WO2016114474A1 - Slurry composition for electrode, electrode, and secondary battery - Google Patents

Abstract

The present invention provides: a slurry composition for an electrode, comprising an electrode active material, a binder including a PVdF binder and an NBR binder, and a solvent; an electrode manufactured using the slurry composition for an electrode; and a secondary battery including the electrode.

Description

Slurry Composition for Electrodes, Electrodes and Secondary Batteries

The present invention relates to a slurry composition for an electrode, an electrode manufactured using the same, and a secondary battery including the electrode.

Recently, power storage devices having high voltage and high energy density have been demanded as power sources for driving electronic devices. In particular, lithium ion secondary batteries and lithium ion capacitors are expected as power storage devices having high voltage and high energy density.

The electrode used for such an electrical storage device is manufactured by apply | coating and drying the mixture of an electrode active material and the binder for electrodes to an electrical power collector. The characteristics required for such an electrode binder include increasing the binding properties between the active substance and between the electrode active material and the current collector, or the resistance of the active substance from the active material layer due to the scratch resistance in the step of winding the electrode, subsequent cutting, and the like. Separation resistance such as fine powder does not occur, reduction of internal resistance of the battery, and the like.

For example, when the slurry for lithium secondary battery electrodes is apply | coated to copper foil, an aluminum foil, etc., and an electrode for lithium ion secondary batteries is manufactured, N-methylolpi which is an organic solvent is generally used as a binder of the slurry for lithium secondary battery electrodes. Polyvinylidene fluoride (PVDF) using a ralidone (NMP) solvent, and styrene-butadiene rubber (SBR) which uses carboxymethylcellulose (CMC) together as a thickener are used.

The above-mentioned PVDF binder (for example, Japanese Patent No. 3966570) has low binding properties between electrode active materials and between electrode active materials and current collectors, and requires a large amount of binders for practical use, resulting in the use of lithium ion secondary batteries. There is a disadvantage that the capacity is lowered.

The SBR-based binder is used for a wide range of applications as a binder for an aqueous lithium ion secondary battery electrode in that the electrode active materials, the electrode active material, and the current collector can be bound together well (for example, Japanese Patent No.3562197). report). However, in the slurry in which the amount of binder used is reduced to increase the capacity of the battery, the electrode active materials and the electrode active material and the current collector cannot be bound well, and thus the charge and discharge cycle characteristics of the lithium ion secondary battery are deteriorated.

In particular, when forming the electrode pattern using the electrode slurry prepared using a conventional electrode binder, such as the PVDF binder or SBR-based binder, as shown in Figure 1, the drag line (Drag line 11) However, the balcony 10 is formed, which is a problem. When the drag line 11 occurs, safety problems such as an internal short circuit occur, and even when welding such as tab, the slurry hardens at a portion where the slurry should not be formed, which causes problems in welding. In addition, when the balcony 10 is formed, the balcony 10 causes capacity reduction due to thickness irregularity and taping of the battery.

[Preceding technical literature]

[Patent Documents]

Japanese Patent No. 3966570

Japanese Patent No. 3552397

The present invention has been made to solve the problems of the prior art as described above, the formation of the drag line (drag line) or balcony when forming the electrode pattern is minimized, resulting in short-circuit welding, such as tap, the thickness of the battery It is an object of the present invention to provide a slurry composition for electrodes, characterized in that the problem of capacity reduction due to unevenness and taping is minimized.

Moreover, an object of this invention is to provide the slurry composition for electrodes which is excellent in binding power between an electrode active material and between an electrode active material and an electrical power collector, and reduces the internal resistance of a battery.

In addition, an object of the present invention is to provide a secondary battery including the electrode, and the electrode to reduce the defective rate of the battery, improve the charge and discharge cycle characteristics and capacity characteristics of the battery by being manufactured using the slurry composition for the electrode. .

The present invention provides a slurry composition for electrodes comprising a binder comprising an electrode active material, a PVdF binder and an NBR binder, and a solvent.

The NBR binder may include 1 to 100 wt% of H-NBR binder based on the total weight of the NBR binder.

The PVdF binder and the NBR binder may be included in a weight ratio of 2: 8 to 8: 2.

The binder including the electrode active material, the PVdF binder, and the NBR binder may be included in a weight ratio of 9.0: 1.0 to 9.9: 0.1.

