JP2014225378A - Sealant for tab lead, tab lead and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealant for the tab lead of a laminated lithium ion secondary battery satisfying high reliability, insulation characteristics, and heat resistance of battery encapsulation entirely.SOLUTION: A sealant 1 for tab lead encapsulating the tab lead of a laminated lithium ion secondary battery has a three layer structure consisting of a laminate adhesive layer 5, an insulation layer 4, and a lead conductor adhesive layer 3 co-extruded. The laminate adhesive layer 5 is composed of a polypropylene-based resin having a melting point of 140°C or less, and a load deflection temperature of 70°C or more. The insulation layer 4 is composed of a polypropylene-based resin having a melting point of 145°C or more, and a load deflection temperature of 100°C or more. The lead conductor adhesive layer 3 is composed of a polymer alloy of acid modified polypropylene having a melting point of 135°C or less, and a polypropylene-based resin.

Description

  The present invention relates to a tab lead sealing material, a tab lead sandwiching a lead conductor with the tab lead sealing material, and a lithium ion secondary battery using the tab lead sealing material.

  Lithium ion secondary batteries have been widely used in consumer equipment applications because of their light weight and high energy density, but in recent years, they have been used for power tools and motorcycles that require higher output. Development is planned. In addition, against the background of environmental and energy problems, there is a demand for the spread as in-vehicle and industrial batteries.

In order to cope with such various uses, various types of lithium ion secondary batteries different from conventional cylindrical types such as a square type and a laminate type have been developed. Such various lithium ion secondary batteries can be classified from the following three viewpoints.
(1) Electrode structure: wound type, laminated type (2) Battery shape: cylindrical type, square type, sheet type (3) Exterior body: metal can type, laminated type Among these, conventionally, [(1) Lithium ion secondary batteries of the revolving type, (2) cylindrical type / square type, (3) metal can type] have been widely used, but recently, they are thin, high output and excellent in heat dissipation [( Development of lithium ion secondary batteries of 1) stacked type, (2) sheet type, (3) laminate type], so-called laminate type lithium ion secondary batteries, is progressing.

  Since the laminated lithium ion secondary battery uses an inexpensive and lightweight aluminum (Al) -based laminate sheet as an outer package, the cost is reduced and the energy density is improved as compared with the case of using a metal can. Is possible.

  A laminate-type lithium ion secondary battery has an electrode laminate in which positive plates and negative plates are alternately stacked via separators, and a pair of tab leads (connection terminals) connected to the positive plate and the negative plate, respectively. These have a structure in which they are sealed together with an electrolyte in a laminate sheet. The tab lead used here has a laminated structure in which an insulating sealing material is welded to a metal lead conductor.

The following points are mentioned as problems and required performance of the tab lead used in the laminate type lithium ion secondary battery.
(A) Liquid leakage: ensuring adhesion reliability between lead conductor and sealing material (high reliability of sealing)
(B) Initial insulation failure: Prevention of short circuit between the lead conductor by lamination sealing and the barrier layer (aluminum layer) of the laminate sheet (insulation characteristics)
(C) Use in a high temperature environment: ensuring adhesion reliability under high temperature conditions (60 to 70 ° C.) (heat resistance)
As a tab lead sealing material satisfying the above performances (a) to (c), a polypropylene resin is widely used from the viewpoint of chemical resistance, heat resistance and low cost. Further, a sealing material having a three-layer structure in which a high melting point resin layer is sandwiched between low melting point resin layers has been proposed (for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4).

JP 2008-192451 A JP 2001-297748 A JP-A-2005-243552 JP 2007-087801 A

  In patent document 1, while defining each melting | fusing point of the high melting point resin layer and low melting point resin layer which comprise a sealing material, the melting point difference of a high melting point resin layer and a low melting point resin layer shall be 20-25 degreeC, and also each resin By constituting the layer with acid-modified polypropylene, (a) high reliability of sealing and (b) insulating characteristics are compatible.

  However, since heat resistance generally decreases as the melting point is lowered, it is difficult to achieve both (b) insulation characteristics and (c) heat resistance with the above-described conventional technology. If the melting point of the low-melting acid-modified polypropylene is lowered with emphasis on the characteristics, the heat resistance is lowered.

  On the other hand, the sealing material described in Patent Document 2 defines the difference in melting point between the low melting point resin layer and the high melting point resin layer to be 30 ° C. or more, and the resin layer that adheres to the lead conductor is made of acid-modified polyolefin. (A) High reliability of sealing and (b) insulation characteristics are compatible.

  However, when different types of resins are used to have a melting point difference of 30 ° C. or more between the resin layers, the low melting point resin layer and the high melting point resin layer must be attached with an adhesive, Electrolytic solution resistance decreases. On the other hand, if an attempt is made to have a melting point difference of 30 ° C. or more between polypropylenes, there is no polypropylene having a melting point higher than 168 ° C., and therefore, it is necessary to use a polypropylene having a lower melting point, and (c) heat resistance Decreases.

  An object of the present invention is to provide a tab lead sealing material for a laminated lithium ion secondary battery that satisfies all of the high reliability, insulation characteristics, and heat resistance of battery sealing.

  Another object of the present invention is to provide a tab lead in which a lead conductor is sandwiched by the tab lead sealing material.

