NONAQUEOUS ELECTROLYTE SECONDARY BATTTERY POROUS LAYER

Abstract

As a nonaqueous electrolyte secondary battery porous layer that is excellent in durability with respect to charge-discharge cycles, provided is a nonaqueous electrolyte secondary battery porous layer including a resin which has an amide bond and which contains a component that is to be eluted into N-methylpyrrolidone. A contained amount of the component that is to be eluted into N-methylpyrrolidone is not less than 6.0% by weight and not more than 25.0% by weight relative to a total weight of the resin having the amide bond.

Claims

1. A nonaqueous electrolyte secondary battery porous layer comprising at least one type of a resin having an amide bond, the resin having the amide bond containing a component that is to be eluted into N-methylpyrrolidone, and a contained amount of the component that is to be eluted into N-methylpyrrolidone being not less than 6.0% by weight and not more than 25.0% by weight relative to a total weight of the resin having the amide bond, where the contained amount of the component that is to be eluted into N-methylpyrrolidone is measured by carrying out extraction with respect to the nonaqueous electrolyte secondary battery porous layer using N-methylpyrrolidone.

2. The nonaqueous electrolyte secondary battery porous layer as set forth in claim 1, wherein: at least one type of the resin having the amide bond is a block copolymer including a block A containing, as a main component, units each represented by Formula (1) below, and a block B containing, as a main component, units each represented by Formula (2) below.
—(NH—Ar.sup.1—NHCO—Ar.sup.2—CO—)—  Formula (1)
—(NH—Ar.sup.3—NHCO—Ar.sup.4—CO)—  Formula (2) where: Ar.sup.1, Ar.sup.2, Ar.sup.3, and Ar.sup.4 may each vary from unit to unit; Ar.sup.1, Ar.sup.2, Ar.sup.3, and Ar.sup.4 are each independently a divalent group having one or more aromatic rings; not less than 50% of all Ar.sup.1 each have a structure in which two aromatic rings are connected by a sulfonyl bond; not more than 50% of all Ar.sup.3 each have a structure in which two aromatic rings are connected by a sulfonyl bond; and 10% to 70% of all Ar.sup.1 and Ar.sup.3 each have a structure in which two aromatic rings are connected by a sulfonyl bond.

3. The nonaqueous electrolyte secondary battery porous layer as set forth in claim 1, further comprising a filler, a contained amount of the filler being not less than 20% by weight and not more than 90% by weight relative to a total weight of the nonaqueous electrolyte secondary battery porous layer.

4. A nonaqueous electrolyte secondary battery laminated separator, wherein a nonaqueous electrolyte secondary battery porous layer recited in claim 1 is formed on one surface or both surfaces of a polyolefin porous film.

5. A nonaqueous electrolyte secondary battery member, comprising a positive electrode, a nonaqueous electrolyte secondary battery porous layer recited in claim 1, and a negative electrode which are disposed in this order.

6. A nonaqueous electrolyte secondary battery comprising a nonaqueous electrolyte secondary battery porous layer recited in claim 1.

7. A nonaqueous electrolyte secondary battery member, comprising a positive electrode, a nonaqueous electrolyte secondary battery laminated separator recited in claim 4, and a negative electrode which are disposed in this order.

8. A nonaqueous electrolyte secondary battery comprising a nonaqueous electrolyte secondary battery laminated separator recited in claim 4.

Description

EXAMPLE 1

[0181] <Preparation of Composition>

[0182] A composition was prepared by a method which included the following steps (a) through (g).

[0183] (a) A 5-L separable flask having a stirring blade, a thermometer, a nitrogen incurrent canal, and a powder addition port was sufficiently dried.

[0184] (b) 4217 g of NMP was introduced into the flask. Further, 324.22 g of calcium chloride (which had been dried at 200° C. for 2 hours) was added, and a resulting mixture was heated to 100° C. The calcium chloride was completely dissolved to obtain a solution of calcium chloride. Here, in the solution of calcium chloride, a concentration of calcium chloride was 7.14% by weight, and a water content was adjusted to be 500 ppm.

[0185] (c) To the solution of calcium chloride, 151.559 g of 4,4′-diaminodiphenylsulfone (DDS) was added while the temperature was maintained at 100° C., and the DDS was completely dissolved to obtain a solution A(1).

[0186] (d) The resulting solution A(1) was cooled to 40° C. After that, to the solution A(1) which had been cooled, a total of 123.304 g of terephthalic acid dichloride (TPC) was added in three separate portions while the temperature was maintained at 40±2° C. A reaction was then caused to occur for 1 hour, and a reaction solution A(1) was obtained. In the reaction solution A(1), a block A(1) which was constituted by poly(4,4′-diphenylsulfonyl terephthalamide) was prepared.

