JP2014029823A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery capable of suppressing melting of a separator even when a laser beam intrudes into a battery case during welding.SOLUTION: The secondary battery includes a reflection member 60 between a boundary of a battery case 10 and a sealing body 20 and a positive electrode mixture layer 42 or a negative electrode mixture layer 32 of a wound body 2. Where transmittance of the reflection member 60 and a separator 50 at the same wavelength of visible light are denoted as transmittance A and transmittance B, respectively, a relational expression (a): A×B<20% is satisfied.

Description

  The present invention relates to a secondary battery in which an electrode body is accommodated in a battery case made of a metal material.

  The importance of a secondary battery is increasing as a power source mounted on a vehicle using electricity as a driving source, or a power source used for a personal computer, a portable terminal, or other electrical products. In particular, a lithium ion secondary battery that is lightweight and obtains a high energy density is preferable as a high-output power source mounted on a vehicle.

  In such a lithium ion secondary battery, a wound body that is wound with a separator interposed between the positive electrode and the negative electrode in order to prevent a short circuit between the two electrodes is accommodated in the battery case. As such a separator, a sheet made of polypropylene (PP), polyethylene (PE) or the like is used.

The separator made of PP or PE has a function of shutting down the lithium ion secondary battery by melting the separator when the melting temperature of the separator material is reached. However, when heat generated in the process of manufacturing a lithium ion secondary battery is transmitted to the separator, the separator is melted, which may adversely affect battery performance.
Therefore, it has been studied to provide a heat-resistant protective member on the outer periphery of the winding body to prevent the separator from being melted by the heat of the battery case when the sealing body is laser welded to the battery case (for example, Patent Documents). 1).

  In addition, it has been studied to prevent melting of the separator by welding an uncoated portion of the electrode mixture of the electrode and the current collecting disk through a foil or a plate (for example, Patent Document 2).

JP 2008-171583 A JP 2009-123440 A

  However, in the lithium ion secondary battery disclosed in Patent Document 1, when laser light enters the battery case from the gap between the battery case and the sealing body during laser welding, the laser light passes through the separator. The electrode mixture layer in the wound body is irradiated. When the electrode mixture layer has a carbon-based material, the electrode mixture layer may absorb the laser beam and generate heat, thereby melting the separator.

  Moreover, in the lithium ion secondary battery disclosed in Patent Document 2, the battery case has an opening on the end side in the axial direction of the wound body. Therefore, it cannot respond when there is an opening of the battery case on the bent part side of the wound body.

The invention according to claim 1 is an electrode body in which a positive electrode having a positive electrode composite material layer and a negative electrode having a negative electrode composite material layer are laminated via a separator, accommodates the electrode body, and has an opening. In a secondary battery having a battery case and a sealing body that is welded to the battery case and seals the battery case, at least one of the positive electrode mixture layer and the negative electrode mixture layer has carbon-based particles, A reflective member between the boundary between the sealing body and the battery case, and the positive electrode mixture layer or the negative electrode mixture layer having the carbon-based particles among the positive electrode mixture layer and the negative electrode mixture layer. Have
A secondary battery that satisfies the relational expression (a): A × B <20 (%) when the transmittance of the reflective member and the separator with respect to the same wavelength of visible light is transmittance A and transmittance B, respectively. is there.

  According to the first aspect of the present invention, even when the laser beam enters the battery case when the sealing body is welded to the battery case, a value obtained by multiplying the transmittance A of the reflecting member and the transmittance B of the separator is obtained. In addition, since it is a value that suppresses irradiation of the laser beam to the positive electrode mixture layer or the negative electrode mixture layer, the positive electrode mixture layer or the negative electrode mixture layer does not generate heat. Therefore, since the positive electrode mixture layer or the negative electrode mixture layer does not apply heat to the separator, melting of the separator by laser light can be suppressed.

  The invention according to claim 2 is a wound body having a flat portion and a bent portion, wherein the positive electrode and the negative electrode are wound and flattened via the separator. In the wound body, the outermost peripheral surface of the flat portion is along the inner wall of the battery case, and one of the bent portions faces the opening side of the battery case, and the other bent portion is the battery case. The bent portion arranged toward the bottom surface and arranged toward the opening side of the battery case has the separator in the outermost layer, and the reflecting member is a sheet-like member, The said positive electrode compound material layer of the said bending part, or the said negative electrode compound material layer of the said bending part is covered along the axial direction of the said winding body, and the circumferential direction of the said winding body. It is a secondary battery.

