuring the heat history of a rolled copper foil, it is possible to examine how much heat is generated in the lithium ion secondary battery.

The figure which shows a X-ray diffraction typically. The figure which shows the X-ray diffraction of a rolled copper foil and an electrolytic copper foil. The figure which shows the X-ray diffraction of the rolled copper foil exposed to 120 degreeC constant temperature atmosphere. The figure which shows the X-ray diffraction of the rolled copper foil exposed to the 140 degreeC constant temperature atmosphere. The figure which shows the X-ray diffraction of the rolled copper foil exposed to the 160 degreeC constant temperature atmosphere. The figure which shows the X-ray diffraction of the rolled copper foil exposed to the 180 degreeC constant temperature atmosphere. The figure which expanded partially the X-ray diffraction of the rolled copper foil exposed to the 120 degreeC constant temperature atmosphere. The figure which expanded partially the X-ray diffraction of the rolled copper foil exposed to the 140 degreeC constant temperature atmosphere. The figure which expanded partially the X-ray diffraction of the rolled copper foil exposed to the 160 degreeC constant temperature atmosphere. The figure which expanded partially the X-ray diffraction of the rolled copper foil exposed to the 180 degreeC constant temperature atmosphere. The figure which shows the X-ray diffraction of the rolled copper foil exposed to the constant temperature atmosphere of different temperature for 30 second. The figure which shows the relationship between a peak intensity ratio and the temperature of a constant temperature atmosphere. The figure which shows a lithium ion secondary battery typically. The figure which shows typically the winding electrode body of a lithium ion secondary battery. The figure which shows typically the manufacturing process of the negative electrode sheet which concerns on one Embodiment of this invention. The figure which shows the vehicle carrying a lithium ion secondary battery.

Hereinafter, the thermal history measuring method of the rolled copper foil which concerns on one Embodiment of this invention is demonstrated.
The method for measuring the thermal history of a rolled copper foil according to an embodiment of the present invention is the peak of 200 plane and 220 plane obtained by X-ray diffraction (XRD) for the rolled copper foil to be inspected. Find the intensity ratio. And based on the correlation of the peak intensity ratio and heat history obtained about the rolled copper foil calculated | required previously, the heat history of the rolled copper foil used as test object is calculated | required. According to the method for measuring the heat history of the rolled copper foil, for example, in the drying process of the negative electrode sheet, the heat actually received by the rolled copper foil can be more accurately known. And the process of the drying process of a negative electrode sheet can be managed more appropriately so that the impurity layer formed in rolled copper foil can be reduced. Moreover, since the rolled copper foil is inspected by X-rays, wiring for the negative electrode sheet is unnecessary. For this reason, this heat history measuring method of rolled copper foil is easy to apply also to the drying process of the strip | belt-shaped negative electrode sheet conveyed continuously to a drying furnace.

  Hereinafter, X-ray diffraction of the rolled copper foil will be described. FIG. 1 is a schematic diagram showing X-ray diffraction. In the X-ray diffraction, the X-ray 24 irradiated from the X-ray generation source 22 is irradiated to the sample surface 26a of the sample 26 (rolled copper foil). The sample surface 26a is a rolled surface of the rolled copper foil. At this time, the X-ray 24 is irradiated while the sample 26 is rotationally scanned with a predetermined scanning axis α, and the X-ray 28 diffracted by the sample 26 is captured by the inspection device 30. For example, the scan angle of the sample is scanned by θ, and the scan angle of the detector is scanned by 2θ. Next, X-rays diffracted from the sample are captured by a detector. Then, the angle difference (2θ) between the diffraction direction and the incident direction of X-rays and the diffraction X-ray intensity (I) are measured. A measurement method for scanning the incident X-ray with the sample scanning angle θ and the detector scanning angle 2θ is called 2θ / θ measurement (2θ / θ scanning method). Such X-ray diffraction can be inspected using X-ray diffractometers commercially available from various inspection apparatus manufacturers. For example, Rigaku Corporation X-ray diffraction apparatus RINT-2000 can be used.

  In the three scanning axes in FIG. 1, the θ axis is called a sample axis, the α axis is an axis, and the β axis is called an in-plane rotation axis. Moreover, the method of moving the sample 26 in the direction in which the X-ray 24 is irradiated and the direction in which the X-ray 28 diffracted by the sample 26 is captured by the inspection device 30 is illustrated. The direction in which the X-ray 24 is irradiated and the direction in which the X-ray 28 diffracted by the sample 26 is captured by the inspection device 30 may be moved with respect to the sample 26.

