JP2012195132A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress variation in fluid volume distribution of electrolyte with which each region of a positive electrode and a negative electrode is impregnated.SOLUTION: In a secondary battery comprising a wound body formed by winding a power generation sheet extending in belt-shape while including a positive electrode and a negative electrode, following conditional expressions (1), (2) are satisfied. In the conditional expressions, the length of one of the positive electrode or the negative electrode in the winding direction is M mm, the length of the other electrode in the winding direction is L mm, the number of first collector tabs connected side by side for the other electrode in the winding direction is n, the interval of adjoining first collector tabs is T mm, and the width of the first collector tabs is W mm. The conditional expression (1) is M/natural number=T, and the conditional expression (2) is 0.898<1-{(W×n)/L}<0.995.

Description

  The present invention relates to a lithium ion battery including a wound body as a power generation element.

  In recent years, lithium ion batteries using a carbon material that occludes and releases lithium ions as a negative electrode material and a lithium-containing composite oxide as a positive electrode material have attracted attention. In this type of lithium ion battery, the positive electrode current collector tab connected to the positive electrode body is connected to the positive electrode external terminal, while the negative electrode current collector tab connected to the negative electrode body is connected to the outer tube also serving as the negative electrode terminal. Thus, electric energy is extracted from both positive and negative electrodes.

  Patent Document 1 discloses a lithium ion battery in which a plurality of positive electrode current collector tabs are connected to a positive electrode current collector at regular intervals.

Japanese Patent Laid-Open No. 10-261439 JP 2000-182656 A JP 2000-106167 A

  However, in the configuration of Patent Document 1, there is a variation in the liquid volume distribution of the electrolyte solution impregnated in each region of the positive electrode body and the negative electrode body. Then, this invention aims at suppressing the dispersion | variation in the liquid volume distribution of the electrolyte solution impregnated in each area | region of a positive electrode body and a negative electrode body.

In order to solve the above-mentioned problems, a secondary battery according to the present invention is (I) a secondary battery including a wound body in which a power generation sheet extending in a strip shape in which a positive electrode body and a negative electrode body are stacked via a separator is wound. The length of one electrode body in the winding direction of the positive electrode body and the negative electrode body is M (mm), the length of the other electrode body in the winding direction is L (mm), and the other electrode body is In contrast, the number of first current collecting tabs connected side by side in the winding direction is n, the interval between adjacent first current collecting tabs is T (mm), and the width of the first current collecting tabs is A secondary battery characterized by satisfying the following conditional expressions (1) and (2) when W (mm).
M / natural number = T (1)
0.898 <1-{(W × n) / L} <0.995 (2)

  (II) In the configuration of (I), the one electrode body may be the negative electrode body, and the other electrode body may be the positive electrode body.

  (III) In the configuration of (II), the second current collecting tab connected to the one electrode body can be provided at a position that does not overlap the positive electrode body when the power generation sheet is viewed in the thickness direction. Thereby, the metal deposited on the second current collecting tab can be prevented from penetrating the separator and coming into contact with the positive electrode body.

  (IV) In the configuration of (I) or (II), in the thickness direction view of the power generation sheet, the first current collection tab and the second current collection tab connected to the one electrode body are mutually It can be provided at a position where it does not overlap. Thereby, it can suppress that the burr | flash produced | generated by the 1st and 2nd current collection tab contacted and short-circuited.

  (V) In the configurations of (I) to (III) above, the power generation element is a power generation element of a lithium ion battery, and the wound body can be housed together with an electrolyte in a cylindrical case. According to the structure of (V), the dispersion | variation in the liquid volume distribution of the electrolyte solution impregnated in the electric power generation element accommodated in the winding body can be suppressed.

  (VI) A plurality of secondary batteries according to any one of the above (I) to (V) may be prepared and connected to be mounted on a vehicle as an assembled battery for a vehicle. The vehicle may be an electric vehicle that drives a motor only by the output of the assembled battery, or a hybrid vehicle that uses both the internal combustion engine and the assembled battery as a power source.

  According to the present invention, it is possible to suppress variations in the distribution of the electrolyte amount impregnated in each region of the positive electrode body and the negative electrode body.

