JP2002373701A - Method of manufacturing for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a nonaqueous electrolyte secondary battery capable of inhibiting a decrease in battery performance and reducing manufacturing costs. SOLUTION: In a preparation step, a positive electrode is fabricated using a positive electrode mix mixed with a binder containing lithium manganate, graphite, and an acrylic polymer of polyacrylic acid or polyacrylic acid ester, and a negative electrode is fabricated using a negative mix mixed with a binder containing graphite or amorphous carbon, and an acrylic polymer of polyacrylic acid or polyacrylic acid ester. In a fabrication step, the positive and negative electrodes are wound via a separator made from polyethylene to fabricate a group of windings. In a drying step, it is heated and dried at reduced pressure. The binders containing the acrylic polymers absorb moisture in the positive and negative electrodes, with the moisture being eliminated in the drying step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a non-aqueous electrolyte secondary battery, and more particularly to a method for manufacturing a non-aqueous electrolyte secondary battery having a group of electrode windings soaked in the non-aqueous electrolyte. .

[0002]

2. Description of the Related Art Lithium ion secondary batteries, which represent non-aqueous electrolyte secondary batteries, are mainly used for powering portable devices such as VTR cameras, notebook computers, and mobile phones, taking advantage of their high energy density. Have been. The internal structure of this battery is usually a wound structure as shown below. The electrode is a belt-like shape in which the active material is coated on a metal foil for both the positive electrode and the negative electrode. The cross section is spirally wound so that the positive electrode and the negative electrode do not come into direct contact with each other with a separator interposed therebetween, forming an electrode winding group. Have been. The electrode wound group is housed in a cylindrical battery can serving as a battery container, and is sealed after the electrolyte is injected.

The size of a general cylindrical lithium ion secondary battery is 18650 type, which has a diameter of 18 mm and a height of 65 mm, and is widely used as a small consumer lithium ion battery. As the positive electrode active material of the 18650 type lithium ion secondary battery, lithium cobalt oxide characterized by high capacity and long life is mainly used. The battery capacity is approximately 1.3 Ah to 1.7 Ah, and the output is approximately 1 Ah.
It is about 0W.

On the other hand, in the automobile industry, in order to cope with environmental problems, an electric vehicle having no exhaust gas and having only a power source entirely of a battery and a hybrid having both an internal combustion engine and a battery as a power source ( The development of electric vehicles has been accelerated and some of them are now in practical use.

[0005] A battery serving as a power source of an electric vehicle is naturally required to have characteristics capable of obtaining high output and high energy, and a non-aqueous electrolyte secondary battery has attracted attention as a battery that meets these requirements. For the spread of electric vehicles, it is essential to lower the price of batteries, and for that purpose, low-cost battery materials are required. In particular, lithium manganate LiMn ₂ O ₄ having a spinel crystal structure has attracted particular attention, and improvements have been made for higher performance of batteries. Specifically, a lithium-rich composition in which the atomic ratio of lithium to manganese (Li / Mn) is larger than 0.5 or a part of manganese atoms in the spinel crystal is replaced with Fe, Co, Ni, C
Attempts have been made to substitute or dope other metal elements such as r, Cu, Al, and Mg. A positive electrode mixture obtained by mixing a positive electrode active material such as lithium cobaltate or lithium manganate, a carbon material such as graphite or acetylene black as a conductive material, and a binder is applied to the foil-shaped current collector in a strip shape. The electrode is formed by compressing in the thickness direction. Generally, polyvinylidene fluoride (PVDF) is used as a binder (binder).

[0006]

However, in the case of a non-aqueous electrolyte secondary battery, if water is mixed in the battery, the electrode is deteriorated or the non-aqueous electrolyte which plays an important function in the charge / discharge electrode reaction is not used. By reacting the lithium ions diffused with the water and the water, the movement of the lithium ions is inhibited,
This causes a reduction in charge / discharge capacity and discharge output, and a reduction in life. Therefore, a dry atmosphere is required in the battery manufacturing process in order to avoid the incorporation of moisture, which contributes to high cost. Although electrodes and electrode winding groups can be manufactured in a non-dry atmosphere to reduce costs, PVDF, which is generally used as a binder, easily absorbs moisture, and the absorbed moisture is then subjected to operations such as heating and decompression. Cannot be easily removed. Moisture remaining in the PVDF leaks into the non-aqueous electrolyte when the battery is charged and discharged, and as a result, the non-aqueous electrolyte is deteriorated, leading to a decrease in battery performance. In particular, when amorphous carbon is used as the negative electrode carbon material, the amorphous carbon has a property of easily adsorbing moisture, so that the negative electrode is significantly deteriorated and the battery performance is significantly lowered. there were.

The present invention has been made in view of the above circumstances, and has as its object to provide a method of manufacturing a non-aqueous electrolyte secondary battery capable of suppressing a decrease in battery performance and reducing manufacturing costs.

[0008]

In order to solve the above-mentioned problems, a first aspect of the present invention is a method for producing a non-aqueous electrolyte secondary battery having a group of electrode windings soaked in a non-aqueous electrolyte. hand,
Lithium transition metal double oxide, a non-dried positive electrode coated with a positive electrode mixture obtained by mixing a binder containing a conductive material and an acrylic polymer, and a binder containing a carbon material and an acrylic polymer. Preparing a non-dried negative electrode in which the mixed negative electrode mixture is applied to a belt-shaped current collector and a separator having microporosity through which lithium ions can pass, and winding the positive electrode and the negative electrode through the separator To form an electrode winding group, and drying the electrode winding group under reduced pressure heating.