  In the X-ray diffraction of a copper foil which is a polycrystal, for example, as shown in FIG. 2, peak intensities are generated on the 111, 200 and 220 planes. Here, the 111 plane, the 200 plane, and the 220 plane are crystal lattice planes defined by a so-called Miller index. According to the knowledge of the present inventor, in normal rolled copper foil A, as shown in FIG. 2, the peak intensity I (200) on the 200 plane and the peak intensity I on the 220 plane compared to the peak intensity I (111) on the 111 plane. (220) becomes higher. On the other hand, in the electrolytic copper foil B as disclosed in Patent Document 1, the peak intensity I (111) of the 111 plane compared to the peak intensity I (200) of the 200 plane and the peak intensity I (220) of the 220 plane. 111) becomes higher. Thus, as can be seen from the fact that the results of X-ray diffraction are different between the rolled copper foil and the electrolytic copper foil, the crystal structures are greatly different. Note that the peak intensity I (200) of the 200 plane appears when 2θ is around 50 °, and the peak intensity I (220) of the 220 plane appears when 2θ is around 74 °.

  The inventor performed X-ray diffraction on a rolled copper foil having a known thermal history, and obtained a peak intensity I (200) of 200 planes and a peak intensity I (220) of 220 planes, respectively. In the rolled copper foil, the peak intensity I (200) on the 200 plane and the peak intensity I (220) on the 220 plane change depending on the thermal history. Hereinafter, an example is shown in FIGS.

  For example, FIG. 3 shows X-ray diffraction of a rolled copper foil exposed to a constant temperature atmosphere of 120 ° C. for a predetermined number of seconds of 10 seconds, 30 seconds, and 600 seconds. Further, in FIG. 3, X-ray diffraction data of rolled copper foil exposed to a constant temperature atmosphere of 120 ° C. for 10 seconds is x11, and X-ray diffraction data of rolled copper foil exposed to a constant temperature atmosphere of 120 ° C. for 30 seconds is x12, 120 ° C. X-ray diffraction data of a rolled copper foil exposed to a constant temperature atmosphere for 600 seconds is x13. FIG. 7 is a partially enlarged view of the result of the X-ray diffraction shown in FIG.

  FIG. 4 shows X-ray diffraction of the rolled copper foil exposed to a constant temperature atmosphere of 140 ° C. for a predetermined number of seconds of 10 seconds, 30 seconds, and 600 seconds, respectively. In FIG. 4, the X-ray diffraction of the rolled copper foil exposed to a constant temperature atmosphere of 140 ° C. for 10 seconds is x21, the X-ray diffraction of the rolled copper foil exposed to a constant temperature atmosphere of 140 ° C. for 30 seconds is x22, 140 ° C. The X-ray diffraction of the rolled copper foil exposed to the atmosphere for 600 seconds is x23. FIG. 8 is a partially enlarged view of the result of the X-ray diffraction shown in FIG.

  FIG. 5 shows X-ray diffraction of the rolled copper foil exposed to a constant temperature atmosphere of 160 ° C. for a predetermined number of seconds of 10 seconds, 30 seconds, and 600 seconds, respectively. In FIG. 5, x-ray diffraction of the rolled copper foil exposed to a constant temperature atmosphere of 160 ° C. for 10 seconds is x31, and X-ray diffraction of the rolled copper foil exposed to the constant temperature atmosphere of 160 ° C. for 30 seconds is x32, 160 ° C. The X-ray diffraction of the rolled copper foil exposed to the atmosphere for 600 seconds is x33. FIG. 9 is a partially enlarged view of the result of the X-ray diffraction shown in FIG.

  FIG. 6 shows X-ray diffraction of the rolled copper foil exposed to a constant temperature atmosphere of 180 ° C. for a predetermined number of seconds of 10 seconds, 30 seconds, and 600 seconds, respectively. In FIG. 6, the X-ray diffraction of the rolled copper foil exposed to a constant temperature atmosphere of 180 ° C. for 10 seconds is x41, and the X-ray diffraction of the rolled copper foil exposed to a constant temperature atmosphere of 180 ° C. for 30 seconds is x42, 180 ° C. The X-ray diffraction of the rolled copper foil exposed to the atmosphere for 600 seconds is x43. FIG. 10 is a partially enlarged view of the result of the X-ray diffraction shown in FIG.