  Another object of the present invention is to provide a laminate type lithium ion secondary battery using the above tab lead sealing material.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  A tab lead sealing material for a laminated lithium ion secondary battery which is a preferred embodiment of the present invention has a three-layer structure comprising a coextruded laminate adhesive layer, an insulating layer and a lead conductor adhesive layer, and the laminate adhesive layer Is made of a polypropylene resin having a melting point of 140 ° C. or less and a deflection temperature under load of 70 ° C. or more, and the insulating layer is made of a polypropylene resin having a melting point of 145 ° C. or more and a deflection temperature under load of 100 ° C. or more. Consists of a polymer alloy of an acid-modified polypropylene having a melting point of 140 ° C. or less and a polypropylene resin.

  The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

  It is possible to provide a tab lead sealing material that satisfies all of the high reliability, insulation characteristics, and heat resistance of battery sealing.

It is sectional drawing which shows the structure of the sealing material for tab leads of embodiment. (A) is sectional drawing of the tab lead along the longitudinal direction of a lead conductor, (b) is sectional drawing of the tab lead along the width direction of a lead conductor. It is a top view which fractures | ruptures and shows a part of lithium ion secondary battery of embodiment. It is a disassembled perspective view which shows a part (thermal welding part of a laminate sheet) of a lamination-type lithium ion secondary battery. It is a perspective view explaining the outline of a 180 degree peeling test.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. In the embodiments, the description of the same or similar parts will not be repeated in principle unless particularly necessary. Furthermore, in the embodiment, “%” for the concentration, content, blending amount, and the like represents mass% unless otherwise specified.

(Embodiment)
FIG. 1 is a cross-sectional view showing the configuration of the tab lead sealing material of the present embodiment. The tab lead sealing material 1 has a three-layer structure in which a lead conductor adhesive layer 3 and a laminate adhesive layer 5 are laminated with an insulating layer 4 interposed therebetween. The lead conductor adhesive layer 3, the insulating layer 4 and the laminate adhesive layer 5 are all made of polypropylene resin. However, the polypropylene resin referred to here includes a copolymer of ethylene and propylene and a polymer alloy of polyethylene and polypropylene.

  The lead conductor adhesive layer 3 of the tab lead sealing material 1 is made of a polymer alloy of an acid-modified polypropylene and a polypropylene resin having excellent adhesion to a lead conductor described later.

  The acid-modified polypropylene is a polypropylene resin grafted with an unsaturated carboxylic acid, and in the present embodiment, one having a melting point of 140 ° C. or lower is used. When an acid-modified polypropylene having a melting point higher than 140 ° C. is used, the adhesive strength with the lead conductor is reduced as compared with a case where a melting point is 140 ° C. or lower. As a result, when the temperature inside the battery rises due to an internal short circuit and the internal pressure rises, there is a concern that the tab lead sealing material 1 may peel from the lead conductor and cause liquid leakage. In addition, since acid-modified polypropylene having a melting point higher than 140 ° C. has low initial adhesive strength, the adhesive strength in a high-temperature environment becomes weak and heat resistance is lowered.

  As the unsaturated carboxylic acid, maleic anhydride is preferably used. The unsaturated carboxylic acid only needs to be grafted into acid-modified polypropylene, and examples of the method include graft copolymerization and graft modification such as a solvent method and a melting method.

  In the acid-modified polypropylene, the graft amount of the unsaturated carboxylic acid is preferably 3 to 10%, more preferably 4 to 8%, and particularly preferably 5 to 7%. When the graft amount is less than 3%, in order to obtain sufficient adhesive strength with the lead conductor, it is necessary to increase the amount of acid-modified polypropylene in the polymer alloy, which is disadvantageous in terms of cost. In addition, if the graft amount of unsaturated carboxylic acid is larger than 10%, the polarity of the acid-modified polypropylene itself becomes too high, resulting in poor compatibility with the polypropylene resin, resulting in a decrease in the mechanical strength of the polymer alloy. The adhesive strength with the lead conductor is reduced.

  Further, for the acid-modified polypropylene, the melt flow rate (hereinafter abbreviated as MFR) measured by JIS K7120 is preferably 10 to 900 g / 10 minutes, more preferably 50 to 500 g / 10 minutes, and 100 to 300% by mass. Is particularly preferred. There is a correlation between the MFR and the molecular weight of the polypropylene resin. The larger the MFR, the smaller the molecular weight, and the smaller the MFR, the larger the molecular weight. That is, when the MFR is larger than 900 g / 10 min, the molecular weight of the acid-modified polypropylene is too low, so that the entanglement effect with the polypropylene resin is reduced and the mechanical properties of the polymer alloy are lowered. On the other hand, when the MFR is less than 10 g / 10 minutes, it is difficult to obtain the above-mentioned graft amount of the unsaturated carboxylic acid.

  The ratio of the unsaturated carboxylic acid grafted to the whole polymer alloy (referred to as the amount of acid modification relative to the total amount of polymer alloy) is preferably about 0.1 to 2.0%, more preferably about 0.2 to 1.5%, and 0 About 3 to 1.2% is particularly preferable. When the acid modification amount is less than 0.1%, the adhesive strength with the lead conductor is lowered. On the other hand, when the acid modification amount is larger than 2.0%, the acid modification amount becomes excessive with respect to the adhesive strength with the lead conductor, and the blend of the acid modified polypropylene is more expensive than the polypropylene not subjected to acid modification treatment. Since the amount is excessive, it is disadvantageous in terms of cost.