In this embodiment, leakage of water into the non-aqueous electrolyte causes deterioration of electrodes and deterioration of battery performance.
In the preparation step, a binder containing an acrylic polymer is mixed and contained in the positive electrode mixture and the negative electrode mixture, the binder absorbs moisture in the positive electrode and the negative electrode, and after the electrode winding group is produced in the production step, a drying step is performed. The electrode winding group is dried under reduced pressure and heating to remove moisture absorbed by the non-dried positive and negative electrode binders. For this reason, it is possible to suppress a decrease in battery performance due to water contamination, and since the flexibility of the positive electrode and the negative electrode using a binder containing an acrylic polymer decreases in a dry state, the non-dry state in the manufacturing step is reduced. Since the electrode winding group is formed by being wound as it is, the winding operation becomes easy, and damage to the electrode can be prevented. In addition, by using a binder containing an acrylic polymer for the positive electrode and the negative electrode, the electrode winding group can be manufactured while the electrodes are not dried, so that the preparation step and the manufacturing step are performed in a dry atmosphere that increases costs. There is no need to perform this, and cost can be reduced.

A second aspect of the present invention is a method for producing a non-aqueous electrolyte secondary battery having an electrode winding group soaked in a non-aqueous electrolyte, comprising a lithium transition metal double oxide, a conductive material and a binder. A positive electrode in a dry state in which a mixed positive electrode mixture is applied to a belt-shaped current collector, and a non-dried state in which a negative electrode mixture in which a binder containing amorphous carbon and an acrylic polymer is mixed is applied to a band-shaped current collector A negative electrode and a separator having microporosity through which lithium ions can pass are prepared, and the positive electrode and the negative electrode are wound through the separator to form an electrode winding group, and the electrode winding group is heated under reduced pressure. Drying underneath. Further, a third aspect of the present invention is a method for producing a nonaqueous electrolyte secondary battery having an electrode winding group soaked in a nonaqueous electrolyte, comprising a lithium transition metal double oxide, a conductive material, and an acrylic polymer. A positive electrode in a non-dried state in which a positive electrode mixture mixed with a binder containing the union is applied to a band-shaped current collector, and a negative electrode in a dry state in which a negative electrode mixture mixed with a carbon material and a binder is applied to a band-shaped current collector Prepare a separator having a microporous through which lithium ions can pass, prepare the electrode winding group by winding the positive electrode and the negative electrode through the separator, and dry the electrode winding group under reduced pressure heating Including the steps.

In the second embodiment, in the preparatory step, a binder other than the binder containing an acrylic polymer, for example, a commonly used binder such as PVDF is mixed and contained in the positive electrode mixture, the positive electrode is dried, and the amorphous carbon is removed. The second embodiment is different from the first embodiment in that a binder containing an acrylic polymer and an acrylic polymer are mixed and contained in the negative electrode mixture. The positive electrode using a binder such as PVDF does not lose its flexibility in the dry state.
In the manufacturing step, the winding operation is facilitated, and the negative electrode using amorphous carbon has a property that amorphous carbon easily adsorbs moisture, and the positive electrode is in a dry state, so that it is possible to prevent water contamination. it can. Therefore, by performing the drying step after the manufacturing step, the deterioration of the electrode plate and the deterioration of the battery performance due to the mixing of moisture do not occur. In the third embodiment, in the preparation step, a binder containing an acrylic polymer is mixed and contained in the positive electrode mixture, and a binder other than the binder containing the acrylic polymer, for example, a commonly used binder such as PVDF is mixed with the negative electrode. Mix and contain in the material to make it dry. The positive electrode using the binder containing the acrylic polymer has the same function and effect as the positive electrode of the first embodiment described above, and the negative electrode using the binder such as PVDF has the same function and effect as the positive electrode of the second embodiment described above. .

In the first and third aspects described above,
If the water content of the positive electrode in the preparation step is 1000 ppm or more, the flexibility of the positive electrode can be sufficiently ensured, so that the winding operation in the manufacturing step is further facilitated and the damage to the positive electrode is reliably prevented. be able to. Further, in the first aspect and the second aspect, if the water content of the negative electrode in the preparation step is 500 ppm or more, the flexibility of the negative electrode can be sufficiently ensured, so that the winding operation in the manufacturing step is not required. This further facilitates the prevention of damage to the negative electrode. Furthermore, in the first aspect, the water content of the positive electrode in the preparation step is 1000 ppm or more, and if the water content of the negative electrode is 500 ppm or more, the flexibility of the electrode can be sufficiently ensured. The winding operation in the manufacturing step is further facilitated, and damage to the electrode can be reliably prevented.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment in which the present invention is applied to a cylindrical lithium ion battery of a power source for an electric vehicle will be described below with reference to the drawings.

<Preparation Step> To briefly explain the preparation step of the present embodiment, as shown in Table 1 below, an acrylic polymer is used as a binder to prepare a non-dried positive electrode and negative electrode. It is as follows.

[0015]

[Table 1]

(Positive electrode) Lithium manganate (LiMn ₂ O ₄ ) powder having an average particle size of 15 μm, graphite powder having an average particle size of 5 μm as a conductive material, acetylene black, and an acrylic material such as polyacrylic acid or polyacrylate. A binder containing a polymer is mixed in a mass ratio of 80: 12: 3: 5, N-methyl-2-pyrrolidone (NMP) as a dispersion solvent is added thereto, and the mixture is kneaded to prepare a slurry. did. The obtained slurry was applied to both sides of a 20-μm-thick strip-shaped aluminum foil (positive electrode current collector) so that the application amount of the mixture (positive electrode mixture) excluding NMP was 130 g / m ² . At this time, a width of 30 mm
Was left uncoated. Thereafter, the NMP was volatilized and removed, and then pressed and cut to a width of 82 mm, a length of 374 cm, and a thickness of the positive electrode mixture application portion (excluding the thickness of the aluminum foil) of 98 μm.
Was obtained. The pressure at the time of pressing was adjusted to make the bulk density of the positive electrode mixture layer 2.65 g / cm ³ . Next, a cutout was made in the uncoated portion, and the remaining cutout was used as a positive electrode lead piece. Adjacent positive electrode lead pieces were set at intervals of 50 mm, and the width of the positive electrode lead piece was set at 5 mm. The prepared positive electrode was kept in a non-dried state without performing a moisture drying operation.

