Crosslinked polymer binder from crosslinkable monomer for nonaqueous electrolyte secondary battery and use thereof

Abstract

A binder for a nonaqueous electrolyte secondary battery electrode and use thereof are described. The binder contains a crosslinked polymer or salt thereof, the crosslinked polymer having an ethylenically unsaturated carboxylic acid and a crosslinkable monomer in constituent monomers thereof, or salt thereof, wherein the crosslinked polymer includes the ethylenically unsaturated carboxylic acid in an amount of 20 to 99.95 mass % of the total constituent monomers, and the crosslinked polymer includes at least one compound selected from the group made of trimethylolpropane diallyl ether and trimethylolpropane triallyl ether as the crosslinkable monomer.

Claims

1. A binder for a nonaqueous electrolyte secondary battery electrode, the binder comprising a crosslinked polymer comprising an ethylenically unsaturated carboxylic acid and a crosslinkable monomer in constituent monomers, or salt thereof, wherein the crosslinked polymer comprises the ethylenically unsaturated carboxylic acid in an amount of 20 to 99.95 mass % of the total constituent monomers, and the crosslinkable monomer comprises at least one compound selected from the group consisting of trimethylolpropane diallyl ether and trimethylolpropane triallyl ether.

2. The binder for a nonaqueous electrolyte secondary battery electrode according to claim 1, wherein the crosslinked polymer comprises the at least one compound selected from the group consisting of trimethylolpropane diallyl ether and trimethylolpropane triallyl ether in an amount of 0.05 to 5 mass % of the total constituent monomers.

3. The binder for a nonaqueous electrolyte secondary battery electrode according to claim 1, wherein a particle diameter of the crosslinked polymer is 0.1 to 7.0 μm in a volume-based median diameter when the crosslinked polymer is neutralized to a neutralization degree of 80 to 100 mol %, subjected to water swelling in water, and then dispersed in a 1 mass % NaCl aqueous solution.

4. A nonaqueous electrolyte secondary battery mixture layer composition comprising a binder according to claim 1, an active material, and water.

5. The nonaqueous electrolyte secondary battery mixture layer composition according to claim 4, further comprising a carbon material or a silicon material as a negative electrode active material.

6. The nonaqueous electrolyte secondary battery mixture layer composition according to claim 4, further comprising a lithium-containing metal oxide as a positive electrode active material.

7. A nonaqueous electrolyte secondary battery electrode comprising a mixture layer on a collector surface, the mixture layer being constituted of a nonaqueous electrolyte secondary battery mixture layer composition according to claim 1.

8. The binder for a nonaqueous electrolyte secondary battery electrode according to claim 2, wherein a particle diameter of the crosslinked polymer is 0.1 to 7.0 μm in a volume-based median diameter when the crosslinked polymer is neutralized to a neutralization degree of 80 to 100 mol %, subjected to water swelling in water, and then dispersed in a 1 mass % NaCl aqueous solution.

Description

EXAMPLES

(1) The present teachings will be described in detail below based on examples. However, the present teachings are not limited to these examples. In the following, “parts” and “%” mean parts by mass and % by mass respectively, unless otherwise specified.

Manufacturing Example 1

Manufacture of Crosslinked Polymer R-1

(2) A reactor equipped with a stirring blade, a thermometer, a reflux condenser and a nitrogen inlet pipe was used for polymerization.

(3) 880 parts of acetonitrile, 99.90 parts of acrylic acid (hereunder referred to as “AA”), and 0.10 parts of trimethylolpropane diallyl ether (product name “Neoallyl T-20” by Daiso Co., Ltd.) were charged into the reactor.

(4) The inside of the reactor was thoroughly purged with nitrogen, and heated to raise its internal temperature to 55° C. Once the internal temperature was confirmed to have stabilized at 55° C., 0.0625 parts of 2,2′-azobis(2,4-dimethylvaleronitrile) (product name “V-65” by Wako Pure Chemical Industries, Ltd.) were added as the polymerization initiator, and since white turbidity was observed in the reaction solution at this point, this was taken as the polymerization initiation point. The polymerization reaction was continued with the external temperature (water bath temperature) being adjusted to maintain the internal temperature of 55° C., then cooling of the reaction solution was initiated when 6 hours had elapsed since the polymerization initiation point, and after when the internal temperature was cooled to 30° C. or lower, a slurry-like polymerization reaction solution having particles of the crosslinked polymer R-1 (unneutralized) dispersed in the medium was obtained.