  Next, as the insulating layer 4 of the tab lead sealing material 1, a polypropylene resin having a melting point of 145 ° C. or higher and a deflection temperature under load of 100 ° C. or higher is used. In a polypropylene resin having a melting point of less than 145 ° C., the melting point difference from the laminate adhesive layer 5 becomes small. At the time of battery sealing, heat welding is performed under the condition that the laminated adhesive layer 5 is melted. However, if the melting point difference from the insulating layer 4 is small, the insulating layer 4 also melts and flows out at the time of heat welding, resulting in a short circuit. There are things to do. In addition, when the deflection temperature under load is less than 100 ° C., the amount of deformation due to pressurization increases even if the melting point is not reached due to thermal welding at the time of sealing the battery, and as a result, a short circuit may occur. Furthermore, the melting point of the insulating layer 4 is preferably 20 ° C. or more higher than the melting point of the laminate adhesive layer 5. If the melting point difference between the insulating layer 4 and the laminate adhesive layer 5 is less than 20 ° C., a short circuit may occur due to thermal welding during battery sealing.

  Next, as the laminate adhesive layer 5 of the tab lead sealing material 1, a polypropylene resin having a melting point of 140 ° C. or lower and a deflection temperature under load of 70 ° C. or higher is used. In a polypropylene resin having a melting point higher than 140 ° C., the melting point difference from the insulating layer 4 is small. At the time of battery sealing, the laminate adhesive layer 5 is heated to the melting point or higher, so that if the difference in melting point from the insulating layer 4 is small, the insulating layer 4 also melts and flows out at the time of heat welding, resulting in a short circuit. . Further, when the deflection temperature under load is less than 70 ° C., the adhesive strength with the lead conductor 2 is remarkably lowered when the battery is left in a high temperature environment, and as a result, liquid leakage may occur.

  As a polypropylene resin having a melting point of 140 ° C. or lower and a deflection temperature under load of 70 ° C. or higher, a random copolymer (metallocene polypropylene) of ethylene and propylene polymerized by a metallocene catalyst can be suitably used. Compared with the polypropylene resin polymerized by the usual ZN (Ziegler-Natta) catalyst, the metallocene polypropylene has (1) narrow composition distribution, (2) few low regularity components, and (3) molecular weight distribution. Since it is narrow, a film having a low melting point and a high rigidity can be obtained.

  Therefore, when a metallocene polypropylene is used as the laminate adhesive layer 5, it is possible to achieve both a low melting point and a mechanical strength in a high temperature environment of about 60 to 70 ° C., and a larger melting point difference from the insulating layer 4. As a result, the insulation characteristics are improved. In addition, when the laminate adhesive layer 5 and a laminate sheet to be described later are thermally welded at the time of battery sealing, it becomes possible to perform welding at a lower temperature. It leads to tact shortening.

  Next, the tab lead in which the lead conductor is sandwiched by the tab lead sealing material 1 will be described. 2A is a cross-sectional view of the tab lead along the longitudinal direction of the lead conductor, and FIG. 2B is a cross-sectional view of the tab lead along the width direction of the lead conductor.

  The tab lead 6 is formed by arranging two tab lead sealing materials 1 so that the lead conductor adhesive layers 3 face each other and thermally welding the front and back surfaces of the lead conductor 2 and the lead conductor adhesive layer 3. It is. In the case of the positive electrode, the lead conductor 2 is preferably an Al foil, and in the case of the negative electrode, a Cu foil, a Ni foil, or a Ni-plated Cu foil is preferably used.

  The thermal welding between the tab lead sealing material 1 and the lead conductor 2 is performed under the condition that the pressure applied to the tab lead sealing material 1 is 0.06 to 0.25 MPa. And the maximum temperature of the interface temperature is within the range of the melting point of the polymer alloy constituting the lead conductor adhesive layer 3 to + 10 ° C.

  When the pressure applied to the tab lead sealing material 1 is less than 0.06 MPa, the pressure is not sufficiently transmitted to the portions along the both side edges of the lead conductor 2, and the molten resin does not flow sufficiently and encloses bubbles. As a result, the reliability of sealing is lowered. Further, since the deformation of the tab lead sealing material 1 due to the pressure is small, due to the variation in thickness that occurs during the manufacture of the tab lead sealing material 1, the parallelism with the lead conductor 2 is reduced during heat welding, and the welding becomes uneven. Therefore, it becomes a factor of liquid leakage. On the other hand, when the pressure applied to the tab lead sealing material 1 is higher than 0.25 MPa, the tab lead sealing material 1 flows to reduce the thickness, resulting in a decrease in insulation characteristics.

  Further, if the maximum value of the interface temperature between the lead conductor adhesive layer 3 and the lead conductor 2 that is reached by thermal welding is less than the melting point of the polymer alloy constituting the lead conductor adhesive layer 3, the welding becomes insufficient and liquid leakage occurs. It becomes a factor of. On the other hand, when the maximum value of the interface temperature between the lead conductor adhesive layer 3 and the lead conductor 2 reached by heat welding is higher than the melting point of the polymer alloy constituting the lead conductor adhesive layer 3 + 10 ° C., the tab lead sealing material 1 Flows to reduce the thickness, and as a result, the insulation characteristics at the time of battery sealing deteriorate.