Here, examples of the acrylic polymer include polyacrylic acid esters such as polyacrylic acid and polymethyl acrylate, and polymethacrylic esters such as polymethyl methacrylate. May be appropriately mixed and used.

(Negative Electrode) 92 parts by mass of graphite or amorphous carbon powder as a negative electrode carbon material were mixed with 8 parts by mass of a binder containing the acrylic polymer described above, and NMP as a dispersion solvent was added thereto.
Was added and kneaded to prepare a slurry. The obtained slurry was coated on both sides of a 10 μm-thick strip-shaped rolled copper foil (negative electrode current collector) with an application amount of a mixture material (negative electrode mixture material) excluding NMP of 45.
2 or 33.3 g / m ² . At this time, an uncoated portion having a width of 30 mm was left on one side edge in the negative electrode long dimension direction. Thereafter, NMP was volatilized and removed, followed by pressing and cutting to obtain a negative electrode having a width of 86 mm, a length of 386 cm, and a thickness of the negative electrode mixture application portion (excluding the thickness of the copper foil) of 66 μm. The pressure at the time of pressing was adjusted, and the negative electrode was compressed so that the porosity of the negative electrode mixture layer became about 35%. Next, a cutout was made in the uncoated portion in the same manner as the positive electrode, and the remaining cutout was used as a negative electrode lead piece. Adjacent negative electrode lead pieces were set at intervals of 50 mm, and the width of the negative electrode lead piece was set at 5 mm. The preparation of the negative electrode was performed in an atmosphere of constant moisture, and the NMP was completely removed by volatilization similarly to the positive electrode, and the prepared negative electrode was kept in a non-dried state.

(Separator) A separator was prepared by cutting a polyethylene film having a thickness of 40 μm and having a microporosity through which lithium ions could pass through to a width of 90 mm and a predetermined length.

<Preparation Step> As shown in FIG. 1, the non-dried positive electrode and negative electrode prepared in the preparation step are wound together with the prepared separator W5 so that these two electrode plates do not come into direct contact with each other. Was prepared. The winding operation was performed in an atmosphere of 30 ± 10% RH. At the center of the winding, a hollow cylindrical shaft core 1 made of polypropylene is used. At this time, the positive electrode lead piece 2 and the negative electrode lead piece 3 are on the opposite sides of the winding group (electrode winding group) 6, respectively. At both ends. Further, the length of the separator W5 was adjusted, and the diameter of the winding group 6 was set to 38 ± 0.1 mm.

<Drying Step> As described above, the wound group 6 formed by winding the electrode in a non-dried state is heated to a predetermined temperature in an environment where the pressure is reduced to a predetermined pressure as described later. It was dried for a predetermined time.

<Assembly of Battery> Next, the cylindrical lithium ion battery 20 was manufactured as follows using the wound group 6 dried as described above. The positive electrode lead pieces 2 were deformed, and all of them were gathered and brought into contact with the vicinity of the flange peripheral surface integrally projecting from the periphery of the positive electrode current collecting ring 4 substantially on the extension of the axis 1 of the winding group 6. After that, positive electrode lead 2
The positive electrode lead 2 was connected to the flange peripheral surface by ultrasonic welding. On the other hand, the connection operation between the negative electrode current collecting ring 5 and the negative electrode lead
The connection operation was performed in the same manner.

Thereafter, an insulating coating was applied to the entire peripheral surface of the flange portion of the positive electrode current collecting ring 4. For this insulating coating, a pressure-sensitive adhesive tape was used in which the base material was polyimide and one side thereof was coated with a pressure-sensitive adhesive composed of hexamethacrylate. This adhesive tape was wound one or more times from the peripheral surface of the flange portion to the outer peripheral surface of the winding group 6 to form an insulating coating, and the winding group 6 was inserted into a nickel-plated steel battery container 7. The outer diameter of the battery container 7 is 40 mm, and the inner diameter is 39 mm.

A negative electrode lead plate 8 for electrical conduction is welded to the negative electrode current collecting ring 5 in advance, and after the winding group 6 is inserted into the battery container 7, the bottom of the battery container 7 and the negative electrode lead plate 8 And was welded.

On the other hand, a positive electrode lead 9 formed by laminating a plurality of aluminum ribbons is welded to the positive electrode current collecting ring 4 in advance, and the other end of the positive electrode lead 9 is sealed with the battery container 7. To the lower surface of the battery lid. The battery lid is provided with a cleavage valve 11 as an internal pressure release mechanism that is opened in accordance with an increase in the internal pressure of the cylindrical lithium ion battery 20. The cleavage pressure of the cleavage valve 11 was set to about 9 × 10 ⁵ Pa. The battery lid is composed of a lid case 12, a lid cap 13, a valve retainer 14 for keeping airtightness, and a cleavage valve 11, and these are stacked and assembled by caulking the periphery of the lid case 12. .

A predetermined amount of the non-aqueous electrolyte is poured into the battery case 7, and then the battery case 7 is covered with the battery cover so that the positive electrode lead 9 is folded.
The cylindrical lithium-ion battery 20 was completed by caulking and sealing through the inside of the battery.

The non-aqueous electrolyte contains lithium hexafluorophosphate (L) in a mixed solution of ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1: 1: 1.
iPF ₆ ) dissolved at 1 mol / liter was used.

In this embodiment, by using a binder containing an acrylic polymer, the binder absorbs moisture in the positive electrode and the negative electrode, and the wound group 6 formed by winding the non-dried electrode is heated under reduced pressure. Dry underneath. Thereby, the water in the positive electrode and the negative electrode absorbed by the binder containing the acrylic polymer is removed, and in particular, when amorphous carbon having a property of easily adsorbing water is used for the negative electrode carbon material, the negative electrode Can be removed without deteriorating the water content.
Accordingly, the reduction in battery performance due to water contamination is suppressed, and the capacity, output, and life of the cylindrical lithium-ion battery 2 are excellent.
0 can be obtained. In addition, an electrode using a binder containing an acrylic polymer has a reduced flexibility in a dehydrated and dried state, and may cause cracks or the like by being wound. To the manufacturing step. This facilitates the winding operation and prevents damage to the electrodes. At this time, the water content of the positive electrode is preferably 1000 ppm or more, and the water content of the negative electrode is preferably 500 ppm or more.

