JP6505859B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

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

  Patent Document 1 proposes a technique for preventing a short circuit by preventing a cutting edge of a positive electrode lead from overlapping a negative electrode active material coated portion in an electrode winding group of a cylindrical lithium ion battery.

Patent No. 4305035

  However, in the technique of Patent Document 1, it is necessary to widen the uncut width of the base foil of a portion not used as a current collection lead, and when the positive electrode mixture is rolled at high density, bending of the electrode occurs and the original positive electrode It reduces the effect of being a method for increasing the mixture density.

  The present invention has been made in view of the above-described point, and the object of the present invention is to short-circuit a negative electrode due to the cutting edge of the positive electrode tab portion without widening the uncut width of the positive electrode metal foil. It is providing the nonaqueous electrolyte secondary battery of the structure which can be prevented.

  The non-aqueous electrolyte secondary battery of the present invention, which solves the above problems, is a non-aqueous electrolyte secondary battery having an electrode group in which positive electrodes and negative electrodes are alternately arranged with a separator interposed therebetween and stacked. The positive electrode includes a positive electrode base provided with a positive electrode mixture layer on both sides of a positive electrode metal foil, and a positive electrode tab portion which protrudes from the positive electrode base and the positive electrode metal foil is exposed. A protective layer is provided at the proximal end of the

  According to the present invention, a short circuit between the positive electrode and the negative electrode can be prevented via burrs of the positive electrode metal foil in the positive electrode tab portion. In addition, the subject except having mentioned above, a structure, and an effect are clarified by description of the following embodiment.

FIG. 1 is an external perspective view of a prismatic secondary battery of Example 1; The disassembled perspective view which shows the state which attached the electrode group to the cover assembly. The perspective view which shows one specific example of an electrode group. The perspective view which shows the other specific example of an electrode group. The figure explaining the positional relationship of a positive electrode, a negative electrode, and a separator. BB sectional drawing of FIG. 5A. The figure which expands and shows the A section of FIG. 5A. The figure which expands and shows the B section of FIG. 5B. The figure which shows typically the process of forming a positive mix layer and a protective layer. The figure which shows typically the process of forming a positive electrode tab part. FIG. 7 is an external perspective view of a non-aqueous electrolyte secondary battery according to Example 2; The figure which expands and shows the A section of FIG.

  An embodiment in which the non-aqueous electrolyte secondary battery of the present invention is applied to a prismatic secondary battery will be described below with reference to the drawings.

  In the non-aqueous electrolyte secondary battery, it is required to increase the density of the active material mixture in order to improve the capacity density. In order to increase the density, a step of rolling the active material mixture applied to the metal foil with a roll press device is general. At this time, in the case of an electrode having a wound-type electrode group, in which the metal foil to which the active material is not applied for current collection is applied at one end and the active material mixture is applied to the other end, strong linear pressure In the case of rolling with, the portion to which the active material is applied is strongly rolled, while the portion not applied is relatively weakly rolled, which causes a difference in the elongation of the metal foil and causes the electrode to bend. .

  In order to avoid this, for example, it has been proposed to cut away a metal foil portion to which an active material is not applied, leaving a portion to be a current collection tab. In this case, it is effective to cut the portion not used as the current collection tab to the nearest end of the application boundary of the active material mixture and minimize the exposed width of the metal foil in order to avoid the above-mentioned bending.

  On the other hand, in general, in the non-aqueous electrolyte secondary battery, by arranging the electrodes such that all of the positive electrodes face the negative electrode, Li ions moving from the positive electrode to the negative electrode during charging may be acicularly precipitated and short circuited. I'm avoiding the danger. In the case where the width of the metal foil in the portion not used as a lead is narrowed as described above, if all the positive electrode active material coated portions are arranged to face the negative electrode active material coated portion, they will be used as cut leads The cutting edge of the metal foil of a part is arrange | positioned in the position which opposes a negative electrode active material.