(5) The resulting polymer reaction solution was centrifuged to precipitate the polymer particles, and the supernatant was removed. The precipitate was then re-dispersed in acetonitrile having the same mass as the polymer reaction solution, and the operations of precipitating the polymer particles by centrifugation and removing the supernatant were repeated twice. The precipitate was collected and dried for 3 hours at 80° C. under reduced pressure to remove the volatile components and obtain a powder of the crosslinked polymer R-1. Because the crosslinked polymer R-1 is hygroscopic, it was sealed and stored in a container having water vapor barrier properties.

(6) (Measuring Average Particle Diameter of the Crosslinked Polymer R-1 Neutralized Salt in 1 Mass % NaCl Aqueous Solution)

(7) 0.25 g of the crosslinked polymer R-1 powder obtained above and 49.75 g of lithium hydroxide aqueous solution (including lithium hydroxide corresponding to 85 mol % of carboxyl group which the crosslinked polymer R-1 contains) were measured into a 100 cc container, and set in a rotating/revolving mixer (“Awatori Rentaro AR-250” by Thinky Corporation). This was then stirred (rotating speed 2,000 rpm/revolving speed 800 rpm, 7 minutes), and then defoamed (rotating speed 2,200 rpm/revolving speed 60 rpm, 1 minute) to prepare a hydrogel of the crosslinked polymer R-1 (neutralization degree 85 mol %) swelled with water.

(8) Next, the particle size distribution of this hydrogel was measured with a laser diffraction/scattering type particle size distribution analyzer (Nikkiso Co., Ltd., Microtrac MT-3300EX2) using a 1 mass % NaCl aqueous solution as a dispersion medium. With the dispersion medium circulating in an excess amount relative to the hydrogel, when the hydrogel in an amount sufficient to obtain a suitable scattered light intensity was added and the dispersion medium was added, the measured particle size distribution shape stabilized after a few minutes. Once stability was confirmed, volume-based particle size distribution measurement was performed, and the average particle diameter was found to be 2.0 μm (median diameter (D50)).

(9) A 85 mol % neutralized product of the crosslinked polymer R-1 swells thoroughly in ion-exchange water to form a hydrogel, but in the 1 mass % NaCl aqueous solution the degree of swelling is reduced because the electrostatic repulsion between carboxy anions is blocked, and particle size distribution measurement is possible because dispersion stability in the dispersion medium is maintained by the effect of the carboxylate salt. The smaller the median diameter as measured in the 1 mass % NaCl aqueous solution medium, the more the crosslinked polymer salt is regarded as forming the hydrogel as an aggregation of smaller (more numerous) gel particles even in the ion-exchange water. That is, this means it is broken up into smaller particles in water.

Manufacturing Example 2

Manufacture of Crosslinked Polymer R-2

(10) The same operations were performed as in Manufacturing Example 1 except that the charged amounts of each starting material were as shown in Table 1, to obtain crosslinked polymer R-2 in powder form. The crosslinked polymer R-2 was sealed and stored in a container having water vapor barrier properties.

(11) Further, Li neutralization product was prepared for each polymer as obtained by same operations as in Manufacturing Example 1. Three types of lithium hydroxide aqueous solution for use in the neutralization, respectively containing lithium hydroxide corresponding to 85 mol %, 90 mol %, and 95 mol % of carboxyl group which the crosslinked polymer R-2 contains, were prepared, and Li neutralization salts of the crosslinked polymer R-2 having different neutralization degrees were prepared. The average particle diameter of each neutralization salt in 1 mass % NaCl aqueous solution was measured, and the results thereof are shown in Table 1.

Manufacturing Examples 3 to 8, 12, and 14

Manufacture of Crosslinked Polymers R-3 to 8, R-12, and R-14

(12) The same operations were performed as in Manufacturing Example 1 except that the charged amounts of each starting material were as shown in Table 1, to obtain crosslinked polymers R-3 to 8, R-12, and R-14 in powder form. The respective crosslinked polymers were sealed and stored in a container having water vapor barrier properties.

(13) Further, Li neutralization products were prepared similar to Manufacturing Example 1 for the respective polymers as obtained, and the average particle diameters thereof were measured in the 1 mass % NaCl aqueous solution. The results are shown in Table 1.

Manufacturing Example 9

Manufacture of Crosslinked Polymer Salt R-9

(14) A reactor equipped with a stirring blade, a thermometer, a reflux condenser and a nitrogen inlet pipe was used for polymerization.