(Second Embodiment) Next, a second embodiment in which the present invention is applied to a cylindrical lithium ion battery of a power supply for an electric vehicle will be described. In the following embodiments, the same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. Only different points will be described.
In the present embodiment, as shown in Table 1, in the preparation step, a positive electrode in a dry state using PVDF for a binder and a negative electrode in a non-dry state using an acrylic polymer for a binder are prepared. The details are as follows.

<Preparation Step> (Positive electrode) Lithium manganate (Li) having an average particle size of 15 μm
Mn ₂ O ₄ ) powder, graphite powder having an average particle size of 5 μm as a conductive material, acetylene black, and PVDF were mixed at a mass ratio of 80: 12: 3: 5, and a dispersion solvent was added thereto. N-methyl-2-pyrrolidone (NMP) was added and kneaded to prepare a slurry. Using the obtained slurry, a positive electrode was prepared in the same manner as in the first embodiment. next,
The prepared positive electrode was heated to a predetermined temperature under a reduced pressure of a predetermined pressure and dried for a predetermined time.

(Negative Electrode) 92 parts by mass of amorphous carbon powder as a negative electrode carbon material was mixed with 8 parts by mass of a binder containing the above-mentioned acrylic polymer, NMP as a dispersion solvent was added thereto, and kneaded to obtain a slurry. Was prepared. A negative electrode was obtained using the obtained slurry in the same manner as in the first embodiment. The prepared negative electrode was kept in a non-dried state.

<Preparation Step> As shown in FIG. 1, an electrode wound group was prepared in the same manner as in the first embodiment, using the dried positive electrode and the non-dried negative electrode prepared in the preparation step. Similarly, the winding operation was performed in an atmosphere of 30 ± 10% RH. However, in consideration of the fact that PVDF easily absorbs moisture, it is necessary to minimize the possibility of mixing of water into the electrode during the winding operation. To work.

Next, as in the first embodiment, a cylindrical lithium ion battery 20 was completed through a drying step and battery assembly.

According to the present embodiment, the positive electrode using PVDF as the binder does not lose its flexibility in the dry state, the winding operation is easy in the manufacturing step, and amorphous carbon is used. Since the negative electrode has a property that amorphous carbon easily adsorbs moisture, and the positive electrode is in a dry state, it is possible to prevent moisture from being mixed. Therefore, by performing the drying step after the manufacturing step, it is possible to suppress the deterioration of the electrode plate and the deterioration of the battery performance due to the incorporation of moisture, and to obtain the cylindrical lithium ion battery 20 excellent in capacity, output, and life.

(Third Embodiment) In the third embodiment, Table 1
As shown in the above, in the preparation step, a non-dried positive electrode using an acrylic polymer as a binder and a dry negative electrode using PVDF as a binder are prepared, and details are as follows. is there.

<Preparation Step> (Positive Electrode) In the same manner as in the first embodiment, a positive electrode using an acrylic polymer as a binder was prepared. The preparation of the positive electrode was performed in an atmosphere of constant moisture, and the prepared positive electrode was kept in a non-dried state.

(Negative Electrode) 92 parts by mass of graphite or amorphous carbon powder as a negative electrode carbon material was mixed with 8 parts by mass of PVDF as a binder, and NMP as a dispersion solvent was added thereto and kneaded to prepare a slurry. A negative electrode was prepared using the obtained slurry in the same manner as in the first embodiment. Next, the prepared positive electrode was heated to a predetermined temperature under a reduced pressure of a predetermined pressure and dried for a predetermined time.

<Preparation Step> As shown in FIG. 1, an electrode winding group was prepared in the same manner as in the first embodiment, using the non-dried positive electrode and the dried negative electrode prepared in the preparation step. Similarly, the winding operation was performed in an atmosphere of 30 ± 10% RH. However, in consideration of the fact that PVDF easily absorbs moisture, it is necessary to minimize the possibility of mixing of water into the electrode during the winding operation. To work.

Next, as in the first embodiment, a cylindrical lithium ion battery 20 was completed through a drying step and battery assembly.

In this embodiment, by using a binder containing an acrylic polymer for the positive electrode, the binder absorbs moisture in the positive electrode, and the wound group 6 formed by winding the non-dried positive electrode is heated under reduced pressure. Dry underneath. Thereby, the moisture in the positive electrode absorbed by the binder containing the acrylic polymer is removed. In addition, a positive electrode using a binder containing an acrylic polymer has a reduced flexibility in a dehydrated and dried state, and may cause cracking or the like by being wound. To the manufacturing step. This facilitates the winding operation and prevents damage to the positive electrode. At this time, the water content of the positive electrode is preferably set to 1000 ppm or more. In addition, the negative electrode using PVDF as a binder does not decrease in flexibility in a dry state, the winding operation is facilitated in the manufacturing step, and the dry state can prevent the incorporation of moisture. Therefore, a reduction in battery performance due to the incorporation of moisture can be suppressed by passing through a drying step after the fabrication step, and the cylindrical lithium ion battery 20 excellent in capacity, output, and life can be obtained.

[0041]

Next, examples of the cylindrical lithium ion battery 20 manufactured according to the above embodiment will be described.
Note that a battery of a comparative example manufactured for comparison is also described.

