JP2017098017A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery reduced in the risk of precipitation of a charge carrier-originating substance.SOLUTION: A nonaqueous electrolyte secondary battery 100 according to the present invention comprises: a wound electrode body 20; a nonaqueous electrolyte solution; and a battery case 30. The wound electrode body 20 has a pair of R parts 22, and a center flat part 24 having a pair of flat surfaces 26 located between the paired R parts. The outer surface of the wound electrode body 20 is partially covered with a heat shrinkable annular member 80 which is disposed to be opposed to the outer surface of the pair of R parts 22 and the pair of flat surfaces 26. In the nonaqueous electrolyte secondary battery, the annular member 80 is disposed around the wound electrode body 20 in the state of being shrunk by heat. The annular member 80 has holes formed therein. A total opening area (S) of the holes formed in the annular member 80 is 40% of an area (S) of the outer surface of the wound electrode body 20 covered by the annular member 80.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  In recent years, non-aqueous electrolyte secondary batteries such as lithium secondary batteries have become increasingly important as power sources for mounting on vehicles or power sources for personal computers and portable terminals. In particular, a lithium secondary battery that is lightweight and has a high energy density is preferably used as a high-output power source for mounting on a vehicle.

A typical example of this type of non-aqueous electrolyte secondary battery is a battery including a wound electrode body in which a positive electrode and a negative electrode are wound through a separator. In such a non-aqueous electrolyte secondary battery, the negative electrode active material layer formed on the negative electrode and the positive electrode active material layer formed on the positive electrode are arranged to face each other.
In this type of non-aqueous electrolyte secondary battery, generally, charge carriers (for example, lithium ions) travel between a positive electrode active material layer containing a positive electrode active material and a negative electrode active material layer containing a negative electrode active material. Thus, charging and discharging are performed. Focusing on the negative electrode active material layer, charge carriers are occluded in the negative electrode active material layer during charging, and charge carriers occluded during charging are discharged from the negative electrode active material layer into the non-aqueous electrolyte during discharging.

JP 2014-086293 A Japanese Patent Laid-Open No. 10-241743

  By the way, in the non-aqueous electrolyte secondary battery having the above-described configuration, a substance (for example, metallic lithium) derived from the charge carrier may be deposited on the negative electrode active material layer depending on the configuration of the battery or the intended use of the battery. Since the substance (for example, metallic lithium) derived from the charge carrier deposited on the negative electrode active material layer is not used for the battery reaction, the battery capacity may be reduced. In addition, substances derived from the deposited charge carriers are not preferable because they cause an internal short circuit.

For example, a non-aqueous electrolyte secondary battery is generally formed such that the width and length of the negative electrode active material layer are wider than the positive electrode active material layer, and the negative electrode active material layer covers the positive electrode active material layer. A positive electrode and a negative electrode are overlaid. That is, in the battery having such a configuration, the negative electrode active material layer includes a facing portion that faces the positive electrode active material layer and a non-facing portion that does not face the positive electrode active material.
About such a non-aqueous electrolyte secondary battery, it is used for applications in which charging / discharging (charging / discharging at a high input / output density in particular) is frequently repeated at short intervals (for example, applications in which high-rate charging / discharging is repeated, such as in-vehicle batteries) And the concentration of charge carriers at the end portion of the opposing portion of the negative electrode active material layer close to the non-opposing portion (typically, the end portion adjacent to the non-opposing portion of the opposing portion of the negative electrode active material layer) is locally It tends to increase. In general, a portion of the negative electrode active material layer where the charge carrier concentration is locally high is locally overcharged, and a substance derived from the charge carrier (for example, metallic lithium) is deposited on the portion. It tends to be.
Patent Document 1 discloses that on the negative electrode active material layer, the retention of the non-aqueous electrolyte in the portion facing the non-facing portion of the negative electrode active material layer in the separator facing the negative electrode active material layer is reduced. Describes a technique for reducing the precipitation of substances derived from charge carriers.

