JP2015159029A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery which enables both of the improvement of high-rate charge and discharge characteristics, and the prevention of the increase in I-V resistance.SOLUTION: A nonaqueous electrolyte secondary battery comprises: an electrode body having a positive electrode, a negative electrode, a separator provided between the positive and negative electrodes, and an uncoated part of a collector, which is provided at one end of an electrode plate of at least one of the positive and negative electrodes in a widthwise direction thereof, and on which a mixture layer is not provided; an electrolyte at least held by the separator; a bag-shaped member in which the electrode body is provided, and which is put in contact with at least part of the external surface of the electrode body as a result of its heat shrinkage; and a collector lead connected with the uncoated part. The collector lead is provided on the uncoated part, and extends in a direction perpendicular to a widthwise direction of the electrode plate. In the direction perpendicular to the widthwise direction of the electrode plate, the collector lead located on the uncoated part is identical to the uncoated part in length.

Description

  The present invention relates to a non-aqueous electrolyte secondary battery including a bag-like member that has an electrode body provided therein and contacts at least a part of the outer surface of the electrode body by thermal contraction.

  Patent Document 1 (Japanese Patent Laid-Open No. 2013-251119) discloses that an insulating bag is tightly fixed to an electrode body by thermally shrinking the insulating bag containing the electrode body.

JP2013-251119A

  When high rate charge / discharge is performed, the temperature of the electrode body rises, and as a result, the electrolyte may expand and flow out of the electrode body. Even if the temperature of the electrode body decreases after the electrolyte flows out of the electrode body and the volume of the electrolyte returns to the state before expansion, the electrolyte does not return to the electrode body. Therefore, the electrode body lacks an electrolyte, and thus the high rate charge / discharge characteristics are deteriorated.

  The present inventors considered that if the insulating bag described in Patent Document 1 is used, the electrolyte can be prevented from flowing out of the electrode body during high-rate charge / discharge. However, according to the method described in Patent Document 1, it has been found that a current collector made of foil or the like may be deformed or damaged in an uncoated portion when the insulating bag is thermally contracted. When the current collector is deformed or broken, the IV resistance is increased. An object of the present invention is to provide a non-aqueous electrolyte secondary battery capable of achieving both improvement in high rate charge / discharge characteristics and prevention of increase in IV resistance.

  The non-aqueous electrolyte secondary battery of the present invention is provided at one end in the width direction of a positive electrode, a negative electrode, a separator provided between the positive electrode and the negative electrode, and at least one electrode plate of the positive electrode and the negative electrode. An electrode body having an uncoated portion on which no mixture layer is provided, at least an electrolyte held by a separator, and at least a part of an outer surface of the electrode body by heat shrinkage And a current collecting lead connected to the uncoated portion. The current collecting lead is provided on the uncoated portion and extends in a direction perpendicular to the width direction of the electrode plate. In the direction perpendicular to the width direction of the electrode plate, the length of the current collecting lead located on the uncoated portion is the same as the length of the uncoated portion.

  Since the bag-shaped member is in contact with at least a part of the outer surface of the electrode body, it is possible to prevent the electrolyte from flowing out of the electrode body during high-rate charge / discharge. Moreover, in the uncoated part, since the current collector is reinforced by the current collector lead, deformation or breakage of the current collector due to heat shrinkage can be prevented.

  “The width direction of the electrode plate” means a direction perpendicular to the longitudinal direction of the electrode plate in a state where no electrode body is formed and is different from the thickness direction of the electrode plate. “A direction perpendicular to the width direction of the electrode plate” is parallel to the longitudinal direction of the current collecting lead on the uncoated portion. For example, a flat electrode body (a positive electrode and a negative electrode sandwich a separator). In the case of an electrode body that is wound and formed flat, this corresponds to the major axis direction in the cross section of the electrode body.

  The “outer surface of the electrode body” includes the end surface of the electrode body at the end in the width direction of the electrode plate. For example, in a flat electrode body, the outer peripheral surface of the electrode body and the end surface of the electrode body at the end in the axial direction of the electrode body ( The tip surface of the uncoated part).