  When the tab lead sealing material 1 and the lead conductor 2 are thermally welded, it is only necessary to pay attention to only the maximum value of the interface temperature between the lead conductor adhesive layer 3 and the lead conductor 2 reached by the heat welding. It is not necessary to hold for a certain time. Therefore, by setting an appropriate heat source surface temperature and welding time, it is possible to reduce the tact time of heat welding. For example, if the heat source surface temperature is increased, the time required to reach the target temperature is shortened, so that the welding time can be shortened. However, in this case, the rate of temperature rise at the interface temperature between the lead conductor adhesive layer 3 and the lead conductor 2 is increased, and the welding time is in the range of the melting point to + 10 ° C. of the polymer alloy constituting the lead conductor adhesive layer 3 described above. Since the range of this is also shortened, more accurate management of the welding time is required.

  Next, a laminated lithium ion secondary battery using the tab lead 6 will be described. FIG. 3 is a top view showing a part of the laminated lithium ion secondary battery of the present embodiment in a cutaway manner.

  The lithium ion secondary battery 7 includes a laminate sheet 13 which is an exterior body, and an electrode laminate 8 housed therein. The electrode laminate 8 has a structure in which a plurality of positive plates and negative plates (not shown) are alternately stacked via separators, and a positive lead conductor attachment 9 is provided at one end of the positive plate. A negative electrode lead conductor mounting portion 10 is provided at one end of the plate. A positive electrode lead conductor 11 is welded to the positive electrode lead conductor attachment portion 9, and a negative electrode lead conductor 12 is welded to the negative electrode lead conductor attachment portion 10. The electrode laminate 8 is sealed by thermally welding the laminate sheets 13 together after being housed in the laminate sheet 13 together with an electrolyte solution (not shown).

  FIG. 4 is an exploded perspective view showing a part of the lithium ion secondary battery 7 (thermal welding portion of the laminate sheet 13). The laminate sheet 13 is composed of, for example, three layers of a base material layer 14 / aluminum layer 15 / thermal welding layer 16, and an outer peripheral portion of the thermal welding layer 16 is formed as a thermal welding portion 17 with a predetermined width. Therefore, the laminate sheet 13 is folded in two and overlapped, and the heat-welded portions 17 of the heat-welded layer 16 are heat-welded to seal the electrode laminate 8 and the electrolytic solution.

  In addition, at the time of sealing, at least a portion of the positive electrode lead conductor 11 and the negative electrode lead conductor 12 drawn out of the laminate sheet 13 and sandwiched by the laminate sheet 13 and thermally welded is covered with the tab lead sealing material 1. Then, the heat-welded layer 16 of the laminate sheet 13 and the laminate adhesive layer 5 of the tab lead sealing material 1 are heat-welded.

  It is preferable that the resin component which comprises the heat welding layer 16 of the laminate sheet 13 is a polypropylene resin. When a resin other than the polypropylene-based resin is used, the compatibility with the laminate adhesive layer 5 of the tab lead sealing material 1 is poor, and sufficient adhesive strength cannot be obtained. As a result, liquid leakage may occur.

  The thermal welding of the tab lead sealing material 1 and the laminate sheet 13 is performed under the condition that the pressure applied to the heat welded portion 17 of the laminate sheet 13 is 0.6 to 1.0 MPa and the laminate adhesive layer 5 and the heat reached by the thermal welding. It is performed under the condition that the maximum value of the interface temperature with the weld layer 16 is not less than the melting point of the laminate adhesive layer 5 and not more than the melting point of the insulating layer 4.

  When the pressure applied to the heat welded portion 17 is less than 0.6 MPa, the appearance of a part of the heat welded portion 17 after the heat welded due to the effect of the step generated in the heat welded portion 17 due to the tab lead 6 being interposed. Wrinkles that become defective may occur. On the other hand, when the pressure applied to the heat welding part 17 is higher than 1.0 MPa, the deformation amount of the tab lead sealing material 1 increases, and a short circuit between the lead conductors (positive electrode and negative electrode) may occur.

  Further, when the maximum value of the interface temperature between the laminate adhesive layer 5 and the heat weld layer 16 that is reached by thermal welding is less than the melting point of the laminate adhesive layer 5, the welding becomes insufficient, which causes liquid leakage. On the other hand, when the maximum value of the interface temperature between the laminated adhesive layer 5 and the heat welding layer 16 reached by heat welding is higher than the melting point of the insulating layer 4, the tab lead sealing material 1 flows and leads conductors (positive electrode and negative electrode). ) May occur.

  When the tab lead sealing material 1 and the laminate sheet 13 are thermally welded, it is only necessary to pay attention only to the maximum value of the interface temperature between the laminate adhesive layer 5 and the heat welded layer 16 that is reached by the heat welding. It is not necessary to hold for a certain time. Therefore, by setting an appropriate heat source surface temperature and welding time, it is possible to reduce the tact time of heat welding. For example, if the heat source surface temperature is increased, the time required to reach the target temperature is shortened, so that the welding time can be shortened. However, in this case, the rate of temperature rise at the interface temperature between the laminate adhesive layer 5 and the heat-welded layer 16 is increased, and the range of the welding time is in the range from the melting point of the laminate adhesive layer 5 to the melting point of the insulating layer 4. Therefore, more accurate management of the welding time is required.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

(Example 1)
A tab lead sealing material 1 having a three-layer structure comprising the lead conductor adhesive layer 3, the insulating layer 4, and the laminate adhesive layer 5 shown in FIG. 1 was produced by a coextrusion inflation method. In this example, a polymer alloy of acid-modified polypropylene (melting point 135 ° C.) and polypropylene was used as the lead conductor adhesive layer 3. The insulating layer 4 was made of polypropylene having a melting point of 162 ° C. and a deflection temperature under load of 110 ° C., and the laminate adhesive layer was made of metallocene polypropylene having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C.