  According to invention of Claim 2, even when an electrode body is arrange | positioned so that the shielding range which should shield a laser beam becomes wide, irradiation of the laser beam to a positive mix layer or a negative mix layer is prevented. Can do. Even when the laser beam enters the battery case when the sealing body is welded to the battery case, the reflecting member reflects most of the laser beam, so that the positive electrode mixture layer or the negative electrode composite of the laser beam is more effectively reflected. Irradiation to the material layer can be suppressed. Therefore, melting of the separator can be suppressed.

  According to a third aspect of the present invention, the reflecting member is disposed closer to the sealing body than the two flat portions, and both ends of the reflecting member along the circumferential direction of the winding body are located on the opening side of the battery case. The secondary battery according to claim 2, wherein the secondary battery faces the inner wall of the battery case.

  According to the invention described in claim 3, since the reflecting member is not provided at the end of the bent portion of the wound body, the reflecting member does not enter between the battery case and the wound body. Therefore, the reflecting member can reflect the irradiation of the laser beam to the positive electrode mixture layer or the negative electrode mixture layer without affecting the surface pressure from the battery case to the wound body. Therefore, melting of the separator can be suppressed while maintaining battery performance.

  Invention of Claim 4 has an insulating film which insulates the said winding body and the said battery case, The said insulating film is a secondary battery of Claim 2 which is the said reflection member.

  According to the invention of claim 4, the insulating film can be used as a reflecting member, and the separator can be prevented from melting with a simple configuration.

  According to a fifth aspect of the present invention, the reflecting member has an adhesive layer, and the adhesive layer is adhered to the bent portion disposed on the opening side of the wound body, and the wound body The secondary battery according to any one of claims 2 to 3, wherein

  According to the fifth aspect of the invention, the winding tape of the wound body obtained by winding the electrode body can function as the reflecting member. Therefore, melting of the separator can be suppressed when the sealing body is welded to the battery case without providing a new member.

  According to the present invention, it is possible to provide a secondary battery that can suppress melting of the separator even if laser light enters the battery case during welding.

It is a figure explaining the lithium ion secondary battery which concerns on the 1st Embodiment of this invention. It is the figure of the content which looked at FIG. 1 from I direction. It is a schematic diagram of the AA arrow cross section of FIG. It is a perspective view of the winding body which concerns on this invention. It is a figure which shows the cross section of the winding body accommodated in the battery case in detail. It is sectional drawing of the lithium ion secondary battery which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the lithium ion secondary battery which concerns on the 3rd Embodiment of this invention. It is sectional drawing of the lithium ion secondary battery which concerns on a comparative example.

  Next, embodiments will be described with reference to the drawings.

First Embodiment FIG. 1 is a perspective view schematically showing a lithium ion secondary battery 1 according to an embodiment of the present invention. FIG. 2 is a view of the inside of the battery case 10 as viewed from the I direction in FIG. Further, FIG. 3 is a schematic diagram of a cross section taken along the line AA of FIG. 2 and shows a state where the wound body 2 is accommodated in the battery case 10. 4 is a perspective view of the wound body 2, and FIG. 5 is a view showing in detail a cross section of the wound body 2 accommodated in the battery case.

The lithium ion secondary battery 1 according to the first embodiment is a large lithium ion secondary battery having a battery capacity of 3 A / h. As shown in FIG. 1, the lithium ion secondary battery 1 includes a battery case 10 and a sealing body 20. The battery case 10 and the sealing body 20 are made of metal.
The battery case 10 has an upper end opened. And the said opening part of the battery case 10 is block | closed with the sealing body 20, and the sealing body 2 and the battery case 10 are welded.
The sealing body 20 is provided with a positive terminal 70a and a negative terminal 70b. The positive electrode terminal 70 a is electrically connected to the long sheet-like positive electrode 40 of the wound body 2. The negative terminal 70 b is electrically connected to the long sheet-like negative electrode 30 of the wound body 2.
Moreover, the sealing body 20 is provided with a safety valve 21 as in the case of a conventional lithium ion secondary battery. The safety valve 21 discharges the gas generated inside when the battery is abnormal to the outside of the battery case 10.

