JP6693695B2 - Storage element - Google Patents

Description

  The present invention relates to a power storage element, and particularly to a power storage element including a separator.

  Conventionally, a power storage element including a separator is known (see, for example, Patent Document 1).

  The above-mentioned Patent Document 1 is a battery (electric storage element) in which a positive electrode, a separator, and a negative electrode are sequentially laminated, and the positive electrode and the negative electrode have a mixture layer formed on a current collector. A portion including a forming region and a mixture layer non-forming region in which the mixture layer is not formed, and a portion near the end of the separator facing the mixture layer non-forming region of the positive electrode is heat-treated to close the pores (shut down). ) Is disclosed, a battery is disclosed. According to such a configuration, when metal powder is mixed inside the battery, metal ions are generated, but metal ions are generated by heat-treating a portion near the end of the separator facing the mixture layer non-forming region of the positive electrode. It is described that by preventing the permeation, metal dendrites are concentrated at the end of the mixture layer forming region of the negative electrode to form a metal dendrite, which can prevent the metal dendrite from reaching the positive electrode and causing a short circuit. ing.

JP 2012-69283 A

  However, the heat treatment of the separator causes thermal contraction (contraction). Due to the thermal contraction of the separator, a portion where the separator does not exist may be generated between the positive electrode and the negative electrode, and the positive electrode and the negative electrode may come into contact with each other to cause a short circuit in the power storage element (manufacturing defect). And, the study for suppressing the manufacturing defect is not sufficiently conducted.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to subject a separator to heat contraction to bring the positive electrode and the negative electrode into contact with each other when a separator is subjected to a heat treatment step to produce a storage element. The present invention is to provide a power storage element that suppresses short-circuiting and manufacturing defects.

  In order to achieve the above object, an electricity storage device according to one aspect of the present invention is an electricity storage device including a positive electrode, a negative electrode, and a separator, and the positive electrode has a positive electrode mixture layer formed on a positive electrode current collector. And a mixture layer non-forming region in which the positive electrode mixture layer is not formed, and the separator is perpendicular to the first direction (MD direction) at 150 ° C. and the first direction. The heat shrinkage ratios in the second direction (TD direction) are both 10% or less, and the portion of the separator facing the area where the mixture layer is not formed is heat treated.

  According to the electricity storage device of the above aspect, when the electricity storage device is manufactured by subjecting the separator to the heat treatment, it is possible to prevent the separator from contracting and causing the positive electrode and the negative electrode to come into contact with each other to cause a short circuit, resulting in a manufacturing defect. ..

  In the electricity storage element according to the above aspect, the air permeability of the heat-treated portion of the separator is preferably 30 times or more that of the non-heat-treated portion of the separator. According to this configuration, when metal powder is mixed inside the power storage element when the power storage element is manufactured, it is possible to suppress the occurrence of a minute short circuit due to the formation of a metal dendrite when the power storage element is used.

  In the electricity storage device according to the above aspect, an insulating layer is preferably formed on at least one surface of the separator. According to this configuration, when the storage element is manufactured by subjecting the separator to the heat treatment step, it is possible to more effectively prevent the manufacturing failure from occurring due to thermal contraction of the separator and short circuit due to contact between the positive electrode and the negative electrode. it can.

  In the electricity storage device according to the above aspect, preferably, the negative electrode includes a negative electrode mixture layer formed on the negative electrode current collector, and in a direction in which the mixture layer non-forming region projects from the end of the positive electrode mixture layer. The distance from the end of the negative electrode mixture layer to the end of the separator is larger than the distance from the end of the positive electrode mixture layer to the end of the negative electrode mixture layer. According to this configuration, when metal powder is mixed inside the power storage element when the power storage element is manufactured, it is more effective that a metal dendrite is formed and a micro short circuit occurs when the power storage element is used. Can be suppressed.

  According to the present invention, as described above, when the storage element is manufactured by subjecting the separator to the heat treatment, it is possible to prevent the separator from being thermally contracted and the positive electrode and the negative electrode to come into contact with each other to cause a short circuit, resulting in a manufacturing defect. It is possible to provide a power storage element that operates.