  Next, as shown in FIG. 2, the tab lead 6 was produced by sandwiching the lead conductor 2 with the tab lead sealing material 1. As the lead conductor 2, an Al strip (width 20 mm, thickness 0.2 mm) is used as the positive lead conductor, and a Ni-plated Cu strip (width 20 mm, thickness 0.2 mm) is used as the negative lead conductor. It was cut into a predetermined shape with respect to the direction. In order to minimize the influence of burrs on the occurrence of short circuits, the generation of burrs due to slits in each strip was suppressed, and burrs were used at 10 μm or less.

  Thereafter, the tab lead sealing material 1 cut into a predetermined shape was disposed so that the lead conductor adhesive layers 3 face each other, and the front and back surfaces of the lead conductor 2 and the lead conductor adhesive layer 3 were thermally welded. In the heat welding, the surface temperature of the heat source and the welding time were set so that the temperature at the interface between the lead conductor 2 and the lead conductor bonding layer 3 reached the melting point of the lead conductor bonding layer 3 under the pressure of 0.2 MPa. In this example, the heat source surface temperature was 220 ° C. and the welding time was 4 seconds.

  Subsequently, as shown in FIG. 3, the positive electrode lead conductor 11 was welded to the positive electrode lead conductor attachment portion 9 provided in the electrode laminate 8, and the negative electrode lead conductor 12 was welded to the negative electrode lead conductor attachment portion 10. As the laminate sheet 13, a sheet having a three-layer structure made of nylon / aluminum / polypropylene resin was used, and was drawn into a concave shape to accommodate the electrode laminate 8.

  Further, as shown in FIG. 4, after the electrode laminate 8 is stored in the laminate sheet 13, the three sides excluding the folded portion of the laminate sheet 13 are overlapped and heat-welded, and the lithium ion secondary battery 7 of this example is obtained. Produced. The thermal welding of the laminate sheet 13 is performed under the condition of a pressure of 0.8 MPa, the temperature at the interface between the laminate adhesive layer 5 of the tab lead sealing material 1 and the thermal weld layer 16 of the laminate sheet 13 (hereinafter referred to as the welding surface temperature). The surface temperature of the heat source and the welding time were set so as to reach a temperature higher than the melting point of the laminate adhesive layer 5. In this embodiment, the welding surface temperature is 130 ° C. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery 7 of this example.

(Example 2)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material 1. Further, polypropylene having a melting point of 162 ° C. and a deflection temperature under load of 110 ° C. was used as the insulating layer 4, and a metallocene polypropylene having a melting point of 135 ° C. and a deflection temperature under load of 80 ° C. was used as the laminate adhesive layer 5. Furthermore, the thermal welding of the laminate sheet 13 at the time of battery sealing was performed under the conditions of a pressure of 0.8 MPa and a welding surface temperature of 140 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery 7 of this example. Table 1 shows the structure of the tab lead sealing material 1 in the lithium ion secondary battery 7 of this example.

Example 3
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material 1. The insulating layer 4 was polypropylene having a melting point of 162 ° C. and a deflection temperature under load of 110 ° C., and the laminate adhesive layer 5 was a metallocene polypropylene having a melting point of 140 ° C. and a deflection temperature under load of 85 ° C. Furthermore, the thermal welding of the laminate sheet 13 at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 145 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery 7 of this example. Table 1 shows the structure of the tab lead sealing material 1 in the lithium ion secondary battery 7 of this example.

Example 4
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material 1. The insulating layer 4 was made of polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 100 ° C., and the laminate adhesive layer 5 was made of metallocene polypropylene having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C. Furthermore, the thermal welding of the laminate sheet 13 at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 130 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery 7 of this example. Table 1 shows the structure of the tab lead sealing material 1 in the lithium ion secondary battery 7 of this example.

(Example 5)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material 1. Further, a metallocene polypropylene having a melting point of 147 ° C. and a deflection temperature under load of 101 ° C. was used as the insulating layer 4, and a metallocene polypropylene having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C. was used as the laminate adhesive layer 5. Furthermore, the thermal welding of the laminate sheet 13 at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 130 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery 7 of this example. Table 1 shows the structure of the tab lead sealing material 1 in the lithium ion secondary battery 7 of this example.

(Example 6)
As the lead conductor adhesive layer 3 of the tab lead sealing material 1, a polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 130 ° C. was used as the lead conductor adhesive layer 3. The insulating layer 4 was made of polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 110 ° C., and the laminate adhesive layer 5 was made of metallocene polypropylene having a melting point of 135 ° C. and a deflection temperature under load of 70 ° C. Furthermore, the thermal welding of the laminate sheet 13 at the time of battery sealing was performed under the conditions of a pressure of 0.8 MPa and a welding surface temperature of 140 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery 7 of this example. Table 1 shows the structure of the tab lead sealing material 1 in the lithium ion secondary battery 7 of this example.

(Example 7)
As the lead conductor adhesive layer 3 of the tab lead sealing material 1, a polymer alloy of acid-modified polypropylene having a melting point of 130 ° C. and polypropylene was used. Further, polypropylene having a melting point of 160 ° C. and a deflection temperature under load of 110 ° C. was used as the insulating layer 4, and a metallocene polypropylene having a melting point of 135 ° C. and a deflection temperature under load of 80 ° C. was used as the laminate adhesive layer 5. Furthermore, the thermal welding of the laminate sheet 13 at the time of battery sealing was performed under the conditions of a pressure of 0.8 MPa and a welding surface temperature of 140 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this example.

