JP5614396B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

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

  As the non-aqueous electrolyte secondary battery, for example, a lithium ion secondary battery is well known. In recent years, lithium ion secondary batteries have become increasingly important as power sources mounted on vehicles using electricity as a driving source, or power sources mounted on personal computers, portable terminals, and other electrical products.

  In the lithium ion secondary battery, lithium ions in the electrolyte solution are responsible for electrical conduction. Some lithium ion secondary batteries include a conductive layer formed by winding a positive electrode sheet and a negative electrode sheet with a separator interposed therebetween. The positive electrode sheet is configured by applying a positive electrode mixture layer on the surface of the positive electrode current collector, and an uncoated portion of the positive electrode mixture layer is formed on one end side in the width direction. Similarly, the negative electrode sheet is configured by applying a negative electrode mixture layer to the surface of the negative electrode current collector, and an uncoated portion of the negative electrode mixture layer is formed on the other end side in the width direction.

  In general, in a lithium ion secondary battery, lithium ions move from a positive electrode mixture layer to a negative electrode mixture layer and take charge of electrical conduction. Therefore, the width of the negative electrode mixture layer is applied to be larger than the width of the positive electrode mixture layer so that lithium ions moving from the positive electrode mixture layer can be received. Here, in the unlikely event that the separator is damaged due to the collapse of the lithium ion secondary battery or the like, the uncoated portion of the positive electrode mixture layer and the negative electrode mixture layer are short-circuited, and self-discharge is increased.

  In order to prevent a short circuit between the uncoated portion of the positive electrode mixture layer and the negative electrode mixture layer of the lithium ion secondary battery, several measures have been taken. For example, in a lithium ion secondary battery described in Patent Document 1, an alumina layer is applied to an uncoated portion of the positive electrode mixture layer in order to insulate the uncoated portion of the positive electrode mixture layer from the negative electrode mixture layer. A secondary battery to be worked is disclosed.

  However, in the lithium ion secondary battery disclosed in Patent Document 1, in the portion where the alumina layer of the positive electrode mixture layer is coated, lithium ions cannot move, so it does not function as the positive electrode mixture layer. Accordingly, the battery capacity of the lithium ion secondary battery is reduced. Therefore, in the lithium ion secondary battery, there is no problem such as a decrease in battery capacity, and it is a problem to prevent a short circuit between the uncoated portion of the positive electrode mixture layer and the negative electrode mixture layer.

JP 2005-310619 A

  The problem to be solved by the present invention is to provide a non-aqueous electrolyte secondary battery capable of preventing short circuit between the uncoated portion of the positive electrode mixture layer and the negative electrode mixture layer without any adverse effects such as a decrease in battery capacity. It is to be.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

According to a first aspect of the present invention , there is provided a wound electrode body configured by winding a positive electrode sheet and a negative electrode sheet through a separator, and the positive electrode sheet is formed by applying a positive electrode mixture layer on a surface of a positive electrode current collector. An uncoated portion of the positive electrode mixture layer is formed on one end side in the width direction, and the negative electrode sheet is formed by applying a negative electrode mixture layer on the surface of the negative electrode current collector, An uncoated portion of the negative electrode mixture layer is formed on the other end side of the negative electrode mixture layer, and the length of the negative electrode mixture layer in the width direction is longer than the length of the positive electrode mixture layer in the width direction. a liquid electrolyte secondary battery, the uncoated portion of the positive-electrode mixture layer, at the width direction, the carbon layer from one end of the positive-electrode mixture layer to the predetermined position is applied to the carbon layer is polyfluorinated Biniderin is contained more than 20 wt%, the carbon layer is formed on the porous, its porosity more than 30% And it is intended to be 80% or less.

In Claim 2 , It is a nonaqueous electrolyte secondary battery of Claim 1 , Comprising: Between the said positive mix layer and the said positive electrode collector in the coating part of the said positive mix layer of the said positive electrode sheet In between, a carbon layer is applied from one end side of the positive electrode mixture layer to a predetermined position in the width direction, and the carbon layer contains 20 wt% or more and 90 wt% or less of polyvinylidene fluoride. is there.

  According to the nonaqueous electrolyte secondary battery of the present invention, there is no adverse effect such as a decrease in battery capacity, and a short circuit between the uncoated portion of the positive electrode mixture layer and the negative electrode mixture layer can be prevented.