(15) 875.6 parts of acetonitrile, 4.40 parts of ion exchanged water, 99.00 parts of AA, 1.00 parts of Neoallyl T-20 were charged into the reactor. The inside of the reactor was thoroughly purged with nitrogen, and heated to raise its internal temperature to 55° C. Once the internal temperature was confirmed to have stabilized at 55° C., 0.0625 parts of V-65 were added as the polymerization initiator, and since white turbidity was observed in the reaction solution at this point, this was taken as the polymerization initiation point. The polymerization reaction was continued with the external temperature (water bath temperature) being adjusted to maintain the internal temperature of 55° C., then cooling of the reaction solution was initiated when 6 hours had elapsed since the polymerization initiation point, and after when the internal temperature was cooled to 25° C., 49.1 parts of powder lithium hydroxide monohydrate (hereunder termed “LiOH.H.sub.2O”) were added. Stirring under the room temperature was continued for 12 hours after this addition to obtain a slurry-like polymerization reaction solution having particles of the crosslinked polymer salt R-9 (Li salt, neutralization degree of 85 mol %) dispersed in the medium.

(16) The resulting polymer reaction solution was centrifuged to precipitate the polymer particles, and the supernatant was removed. The precipitate was then re-dispersed in acetonitrile having the same mass as the polymer reaction solution, and the operations of precipitating the polymer particles by centrifugation and removing the supernatant were repeated twice. The precipitate was collected and dried for 3 hours at 80° C. under reduced pressure to remove the volatile components and obtain a powder of the crosslinked polymer salt R-9. Because the crosslinked polymer salt R-9 is hygroscopic, it was sealed and stored in a container having water vapor barrier properties. The powder of the crosslinked polymer salt salt R-9 was measured by IR to obtain the neutralization degree from an intensity ratio of a peak derived from C═O group of carboxylic acid and a peak derived from C═O group of carboxylic acid Li, and the neutralization degree thereof was 85 mol %, identical to the calculated value from the charged substances.

(17) (Measuring Average Particle Diameter of the Crosslinked Polymer Salt R-9 in 1 Mass % NaCl Aqueous Solution)

(18) 0.25 g of the crosslinked polymer salt R-9 powder obtained above and 49.75 g of ion exchanged water were measured into a 100 cc container, and set in a rotating/revolving mixer (“Awatori Rentaro AR-250” by Thinky Corporation). This was then stirred (rotating speed 2,000 rpm/revolving speed 800 rpm, 7 minutes), and then defoamed (rotating speed 2,200 rpm/revolving speed 60 rpm, 1 minute) to prepare a hydrogel of the crosslinked polymer salt R-9 swelled with water.

(19) Next, the particle size distribution of this hydrogel was measured with the laser diffraction/scattering type particle size distribution analyzer (Nikkiso Co., Ltd., Microtrac MT-3300EX2) using a 1 mass % NaCl aqueous solution as a dispersion medium. With the dispersion medium circulating in an excess amount relative to the hydrogel, when the hydrogel in an amount sufficient to obtain a suitable scattered light intensity was added and the dispersion medium was added, the measured particle size distribution shape stabilized after a few minutes. Once stability was confirmed, volume-based particle size distribution measurement was performed, and the average particle diameter was found to be 2.2 μm (median diameter (D50)).

Manufacturing Example 10

Manufacture of Crosslinked Polymer Salt R-10

(20) A reactor equipped with a stirring blade, a thermometer, a reflux condenser and a nitrogen inlet pipe was used for polymerization.

(21) 300 parts of methanol, 99.00 parts of AA, and 1.00 parts of Neoallyl T-20 were charged into the reactor. Then, 29.5 parts of LiOH—H.sub.2O powder and 1.40 parts of ion exchange water were added slowly under stirring while internal temperature is maintained at 40° C. or lower.

(22) The inside of the reactor was thoroughly purged with nitrogen, and heated to raise its internal temperature to 68° C. Once the internal temperature was confirmed to have stabilized at 68° C. 0.02 parts of 4,4′-azobiscyanovaleric acid (product name “ACVA” by Otsuka Chemical Co., Ltd.) were added as the polymerization initiator, and since white turbidity was observed in the reaction solution at this point, this was taken as the polymerization initiation point. The polymerization reaction was continued with the external temperature (water bath temperature) being adjusted so as to gently reflux the solvent, and solvent reflux was maintained while 0.02 parts of ACVA were added 3 hours after the polymerization initiation point and an additional 0.035 parts of ACVA were added 6 hours after the polymerization initiation point, and the reflux of the solvent was continued. Cooling of the reaction solution was initiated 9 hours after the polymerization initiation point, the internal temperature was lowered to 30° C. and 19.6 parts of LiOH.H.sub.2O powder were then added slowly so that the internal temperature did not exceed 50° C. After the addition of the LiOH.H.sub.2O powder, stirring was continued for 3 hours to obtain a slurry-like polymer reaction solution comprising particles of the crosslinked polymer salt R-10 (neutralization degree 85 mol %) dispersed in the medium.