As shown in FIG. 2, the wound body 2 and the non-aqueous electrolyte are accommodated inside the battery case 10. The wound body 2 is an electrode body in which a sheet-like positive electrode 40 and a sheet-like negative electrode 30 are laminated via a separator 50. The wound body 2 has a shape in which the electrode body is wound into a flat shape. Specifically, the flat wound body 2 may be manufactured by winding the electrode body and crushing from the side surface direction.
The sheet-like positive electrode 40 has a positive electrode mixture layer 42 formed by applying and drying a paste obtained by dissolving at least a positive electrode active material, a conductive material, and a binder in a solvent on both surfaces of a positive electrode foil 41. Moreover, the said paste is not apply | coated to the edge part of the horizontal direction with respect to the winding direction of the sheet-like positive electrode 40. FIG. In the wound body 2, the positive foil 41 is exposed so as to protrude outward in the lateral direction with respect to the winding direction.
Further, the sheet-like negative electrode 30 has a negative electrode mixture layer 32 formed by applying and drying a paste prepared by dissolving at least a negative electrode active material, a conductive material, and a binder in a solvent on both surfaces of the negative electrode foil 31. Moreover, the said paste is not apply | coated to the edge part of the horizontal direction with respect to the winding direction of the sheet-like negative electrode 30. FIG. And in the winding body 2, the negative electrode foil 31 is exposed so that it may protrude toward the outer side of the horizontal direction with respect to the winding direction.
And the said exposed part of the positive electrode foil 41 and the positive electrode terminal 70a are joined, and the positive electrode 40 and the positive electrode terminal 70a of the winding body 2 are electrically connected. Similarly, the exposed part of the negative electrode foil 31 and the negative electrode terminal 70b are joined, and the negative electrode 30 and the negative electrode terminal 70b of the wound body 2 are electrically connected.
Here, on the upper part of the wound body 2 (opening side of the battery case 10), a sheet-like reflecting member 60 having an adhesive layer on the lower surface (the surface on the side of the wound body 2) is disposed in an adhesive manner. . Further, when the transmittance of the reflective member 60 and the separator 50 with respect to the same wavelength of visible light is set to the transmittance A and the transmittance B, respectively, if the relational expression (a): A × B <20 (%) is satisfied Good. More preferably, the relational expression (b): A × B <16 (%) may be satisfied.

  Further, as shown in FIG. 3, the wound body 2 has a wound end portion at a bent portion 2 a on the upper portion of the wound body 2 (opening side of the battery case 10). And the reflection member 60 is adhere | attached so that the negative mix layer 32 of the bending part 2a of the upper part (opening part side of the battery case 10) of the winding body 2 may be covered. Therefore, the reflecting member 60 stops the wound body 2.

  Here, in the wound body 2, the exposed positive electrode foil 41 of the positive electrode 40 and the exposed negative electrode foil 31 of the negative electrode 30 protrude from both sides of the separator 50 in the width direction (lateral direction with respect to the winding direction). Further, the positive electrode 40 and the negative electrode 30 are superposed with a slight shift in the width direction. And the electrode body is formed by laminating | stacking the positive electrode 40 and the negative electrode 30 through the separator 50. FIG. Further, the wound body 2 is formed by winding the electrode body into a flat shape. In the wound body 2 formed in this way, as shown in FIG. 4, the positive electrode mixture layer 42, the negative electrode mixture layer 32, and the separator 50 are positively wound outward from the portion where the positive electrode mixture layer 42, the negative electrode mixture layer 32, and the separator 50 are wound tightly. The configuration is such that the foil 41 and the negative electrode foil 31 protrude.

FIG. 5 shows the winding body 2 housed in the battery case 10 in detail. As shown in FIG. 5, a positive electrode 40 and a negative electrode 30 are laminated via a separator 50 to form an electrode body, and the electrode body is wound into a flat shape to form a wound body 2. The positive electrode 40 has a positive electrode mixture layer 42 on both surfaces of a sheet-like positive electrode foil 41. The negative electrode 30 has a negative electrode mixture layer 32 on both surfaces of a sheet-like negative electrode foil 31.
The wound body 2 has a bent portion 2a and a flat portion 2b. Further, the outermost periphery of the flat portion 2 b is along the inner wall 11 of the battery case 10. One of the bent portions 2 a faces the opening of the battery case 10, and the other bent portion 2 a faces the bottom surface of the battery case 10.

