KR101103198B1 - A forming method of electrode active material layer of a secondary battery developing dispersibility of electroconductive particles - Google Patents

Abstract

The present invention relates to a method for forming an electrode active material layer of a secondary battery having improved dispersibility of conductive particles. In the method of forming an electrode active material layer of a secondary battery according to the present invention, the conductive particles are dispersed in a melt of the binder resin (S1), and the master batch binder resin-conductive composite chip in which the conductive agents are dispersed in the binder resin. (S2) dispersing the master batch binder resin-conductor composite chips and the electrode active material particles in a solvent, and then dissolving the binder resin of the composite chips in the solvent to prepare an electrode active material slurry; S3) applying and drying the electrode active material slurry on the substrate. According to the forming method of the present invention, the binder resin is dissolved in the state in which the master batch binder resin-conductive composite chips are dispersed in the electrode active material slurry, and the conductive particles dispersed therein are released in the slurry, An electrode active material slurry having improved dispersibility of conductive particles may be prepared. Accordingly, since the conductive particles are uniformly dispersed in the electrode active material layer formed using the electrode active material slurry, the ion conductivity of the electrode can be maintained uniformly.

Description

A method of forming an electrode active material layer of a secondary battery having improved dispersibility of conductive particles {A FORMING METHOD OF ELECTRODE ACTIVE MATERIAL LAYER OF A SECONDARY BATTERY DEVELOPING DISPERSIBILITY OF ELECTROCONDUCTIVE PARTICLES}

The present invention relates to a method for forming an electrode active material layer of a secondary battery having improved dispersibility of conductive particles.

In general, rechargeable batteries capable of charging and discharging are being actively researched by developing portable electronic devices such as cellular phones, notebook computers, and camcorders. Examples of such secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-hydrogen batteries, and lithium secondary batteries. Among them, lithium secondary batteries are considered the most promising and have high future prospects because they have superior operating voltage characteristics and energy density per unit weight compared to nickel-cadmium batteries or nickel-metal hydride batteries, which are widely used as power sources for electronic devices. .

The lithium secondary battery may be manufactured in various forms, and typical shapes include cylindrical and rectangular shapes mainly used in lithium ion batteries. Lithium polymer batteries, which are in the spotlight in recent years, are made of flexible materials and their shapes are relatively free. In addition, since the safety and light weight is excellent, it can be said that it is advantageous to slim and lighten portable electronic devices.

A lithium secondary battery typically includes a positive electrode having a positive electrode active material layer formed on at least one surface of a positive electrode current collector, a negative electrode having a negative electrode active material layer formed on at least one surface of a negative electrode current collector, and interposed between the positive electrode and the negative electrode to electrically insulate them. A separator is provided. The electrode (anode or cathode) active material layer may be formed by applying and drying the electrode active material slurry in which the electrode active material particles, the conductive agent particles, and the binder resin are dispersed in a solvent to the current collector, or the electrode active material. The slurry is applied and dried on top of a separate support, and then a film peeled from the support is formed by lamination onto a current collector.

In the above-described method of forming an electrode active material, the ion conductivity of the formed electrode active material layer is uniformly maintained only when the conductive particles are well dispersed in the electrode active material slurry. However, in the case of using a conventional dispersing method in which the electrode active material particles, the conductive agent and the binder resin are added to the solvent at the same time and stirred and dispersed in the mixer, due to differences in particle sizes and specific gravity of the electrode active material particles and the conductive agent, The conductive particles are difficult to uniformly disperse in the slurry.

In order to improve this problem, Japanese Laid-Open Patent Publication No. 2003-173777 discloses a method of spray drying the electrode active material slurry, and then adding a solvent and kneading the mixture, followed by coating and drying the current collector to form an electrode active material layer. Is disclosed. In addition, Korean Unexamined Patent Application Publication No. 2000-6809 discloses a method of improving dispersibility of electrode active material and conductive particles in an electrode active material slurry through a specially designed dispersing device. However, these manufacturing methods require a special dispersing apparatus or are cumbersome in manufacturing process, and there is a limit in improving the dispersibility of the conductive particles in the electrode active material slurry.

The technical problem to be achieved by the present invention is to solve the above-described problems, to provide a method for forming an electrode active material layer of a secondary battery that improves the dispersibility of the conductive particles in a relatively simple method.