(23) The resulting polymer reaction solution was centrifuged to precipitate the polymer particles, and the supernatant was removed. The precipitate was then re-dispersed in acetonitrile having the same mass as the polymer reaction solution, and the operations of precipitating the polymer particles by centrifugation and removing the supernatant were repeated twice. The precipitate was collected and dried for 3 hours at 80° C. under reduced pressure to remove the volatile components and obtain a powder of the crosslinked polymer salt R-10. Because the crosslinked polymer salt R-10 is hygroscopic, it was sealed and stored in a container with water vapor barrier properties. When the powder of the crosslinked polymer salt R-10 was measured by IR and the neutralization degree was determined from the intensity ratio of the peak derived from the C═O group of the carboxylic acid Li and the peak derived from the C═O of the lithium carboxylate, it was equal to the calculated value from charging, which was 85 mol %.

(24) As in Manufacturing Example 9, the average particle diameter of the resulting polymer salt was measured in the 1 mass % NaCl aqueous solution. The results are shown in Table 1.

Manufacturing Example 11

Manufacture of Crosslinked Polymer R-11

(25) A reactor equipped with a stirring blade, a thermometer, a reflux condenser and a nitrogen inlet pipe was used for polymerization.

(26) 880 parts of acetonitrile, 30 parts of AA, 70 parts of isobornyl acrylate, 1.00 parts of Neoallyl T-20, as well as triethylamine corresponding to 1.0 mol % of the AA were charged into the reactor. The inside of the reactor was thoroughly purged with nitrogen, and heated to raise its internal temperature to 55° C. Once the internal temperature was confirmed to have stabilized at 55° C. 0.0625 parts of V-65 were added as the polymerization initiator, and since white turbidity was observed in the reaction solution at this point, this was taken as the polymerization initiation point. The polymerization reaction was continued with the external temperature (water bath temperature) being adjusted to maintain the internal temperature of 55° C., then the temperature was increased to 65° C. at the time when 6 hours had elapsed since the polymerization initiation point. The internal temperature was maintained at 65° C., and cooling of the reaction solution was initiated when 12 hours had elapsed since the polymerization initiation point, and the internal temperature was cooled to 30° C. or lower to obtain a slurry-like polymerization reaction solution having particles of the crosslinked polymer salt R-11 (unneutralized) dispersed in the medium.

(27) The resulting polymer reaction solution was centrifuged to precipitate the polymer particles, and the supernatant was removed. The precipitate was then re-dispersed in acetonitrile having the same mass as the polymer reaction solution, and the operations of precipitating the polymer particles by centrifugation and removing the supernatant were repeated twice. The precipitate was collected and dried for 3 hours at 80° C. under reduced pressure to remove the volatile components and obtain a powder of the crosslinked polymer salt R-11. Because the crosslinked polymer salt R-11 is hygroscopic, it was sealed and stored in a container with water vapor barrier properties.

(28) Further, the Li neutralization product was prepared for the obtained crosslinked polymer R-11 (unneutralized) as in Manufacturing Example 1, after which the average particle diameter of the resulting polymer salt was measured in the 1 mass % NaCl aqueous solution. The results are shown in Table 1.

Manufacturing Example 13

Manufacture of Crosslinked Polymer Salt R-13

(29) The same operations were performed as in Manufacturing Example 9 except that the charged amounts of each starting material were as shown in Table 1, to obtain crosslinked polymer salt R-13 in powder form. The crosslinked polymer salt R-13 was sealed and stored in a container having water vapor barrier properties. The powder of the crosslinked polymer salt R-13 was measured by IR and the neutralization degree was determined from the intensity ratio of the peak derived from the C═O group of the carboxylic acid Li and the peak derived from the C═O of the lithium carboxylate, it was equal to the calculated value from charging, which was 85 mol %.