  “In the direction perpendicular to the width direction of the electrode plate, the length of the current collecting lead located on the uncoated part is the same as the length of the uncoated part” means “the width direction of the electrode plate”. In the “perpendicular to” direction, it means that the length of the current collecting lead located on the uncoated part is 0.8 to 1.2 times the length of the uncoated part.

  In the present invention, it is possible to prevent the electrolyte from flowing out of the electrode body during high-rate charge / discharge, and it is possible to prevent deformation or breakage of the current collector due to thermal shrinkage in the uncoated part, thereby improving the high-rate charge / discharge characteristics. -V resistance can be prevented from increasing.

It is a top view which shows the internal structure of the nonaqueous electrolyte secondary battery of one Embodiment of this invention. (A), (b) is a top view which shows a part of manufacturing method of the nonaqueous electrolyte secondary battery of one Embodiment of this invention in order of a process. It is a graph which shows the temperature dependence of the thermal contraction rate of the bag-shaped member used in the Example. It is a graph which shows the measurement result of the increase rate of reaction resistance.

  The present invention will be described below with reference to the drawings. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

  Hereinafter, the bag-like member after heat shrink is referred to as “first bag-like member”, and the bag-like member before heat shrink is referred to as “second bag-like member”. That is, the second bag-like member is thermally contracted to become the first bag-like member.

[Configuration of non-aqueous electrolyte secondary battery]
FIG. 1 is a plan view showing an internal structure of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. The case body 1A of the battery case 1 is provided with an electrode body 11, a first bag-like member 31, and an electrolyte (not shown), and the lid body 1B of the battery case 1 is provided with a positive electrode terminal 3 and a negative electrode terminal 7. ing.

  The electrode body 11 is formed in a flat shape by winding a positive electrode 13 and a negative electrode 17 with a separator 15 interposed therebetween. The positive electrode 13 includes a positive electrode current collector 13A and a positive electrode mixture layer 13B provided on the positive electrode current collector 13A. One end in the width direction of the positive electrode 13 is provided with a positive electrode uncoated portion 13D in which the positive electrode mixture layer 13B is not provided in the positive electrode current collector 13A. The negative electrode 17 includes a negative electrode current collector 17A and a negative electrode mixture layer 17B provided on the negative electrode current collector 17A. One end in the width direction of the negative electrode 17 is provided with a negative electrode uncoated portion 13D in which the negative electrode mixture layer 17B is not provided in the negative electrode current collector 17A. The positive electrode uncoated portion 13D of the positive electrode 13 and the negative electrode uncoated portion 17D of the negative electrode 17 protrude in opposite directions from the separator 15 in the axial direction of the electrode body 11, and the positive electrode uncoated portion 13D The negative electrode uncoated portion 17D is connected to the negative electrode terminal 7 via a negative electrode lead 27 (current collecting lead). The electrolyte is held at least in the separator 15.

  In the present embodiment, the electrode body 11 is provided inside the first bag-shaped member 31, and the first bag-shaped member 31 is in contact with at least a part of the outer surface of the electrode body 11 due to thermal contraction. Thereby, it is possible to prevent the electrolyte from flowing out from the electrode body 11 at the contact portion between the first bag-shaped member 31 and the outer surface of the electrode body 11 during high-rate charging / discharging, so that the electrolyte in the electrode body 11 can be prevented from withstanding. Therefore, the high rate charge / discharge characteristics are improved.

  In addition, since the electrolyte in the electrode body 11 can be prevented from dying, it is possible to prevent unevenness in resistance in the electrode body 11. Thereby, since precipitation of lithium metal can be prevented, generation | occurrence | production of the internal short circuit resulting from precipitation of lithium metal can be prevented. Therefore, it is possible to prevent a decrease in thermal stability.