  The cutting edge of the positive electrode metal foil is isolated from the negative electrode through the separator, but it is feared that the separator will be damaged to cause a short circuit when bundling and bending the lead portion for welding to the current collecting component etc. Be done. That is, although rolling is performed with high strength in order to increase the density of the positive electrode mixture containing the positive electrode active material of the non-aqueous electrolyte secondary battery, the active material is applied to prevent the electrode from bending in this step. When a configuration is adopted in which the metal foil portion which is not removed is cut away leaving a portion to be a lead for current collection, the cutting edge of the metal foil lead is prone to burrs and curls due to stress during processing, which is caused by this There is a concern that a short circuit may occur between the negative electrode and the positive electrode due to the breakage of the separator.

On the other hand, in the non-aqueous electrolyte secondary battery of the present invention, a protective layer is provided at the base end of the positive electrode tab portion and in the region facing the adjacent negative electrode, and the positive electrode metal foil in the positive electrode tab portion It is possible to prevent a short circuit between the positive electrode and the negative electrode through the burrs.
Example 1
FIG. 1 is an external perspective view of a prismatic secondary battery of Example 1, and FIG. 2 is an exploded perspective view showing a state in which an electrode group is attached to a lid assembly.

  The non-aqueous electrolyte secondary battery of Example 1 to which the present invention is applied is a prismatic secondary battery 1, and is, for example, a lithium ion secondary battery used as a power source of a hybrid vehicle, an electric vehicle, or the like. The prismatic secondary battery 1 has a battery container including a prismatic battery can 2 for housing the electrode group 4 and a battery lid 3 for closing the opening of the battery can 2. The battery can 2 and the battery lid 3 are formed by subjecting a metal material such as aluminum or an aluminum alloy to pressing or the like. The battery can 2 has a rectangular box shape formed by deep drawing, and the battery lid 3 has a rectangular flat plate shape that closes the opening of the battery can 2. The battery lid 3 is welded to the battery can 2 to seal the opening.

  A positive electrode external terminal 11 and a negative electrode external terminal 21 are disposed at positions on both ends in a direction along the long side of the battery lid 3. A gas discharge valve 5 is disposed at a position near the center in the long side direction of the battery cover 3. At a side position of the gas discharge valve 5, an injection hole 6 for injecting an electrolytic solution into the battery is disposed. The liquid injection hole 6 is sealed by welding the liquid injection valve 7 to the battery lid 3 after injecting the electrolytic solution. As the electrolytic solution, for example, a non-aqueous electrolytic solution in which a lithium salt such as lithium hexafluorophosphate (LiPF6) is dissolved in a carbonate-based organic solvent such as ethylene carbonate can be used.

  The positive electrode current collector 12 and the negative electrode current collector 22 are fixed to the back surface side of the battery lid 3. The positive electrode current collector 12 is crimped and fixed to the battery cover 3 integrally with the positive electrode external terminal 11 by a positive electrode connection terminal which penetrates the battery cover 3, and is electrically connected to the positive electrode external terminal 11. The negative electrode current collector 22 is crimped and fixed to the battery cover 3 integrally with the negative electrode external terminal 21 by a negative electrode connection terminal penetrating the battery cover 3, and is electrically connected to the negative electrode external terminal 21.

  In addition, although not particularly illustrated, insulating resin is provided between the positive electrode connection terminal and the negative electrode connection terminal and the battery lid 3 and between the positive electrode current collector 12 and the negative electrode current collector 22 and the battery lid 3 respectively. Is interposed and insulated. As described above, the positive electrode external terminal 11, the negative electrode external terminal 21, the positive electrode current collector 12, the negative electrode current collector 22 and the like are fixed to the battery lid 3 to constitute a lid assembly. And the electrode group 4 is attached to this lid assembly.

  The electrode group 4 attached to the lid assembly is housed in the battery can 2 in a state of being covered by an insulating case (not shown). The material of the insulating case is an insulating resin such as polypropylene. Thereby, the inner surface of the battery can 2 and the electrode group 4 are electrically insulated.