It is the top view which illustrated the state before winding of a winding body. It is a perspective view of a cylindrical battery. It is sectional drawing of a positive electrode body, a negative electrode body, and a separator. It is sectional drawing of the positive electrode body as a comparative example of FIG. 2, a negative electrode body, and a separator. It is sectional drawing of the positive electrode body as a comparative example of FIG. 2, a negative electrode body, and a separator. 2 is a plan view of a positive electrode body and a negative electrode body of Example 1. FIG. It is a top view which shows the state which accumulated the positive electrode body of Example 1, the negative electrode body, and the separator. 3 is a plan view of a positive electrode body in Example 2. FIG. 4 is a plan view of a positive electrode body in Example 3. FIG. 6 is a plan view of a positive electrode body in Example 4. FIG. 6 is a plan view of a positive electrode body and a negative electrode body of Example 5. FIG. 3 is a plan view of a positive electrode body of Comparative Example 1. FIG. 6 is a plan view of a positive electrode body in Comparative Example 2. FIG. 6 is a plan view of a positive electrode body and a negative electrode body of Comparative Example 3. FIG. It is a graph which shows the evaluation result of Table 1.

  A lithium ion battery (secondary battery) according to this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1A shows a state before winding of the positive electrode body 10 and the negative electrode body 20 constituting the power generation sheet of the lithium ion battery. FIG. 1B is a perspective view of a lithium ion battery. FIG. 2 is a cross-sectional view of the positive electrode body 10, the negative electrode body 20, and the separator 30 cut in the thickness direction. The positive electrode body 10 and the negative electrode body 20 constitute a power generation sheet extending in a strip shape by being stacked via a separator 30 (see FIG. 1A). The power generation sheet is wound to form a wound body, and is accommodated together with the electrolyte in the cylindrical case 5 (see FIG. 2).

  The positive electrode body 10 includes a current collector 13 and a positive electrode layer 11 applied to both surfaces of the current collector 13. An uncoated portion where the positive electrode layer 11 is not applied is formed on the current collector 13, and a positive electrode current collecting tab 12 is connected to the uncoated portion. The connection method may be welding or the like. Two positive electrode current collecting tabs 12 of the present embodiment are provided side by side in the longitudinal direction of the positive electrode body 10. However, the number of the positive electrode current collecting tabs 12 is not limited as long as it is two or more.

  The negative electrode body 20 includes a current collector 23 and a negative electrode layer 21 applied to both surfaces of the current collector 23. An uncoated portion where the positive electrode layer 21 is not applied is formed on the current collector 23, and a negative electrode current collecting tab 22 is connected to the uncoated portion. The connection method may be welding or the like. Two negative electrode current collecting tabs 22 of the present embodiment are provided side by side in the longitudinal direction of the negative electrode body 20.

With reference to FIG. 1A, the length of the negative electrode body 20 in the winding direction is M (mm), the length of the positive electrode body 10 in the winding direction is L (mm), and the positive electrode adjacent to the winding direction of the positive electrode body 10 When the interval between the current collecting tabs 12 is T (mm), the number of the positive current collecting tabs 12 is n, and the width of the positive current collecting tabs 12 is W (mm), the following conditional expressions (1) and (2) Satisfied.
M / natural number = T (1)
0.898 <1-{(W × n) / L} <0.995 (2)

  By satisfying the above conditional expressions (1) and (2), variation in the distribution of the electrolyte solution impregnated in each part of the positive electrode body 10 and the negative electrode body 20 is suppressed, and a decrease in battery capacity can be suppressed. That is, the positive electrode current collector tab 12 is formed thicker than the positive electrode body 10, and when it is formed as a wound body, a gap is formed around the positive electrode current collector tab 12, and the positive electrode body 10 is interposed through this gap. And each part of the negative electrode body 20 is impregnated with an electrolytic solution.