(30) The average particle diameter of the obtained polymer salt was measured in the 1 mass % NaCl aqueous solution as in Manufacturing Example 9. The results are shown in Table 1.

Manufacturing Example 15

Manufacture of Crosslinked Polymer R-15

(31) The same operations were performed as in Manufacturing Example 11 except that the charged amounts of each starting material were as shown in Table 1, however, uniform stirring became difficult during the polymerization due to significant generation of aggregates by which the polymerizing operation had to be stopped, so crosslinked polymer R15 was not obtained.

(32) TABLE-US-00001 TABLE 1 Manufacturing Example No. Manufac. Manufac. Manufac. Manufac. Manufac. Manufac. Manufac. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Crosslinked Polymer R-1 R-2 R-3 R-4 R-5 R-6 R-7 Charged Monomer AA 99.90 99.70 99.00 99.00 98.00 96.50 94.00 Substances IBXA 5.00 [parts] PEA Crosslinkable T-20 0.10 0.30 1.00 1.00 2.00 3.50 1.00 Monomer EGDMA MBAA Initial LiOH•H.sub.2O Neutralization Organic Amine TEA [mol %] Polymerization Water Solvent AcN 880 880 880 440 880 880 880 EAc 440 MeOH Polymerization V-65 0.0625 0.0625 0.0625 0.0625 0.0625 0.0625 0.0625 Inhibitor Initial ACVA Added ACVA Process LiOH•H.sub.2O Neutralization Neutralization Degree 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% (Initial Neutralization + Process Neutralization) Average Particle Diameter Neutralization 85.0% 85.0% 90.0% 95.0% 85.0% 85.0% 85.0% 85.0% 85.0% Measurement in 1 wt % Degree NaCl Water Solution Average 2.0 1.8 1.8 1.8 1.7 5.6 2.0 3.8 2.1 Particle Diameter [μm] Manufacturing Example No. Manufac. Manufac. Manufac. Manufac. Manufac. Manufac. Manufac. Manufac. Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 15 Crosslinked Polymer R-8 R-9 R-10 R-11 R-12 R-13 R-14 R-15 Charged Monomer AA 70.00 99.00 99.00 30.00 99.00 99.00 99.00 15.00 Substances IBXA 70.00 85.00 [parts] PEA 29.00 Crosslinkable T-20 1.00 1.00 1.00 1.00 1.00 Monomer EGDMA 1.00 1.00 MBAA 1.00 Initial LiOH•H.sub.2O 29.5 Neutralization Organic Amine TEA 1.0 1.0 [mol %] Polymerization Water 4.40 1.40 Solvent AcN 880.0 875.6 880.0 880.0 880.0 880 880 EAc MeOH 300 Polymerization V-65 0.0625 0.0625 0.0625 0.0625 0.0625 0.0625 0.0625 Inhibitor Initial ACVA 0.020 Added ACVA 0.055 Process LiOH•H.sub.2O 49.1 19.6 49.1 Neutralization Neutralization Degree 0.0% 85.0% 85.0% 0.0% 0.0% 85.0% 0.0% 0.0% (Initial Neutralization + Process Neutralization) Average Particle Diameter Neutralization 85.0% 85.0% 85.0% 85.0% 85.0% 85.0% 85.0% — Measurement in 1 wt % Degree NaCl Water Solution Average 2.4 2.2 13.1 1.2 26.8 29.3 31.5 — Particle Diameter [μm]

(33) The details of the compounds used in Table 1 are given below.

(34) AA: Acrylic acid

(35) IBXA: Isobornyl acrylate

(36) PEA: Phenoxy ethyl acrylate (Osaka Organic Chemical Industry Ltd., Viscoat #192)

(37) T-20: Trimethylolpropane diallyl ether (Daiso Co., Ltd. Neoallyl™ T-20)

(38) EGDMA: Ethylene glycol dimethcylate

(39) MBAA: methylene bisacrylamide

(40) TEA: Triethylamine

(41) AcN: Acetonitrile

(42) EAc: Ethyl acetate

(43) MeOH: Methanol

(44) V-65: 2,2′-azobis(2,4-dimethylvaleronitrile) (product of Wako Pure Chemical Industries, Ltd.)

(45) ACVA: 4,4′-azobiscyanovaleric acid (product of Otsuka Chemical Co., Ltd.)

(46) (Electrode Evaluation: Negative Electrode)

Example 1

(47) The coating properties of a mixture layer composition using graphite as the negative electrode active material and the crosslinked polymer R-1 as the binder, and the peel strength between the formed mixture layer and the collector (that is, the binding ability of the binder) were measured.