(Example 8)
As the lead conductor adhesive layer 3 of the tab lead sealing material 1, a polymer alloy of acid-modified polypropylene having a melting point of 130 ° C. and polypropylene was used. The insulating layer 4 was made of polypropylene having a melting point of 160 ° C. and a deflection temperature under load of 110 ° C., and the laminate adhesive layer 5 was made of metallocene polypropylene having a melting point of 140 ° C. and a deflection temperature under load of 85 ° C. Furthermore, the thermal welding of the laminate sheet 13 at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 145 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery 7 of this example.

Example 9
As the lead conductor adhesive layer 3 of the tab lead sealing material 1, a polymer alloy of acid-modified polypropylene having a melting point of 130 ° C. and polypropylene was used. The insulating layer 4 was made of polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 100 ° C., and the laminate adhesive layer 5 was made of metallocene polypropylene having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C. Furthermore, the thermal welding of the laminate sheet 13 at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 135 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery 7 of this example.

(Example 10)
As the lead conductor adhesive layer 3 of the tab lead sealing material 1, a polymer alloy of acid-modified polypropylene having a melting point of 130 ° C. and polypropylene was used. Further, a metallocene polypropylene having a melting point of 147 ° C. and a deflection temperature under load of 101 ° C. was used as the insulating layer 4, and a metallocene polypropylene having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C. was used as the laminate adhesive layer 5. Furthermore, the thermal welding of the laminate sheet 13 at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 130 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery 7 of this example.

(Comparative Example 1)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material. Further, polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 100 ° C. was used as the insulating layer 4, and an ethylene-propylene random copolymer having a melting point of 132 ° C. and a deflection temperature under load of 58 ° C. was used as the laminate adhesive layer 5. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 137 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

(Comparative Example 2)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material. Further, polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 100 ° C. was used as the insulating layer 4, and an ethylene-propylene random copolymer having a melting point of 135 ° C. and a deflection temperature under load of 60 ° C. was used as the laminate adhesive layer 5. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 140 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

(Comparative Example 3)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material. Further, polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 100 ° C. was used as the insulating layer 4, and an ethylene-propylene random copolymer having a melting point of 146 ° C. and a deflection temperature under load of 80 ° C. was used as the laminate adhesive layer 5. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 150 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

(Comparative Example 4)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material. Further, polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 100 ° C. was used as the insulating layer 4, and an ethylene-propylene random copolymer having a melting point of 142 ° C. and a deflection temperature under load of 75 ° C. was used as the laminate adhesive layer 5. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 145 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

(Comparative Example 5)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material. Further, an ethylene-propylene random copolymer having a melting point of 142 ° C. and a deflection temperature under load of 75 ° C. is used as the insulating layer 4, and an ethylene-propylene random copolymer having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C. is used as the laminate adhesive layer 5. Was used. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 130 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

(Comparative Example 6)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material. Further, an ethylene-propylene random copolymer having a melting point of 146 ° C. and a deflection temperature under load of 80 ° C. was used as the insulating layer 4, and a metallocene polypropylene having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C. was used as the laminate adhesive layer 5. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 130 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

(Comparative Example 7)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material. Further, an ethylene-propylene random copolymer having a melting point of 150 ° C. and a deflection temperature under load of 88 ° C. was used as the insulating layer 4, and a metallocene polypropylene having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C. was used as the laminate adhesive layer 5. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 130 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

(Comparative Example 8)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material. Further, a metallocene polypropylene having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C. was used as the insulating layer 4, and a metallocene polypropylene having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C. was used as the laminate adhesive layer 5. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 130 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

(Comparative Example 9)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material. The insulating layer 4 was made of polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 100 ° C., and the laminate adhesive layer 5 was made of polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 100 ° C. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 165 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

(Comparative Example 10)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material. Further, a metallocene polypropylene having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C. was used as the insulating layer 4, and a polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 100 ° C. was used as the laminate adhesive layer 5. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 165 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

(Comparative Example 11)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material. Further, a metallocene polypropylene having a melting point of 135 ° C. and a deflection temperature under load of 80 ° C. was used as the insulating layer 4, and a polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 100 ° C. was used as the laminate adhesive layer 5. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 165 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

(Comparative Example 12)
As the lead conductor adhesive layer 3 of the tab lead sealing material, a polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 147 ° C. was used. The insulating layer 4 was made of polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 100 ° C., and the laminate adhesive layer 5 was made of metallocene polypropylene having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 130 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

(Comparative Example 13)
A polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 150 ° C. was used as the lead conductor adhesive layer 3 of the tab lead sealing material. The insulating layer 4 was made of polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 100 ° C., and the laminate adhesive layer 5 was made of metallocene polypropylene having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 130 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

(Comparative Example 14)
As the lead conductor adhesive layer 3 of the tab lead sealing material, acid-modified polypropylene having a melting point of 135 ° C. was used. The insulating layer 4 was made of polypropylene having a melting point of 158 ° C. and a deflection temperature under load of 100 ° C., and the laminate adhesive layer 5 was made of metallocene polypropylene having a melting point of 125 ° C. and a deflection temperature under load of 70 ° C. Furthermore, the thermal welding of the laminate sheet at the time of battery sealing was performed under conditions of a pressure of 0.8 MPa and a welding surface temperature of 130 ° C. Except for this, the same operation as in Example 1 was repeated to produce a lithium ion secondary battery of this comparative example. Table 1 shows the structure of the tab lead sealing material in the lithium ion secondary battery of this comparative example.