1 is a diagram showing a battery according to a first exemplary embodiment of the present invention. FIG. 3 is a diagram showing a positive electrode, a separator and a negative electrode of the battery according to the first exemplary embodiment of the present invention. FIG. 4 is an enlarged view of an end portion of the battery separator according to the first embodiment of the present invention on the X1 direction side. FIG. 6 is a diagram showing a positive electrode, a separator and a negative electrode of a battery according to a second exemplary embodiment of the present invention. FIG. 9 is a diagram showing a positive electrode, a separator and a negative electrode of a battery according to a first modified example of the first embodiment of the present invention. FIG. 11 is an enlarged view of an end portion on the X1 direction side of a separator according to a second modified example of the first embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)

  First, the configuration of the battery 1 according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3. The battery 1 is an example of the "electric storage element" in the present invention.

  A battery (for example, a lithium-ion battery) 1 according to the first embodiment of the present invention includes a power generation element 2 as shown in FIG. 1. As shown in FIG. 2, the power generation element 2 has a horizontally long separator 5 interposed between a horizontally long positive electrode 3 and a horizontally long negative electrode 4, and winds the positive electrode 3, the negative electrode 4, and the separator 5 together. It is formed by The power generation element 2 is housed inside the case 6, as shown in FIG. Further, a battery lid 7 is attached to the case 6 by laser welding so that an electrolyte (not shown) and the power generation element 2 are housed inside the case 6 so as to close the opening of the case 6. The positive electrode 3 is electrically connected to the positive electrode terminal 11 via the positive electrode current collector grip portion 8, and the negative electrode 4 is electrically connected to the negative electrode terminal 10 via the negative electrode current collector grip portion 9. In addition, the longitudinal direction of the separator 5 in the horizontally long shape before winding is the first direction (MD direction), and the lateral direction perpendicular to the first direction is the second direction (TD direction). In other words, in the state where the battery 1 is manufactured (the state after winding), the first direction is along the winding axis (winding axis), and the second direction is the winding axis. It is the extending direction. In addition, in FIG. 1, the state in which the positive electrode 3, the negative electrode 4, and the separator 5 are wound is simplified to show the power generation element 2.

  As shown in FIGS. 2 and 3, the positive electrode 3 has a positive electrode current collector 31 made of an aluminum foil or an aluminum alloy foil, and a positive electrode mixture containing a positive electrode active material applied to both surfaces of the positive electrode current collector 31. The positive electrode mixture layer 32 is included. The positive electrode 3 has a positive electrode mixture layer forming region R1 in which the positive electrode mixture layer 32 on the X2 direction side is formed and a positive electrode mixture layer non-forming region in which the positive electrode mixture layer 32 on the X1 direction side is not formed. R2 (a positive electrode mixture uncoated region). Further, the positive electrode mixture layer non-forming region R2 protrudes from the end of the positive electrode mixture layer forming region R1 on the X1 direction side so as to project in the X1 direction side. In addition, in the positive electrode current collector 31, a portion protruding outside the negative electrode 4 (X1 direction side) in the X direction has a width W0 (about 10.5 mm, see FIG. 3). Further, the protruding portion is entirely included in the positive electrode mixture layer non-forming region R2. Further, the positive electrode active material is not particularly limited, and various positive electrode active materials can be used. The positive electrode mixture layer forming region R1 is an example of the “mixture layer forming region” in the present invention. The positive electrode mixture layer non-forming region R2 is an example of the "mixture layer non-forming region" in the present invention.

  The negative electrode 4 includes a negative electrode current collector 41 made of a copper foil, and a negative electrode mixture layer 42 in which both surfaces of the negative electrode current collector 41 are coated with a negative electrode mixture containing a negative electrode active material. The negative electrode 4 includes a negative electrode mixture layer forming region R3 in which the negative electrode mixture layer 42 on the X1 direction side is formed and a negative electrode mixture layer non-forming region in which the negative electrode mixture layer 42 on the X2 direction side is not formed. R4 (a region not coated with the negative electrode mixture). Further, the negative electrode mixture layer non-forming region R4 protrudes from the end of the negative electrode mixture layer forming region R3 on the X2 direction side so as to project to the X2 direction side. That is, the positive electrode mixture layer non-forming region R2 and the negative electrode mixture layer non-forming region R4 are formed so as to extend in opposite directions in the X direction. Further, the negative electrode active material is not particularly limited, and various negative electrode active materials can be used.

  In the X direction, the width of the negative electrode mixture layer 42 (width of the negative electrode mixture layer formation region R3) is larger than the width of the positive electrode mixture layer 32 (width of the positive electrode mixture layer formation region R1). Further, both ends of the negative electrode mixture layer 42 in the X direction are configured to extend outside the both ends of the positive electrode mixture layer 32 in the X direction.