  The electrode group 4 has a structure in which the positive electrode 31 and the negative electrode 41 are flatly wound and stacked with the separator 51 interposed therebetween. A plurality of positive electrode tab portions 35 are disposed at one end of the electrode group 4 in the winding axial direction, and a negative electrode tab portion 45 is disposed at the other end. The positive electrode tab portion 35 and the negative electrode tab portion 45 are bundled at the center position in the thickness direction of the electrode assembly 4 and integrally joined to the positive electrode current collector 12 and the negative electrode current collector 22 by ultrasonic welding. At this time, the positive electrode ribbon 13 and the negative electrode ribbon 23 are brought into contact with and welded integrally with each other so that the positive electrode tab portion 35 and the negative electrode tab portion 45 are not torn apart by the vibration due to the ultrasonic wave.

  In the specific example shown in FIG. 3, the positive electrode tab portion 35 and the negative electrode tab portion 45 are provided only in the flat portion of the flat portion and the curved portion of the electrode group 4, but as in the other specific example shown in FIG. Alternatively, the positive electrode tab portion 35 and the negative electrode tab portion 45 may be provided on both the flat portion and the curved portion of the electrode group 4 and joined to the positive electrode current collector 12 and the negative electrode current collector 22 respectively.

  5A illustrates the positional relationship between the positive electrode, the negative electrode, and the separator, FIG. 5B is a cross-sectional view taken along the line B-B in FIG. 5A, and FIG. 6A is an enlarged view of a portion A in FIG. 6B is an enlarged view of a portion B of FIG. 5B.

  The positive electrode 31 has a positive electrode base 34 in which a positive electrode mixture layer 33 is provided on both surfaces of the positive electrode metal foil 32, and a positive electrode tab portion 35 which protrudes from the positive electrode base 34 and exposes the positive electrode metal foil 32. The positive electrode base 34 has a band shape having a long side and a short side, and a plurality of positive electrode tab portions 35 are provided at equal intervals on the long side 34 a on one side in the width direction of the positive electrode base 34 There is. The edge 33 a on one side in the width direction of the positive electrode mixture layer 33 is provided at a position separated by a predetermined distance x 1 from the long side 34 a of the positive electrode base 34. The edge 33 b on the other side in the width direction is provided at the same position as the long side 34 b of the positive electrode base 34. In the present embodiment, although the positive electrode tab portion 35 and the positive electrode base 34 are integrally provided, a separately provided member may be connected later.

  The negative electrode 41 has a negative electrode base 44 in which the negative electrode mixture layer 43 is provided on both surfaces of the negative electrode metal foil 42, and a negative electrode tab 45 that protrudes from the negative electrode base 44 and exposes the negative metal foil 42. The negative electrode base 44 has a band shape having a long side and a short side, and a plurality of negative electrode tab portions 45 are provided at equal intervals on the long side 44 a on one side in the width direction of the negative electrode base 44 There is. The edge 43 b on one side in the width direction of the negative electrode mixture layer 43 is provided at the same position as the long side 44 b on one side in the width direction of the negative electrode base 44, and the edge on the other side in the width direction of the negative electrode mixture layer 43. 43a is provided at a position spaced apart from the long side 44a of the negative electrode base 44 with a predetermined distance.

  For example, as shown in FIG. 5B, the positive electrode base 31 of the positive electrode 31 is formed narrower than the negative electrode base 44 of the negative electrode 41. When the positive electrode 31 and the negative electrode 41 are wound with the separator 51 interposed therebetween, the pair of long sides 34 a and 34 b of the positive electrode base 34 is wider than the pair of long sides 44 a and 44 b of the negative electrode base 44. It is arranged at the position of the direction outer side (rolling axial direction outer side).

  As shown in FIG. 6A, the positive electrode 31 is formed by cutting out a portion other than the positive electrode tab portion 35 of the positive electrode metal foil 32 protruding from the positive electrode mixture layer 33 to the vicinity of the positive electrode mixture layer 33. . The width x1 from the positive electrode mixture layer 33 to the long side 34a of the positive electrode base 34 is the position of the edge 43b of the negative electrode mixture layer 43 and the edge of the positive electrode mixture layer 33 on one side in the width direction of the electrode assembly 4 It is formed to be smaller than the distance difference x2 from the position of 33a.