  The reason why the conditional expression (2) limits the width W of the positive electrode current collecting tab 12, the number n of the positive electrode current collecting tabs 12, and the length L in the longitudinal direction of the positive electrode body 10 will be described. When the area of the positive electrode current collecting tab 12 occupying the positive electrode body 10 is relatively large, the number of uncoated parts to which the active material is not applied increases, so that the battery output decreases. On the other hand, when the area of the positive electrode current collecting tab 12 occupying the positive electrode body 10 is relatively small, the amount of the electrolytic solution flowing from the periphery of the positive electrode current collecting tab 12 is reduced when the electrolytic solution is impregnated. In order to satisfy these problems, the width W of the positive electrode current collecting tab 12, the number n of the positive electrode current collecting tabs 12, and the length L in the longitudinal direction of the positive electrode body 10 are limited.

  As shown in FIG. 2, the positive electrode current collecting tab 12 and the negative electrode current collecting tab 22 are preferably provided at positions that do not overlap with each other in the thickness direction of the positive electrode body 10. The effect of this will be described with reference to a comparative example. FIG. 3A is a cross-sectional view corresponding to FIG. 2, and differs from the configuration illustrated in FIG. 2 in that a negative electrode current collecting tab 22 is provided so as to face the positive electrode current collecting tab 12.

  Each of the positive electrode current collecting tab 12 and the negative electrode current collecting tab 22 is obtained by cutting a metal sheet as a base material, and burrs may be generated in this cutting process. As shown in FIG. 3A, when the positive electrode current collecting tab 12 and the negative electrode current collecting tab 22 are arranged to face each other, these burrs may come into contact with each other and short-circuit. Therefore, as shown in FIG. 2, by providing the positive electrode current collecting tab 12 and the negative electrode current collecting tab 22 at positions where they do not overlap each other, it is possible to suppress a short circuit due to contact between burrs.

  However, even in the configuration illustrated in FIG. 3A, variation in the electrolyte volume distribution can be suppressed by satisfying conditional expressions (1) and (2).

  As shown in FIG. 2, the negative electrode current collecting tab 22 is preferably provided at a position that does not overlap the positive electrode body 10 in the thickness direction of the positive electrode body 10. The effect of this will be described with reference to a comparative example. FIG. 3B is a cross-sectional view corresponding to FIG. 2, and is different from the configuration illustrated in FIG. 2 in that a negative electrode current collecting tab 22 is provided so as to face the positive electrode body 10.

  When the lithium ion battery is charged, the lithium ions in the positive electrode layer 11 move to the negative electrode body 20. At this time, in the configuration illustrated in FIG. 3B, since the negative electrode current collecting tab 22 is provided at a position facing the positive electrode layer 11, lithium metal is deposited on the negative electrode current collecting tab 22. When the lithium ion battery is further charged, the lithium metal deposited on the negative electrode current collecting tab 22 may penetrate the separator 30 and contact the positive electrode body 10 to cause a short circuit. In the configuration illustrated in FIG. 2, since the negative electrode current collecting tab 22 is provided at a position where it does not overlap the positive electrode body 10, it is possible to suppress deposition of lithium metal on the negative electrode current collecting tab 22.

  However, even in the configuration illustrated in FIG. 3B, variation in the electrolyte volume distribution can be suppressed by satisfying conditional expressions (1) and (2).

  The present invention showing examples will be described in detail. The lithium ion batteries of Examples 1 to 4 and Comparative Examples 1 to 3 below were evaluated by calculating the capacity retention rate. The capacity maintenance rate was calculated by subjecting a lithium ion battery to cycle charge / discharge and dividing the post-cycle capacity after cycle charge / discharge by the initial capacity before cycle charge. Specifically, it was calculated from the capacity before and after 1000 cycles of 2C CC charge / discharge in a 50 ° C. thermostat. The capacity was discharged to 4.2V at C rate (1C), paused for 5 minutes, then discharged to 2.5V, then CC-CV charge (4.2V, rate 1C, 0.1C cut) and CCCV discharge (4.2 V, rate 1 C, 0.1 C cut).