(48) 100 parts of natural graphite (product name “CGB-10” by Nippon Graphite Industries) and 2.2 parts of the crosslinked polymer R-1 in powder form were weighed and thoroughly premixed, and a solution in which 1.09 parts of LiOH—H.sub.2O powder (corresponding to neutralization degree of 85 mol %) were dissolved in 160 parts of ion-exchange water was added and pre-dispersed with the disperser, after which the main dispersion was performed for 15 seconds at the peripheral speed of 20 m/second with the thin film swirling mixer (Primix Corporation, FM-56-30) to obtain a slurry-like negative electrode mixture layer composition.

(49) This mixture layer composition was coated with an adjustable applicator on a 20 μm-thick copper foil (Nippon Foil Mfg. Co., Ltd.) so that the dried and pressed film thickness was 50 μm, and then immediately dried for 10 minutes at 100° C. in the ventilating dryer to form a mixture layer. The external appearance of the resulting mixture layer was observed with the naked eyes, and the coating properties were evaluated according to the below standard and judged as good (“A”).

(50) (Coating Property Evaluation Standard)

(51) A: No streaks, spots or other appearance defects observed on surface

(52) B: Slight streaks, spots or other appearance defects observed on surface

(53) C: Obvious streaks, spots or other appearance defects observed on surface

(54) (90° Peel Strength (Binding Ability))

(55) The mixture layer density was adjusted with a roll press to 1.70±0.05 g/cm.sup.3 to prepare an electrode, which was then cut into a 25 mm-wide strip to prepare a sample for peel testing. The mixture layer side of this sample was affixed to a horizontally fixed double-sided tape, after which dehydration was performed thereon at 60° C. under reduced pressure (10 kPa or less) by a vacuum dryer, and stored in aluminum laminate bag having water vapor barrier properties at 23° C., and then peeled at 90° at a rate of 50 mm/minute, and the peel strength between the mixture layer and the copper foil was measured. The peel strength was high at 6.3 N/m, exhibiting a favorable strength.

(56) In general, when an electrode is cut, worked and assembled into a battery cell, greater peel strength is necessary to prevent the problem of detachment of the mixture layer from the collector (copper foil). The high peel strength in this case means that the binder provides excellent binding ability between the active materials and between the active material and the electrode, and suggests that it is possible to obtain a battery with excellent durability and little loss of capacity during charge-discharge cycle testing.

(57) (Flex Resistance)

(58) This was evaluated using the electrode sample similar to that used in the 90° peel strength test. The electrode sample was wrapped around a SUS rod with 2.0 mm diameter, the condition of the bent mixture layer was observed, and flex resistance was evaluated based on the following standard, resulting in an evaluation of “A”.

(59) A: No appearance defects observed in mixture layer

(60) B: Fine cracks observed in mixture layer

(61) C: Obvious cracks observed in the mixture layer, or the mixture layer partially detached

Examples 2 to 13 and Comparative Examples 1 and 2

(62) Mixture layer compositions were prepared by the same operations as in Example 1 except that types and quantities of the crosslinked polymers used as the binder, the neutralizers, and the ion exchange water were as shown in Tables 2 and 3, and the coating properties, 90° peel strength and flex resistance were evaluated. In preparing the mixture layer composition, the blending quantity of the ion exchange water was suitably adjusted to achieve suitable viscosity for coating. The results are shown in Tables 2 and 3.

(63) TABLE-US-00002 TABLE 2 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Graphite (CGB-10) 100 100 100 100 100 100 100 100 Crosslinked Type R-1 R-2 R-2 R-2 R-3 R-4 R-5 R-6 Polymer Parts 2.20 2.20 2.20 2.20 2.20 2.20 2.20 2.20 Neutralizer Type LiOH•H.sub.2O LiOH•H.sub.2O LiOH•H.sub.2O LiOH•H.sub.2O LiOH•H.sub.2O LiOH•H.sub.2O LiOH•H.sub.2O LiOH•H.sub.2O Parts 1.09 1.09 1.15 1.22 1.08 1.08 1.07 1.05 Neutralization Degree 85% 85% 90% 95% 85% 85% 85% 85% Ion Exchange Water 160 160 150 150 140 140 130 124 Mixture Layer Slurry 38.9% 38.9% 40.4% 40.4% 42.1% 42.1% 43.9% 45.0% Concentration Coating Properties A A A A A A A A Peel Strength N/m 6.3 9.4 8.8 8.9 10.3 5.4 7.0 6.1 Flex Resistance A A A A A A A A