  Further, in FIGS. 3 to 6, X-ray diffraction results of the rolled copper foils not subjected to the heat treatment are indicated by X0. In FIGS. 3 to 6, the results of the X-ray diffraction are slightly shifted so that the results of the X-ray diffraction do not overlap.

  As shown in FIG. 3 to FIG. 6, the peak intensity I (200) of the rolled copper foil on the 200 plane is easily affected by the applied heat, and when the applied heat increases, the peak intensity I (200 on the 200 plane) is increased. ) Tends to be high. On the other hand, the peak intensity I (220) on the 220 plane of the rolled copper foil is less susceptible to heat than the peak intensity I (200) on the 200 plane.

  Further, when the rolled copper foil is exposed to heat, an impurity layer containing copper oxide may be formed on the surface. When such an impurity layer is formed, a slight peak appears on a specific surface W (2θ is around 45.2) defined by the Miller index in the X-ray diffraction of the rolled copper foil. When used as a negative electrode current collector of a lithium ion secondary battery, it is desirable that such an impurity layer does not appear.

  For example, as shown in FIGS. 7 to 10, when an impurity layer is formed by exposing the rolled copper foil to a certain amount of heat, 2θ is around 45.2 due to the impurity layer ( A peak occurs in the X-ray diffraction at a position indicated by W. For example, as shown in FIG. 7, when the rolled copper foil is exposed to a constant temperature atmosphere of 120 ° C. for 30 seconds (x12), an X-ray diffraction peak due to the impurity layer does not appear, but the constant temperature atmosphere of 120 ° C. When exposed for 600 seconds (x13), an X-ray diffraction peak due to the impurity layer appears. As shown in FIGS. 8 and 9, when exposed to a constant temperature atmosphere of 140 ° C. or exposed to a constant temperature atmosphere of 160 ° C., similarly, when exposed to the constant temperature atmosphere for 30 seconds (x22, x32), The resulting X-ray diffraction peak does not appear, but when exposed to the constant temperature atmosphere for 600 seconds (x23, x33), the X-ray diffraction peak due to the impurity layer appears. On the other hand, when exposed to a constant temperature atmosphere of 180 ° C., as shown in FIG. 10, even when exposed to a constant temperature atmosphere for 30 seconds (x42), an X-ray diffraction peak due to the impurity layer appears.

  The present inventor found the following events (1) to (4) from the result of X-ray diffraction of the rolled copper foil as described above. (1) When heating a rolled copper foil by exposure to a constant temperature atmosphere lower than 180 ° C., the peak intensity I (200) on the 200 plane and the peak intensity I on the 220 plane are within 30 seconds. There is a temporary correlation between the ratio to (220) and the heat (heat history) received by the rolled copper foil.

  (2) When the rolled copper foil is heated by exposure to a constant temperature atmosphere in a temperature range higher than 180 ° C., an impurity layer is likely to appear in the rolled copper foil. (3) Even if it is a case where it exposes to the constant temperature atmosphere of a temperature range lower than 180 degreeC, when a heating time becomes longer than 30 second, an impurity layer may express in rolled copper foil. (4) When the impurity layer appears excessively in the rolled copper foil, the tendency of the peak intensity of X-ray diffraction changes. As the rolled copper foil used for the negative electrode current collector of the lithium ion secondary battery, it is not desirable that the impurity layer is excessively developed.

  On the other hand, when heating the rolled copper foil by exposure to a constant temperature atmosphere lower than 180 ° C., if the heating time is within 30 seconds, the impurity layer hardly appears on the rolled copper foil, and X-ray diffraction The peak intensities show the same tendency. In this case, if the heating time is the same, the peak intensity I (200) on the 200 plane increases as the heating temperature increases, but the peak intensity I (220) on the 220 plane hardly changes. Moreover, individual differences of the rolled copper foil also occur only with the peak intensity I (200) on the 200 plane. Then, this inventor considered estimating the heat | fever (heat history) which the rolled copper foil received from ratio of the peak intensity I (200) of 200 planes, and the peak intensity I (220) of 220 planes.

  For example, when X-ray diffraction data of the rolled copper foil is collected from the above-described FIGS. 3 to 6 when exposed to a constant temperature atmosphere for 30 seconds, it is as shown in FIG. In FIG. 11, x0 is X-ray diffraction data of a rolled copper foil that has not been heat-treated. x12 is X-ray diffraction data of a rolled copper foil exposed to a constant temperature atmosphere at 120 ° C. for 30 seconds. x22 is X-ray diffraction data of a rolled copper foil exposed to a constant temperature atmosphere of 140 ° C. for 30 seconds. x32 is X-ray diffraction data of a rolled copper foil exposed to a constant temperature atmosphere of 160 ° C. for 30 seconds. x42 is X-ray diffraction data of a rolled copper foil exposed to a constant temperature atmosphere of 180 ° C. for 30 seconds.