  The separator 5 is arranged between the positive electrode 3 and the negative electrode 4. Further, in the X direction, the width of the separator 5 is larger than the width of the positive electrode mixture layer 32 (width of the positive electrode mixture layer forming region R1) and the width of the negative electrode mixture layer 42 (width of the negative electrode mixture layer forming region R3). Is also big. Further, both ends of the separator 5 in the X direction are respectively arranged in the X direction of the positive electrode mixture layer 32 (width of the positive electrode mixture layer forming region R1) and the negative electrode mixture layer 42 (width of the negative electrode mixture layer forming region R3). Is configured to extend outward from both ends of the.

  The separator 5 is made of a porous material. Specifically, as the material of the separator 5, a polyolefin resin such as PE (polyethylene) or PP (polypropylene) can be used. These materials may be used alone or in combination of two or more. Further, the separator 5 thermally contracts (contracts) by applying heat of a predetermined temperature. Here, in the first embodiment, the separator 5 has a physical property that the heat shrinkage rates in the first direction (MD direction) and the second direction (TD direction) at 150 ° C. are both 10% or less.

  The separator 5 includes a portion heat-treated at 180 ° C. (hereinafter, referred to as a heat treatment portion 51) on the X1 direction side, and the holes of the heat treatment portion 51 are closed (shut down). Specifically, the separator 5 includes a heat treatment section 51 in a portion facing the positive electrode mixture layer non-forming region R2 (near the end on the X1 direction side that does not face the positive electrode mixture layer 32). The heat treatment part 51 is formed over the entire region in the thickness direction (Y direction) of the separator 5 and extends to a position corresponding to the end of the positive electrode mixture layer forming region R1 on the X1 direction side in the X direction. Has been formed. That is, the positive electrode mixture layer 32 (positive electrode mixture layer forming region R1) and the non-heat-treated portion of the separator 5 (hereinafter referred to as the non-heat-treated portion 52) are located at substantially the same position in the X direction in the X1 direction. Correspondingly formed to be located.

  Further, in the separator 5, the heat treatment section 51 can be formed so that the air permeability thereof is 30 times or more the air permeability (sec / 100 cc) of the non-heat treatment section 52.

  In the separator 5, the porosity of the non-heat-treated portion 52 (the porosity of the separator 5 before the heat treatment) is preferably 50% or less, more preferably 30% or more and 50% or less, and 40% or more 50% or more. It is even more preferable that it is not more than%.

  Further, when the separator 5 is interposed between the positive electrode 3 and the negative electrode 4 and wound, a heat treatment is performed by a roller (not shown) at 180 ° C. in the vicinity of the end portion on the X1 direction side (a portion corresponding to the heat treatment portion 51). Thus, the heat treatment section 51 is formed. 2 and 3, in order to clarify the heat treatment portion 51, the heat treatment portion 51 is represented by hatching that is denser than that of the non-heat treatment portion 52. The heat treatment section 51 is an example of the “heat-treated portion” in the present invention. The non-heat-treated portion 52 is an example of the “non-heat-treated portion” in the present invention.

  Further, as shown in FIG. 3, the heat treatment section 51 includes an outer region 51a on the end side (X1 direction side) of the separator 5 and an inner region 51b inside the outer region 51a. Specifically, the outer region 51a of the separator 5 is a negative electrode in the direction (X direction) in which the positive electrode mixture layer non-forming region R2 (positive electrode mixture uncoated region) protrudes from the end of the positive electrode mixture layer 32. It is a region from the portion corresponding to the end of the mixture layer 42 (negative electrode 4) on the X1 direction side to the end of the separator 5 on the X1 direction side. The inner region 51b of the separator 5 is located in the X1 direction side of the negative electrode mixture layer 42 from the portion corresponding to the X1 direction side end of the positive electrode mixture layer 32 (positive electrode mixture layer forming region R1) in the X direction. It is a region up to the portion corresponding to the end. The outer region 51a and the inner region 51b are examples of the "heat-treated portion" in the present invention.

  In the X direction, the outer region 51a has a width W1 of about 3.5 mm, and the inner region 51b has a width W2 of about 3.0 mm. That is, the width W1 of the outer region 51a is larger than the width W2 of the inner region 51b (the width X1 of the outer region 51a is about 1.17 times the width W2 of the inner region 51b).