However, although the technique described in Patent Document 1 can reduce the deposition of a substance derived from the charge carrier in the non-opposing portion of the negative electrode active material layer, depending on the configuration of the wound electrode body, the charge carrier In some cases, the material derived from the material was deposited on the negative electrode active material layer.
As one aspect of the non-aqueous electrolyte secondary battery, a flat wound electrode body having two flat portions facing each other and two curved portions (R portion) interposed between the two flat portions is provided. Examples are given. In such a flat wound electrode body, typically, the distance between the electrodes in the curved portion (the distance between the negative electrode and the positive electrode facing each other) is larger than the distance between the electrodes in the flat portion. There is a tendency. When a non-aqueous electrolyte secondary battery having an electrode body with uneven distance between the electrodes is charged as described above, the resistance of the negative electrode is increased where the distance between the electrodes is large, and the charge carrier is formed on the negative electrode active material layer. The derived material (typically metallic lithium) tends to precipitate. Therefore, Patent Document 2 describes a technique in which a heat-shrinkable annular member is disposed on the outer peripheral surface of the wound electrode body in order to reduce the looseness of the wound electrode body in the outer diameter direction.

However, according to the study by the inventors, in the technique described in Patent Document 2, the non-aqueous electrolyte is introduced into the wound electrode body by disposing the heat-shrinkable member on the outer peripheral surface of the wound electrode body. It has been confirmed that impregnation (penetration) may be difficult. The non-aqueous electrolyte is mainly impregnated (penetrated) into the wound electrode body in the direction from both ends of the wound electrode body in the winding axis direction toward the center in the winding axis direction, but penetrates into the wound electrode body. A part of the non-aqueous electrolyte solution can be impregnated (penetrated) into the wound electrode body from other than both ends in the winding axis direction (that is, the surface of the R portion and the flat portion). For example, it is possible to impregnate (penetrate) into the wound electrode body from the pores of a porous separator that is usually disposed on the outermost periphery of the wound electrode body or from the winding end of the wound electrode body. For this reason, when the outer peripheral surface of the wound electrode body is covered with the annular member, the nonaqueous electrolytic solution is less likely to be impregnated (penetrated) in the portion of the outer peripheral surface of the wound electrode body where the annular member is disposed. I think it may be.
When the permeability (infiltration property) of the nonaqueous electrolytic solution is lowered in a part of the wound electrode body, the liquid amount unevenness of the nonaqueous electrolytic solution easily occurs in the wound electrode body. In general, the battery reaction tends to concentrate on a portion of the electrode body where a relatively large amount of non-aqueous electrolyte exists, and a substance derived from charge carriers on the negative electrode active material layer (for example, metallic lithium) May be deposited.

  This invention is made | formed in view of this point, The main objective is to provide the battery in which it was highly suppressed that the substance derived from a charge carrier precipitated on a negative electrode active material layer.

To achieve the above object, according to the present invention, a non-aqueous electrolyte secondary comprising a flat wound electrode body, a non-aqueous electrolyte, and a battery case containing the electrode body and the non-aqueous electrolyte. A battery is provided. The wound electrode body is sandwiched between two R parts which are both ends in a direction orthogonal to the winding axis and whose outer surface excluding the laminated surface of the wound electrode body is a curved surface. A central flat portion having two flat surfaces, and the wound electrode body has a portion of the outer surface of the wound electrode body, the two R And a heat-shrinkable annular member disposed so as to face the two flat surfaces of the central flat part. Here, the annular member is disposed around the wound electrode body in a state of being contracted by heat. The annular member has a plurality of holes formed in a thermally contracted state, and a portion of the outer surface of the wound electrode body that is covered by the annular member in the thermally contracted state. The ratio of the total opening area (S _A ) of the holes formed in the annular member in the heat-shrinked state with respect to the area (S _B ) of 100% is 40%.