  FIG. 12 shows the ratio of the peak intensity I (200) on the 200 plane to the peak intensity I (220) on the 220 plane (here) for the X-ray diffraction data of the rolled copper foil when exposed to a constant temperature atmosphere for 30 seconds. Shows the relationship between the peak intensity ratio I (200) / I (220)) and the temperature of the constant temperature atmosphere. In FIG. 12, a plot x12 represents a peak intensity ratio I (200) / I (220) obtained from X-ray diffraction data of a rolled copper foil exposed to a constant temperature atmosphere at 120 ° C. for 30 seconds. Plot x22 shows the peak intensity ratio I (200) / I (220) obtained from the X-ray diffraction data of the rolled copper foil exposed to a constant temperature atmosphere of 140 ° C. for 30 seconds. Plot x32 shows the peak intensity ratio I (200) / I (220) obtained from the X-ray diffraction data of the rolled copper foil exposed to a constant temperature atmosphere at 160 ° C. for 30 seconds.

  In addition, in the x-ray diffraction data x42 of the rolled copper foil exposed to a constant temperature atmosphere of 180 ° C. for 30 seconds, a peak W due to the impurity layer is seen as shown in FIG. In this case, the possibility that the peak intensity ratio I (200) / I (220) is affected by the impurity layer cannot be denied. For this reason, FIG. 12 does not employ the X-ray diffraction data x42 of the rolled copper foil exposed to a constant temperature atmosphere of 180 ° C. for 30 seconds.

Table 1 shows the heat treatment temperature when the rolled copper foil is exposed to a constant temperature atmosphere for 30 seconds with respect to the data shown in FIGS. 11 and 12, and the peak intensity I (200) of the 200 planes in the X-ray diffraction data of the rolled copper foil. , 220 plane peak intensity I (220) and peak intensity ratio I (200) / I (220), respectively.

  Further, as shown in FIG. 12, regarding the X-ray diffraction data of the rolled copper foil when exposed to a constant temperature atmosphere for 30 seconds, the relationship between the peak intensity ratio I (200) / I (220) and the temperature of the constant temperature atmosphere. From this, an approximate curve L can be obtained. The approximate curve L is actually calculated by taking more data. The approximate curve L may be obtained by various appropriate methods such as linear approximation and quadratic approximation. In the example shown in FIG. 12, the approximate curve L is obtained by quadratic approximation.

  Next, X-ray diffraction is performed on the rolled copper foil to be inspected whose thermal history is unknown to obtain the peak intensity ratio I (200) / I (220) (peak intensity ratio measuring step). Then, as described above, the correlation between the peak intensity ratio I (200) / I (220) and the thermal history is obtained in advance, and the peak intensity ratio I (200) / I obtained by the peak intensity ratio measuring step is obtained. Based on (220) and the correlation, the thermal history of the rolled copper foil to be inspected is obtained (thermal history calculation step).

  For example, the peak intensity ratio I (200) / I (220) obtained from the rolled copper foil to be inspected in the peak intensity ratio measuring step is set to Y1. In this case, as shown in FIG. 12, the constant temperature of 30 seconds is based on the peak intensity ratio Y1 and the approximate curve L indicating the correlation between the peak intensity ratio I (200) / I (220) and the thermal history. T1 corresponding to the heat treatment temperature when the rolled copper foil is exposed to the atmosphere can be obtained.

  Thus, the inventor considered that the thermal history of the rolled copper foil can be estimated from the peak intensity ratio I (200) / I (220) based on the above-described correlation. Here, the thermal history is obtained by exposing the rolled copper foil to a constant temperature atmosphere at a predetermined temperature for a predetermined time, and the correlation between the temperature of the constant temperature atmosphere and the peak strength ratio I (200) / I (220) of the rolled copper foil. L is obtained. Then, based on the peak strength ratio Y1 of the rolled copper foil to be inspected whose thermal history is unknown and the correlation L, the rolled copper foil is heated to a constant temperature atmosphere of 30 seconds as the thermal history of the rolled copper foil to be inspected. A temperature T1 corresponding to the heat treatment temperature when the foil is exposed is obtained. That is, here, it can be estimated that the rolled copper foil to be inspected whose peak intensity ratio is Y1 is almost the same state as that exposed to a constant temperature atmosphere at temperature T1 for 30 seconds. Thus, according to the method for measuring the thermal history of the rolled copper foil, it is possible to completely measure the heat history of the rolled copper foil in a strict sense, that is, what kind of heat the rolled copper foil was exposed to. Although not possible, it is possible to roughly estimate the heat treatment temperature corresponding to exposure to a constant temperature atmosphere at a predetermined heat treatment temperature for 30 seconds.