Example 1
FIG. 4 is a plan view of the positive electrode body 10 and the negative electrode body 20 according to the first embodiment. The positive electrode layer 11 is composed of a positive electrode active material, a binder, and a conductive agent. Lithium cobaltate is used as the positive electrode active material, PVDF is used as the binder, and acetylene black is used as the conductive agent. An aluminum foil was used for the current collector 13. The positive electrode layer 11 was applied to the current collector 13 and dried, and then rolled into a sheet with a roll. The rolled sheet was cut into a width of 54.0 mm to obtain a hoop of the positive electrode body 10. The length in the longitudinal direction of the hoop of the positive electrode body 10 was set to 690 mm. The positive electrode current collecting tab 12 is ultrasonically welded to a first position that is 218.0 mm away from the end in the longitudinal direction and a second position that is further 290.0 mm away from the first position in the winding direction. Fixed by. The positive electrode current collecting tab 12 was made of aluminum and set to a size of width 5.0 mm, thickness 0.1 mm, and length 50.0 mm.

  The negative electrode layer 21 is composed of a negative electrode active material, a binder, and a thickener, natural graphite is used as the negative electrode active material, SBR is used as the binder, and carboxymethyl cellulose is used as the thickener. Copper foil was used for the negative electrode current collector foil. The negative electrode layer 21 was applied to the negative electrode body 23 and dried, and then rolled into a sheet by a roll. The rolled sheet was cut into a width of 56.0 mm to obtain a hoop of the negative electrode body 20. The length of the hoop of the negative electrode body 20 in the longitudinal direction was set to 870.0 mm. The negative electrode current collecting tab 22 was fixed to both ends in the longitudinal direction of the negative electrode body 20 by ultrasonic welding. The negative electrode current collecting tab 22 was made of nickel.

As the electrolytic solution, a solution obtained by dissolving 1M of LIPF ₆ in a non-aqueous mixed solvent was used. As the non-aqueous mixed solvent, a mixed solvent composed of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate was used. The mixing ratio of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate was set to 3: 5: 2 by volume.

  With reference to FIG. 5, these positive electrode body 10 and negative electrode body 20 were laminated | stacked through the separator 30, and the wound body was obtained by winding. That is, the positive electrode body 10 and the negative electrode body 20 are wound in the direction of the arrow A in a state where the positive electrode body 10 and the negative electrode body 20 are opposed to each other with the separator 30 interposed therebetween. Was wound so that the spacing in the rolling direction was 14.0 mm. The obtained wound body is accommodated in a cylindrical outer case, the wound body and the bottom surface of the cylindrical outer case are welded, and an electrolyte is injected to obtain a lithium ion battery having a theoretical capacity of 1.5 Ah. Ten cells were produced. The size of the cylindrical outer case was set to 18 mm in diameter and 650 mm in the direction perpendicular to the radial direction.

  Since the interval between the adjacent positive electrode current collecting tabs 12 is 290.0 mm obtained by dividing the length of the negative electrode body 20 in the longitudinal direction (870.0 mm) by the natural number 3, conditional expression (1) is satisfied. The length L of the positive electrode body 10 in the longitudinal direction is 690.0 mm, the number n of the positive electrode current collecting tabs 12 is 2, and the width W of the positive electrode current collecting tabs 12 is 5.0 mm. Substituting into equation (2) yields 0.986, which satisfies conditional expression (2).

(Example 2)
Except the production of the positive electrode body 10, the same procedure as in Example 1 was carried out, and 10 lithium ion batteries having a theoretical capacity of 1.35 Ah were produced. Referring to FIG. 6, a hoop of positive electrode body 10 was obtained, and the length of the hoop in the longitudinal direction was adjusted to 690.0 mm. Seven positive electrode current collecting tabs 12 were provided at intervals of 108.75 mm, and these positive electrode current collecting tabs 12 were fixed to the positive electrode body 10 by ultrasonic welding. The positive electrode current collecting tab 12 located on the leftmost side was disposed at a position 36.75 mm away from the longitudinal end of the positive electrode body 10. The positive electrode current collecting tab 12 was made of aluminum and was adjusted to a size of 10.0 mm in width, 0.1 mm in thickness, and 50.0 mm in length.

  Since the interval between the adjacent positive electrode current collecting tabs 12 is 108.75 mm obtained by dividing the length of the negative electrode body 20 in the longitudinal direction (870.0 mm) by the natural number 8, conditional expression (1) is satisfied. The length L in the longitudinal direction of the positive electrode body 10 is 690.0 mm, the number n of the positive electrode current collecting tabs 12 is 7, and the width W of the positive electrode current collecting tabs 12 is 10.0 mm. Substituting into equation (2) gives 0.899, which satisfies conditional expression (2).