According to the non-aqueous electrolyte secondary battery having such a configuration, the wound electrode body is provided with a heat-shrinkable member arranged so as to face the outer surfaces of the two R portions and the two flat surfaces of the central flat portion. In addition, since it is constrained (pressed) in the direction from the outer surface of the wound electrode body toward the winding axis, unevenness occurs in the distance between the electrodes (typically, the distance between the electrodes in the R portion is the central flat portion. The risk of becoming larger than the distance between the electrodes in (1) can be reduced. Thereby, the distance between the electrodes can be made substantially constant over the entire wound electrode body, and it is preferable that the substance derived from the charge carrier is deposited on the negative electrode active material layer due to the unevenness of the distance between the electrodes. Can be reduced.
Moreover, according to the non-aqueous electrolyte secondary battery having the above-described configuration, since the hole is formed in the annular member, the non-aqueous electrolyte can be supplied into the wound electrode body through the hole. Thereby, the possibility that the impregnation property (penetration) of the non-aqueous electrolyte into the wound electrode body may be reduced by covering a part of the outer surface of the wound electrode body with the annular member. . That is, according to the non-aqueous electrolyte secondary battery having the above-described configuration, the possibility that the charge carrier-derived substance is deposited on the negative electrode active material layer due to non-uniformity in the amount of non-aqueous electrolysis in the wound electrode body is reduced. can do.
Therefore, according to the nonaqueous electrolyte secondary battery disclosed herein, it is possible to provide a battery in which the distance between the electrodes can be kept constant and the electrode body can be satisfactorily impregnated (penetrated) with the nonaqueous electrolyte. it can. That is, according to the non-aqueous electrolyte secondary battery disclosed here, a battery in which the substance derived from the charge carrier is highly suppressed from being deposited on the negative electrode active material layer can be provided.

It is a perspective view which shows typically the external shape of the nonaqueous electrolyte secondary battery which concerns on one Embodiment. It is a longitudinal cross-sectional view which follows the II-II line | wire in FIG. It is a perspective view which shows typically the relationship between the winding electrode body which concerns on one Embodiment, and the annular member arrange | positioned around this winding electrode body. FIG. 4 is a longitudinal sectional view taken along line IV-IV in FIG. 2.

Hereinafter, the present invention will be described in detail by taking a lithium secondary battery as an example as a non-aqueous electrolyte secondary battery according to an embodiment of the present invention with appropriate reference to the drawings. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Further, the lithium secondary battery is an example, and the technical idea of the present invention is also applied to other non-aqueous electrolyte secondary batteries (for example, sodium secondary batteries) having other charge carriers (for example, sodium ions). .
In the following drawings, members / parts having the same action are described with the same reference numerals, and redundant descriptions may be omitted or simplified. Further, the dimensional relationship (length, width, thickness, etc.) in each drawing does not necessarily reflect the actual dimensional relationship.

  In the present specification, the “secondary battery” generally refers to a battery that can be repeatedly charged and discharged, such as a so-called chemical battery such as a lithium secondary battery, a sodium secondary battery, and a nickel hydride secondary battery, and an electric double layer capacitor. It is a term encompassing the physical battery. In the present specification, the “lithium secondary battery” refers to a secondary battery that uses lithium ions as a charge carrier (supporting salt, supporting electrolyte) and is charged and discharged by the movement of lithium ions between the positive and negative electrodes.

  FIG. 1 shows a lithium secondary battery (lithium ion secondary battery) 100 according to an embodiment of the present invention. As shown in FIG. 2, in the lithium secondary battery 100, a flat wound electrode body 20 having a part of the outer surface covered with an annular member, together with an electrolyte solution (not shown), is a battery case (that is, an outer container) 30. Is housed in.

  The shape of the battery case 30 is not particularly limited, and may be, for example, a cylindrical shape or a cubic shape (box shape). The battery case 30 is, for example, as shown in FIGS. 1 and 2, a box-shaped (that is, a bottomed rectangular parallelepiped) case body having an opening at one end (corresponding to the upper end in a normal use state of the battery) 32 and a lid 34 that seals the opening of the case body 32. As shown in the figure, the lid 34 is provided with external terminals (a positive terminal 42 and a negative terminal 44) for external connection so that a part of the terminals protrudes from the lid 34 to the outside of the battery 100. Yes. In addition, the lid 34 is provided with an inlet (not shown) for injecting the electrolytic solution into the battery case. In addition, the internal pressure of the battery case 30 is released to a part of the battery case 30 (typically, a part of the lid 34) when the pressure in the battery case 30 becomes equal to or higher than a predetermined pressure. A safety valve 36 set as described above is provided. As a material of such a battery case, for example, a metal material (for example, aluminum) that is lightweight and has good thermal conductivity is suitable.