  Furthermore, in this embodiment, in the direction perpendicular to the width direction of the positive electrode 13, the length of the positive electrode lead 23 (shaded area in FIG. 1) located on the positive electrode uncoated portion 13D is the positive electrode uncoated portion 13D. Is the same length. The thickness of the positive electrode lead 23 is larger than the thickness of the positive electrode current collector 13A. For example, the thickness of the positive electrode current collector 13A is 10 μm or more and 500 μm or less, while the thickness of the positive electrode lead 23 is 1 mm or more and 20 mm or less. Therefore, the positive electrode current collector 13 </ b> A is reinforced by the positive electrode lead 23 in the positive electrode uncoated portion 13 </ b> D. Therefore, even if an external force is applied to the positive electrode uncoated portion 13D due to, for example, heat shrinkage of the second bag-like member 131 (see FIG. 2B), the positive electrode current collector 13A in the positive electrode uncoated portion 13D is deformed. Or damage etc. can be prevented. Therefore, since the conductive state between the positive electrode uncoated portion 13D and the positive electrode lead 23 can be secured, the IV resistance can be kept low.

  Similarly, in the direction perpendicular to the width direction of the negative electrode 17, the length of the negative electrode lead 27 (shaded area in FIG. 1) located on the negative electrode uncoated portion 17D is the same as the length of the negative electrode uncoated portion 17D. It is. The thickness of the negative electrode lead 27 is larger than the thickness of the negative electrode current collector 17A. For example, the thickness of the negative electrode current collector 17A is 10 μm or more and 500 μm or less, while the thickness of the negative electrode lead 27 is 1 mm or more and 20 mm or less. Therefore, the negative electrode current collector 17 </ b> A is reinforced by the negative electrode lead 27 in the negative electrode uncoated portion 17 </ b> D. Therefore, for example, even if an external force is applied to the negative electrode uncoated portion 17D due to heat shrinkage or the like of the second bag-like member 131 (see FIG. 2B), the deformation of the negative electrode current collector 17A in the negative electrode uncoated portion 17D. Or damage etc. can be prevented. Therefore, since the conductive state between the negative electrode uncoated portion 17D and the negative electrode lead 27 can be ensured, the IV resistance can be kept low. Note that it is sufficient that at least one of the positive electrode lead 23 and the negative electrode 27 has the above-described configuration.

  As described above, in this embodiment, it is possible to prevent the occurrence of a new problem due to heat shrinkage (such as deformation or breakage of the current collector in an uncoated part), so that the high-rate charge / discharge characteristics are improved and the IV resistance is improved. Both increase prevention can be achieved. In addition, the thermal stability can be maintained high. Therefore, the non-aqueous electrolyte secondary battery of this embodiment is suitable as a large battery used for a power source for automobiles such as a hybrid vehicle or an electric vehicle, a factory power source, a household power source, or the like. Hereinafter, the positive electrode lead 23, the negative electrode lead 27, and the first bag-like member 31 are sequentially shown.

(Positive lead, negative lead)
The positive electrode lead 23 is preferably provided in a portion of the positive electrode uncoated portion 13D located on the outermost periphery of the electrode body 11. The positive electrode lead 23 preferably has a conventionally known configuration as the positive electrode lead of the nonaqueous electrolyte secondary battery except for the length in the direction perpendicular to the width direction of the positive electrode 13.

  Similarly, the negative electrode lead 27 is preferably provided in a portion of the negative electrode uncoated portion 17D located on the outermost periphery of the electrode body 11. The negative electrode lead 27 preferably has a conventionally known configuration as the negative electrode lead of the nonaqueous electrolyte secondary battery, except for the length in the direction perpendicular to the width direction of the negative electrode 17.

(First bag-shaped member)
The first bag-like member 31 is preferably open on the opening side of the case body 1A. The side portion of the first bag-shaped member 31 is preferably opposed to the side surface of the case body 1A, and is opposed to or in contact with the end surface of the electrode body 11 (the end surface of the electrode body 11 at the axial end portion of the electrode body 11). It is preferable.

  The first bag-shaped member 31 is preferably provided so that the electrode body 11 does not protrude from the opening of the first bag-shaped member 31. Thereby, the 1st bag-shaped member 31 can hold | maintain the quantity of electrolyte required for charging / discharging reaction. Therefore, the high rate charge / discharge characteristics are further improved.