The perspective view which showed the whole structure of the lithium ion secondary battery which is embodiment of this invention. Similarly AA sectional drawing in FIG. The schematic diagram which shows the positive electrode sheet, negative electrode sheet, and separator which concern on 1st embodiment. The schematic diagram which shows the positive electrode sheet, negative electrode sheet, and separator which concern on 2nd embodiment. The schematic diagram which shows the positive electrode sheet, negative electrode sheet, and separator which concern on 3rd embodiment.

A lithium ion secondary battery 100 will be described with reference to FIG.
In addition, below, it demonstrates according to the width direction, depth direction, and height direction which are shown by FIGS.

  The lithium ion secondary battery 100 is a first embodiment of a non-aqueous electrolyte secondary battery according to the present invention.

  The configuration of the lithium ion secondary battery 100 will be described. The lithium ion secondary battery 100 includes a battery case 111, a lid body 112, a positive electrode terminal 121, and a negative electrode terminal 122.

  The battery case 111 has a rectangular parallelepiped shape. In the battery case 111, a flat wound electrode body 50 and an electrolyte solution described later are accommodated. The lid body 112 is configured to close an opening that is opened at the top of the battery case 111. The lid body 112 is provided with a positive terminal 121 and a negative terminal 122 for external connection. Part of the positive terminal 121 and the negative terminal 122 protrudes to the surface side of the lid body 112.

The wound electrode body 50 will be described with reference to FIG.
2 shows a cross-sectional view in the AA direction in FIG.

  The wound electrode body 50 is housed inside the battery case 111. The wound electrode body 50 is formed by winding a long sheet-like positive electrode sheet 10 and a long sheet-like negative electrode sheet 20 with a width direction as an axis through a long sheet-like separator 30. (See FIGS. 3 to 5). More specifically, the wound electrode body 50 is obtained by superposing the positive electrode sheet 10 and the negative electrode sheet 20 together with the two separators 30 and 30 and winding the positive electrode sheet 10, the negative electrode sheet 20, and the separator 30. -It is formed into a flat shape by crushing 30 wound bodies from the depth direction and expanding in the height direction.

  In the wound electrode body 50, in the wound positive electrode sheet 10, the positive electrode current collector 11 is exposed without forming a later-described positive electrode mixture layer 12 at one end along the width direction. ing. On the other hand, in the wound electrode body 50, also in the negative electrode sheet 20, the negative electrode current collector 21 is exposed at the other end in the width direction without forming the negative electrode mixture layer 22 described later. A positive electrode terminal 121 is joined to the exposed end of the positive electrode current collector 11. On the other hand, a negative electrode terminal 122 is joined to the exposed end of the negative electrode current collector 21.

The positive electrode sheet 10 of the lithium ion secondary battery 100 will be described with reference to FIG.
FIG. 3 schematically shows the positive electrode sheet 10, the negative electrode sheet 20, and the separator 30 before being wound to form the wound electrode body 50.

  The positive electrode sheet 10 is configured by applying a positive electrode mixture layer 12 to the surface of a positive electrode current collector 11. In addition, the surface means the surface on the front side and the back side of the sheet when the positive electrode sheet 10 is viewed as a sheet. The positive electrode sheet 10 has an uncoated portion 13 of the positive electrode mixture layer 12 formed on one end side in the width direction. The positive electrode mixture layer 12 contains a positive electrode active material and a binder.

  A carbon layer 40 is coated on the surface of the uncoated portion 13 of the positive electrode sheet 10. The carbon layer 40 is coated from one end side of the positive electrode mixture layer 12 to a predetermined position of the uncoated portion 13 in the width direction. As a carbon material constituting the carbon layer 40, for example, acetylene black (AB) is used. Further, the carbon layer 40 is assumed to contain 20 wt% or more of polyvinylidene fluoride as a resin. The carbon layer 40 of this embodiment contains 50 wt% of polyvinylidene fluoride.

  That is, the carbon layer 40 is composed of a carbon material that is a conductive material and polyvinylidene fluoride that is a resin. The carbon layer 40 exhibits conductivity in a normal state where the carbon layer 40 is not heated, and when heated, the polyvinylidene fluoride, which is a resin, is crystallized to increase resistance and exhibit insulation.