The electrode slurry composition may further include a conductive material.

The H-NBR binder may remain at 60 mol% or less of a double bond of NBR by hydrogenation.

The H-NBR may include 40 to 85% by weight of hydrogenated butadiene and 15 to 60% by weight of acrylonitrile based on the total weight of H-NBR.

The viscosity of the slurry composition for the electrode may be 4,000 to 30,000 cps.

The present invention also provides an electrode produced using the slurry composition for the electrode and a secondary battery comprising the electrode.

The electrode may include a binder including an electrode active material, a polyvinylidene fluoride (PVF) binder, and a nitrile butadiene rubber (NBR) binder.

The slurry composition for electrodes of the present invention includes an NBR binder, thereby minimizing the formation of a drag line or a balcony when forming an electrode pattern. It provides the effect of minimizing capacity reduction problem due to unevenness and taping.

In addition, the slurry composition for electrodes of the present invention provides an excellent binding force between the electrode active material and between the electrode active material and the current collector, and also provides an effect of reducing the internal resistance of the battery.

The electrode of the present invention is prepared using the slurry composition for the electrode to lower the defective rate of the battery, and provides an effect of improving the charge and discharge cycle characteristics and capacity characteristics of the battery.

The secondary battery of the present invention has a low defect rate by including the electrode, and is excellent in charge and discharge cycle characteristics and capacity characteristics.

FIG. 1 is a diagram schematically illustrating a drag line and a balcony generated when an electrode pattern is formed using a conventional slurry for electrodes. In FIG. 1, (a) is a plan view of the electrode pattern, (b) is an ideally coated side cross section of the electrode pattern, and (c) is an actual coated side cross section of the electrode pattern.

Figure 2 is a graph evaluating the characteristics of the lithium ion secondary battery (Example 1) manufactured using the electrode of the present invention.

3 is a graph evaluating the characteristics of a lithium ion secondary battery (Comparative Example 1) manufactured using a conventional electrode.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

The present invention relates to a binder composition comprising an electrode active material, a PVdF binder and an NBR binder, and a slurry composition for electrodes comprising a solvent.

The slurry composition for the electrode is not particularly limited as long as it is used for the production of the electrode, and may be used, for example, in secondary batteries such as lithium ion secondary batteries, storage batteries, and the like.

The PVdF binder refers to a binder including polyvinylidene fluoride or polyvinylidene difluoride as a binder generally used in the art.

The NBR (Nitrile Butadiene Rubber) binder refers to a binder including a copolymer of acrylonitrile and butadiene.

As the NBR binder used in the present invention, those known in the art may be used. In particular, the NBR binder is a concept including a H-NBR binder prepared by hydrogenation reaction to NBR.

The NBR binder may include 1 to 100 wt% of a H-NBR (Hydrogenated-Nitrile Butadiene Rubber) binder based on the total weight of the NBR binder, preferably 40 to 80 wt%. Since the general NBR binder has a higher resistance than the H-NBR binder, a general NBR binder and an H-NBR binder may be used in combination, or only an H-NBR binder may be selected and used.

The H-NBR binder used in the present invention may preferably be used to include H-NBR in which double bonds originally contained in the NBR remain at 60 mol% or less by hydrogenation.

The H-NBR may include 40 to 85% by weight of hydrogenated butadiene and 15 to 60% by weight of acrylonitrile, preferably 50 to 60% by weight of hydrogenated butadiene, based on the total weight of H-NBR. 75 wt% and acrylonitrile at 25-50 wt%.

When the content of the hydrogenated butadiene is less than 40% by weight based on the total weight of H-NBR, the resistance may be increased to decrease the capacity, and when the content of the hydrogenated butadiene is greater than 85% by weight, the adhesion with the current collector may be reduced.

In the slurry composition for electrodes of the present invention, the PVdF binder and the NBR binder are preferably contained in a weight ratio of 2: 8 to 8: 2, more preferably 2: 8 to 3: 7.

In the case where the PVdF binder is insufficiently included outside the above range, the loading variation may be increased during the electrode coating process, and the fairness may be worsened. When the PVdF binder is included in the above range, the loading variation may be increased during the electrode coating process. And the adhesion with the current collector can be lowered.

In addition, when the NBR binder is out of the above range, the performance of the lithium ion secondary battery may be degraded.