  Next, the thermal history measurement method of rolled copper foil is demonstrated about the negative electrode sheet | seat actually used for a lithium ion secondary battery.

  In this embodiment, the lithium ion secondary battery 1000 includes a wound electrode body 100 as shown in FIG. In the lithium ion secondary battery 1000 shown in FIG. 13, the wound electrode body 100 housed in a rectangular battery case 300 is immersed in an electrolytic solution (not shown). As shown in FIG. 14, the wound electrode body 100 is wound by overlapping a positive electrode sheet 101 and a negative electrode sheet 103 with separators 102 and 104 interposed therebetween. Separator 102,104 is a film | membrane which an ionic substance can permeate | transmit, and the microporous film made from a polypropylene is used in this embodiment.

In this embodiment, the positive electrode sheet 101 is coated with an electrode material 132 containing a positive electrode active material on both surfaces of a positive electrode current collector 131 made of an aluminum foil. Examples of the positive electrode active material included in the electrode material 132 include lithium manganate (LiMn ₂ O ₄ ), lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), and transition metal substitutes thereof. It is done.

  In this embodiment, the negative electrode sheet 103 is coated with an electrode material 142 containing a negative electrode active material on both surfaces of a negative electrode current collector 141 made of rolled copper foil. Examples of the negative electrode active material included in the electrode material 142 include carbon-based materials such as graphite and amorphous carbon, lithium-containing transition metal oxides, and transition metal nitrides. Specifically, in this embodiment, graphite is used as the negative electrode active material, and the graphite, carboxymethylcellulose (CMC), and water are mixed at a weight ratio of 98: 1: 250, A paste in which 1.02 parts by weight of styrene-butadiene rubber (SBR) is uniformly dispersed with respect to graphite as a negative electrode active material is applied to the negative electrode current collector 141.

For example, as shown in FIG. 15, the coating process of the negative electrode material 142 is performed using a coating apparatus 400 (for example, a die coater) with a predetermined coating weight (for example, a coating weight of one side of 3.2 mg). / cm ² ) on both surfaces of the negative electrode current collector 141. Thereafter, the electrode material 142 applied to the drying furnace 410 through the negative electrode current collector 141 is dried. In this embodiment, the electrode material 142 was dried by passing through a drying furnace 410 having a constant temperature atmosphere of 120 ° C. for a predetermined time. At this time, the conveyance speed of the negative electrode current collector 141 was set to 40 m / min. In the example shown in FIG. 15, the electrode material 142 is applied in three lines along the length direction of the negative electrode current collector 141. The electrode material 142 is coated with a predetermined width and a predetermined interval apart from both edges in the width direction of the negative electrode current collector 141. All of the applied electrode materials 142 have the same width. The negative electrode current collector 141 shown in FIG. 15 is cut along five cutting lines z1 to z5 set in the width direction, whereby the negative electrode sheet 103 shown in FIG. 14 is obtained.

  In this case, it is desired to appropriately control the temperature of the drying furnace 410 so that an impurity layer is not excessively formed on the negative electrode current collector 141 of the negative electrode sheet 103. However, it is not practical to attach a thermocouple to the negative electrode sheet 103 and measure the thermal history of the negative electrode sheet 103 in the drying process because it is difficult to handle wiring and the like. Therefore, in this embodiment, an X-ray diffraction apparatus 420 is provided on the downstream side of the drying furnace 410 in the conveyance path of the negative electrode sheet 103. Then, the X-ray diffraction of the negative electrode current collector 141 is performed at the position that has passed through the drying furnace 410, and the peak intensity ratio I (200) / I (220) of the negative electrode current collector 141 is obtained. Then, as shown in FIG. 12, based on the correlation L between the peak intensity ratio I (200) / I (220) of the rolled copper foil obtained in advance and the thermal history, the negative electrode current collector to be inspected The heat history of the body 141 is obtained.