(64) TABLE-US-00003 TABLE 3 Comparative Comparative Example 9 Example 10 Example 11 Example 12 Example 13 Example 1 Example 2 Graphite (CGB-10) 100 100 100 100 100 100 100 Crosslinked Type R-7 R-8 R-9 R-10 R-11 R-12 R-14 Polymer Parts 2.20 2.20 2.20 2.20 2.20 2.20 2.20 Neutralizer Type LiOH•H.sub.2O LiOH•H.sub.2O LiOH•H.sub.2O LiOH•H.sub.2O LiOH•H.sub.2O LiOH•H.sub.2O LiOH•H.sub.2O Parts 1.03 0.76 — — 0.33 1.08 1.08 Neutralization Degree 85% 85% 85% 85% 85% 85% 85% Ion Exchange Water 150 170 125 125 125 140 140 Mixture Layer Slurry 40.4% 37.5% 45.0% 45.0% 45.0% 42.1% 42.1% Concentration Coating Properties A A A A B A B Peel Strength N/m 10.7 11.2 9.8 4.5 7.5 1.3 0.9 Flex Resistance A A A A A C C

Example 14

(65) The coating properties of a mixture layer composition using silicon particles and graphite as the negative electrode active material and the crosslinked polymer salt R-9 as the binder, and the peel strength between the formed mixture layer and the collector (that is, the binding ability of the binder) were measured.

(66) 30 parts of silicon particles (Sigma-Aldrich Corporation, Si Nanopowder, particle diameter <100 nm) and 70 parts of natural graphite (product name “CGB-10” by Nippon Graphite Industries) were stirred for 1 hour at 300 rpm with a planetary ball mill (Fritsch GmbH, P-5). 1.8 parts of the crosslinked polymer salt R-9 in the powder form were weighed into the resulting mixture and thoroughly premixed, 120 parts of ion-exchange water were added, and the mixture was pre-dispersed with the disperser, after which the main dispersion was performed for 15 seconds at the peripheral speed of 20 m/second with the thin film swirling mixer (Primix Corporation, FM-56-30) to obtain a slurry-like negative electrode mixture layer composition.

(67) The obtained negative electrode mixture layer composition was evaluated similar to Example 1. However, the mixture layer concentration of the electrode sample used in the evaluation of 90° peeling strength and flex resistance was prepared to 1.85±0.05 g/cm.sup.3. The result is shown in Table 4.

Example 15 and Comparative Examples 3 and 4

(68) Mixture layer compositions were prepared by the same operations as in Example 14 except that the active materials and the crosslinked polymers used as the binder were as shown in Table 4, and the coating properties, 90° peel strength and flex resistance were evaluated. The results are shown in Table 4.

(69) TABLE-US-00004 TABLE 4 Example Example Comparative Comparative 14 15 Example 3 Example 4 Active Graphite 70 85 70 85 Material Silicon 30 15 30 15 Particles Crosslinked Type R-9 R-9 R-13 R-13 Polymer Salt Parts 1.80 1.80 1.80 1.80 Ion Exchange Water 120 120 120 120 Mixture Layer Slurry 45.9% 45.9% 45.9% 45.9% Concentration Coating Properties A A A A Peel Strength N/m 18.7 15.0 2.7 2.1 Flex Resistance A A C C
(Electrode Evaluation: Positive Electrode)

Example 16

(70) The coating properties of a mixture layer composition using lithium nickel cobalt manganese oxide (NCM) as the positive electrode active material, acetylene black (AB) as the conductive assistant and the crosslinked polymer R-1 as the binder were measured, and the peel strength between the formed mixture layer and the collector (that is, the binding ability of the binder) was evaluated.

(71) 95 parts of NCM111 (Toda Kogyo Corp., NM-3050), 5 parts of AB (Denki Kagaku HS-100) and 1.5 parts of the crosslinked polymer R-1 in powder form were weighed and thoroughly premixed, 110 parts of ion-exchange water were added, and the mixture was pre-dispersed with the disperser, after which the main dispersion was performed for 15 seconds at the peripheral speed of 20 m/second with the thin film swirling mixer (Primix Corporation, FM-56-30) to obtain a slurry-like positive electrode mixture layer composition. Because lithium ions are eluted (alkalized, exchanged for protons in water) from the NCM in the positive electrode mixture layer composition, some (or all) of the carboxyl groups of the crosslinked polymer R-1 are neutralized and converted to lithium salts. This positive electrode mixture layer composition had a pH of 8.7.