(Example 1) As shown in Table 2 below, in Example 1, according to the first embodiment, the binder A described below was used for both the positive electrode and the negative electrode, and the mesophase-based spherical graphite (Kawasaki Steel Co., Ltd.) was used as the negative electrode carbon material. Company name, KMFC)
A positive electrode and a negative electrode were produced in an atmosphere of 30 ± 10% RH.
The application amount of the negative electrode mixture was 45.2 g / m ² . Also,
After preparing the same electrode as the electrode used for producing the battery and measuring the mass, the water content of the electrode was reduced to 120 ° C. under a reduced pressure of 90 kPa lower than the atmospheric pressure.
For 24 hours, the mass after drying was measured, and the mass difference before and after the drying was calculated and determined (the method of calculating the water content of the electrode is the same in the following Examples and Comparative Examples). The water content of the positive electrode of this example thus determined was 870.
ppm, and the water content of the negative electrode was 490 ppm. Further, the drying conditions of the electrode winding group in the drying step,
The pressure was reduced to 90 kPa lower than the atmospheric pressure or less, and the temperature was set to 60 ° C. for 72 hours (the drying conditions of the electrode winding group are the same in the following Examples and Comparative Examples). In Table 2, the binder A was only polyacrylic acid,
Binder B is a mixture of polyacrylic acid and polymethyl acrylate (polyacrylate) mixed at a mass ratio of 7: 3, and binder C is a mixture of polyacrylic acid and polymethyl methacrylate (polymethacrylate). And Binder D is a mixture of polyacrylic acid, polymethyl acrylate, and polymethyl methacrylate (polymethacrylate) in a mass ratio of 5: 2: 3. Of the resulting mixture. Further, after applying the mixture to the current collector and evaporating and removing NMP, it was confirmed by gas chromatography / mass spectrometry that no NMP remained in the mixture layer.

[0043]

[Table 2]

(Examples 2 to 4) As shown in Table 2, in Examples 2 to 4, positive electrodes and negative electrodes were produced in the same manner as in Example 1 except that the binder was changed. In the second embodiment, the binder B is used. In the third embodiment, the binder C is used.
In Example 4, binder D was used. The water content of the positive electrode was 920 ppm in Example 2, and 840 p in Example 3.
pm and 960 ppm in Example 4. The water content of the negative electrode was 430 ppm and 470 pp, respectively.
m and 440 ppm.

Example 5 As shown in Table 2, Example 5
Then, the positive electrode was manufactured in the same manner as the positive electrode of Example 1. Also,
The negative electrode was prepared using amorphous carbon (Carbotron, trade name, manufactured by Kureha Chemical Industry Co., Ltd.) as the negative electrode carbon material and using a binder A in an atmosphere of 30 ± 10% RH. The applied amount of the negative electrode mixture was 33.3 g / m ² . The water content of the positive electrode was 870 ppm, and the water content of the negative electrode was 470 pp.
m.

(Examples 6 to 8) As shown in Table 2, in Examples 6 to 8, positive electrodes and negative electrodes were produced in the same manner as in Example 5 except that the binder was changed. In the sixth embodiment, the binder B is used. In the seventh embodiment, the binder C is used.
In Example 8, the binder D was used. The water content of the positive electrode was 920 ppm in Example 6, and 840 p in Example 7.
pm and 960 ppm in Example 8. The water content of the negative electrode was 460 ppm and 490 pp, respectively.
m and 480 ppm.

(Examples 9 and 10) As shown in Table 2, in Examples 9 and 10, the production of the positive electrode was 60 ± 2.
A positive electrode and a negative electrode were produced in the same manner as in Example 1 except that the reaction was performed in an atmosphere of 0% RH. The water content of the positive electrode was 1000 ppm in Example 9 and 2700 ppm in Example 10. The water content of the negative electrode was determined in Example 9,
In all of Examples 10, the content was 490 ppm.

(Examples 11 to 12) As shown in Table 2, in Examples 11 to 12, the binders were used and the negative electrodes were produced in an atmosphere of 60 ± 20% RH. In the same manner as in Example 1, a positive electrode and a negative electrode were produced. The water content of the positive electrode was 920 p in both Examples 11 and 12.
pm. The water content of the negative electrode was
500 ppm and 900 ppm.

(Examples 13 and 14) As shown in Table 2, Examples 13 and 14 were the same as Example 1 except that the binder C was used and an atmosphere of 60 ± 20% RH was used. A positive electrode and a negative electrode were produced. The water content of the positive electrode is
In Example 13, 1000 ppm, and in Example 14, 270 ppm.
It was 0 ppm. The water content of the negative electrode was 500 ppm and 900 ppm, respectively.

(Examples 15 to 16) As shown in Table 2, in Examples 15 to 16, in the same manner as in Example 5 except that the binder D was used and the atmosphere was 60 ± 20% RH. A positive electrode and a negative electrode were produced. The water content of the positive electrode is
In Example 15, 1000 ppm, and in Example 16, 270 ppm.
It was 0 ppm. The water content of the negative electrode was 500 ppm and 1200 ppm, respectively.

(Examples 17 and 18) As shown in Table 2, in Examples 17 and 18, except that the negative electrode was produced in an atmosphere of 60 ± 20% RH using the binder D. In the same manner as in Example 5, a positive electrode and a negative electrode were produced. The water content of the positive electrode was 920 p in both Examples 17 and 18.
pm. The water content of the negative electrode was
500 ppm and 1200 ppm.

(Example 19) As shown in Table 2, in Example 19, according to the second embodiment, the positive electrode was PV
After the DF was prepared in an atmosphere of 5 ± 2% RH, the pressure was reduced to 60 kPa lower than the atmospheric pressure by 60 kPa or less.
Drying was performed at 24 ° C. for 24 hours. The negative electrode was manufactured in the same manner as the negative electrode of Example 1 except that the negative electrode was used in an atmosphere of 60 ± 20% RH using a binder B. The water content of the positive electrode is 3
The water content of the negative electrode was 620 ppm.

(Example 20) As shown in Table 2, in Example 20, according to the third embodiment, the positive electrode was manufactured in the same manner as the positive electrode of Example 1 except that binder B was used. In addition, the negative electrode was manufactured in an atmosphere of 5 ± 2% RH using mesophase-based spheroidal graphite as a negative electrode carbon material and PVDF as a binder. Drying was performed at 24 ° C. for 24 hours. The application amount of the negative electrode mixture was 45.2 g / m ² . The water content of the positive electrode was 920 ppm, and the water content of the negative electrode was 280 ppm.
ppm.