  Further, the heat treatment part 51 of the separator 5 is formed by contraction (heat contraction) in the longitudinal direction (MD direction) and the lateral direction (TD direction) in a horizontally long state before winding. That is, since one end portion of the separator 5 in the X direction contracts in the longitudinal direction and the other end portion does not contract without undergoing the heat treatment process, the separator 5 is distorted. The larger the width of the separator 5 in the X direction, the smaller the degree of the distortion. Therefore, when heat-treating only one side of the separator 5 in the X direction as in the first embodiment, the width of the separator 5 in the X direction is preferably 110 mm or more. The width of the heat treatment part 51 in the X direction (the total width of the outer region 51a and the inner region 51b (= W1 + W2)) is preferably 3 mm or more and 10 mm or less. Further, it is preferable that the end of the heat treatment section 51 on the X1 direction side be located on the X2 direction side of the X1 direction end of the positive electrode current collector 31 (positive electrode mixture layer non-forming region R2).

  Further, in the first embodiment, since the separator 5 includes the heat treatment section 51 on the X1 direction side, when metal powder is mixed inside the battery 1 when the battery 1 is manufactured, when the battery 1 is used, It is possible to suppress the formation of a metal dendrite and the occurrence of a micro short circuit. This will be described in detail with reference to FIG.

  For example, when manufacturing the battery 1 (for example, when welding the negative electrode current collector grip 9 and the negative electrode mixture layer non-forming region R4 of the negative electrode current collector 41 or when cutting the negative electrode current collector 41). When powder is generated and the metal powder mixes inside the battery 1 and adheres to the positive electrode material mixture layer non-forming region R2, the metal powder is ionized by applying a positive electrode potential when the battery 1 is used. Due to the potential difference, the metal ions migrate from the positive electrode mixture layer non-forming region R2 toward the end of the negative electrode mixture layer forming region R3 on the X1 direction side, but face the positive electrode mixture layer non-forming region R2 of the separator 5. Since the portion includes the heat treatment portion 51, it becomes difficult for the metal ions to pass through the heat treatment portion 51, and the metal dendrite is concentrated at the end of the negative electrode mixture layer formation region R3 on the X1 direction side to cause a micro short circuit. Can be suppressed.

  Even if metal ions are concentrated at the end of the negative electrode mixture layer forming region R3 on the X1 direction side and a metal dendrite is formed, the separator 5 includes the heat treatment section 51, so that the metal dendrite can be treated by the heat treatment section 51. It is possible to suppress a minute short circuit by penetrating through and contacting the positive electrode 3.

  In addition, a metal dendrite is formed at the end of the negative electrode mixture layer formation region R3 on the X1 direction side, and the metal dendrite grows so as to pass through the outside (the X1 direction side) of the outer region 51a of the heat treatment unit 51 to grow the positive electrode 3 It is possible that a short circuit may occur due to contact with. As in the first embodiment, the width W1 of the outer region 51a is made larger than the width of the inner region 51b, so that the metal dendrite grows so as to pass through the outside of the outer region 51a (X1 direction side) and the positive electrode 3 It becomes difficult to contact with, and it is possible to suppress a minute short circuit.

  In the first embodiment, the following effects can be obtained.

  In the first embodiment, as described above, the separator 5 having a thermal shrinkage rate of 10% or less in the first direction (MD direction) and the second direction (TD direction) perpendicular to the first direction at 150 ° C. is used. The portion of the separator 5 facing the positive electrode mixture layer non-forming region R2 is heat-treated. The separator 5 is subjected to a heat treatment step by reducing the heat shrinkage rate of the separator 5 at 150 ° C. in both the first direction (MD direction) and the second direction (TD direction) perpendicular to the first direction to 10% or less. When the battery 1 is manufactured, it is possible to prevent the separator 5 from being thermally contracted and the positive electrode 3 and the negative electrode 4 to come into contact with each other to cause a short circuit, resulting in defective manufacturing.

  Further, in the first embodiment, as described above, the portion of the separator 5 facing the positive electrode mixture layer non-forming region R2 includes the heat treatment portion 51, so that when the battery 1 is manufactured, the inside of the battery 1 is When the metal powder is mixed, it is possible to suppress the formation of a metal dendrite and the occurrence of a minute short circuit when the battery 1 is used.