[0187] (e) To the reaction solution A(1) obtained, 66.003 g of paraphenylenediamine (PPD) was added, and completely dissolved over 1 hour to obtain a solution B(1).

[0188] (f) To the solution B(1), a total of 123.049 g of TPC was added in three separate portions while the temperature was maintained at 40±2° C. A reaction was then caused to occur for 1.5 hours, and a reaction solution B(1) was obtained. In the reaction solution B(1), blocks B(1), each of which was constituted by poly(paraphenylene terephthalamide), extended on both sides of the block A(1).

[0189] (g) While the temperature of the reaction solution B(1) was maintained at 40±2° C., the solution was matured for 1 hour. After that, the solution was stirred for 1 hour under reduced pressure, and air bubbles were removed. As a result, a solution was obtained which contained a block copolymer (1) in which the block A(1) accounted for 50% of the entirety of a molecule and the block B(1) accounted for the remaining 50% of the entirety of the molecule. The block copolymer (1) is a resin having an amide bond.

[0190] Note that, in Example 1, the weight of the block A(1) relative to the weight of the reaction solution A(1) was 4.82% by weight.

[0191] In another flask different from the separable flask, 0.5 L of ion-exchange water was introduced. Further, 50 mL of the solution containing the block copolymer (1) was weighed and collected. After that, 50 mL of the collected solution containing the block copolymer (1) was added to said another flask, and the block copolymer (1) was deposited. The deposited block copolymer (1) was separated by a filtration operation to obtain a composition (1) which was constituted by 3.75 g of the block copolymer (1). Note that, in the filtration operation, the solution remained after the deposition of the block copolymer (1) was filtered once, and then 100 mL of ion-exchange water was added to the resulting deposit and filtration was carried out again. That is, filtration was carried out twice.

[0192] 0.50 g of the obtained composition (1), i.e., the block copolymer (1) was weighed and collected, and with use of the collected 0.50 g of the block copolymer (1), a contained amount of a component that is contained in the composition and that is to be eluted into NMP was measured by the above described method.

[0193] <Preparation of Porous Layer and Laminated Separator>

[0194] With use of a remaining solution of the solution containing the block copolymer (1) which had not been used for measurement of the contained amount of the component that is to be eluted into NMP, a porous layer and a laminated separator were prepared by a method described below.

[0195] To 4000 g of the solution containing the block copolymer (1), 8.56 L of NMP was added, and a solution in which the block copolymer (1) was dissolved and dispersed was obtained. To the solution in which the block copolymer (1) had been dissolved and dispersed, 300.0 g of aluminum oxide (average particle diameter: 0.013 μm) was added. A resulting mixture was uniformly dispersed with use of a pressure type disperser to prepare a coating solution. A solid content concentration of the coating solution was 5% by weight.

[0196] The coating solution was applied to a polyethylene porous film (thickness: 10 μm, weight per unit area: 5.6 g/m.sup.2), and the polyethylene porous film to which the coating solution was applied was treated in an oven at 50° C. and a humidity of 70% for 2 minutes so that a porous layer was formed. After that, the resulting polyethylene porous film and porous layer were washed with water and dried to obtain a laminated separator including the porous layer.

[0197] Physical property values of the porous layer and the laminated separator were measured by the above described methods. Moreover, with use of the laminated separator, a short circuit time and a contained amount of a component that is contained in the porous layer and that is to be eluted into NMP were measured by the above described method.

EXAMPLE 2

[0198] A reaction solution A(2), a solution containing a block copolymer (2) in which the block A(2) accounted for 50% of the entirety of a molecule and the block B(2) accounted for the remaining 50% of the entirety of the molecule, and a composition (2) constituted by 3.5 g of the block copolymer (2) were obtained in a manner similar to that in Example 1, except that the amount of DDS used in the step (c) was changed to 140.659 g, the total amount of TPC used in each of the steps (d) and (f) was changed to 227.942 g, and the amount of PPD used in the step (f) was changed to 61.259 g. Note that, in

[0199] Example 2, the weight of the block A(2) relative to the weight of the reaction solution A(2) was 4.48% by weight.