Example 21 As shown in Table 2, in Example 21, according to the second embodiment, a positive electrode was manufactured and dried in the same manner as the positive electrode of Example 19. The negative electrode was manufactured in the same manner as the negative electrode of Example 19 except that amorphous carbon was used as the negative electrode carbon material. The water content of the positive electrode was 300 ppm, and the water content of the negative electrode was 620 ppm.

Comparative Example 1 As shown in Table 2, Comparative Example 1
Then, the positive electrode uses PVDF for the binder, and 5 ± 2% R
H atmosphere, then 90 kP below atmospheric pressure
a Drying was performed at 60 ° C. for 24 hours under reduced pressure below the low pressure. Further, the negative electrode was manufactured using mesophase-based spheroidal graphite as the negative electrode carbon material, using a binder B in an atmosphere of 5 ± 2% RH, and then operating at 60 ° C. under a reduced pressure of 90 kPa lower than the atmospheric pressure. For 24 hours. The application amount of the negative electrode mixture was 45.2 g / m ² . The water content of the positive electrode was 300 ppm, and the water content of the negative electrode was 19 ppm.
It was 0 ppm. The electrode wound group was not dried.

Comparative Example 2 As shown in Table 2, Comparative Example 2
Then, a positive electrode and a negative electrode were prepared and dried in the same manner as in Comparative Example 1 except that amorphous carbon was used as the negative electrode carbon material, and the coating amount of the negative electrode mixture was 33.3 g / m ² . The water content of the positive electrode is 300 ppm, and the water content of the negative electrode is 220 ppm.
Met. The electrode winding group was not dried.

Comparative Example 3 As shown in Table 2, Comparative Example 3
Then, binder B is used for the positive electrode, and PV is used for the binder of the negative electrode.
A positive electrode and a negative electrode were prepared and dried in the same manner as in Comparative Example 1 except that DF was used. The water content of the positive electrode was 290 ppm, and the water content of the negative electrode was 280 ppm. The electrode wound group was not dried.

Comparative Example 4 As shown in Table 2, Comparative Example 4
Then, the positive electrode uses PVDF for the binder,
% RH and was not dried. Also,
The negative electrode was prepared and dried in the same manner as the negative electrode of Comparative Example 1. The water content of the positive electrode was 1680 ppm, and the water content of the negative electrode was 220 ppm. The electrode wound group was not dried.

Comparative Example 5 As shown in Table 2, Comparative Example 5
Then, the positive electrode was manufactured using a binder B in an atmosphere of 60 ± 20% RH. In addition, the negative electrode was manufactured in a 60 ± 20% RH atmosphere using mesophase-based spherical graphite as the negative electrode carbon material and PVDF as the binder. The application amount of the negative electrode mixture was 45.2 g / m ² . The water content of the positive electrode was 1000 ppm, and the water content of the negative electrode was 660 p.
pm. The positive electrode and the negative electrode were wound without drying, and after the winding, the electrode wound group was dried under the above-mentioned drying conditions.

Comparative Example 6 As shown in Table 2, Comparative Example 6
Then, a positive electrode and a negative electrode were produced in the same manner as in Comparative Example 5, except that amorphous carbon was used as the negative electrode carbon material, and the coating amount of the negative electrode mixture was 33.3 g / m ² . Water content of the positive electrode is 1000p
pm, and the water content of the negative electrode was 750 ppm. The positive electrode and the negative electrode were wound without drying, and after the winding, the electrode wound group was dried under the above-mentioned drying conditions.

<Test / Evaluation> Next, the following series of tests were performed on the batteries of the examples and comparative examples manufactured as described above.

The batteries of Examples and Comparative Examples were charged and then discharged, and the discharge capacities were measured. The charging conditions were a constant voltage of 4.2 V, a limited current of 5 A, and 3.5 hours. The discharge conditions are
The constant current was 5 A, and the final voltage was 2.7 V.

The discharge output of the battery in the charged state under the above conditions was measured. The measurement conditions were 1A, 3A, and 6A. The voltage at 5 seconds was read at each discharge current, the voltage was plotted on the vertical axis against the current value on the horizontal axis, and an approximate straight line connecting three points was 2.7.
The product of the current value at the intersection with V and 2.7 V was used as the output.

Further, each of the batteries of Examples and Comparative Examples was repeatedly charged and discharged 100 times under the above conditions, and then the discharge capacity was measured. The capacity retention ratio with respect to the initial discharge capacity was shown as a percentage. Naturally, the higher the capacity retention ratio, the better the life characteristics.

The charge, discharge, and output measurements were all performed in an atmosphere at an ambient temperature of 25 ± 1 ° C. The results of each measurement are shown in Table 3 below.

[0066]

[Table 3]

As shown in Table 3, the battery of the example in which the acrylic polymer was used as the binder of the positive and negative electrode mixture and the electrode winding group was dried was higher in capacity and output than the battery of the comparative example. ,
It became a long-life battery. Examples 5 to 8 and Examples 15 to 1 using amorphous carbon as the negative electrode carbon material
In the battery of No. 8, the output was higher than those of the batteries of Examples 1 to 4 and Examples 9 to 14 under almost the same conditions except that graphite was used as the negative electrode carbon material. The batteries of Examples 9, 10, and 13 to 16 in which the water content of the positive electrode was 1000 ppm or more were higher capacity, higher output, and longer life. In addition, the batteries of Examples 11 to 18 in which the water content of the negative electrode was 500 ppm or more were batteries with higher capacity, higher output, and longer life. In particular, in the batteries of Examples 13 to 16 in which the water content of the positive electrode was 1000 ppm or more and the water content of the negative electrode was 500 ppm or more, the deterioration of the battery performance was suppressed, and the capacity, output, and capacity retention were reduced. All were high batteries.

The batteries of Examples 19 to 21 are excellent in battery performance. However, in Examples 19 and 21, PVDF is used for the positive electrode binder. In Example 20, PVDF is used for the negative electrode binder. Since the electrode is used, in order to avoid the residual water, the electrode preparation in the preparation step is performed in a dry atmosphere, dried to a dry state, and the electrode winding group is further dried through the preparation step. Therefore, it is not preferable in terms of manufacturing cost.