  In addition, in the first embodiment, as described above, the air permeability of the heat treatment part 51 of the separator 5 can be set to be 30 times or more the air permeability of the non-heat treatment part 52. As a result, the heat treatment section 51 of the separator 5 is less likely to allow metal ions to pass therethrough, and more difficult to penetrate metal dendrites, so that when the battery 1 is used, metal dendrites are formed and a micro short circuit is more likely to occur. Can be effectively suppressed.

  Further, in the first embodiment, as described above, the negative electrode 4 includes the negative electrode mixture layer 42 formed on the negative electrode current collector 41, and the positive electrode mixture layer non-forming region R2 is the end of the positive electrode mixture layer 32. In the direction projecting from the portion (X1 direction), the distance W1 (width of the outer region 51a in the X direction) from the end of the negative electrode mixture layer 42 to the end of the separator 5 is from the end of the positive electrode mixture layer 32. The distance W2 to the end of the negative electrode mixture layer 42 (width of the inner region 51b in the X direction) can be set to be larger. This makes it less likely that the metal dendrite grows from the end of the negative electrode mixture layer forming region R3 on the X1 direction side to pass through the outside of the outer region 51b (X1 direction side) and comes into contact with the positive electrode 3. Further, it is possible to more effectively suppress the occurrence of a minute short circuit due to the formation of a metal dendrite when the battery 1 is used.

(Second embodiment)
Next, the configuration of the battery 100 according to the second embodiment of the present invention will be described with reference to FIGS. 1 and 4. The battery 100 is an example of the "electric storage element" in the present invention.

  In the second embodiment, a battery 100 in which the insulating layer 53 is formed on the separator 5 will be described, which is different from the first embodiment in that the insulating layer 53 is formed on the surface of the separator 5 on the positive electrode 3 side. In addition, in the second embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

  As shown in FIG. 4, in the battery 100 according to the second embodiment, the heat shrinkage rates in the first direction (MD direction) and the second direction (TD direction) perpendicular to the first direction at 150 ° C. are both 10% or less. is there. The heat treatment section 51 of the separator 5 is provided near the end of the positive electrode 3 on the X1 direction side that does not face the positive electrode mixture layer 32. Further, the heat treatment section 51 is configured to directly face the positive electrode current collector 31 with the insulating layer 53 interposed therebetween. In the second embodiment, the insulating layer 53 is configured to be carried on substantially the entire surface of the separator 5 on the positive electrode 3 side (one side in the Y direction). Thereby, when the separator 5 is heat-treated, the degree of thermal contraction of the separator 5 is reduced. The insulating layer 53 is a layer containing inorganic particles and is arranged between the positive electrode and the negative electrode.

  The type of inorganic particles contained in the insulating layer 53 is not particularly limited, but examples thereof include oxide ceramics such as silica, alumina, boehmite, titania, zirconia, magnesia, ceria, yttria, zinc oxide, and iron oxide; silicon nitride. , Nitride ceramics such as titanium nitride, boron nitride; silicon carbide, calcium carbonate, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, kaolin clay, kaolinite, halloysite, pyrophyllite, montmorillonite, sericite, mica , Amethite, bentonite, asbestos, aluminosilicate, calcium silicate, magnesium silicate, diatomaceous earth, ceramics such as silica sand, and glass fiber. These inorganic particles may be used alone or in combination of two or more.

  The porosity of the insulating layer 53 is not particularly limited, but is preferably 70% or less, more preferably 40% or more and 70% or less, and further preferably 60% or more and 70% or less. .. The porosity of the non-heat-treated portion 52 of the separator 5 (the porosity of the separator 5 before the heat treatment) and the porosity of the insulating layer 53 are not particularly limited, but are preferably 60% or less as a whole, 30 % Or more and 55% or less, more preferably 45% or more and 50% or less.

  The other configurations of the second embodiment are similar to those of the first embodiment.

  In the second embodiment, the following effects can be obtained.

  In the second embodiment, as described above, the insulating layer 53 is formed on the surface of at least one side of the separator 5. As a result, since the separator 5 is supported on the insulating layer 53, it is less likely to undergo thermal contraction, and when the battery 5 is manufactured by subjecting the separator 5 to a heat treatment step, the separator 5 undergoes thermal contraction and the positive electrode 3 and the negative electrode 4 are formed. It is possible to more effectively suppress the occurrence of manufacturing defects due to contact with and short-circuiting.

  The other effects of the second embodiment are similar to those of the first embodiment.