According to the lithium ion secondary battery 1 according to the first embodiment of the present invention, the positive electrode mixture layer 42 or the negative electrode is provided even when the electrode body is arranged so that the shielding range in which the laser beam should be shielded is widened. Irradiation of the laser beam to the composite material layer 32 can be prevented. Even when the laser beam enters the battery case 10 when the sealing body 20 is welded to the battery case 10, the laser beam is reflected by the reflecting member 60, so that the positive electrode mixture layer 42 or the negative electrode composite of the laser beam is reflected. Irradiation to the material layer 32 is suppressed, and melting of the separator 50 by laser light can be suppressed.
Further, the winding tape of the wound body 2 obtained by winding the electrode body can be functioned as the reflecting member 60. Therefore, melting of the separator 50 when the sealing body 20 is welded to the battery case 10 can be suppressed without providing a new member.

  More specifically, a value obtained by multiplying the transmittance A of the reflecting member 60 and the transmittance B of the separator 50 is a value that suppresses irradiation of the positive electrode mixture layer 42 or the negative electrode mixture layer 32 with laser light. Yes. Therefore, the positive electrode mixture layer 42 or the negative electrode mixture layer 32 does not generate heat. Therefore, since the positive electrode mixture layer 42 or the negative electrode mixture layer 32 does not apply heat to the separator 50, melting of the separator 50 due to laser light can be suppressed.

5 shows an example in which the end of the separator 50 extends to the bent portion 2a on the opening side of the battery case 10, but the position of the end of the separator 50 is the position shown in FIG. It is not limited to.
Further, when the reflecting member 60 is not used as a squeeze stopper, the reflecting member 60 and the end portion of the separator 50 may not be continuous. In other words, the reflecting member 60 and the end of the separator 50 do not have to be in contact with each other. When the reflection member 60 and the end portion of the separator 50 do not have to be continuous, the end portion of the separator 50 can be in a free position based on various factors. For example, when it is desired to position the end of the separator 50 on the bottom side of the battery case 10, it is not necessary to unnecessarily extend the reflecting member 60.
Further, the reflection member 60 is formed of a material different from that of the separator 50. Thereby, the separator 50 can be formed from a material optimal for the function required for the separator 50, and the reflecting member 60 can be formed from a material optimal for the reflecting function of the reflecting member 60.
In addition, a plurality of separators 50 may be provided between the positive electrode 40 and the negative electrode 30. Similarly, a plurality of overlapping reflecting members 60 may be provided on the opening side of the battery case 10 of the wound body 2. In this case, the transmittance of the reflecting member 60 that overlaps a plurality of sheets is set as the transmittance A, and the transmittance of the separator 50 that overlaps a plurality of sheets is set as the transmittance B, and the relational expression (a) or (b) may be satisfied.

Second Embodiment As shown in FIG. 6, a lithium ion secondary battery 100 according to a second embodiment of the present invention is similar to the lithium ion secondary battery 1 according to the first embodiment. This is a lithium ion secondary battery in which an electrode pair is accommodated in the battery case 10. The electrode body according to the second embodiment is the same wound body 2 as that of the first embodiment, and only the reflection member 61 is different from that of the first embodiment. The same reference numerals are given and the description thereof is omitted.
The reflection member 61 is disposed between the sealing body 20 and the bent portion 2a. Both ends of the reflecting member 61 along the circumferential direction of the wound body 2 face the opening side of the battery case 10 and are in contact with the inner wall 11 of the battery case 10.

  According to the lithium ion secondary battery 100 according to the second embodiment, the reflecting member 60 is not provided at the end of the bent portion 2a of the wound body 2, and therefore, between the battery case 10 and the wound body 2. The reflection member 60 does not enter. Therefore, the surface of the wound body 2 that contacts the battery case 10 is a flat surface, and the pressure from the battery case 10 does not change partially. That is, the surface pressure from the battery case 10 applied to the wound body 2 can be made constant. Therefore, the melting of the separator 50 at the time of welding the battery case 10 and the sealing body 20 can be more reliably suppressed without adversely affecting battery farming by changing part of the surface pressure.

Third Embodiment A lithium ion secondary battery 200 according to a third embodiment has an insulating film 62 as shown in FIG. 7, and the only difference is that the insulating film 62 is a reflecting member. This is different from the lithium ion secondary battery 1 according to the first embodiment. For this reason, the same components are denoted by the same reference numerals and description thereof is omitted.

The insulating film 62 covers the entire circumference of the wound body 2. Thereby, the insulating film 62 insulates the wound body 2 and the battery case 10. More specifically, the insulating film 62 is a sheet-like member made of an insulating material. Then, the insulating film 62 is inserted into the battery case 10 along the inner wall 11. At this time, the end portion of the insulating film 62 faces the opening side of the battery case 10. Next, the wound body 2 is inserted inside the insulating film 62. In other words, the insulating film 62 is inserted between the wound body 2 and the battery case 10. And the edge parts by the side of the opening part of the insulating film 62 are heat-welded. Thereby, the insulating film 62 covers the entire circumference of the wound body 2.
And at least the surface of the insulating film 62 on the battery case 10 side is a reflective surface. Thereby, the insulating film 62 functions as a reflecting member.