In the batteries of Comparative Examples 1 and 2, the discharge capacity, output, and capacity retention of the batteries were all significantly reduced. When the battery was disassembled and the electrodes were observed, no abnormality was found in the positive electrode. However, in the negative electrode, cracks occurred in a part of the mixture layer, and a part of the mixture was peeled off from the current collector. The cause of the cracks and peeling is that the negative electrode using an acrylic polymer as a binder was dried in a preparation step, and the dried negative electrode was wound in a manufacturing step. That is, it is considered that the acrylic polymer had a reduced flexibility in the completely dehydrated and dried state, and the electrode could not follow the winding curvature at the time of winding. For this reason, it is speculated that the electrode reaction was not performed sufficiently and uniformly, the discharge capacity and output were reduced, and because the reaction was not homogeneous, the electrode reaction site was limited and the current density was concentrated, leading to a reduction in life. .

On the other hand, the electrodes of the examples using the acrylic polymer as the binder were wound in a non-dried state, so that the flexibility did not decrease at the time of winding and could follow the winding curvature. It was considered that there was no cracking or peeling of the positive / negative electrode mixture. Since the electrode is fixed in a wound state (wound curvature) by being wound, even if it is rolled and then dried after forming a wound group to reduce flexibility, it does not crack or peel. Was.

When the battery of Comparative Example 3 was dismantled and observed, no abnormality was observed in the negative electrode, but cracks and peeling were also observed in a part of the positive electrode mixture layer. In Comparative Example 4, in addition to the occurrence of the above-described abnormality in the negative electrode, the PVDF used as the binder of the positive electrode was not sufficiently dried, so that the water leaked from the PVDF in the battery deteriorated the electrolyte. As a result, the capacity retention rate is reduced. Also in the batteries of Comparative Examples 5 and 6, the negative electrode using PVDF as a binder was insufficiently dried, and the battery performance was deteriorated due to residual moisture. The fact that the battery performance was lowered despite drying the electrode winding group indicates that water remaining in PVDF cannot be easily removed by a general drying operation. In particular, in the electrode using amorphous carbon, the performance decrease due to moisture is larger than that in the electrode using graphite, and the capacity retention ratio of the battery of Comparative Example 6 is further remarkably reduced.

As described above, the cylindrical lithium ion battery 20 of the above embodiment is formed by winding an electrode manufactured by using a binder containing an acrylic polymer for the binder of the positive electrode and / or the negative electrode mixture. By drying the electrode-wound group after forming the group, the water in the positive electrode and / or the negative electrode absorbed by the binder is sufficiently removed, so that a decrease in battery performance due to water contamination can be suppressed. . Also,
In the first embodiment, it is not necessary to perform the preparation step and the manufacturing step in a dry atmosphere that increases the cost, and the cost can be reduced. In the first and third embodiments, if the water content of the positive electrode produced in the preparation step is set to 1000 ppm or more, the winding operation can be easily performed. Furthermore, in the first embodiment and the second embodiment, if the water content of the negative electrode manufactured in the preparation step is set to 500 ppm or more, the winding operation can be easily performed.

In the above embodiment, a comparatively large secondary battery used for a power supply for an electric vehicle has been described as an example. However, the present invention is not limited to the size and the battery capacity of the battery. Has been confirmed to exhibit Further, the shape of the battery to which the present invention can be applied may be other than the battery having a structure in which the battery upper lid is sealed by caulking in the above-described bottomed cylindrical container (can). An example of such a structure is a battery in which the positive and negative external terminals penetrate the battery cover and the positive and negative external terminals press against each other via the shaft core in the battery container. Furthermore, the present invention is not limited to a cylindrical battery, and can be applied to, for example, a nonaqueous electrolyte secondary battery in which a positive electrode and a negative electrode are wound in a triangular, quadrangular, square, or polygonal shape to form an electrode winding group. .

In the above embodiment, the electrode winding group was dried at 60 ° C. for 72 hours under reduced pressure of 90 kPa lower than the atmospheric pressure. The time may be appropriately determined, and may be any condition as long as moisture is sufficiently removed.

Furthermore, in the above embodiment, the positive electrode for a lithium ion battery is lithium manganate, the negative electrode is graphite or amorphous carbon, and the electrolyte is ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1: 1: 1.
A solution in which lithium hexafluorophosphate was dissolved at 1 mol / l in a mixed solution of was used. However, the battery of the present invention is not particularly limited, and any of the commonly used positive electrode conductive materials is also used. Can also be used. There is no limitation on the composition of the mixture of the positive electrode mixture and the negative electrode mixture, the amount of the mixture applied, the mixture density, and the electrode thickness. In general, lithium manganate can be synthesized by mixing and baking an appropriate lithium salt and manganese oxide. However, by controlling the charging ratio of the lithium salt and manganese oxide, the desired Li / Mn ratio can be obtained. can do.

Examples of the lithium transition metal double oxide that can be used in other than the above-mentioned embodiment include lithium cobalt oxide and other materials into which lithium can be inserted and desorbed, and lithium in which a sufficient amount of lithium has been inserted in advance. As long as it is a manganese double oxide, lithium manganate having a spinel structure, or a part of manganese or lithium in a crystal may be replaced with another element (eg, Li, Fe, Co, Ni, Cr,
Al, Mg, etc.) may be used. Further, the crystal structure has a layered structure, and some of manganese and lithium in the crystal are replaced with other elements (eg, Li, Fe, Co, Ni, Cr, A).
1, manganese, etc.).

Furthermore, although PVDF has been exemplified as the binder of the positive electrode of the second embodiment and the negative electrode of the third embodiment, any commonly used binder can be used. For example, Teflon (registered trademark), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethylcellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride And polymers such as chloroprene fluoride and mixtures thereof.