  The first bag-shaped member 31 is preferably in contact with at least a part of the end surface of the electrode body 11. This prevents the electrolyte held between the positive electrode 13 and the negative electrode 17 from flowing out of the electrode body 11 at the time of high-rate charge / discharge, so that the amount of electrolyte necessary for the charge / discharge reaction is reduced between the positive electrode 13 and the negative electrode 17. It will be held between. Therefore, the high rate charge / discharge characteristics are further improved. More preferably, the first bag-shaped member 31 is in contact with the entire end surface of the electrode body 11, and may be in contact with not only the end surface of the electrode body 11 but also the outer peripheral surface of the electrode body 11.

  The first bag-shaped member 31 is preferably made of a material that thermally contracts at a preset contraction rate, and thereby contacts at least a part of the outer surface of the electrode body 11 by thermal contraction. More preferably, the thermal contraction rate of the material constituting the first bag-shaped member 31 is 5% or more and 60% or less.

  More preferably, in the first bag-shaped member 31, the thermal contraction rate in the direction in which the bottom extends (corresponding to the width direction of the positive electrode 13 or the negative electrode 17) is the direction in which the side extends (in the width direction of the positive electrode 13 or the negative electrode 17). Higher than the heat shrinkage rate in the direction perpendicular to the vertical direction). Thereby, the 1st bag-shaped member 31 becomes easy to contact at least one part of the end surface of the electrode body 11 by heat contraction. More preferably, in the first bag-shaped member 31, the heat shrinkage rate in the direction in which the bottom portion extends is 10% or more and 60% or less, and the heat shrinkage rate in the direction in which the side portion extends is 5% or more and 20% or less.

  The first bag-shaped member 31 is preferably made of a material that thermally contracts below the temperature at which the separator 15 shuts down. Thereby, generation | occurrence | production of the internal short circuit resulting from heat contraction can be prevented. Moreover, it is preferable that the 1st bag-shaped member 31 consists of a material which does not react with electrolyte, and it is preferable that it is comprised so that electrolyte may not permeate | transmit. From the above, the first bag-like member 31 is preferably made of a copolymer resin of PET (polyethylene terephthalate) and PP (polypropylene).

  If the first bag-shaped member 31 is made of the above material, a gap is generated between the first bag-shaped member 31 and the outer surface of the electrode body 11 even if gas is generated during use of the nonaqueous electrolyte secondary battery. Can be prevented. Thereby, the performance of the non-aqueous electrolyte secondary battery can be maintained high even if the high rate charge / discharge is repeated. Therefore, even when compared with a laminated battery using a battery case made of a laminated film without using the first bag-shaped member 31, the high rate charge / discharge characteristics are improved.

[Manufacture of non-aqueous electrolyte secondary batteries]
2A and 2B are plan views showing a part of the manufacturing method of the nonaqueous electrolyte secondary battery of this embodiment in the order of steps. First, the electrode body 11 is manufactured according to a conventionally known method.

  Next, the positive electrode lead 23 is connected to the positive electrode uncoated portion 13D. Specifically, the positive electrode lead 23 extends from one end (lower end) of the positive electrode uncoated portion 13D to the other end (upper end) of the positive electrode uncoated portion 13D in the direction perpendicular to the width direction of the positive electrode 13, and the other end. The positive electrode lead 23 is provided on the positive electrode uncoated portion 13D so as to extend from the electrode body 11 to the outside of the electrode body 11 (FIG. 2A). Thereby, the positive electrode current collector 13 </ b> A is reinforced by the positive electrode lead 23 in the positive electrode uncoated portion 13 </ b> D. Thereafter, the positive electrode lead 23 is welded to the positive electrode uncoated portion 13D.

  Similarly, the negative electrode lead 27 is connected to the negative electrode uncoated portion 17D. Specifically, the negative electrode lead 27 extends from one end (lower end) of the negative electrode uncoated portion 17D to the other end (upper end) of the negative electrode uncoated portion 17D in the direction perpendicular to the width direction of the negative electrode 17, and the other end. The negative electrode lead 27 is provided on the negative electrode uncoated portion 17D so as to extend from the electrode body 11 to the outside of the electrode body 11 (FIG. 2A). Thereby, the negative electrode current collector 17 </ b> A is reinforced by the negative electrode lead 27 in the negative electrode uncoated portion 17 </ b> D. Thereafter, the negative electrode lead 27 is welded to the negative electrode uncoated portion 17D.