(Example 3)
Except the production of the positive electrode body 10, the same procedure as in Example 1 was carried out, and 10 lithium ion batteries having a theoretical capacity of 1.35 Ah were produced. Referring to FIG. 7, a hoop of positive electrode body 10 was obtained, and the length of this hoop in the longitudinal direction was adjusted to 690.0 mm. Two positive electrode current collecting tabs 12 were provided at 290.0 mm intervals, and these positive electrode current collecting tabs 12 were fixed to the positive electrode body 10 by ultrasonic welding. The positive electrode current collecting tab 12 located on the left side was arranged at a position away from the end in the longitudinal direction of the positive electrode body 21 by 218.0 mm. The positive electrode current collecting tab 12 was made of aluminum and set to a size of 35.0 mm in width, 0.1 mm in thickness, and 50.0 mm in length. That is, the size of the positive electrode current collecting tab 12 was changed from that in Example 1.

  Since the interval between the adjacent positive electrode current collecting tabs 12 is 290.0 mm obtained by dividing the length of the negative electrode body 20 in the longitudinal direction (870.0 mm) by the natural number 3, conditional expression (1) is satisfied. The length L in the longitudinal direction of the positive electrode body 10 is 690.0 mm, the number n of the positive electrode current collecting tabs 12 is 2, and the width W of the positive electrode current collecting tabs 12 is 35.0 mm. Substituting into equation (2) gives 0.899, which satisfies conditional expression (2).

Example 4
Except the production of the positive electrode body 10, the same procedure as in Example 1 was carried out, and 10 lithium ion batteries having a theoretical capacity of 1.5 Ah were produced. Referring to FIG. 8, a hoop of positive electrode body 10 was obtained, and the length of this hoop in the longitudinal direction was adjusted to 690.0 mm. Two positive electrode current collecting tabs 12 were provided at 290.0 mm intervals, and these positive electrode current collecting tabs 12 were fixed to the positive electrode body 10 by ultrasonic welding. The positive electrode current collecting tab 12 located on the left side was arranged at a position away from the end in the longitudinal direction of the positive electrode body 21 by 218.0 mm. The positive electrode current collecting tab 12 was made of aluminum and adjusted to a size of width 2.0 mm, thickness 0.1 mm, and length 50.0 mm. That is, the size of the positive electrode current collecting tab 12 was changed from that in Example 1.

  Since the interval between the adjacent positive electrode current collecting tabs 12 is 290.0 mm obtained by dividing the length of the negative electrode body 20 in the longitudinal direction (870.0 mm) by the natural number 3, conditional expression (1) is satisfied. The length L of the positive electrode body 10 in the longitudinal direction is 690.0 mm, the number n of the positive electrode current collecting tabs 12 is 2, and the width W of the positive electrode current collecting tabs 12 is 2.0 mm. Substituting into equation (2) gives 0.994, which satisfies conditional expression (2).

(Example 5)
Except the production of the negative electrode body 20, it was the same as that of Example 1, and 10 lithium ion batteries having a theoretical capacity of 1.5 Ah were produced. Referring to FIG. 9, the negative electrode layer 21 is composed of a negative electrode active material, a binder and a thickener, using natural graphite as the negative electrode active material, using SBR as the binder, and as a thickener. Carboxymethyl cellulose was used. Copper foil was used for the negative electrode current collector foil. After drying the laminated body which apply | coated the negative electrode layer 21 to negative electrode current collector foil, it rolled with the roll. The rolled laminate was cut into a width of 56.0 mm to obtain a hoop of the negative electrode body 20. The length of the hoop of the negative electrode body 20 in the longitudinal direction was adjusted to 870.0 mm. Two negative electrode current collecting tabs 22 were arranged so as to face the positive electrode current collecting tabs 12 of the positive electrode body 10, and these negative electrode current collecting tabs 22 were joined to the positive electrode body 10 by ultrasonic welding. The negative electrode current collecting tab 22 was made of nickel.