  In the width direction of the carbon layer 40, a length L from one end side of the positive electrode mixture layer 12 to a predetermined position of the uncoated portion 13 is 0.05 mm or more. The length L of the carbon layer 40 of this embodiment is 2 mm.

  The thickness T of the carbon layer 40 is 1 μm or more and 20 μm or less. The thickness T of this embodiment is 2 μm.

  The negative electrode sheet 20 is configured by applying a negative electrode mixture layer 22 on the surface of a negative electrode current collector 21. The negative electrode sheet 20 has an uncoated portion 23 of the negative electrode mixture layer 22 formed on the other end side in the width direction. The length in the width direction of the negative electrode mixture layer 22 of the negative electrode sheet 20 is applied so as to be longer than the length in the width direction of the positive electrode mixture layer 12 of the positive electrode sheet 10.

  The separator 30 is a sheet interposed between the positive electrode sheet 10 and the negative electrode sheet 20. The separator 30 is disposed so as to be in contact with the positive electrode mixture layer 12 of the positive electrode sheet 10 and the negative electrode mixture layer 22 of the negative electrode sheet 20. And it has the function of forming a conductive path (conductive path) between the electrodes by preventing the short circuit accompanying the contact of the active material layer in the positive electrode sheet 10 and the negative electrode sheet 20 and impregnating the electrolyte in the pores of the separator 30. .

The operation of the lithium ion secondary battery 100 will be described.
If the separator 30 is damaged due to the collapse of the lithium ion secondary battery 100 or the like, the carbon layer 40 applied to the positive electrode mixture layer 12 and the negative electrode mixture layer 22 are once brought into conduction. When the carbon layer 40 and the negative electrode mixture layer 22 are once conducted, heat due to conduction is generated. The resin of the carbon layer 40 in the vicinity where the separator 30 is damaged is crystallized by heat generated by conduction.

As the resin of the carbon layer 40 is crystallized, the carbon layer 40 is highly resistant to electrical conduction. When the resistance of the carbon layer 40 is increased, the electrical conductivity in the vicinity of the damaged separator 30 is locally blocked. When the conduction is locally interrupted, the voltage drop behavior of the lithium ion secondary battery 100 stops.

The effect of the lithium ion secondary battery 100 will be described.
According to the lithium ion secondary battery 100, the carbon layer 40 applied to the uncoated portion 13 of the positive electrode mixture layer 12 is crystallized by heat generated by conduction, whereby the positive electrode mixture layer 12 is not coated. A short circuit between the working part 13 and the negative electrode mixture layer 22 can be prevented.

  Moreover, since the carbon layer 40 has sufficient conductivity in a normal state where it is not heated, the battery capacity of the lithium ion secondary battery 100 is not reduced by being applied to the uncoated portion 13.

  Furthermore, by setting the length L of the carbon layer 40 to 0.05 mm or more, a sufficient conductivity blocking effect can be obtained, and a voltage effect behavior can be obtained.

  In addition, by setting the thickness T of the carbon layer 40 to 1 μm or more, a sufficient conductivity blocking effect can be obtained. At the same time, by setting the thickness T of the carbon layer 40 to 20 μm or less, the flexibility of the carbon layer 40 is lost, and the carbon layer 40 can be prevented from peeling off from the uncoated portion 13.

The positive electrode sheet 210 of the lithium ion secondary battery 200 will be described with reference to FIG.
FIG. 4 schematically shows the positive electrode sheet 210, the negative electrode sheet 220, and the separator 230 before being wound to form a wound electrode body.

  The lithium ion secondary battery 200 is a second embodiment of the non-aqueous electrolyte secondary battery according to the present invention.

The configuration of the lithium ion secondary battery 200 will be described.
Since the wound electrode body (not shown), the negative electrode sheet 220, the separator 230, and the like of the lithium ion secondary battery 200 are the same as those of the lithium ion secondary battery 100 of the first embodiment, description thereof is omitted.

  The positive electrode sheet 210 is configured by coating a positive electrode mixture layer 212 on the surface of a positive electrode current collector 211. The positive electrode sheet 210 has an uncoated portion 213 of the positive electrode mixture layer 212 formed on one end side in the width direction. The positive electrode mixture layer 212 contains a positive electrode active material and a binder.