[0200] A contained amount of a component that is contained in the composition and that is to be eluted into NMP was measured in a manner similar to that in Example 1, except that the composition (2) was used instead of the composition (1). A porous layer and a laminated separator were prepared, physical property values of the porous layer and the laminated separator were measured, a short circuit time was measured, and a contained amount of a component that is contained in the porous layer and that is to be eluted into NMP were measured in a manner similar to that in Example 1, except that a solution containing the block copolymer (2) was used instead of the solution containing the block copolymer (1), and that the amount of NMP used was changed to 6.83 L and the amount of aluminum oxide used was changed to 280.0 g.

EXAMPLE 3

[0201] A reaction solution A(3), a solution containing a block copolymer (3) in which the block A(3) accounted for 50% of the entirety of a molecule and the block B(3) accounted for the remaining 50% of the entirety of the molecule, and a composition (3) constituted by 3.5 g of the block copolymer (3) were obtained in a manner similar to that in Example 1, except that the amount of NMP used in the step (a) was changed to 4177 g, the amount of calcium chloride used was changed to 366.29 g, the amount of DDS used in the step (c) was changed to 140.853 g, the total amount of TPC used in each of the steps (d) and (f) was changed to 227.615 g, the amount of PPD used in the step (f) was changed to 61.344 g, the temperature of the solution A(3) in the step (d) was changed to 20° C., the temperature of the solution B(3) in the step (g) was changed to 20° C., and the water content in the step (b) was adjusted to 400 ppm. Note that, in Example 3, the weight of the block A(3) relative to the weight of the reaction solution A(3) was 4.48% by weight.

[0202] A contained amount of a component that is contained in the composition and that is to be eluted into NMP was measured in a manner similar to that in Example 1, except that the composition (3) was used instead of the composition (1). A porous layer and a laminated separator were prepared, physical property values of the porous layer and the laminated separator were measured, a short circuit time was measured, and a contained amount of a component that is contained in the porous layer and that is to be eluted into NMP were measured in a manner similar to that in Example 1, except that a solution containing the block copolymer (3) was used instead of the solution containing the block copolymer (1), and that the amount of NMP used was changed to 6.83 L and the amount of aluminum oxide used was changed to 280.0 g.

EXAMPLE 4

[0203] A reaction solution A(4), a solution containing a block copolymer (4) in which the block A(4) accounted for 50% of the entirety of a molecule and the block B(4) accounted for the remaining 50% of the entirety of the molecule, and a composition (4) constituted by 3.5 g of the block copolymer (4) were obtained in a manner similar to that in Example 1, except that the amount of NMP used in the step (a) was changed to 4177 g, the amount of calcium chloride used was changed to 366.29 g, the amount of DDS used in the step (c) was changed to 141.119 g, the total amount of TPC used in each of the steps (d) and (f) was changed to 226.911 g, the amount of PPD used in the step (f) was changed to 61.460 g, the temperature of the solution A(4) in the step (d) was changed to 20° C., the temperature of the solution B(4) in the step (g) was changed to 20° C., and the water content in the step (b) was adjusted to 300 ppm. Note that, in Example 4, the weight of the block A(4) relative to the weight of the reaction solution A(4) was 4.48% by weight.

[0204] A contained amount of a component that is contained in the composition and that is to be eluted into NMP was measured in a manner similar to that in Example 1, except that the composition (4) was used instead of the composition (1). A porous layer and a laminated separator were prepared, physical property values of the porous layer and the laminated separator were measured, a short circuit time was measured, and a contained amount of a component that is contained in the porous layer and that is to be eluted into NMP were measured in a manner similar to that in Example 1, except that a solution containing the block copolymer (4) was used instead of the solution containing the block copolymer (1), and that the amount of NMP used was changed to 6.83 L and the amount of aluminum oxide used was changed to 280.0 g.

EXAMPLE 5

[0205] eaction solution A(5), a solution containing a block copolymer (5) in which the block A(5) accounted for 50% of the entirety of a molecule and the block B(5) accounted for the remaining 50% of the entirety of the molecule, and a composition (5) constituted by 3.5 g of the block copolymer (5) were obtained in a manner similar to that in Example 1, except that the amount of NMP used in the step (a) was changed to 4177 g, the amount of calcium chloride used was changed to 366.29 g, the amount of DDS used in the step (c) was changed to 141.119 g, the total amount of TPC used in each of the steps (d) and (f) was changed to 226.911 g, the amount of PPD used in the step (f) was changed to 61.460 g, the temperature of the solution A(5) in the step (d) was changed to 20° C., the temperature of the solution B(5) in the step (g) was changed to 20° C., and the water content in the step (b) was adjusted to 730 ppm. Note that, in Example 5, the weight of the block A(5) relative to the weight of the reaction solution A(5) was 4.48% by weight.