  In order to confirm the effect of the present invention, a defect evaluation test of the power generation element was performed. The power generation elements of Examples 1 to 4 were manufactured using the separators A to D, and the power generation elements of Comparative Examples 1 to 3 were manufactured using the separators E to G to carry out a failure evaluation test. Specifically, a power generation element was manufactured using a positive electrode current collector made of aluminum foil, a negative electrode current collector made of copper foil, and a separator. At this time, horizontally long separators A to G having the same size were used as the separators before winding. Then, together with the positive electrode and the negative electrode, a roller (not shown) was used and wound in the vicinity of one end of the separators A to G while heat-treating at 180 ° C. Thereby, the power generation elements of Examples 1 to 4 and Comparative Examples 1 to 3 were produced in a state where the heat treatment part was formed on one end of the separators A to G.

(Example 1)
Power generation of Example 1 using a PE-made separator A having a heat shrinkage of 4% in the first direction (MD direction) and a heat shrinkage of 4% in the second direction (TD direction) at 150 ° C. The element was made. Further, the air permeability of the non-heat-treated portion of the separator A is 160 (sec / 100 cc) and the air permeability of the heat-treated portion is 13000 (sec / 100 cc). The value obtained by dividing the air permeability by the air permeability of the non-heat-treated portion was 81.3.

(Example 2)
Power generation in Example 2 using a PE separator B having a heat shrinkage rate of 2% at 150 ° C. in the first direction (MD direction) and a heat shrinkage rate of 3% in the second direction (TD direction). The element was made. Further, the air permeability of the non-heat-treated portion of the separator B is 240 (sec / 100 cc), and the air permeability of the heat-treated portion is 12500 (sec / 100 cc). The value obtained by dividing the air permeability by the air permeability of the non-heat-treated portion was 52.1.

(Example 3)
Power generation of Example 3 using a PE separator C having a heat shrinkage of 5% in the first direction (MD direction) and a heat shrinkage of 5% in the second direction (TD direction) at 150 ° C. The element was made. Further, the air permeability of the non-heat-treated portion of the separator C is 255 (sec / 100 cc), and the air permeability of the heat-treated portion is 10500 (sec / 100 cc). The value obtained by dividing the air permeability by the air permeability of the unheated portion was 41.2.

(Example 4)
Power generation of Example 4 using a PE separator D having a heat shrinkage of 10% in the first direction (MD direction) and a heat shrinkage of 10% in the second direction (TD direction) at 150 ° C. The element was made. Further, the air permeability of the non-heat-treated portion of the separator D is 350 (sec / 100 cc), and the air permeability of the heat-treated portion is 10500 (sec / 100 cc). The value obtained by dividing the air permeability by the air permeability of the non-heat-treated portion was 30.

(Comparative Example 1)
Power generation of Comparative Example 1 using a separator E made of PE having a heat shrinkage rate of 15% in the first direction (MD direction) and a heat shrinkage rate of 15% in the second direction (TD direction) at 150 ° C. The element was made. Further, the air permeability of the non-heat-treated portion of the separator E is 340 (sec / 100 cc), and the air permeability of the heat-treated portion is 11000 (sec / 100 cc). The value obtained by dividing the air permeability by the air permeability of the non-heat-treated portion was 32.4.

(Comparative example 2)
Power generation of Comparative Example 2 using a PE separator F having a heat shrinkage of 30% in the first direction (MD direction) and a heat shrinkage of 20% in the second direction (TD direction) at 150 ° C. The element was made. Further, the air permeability of the non-heat-treated portion of the separator F is 330 (sec / 100 cc), and the air permeability of the heat-treated portion is 10,000 (sec / 100 cc). The value obtained by dividing the air permeability by the air permeability of the non-heat-treated portion was 30.3.

(Comparative example 3)
Power generation of Comparative Example 3 using a PE separator G having a heat shrinkage of 55% in the first direction (MD direction) and a heat shrinkage of 30% in the second direction (TD direction) at 150 ° C. The element was made. Further, the air permeability of the non-heat-treated portion of the separator G is 300 (sec / 100 cc), and the air permeability of the heat-treated portion is 10,000 (sec / 100 cc). The value obtained by dividing the air permeability by the air permeability of the non-heat-treated portion was 33.3.