  As shown in FIGS. 3 and 4, the wound electrode body 20 has two end portions in a direction orthogonal to the winding axis direction, and the outer surface excluding the laminated surface of the wound electrode body 20 has a curved surface. It has a flat shape having an R portion 22 and a central flat portion 24 having two wide flat surfaces 26 that are sandwiched between both R portions.

  Although not particularly limited, as shown in FIGS. 2 and 4, the wound electrode body 20 according to the present embodiment has the battery case 30 (battery case body 32) in a direction orthogonal to the winding axis direction. The opening of the battery case main body 32 is formed in a posture in which the winding axis WL of the wound electrode body 20 lies sideways, that is, in the normal direction of the winding axis WL of the wound electrode body 20. The two R portions 22 are accommodated in the battery case 30 so as to face the bottom surface of the battery case 30 or the lid 34.

  The wound electrode body 20 includes a positive electrode 50 including a positive electrode active material layer 54 including at least a positive electrode active material formed along a longitudinal direction on one side or both sides (here, both sides) of an elongated positive electrode current collector 52; The negative electrode 60 provided with the negative electrode active material layer 64 containing at least the negative electrode active material formed along the longitudinal direction on one side or both sides (here, both sides) of the long negative electrode current collector 62, They are stacked (overlapped) via a scale separator 70 and wound in the longitudinal direction. The flat wound electrode body 20 is formed by, for example, laminating the positive electrode 50, the negative electrode 60, and the separator 70 and winding the wound body in one direction orthogonal to the winding axis (typically Can be formed by crushing (pressing) and abating from the side.

  Although not particularly limited, in the present embodiment, the positive electrode 50 has the positive electrode current collector 52 exposed without forming the positive electrode active material layer 54 along the edge on one side in the width direction of the positive electrode current collector 52. The exposed positive electrode current collector exposed end 53 is set. Similarly, in the negative electrode 60, the negative electrode current collector exposed end portion 63 where the negative electrode current collector 62 is exposed without forming the negative electrode active material layer 64 along the edge portion on one side in the width direction of the negative electrode current collector 62. Is set. As shown in FIG. 2, the wound electrode body 20 has the positive electrode current collector exposed end portion 53 and the negative electrode current collector exposed end portion 63 protruding outward from both ends in the winding axis direction. It may have been rolled over and rolled up. As a result, a wound core in which the positive electrode 50, the negative electrode 60, and the separator 70 are laminated and wound is formed at the center of the wound electrode body 20 in the winding axis direction. As shown in FIG. 2, the positive electrode current collector exposed end 53 and the positive electrode terminal 42 (for example, made of aluminum) are electrically connected via the positive electrode current collector plate 42 a, and the negative electrode current collector exposed end 63. And a negative electrode terminal 44 (for example, made of nickel) can be electrically connected via a negative electrode current collector plate 44a. The positive and negative electrode current collector plates 42a and 44a and the positive and negative electrode current collector exposed end portions 53 and 63 (typically the positive and negative electrode current collectors 52 and 62) are respectively formed by, for example, ultrasonic welding or resistance welding. Can be joined.

  In the embodiment disclosed herein, the wound electrode body 20 is configured so that a part of the outer surface of the wound electrode body 20 has the two Rs of the wound electrode body 20 as shown in FIGS. 3 and 4. It is covered with a heat-shrinkable annular member 80 disposed so as to face the outer surface of the portion 22 and the two flat surfaces 26. The annular member 80 is disposed around the wound electrode body 20 while being contracted by heat. That is, the heat-shrinkable annular member 80 covers a part of the outer surface of the wound electrode body 20 while being contracted in the direction from the outer surface of the wound electrode body 20 toward the winding axis WL. Are arranged as follows. As a result, the wound electrode body 20 is constrained (compressed) by the annular member 80 in the direction from the outer surface of the wound electrode body 20 toward the winding axis, resulting in unevenness in the distance between the electrodes. Is highly reduced.