The electrode active material used in the slurry composition for electrodes of this invention is not specifically limited, It can select suitably according to the kind of battery and a capacitor. For example, a lithium ion secondary battery positive electrode active material is, for example, LiCoO _2, LiNiO _2, lithium-containing composite metal oxides such as LiMnO _2, LiMn ₂ O _4; Transition metal sulfides such as TiS ₂ , TiS ₃ , and amorphous MoS ₃ ; Transition metal oxides such as Cu ₂ V ₂ O ₃ , amorphous V ₂ OP ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O _13, and the like.

Examples of the negative electrode active material include amorphous carbon, graphite, natural graphite, carbonaceous materials such as mesocarbon microbeads (MCMB) and pitch-based carbon fibers, conductive polymers such as polyacene, and the like.

In the slurry composition for electrodes of the present invention, a binder including an electrode active material, a PVdF binder, and an NBR binder may be included in a weight ratio of 9.0: 1.0 to 9.9: 0.1. When the content of the binder exceeds the above range, the charge / discharge performance and capacity of the device using the electrode may decrease, and when the content of the binder is less than the above range, a problem of insufficient binding force of the electrode may occur.

In the slurry composition for electrodes of the present invention, the solvent is not particularly limited as long as it can dissolve the PVdF binder and the NBR binder, and those known in the art may be used. For example, amides such as N-methylpyrrolidone, N, N-dimethylacetoamide, and N, N-dimethylformamide may be used, and among these, N-methylpyrrolidone may be applied to a current collector. Since it is good, it can be used preferably.

The amount of the solvent used may be determined to be a viscosity suitable for coating depending on the type of the electrode active material, the binder, and the conductive material described later. For example, the concentration of the solid content of the electrode active material, the binder, and the conductive material described later may be adjusted to 50 to 95% by weight, more preferably 70 to 90% by weight.

The slurry composition for electrodes of the present invention may further include a conductive material. The conductive material is not particularly limited and may be appropriately selected according to the type of battery and capacitor. For example, in the case of a lithium ion secondary battery, carbon such as graphite and activated carbon may be used. In the case of a nickel hydrogen secondary battery, cobalt oxide may be used, and in the negative electrode, nickel powder, cobalt oxide, titanium oxide, and carbon may be used.

Examples of the carbon include acetylene black, furnace black, graphite, carbon fiber, and fullerenes.

The amount of the conductive material is usually 1 to 20 parts by weight, preferably 2 to 10 parts by weight based on 100 parts by weight of the electrode active material.

Viscosity modifiers, glidants, etc. may be further added to the slurry composition for electrodes as needed.

The viscosity of the slurry composition for the electrode may be 4,000 to 30,000 cps, preferably 8000 to 19000 cps. When the viscosity of the slurry composition for the electrode is less than 4,000 cps, high loading of the slurry for the electrode may be difficult, and when the viscosity of the electrode composition exceeds 30,000 cps, the coating of the slurry for the electrode may be uneven.

The slurry composition for electrodes of the present invention can be prepared by mixing the above components by methods known in the art.

Moreover, this invention relates to the electrode manufactured using the said slurry composition for electrodes. Accordingly, the electrode may include a binder including an electrode active material, a polyvinylidene fluoride (PVDF) binder, and a nitrile butadiene rubber (NBR) binder.

The electrode can be prepared by a method known in the art. That is, the electrode of the present invention can be prepared by applying the slurry composition for electrode of the present invention to a current collector and drying it. The coating method to the collector of the said slurry composition for electrodes is not specifically limited. For example, methods, such as a doctor blade method, a dip method, the reverse roll method, the direct roll method, the gravure method, the extrusion method, the brush coating method, are mentioned. The amount of the slurry to be applied is also not particularly limited, but an amount such that a mixed layer made of an active material, a binder, and the like formed after drying and removing the liquid medium is usually 0.005 to 5 mm, preferably 0.01 to 2 mm is common. The drying method is not particularly limited, and examples thereof include drying by warm air, hot air and low humidity, vacuum drying, and drying by irradiation of (far) infrared rays and electron beams. The drying rate is usually adjusted so that the liquid medium can be removed as soon as possible within a speed range such that cracks do not form in the mixed layer due to stress concentration or the mixed layer does not peel off from the current collector.