  Five lithium ion secondary batteries obtained in Examples 1 to 10 and Comparative Examples 1 to 14 were produced, and the insulating properties, adhesion to lead conductors, and heat resistance were evaluated.

  The insulation characteristics were evaluated by using a tester to evaluate the presence or absence of a short circuit between the aluminum layer of the laminate sheet 13 and the lead conductor (positive electrode and negative electrode). The obtained results are also shown in Table 1. The heat resistance was evaluated by a 180 ° peel test in a state where the sample was heated to 70 ° C.

  In FIG. 5, the test piece cut out from the produced lithium ion secondary battery and the tensile direction are shown. The test piece was prepared by cutting the laminate sheet 13 welded to the tab lead to the same 20 mm width as the lead conductor 2. The test piece was pulled by chucking the laminate sheet 13 and the lead conductor 2. The measurement was performed using an autograph with a tensile speed of 100 mm / min. The obtained results are also shown in Table 1. When the peel strength obtained is less than 2 N / mm, there is a concern that when the temperature inside the battery rises due to an internal short circuit or the like and the internal pressure rises, the sealing material peels off from the lead conductor and causes liquid leakage. It was judged that there was a problem (indicated by x in Table 1).

  From Table 1, for the tab lead sealing material, a polymer alloy of acid-modified polypropylene and polypropylene having a melting point of 135 ° C. or lower is used as the lead conductor adhesive layer 3, and a polypropylene having a melting point of 145 ° C. or higher and a deflection temperature under load of 100 ° C. or higher is used as the insulating layer 4. Further, in Examples 1 to 6 in which a metallocene polypropylene having a melting point of 140 ° C. or lower and a load deflection temperature of 70 ° C. or higher is used as the laminate adhesive layer 5, a short circuit between the aluminum layer 15 of the laminate sheet 13 and the lead conductor 2 is prevented. And it has been found that the peel strength in a high temperature environment is maintained.

  As described above, by using the tab lead sealing material 1 belonging to the scope of the present invention, it is possible to provide an excellent lithium ion secondary battery that satisfies all of the high reliability of sealing, insulating characteristics, and heat resistance. .

  On the other hand, from Table 1, as in Comparative Examples 1 and 2, when the deflection temperature under load of the laminate adhesive layer 5 was less than 70 ° C., the short circuit between the aluminum layer 15 of the laminate sheet 13 and the lead conductor 2 did not occur. However, the peel strength was greatly reduced by the softening of the resin in a high temperature environment.

  Further, as in Comparative Examples 3 and 4, when the melting point of the laminate adhesive layer 5 is larger than 140 ° C., the difference in melting point between the laminate adhesive layer 5 and the insulating layer 4 is maintained, although the peel strength is maintained in a high temperature environment. As a result of the decrease, a short circuit between the aluminum layer 15 of the laminate sheet 13 and the lead conductor 2 occurred.

  Further, as in Comparative Example 5, when the melting point of the insulating layer 4 is less than 145 ° C., the difference in melting point between the laminate adhesive layer 5 and the insulating layer 4 is reduced, so that the aluminum layer 15 of the laminate sheet 13 and the lead A short circuit with the conductor 2 occurred.

  Further, as in Comparative Examples 6 and 7, when the deflection temperature under load of the insulating layer 4 is less than 100 ° C., deformation of the resin due to heat and pressure during heat welding increases, and the aluminum layer 15 of the laminate sheet 13 A part of the short circuit with the lead conductor 2 occurred.

  Further, as in Comparative Examples 8 and 9, when the same kind of resin is used for the laminate adhesive layer 5 and the insulating layer 4, the difference in melting point between the laminate adhesive layer and the insulating layer 4 is eliminated. A short circuit between the aluminum layer 15 and the lead conductor 2 occurred.

  Further, as in Comparative Examples 10 and 11, when a high melting point resin is used for the laminate adhesive layer 5 and a low melting point resin is used for the insulating layer 4, the difference in melting point between the laminate adhesive layer 5 and the insulating layer 4 increases. A short circuit between the aluminum layer 15 of the laminate sheet 13 and the lead conductor 2 occurred because it is necessary to perform heat welding under the condition that the high melting point laminated adhesive layer melts.

  Further, as in Comparative Examples 12 and 13, when a polymer alloy of acid-modified polypropylene and polypropylene having a melting point higher than 135 ° C. is used as the lead conductor adhesive layer 3, the lead conductor 2 and the lead conductor adhesive layer 3 The initial adhesive strength was weakened, and the peel strength in a high temperature environment was reduced.

  In addition, when acid-modified polypropylene is used as it is as the lead conductor adhesive layer 3 as in Comparative Example 14, the adhesive force at the interface between the lead conductor adhesive layer 3 and the insulating layer 4 becomes weak, and peeling in a high temperature environment The strength decreased.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiments and examples. However, the present invention is not limited to the above-described embodiments and examples, and does not depart from the spirit of the invention. It goes without saying that various changes can be made.

  The present invention can be applied to a tab lead sealing material for a lithium ion secondary battery, a tab lead sandwiching a lead conductor with the tab lead sealing material, and a laminated lithium ion secondary battery using the tab lead sealing material. it can.