  According to the lithium ion secondary battery 200 according to the third embodiment, the insulating film 62 can be used as a reflecting member, and the melting of the separator 50 can be suppressed with a simple configuration.

  Here, the positive electrode 40 of the lithium ion secondary battery 1, 100, 200 according to the above embodiment of the present invention will be described. The positive electrode 40 according to the above embodiment of the present invention is a positive electrode mixture layer formed by applying a paste prepared by dissolving at least a positive electrode active material, a conductive material, and a binder in a solvent on both surfaces of the positive electrode foil 41 and drying the paste. 42.

The positive electrode active material used in the positive electrode 40 according to the above embodiment is a material capable of inserting and extracting lithium ions. Specifically, the positive electrode active material includes a lithium-containing compound (for example, a lithium transition metal composite oxide) containing a lithium element and one or more transition metal elements. For example, lithium nickel composite oxide (eg, LiNiO ₂ ), lithium cobalt composite oxide (eg, LiCoO ₂ ), lithium manganese composite oxide (eg, LiMnO ₄ ), or lithium nickel cobalt manganese composite oxide (eg, LiNi _1/3). And ternary lithium-containing composite oxides such as Co _1/3 Mn _1/3 O ₂ ). In addition, a polyanionic compound (for example, LiFePO 4) represented by a general formula of LiMPO ₄ , LiMVO _4, or Li ₂ MSiO ₄ (wherein M is at least one element of Co, Ni, Mn, and Fe) ₄ , LiMnPO ₄ , LiFeVO ₄ , LiMnVO ₄ , Li ₂ FeSiO ₄ , Li ₂ MnSiO ₄ , Li ₂ CoSiO ₄ ) may be used as the positive electrode active material.

  The conductive material is not limited to a specific conductive material as long as it is conventionally used in this type of lithium ion secondary battery. For example, carbon materials such as carbon powder and carbon fiber can be used. As the carbon powder, various carbon blacks (for example, acetylene black, furnace black, ketjen black, etc.), graphite powder, and the like can be used. Among these, you may use together 1 type, or 2 or more types.

  Moreover, as the binder, those similar to the binder used for the positive electrode of a general lithium ion secondary battery can be appropriately employed. When the composition is prepared using an aqueous solvent, a water-soluble (dissolvable in water) or water-dispersible (dispersible in water) aqueous polymer is preferable. Examples of the water dispersible polymer include rubbers such as styrene butadiene rubber (SBR); polyethylene oxide (PEO); vinyl oxide copolymer; Moreover, when adjusting a composition using a solvent-type solvent, the polymer material which melt | dissolves in organic solvents (nonaqueous solvent), such as a polyvinylidene fluoride (PVDF) and a polyvinylidene chloride (PVDC), can be used. . Examples of the solvent-based solvent include N-methylpyrrolidone (NMP).

  As the positive electrode foil 41, an aluminum material or an alloy material mainly composed of an aluminum material can be used as in the positive electrode foil used for the positive electrode of a conventional lithium ion secondary battery.

  Next, the negative electrode 30 according to the above embodiment will be described. The negative electrode 30 according to the present embodiment is a member having a negative electrode mixture layer 32 formed by applying a paste obtained by dissolving at least a negative electrode active material and a binder in a solvent to both surfaces of the negative electrode foil 31 and drying the paste. .

As said negative electrode active material, the material of 1 type, or 2 or more types conventionally used for a lithium ion secondary battery can be used without limitation. For example, particulate carbon material including a graphite structure (layered structure) at least partially, lithium transition metal composite oxide (for example, lithium titanium composite oxide such as Li ₄ Ti ₅ O ₁₂ ), lithium transition metal composite nitride Etc. Examples of the carbon material include natural graphite, artificial graphite (artificial graphite), non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), and the like.

  As a binder contained in the said negative electrode compound material, the thing similar to the binder used for the negative electrode of a general lithium ion secondary battery can be employ | adopted suitably. For example, when a water-based paste-like composition is used to form the negative electrode mixture layer 32, the adhesive used in the positive electrode 40 can be appropriately employed as an adhesive contained in the negative electrode mixture. .