In addition, the density of the active material of the electrode can be increased by pressing the current collector after drying. As a press method, methods, such as a metal mold | die press and a roll press, are mentioned.

The current collector is not particularly limited as long as it is made of a conductive material. For example, in the case of a lithium ion secondary battery, one made of metal such as iron, copper, aluminum, nickel, stainless, or the like may be used.

The present invention also relates to a secondary battery comprising the electrode.

In the secondary battery, other components and manufacturing methods except those using the electrode for the negative electrode and / or the positive electrode may be used without limitation those known in the art. That is, the secondary battery of the present invention includes the electrode and the electrolyte and can be manufactured according to a known method using a component such as a separator. Therefore, description thereof will be omitted.

Hereinafter, preferred embodiments will be presented to aid in understanding the invention. However, the following examples are only to illustrate the invention, not limited to the invention only.

Preparation Example: Fabrication of Li-ion Secondary Battery

(Example 1)

1) Preparation of Anode

As a cathode active material, LiCoO _{2 ,} PVdF (trade name: KF1100, manufacturer: Kureha), and H-NBR (brand name: BM-730H, manufacturer: zeon) were mixed in a weight ratio of 8: 2, and acetylene black was used as a conductive material. After the slurry was prepared by mixing with N-methylpyrrolidone in a weight ratio of 2: 2, a slurry was applied to an aluminum (Al) foil current collector using a slot die coater, and dried to prepare a positive electrode.

2) Preparation of Cathode

Artificial graphite, CMC (brand name: BG-L01, manufacturer: GEL Chem), SBR (brand name: BM-L301, manufacturer: zeon) as a negative electrode active material, acetylene black as a conductive material in a weight ratio of 95: 2: 1: 1 A slurry was prepared by mixing with methylpyrrolidone and then applied to a copper (Cu) foil current collector using a commacoater to prepare a negative electrode.

3) Manufacture of Lithium Ion Secondary Battery

A stack-type electrode assembly prepared by interposing a polyethylene porous membrane between the positive electrode and the negative electrode prepared above was introduced into a pouch-type battery case, and 3.0M LiTFSI (lithium trifluoromethanesulfonimide, Li (N (SO ₂ CF ₃ ) ₂ ) and DME (dimethoxyethane): DOL (dioxolane) = 1: 1 was injected to prepare a pouch type lithium ion secondary battery.

(Comparative Example 1)

1) Preparation of Anode

A positive electrode was manufactured in the same manner as in Example 1, except that only a PVdF (trade name: KF1100, manufacturer: Kureha) binder was used as the binder.

2) Preparation of Cathode

A negative electrode was prepared in the same manner as in Example 1.

3) Manufacture of Lithium Ion Secondary Battery

A stack-type electrode assembly prepared by interposing a polyethylene porous membrane between the positive electrode and the negative electrode prepared above was introduced into a pouch-type battery case, and 1.0M LiTFSI (lithium trifluoromethanesulfonimide, Li (N (SO ₂ CF ₃ ) ₂ ) and DME (dimethoxyethane): DOL (dioxolane) = 1: 1 was injected to prepare a pouch type lithium ion secondary battery.

(Comparative Example 2)

1) Preparation of Anode

Of LiCoO _2, a binder of the water-based positive electrode as the positive electrode active material, SBR (trade name: BM-L301, Manufacturer: zeon) binder, CMC (trade name: BG-L01, Manufacturer: GL-Chem), the conductive material, acetylene black 96 as: 2: 1 A slurry was prepared by mixing with N-methylpyrrolidone in a weight ratio of 1, and then applied to an aluminum (Al) foil current collector using a slot die coater, followed by drying to prepare a positive electrode.

2) Preparation of Cathode

A negative electrode was prepared in the same manner as in Example 1.

3) Manufacture of Lithium Ion Secondary Battery

A stack-type electrode assembly prepared by interposing a polyethylene porous membrane between the positive electrode and the negative electrode prepared above was introduced into a pouch-type battery case, and 3.0M LiTFSI (lithium trifluoromethanesulfonimide, Li (N (SO ₂ CF ₃ ) ₂ ) and DME (dimethoxyethane): DOL (dioxolane) = 1: 1 was injected to prepare a pouch type lithium ion secondary battery.