In this embodiment, in the negative electrode sheet 103, X-ray diffraction is performed in each of the uncoated portion S1 where the electrode material 142 is not coated and the coated portion S2 where the electrode material 142 is coated. A peak intensity ratio I (200) / I (220) of the foil was obtained. In this case, in the coating part S2 to which the electrode material 142 is applied, the heat received by the rolled copper foil is smaller than in the uncoated part S1 to which the electrode material 142 is not applied. The uncoated portion S2 in the resulting peak intensity ratio I (200) / I (220) and _{Y S2,} the peak intensity ratio I (200) obtained in the coating section S1 / I a (220) and _{Y S1.} As shown in FIG. 12, based on the peak intensity ratios Y _S1 and Y _S2 and the correlation L, the thermal history T _S1 of the negative electrode current collector 141 in the uncoated part S1 and the negative electrode in the coated part S2 The thermal history T _S2 of the current collector 141 can be obtained respectively.

The thermal histories T _S1 and T _S2 are obtained based on the correlation L between the peak intensity ratio I (200) / I (220) and the heat treatment temperature shown in FIG. The correlation L shown in FIG. 12 is an approximation showing the correlation between the peak intensity ratio I (200) / I (220) of the rolled copper foil and the heat treatment temperature when the rolled copper foil is exposed to a constant temperature atmosphere for 30 seconds. Curve L. Therefore, the thermal histories T _S1 and T _S2 obtained by the above method indicate the heat treatment temperature when the rolled copper foil is exposed to a constant temperature atmosphere of 30 seconds. That is, in this embodiment, in the uncoated part S1, it is presumed that the negative electrode current collector 141 is subjected to the same heat treatment as when the rolled copper foil was exposed to a constant temperature atmosphere of the temperature T _S1 for 30 seconds. . In addition, in the coating part S2, it is presumed that the negative electrode current collector 141 is subjected to the same heat treatment as when the rolled copper foil was exposed to a constant temperature atmosphere of the temperature T _S2 for 30 seconds.

  Thus, this heat history measurement method of the rolled copper foil can measure the heat history of the negative electrode current collector used in the lithium ion secondary battery 1000. Here, when the rolled copper foil is exposed to a constant temperature atmosphere at a predetermined temperature for 30 seconds, it can be estimated how much heat treatment is performed at the same temperature as when exposed to a constant temperature atmosphere. In this case, in the manufacturing process of the lithium ion secondary battery 1000, for the negative electrode sheet 103, the peak intensity ratio I (200) / I (200) / 220 of the negative electrode current collector 141 obtained by X-ray diffraction is obtained. 220), an inspection process for determining the quality of the negative electrode sheet 103 may be provided.

  According to the knowledge of the present inventor, it has been found that in the heat treatment in which the rolled copper foil is exposed to a constant temperature atmosphere of 170 ° C. or lower for 30 seconds, a peak due to the appearance of the impurity layer does not occur in X-ray diffraction. Further, according to the knowledge of the present inventor, when the heat treatment temperature is 170 ° C., the peak intensity ratio I (200) / I (220) shows about 10.8. Therefore, in the negative electrode sheet 103 used for the lithium ion secondary battery 1000, if the peak intensity ratio I (200) / I (220) measured in the uncoated part S1 after the drying process is 10.8 or less, the negative electrode It is considered that the possibility that the impurity layer is developed in the current collector 141 is low.

  In this case, for example, the peak intensity ratio I (200) / I (220) of the uncoated part S1 after the drying process is measured. When the peak intensity ratio I (200) / I (220) is 10.8 or less, the negative electrode sheet 103 is regarded as a non-defective product, and the peak intensity ratio I (200) / I (220) is from 10.8. The larger negative electrode sheet 103 may be determined as defective.

  Further, in the drying process of the negative electrode sheet 103, it can be used for temperature management of the drying furnace 410 and the like. That is, the temperature of the drying furnace 410 may be controlled so that the peak intensity ratio I (200) / I (220) of the uncoated part S1 after the drying process is 10.8 or less. In addition, for example, a lithium ion secondary battery 1000 with a negative electrode current collector having a peak intensity ratio I (200) / I (220) of 10.8 or less after the drying step may be used. Thereby, the lithium ion secondary battery 1000 with few impurity layers in the negative electrode current collector 141 of the negative electrode sheet 103 can be stably produced.