  Subsequently, the electrode body 11 is provided inside the second bag-like member 131 made of a heat shrinkable material. Preferably, the end surface of the electrode body 11 is opposed to the side portion of the second bag-like member 131. Thereafter, the electrode body 11 provided inside the second bag-like member 131 is placed in the case main body 1A. Preferably, the second bag-shaped member 131 is opened on the opening side of the case main body 1A, and the side portion of the second bag-shaped member 131 is opposed to the side surface of the case main body 1A.

  The second bag-shaped member 131 preferably has an internal volume larger than the volume of the electrode body 11, and the electrode body 11 is preferably provided so that the electrode body 11 does not protrude from the opening of the second bag-shaped member 131. In the second bag-like member 131, the thermal contraction rate in the direction in which the bottom extends (corresponding to the width direction of the positive electrode 13 or the negative electrode 17) is perpendicular to the direction in which the side extends (the width direction of the positive electrode 13 or the negative electrode 17). It is preferably higher than the heat shrinkage rate in the direction).

  Subsequently, the positive electrode terminal 3 and the positive electrode lead 23 are connected, the negative electrode terminal 7 and the negative electrode lead 27 are connected, and then the opening of the case main body 1A is covered with the lid body 1B (FIG. 2B). If the second bag-like member 131 is opened on the opening side of the case main body 1A, the positive electrode terminal 3 and the positive electrode lead 23 can be easily connected, and the negative electrode terminal 7 and the negative electrode lead 27 can be easily connected. In addition, after connecting the positive electrode terminal 3 and the positive electrode lead 23 and connecting the negative electrode terminal 7 and the negative electrode lead 27, the electrode body 11 may be provided inside the second bag-shaped member 131 made of a heat-shrinkable material. .

  Subsequently, an electrolyte is injected from the injection hole 9 formed in the lid 1B. If the second bag-like member 131 is open on the opening side of the case main body 1A, the electrolyte can be easily injected into the second bag-like member 131. If the electrode body 11 is provided inside the second bag-like member 131 so as not to protrude from the opening of the second bag-like member 131, an amount of electrolyte necessary for the charge / discharge reaction is injected into the second bag-like member 131. it can. Therefore, it is possible to prevent the electrolyte from overflowing from the second bag-like member 131.

  When the electrolyte is held at least by the separator 15, the case body 1A is heated from the outside (FIG. 2B). As a result, the second bag-shaped member 131 is thermally contracted, and the first bag-shaped member 31 is in contact with at least a part of the outer surface of the electrode body 11. Thus, after the electrolyte is held at least by the separator 15, the second bag-like member 131 is thermally contracted. Therefore, the high rate charge / discharge characteristics are improved without degrading the electrolyte injection property.

  Further, in the positive electrode uncoated portion 13D, since the positive electrode current collector 13A is reinforced by the positive electrode lead 23, deformation or breakage of the positive electrode current collector 13A due to thermal contraction can be prevented. Similarly, in the negative electrode uncoated portion 17D, since the negative electrode current collector 17A is reinforced by the negative electrode lead 27, deformation or breakage of the negative electrode current collector 17A due to thermal contraction can be prevented.

  In the second bag-like member 131, if the thermal contraction rate in the direction in which the bottom portion extends is higher than the thermal contraction rate in the direction in which the side portion extends, the thermal contraction amount in the direction in which the bottom portion extends is greater than the thermal contraction amount in the direction in which the side portion extends. Also grows. Therefore, the first bag-shaped member 31 can easily come into contact with at least a part of the end surface of the electrode body 11. In addition, the electrode body 11 can be prevented from protruding from the opening of the first bag-shaped member 31.