  A carbon layer 240 is coated on the surface of the uncoated portion 13 of the positive electrode sheet 210. The carbon layer 240 is coated from one end side of the positive electrode mixture layer 212 to a predetermined position of the uncoated portion 213 in the width direction.

  In the width direction of the carbon layer 40, a length L from one end side of the positive electrode mixture layer 212 to a predetermined position of the uncoated portion 13 is set to 0.05 mm or more. The length L of the carbon layer 240 of this embodiment is 2 mm.

  The thickness T of the carbon layer 40 is 1 μm or more and 20 μm or less. The thickness T of the carbon layer 40 of this embodiment is 2 μm.

  In the coating portion of the positive electrode mixture layer 212, the positive electrode mixture layer 212 (positive electrode mixture) from one end side of the positive electrode mixture layer 212 in the width direction between the positive electrode mixture layer 212 and the positive electrode current collector 211. The carbon layer 240 is applied up to a predetermined position between the layer 212 and the positive electrode current collector 211.

  The predetermined position in the width direction is from a position of 10% or more to a position of 100% or less when one end side in the width direction is a 0% position and the other end side in the width direction is a 100% position. In the present embodiment, the carbon layer 240 is coated between the positive electrode mixture layer 212 and the positive electrode current collector 211 at a predetermined position in the width direction of 100%, that is, in the width direction. Shall.

  The carbon layer 240 is composed of a carbon material such as acetylene black, which is a conductive substance, and polyvinylidene fluoride, which is a resin. The carbon layer 240 contains 20 wt% or more and 90 wt% or less of polyvinylidene fluoride. The carbon layer 240 of this embodiment contains 50 wt% of polyvinylidene fluoride.

The operation of the lithium ion secondary battery 200 will be described.
If the separator 230 is damaged due to the collapse of the lithium ion secondary battery 200 or the like, the carbon layer 240 applied to the positive electrode mixture layer 212 and the negative electrode mixture layer 222 are once conducted. Once the carbon layer 240 and the negative electrode mixture layer 222 are electrically connected, heat due to the conduction is generated. The resin of the carbon layer 240 is entirely crystallized by heat generated by conduction.

  When the resin of the carbon layer 240 is entirely crystallized, the positive electrode mixture layer 212 has a high resistance to electrical conduction. By increasing the resistance of the positive electrode mixture layer 212, the amount of mobile charge due to charging or discharging that should be performed in the positive electrode mixture layer 212 is suppressed. By suppressing the mobile charge amount of the lithium ion secondary battery 200, the voltage or current behavior of the lithium ion secondary battery 200 is significantly reduced.

The effect of the lithium ion secondary battery 200 will be described.
According to the lithium ion secondary battery 200, the carbon layer 240 applied to the uncoated portion 213 of the positive electrode mixture layer 212 is crystallized by heat generated by conduction, whereby the positive electrode mixture layer 212 is not applied. A short circuit between the portion 213 and the negative electrode mixture layer 222 can be prevented.

  Further, an abnormal state of the lithium ion secondary battery 200 such as when the separator 230 is damaged can be detected by a significant decrease in the voltage or current of the lithium ion secondary battery 200.

  Since other effects are the same as those of the lithium ion secondary battery 100 of the first embodiment, description thereof is omitted.

The positive electrode sheet 310 of the lithium ion secondary battery 300 will be described with reference to FIG.
FIG. 5 schematically shows the positive electrode sheet 310, the negative electrode sheet 320, and the separator 330 before being wound to form a wound electrode body.

  The lithium ion secondary battery 300 is a third embodiment of the non-aqueous electrolyte secondary battery according to the present invention.

The configuration of the lithium ion secondary battery 300 will be described.
Since the wound electrode body (not shown), the negative electrode sheet 320, the separator 330, and the like of the lithium ion secondary battery 300 are the same as those of the lithium ion secondary battery 100 of the first embodiment, description thereof is omitted.

  The positive electrode sheet 310 is configured by applying a positive electrode mixture layer 312 to the surface of a positive electrode current collector 311. The positive electrode sheet 310 has an uncoated portion 313 of the positive electrode mixture layer 312 formed on one end side in the width direction. The positive electrode mixture layer 312 contains a positive electrode active material and a binder.