  In addition, in a lithium ion secondary battery having a negative electrode current collector peak intensity ratio I (200) / I (220) of 10.8 or less, it is unlikely that an impurity layer generated in the negative electrode current collector 141 is developed. . The lithium ion secondary battery 1000 provided with such a negative electrode current collector 141 is excellent in battery characteristics and can be expected to have high output characteristics. For example, as schematically shown in FIG. 16, the lithium ion secondary battery 1000 is suitably used for a battery 1000 for a motor (electric motor) mounted on a vehicle 1 such as a hybrid vehicle, an electric vehicle, or a fuel cell vehicle. be able to. These vehicles are required to have high output power and stable battery performance over time. In this case, by evaluating and selecting the negative electrode sheet as described above, the performance of the lithium ion secondary battery for vehicles can be improved, and as a result, a vehicle with good performance can be supplied stably.

  The lithium ion secondary battery 1000 may generate heat while repeatedly being discharged and charged. In such a case, it is difficult to appropriately examine how much heat is generated in the lithium ion secondary battery 1000 (for example, in the wound electrode body 100). The method for measuring the thermal history of the rolled copper foil described above is a method for inspecting a lithium ion secondary battery that inspects a lithium ion secondary battery having a negative electrode sheet in which a negative electrode active material is coated on a negative electrode current collector made of rolled copper foil. Applicable. That is, this lithium ion secondary battery inspection method preferably includes a peak intensity ratio measurement step and a step of estimating heat generated in the lithium ion secondary battery (estimation step). In the peak intensity ratio measurement step, the peak intensity ratio between the 200 plane and the 220 plane in the X-ray diffraction is determined for the negative electrode sheet taken out from the lithium ion secondary battery. In the process of estimating the heat generated in the lithium ion secondary battery (estimation process), the correlation between the peak intensity ratio obtained for the rolled copper foil and the thermal history obtained in advance and the peak intensity ratio measurement process are used. Based on the peak intensity ratio of the negative electrode sheet thus obtained, heat generated in the lithium ion secondary battery is estimated.

According to this inspection method for a lithium ion secondary battery, for example, with respect to the negative electrode sheet taken out from the lithium ion secondary battery, the peak intensity ratio I (200) / I (220) between the 200 plane and the 220 plane in X-ray diffraction. ) (Peak intensity ratio measurement step). Then, the correlation between the peak intensity ratio obtained for the rolled copper foil obtained in advance and the thermal history (see, for example, FIG. 12) and the peak intensity ratio of the negative electrode sheet obtained in the peak intensity ratio measurement step Based on this, heat generated in the lithium ion secondary battery can be estimated (estimation step). Thus, for example, when the peak intensity ratio I (200) / I (220) is 12, the heat received by the negative electrode current collector 141 in the lithium ion secondary battery 1000 is changed to the temperature T as shown in FIG. _It can be estimated that the heat was about the same as that exposed to a constant temperature atmosphere of _x for 30 seconds. Thus, according to this inspection method for lithium ion secondary batteries (heat history measurement method for rolled copper foil), the lithium ion secondary battery 1000 is more than the amount of heat received by the negative electrode current collector 141 during the heat treatment in the drying process. It is possible to estimate how much heat is generated in the lithium ion secondary battery 1000 when the amount of heat generated by charging and discharging is large.

  As described above, according to this lithium ion secondary battery inspection method (heat history measurement method of rolled copper foil), how much heat is generated in the lithium ion secondary battery 1000 can be examined. For example, in the safety test of the lithium ion secondary battery 1000, the lithium ion secondary battery 1000 may be used in an abnormal manner to generate high-temperature heat in the lithium ion secondary battery 1000. This inspection method of lithium ion secondary battery (heat history measurement method of rolled copper foil) is used as a method for examining how much heat is generated in the lithium ion secondary battery 1000 in such a safety test. Can do.

  As mentioned above, although the thermal history measurement method of the rolled copper foil which concerns on one Embodiment of this invention and the inspection method of the lithium ion secondary battery using the thermal history measurement method of the said rolled copper foil were demonstrated, the rolled copper which concerns on this invention The method for measuring the heat history of the foil and the method for inspecting the lithium ion secondary battery are not limited to the above.