  The negative electrode mixture layer 32 may contain a thickener. As the thickener contained in the negative electrode mixture layer 32, for example, a water-soluble or water-dispersible polymer can be employed. Examples of the water-soluble polymer include cellulose polymers such as carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), and hydroxypropylmethylcellulose (HPMC); polyvinyl alcohol (PVA); . In addition, the same materials as those mentioned as the binder can be appropriately used as the thickener contained in the negative electrode mixture layer 32.

  As the negative electrode foil 31, a copper material or an alloy material mainly composed of a copper material can be used as in the negative electrode foil used in the negative electrode of a conventional lithium ion secondary battery.

  Next, the non-aqueous electrolyte of the lithium ion secondary battery according to the above embodiment will be described. The non-aqueous electrolyte is injected into the battery case 10 from a non-aqueous electrolyte inlet (not shown) after welding the battery case 10 and the sealing body 20.

  Here, at least one of the positive electrode mixture and the negative electrode mixture includes carbon-based particles, and an electrode including the carbon-based particles is disposed outside the wound body 2. Good configuration.

As said non-aqueous electrolyte, the thing similar to the non-aqueous electrolyte conventionally used for a lithium ion secondary battery can be used without specifically limiting. Such a non-aqueous electrolyte typically has a composition in which a supporting salt is contained in an appropriate organic solvent (non-aqueous solvent). As the organic solvent, for example, one or more selected from ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and the like can be used. Further, as the supporting salt, for _{example, LiPF 6, LiBF 4, LiAsF} 6, Li (CF 3 SO 2) 2N, it is preferable to use a lithium salt containing as a constituent element fluorine (F), such as LiCF ₃ SO ₃ . Further, difluorophosphate (LiPO ₂ F ₂ ) or lithium bisoxalate borate (LiBOB) may be dissolved in the non-aqueous electrolyte.

  Next, the separator 50 of the lithium ion secondary battery according to the above embodiment will be described. The separator 50 is a member disposed between the positive electrode 40 and the negative electrode 30.

  As said separator 50, the conventionally well-known thing used for a lithium ion secondary battery can be especially used without a restriction | limiting. For example, polyethylene (PE) type, polypropylene (PP) type, etc. can be used.

  Next, the reflecting member 60 of the lithium ion secondary battery according to the above embodiment will be described. The reflective member 60 is a member that has an adhesive layer on one surface and can wind the wound body 2 by sticking the reflective member 60 to the wound body 2.

As the reflective member 60, a polypropylene (PP) -based or polyethylene (PE) -based material can be used as a base material.
Moreover, when t with respect to the same wavelength of visible light of the reflection member 60 and the separator 50 is set to the transmittance A and the transmittance B, respectively, it is preferable that the relational expression (a): A × B <20 (%) is satisfied. Furthermore, it is preferable that the relational expression (b): A × B <16 (%) is satisfied. Here, the transmittance | permeability with respect to visible light can be adjusted with the color and brightness of a member based on the following Table 1 and Table 2 (refer JISZ8721-1993). Specifically, transmittance (%) = 100−reflectance can be calculated.

As the adhesive layer, the same adhesive layer as that of a tape used for scratching a general lithium ion secondary battery can be appropriately employed. For example, an acrylic adhesive layer can be used.
Further, the reflection member 61 and the insulating film 62 may be the same as the reflection member 60. In addition, the reflective member 61 and the insulating film 62 do not need to have the adhesion layer.

  Hereinafter, examples according to the first embodiment will be described in Example 1, examples according to the second embodiment will be described in Example 2, and comparative examples will be described in Examples 3 and 4. It is not intended to be limited to the examples.