The annular member 80 in a state before being contracted by heating is disposed at a predetermined position on the outer surface of the wound electrode body 20, and then the annular member 80 is heated so that the annular member 80 is contracted by heat. The annular member 80 can be disposed around the wound electrode body 20.
Means for heating the annular member 80 to a predetermined temperature (heat shrinkage temperature) is not particularly limited, and conventionally known heating means may be employed. For example, hot air (warm air) is applied to the annular member 80, a high-temperature heater such as a heated heating wire is brought close to the annular member 80, and electromagnetic waves such as infrared rays (far infrared rays) are irradiated to the annular member 80. Means are mentioned. From the viewpoint of efficiently heating the annular member 80, means for applying hot air (hot air) to the annular member 80 using a warm air machine is preferable.

In a preferred aspect, the annular member 80 is disposed so as to cover at least a part of the outer surface of the wound core formed at the center in the winding axis direction of the wound electrode body 20. More preferably, the anode active material layer 64 is preferably disposed so as to cover a portion where the portion not facing the cathode active material layer 54 (that is, the non-facing portion) is laminated. Thereby, it is possible to restrain (press) suitably the wound electrode body 20, and it can suppress suitably that the distance between electrodes becomes non-uniform | heterogenous. In the example shown in FIG. 3, the example in which the wound electrode body 20 is restrained by one member as the annular member 80 is shown, but the present invention is not limited to this, and the wound member is wound by two or more annular members 80. The electrode body 20 may be restrained. For example, both ends in the winding axis direction of the wound core of the wound electrode body 20 (preferably including the non-opposing portion of the negative electrode active material layer 64) may be constrained by the two annular members 80. For the purpose of making the distance between the electrodes substantially constant over the entire wound electrode body 20, the entire outer surface of the portion of the wound electrode body 20 where the negative electrode active material layer 64 is laminated is formed on the annular member. It is preferable to cover (restrain) with 80.
The annular member 80 does not interfere with the connection between the positive terminal 42 and the positive current collector exposed end 53 and the connection between the negative terminal 44 and the negative current collector exposed end 63 (more Preferably, the size does not cover the connection portion between the positive and negative electrode terminals and the exposed end of the positive and negative electrodes.

  The material of the annular member 80 is formed of a material having a property of contracting when heated to a predetermined temperature (heat shrinkage temperature) or higher. Typically, it may be formed of a known heat-shrinkable resin material. Further, the annular member 80 is preferably resistant to a solvent (typically an organic solvent) of a non-aqueous electrolyte, and a temperature at which the heat shrink temperature does not affect the separator 70 (typically, a separator). Preferably, the temperature is lower than the temperature at which 70 shuts down. Examples of such heat-shrinkable resin materials include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, polystyrene resins, polyvinyl chloride resins, and polyimide resins. Various materials are commercially available as these heat-shrinkable resin materials, and appropriate materials may be selected from these commercially available materials.

The annular member 80 has a plurality of holes other than the ring in which the wound electrode body 20 is inserted. Thereby, it is possible to suitably impregnate (penetrate) the non-aqueous electrolyte into the portion of the wound electrode body 20 covered with the annular member 80, and the annular member 80 can be By disposing around 20, it is possible to reduce the possibility that the impregnation property of the non-aqueous electrolyte into the wound electrode body is lowered.
The size of the hole formed in the annular member 80 can permeate the non-aqueous electrolyte in a thermally contracted state (that is, a state in which the hole is thermally contracted after being disposed on the outer periphery of the wound electrode body 20). Size is preferred. For example, it is preferable that an average diameter is 1 mm or more in the heat-shrinked state. On the other hand, if the number of holes formed in the annular member 80 is too large, the strength of the annular member 80 is lowered and easily broken. In addition, according to the annular member 80 in which a hole that is too large is formed, the effect of compressing (constraining) the wound electrode body 20 in the direction from the outer surface of the wound electrode body 20 toward the winding axis cannot be exhibited sufficiently. There is. Therefore, the average diameter of holes formed in the annular member 80 is in a state of being heat-shrinkable, (L _A in FIG. ₃₎ Kaijiku direction size wound of the wound electrode body 20, or the wound It is preferable to set it to 1/2 or less of the smaller one of the sizes connecting the vertices of the two R portions 22 of the electrode body 20 (L _{B in} FIG. 3).