The heat shrinkage rates of the separators A to G were obtained by the following method. Specifically, each of the separators A to G was cut by 100 mm in the MD direction and 100 mm in the TD direction, and heated in an oven at 150 ° C. for 1 hour. At this time, in order to prevent the hot air in the oven from directly hitting the separator, the separator was heated with the upper surface and the lower surface of the separator sandwiched by paper. Then, after cooling the heated separator, the length (mm) in each of the MD direction and the TD direction was measured. Then, using the following equations (1) and (2), the heat shrinkage rate (%) in each of the MD direction and the TD direction was calculated.
Thermal shrinkage in MD direction (%) = [(100-length in MD direction after heating) / 100] × 100
... (1)
Thermal shrinkage in TD direction (%) = [(100−length in TD direction after heating) / 100] × 100
... (2)

  The air permeability of the non-heat-treated part and the air permeability of the heat-treated part of the separators A to G are determined by measuring the time taken for 100 cc of air to pass through the Gurley method (JIS8119) specified area. I got it.

(Defect evaluation test)
It was confirmed whether or not the power generation elements of Examples 1 to 4 and Comparative Examples 1 to 3 were defective. In the present invention, if a short circuit occurs in the produced power generation element, it is determined to be defective. Specifically, a predetermined voltage is applied to the power generating elements of Examples 1 to 4 and the power generating elements of Comparative Examples 1 to 3, and the resistance value is measured to perform an insulation check to determine whether a defect has occurred. It was confirmed.

  Table 1 shows the result of the failure evaluation test for each of the power generation elements of Examples 1 to 4 and Comparative Examples 1 to 3 produced by using the separators A to G.

  From the results of the defect evaluation test shown in Table 1, in the power generation elements of Examples 1 to 4 using the separators A to D, the number of defects is 8 or less per 100, that is, the defect occurrence rate is 8%. It was below. In the power generation elements of Example 1 and Example 3 using the separator A and the separator C having a small heat shrinkage ratio, the number of defectives was 2 for 100 (the defect occurrence rate was 2%). Particularly, in the power generation element of Example 2 using the separator B having the smallest thermal shrinkage, the defective number was 1 out of 100 (the defective occurrence rate was 1%), and the defective number was the minimum value.

  Further, in the power generation elements of Comparative Examples 1 to 3 using the separators E to G, the defective number was 13 or more per 100, that is, the defect occurrence rate was 13% or more. In particular, in the power generation element of Comparative Example 3 using the separator G (55% in MD direction, 30% in TD direction) having the largest heat shrinkage ratio, the number of defectives was 32 with respect to 100 (the defective occurrence rate was 32%. ), And became the largest. This is because when the separator was subjected to a heat treatment step to produce a power generation element, both the heat shrinkage rates of the separator in the MD direction and the TD direction at 150 ° C. exceeded 10%, so that the heat shrinkage of the separator resulted in the positive electrode and the negative electrode. It is considered that this is because a part where there is no separator was generated between and and a short circuit occurred.

  From the above, when the power generation element is manufactured by subjecting the separator to the heat treatment step, both the heat shrinkage rates of the separator in the first direction (MD direction) and the second direction (TD direction) perpendicular to the first direction at 150 ° C. It was found that the manufacturing defect of the electricity storage device can be reduced by setting the content to 10% or less.

  Further, by setting the value obtained by dividing the air permeability of the heat-treated portion of the separator by the air permeability of the non-heat-treated portion to 30 or more, the heat-treated portion of the separator is less likely to permeate metal ions, and It is considered that the metal dendrites are more difficult to penetrate, and it is possible to suppress the formation of the metal dendrites and the occurrence of a minute short circuit when the power storage element is used.

  The embodiments and examples disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments and examples but by the scope of claims for patent, and further includes meanings equivalent to the scope of claims for patent and all modifications within the scope.

  For example, in the first and second embodiments, the heat treatment part 51 (the outer region 51a having the width W1 and the inner side of the width W2) is provided in the vicinity of the end portion of the separator in the X1 direction (a portion facing the positive electrode mixture layer non-forming region R2). Although the example of forming the region 51b) is shown, the present invention is not limited to this. In the present invention, as in the first modification shown in FIG. 5, the heat treatment section 51 may be formed in the vicinity of both ends of the separator 5 in the X direction.