  The heating conditions are not particularly limited. For example, the heating temperature is preferably equal to or higher than the contraction temperature of the second bag-like member 131, and more preferably less than the temperature at which the separator 15 shuts down. Thereby, since the 2nd bag-shaped member 131 heat-shrinks without being accompanied by the heat shrink of the separator 15, generation | occurrence | production of the internal short circuit by the heat shrink of the 2nd bag-shaped member 131 can be prevented.

  Thereafter, the injection hole 9 is covered. Thereby, the nonaqueous electrolyte secondary battery of this embodiment can be obtained.

Hereinafter, the present invention will be specifically described, but the present invention is not limited to the following configurations.
[Example]
(Preparation of positive electrode)
As a positive electrode active material, a powder made of a lithium-containing transition metal composite oxide containing Li and three transition metal elements (Co, Ni, and Mn) was prepared. Mix the positive electrode active material, acetylene black (conductive agent) and polyvinylidene fluoride (binder) so that the mass ratio is 90: 8: 2, dilute with NMP (N-methylpyrrolidone), and mix the positive electrode mixture paste Got.

  The positive electrode mixture paste was applied to both sides of the Al foil and dried so that one end in the width direction of the Al foil (positive electrode current collector, thickness: 15 μm) was exposed. Thereby, the positive mix layer was formed on both surfaces of the Al foil. Then, the positive mix layer and Al foil were rolled using the roll mill. In this way, a positive electrode having a positive electrode uncoated portion (a portion of the positive electrode current collector where the positive electrode mixture layer was not provided) was obtained.

(Preparation of negative electrode)
A carbon material having natural graphite as a core material was prepared as a negative electrode active material. Mix the negative electrode active material, CMC (carboxymethylcellulose) (thickener) and SBR (Styrene-butadiene rubber) (binder) so that the mass ratio is 98: 1: 1 and dilute with water. Thus, a negative electrode mixture paste was obtained.

  The negative electrode mixture paste was applied to both sides of the Cu foil and dried so that one end in the width direction of the Cu foil (negative electrode current collector, thickness 10 μm) was exposed. Thereby, the negative mix layer was formed in both surfaces of Cu foil. Then, the negative mix layer and Cu foil were rolled using the roll mill. In this way, a negative electrode having a negative electrode uncoated portion (a portion where the negative electrode mixture layer was not provided in the negative electrode current collector) was obtained.

(Production and insertion of wound electrode body)
A separator made of PE (polyethylene) was prepared. A separator is provided between the positive electrode mixture layer and the negative electrode mixture layer, and the positive electrode, the negative electrode, and the separator so that the positive electrode uncoated portion and the negative electrode uncoated portion protrude in the opposite direction from the separator in the width direction of the Al foil. And provided. Next, a winding shaft (not shown) was arranged so as to be parallel to the width direction of the Al foil, and the positive electrode, the separator, and the negative electrode were wound using the winding shaft. A pressure of 4 kN / cm ² was applied to the obtained cylindrical electrode body at room temperature for 2 minutes to obtain a flat electrode body.

  Next, the positive electrode lead (thickness: 1 mm) extends from one end (lower end) of the positive electrode uncoated portion to the other end (upper end) of the positive electrode uncoated portion in a direction perpendicular to the width direction of the positive electrode, and the other end The positive electrode lead was provided on the portion of the positive electrode uncoated portion located on the outermost periphery of the electrode body so as to extend from the electrode body to the outside of the electrode body. Thereafter, the positive electrode lead was welded to the positive electrode uncoated portion. According to the same method, a negative electrode lead (thickness: 1 mm) was welded to the negative electrode uncoated portion.

  Next, a second bag-like member made of a copolymer resin of PET and PP was prepared. When this second bag-shaped member was heated and the heat shrinkage rate was examined, the heat shrinkage rate was found to be greater in the horizontal direction (the direction in which the bottom portion extends) than in the vertical direction (the direction in which the side portion extends). Okay (Figure 3).

  Subsequently, the electrode body was put in the bag-like member so that the end face of the electrode body was opposed to the side portion of the bag-like member. The electrode body contained in the bag-like member was placed in the case body so that the opening of the bag-like member was positioned on the opening side of the case body. Thereafter, the positive electrode lead and the positive electrode terminal were connected, the negative electrode lead and the negative electrode terminal were connected, and then the opening of the case body was closed with a lid.