In addition, the holes formed in the annular member 80 are heat-shrinked, and the sum of the opening areas of the holes formed in the annular member 80 (S _A ) is the area of the outer surface of the wound electrode body 20. In addition, it is preferable that the ratio is 10% or more and 50% or less with respect to the area (S _B ) of the portion covered by the heat-shrinked annular member 80. For example, the annular member in the heat-shrinked state with respect to the case where the area (S _B ) of the outer surface of the wound electrode body 20 covered with the annular member 80 in the thermally-shrinked state is 100%. The ratio of the total opening area (S _A ) of the holes formed in 80 can be 40%.
The total sum of the opening areas of the holes formed in the annular member 80 (S _B ) when the area (S _B ) of the outer surface of the wound electrode body 20 covered by the annular member 80 is 100% (S _If the ratio of _A ) is too small, the effect of improving the impregnation property (penetration) of the nonaqueous electrolytic solution into the wound electrode body 20 may not be sufficiently exhibited. A sum of the opening areas of the holes formed in the annular member 80 for the case where the area of the portion covered by the annular member 80 (S _B) is 100% of the outer surface of the wound electrode body 20 If the ratio of (S _A ) is too large, the wound electrode body 20 covered by the annular member 80 is compressed (restrained) by the annular member in the direction from the outer surface of the wound electrode body 20 toward the winding axis. ) May not be fully effective.

  In addition, the material and member itself which comprise the said electrode body (winding electrode body) 20 may be the same as that of the electrode body of the conventional lithium ion secondary battery, and there is no restriction | limiting in particular. A preferred embodiment of the wound electrode body 20 will be described below.

As the positive electrode current collector 52 constituting the positive electrode 50, for example, an aluminum foil or the like can be suitably used. Examples of the positive electrode active material include lithium composite metal oxides such as a layered structure and a spinel structure (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNiO ₂ , LiCoO ₂ , LiFeO ₂ , LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 O ₄ , LiFePO _4, etc.). Further, the positive electrode active material layer 54 can include components other than the active material, such as a conductive material and a binder. As the conductive material, carbon black such as acetylene black (AB) and other (such as graphite) carbon materials can be suitably used. As the binder, PVdF or the like can be used.

  As the negative electrode current collector 62 constituting the negative electrode 60, for example, a copper foil or the like can be suitably used. Examples of the negative electrode active material include a carbon material having a graphite structure (layered structure) at least partially, lithium transition metal nitride, and the like. Carbon materials such as so-called graphitic materials (graphite), non-graphitizable carbon materials (hard carbon), graphitizable carbon materials (soft carbon), and materials having a combination of these are preferably used. obtain. Moreover, the negative electrode active material layer 64 may contain components other than the active material, such as a binder and a thickener. As the binder, styrene butadiene rubber (SBR) or the like can be used. As the thickener, for example, carboxymethyl cellulose (CMC) can be used.

  Examples of the separator 70 include a porous sheet (film) made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Such a porous sheet may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer).

As the nonaqueous electrolytic solution, typically, a nonaqueous electrolytic solution containing a supporting salt in an organic solvent (nonaqueous solvent) can be used.
As the non-aqueous solvent, for example, one kind of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), etc. may be used alone or in two kinds. The above can be combined as appropriate (for example, a mixed solvent containing EC, EMC, and DMC at a volume ratio of 3: 4: 3). As the supporting salt, for example, a lithium salt (preferably LiPF ₆ ) such as LiPF ₆ , LiBF ₄ , or LiClO ₄ can be used. The concentration of the supporting salt is, for example, 0.7 mol / L or more and 1.3 mol / L or less (preferably about 1.1 mol / L).

  As described above, the non-aqueous electrolyte secondary battery disclosed herein provides a battery in which the deposition of a charge carrier-derived substance on the surface of the negative electrode active material layer is highly suppressed. Therefore, although the said battery can be utilized for various uses, it can use suitably as a drive power supply mounted in a vehicle, for example using such a property. The type of vehicle is not particularly limited, and examples include plug-in hybrid vehicles (PHV), hybrid vehicles (HV), electric vehicles (EV), electric trucks, motorbikes, electric assist bicycles, electric wheelchairs, electric railways, and the like. . Therefore, according to the present invention, there is provided a vehicle equipped with any of the nonaqueous electrolyte secondary batteries disclosed herein, preferably as a power source. The non-aqueous electrolyte secondary battery provided in the vehicle may be in the form of an assembled battery in which a plurality are connected.