  The positive electrode metal foil 32 is made of an aluminum alloy foil having a thickness of about 20 to 30 μm, and the negative electrode metal foil 42 is made of a copper alloy foil having a thickness of about 15 to 20 μm. The positive electrode active material contained in the positive electrode mixture layer 33 is a lithium-containing transition metal double oxide such as lithium manganate, and the negative electrode active material contained in the negative electrode mixture layer 43 can reversibly absorb and release lithium ions. Carbon materials such as natural graphite. The material of the separator 51 is a porous polyethylene resin.

  As shown in FIG. 6A, the positive electrode tab portion 35 protrudes from the long side 34 a of the positive electrode base 34 toward the outer side in the width direction of the positive electrode 31 with a substantially constant tab width. The positive electrode tab portion 35 is formed in an arc portion 35a so that the tab width of the positive electrode tab portion 35 becomes gradually narrower as it moves from the long side 34a of the positive electrode base 34 toward the tip of the positive electrode tab portion 35. And a straight portion 35b which is formed in a straight line toward the tip end continuously with the R portion 35a. The R portion 35 a of the positive electrode tab portion 35 is provided at the boundary between the positive electrode base 34 and the positive electrode base 34 in order to prevent breakage and breakage of the positive electrode tab 35.

  The R portion 35 a is disposed at a position overlapping the negative electrode mixture layer 43 of the negative electrode 41. As described later, when the positive electrode tab portion 35 is formed by cutting with a rotary cutter, burrs may occur at the cutting edge of the positive electrode metal foil 32, and burrs are most likely to be generated in the R portion 35a. The R portion 35a is an end portion of the positive electrode metal foil 32 usually about 15 μm, and when burrs are generated at the time of forming the positive electrode tab portion 35, for example, when bundled, it is a porous resin film usually about 30 μm There is a possibility of penetrating the separator 51 and causing a short circuit.

  In the present embodiment, the protective layer 36 is provided in the base end portion of the positive electrode tab portion 35 and in the region facing the adjacent negative electrode 41. The protective layer 36 is provided at a width corresponding to at least the R portion 35 a of the positive electrode tab portion 35, and in the present embodiment, the end of the protective layer 36 is in the width direction than the edge 43 b of the negative electrode mixture layer 43 It is provided to be located outside.

  The protective layer 36 is formed, for example, by applying an insulating member on the positive electrode metal foil 32. The insulating member is simple to apply and dry a resin in which polyvinylidene fluoride is dissolved in NMP, but contains an inorganic filler such as alumina, or contains an inorganic material having no conductivity such as lithium carbonate. It is also possible, and does not limit the composition of the insulating member.

  The protective layer 36 has a predetermined thickness, and when burrs occur on the positive electrode metal foil 32, the protrusion height of the burrs from the protective layer 36 can be reduced. Therefore, it is possible to prevent the burr of the positive electrode metal foil 32 of the R portion 35 a from breaking through the separator and causing a short circuit.

  In this embodiment, the insulating member is applied not only to the base end of the positive electrode tab portion 35 but also to the region between the edge 33 a of the positive electrode mixture layer 33 and the long side 34 a of the positive electrode base 34. Is provided. That is, the protective layer 36 is located at the base end of the positive electrode tab portion 35 from the edge 33 a of the positive electrode mixture layer 33 and outside in the width direction than the edge 43 b of the negative electrode mixture layer 43 of the adjacent negative electrode 41. It is provided over the width x3 of The application width x3 of the protective layer 36 is preferably larger than the distance difference x2 between the side end position of the negative electrode mixture layer 43 and the side end position of the positive electrode mixture layer 33 on one side in the width direction of the electrode group 4.