  Since the interval between the adjacent positive electrode current collecting tabs 12 is 290.0 mm obtained by dividing the length of the negative electrode body 20 in the longitudinal direction (870.0 mm) by the natural number 3, conditional expression (1) is satisfied. The length L of the positive electrode body 10 in the longitudinal direction is 690.0 mm, the number n of the positive electrode current collecting tabs 12 is 2, and the width W of the positive electrode current collecting tabs 12 is 5.0 mm. Substituting into equation (2) yields 0.986, which satisfies conditional expression (2).

(Comparative Example 1)
Except the production of the positive electrode body 10, the same procedure as in Example 1 was conducted, and 10 lithium ion batteries with a theoretical capacity of 1.6 Ah were produced. Referring to FIG. 10, a hoop of positive electrode body 10 was obtained, and the length of the hoop in the longitudinal direction was adjusted to 690.0 mm. Two positive electrode current collecting tabs 12 were provided at 290.0 mm intervals, and these positive electrode current collecting tabs 12 were fixed to the positive electrode body 10 by ultrasonic welding. The positive electrode current collecting tab 12 located on the left side was arranged at a position away from the end in the longitudinal direction of the positive electrode body 21 by 218.0 mm. The positive electrode current collecting tab 12 was made of aluminum and adjusted to a size of a width of 1.0 mm, a thickness of 0.1 mm, and a length of 50.0 mm. That is, the size of the positive electrode current collecting tab 12 was changed from that in Example 1.

  Since the interval between the adjacent positive electrode current collecting tabs 12 is 290.0 mm obtained by dividing the length of the negative electrode body 20 in the longitudinal direction (870.0 mm) by the natural number 3, conditional expression (1) is satisfied. The length L of the positive electrode body 10 in the longitudinal direction is 690.0 mm, the number n of the positive electrode current collecting tabs 12 is 2, and the width W of the positive electrode current collecting tabs 12 is 1.0 mm. Substituting into equation (2) gives 0.997, which does not satisfy conditional expression (2).

(Comparative Example 2)
Except the production of the positive electrode body 10, the same procedure as in Example 1 was carried out, and 10 lithium ion batteries having a theoretical capacity of 1.3 Ah were produced. Referring to FIG. 11, a hoop of positive electrode body 10 was obtained, and the length of the hoop in the longitudinal direction was adjusted to 690.0 mm. Two positive electrode current collecting tabs 12 were provided at 290.0 mm intervals, and these positive electrode current collecting tabs 12 were fixed to the positive electrode body 10 by ultrasonic welding. The positive electrode current collecting tab 12 located on the left side was arranged at a position away from the end in the longitudinal direction of the positive electrode body 21 by 218.0 mm. The positive electrode current collecting tab 12 was made of aluminum and adjusted to a size of 40.0 mm in width, 0.1 mm in thickness, and 50.0 mm in length. That is, the size of the positive electrode current collecting tab 12 was changed from that in Example 1.

  Since the interval between the adjacent positive electrode current collecting tabs 12 is 290.0 mm obtained by dividing the length of the negative electrode body 20 in the longitudinal direction (870.0 mm) by the natural number 3, conditional expression (1) is satisfied. The length L of the positive electrode body 10 in the longitudinal direction is 690.0 mm, the number n of the positive electrode current collecting tabs 12 is 2, and the width W of the positive electrode current collecting tabs 12 is 40.0 mm. Substituting into the formula (2) is 0.884, which does not satisfy the conditional formula (2).

(Comparative Example 3)
FIG. 12 is a plan view of the positive electrode body 10 and the negative electrode body 20 of Comparative Example 3. The positive electrode layer 11 is composed of a positive electrode active material, a binder, and a conductive agent. Lithium cobaltate is used as the positive electrode active material, PVDF is used as the binder, and acetylene black is used as the conductive agent. An aluminum foil was used for the current collector 13. The positive electrode layer 11 was applied to the current collector 13 and dried, and then rolled into a sheet with a roll. The rolled sheet was cut into a width of 54.0 mm to obtain a hoop of the positive electrode body 10. The length in the longitudinal direction of the hoop of the positive electrode body 10 was adjusted to 2000.0 mm. The positive electrode current collecting tab 12 was joined by ultrasonic welding at a position distant from the end in the longitudinal direction by 1233.0 mm. The positive electrode current collecting tab 12 was made of aluminum and adjusted to a size of width 5.0 mm, thickness 0.1 mm, and length 50.0 mm.