  When the heat treatment section 51 is formed only in the vicinity of one side end in the X direction of the separator 5 as in the first and second embodiments, the heat treatment section 51 thermally contracts in the longitudinal direction (MD direction), so that the separator 5 is distorted. The degree of the distortion increases as the width of the separator 5 in the X direction decreases. On the other hand, in the case where the heat treatment parts 51 are formed near both ends of the separator 5 in the X direction, both ends where the heat treatment parts 51 are formed are thermally contracted, so that the degree of strain generated in the separator 5 is reduced. Therefore, when the width of the separator 5 in the X direction is 100 mm or less, it is preferable to form the heat treatment section 51 near both ends of the separator 5 in the X direction. Further, when the heat treatment portion 51 is formed in the vicinity of both ends in the X direction of the separator 5, the width in the X direction of one heat treatment portion 51 (the total width (W1 + W2) of the outer region 51a and the inner region 51b) is 5 mm or more and 10 mm or more. The following is preferable.

  Moreover, in the said 1st and 2nd embodiment, although the example which completely close | closes (shuts down) the hole of a heat processing part was shown, this invention is not limited to this. In the present invention, it is not necessary to completely close the holes in the heat treatment section. That is, the air permeability of the heat treatment part 51 may be 30 times or more the air permeability of the non-heat treatment part 52.

  In the first and second embodiments, the width W1 of the outer region 51a of the heat treatment part 51 is about 1.17 times the width W2 of the inner region 51b of the heat treatment part 51 in the X direction. However, the present invention is not limited to this. In the present invention, the width W1 of the outer region 51a may be a size other than about 1.17 times as long as it is larger than one time the width W2 of the inner region 51b.

  Moreover, in the said 1st and 2nd embodiment, although the example which the heat processing part was formed over the whole region of the thickness direction of the separator was shown, this invention is not limited to this. In the present invention, as in the second modification shown in FIG. 6, the heat treatment portion 151 including the outer region 151a and the inner region 151b is formed by heat-treating the surface on one side (Y1 direction side) in the thickness direction of the separator 105. It may have been done. The heat treatment part 151 (the outer region 151a and the inner region 151b) is an example of the “heat-treated part” in the present invention. The non-heat-treated parts 152 and 152a are examples of the “non-heat-treated part” in the present invention.

  In this case, it is preferable that the heat treatment section 151 be formed near the surface of the separator 105 on the negative electrode side. The heat treatment unit 151 can suppress migration of metal ions to the negative electrode side (the end portion of the negative electrode mixture layer formation region R3 on the X1 direction side). Further, it is possible to prevent metal ions from being trapped in a portion of the non-heat-treated portion 152 that overlaps with the heat-treated portion 151 in the thickness direction of the separator 105 (non-heat-treated portion 152a) and the metal ion returning to the electrolyte. ..

  Further, although the insulating layer is provided on the surface of the separator on the positive electrode side in the second embodiment, the present invention is not limited to this. In the present invention, an insulating layer may be provided on the surface of the separator on the negative electrode side. Further, in the present invention, an insulating layer may be provided on both surfaces of the positive electrode side and the negative electrode side separators.

1,100 battery (electric storage element)
3 Positive electrode 4 Negative electrode 5 Separator 31 Positive electrode current collector 32 Positive electrode mixture layer 41 Negative electrode current collector 42 Negative electrode mixture layer 51, 151 Heat treatment part (heat treated part)
51a, 151a Outer region (heat treated part)
51b, 151b Inner region (heat treated part)
52, 152, 152a Non-heat treated part (portion not heat treated)
53 Insulating layer R1 Positive electrode mixture layer forming region (mixture layer forming region)
R2 positive electrode mixture layer non-forming region (mixture layer non-forming region)

Claims (1)

A power storage element comprising a positive electrode, a negative electrode, and a separator,
The positive electrode has a mixture layer forming region where a positive electrode mixture layer is formed on the positive electrode current collector, and a mixture layer non-forming region where the positive electrode mixture layer is not formed,
The separator has a thermal shrinkage ratio of 10% or less at 150 ° C. in both the first direction (MD direction) and the second direction (TD direction) perpendicular to the first direction,
The portion of the separator facing the mixture layer non-forming region is heat treated ,
The negative electrode includes a negative electrode mixture layer formed on the negative electrode current collector,
In the direction in which the mixture layer non-forming region projects from the end of the positive electrode mixture layer, the distance from the end of the negative electrode mixture layer to the end of the separator is from the end of the positive electrode mixture layer. An electricity storage device, which is larger than the distance to the end of the negative electrode mixture layer .

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