(72) This mixture layer composition was coated with the adjustable applicator on the 15 thick aluminum foil (Nippon Foil Mfg. Co., Ltd.) so that the dried and pressed film thickness was 50 μm, and then immediately dried for 10 minutes at 100° C. in the ventilating dryer to form a mixture layer. The external appearance of the resulting mixture layer was observed with the naked eyes, and the coating properties were evaluated according to the following standard and judged as good (“A”).

(73) (Coating Property Evaluation Standard)

(74) A: No streaks, spots or other appearance defects observed on surface

(75) B: Slight streaks, spots or other appearance defects observed on surface

(76) C: Obvious streaks, spots or other appearance defects observed on surface

(77) (90° Peel Strength (Binding Ability))

(78) The mixture layer density was adjusted with the roll press to 2.7±0.1 g/cm.sup.3 to prepare an electrode, which was then cut into a 25 mm-wide strip to prepare a sample for the peel testing. The mixture layer side of this sample was affixed to a horizontally fixed double-sided tapes, after which dehydration was performed thereon at 60° C. under reduced pressure (10 kPa or less) by a vacuum dryer, and stored in an aluminum laminate bag having water vapor barrier properties at 23° C., and then peeled at 90° at the rate of 50 mm/minute, and the peel strength between the mixture layer and the copper foil was measured. The peel strength was high at 7.9 N/m, exhibiting a favorable strength.

(79) (Flex Resistance)

(80) Flex resistance was evaluated using the electrode sample similar to that used in the 90° peel strength test. The electrode sample was wrapped around the SUS rod with 2.0 mm diameter, the condition of the bent mixture layer was observed, and flex resistance was evaluated based on the following standard, resulting in an evaluation of “A”.

(81) A: No appearance defects observed in mixture layer

(82) B: Fine cracks observed in mixture layer

(83) C: Obvious cracks observed in mixture layer, or mixture layer partially detached

Examples 17 to 21 and Comparative Examples 5 and 6

(84) Mixture layer compositions were prepared by the same operations as in Example 16 except that the crosslinked polymers used as the binder were as shown in Table 5, and the coating properties, 90° peel strength and flex resistance were evaluated. The results are shown in Table 5.

(85) TABLE-US-00005 TABLE 5 Example Example Example Example Example Example Comparative Comparative 16 17 18 19 20 21 Example 5 Example 6 NCM 95 95 95 95 95 95 95 95 Acetylene Black  5  5  5  5  5  5  5  5 Crosslinked Type R-1 R-2 R-3 R-4 R-5 R-6 R-12 R-14 Polymer Parts 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Ion Exchange Water 110 110 110 110 110 110 110 110 Mixture Layer Slurry 48.0% 48.0% 48.0% 48.0% 48.0% 48.0% 48.0% 48.0% Concentration Coating Properties A A A B A A B C Peel Strength N/m 7.9 11.1 11.2 6.1 10.5 9.9 3.3 1.9 Flex Resistance A A A B A A C C

(86) Examples 1 to 21 produce the electrode mixture layer composition including the binder for nonaqueous electrolyte secondary battery electrode belonging to the teachings herein and the electrode using the same. The coating properties of the respective mixture layer compositions (slurry) was excellent, and the peel strength between the mixture layer and the collector of the obtained electrode exhibits high values, and excellent binding ability is exhibited. Further, the flex resistance of the electrodes was also confirmed as surpassing a satisfying level.

(87) On the other hand, with the crosslinked polymers R-12 to R-14 were crosslinked monomers obtained by using crosslinkable monomers other than trimethylolpropane diallyl ether and trimethylolpropane triallyl ether, in which the peel strength of the mixture layer was low, and the flex resistance of the electrode was also inadequate.

INDUSTRIAL APPLICABILITY

(88) Because the binder for a nonaqueous electrolyte secondary battery electrode of the present teachings exhibits excellent binding ability in the mixture layer, the nonaqueous electrolyte secondary battery provided with the electrode obtained using this binder is expected to have good durability (cycle characteristics) even after repeated high-rate charge and discharge, and should be applicable to vehicle-mounted secondary batteries.

(89) Moreover, the binder of the present teachings can also impart good flex resistance to the electrode mixture layer. Consequently, it can help to reduce troubles and increase yield during electrode manufacture.