  A carbon layer 340 is coated on the surface of the uncoated portion 313 of the positive electrode sheet 310. The carbon layer 340 is coated from one end side of the positive electrode mixture layer 312 to a predetermined position of the uncoated portion 313 in the width direction. The carbon layer 340 is mainly composed of a carbon material such as acetylene black, which is a conductive substance, and polyvinylidene fluoride, which is a resin. It is assumed that the carbon layer 340 contains 20 wt% or more of polyvinylidene fluoride. The carbon layer 340 of this embodiment contains 50 wt% of polyvinylidene fluoride.

  The carbon layer 340 is configured to be porous. Specifically, the carbon paste before the carbon layer 340 is applied to the uncoated portion 313 is mixed with a foaming agent and applied, and the applied carbon layer 340 is foamed to empty the carbon layer 340. A hole is formed. As the foaming agent, for example, azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, 4,4′oxybis or the like is used. Further, the porosity of the carbon layer 340 configured to be porous is set to be 30% or more and 80% or less.

  In the width direction of the carbon layer 40, a length L from one end side of the positive electrode mixture layer 12 to a predetermined position of the uncoated portion 13 is 0.05 mm or more. The length L of the carbon layer 340 of this embodiment is 2 mm.

  The thickness T of the carbon layer 340 is 1 μm or more and 20 μm or less. The thickness T of the carbon layer 340 of the present embodiment is 2 μm.

  Since the operation of the lithium ion secondary battery 300 is the same as that of the lithium ion secondary battery 100 of the first embodiment, the description thereof is omitted.

The effect of the lithium ion secondary battery 300 will be described.
According to the lithium ion secondary battery 300, the carbon layer 340 applied to the uncoated portion 313 of the positive electrode mixture layer 312 is crystallized by heat generated by conduction, whereby the positive electrode mixture layer 312 is not coated. A short circuit between the portion 313 and the negative electrode mixture layer 322 can be prevented.

  Further, by forming the carbon layer 340 to be porous, it is possible to prevent the separator 330 from being damaged during a load or impact. Furthermore, since the porosity is 30% or more, the load applied to the carbon layer 340 or energy due to impact can be sufficiently absorbed. On the other hand, since the porosity is 80% or less, the strength of the carbon layer 340 can be prevented from being damaged by an external force without being impaired.

  Since other effects are the same as those of the lithium ion secondary battery 100 of the first embodiment, description thereof is omitted.

DESCRIPTION OF SYMBOLS 10 Positive electrode sheet 11 Positive electrode collector 12 Positive electrode compound material layer 13 Uncoated part 20 Negative electrode sheet 21 Negative electrode collector 22 Negative electrode compound material layer 23 Uncoated part 30 Separator 40 Carbon layer 100 Lithium ion secondary battery

Claims (2)

A wound electrode body configured by winding a positive electrode sheet and a negative electrode sheet through a separator,
The positive electrode sheet is configured by applying a positive electrode mixture layer on the surface of the positive electrode current collector, and an uncoated portion of the positive electrode mixture layer is formed on one end side in the width direction,
The negative electrode sheet is configured by applying a negative electrode mixture layer on the surface of the negative electrode current collector, and an uncoated portion of the negative electrode mixture layer is formed on the other end side in the width direction,
The length in the width direction of the negative electrode mixture layer is a non-aqueous electrolyte secondary battery configured to be longer than the length in the width direction of the positive electrode mixture layer,
In the uncoated portion of the positive electrode mixture layer, in the width direction, a carbon layer is applied from one end side of the positive electrode mixture layer to a predetermined position,
Wherein the carbon layer, contains polyvinylidene Biniderin more than 20 wt%,
The carbon layer is formed to be porous, and its porosity is 30% or more and 80% or less.
Non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to claim 1 ,
A carbon layer between one end side of the positive electrode mixture layer and a predetermined position in the width direction between the positive electrode mixture layer and the positive electrode current collector in the coating portion of the positive electrode mixture layer of the positive electrode sheet Is coated,
The carbon layer includes 20% by weight or more and 90% by weight or less of polyvinylidene fluoride.
Non-aqueous electrolyte secondary battery.

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