(Example 1)
LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as a positive electrode active material, acetylene black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder are dispersed in NMP to form a positive electrode composite. A paste for forming a material layer was obtained. The positive electrode composite material layer forming paste was applied to both surfaces of the positive electrode foil 41 (aluminum foil) and dried, and then subjected to a rolling treatment to produce the positive electrode 40.
Natural graphite as a negative electrode active material, SBR as a binder, and CMC as a thickener were dispersed in water to obtain a negative electrode mixture layer forming paste. The negative electrode composite material layer forming paste was applied to both surfaces of the negative electrode foil 31 (copper foil) and dried, and then subjected to a rolling treatment to produce the negative electrode 30.
The non-aqueous electrolyte was prepared by dissolving LiPF _{6 in} a mixed solvent of EC, MEC, and DMV.
The separator 50 is made of PE as a base material and has a reflectivity with respect to visible light of about 46%. That is, the transmittance B of the separator 50 is 54%.
The reflective member 60 has an acrylic adhesive layer and white adhesive tape No. 1 manufactured by Nitto Denko Corporation using PE as a base material. 31C was used. That is, the reflectance of the reflecting member 60 is 70%. In other words, the transmittance A of the reflecting member 60 is 30%. Therefore, in Example 1, A × B≈16 (%).
And the said positive electrode 40 and the said negative electrode 30 were laminated | stacked through the said separator 50, and the electrode body was formed. Next, the electrode body was wound into a flat shape to produce a wound body 2 (see FIG. 5).
Here, the separator 50 is disposed on the outermost periphery of the wound body 2, and the negative electrode 30 is disposed on the layer immediately below the separator 50. In addition, the wound body 2 was wound so that the wound end portion is disposed in the bent portion 2 a above the wound body 2. Moreover, the reflecting member 60 was adhered so that the front surface of the negative electrode mixture layer 32 above the wound body 2 was covered with the reflecting member 60, and the wound body 2 was stopped. And while connecting positive electrode terminal 70a and positive electrode foil 41 of winding body 2 electrically, negative electrode terminal 70b and negative electrode foil 31 of winding body 2 were connected electrically. Further, the wound body 2 and the non-aqueous electrolyte were accommodated in the battery case 10 and assembled so that the sealing body 20 was fitted into the battery case 10. Thereafter, the battery case 10 and the sealing body 20 were welded using a fiber laser having an output of 2.4 kw to obtain the lithium ion secondary battery 1 according to Example 1.

(Example 2)
The lithium ion secondary battery 100 according to Example 2 was manufactured in the same manner as Example 1. Specifically, in the lithium ion secondary battery 100 according to Example 2, the reflecting member 61 having a shape in which the circumferential length of the wound body 2 is longer than the bent portion 2a is adhered to the bent portion 2a. . Here, the winding body 2 is connected to the battery case 10 so that both ends of the reflecting member 61 in the circumferential direction of the winding body 2 are not in contact with the winding body 2 and are in contact with the inner wall 11 of the battery case 10. Stored inside.

(Example 3)
The lithium ion secondary battery 1 according to Example 3 was manufactured in the same manner as Example 1. Specifically, the lithium ion secondary battery 1 according to Example 3 has the same shape as that shown in FIG. 3, and the reflective member 60 is a PP adhesive tape No. 1 manufactured by Nitto Denko Corporation. 3703DF light green was used. That is, the reflectance of the reflecting member 60 is 30%. In other words, the transmittance A of the reflecting member 60 is 70%. Therefore, in Example 3, A × B≈37 (%).

(Example 4)
As shown in FIG. 7, the lithium ion secondary battery 300 according to Example 4 does not have a reflective member between the bent portion of the wound body 2 and the sealing body 20. Therefore, since the lithium ion secondary battery 300 according to Example 4 is the same as the lithium ion secondary battery 1 according to Example 1 except that it does not have a reflecting member, the same components are denoted by the same reference numerals. The description is omitted.

  Here, after producing the lithium ion secondary batteries 1, 100, 300 according to Examples 1 to 4, the lithium ion secondary batteries 1, 100, 300 were disassembled, and the influence on the separator 50 by laser welding was visually observed. Confirmed and compared. As a result, in Example 1 and Example 2, the separator 50 was not melted. However, in Example 3, the separator 50 was melted. In Example 4, the separator 50 was slightly melted.

  In Examples 1 and 2, white members, that is, the reflecting members 60 and 61 having a reflectance of 70% or more were used as the reflecting member. In other words, a value obtained by multiplying the transmittance A of the reflecting member and the transmittance B of the separator is a value that suppresses the irradiation of the laser beam to the positive electrode mixture layer or the negative electrode mixture layer. Therefore, the laser light that has entered the battery case 10 during welding is reflected by the reflecting members 60 and 61, and the irradiation of the laser light on the negative electrode mixture layer 32 of the wound body 2 can be suppressed. Thereby, the heat_generation | fever of the negative mix layer 32 can be suppressed, and it is thought that the separator 50 was not melted.