[0206] A contained amount of a component that is contained in the composition and that is to be eluted into NMP was measured in a manner similar to that in Example 1, except that the composition (5) was used instead of the composition (1). A porous layer and a laminated separator were prepared, physical property values of the porous layer and the laminated separator were measured, a short circuit time was measured, and a contained amount of a component that is contained in the porous layer and that is to be eluted into NMP were measured in a manner similar to that in Example 1, except that a solution containing the block copolymer (5) was used instead of the solution containing the block copolymer (1), and that the amount of NMP used was changed to 6.83 L and the amount of aluminum oxide used was changed to 280.0 g.

EXAMPLE 6

[0207] A reaction solution A(6), a solution containing a block copolymer (6) in which the block A(6) accounted for 50% of the entirety of a molecule and the block B(6) accounted for the remaining 50% of the entirety of the molecule, and a composition (6) constituted by 3.5 g of the block copolymer (6) were obtained in a manner similar to that in Example 1, except that the amount of NMP used in the step (a) was changed to 4177 g, the amount of calcium chloride used was changed to 366.29 g, the amount of DDS used in the step (c) was changed to 141.119 g, the total amount of TPC used in each of the steps (d) and (f) was changed to 226.911 g, the amount of PPD used in the step (f) was changed to 61.460 g, the temperature of the solution A(6) in the step (d) was changed to 20° C., the temperature of the solution B(6) in the step (g) was changed to 20° C., and the water content in the step (b) was adjusted to 1000 ppm. Note that, in Example 6, the weight of the block A(6) relative to the weight of the reaction solution A(6) was 4.48% by weight.

[0208] A contained amount of a component that is contained in the composition and that is to be eluted into NMP was measured in a manner similar to that in Example 1, except that the composition (6) was used instead of the composition (1). A porous layer and a laminated separator were prepared, physical property values of the porous layer and the laminated separator were measured, a short circuit time was measured, and a contained amount of a component that is contained in the porous layer and that is to be eluted into NMP were measured in a manner similar to that in Example 1, except that a solution containing the block copolymer (6) was used instead of the solution containing the block copolymer (1), and that the amount of NMP used was changed to 6.83 L and the amount of aluminum oxide used was changed to 280.0 g.

EXAMPLE 7

[0209] A reaction solution A(7), a solution containing a block copolymer (7) in which the block A(7) accounted for 20% of the entirety of a molecule and the block B(7) accounted for the remaining 80% of the entirety of the molecule, and a composition (7) constituted by 3.0 g of the block copolymer (7) were obtained in a manner similar to that in Example 1, except that the amount of NMP used in the step (a) was changed to 4177 g, the amount of calcium chloride used was changed to 366.29 g, the amount of DDS used in the step (c) was changed to 79.159 g, the total amount of TPC used in each of the steps (d) and (f) was changed to 210.978 g, the amount of PPD used in the step (f) was changed to 80.443 g, the temperature of the solution A(7) in the step (d) was changed to 20° C., the temperature of the solution B(7) in the step (g) was changed to 20° C., and the water content in the step (b) was adjusted to 300 ppm. Note that, in Example 7, the weight of the block A(7) relative to the weight of the reaction solution A(7) was 2.55% by weight.

[0210] A contained amount of a component that is contained in the composition and that is to be eluted into NMP was measured in a manner similar to that in Example 1, except that the composition (7) was used instead of the composition (1). A porous layer and a laminated separator were prepared, physical property values of the porous layer and the laminated separator were measured, a short circuit time was measured, and a contained amount of a component that is contained in the porous layer and that is to be eluted into NMP were measured in a manner similar to that in Example 1, except that a solution containing the block copolymer (7) was used instead of the solution containing the block copolymer (1), and that the amount of NMP used was changed to 6.33 L and the amount of aluminum oxide used was changed to 240.0 g.

COMPARATIVE EXAMPLE 1

[0211] <Preparation of Composition>

[0212] A solution containing a comparative polymer (1) was obtained by a method which included the following steps (a′) through (e′).

[0213] (a′) A 5-L separable flask having a stirring blade, a thermometer, a nitrogen incurrent canal, and a powder addition port was sufficiently dried.

[0214] (b′) 4280 g of NMP was introduced into the flask. Further, 329.08 g of calcium chloride (which had been dried at 200° C. for 2 hours) was added, and a resulting mixture was heated to 100° C. The calcium chloride was completely dissolved to obtain a solution of calcium chloride. Here, in the solution of calcium chloride, a concentration of calcium chloride was 7.14% by weight, and a water content was adjusted to be 500 ppm.