Further, the carbon material for a negative electrode for a lithium ion battery that can be used in other than the above embodiment is not particularly limited, other than the matters described in the claims. For example,
Natural graphite, artificial graphite materials, coke, and carbonaceous materials such as amorphous carbon may be used.
The shape is not particularly limited, such as a scale, a sphere, a fiber, and a lump.

Further, in the above-described embodiment, an example is shown in which an adhesive tape is used in which the base material is polyimide and the adhesive agent made of hexamethacrylate is applied to one surface of the insulating coating. Or a polyolefin such as polyethylene, an adhesive tape having an acrylic adhesive such as hexamethacrylate or butyl acrylate applied to one or both surfaces thereof, or a tape made of a polyolefin or polyimide to which no adhesive is applied may be suitably used. it can.

Further, as the non-aqueous electrolytic solution other than the one used in the above embodiment, an electrolytic solution obtained by dissolving a general lithium salt as an electrolyte in an organic solvent is used. The lithium salt or organic solvent used is not particularly limited. For example, as the electrolyte, LiClO ₄ , LiAsF ₆ , LiP
F ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ L
i, CF ₃ SO ₃ Li, or a mixture thereof can be used. Non-aqueous electrolyte organic solvents include propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolan,
Methyl-1,3-dioxolan, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitonyl, etc., or a mixed solvent of two or more thereof may be used, and the mixing ratio is not limited.

[0081]

As described above, according to the manufacturing method of the present invention, in the preparation step, the positive electrode and / or the negative electrode are mixed and mixed.
After absorbing the water in the positive electrode and / or the negative electrode with the binder containing the acrylic polymer contained therein, and preparing the electrode winding group in the manufacturing step, the electrode winding group is dried under reduced pressure heating in the drying step. And the non-dried positive electrode and / or
Alternatively, since the moisture absorbed by the binder of the negative electrode is removed, the deterioration of the battery performance due to the contamination with water can be suppressed, and the positive electrode and / or the negative electrode using the binder containing the acrylic polymer can be dried. Since the flexibility decreases, the electrode is wound in a non-dried state in the manufacturing step to form an electrode-wound group, thereby facilitating the winding operation and preventing the electrode from being damaged. Since the electrode winding group can be manufactured as it is, there is no need to perform the preparation step and the manufacturing step in a dry atmosphere that increases the cost, and the effect that the cost can be reduced can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a cylindrical lithium ion battery according to an embodiment to which the present invention can be applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Shaft core 2 Positive electrode lead piece 3 Negative electrode lead piece 4 Positive electrode current collecting ring 5 Negative current collecting ring 6 Winding group (Electrode winding group) 7 Battery container 8 Negative lead plate 9 Positive electrode lead 10 Gasket 11 Cleavage valve 12 Lid case 13 Lid cap 14 Valve holder 20 Cylindrical lithium ion battery (non-aqueous electrolyte secondary battery) W1 Positive electrode current collector W2 Positive electrode mixture layer W3 Negative electrode current collector W4 Negative electrode mixture layer W5 Separator

Continued on front page F term (reference) 5H029 AJ14 AK03 AL07 AL08 AM01 BJ02 BJ14 CJ02 CJ07 CJ08 CJ22 CJ28 EJ12 HJ01 5H050 AA19 BA17 CA05 CB08 CB09 DA10 DA11 EA23 GA00 GA02 GA09 GA10 GA22 HA01

Claims (6)

[Claims] 1. A method for producing a non-aqueous electrolyte secondary battery having an electrode winding group soaked in a non-aqueous electrolyte, comprising a binder containing a lithium transition metal double oxide, a conductive material and an acrylic polymer. A positive electrode in a non-dried state in which a mixed positive electrode mixture is applied to a belt-shaped current collector, and a non-dried state in which a negative electrode mixture in which a binder containing a carbon material and an acrylic polymer is mixed is applied to a band-shaped current collector A negative electrode and a separator having microporosity through which lithium ions can pass are prepared, and the positive electrode and the negative electrode are wound through the separator to form an electrode winding group. The electrode winding group is heated under reduced pressure. Drying the non-aqueous electrolyte secondary battery. 2. A method for producing a non-aqueous electrolyte secondary battery having an electrode winding group soaked in a non-aqueous electrolyte, comprising: a positive electrode mixture obtained by mixing a lithium transition metal double oxide, a conductive material and a binder. A positive electrode in a dry state coated on a belt-shaped current collector, a negative electrode in a non-dried state coated with a negative electrode mixture obtained by mixing a binder containing amorphous carbon and an acrylic polymer, and a lithium ion Preparing a separator having a microporous through which the positive electrode and the negative electrode are wound, forming an electrode winding group by winding the positive electrode and the negative electrode through the separator, and drying the electrode winding group under reduced pressure heating, A method for producing a non-aqueous electrolyte secondary battery comprising: 3. A method for producing a non-aqueous electrolyte secondary battery having an electrode winding group soaked in a non-aqueous electrolyte, comprising a binder containing a lithium transition metal double oxide, a conductive material and an acrylic polymer. A non-dried positive electrode in which a mixed positive electrode mixture is applied to a belt-shaped current collector, a dry negative electrode in which a negative electrode mixture in which a carbon material and a binder are mixed is applied to a band-shaped current collector, and lithium ions pass through Preparing a separator having a possible microporosity, winding the positive electrode and the negative electrode through the separator to form an electrode winding group, and drying the electrode winding group under reduced pressure heating. A method for manufacturing a non-aqueous electrolyte secondary battery. 4. The method according to claim 1, wherein the water content of the positive electrode in the preparation step is 1000 ppm or more.
A method for producing the nonaqueous electrolyte secondary battery according to claim 3. 5. The method for producing a non-aqueous electrolyte secondary battery according to claim 1, wherein the water content of the negative electrode in the preparation step is 500 ppm or more. 6. The non-aqueous battery according to claim 1, wherein the water content of the positive electrode in the preparation step is 1000 ppm or more, and the water content of the negative electrode in the preparation step is 500 ppm or more. A method for producing a water electrolyte secondary battery.