  For example, in the above-described embodiment, as shown in FIG. 12, when the rolled copper foil is exposed to a constant temperature atmosphere for 30 seconds, the temperature of the constant temperature atmosphere and the peak strength ratio I (200) / I ( 220). In the present invention, when obtaining such a correlation, the time for exposing the rolled copper foil to a constant temperature atmosphere is not limited to 30 seconds. Further, in the present invention, when obtaining such correlation, the temperature of the constant temperature atmosphere is kept constant, the time of exposure to the constant temperature atmosphere is changed, the time of exposing the rolled copper foil to the constant temperature atmosphere, and the peak of the rolled copper foil A correlation L with the intensity ratio I (200) / I (220) may be derived. For example, as shown in FIG. 3, the peak intensity ratio I (200) / I (220) is obtained from a rolled copper foil in which the temperature of the constant temperature atmosphere is kept constant at 120 ° C. and the time of exposure to the constant temperature atmosphere is changed. And you may obtain the correlation with the time which exposed the rolled copper foil to the said constant temperature atmosphere, and the said peak intensity ratio I (200) / I (220).

  As described above, various correlations can be adopted for the correlation between the peak intensity ratio and the thermal history obtained for the rolled copper foil. And when calculating | requiring the thermal history of the said rolled copper foil from the peak intensity ratio I (200) / I (220) of the rolled copper foil used as a test object, it is good to evaluate appropriately based on the employ | adopted correlation.

  That is, when the correlation between the time during which the rolled copper foil is exposed to a constant temperature atmosphere at a predetermined temperature and the peak intensity ratio I (200) / I (220) is used, the peak intensity of the rolled copper foil to be inspected is used. The thermal history derived from the ratio I (200) / I (220) is evaluated by the time exposed to the constant temperature atmosphere. Moreover, when using the correlation (for example, correlation L of FIG. 12) with the temperature of the constant temperature atmosphere which exposed the rolled copper foil for the predetermined time, and peak intensity ratio I (200) / I (220), it test | inspects. The thermal history derived from the peak intensity ratio I (200) / I (220) of the rolled copper foil as an object is evaluated at the temperature of the constant temperature atmosphere to which the rolled copper foil is exposed. Thus, even if the peak intensity ratio I (200) / I (220) of the rolled copper foil to be inspected is the same, the evaluation of the thermal history of the rolled copper foil differs depending on the correlation employed.

DESCRIPTION OF SYMBOLS 1 Vehicle 22 X-ray generation source 24 X-ray 26 Sample 26a Sample surface 28 Diffracted X-ray 30 Inspection device 100 Winding electrode body 101 Positive electrode sheet 102, 104 Separator 103 Negative electrode sheet 131 Positive electrode current collector 132 Positive electrode material 141 Negative electrode current collector 142 Negative electrode material 300 Battery case 400 Coating device 410 Drying furnace 420 X-ray diffraction device 1000 Lithium ion secondary battery

Claims (5)

A thermal history measurement method for measuring the thermal history of a rolled copper foil,
For a rolled copper foil to be inspected, a peak intensity ratio measuring step for obtaining a peak intensity ratio between the 200 plane and the 220 plane by X-ray diffraction,
Based on the correlation between the peak strength ratio obtained in advance for the rolled copper foil and the thermal history, and the peak strength ratio obtained by the peak strength ratio measurement step, the rolled copper foil to be inspected A method for measuring the thermal history of a rolled copper foil, comprising a thermal history calculation step for obtaining a thermal history. A method for producing a lithium ion secondary battery having a negative electrode sheet coated with a negative electrode active material on a negative electrode current collector made of rolled copper foil,
For the negative electrode sheet, the peak intensity ratio between the 200 and 220 surfaces of the negative electrode current collector obtained by X-ray diffraction, and the 200 and 220 surfaces obtained for the negative electrode current collector obtained in advance. Manufacture of a lithium ion secondary battery comprising an inspection step for estimating the amount of heat received by the negative electrode current collector based on the correlation between the peak intensity ratio and the thermal history of the negative electrode sheet Method. A lithium ion secondary battery manufactured by the manufacturing method according to claim 2 .   A vehicle equipped with the lithium ion secondary battery according to claim 3. A method for inspecting a lithium ion secondary battery having a negative electrode sheet in which a negative electrode active material is applied to a negative electrode current collector made of rolled copper foil,
For the negative electrode sheet taken out from the lithium ion secondary battery, a peak intensity ratio measuring step for obtaining a peak intensity ratio between the 200 plane and the 220 plane in X-ray diffraction;
Based on the correlation between the peak strength ratio obtained in advance for the rolled copper foil and the thermal history, and the peak strength ratio of the negative electrode sheet obtained in the peak strength ratio measurement step, the lithium ion secondary A method for inspecting a lithium ion secondary battery, comprising a step of estimating heat generated in the battery.

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