[0215] (c′) To the solution of calcium chloride, 138.932 g of PPD was added while the temperature was maintained at 30±2° C., and the PPD was completely dissolved to obtain a comparative solution A.

[0216] (d′) The resulting comparative solution A was cooled to 20° C. After that, to the comparative solution A which had been cooled, a total of 251.499 g of terephthalic acid dichloride (TPC) was added in three separate portions while the temperature was maintained at 20±2° C. A reaction was then caused to occur for 1 hour, and a comparative reaction solution A was obtained.

[0217] (e′) While the temperature of the comparative reaction solution A was maintained at 20±2° C., the solution was matured for 1 hour. After that, the solution was stirred for 1 hour under reduced pressure, and air bubbles were removed. As a result, a solution containing a comparative polymer (1) constituted by poly(paraphenylene terephthalamide) was obtained. The comparative polymer (1) is a resin having an amide bond.

[0218] In a flask, 0.5 L of ion-exchange water was introduced. Further, 50 mL of the solution containing the comparative polymer (1) was weighed and collected. After that, 50 mL of the collected solution containing the comparative polymer (1) was added to the flask, and the comparative polymer (1) was deposited. The deposited comparative polymer (1) was separated by a filtration operation to obtain a comparative composition (1) which was constituted by 3.0 g of the comparative polymer (1). Note that, in the filtration operation, the solution remained after the deposition of the comparative polymer (1) was filtered once, and then 100 mL of ion-exchange water was added to the resulting deposit containing the cyclic component and filtration was carried out again. That is, filtration was carried out twice.

[0219] A contained amount of a component that is contained in the composition and that is to be eluted into NMP was measured in a manner similar to that in Example 1, except that the comparative composition (1) was used instead of the composition (1). A porous layer and a laminated separator were prepared, physical property values of the porous layer and the laminated separator were measured, a short circuit time was measured, and a contained amount of a component that is contained in the porous layer and that is to be eluted into NMP were measured in a manner similar to that in

[0220] Example 1, except that a solution containing the comparative polymer (1) was used instead of the solution containing the block copolymer (1), and that the amount of NMP used was changed to 6.33 L and the amount of aluminum oxide used was changed to 240.0 g.

[0221] Table 1 below shows the contained amount of the component that is contained in the composition and that is to be eluted into NMP, the physical property values of the porous layer and the laminated separator, and the short circuit time which were measured in each of Examples 1 through 7 and Comparative Example 1.

TABLE-US-00001 TABLE 1 Laminated Composition Nonaqueous Porous layer separator Contained amount of electrolyte Weight per Air Weight per component that is to secondary battery Thickness unit area permeability unit area be eluted into NMP Short circuit time [μm] [g/m.sup.2] [s/100 cc] [g/m.sup.2] [% by weight] [number of cycles] Example 1 12.9 1.8 288 7.88 18.7 201 Example 2 12.6 1.7 274 7.75 18.8 173 Example 3 12.5 1.7 268 7.84 11.7 189 Example 4 12.6 1.7 268 7.71 9.5 199 Example 5 13.9 1.9 215 7.98 18.9 200 Example 6 13.9 1.9 218 7.99 21.7 207 Example 7 12.5 1.7 294 7.74 7.3 175 Comparative 13.0 1.7 302 7.79 0.2 157 Example 1

[0222] [Conclusion]

[0223] In Examples 1 through 7 and Comparative Example 1, as a result of measuring the contained amount of the component that is contained in the porous layer and that is to be eluted into NMP, the contained amount of the component that is contained in the porous layer and that is to be eluted into NMP was not substantially changed from the contained amount of the component that is contained in the composition and that is to be eluted into NMP. Therefore, it has been found that the porous layer in accordance with an embodiment of the present invention can be produced by using, as a raw material, a composition which is constituted by a resin having an amide bond and in which a contained amount of a component that is to be eluted into NMP is not less than 6.0% by weight and not more than 25.0% by weight.

[0224] As shown in Table 1, the short circuit time of the nonaqueous electrolyte secondary battery including any of the porous layers described in Examples 1 through 7 is greater than the short circuit time of the nonaqueous electrolyte secondary battery including the porous layer described in Comparative Example 1. Therefore, it has been found that the porous layer in accordance with an embodiment of the present invention can improve durability of a nonaqueous electrolyte secondary battery with respect to charge-discharge cycles.

INDUSTRIAL APPLICABILITY

[0225] The nonaqueous electrolyte secondary battery porous layer in accordance with an embodiment of the present invention can be suitably utilized as a member of a nonaqueous electrolyte secondary battery which is excellent in durability with respect to charge-discharge cycles.