  By providing the protective layer 36 also in the region between the edge 33 a of the positive electrode mixture layer 33 and the long side 34 a of the positive electrode base 34, the positive electrode mixture layer when burrs are generated at the cutting edge of the long side 34 a The protrusion height of the burr from 33 can be reduced. Therefore, it is possible to prevent the burrs of the positive electrode metal foil 32 from breaking through the separator 51 and shorting with the adjacent negative electrode 41.

  FIG. 7 is a view schematically showing a step of forming a positive electrode mixture layer and a protective layer, and FIG. 8 is a view schematically showing a step of forming a positive electrode tab portion.

  The method of forming the positive electrode 31 includes a step of applying the positive electrode mixture on both surfaces of the positive electrode metal foil 32, and a step of cutting one long side of the positive electrode metal foil 32 to form the positive electrode tab portion 35.

  In the present embodiment, when applying the positive electrode mixture, application of an insulating member for forming the protective layer 36 is also performed simultaneously. By thus applying the insulating member simultaneously with the positive electrode mixture, the manufacturing tact can be shortened. Coating of the insulating member is performed by a die coater. For example, as shown in FIG. 7, the positive electrode mixture is applied to the positive electrode metal foil 32 moved in the coating direction using the nozzle 62 for applying the insulating member separately from the nozzle 61 for applying the positive electrode mixture. Apply an insulating member at a position adjacent to

  Then, for example, as shown in FIG. 8, the positive electrode tab portion 35 is formed by cutting the end portion on one side in the width direction of the positive electrode metal foil 32 using a rotary cutter 63 rotating in the processing direction. The formation of the positive electrode tab portion 35 is performed on both ends of the coated portion, and the rolling process is performed in this state, thereby equalizing the extension in the winding direction and preventing the bending of the electrode.

According to this embodiment, since the protective layer 36 is provided at the base end of the positive electrode tab portion 35 and in the region facing the adjacent negative electrode 41, burrs are generated at the cutting edge of the positive electrode metal foil 32. Thus, the burr can be prevented from breaking through the separator and shorting with the negative electrode 41.
Example 2
A second embodiment will now be described with reference to FIGS. 9 and 10.

  FIG. 9 is an external perspective view of the non-aqueous electrolyte secondary battery according to Example 2, and FIG. 10 is an enlarged view of a portion A of FIG. In addition, the detailed description is abbreviate | omitted by attaching the same code | symbol to the component similar to Example 1. FIG.

  A characteristic feature of this embodiment is that the protective layer is formed by extending the positive electrode mixture layer 33 of the positive electrode base 34 to the base end portion of the positive electrode tab portion 35 and a region facing the adjacent negative electrode 41. .

  In the present embodiment, the positive electrode mixture layer 33 is provided over the entire surface of the positive electrode base 34, and is further provided continuously at the base end of the positive electrode tab portion 35. The positive electrode mixture layer 33 at the base end of the positive electrode tab portion 35 is provided across the width corresponding to the R portion 35 a and forms a protective layer. The positive electrode mixture layer 33 at the base end of the positive electrode tab portion 35 preferably covers the entire area facing the adjacent negative electrode 41, but is not limited to such a configuration, and it is most likely to generate burrs. It may be provided to cover only the width corresponding to the R portion 35a, which has the effect of reducing the possibility of a short circuit.

  In the protective layer, the edge 33 c of the positive electrode mixture layer 33 in the positive electrode tab portion 35 is positioned inward of the edge 43 b of the negative electrode mixture layer 43 in the width direction of the positive electrode 31. The positive electrode 31 and the negative electrode 41 are stacked and arranged such that the edge 33 c of the positive electrode mixture layer 33 at the base end of the positive electrode tab portion 35 is positioned inward in the width direction than the edge 43 b of the negative electrode mixture layer 43 It prevents the solid precipitation of Li ions moving from the positive electrode to the negative electrode during charging.