  Several examples (test examples) relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the specific examples.

[Construction of lithium secondary battery]
The lithium secondary battery (nonaqueous electrolyte secondary battery) according to Examples 1 to 4 was constructed by the following materials and processes.

<Example 1>
LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (LNCM) as a positive electrode active material, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder are combined with LNCM: AB Was mixed with N-methylpyrrolidone (NMP) at a mass ratio of: PVdF = 94: 3: 3 to prepare a paste-like (slurry) positive electrode active material layer forming composition. This composition was applied in a strip shape on both sides of a long aluminum foil (positive electrode current collector) having an average thickness of 15 μm, dried and pressed to produce a positive electrode.

  Next, spheroidized graphite (C) as a negative electrode active material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener, C: SBR: CMC = 98: 1 The composition for forming a paste-like (slurry) negative electrode active material layer was prepared by dispersing in water at a mass ratio of 1: 1. The composition was applied in a strip shape on both sides of a long copper foil (negative electrode current collector) having an average thickness of 10 μm, dried and pressed to prepare a negative electrode.

The positive electrode and the negative electrode manufactured by the above-described method were overlapped in the longitudinal direction via two separators, wound in the longitudinal direction, and then crushed and ablated to produce a flat wound electrode body. Here, as the separator, a three-layer structure having an average thickness of 20 μm and a porous polypropylene layer formed on both sides of the porous polyethylene layer was used.
Next, the wound electrode body and the nonaqueous electrolytic solution were accommodated in a rectangular battery case (made of aluminum), and a lithium secondary battery according to Example 1 was constructed. As the non-aqueous electrolyte, a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) at a volume ratio of EC: DMC: EMC = 1: 1: 1, of LiPF ₆ as a supporting salt was used dissolved at a concentration of 1 mol / L. Moreover, the battery capacity of the lithium secondary battery according to Example 1 was 30 Ah.

<Example 2>
The above example except that a polypropylene ring member is prepared, and the flat wound electrode body is inserted into the ring of the ring member in the winding axis direction, and then the ring member is heated and contracted. A lithium secondary battery according to Example 2 was fabricated using the same material and process as in Example 1. That is, the annular member is disposed so that the inner side of the ring faces the outer surface and the flat surface of the R portion of the wound electrode body. Here, as the annular member, a member having no hole other than the ring into which the wound electrode body is inserted was used. The annular member was heated by applying hot air blown from a warm air machine.

<Example 3>
Example 1 except that a polypropylene ring member having a plurality of holes is prepared and the flat wound electrode body is inserted in the ring axis direction into the ring of the ring member. A lithium secondary battery according to Example 3 was manufactured using the same material and process. That is, the lithium secondary battery according to Example 3 did not heat the annular member after inserting the wound electrode body into the ring of the annular member. Here, the average diameter of the holes formed in the annular member is 2 mm, and the total opening area (S _A ) of the holes is the portion of the outer surface of the wound electrode body covered by the annular member. It is 40% with respect to the area (S _B ).

<Example 4>
A polypropylene ring member having a plurality of holes formed therein is prepared, and after the flat wound electrode body is inserted into the ring of the ring member in the winding axis direction, the ring member is heated. A lithium secondary battery according to Example 4 was manufactured using the same materials and processes as in Example 1 except that the lithium secondary battery was contracted. That is, the annular member is disposed so that the inner side of the ring faces the outer surface and the flat surface of the R portion of the wound electrode body. Here, the annular member is in a state after being contracted by heating, the average diameter of the holes is 2 mm, and the total opening area (S _A ) of the holes formed in the annular member is a wound electrode body. was 40% of the area of the portion covered by the annular member of the outer surface (S _B). The annular member was heated by applying hot air blown from a warm air machine.