The negative electrode layer 21 is composed of a negative electrode active material, a binder, and a thickener, natural graphite is used as the negative electrode active material, SBR is used as the binder, and carboxymethyl cellulose is used as the thickener. A copper foil was used for the current collector 23. The negative electrode layer 21 was applied to the current collector 23 and dried, and then rolled into a sheet with a roll. The rolled sheet was cut into a width of 56.0 mm to obtain a hoop of the negative electrode body 20. The length of the hoop of the negative electrode body 20 in the longitudinal direction was adjusted to 2610.0 mm. The negative electrode current collecting tab 22 was joined to both ends in the longitudinal direction of the negative electrode body 20 by ultrasonic welding. The negative electrode current collecting tab 22 was made of nickel.
The electrolytic solution was the same as in Example 1.

  Since the comparative example 3 has only one positive electrode current collection tab 12, it does not satisfy conditional expression (1). The length L in the longitudinal direction of the positive electrode body 10 is 2000.0 mm, the number n of the positive electrode current collecting tabs 12 is 1, and the width W of the positive electrode current collecting tabs 12 is 30.0 mm. Substituting into equation (2) yields 0.985, which satisfies conditional expression (2).

  Table 1 shows the evaluation results of Examples 1 to 5 and Comparative Examples 1 to 3. When the capacity retention rate was higher than 65.0% and the number of defective cells was 0, the result was evaluated as “good” as good. Although the capacity retention ratio was higher than 65.0%, when a defective cell was generated, the result was evaluated as “good” because the result was generally good. When the capacity maintenance rate was less than 65.0%, the result was evaluated as x because the result was defective. FIG. 13 is a graph of the evaluation results in Table 1.

  From these results, it was proved that a battery having a high capacity retention rate can be provided by satisfying conditional expressions (1) and (2).

(Modification 1)
Although the lithium ion battery has been described in the above-described embodiment, the present invention is not limited to this and can be applied to other secondary batteries. The other secondary battery may be a nickel metal hydride battery.

DESCRIPTION OF SYMBOLS 1 Lithium ion battery 5 Cylindrical case 10 Positive electrode body 11 Positive electrode layer
DESCRIPTION OF SYMBOLS 12 Positive electrode current collection tab 13 Current collector 20 Negative electrode body 21 Negative electrode layer 22 Negative electrode current collection tab 23 Current collector 30 Separator

Claims (6)

In a secondary battery including a wound body in which a power generation sheet extending in a strip shape in which a positive electrode body and a negative electrode body are stacked via a separator is wound,
The length of one electrode body in the winding direction of the positive electrode body and the negative electrode body is M (mm), the length of the other electrode body in the winding direction is L (mm), and the length of the other electrode body is N is the number of first current collecting tabs connected side by side in the winding direction, T is the interval between the first current collecting tabs adjacent to each other, and the width of the first current collecting tab is A secondary battery characterized by satisfying the following conditional expressions (1) and (2) when W (mm).
M / natural number = T (1)
0.898 <1-{(W × n) / L} <0.995 (2)   The secondary battery according to claim 1, wherein the one electrode body is the negative electrode body, and the other electrode body is the positive electrode body.   3. The secondary battery according to claim 2, wherein the second current collecting tab connected to the one electrode body is provided at a position that does not overlap the positive electrode body when viewed in the thickness direction of the power generation sheet. .   The first power collecting tab and the second current collecting tab connected to the one electrode body are provided at positions that do not overlap each other in the thickness direction view of the power generation sheet. 2. The secondary battery according to 2. The power generation element is a power generation element of a lithium ion battery,
5. The secondary battery according to claim 1, wherein the wound body is housed together with an electrolytic solution in a cylindrical case. An assembled battery for a vehicle in which a plurality of the secondary batteries according to any one of claims 1 to 5 are connected.

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