Test Example 1: Evaluation of Appearance of Electrode

Visually the appearance of the electrodes prepared in Examples and Comparative Examples Evaluated. As a result, a drag line or a balcony did not occur in the electrodes of the example, but the occurrence of a drag line and a balcony was observed in the electrodes of the comparative example.

A scanning electron microscope (SEM) image of the anode prepared in Example 1 is shown in FIG. 2 of Korean Patent Application No. 10-2015-0006905 (filed date: January 14, 2015) of the present invention. As confirmed in the photograph, it was confirmed that no drag line occurred in the anode of Example 1.

A scanning electron microscope (SEM) image of the anode prepared in Comparative Example 1 is shown in FIG. 3 of Korean Patent Application No. 10-2015-0006905 (Application Date: January 14, 2015), which is the original application of the present invention. As confirmed in the above photograph, a drag line was confirmed at the anode of Comparative Example 1.

An image photographing the appearance of the anode of Comparative Example 2 is shown in FIG. 4 of Korean Patent Application No. 10-2015-0006905 (Application Date: January 14, 2015), which is the original application of the present invention. As can be seen in the photo, in the positive electrode of Comparative Example 2, grains occurred during mixing and line defects occurred during coating.

Test Example 2: Performance Evaluation of Lithium Ion Secondary Battery

The discharge capacity was measured to confirm the performance of the batteries produced in the above Examples and Comparative Examples. The charge was charged at room temperature with CC / CV C-rate 0.5C 4.2V, 1 / 20C cut-off and the discharge was cut 2.5V with room temperature CC 0.2C. The results are shown in FIGS. 2 and 3.

As confirmed in FIG. 2 (cell of Example 1) and FIG. 3 (cell of Comparative Example 1), the batteries prepared in Example 1 and Comparative Example 1 did not show any particular difference in performance. These results indicate that the NBR binder further added as a binder in the manufacture of the electrode in the present invention does not adversely affect the performance of the battery.

In the case of Comparative Example 2, granules were generated during mixing and line defects occurred during coating, and thus, the discharge capacity was not measured.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

The present invention relates to a slurry composition for an electrode, an electrode prepared using the same, and a secondary battery including the electrode, wherein the slurry composition for the electrode includes an electrode active material, a polyvinylidene fluoride (PVDF) binder, and a nitrile butadiene rubber (NBR) binder. It includes.

The slurry composition for the electrode includes an NBR binder, thereby minimizing the formation of a drag line or a balcony when forming an electrode pattern, such as an internal short circuit due to the drag line or a balcony, difficulty in welding such as a tap, uneven thickness of a battery, and the like. It minimizes the capacity reduction problem caused by taping.

Claims (11)

1. Slurry composition for electrodes comprising an electrode active material, a polyvinylidene fluoride (PVD) binder and a Nitrile Butadiene Rubber (NBR) binder, and a solvent.
2. The method of claim 1,

   The NBR binder is a slurry composition for an electrode containing 1 to 100% by weight of H-NBR binder based on the total weight of the NBR binder.
3. The method of claim 1,

   The PVdF binder and NBR binder is a slurry composition for an electrode is included in a weight ratio of 2: 8 to 8: 2.
4. The method of claim 1,

   A binder comprising an electrode active material, a PVdF binder, and an NBR binder is included in a weight ratio of 9.0: 1.0 to 9.9: 0.1.
5. The method of claim 1,

   Slurry composition for electrodes that the electrode composition further comprises a conductive material.
6. The method of claim 2,

   The H-NBR binder has 60 double bonds of NBR by hydrogenation. Slurry composition for electrodes remaining in mol% or less.
7. The method of claim 2,

   The H-NBR is a slurry composition for an electrode comprising 40 to 85% by weight of hydrogenated butadiene (hydrogenated buradiene) and 15 to 60% by weight of acrylonitrile relative to the total weight of the H-NBR.
8. The method of claim 1,

   The viscosity of the slurry composition for electrodes is 4,000 to 30,000cps slurry composition for electrodes.
9. The electrode manufactured using the slurry composition for electrodes of any one of Claims 1-8.
10. The method of claim 9,

    The electrode is an electrode active material, and

    An electrode comprising a binder comprising a polyvinylidene fluoride (PVDF) binder and a Nitrile Butadiene Rubber (NBR) binder.
11. A secondary battery comprising the electrode of claim 9.

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