[Li precipitation resistance evaluation test]
Under the temperature condition of 25 ° C., the lithium secondary batteries according to Examples 1 to 4 are subjected to constant current charging (CC charging) at a charging rate of 1 C up to the charging upper limit voltage (4.1 V), and the current value is Constant current constant voltage charging (CCCV charging) was performed in which constant voltage charging (CV charging) was performed until 1/10 C. Then, the batteries according to the respective examples after performing the CCCV charge are respectively disassembled, the negative electrode is taken out, and the presence or absence of deposition of a substance (here, metallic lithium) derived from the charge carrier on the negative electrode active material layer is visually observed. confirmed.
Here, five lithium secondary batteries according to each example were prepared, and the number of batteries in which the deposition of metallic lithium was confirmed in the Li deposition durability evaluation test was counted. Table 1 shows the number of generations of batteries in which the deposition of metallic lithium was confirmed with respect to the number of batteries used in the test (here, 5) for the batteries according to each example: “Li precipitation generation number (pieces) / test number ( Number)).

As shown in Table 1, the lithium secondary battery according to Example 4 had a lower frequency of batteries in which Li deposition was observed than the lithium secondary batteries according to Examples 1 to 3.
Here, the fact that the lithium secondary battery according to Example 4 was observed less frequently than Li secondary battery according to Example 3 covered a part of the outer surface of the wound electrode body. The annular member arranged in this manner is contracted by heating, whereby the wound electrode body is constrained (compressed) by the annular member in the direction from the outer surface toward the winding axis, and the width between the electrodes of the wound electrode body This is considered to be due to the fact that it was made almost uniform.
In addition, the lithium secondary battery according to Example 4 was observed to have a lower frequency of Li deposition compared to the lithium secondary battery according to Example 2 because the annular member was formed with a plurality of holes. This is considered to be because the nonaqueous electrolyte solution was suitably impregnated (penetrated) into the wound electrode body and the non-aqueous electrolyte solution unevenness that could occur in the wound electrode body was improved. Moreover, from the result of Example 4, the hole formed in the annular member corresponds to the case where the area (S _B ) of the portion covered by the annular member on the outer surface of the wound electrode body is 100%. It was confirmed that it is preferable to form the annular member so as to be 40% of the ratio of the total opening area (S _A ) of the holes formed in the annular member.
Thus, according to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery in which the deposition of a charge carrier-derived substance on the negative electrode active material layer is highly reduced.

  As mentioned above, although the specific example of this invention was demonstrated in detail, the said embodiment and Example are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

20 Winding electrode body 22 R part 24 Central flat part 26 Flat surface 30 Battery case 32 Battery case main body 34 Cover body 36 Safety valve 42 Positive electrode terminal 42a Positive electrode current collector plate 44 Negative electrode terminal 44a Negative electrode current collector plate 50 Positive electrode 52 Positive electrode current collector 53 Positive electrode current collector exposed end 54 Positive electrode active material layer 60 Negative electrode 62 Negative electrode current collector 63 Negative electrode current collector exposed end 64 Negative electrode active material layer 70 Separator 80 Ring member 100 Secondary battery (lithium secondary battery)
WL winding axis

Claims (1)

A non-aqueous electrolyte secondary battery comprising a flat wound electrode body, a non-aqueous electrolyte, and a battery case containing the electrode body and the non-aqueous electrolyte,
The wound electrode body is sandwiched between two R portions, which are both ends in a direction orthogonal to the winding axis, and whose outer surface excluding the laminated surface of the wound electrode body is a curved surface. And a central flat portion having two broad flat surfaces,
The wound electrode body has a heat-shrinkable structure in which a part of the outer surface of the wound electrode body is arranged so as to face the outer surface of the two R parts and the two flat surfaces of the central flat part. Covered by an annular member,
The annular member is arranged around the wound electrode body in a contracted state by heat,
The annular member has a plurality of holes formed in a thermally contracted state, and the area of the outer surface of the wound electrode body covered with the annular member in the thermally contracted state ( _A non-aqueous electrolyte secondary battery in which the ratio of the sum of the opening areas of the holes formed in the thermally contracted annular member (S _A ) is 40% with respect to the case where S _B ) is 100%.

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