  In Example 3, part of the laser light that enters the battery case 10 during welding is reflected by the reflecting member 60. However, part of the laser light that has entered the battery case 10 during welding is transmitted through or absorbed by the reflecting member 60 and the outermost separator 50, and the reflecting member 60 generates heat. This is probably because the lithium ion secondary battery 1 according to Example 3 uses the reflecting member 60 having a lower reflectance than those of Examples 1 and 2. Therefore, the amount of laser light reflected by the reflecting member 60 is small, the amount of laser light absorbed by the negative electrode mixture layer 32 or the reflecting member 60 is increased, and the negative electrode mixture layer 32 and the reflecting member 60 generate heat. Thereby, it is considered that a part of the separators 50 is melted.

  In Example 4, it is considered that the laser light entering the battery case 10 during welding was transmitted through the separator 50 of the wound body 2 and irradiated to the negative electrode mixture layer 32 under the separator 50. Therefore, it is considered that the negative electrode mixture layer 32 generates heat and the separator 50 is melted.

  Although not shown in the drawings, as another embodiment of the present invention, the electrode body is formed by laminating a positive electrode and a negative electrode toward the opening of the battery case via a separator, and the reflecting member is disposed on the opening side of the electrode body. Examples include a secondary battery that covers the outermost layer and is adhered to the electrode body.

  Further, as another embodiment of the present invention, an electrode body or a wound body in which a positive electrode and a negative electrode are laminated to face an inner wall of a battery case via a separator is accommodated in the battery case. Examples thereof include a secondary battery in which the end of the electrode body on the opening side or the end of the wound body is covered and a reflective member is adhered.

  In the embodiments of the present invention and other embodiments, the reflecting member is a sheet member adhered to the electrode body or the wound body, but the reflecting member is attached to the battery case and covers the electrode body or the wound body. Alternatively, the battery case may be arranged from the battery case to the sealing body so as to close the boundary between the battery case and the sealing body.

  The present invention is not limited to the lithium ion secondary battery described in the embodiment. Further, in the embodiments and examples of the invention, the negative electrode 30 has been described as being configured at the lower part of the separator 50 disposed at the outermost periphery, but the present invention is not limited to such a configuration, and carbon The electrode which has the electrode compound-material layer containing system particle | grains should just be arrange | positioned under the separator 50 of the outermost periphery.

1, 100, 200 Lithium ion secondary battery 2 Winding body (electrode body)
2a Bent part 2b Flat part 10 Battery case 11 Inner wall 20 Sealing body 30 Negative electrode 31 Negative electrode foil 32 Negative electrode composite material layer 40 Positive electrode 41 Positive electrode foil 42 Positive electrode composite material layer 50 Separator 60, 61, 62 Reflective member 70a Positive electrode terminal 70b Negative electrode terminal

Claims (5)

An electrode body in which a positive electrode having a positive electrode mixture layer and a negative electrode having a negative electrode mixture layer are laminated via a separator;
A battery case containing the electrode body and having an opening;
In a secondary battery having a sealing body that is welded to the battery case and seals the battery case,
At least one of the positive electrode mixture layer and the negative electrode mixture layer has carbon-based particles,
A reflective member between the boundary between the sealing body and the battery case, and the positive electrode mixture layer or the negative electrode mixture layer having the carbon-based particles among the positive electrode mixture layer and the negative electrode mixture layer. Have
A secondary battery satisfying the relational expression (a): A × B <20 (%) when the transmittance of the reflective member and the separator with respect to the same wavelength of visible light is defined as transmittance A and transmittance B, respectively. The electrode body is a wound body having a flat portion and a bent portion, in which the positive electrode and the negative electrode are wound and flattened via the separator,
In the wound body, the outermost peripheral surface of the flat portion is along the inner wall of the battery case, and one of the bent portions faces the opening side of the battery case, and the other bent portion is the battery case. It is arranged toward the bottom,
The bent portion arranged toward the opening side of the battery case has the separator in the outermost layer,
The reflecting member is a sheet-like member, and at least the positive electrode mixture layer of the bent portion or the negative electrode mixture layer of the bent portion includes an axial direction of the wound body and a circumferential direction of the wound body. The secondary battery according to claim 1, wherein the secondary battery is covered along the line. The reflective member is disposed closer to the sealing body than the two flat portions,
3. The secondary battery according to claim 2, wherein both ends of the reflecting member along the circumferential direction of the wound body face the opening side of the battery case and are in contact with the inner wall of the battery case.   The secondary battery according to claim 2, further comprising an insulating film that insulates the wound body and the battery case, wherein the insulating film is the reflecting member. The reflective member has an adhesive layer,
The secondary adhesive according to any one of claims 2 to 3, wherein the adhesive layer is adhered to the bent portion disposed on the opening side of the wound body to stop the wound body. battery.

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