DESCRIPTION OF SYMBOLS 1 Tab lead sealing material 2 Lead conductor 3 Lead conductor adhesive layer 4 Insulating layer 5 Laminate adhesive layer 6 Tab lead 7 Lithium ion secondary battery 8 Electrode laminated body 9 Positive electrode lead conductor attachment part 10 Negative electrode lead conductor attachment part 11 Positive electrode lead conductor 12 Negative electrode Lead conductor 13 Laminate sheet 14 Base material layer 15 Aluminum layer 16 Heat welding layer 17 Heat welding portion

Claims (13)

A tab lead sealing material for sealing a tab lead of a laminated lithium ion secondary battery,
Having a three-layer structure comprising a co-extruded laminate adhesive layer, an insulating layer and a lead conductor adhesive layer;
The laminate adhesive layer is made of a polypropylene resin having a melting point of 140 ° C. or lower and a deflection temperature under load of 70 ° C. or higher.
The insulating layer is made of a polypropylene resin having a melting point of 145 ° C. or higher and a deflection temperature under load of 100 ° C. or higher.
The lead conductor adhesive layer is a tab lead sealing material comprising a polymer alloy of an acid-modified polypropylene having a melting point of 140 ° C. or lower and a polypropylene resin. In the tab lead sealing material according to claim 1,
The laminate adhesive layer is a tab lead sealing material made of a random copolymer of ethylene and propylene polymerized by a metallocene catalyst. In the tab lead sealing material according to claim 1,
The acid-modified polypropylene is a tab lead sealing material made of a polypropylene resin grafted with an unsaturated carboxylic acid. In the tab lead sealing material according to claim 3,
The amount of grafting of the unsaturated carboxylic acid is 3 to 10% by mass with respect to the acid-modified polypropylene, the tab lead sealing material. In the tab lead sealing material according to claim 3,
The tab lead sealing material, wherein the ratio of the unsaturated carboxylic acid to the entire polymer alloy is 0.1 to 2.0 mass%. In the tab lead sealing material according to claim 3,
The tab lead sealing material, wherein the unsaturated carboxylic acid is maleic anhydride. In the tab lead sealing material according to claim 1,
The acid-modified polypropylene has a melt flow rate of 10 to 900 g / 10 min. It is a tab lead of a laminate type lithium ion secondary battery,
A lead conductor and a tab lead sealing material thermally welded to both sides of the lead conductor;
Have
The tab lead sealing material has a three-layer structure comprising a coextruded laminate adhesive layer, an insulating layer and a lead conductor adhesive layer,
The laminate adhesive layer is made of a polypropylene resin having a melting point of 140 ° C. or lower and a deflection temperature under load of 70 ° C. or higher.
The insulating layer is made of a polypropylene resin having a melting point of 145 ° C. or higher and a deflection temperature under load of 100 ° C. or higher.
The lead conductor adhesive layer is a tab lead made of a polymer alloy of an acid-modified polypropylene having a melting point of 140 ° C. or less and a polypropylene resin. The tab lead according to claim 8,
The thermal welding between the tab lead sealing material and the lead conductor is performed under the condition that the pressure applied to the tab lead sealing material is 0.06 to 0.25 MPa. A tab lead which is formed under conditions where the maximum value of the interface temperature with the conductor is in the range of the melting point of the polymer alloy to + 10 ° C. Laminate sheet,
An electrode laminate that is housed inside the laminate sheet and in which positive and negative plates are alternately laminated via separators;
A positive electrode lead conductor electrically connected to the positive electrode plate via a positive electrode lead conductor attachment portion, one end exposed to the outside of the laminate sheet;
A negative electrode lead conductor electrically connected to the negative electrode plate via a negative electrode lead conductor attachment portion, one end of which is exposed to the outside of the laminate sheet; and
Have
Each of the positive electrode lead conductor and the negative electrode lead conductor is covered with a tab lead sealing material between the laminate sheet and thermally welded.
The tab lead sealing material has a three-layer structure comprising a coextruded laminate adhesive layer, an insulating layer and a lead conductor adhesive layer,
The laminate adhesive layer is made of a polypropylene resin having a melting point of 140 ° C. or lower and a deflection temperature under load of 70 ° C. or higher.
The insulating layer is made of a polypropylene resin having a melting point of 145 ° C. or higher and a deflection temperature under load of 100 ° C. or higher.
The lead conductor adhesive layer is a laminated lithium ion secondary battery made of a polymer alloy of an acid-modified polypropylene having a melting point of 140 ° C. or less and a polypropylene resin. The laminate type lithium ion secondary battery according to claim 10,
The laminate sheet has a three-layer structure composed of a base material layer, an aluminum layer, and a heat welding layer,
A laminate type lithium ion secondary battery in which the laminate adhesive layer of the tab lead sealing material and the heat welding layer of the laminate sheet are thermally welded to each other. The laminated lithium ion secondary battery according to claim 11,
The thermal welding of the tab lead sealing material and the laminate sheet is performed by the tab lead sealing material that is reached by the thermal welding under a pressure of 0.6 to 1.0 MPa applied to the thermal welding portion of the laminate sheet. It is performed under the condition that the maximum value of the interface temperature between the laminate adhesive layer and the heat-bonding layer of the laminate sheet is not less than the melting point of the laminate adhesive layer and not more than the melting point of the insulating layer of the tab lead sealing material. Laminated lithium ion secondary battery. The laminated lithium ion secondary battery according to claim 11,
The laminate type lithium ion secondary battery, wherein the resin component constituting the heat-welded layer of the laminate sheet is a polypropylene resin.

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