(Preparation and injection of electrolyte)
EC (ethylene carbonate), DMC (dimethyl carbonate), and EMC (ethyl methyl carbonate) were mixed so that the volume ratio was 1: 1: 1 to obtain a mixed solvent. LiPF ₆ was put in the mixed solvent so that the concentration was 1.0 mol / L. The prepared electrolyte was injected from the injection hole of the lid. Thereafter, the inside of the battery case was depressurized. As a result, at least the separator was impregnated with the electrolytic solution.

(Heat shrink)
Hot air (80 ° C.) was applied to the entire outer surface of the case body so that the heat shrinkage rate of the bag-shaped member in the lateral direction was 30% or more. Thereafter, the injection hole was sealed. Thus, the lithium ion secondary battery of the present Example was obtained.

(Increase rate of reaction resistance)
The SOC of the lithium ion secondary battery was adjusted to 60%. In a thermostat adjusted to −30 ° C., the impedance of the lithium ion secondary battery was measured by the AC impedance method. Using a frequency response analyzer (manufactured by Toyo Corporation, model number “1255B”) and potentio / galvanostat (model number “1287A” manufactured by solartron), while changing the frequency from 0.001 to 100,000 Hz, the lithium ion secondary The impedance of the battery was measured. The size of the diameter of the semicircle in the obtained Nyquist plot was defined as the reaction resistance (initial reaction resistance).

  Next, a high rate cycle test was performed on the lithium ion secondary battery. In this test, a CC (constant-current) charge having a constant current value of 2C and a CC discharge having a constant current value of 2 / 5C were defined as one cycle in an environment of −15 ° C. And five kinds of tests which differ only in the number of cycles were done.

Subsequently, after the secondary battery after each high-rate cycle test was adjusted to a state of SOC 60%, the reaction resistance during durability was measured according to the initial reaction resistance measurement method. The increase rate of reaction resistance was calculated | required using following formula (1).
(Increase rate of reaction resistance) = (Change amount of reaction resistance before and after cycle test) ÷ (Initial reaction resistance) Formula (1).

[Comparative example]
In the comparative example, in the direction perpendicular to the width direction of the electrode plate, the length of the positive electrode lead located on the positive electrode uncoated part is about 0.2 times the length of the positive electrode uncoated part. The length of the negative electrode lead located on the uncoated part was about 0.2 times the length of the negative electrode uncoated part. Except for the points other than this, a lithium ion secondary battery was manufactured in accordance with the method described in the above example, and the rate of increase in reaction resistance was determined.

(Discussion)
The results are shown in FIG. The rate of increase in reaction resistance was lower in the Examples than in the Comparative Examples. This effect became more prominent as the total energization amount increased (as the number of cycles in the high-rate cycle test increased).

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Battery case, 1A case main body, 1B cover body, 3 positive electrode terminal, 7 negative electrode terminal, 9 injection hole, 11 electrode body, 13 positive electrode, 13A positive electrode current collector, 13D positive electrode uncoated part, 15 separator, 17 Negative electrode, 17A Negative electrode current collector, 17D Negative electrode uncoated portion, 23 Positive electrode lead, 27 Negative electrode lead, 31 First bag-like member, 131 Second bag-like member.

Claims (1)

A positive electrode, a negative electrode, a separator provided between the positive electrode and the negative electrode, and provided at one end in a width direction of at least one of the positive electrode and the negative electrode; An electrode body having an uncoated portion that is not provided;
At least an electrolyte held in the separator;
The electrode body is provided inside, and a bag-like member that contacts at least a part of the outer surface of the electrode body by heat shrinkage;
A current collecting lead connected to the uncoated part,
The current collecting lead is provided on the uncoated portion and extends in a direction perpendicular to the width direction of the electrode plate,
A non-aqueous electrolyte secondary battery in which a length of a current collecting lead located on the uncoated part is the same as a length of the uncoated part in a direction perpendicular to the width direction of the electrode plate.

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