  The positive electrode mixture layer 33 provided at the base end of the positive electrode tab portion 35 has a predetermined thickness, and when burrs occur at the cutting edge of the positive electrode metal foil 32, the positive electrode mixture layer 33 from the positive electrode mixture layer 33 The protrusion height of the burr can be reduced. In addition, since the positive electrode mixture layer 33 is provided up to the long side 34 a of the positive electrode base 34, when burrs are generated at the cutting edge of the long side 34 a, the protrusion height of the burr from the positive electrode mixture layer 33 It can be lowered. Therefore, it is possible to prevent the burrs of the positive electrode metal foil 32 from breaking through the separator 51 and shorting with the adjacent negative electrode 41.

  In the above-described first and second embodiments, although the case where the negative electrode 41 has the negative electrode tab portion 45 has been described as an example, the present invention is not limited to this configuration. For example, the pressure required for rolling the negative electrode 41 is Even if it is small and there is no concern that the negative electrode 41 may be curved even if it is not shaped like a plurality of such negative electrode tabs 45, there is no need to process such a plurality of negative electrode tabs 45, and a constant width It is also possible to use a negative electrode metal foil as the current collector.

  Moreover, in the above-mentioned Example 1, 2, although the case where the non-aqueous-electrolyte secondary battery of this invention was applied to the square secondary battery 1 was demonstrated to the example, it is not limited to this structure, For example, The present invention can also be applied to a cylindrical secondary battery having cylindrical electrode groups. The electrode group 4 is not limited to the wound type, and may be applied to, for example, a laminated type in which positive and negative electrodes in the form of a rectangular sheet are alternately stacked and stacked. Moreover, in the above-described first and second embodiments, although the case where the R portion 35a is provided at the base end portion of the positive electrode tab portion 35 is described as an example, providing the R portion 35a is not essential. May be

  As mentioned above, although the embodiment of the present invention was explained in full detail, the present invention is not limited to the above-mentioned embodiment, and various designs are possible in the range which does not deviate from the spirit of the present invention described in the claim. It is possible to make changes. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to one having all the described configurations. Further, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Furthermore, with respect to a part of the configuration of each embodiment, it is possible to add / delete / replace other configurations.

1 square secondary battery (non-aqueous electrolyte secondary battery)
4 electrode group 31 positive electrode 32 positive electrode metal foil 33 positive electrode mixture layer 33a, 33b edge 34 positive electrode base 34a long side 35 positive electrode tab portion 35a R portion 36 protective layer 41 negative electrode 42 negative metal foil 43 negative electrode mixture layer 43a, 43b edge 44 negative electrode base 44a long side 51 separator

Claims (6)

A positive electrode and the negative electrode, a nonaqueous electrolyte secondary battery having an electrode group are laminated wound into a flat shape by interposing the separator therebetween,
The positive electrode includes a positive electrode base provided with a positive electrode mixture layer on both sides of a positive electrode metal foil, and a positive electrode tab portion which protrudes from the positive electrode base and exposes the positive electrode metal foil.
The negative electrode has a negative electrode base provided with a negative electrode mixture layer on both sides of a negative electrode metal foil, and a negative electrode tab portion projecting from the negative electrode base and exposing the negative electrode metal foil.
A protective layer is provided at the proximal end of the positive electrode tab portion ,
In the protective layer, an edge of the positive electrode mixture layer is positioned inward in a width direction of the positive electrode than an edge of the negative electrode mixture layer, and an edge of the positive electrode is an edge of the negative electrode mixture layer. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is positioned on the outer side in the width direction of the positive electrode and further on the inner side in the width direction of the separator than the edge of the separator .   The non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode base and the positive electrode tab portion are integrally formed.   The non-aqueous electrolyte secondary battery according to claim 2, wherein the protective layer is provided at least at a base end portion of the positive electrode tab portion and in a region facing the adjacent negative electrode.   The non-aqueous electrolyte secondary battery according to claim 3, wherein the protective layer is formed of an insulating member.   The non-aqueous electrolyte secondary battery according to claim 4, wherein the insulating member and the positive electrode mixture layer are applied to the positive electrode metal foil in the same step. The positive electrode tab portion has an R portion at the boundary with the positive electrode base,
The non-aqueous electrolyte secondary battery according to claim 3, wherein the protective layer is provided in a width corresponding to at least the R portion.

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