In order to achieve the above technical problem, a method of forming an electrode active material layer of a secondary battery according to the present invention includes dispersing conductive agent particles in a melt of a (S1) binder resin, thereby dispersing the conductive particles in the binder resin. Preparing Batch Binder Resin-Conductor Composite Chips (S2) Dispersing the Master Batch Resin-Conductor Composite Chips and Electrode Active Material Particles in a Solvent, Dissolving the Binder Resin of the Composite Chips in the Solvent Preparing an electrode active material slurry and (S3) applying and drying the electrode active material slurry on a substrate.

In the method for forming an electrode active material layer of the secondary battery of the present invention, the conductive content of the master batch binder resin-conductor composite chip is preferably 10 to 80% by weight, and the master batch type binder resin-conductor composite chip The average diameter is preferably 0.1 to 10 mm.

According to the present invention, the master batch binder resin-conductor composite chips in which the conductive particles are dispersed in advance are dispersed in a solvent together with the electrode active material particles, and then the binder resin of the composite chips is dissolved in a solvent to prepare an electrode active material slurry. As the binder resin constituting the composite chip is dissolved and the conductive particles dispersed therein are released in the slurry, an electrode active material slurry having improved dispersibility of the conductive particles can be manufactured. Accordingly, since the conductive particles are uniformly dispersed in the electrode active material layer formed using the electrode active material slurry, the ion conductivity of the electrode can be maintained uniformly.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the present invention. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to explain their own invention in the best way. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

The present invention is a method for forming an electrode active material layer using a conventional electrode active material slurry consisting of a binder resin, electrode active material particles, conductive particles and a solvent, the master batch binder resin in which the conductive particles are previously dispersed in the binder resin It is characterized by the use of conductive composite chips.

That is, as shown in FIG. 1, the master batch binder resin-conductor composite chip 10 according to the present invention added to the electrode active material slurry has a plurality of conductive particles 5 inside the polymer resin 3. Is dispersed. When the master batch binder resin-conductor composite chips are dispersed in a solvent together with the electrode active material particles, the binder resins of the composite chips are dissolved in a solvent to prepare an electrode active material slurry, and the binder resin constituting the composite chip is dissolved. At the same time, the conductive particles dispersed therein are released in the slurry, thereby making it possible to prepare an electrode active material slurry having improved dispersibility of the conductive particles.

The electrode active material layer forming method of the secondary battery according to the present invention will be described in detail as follows.

First, the conductive particles are dispersed in the melt of the binder resin to prepare master batch type binder resin-conductive composite chips in which the conductive particles are dispersed in the binder resin (step S1). That is, the binder resin is heated to melt above the melting point and melted, and then the conductive particles are dispersed in the melt of the binder resin by adding and stirring the conductive particles therein. The binder resin melt in which the conductive particles are dispersed may be manufactured into a cylindrical chip having a predetermined size and shape, for example, an average diameter of 0.1 to 10 mm, using a conventional chip manufacturing method such as cutting after extrusion. The shape, size, and manufacturing method thereof can be variously selected by those skilled in the art within the scope of achieving the object of the present invention.

In the formation method of the present invention, any of the conventional conductive agents used in the electrode active material layer of the secondary battery may be used as the conductive agent used in the production of the master batch binder resin-conductive composite chip. For example, acetylene black, Carbon black, Ketjen black, graphite, etc. can be used individually or in combination of 2 or more types, respectively. The content of the conductive particles in the master batch binder resin-conductive composite chip can be controlled within a content range in which the conductive particles can be sufficiently dispersed in the binder resin, for example, 10 to 80 weight based on the total weight of the chip. % Can be added.

As the binder resin used to prepare the master batch binder resin-conductor composite chip, any thermoplastic binder resin commonly used as a binder of the electrode active material particles may be used. For example, polyvinylidene fluoride and vinylidene fluoride may be used. Hexafluoropropylene copolymer, polyvinylidene fluoride, polyurethane, polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polyacrylamide, polyacetate and the like can be used alone or in combination of two or more thereof. have.

Subsequently, the master batch binder resin-conductor composite chips and the electrode active material particles are dispersed in a solvent, and the binder resin of the composite chips is dissolved in the solvent to prepare an electrode active material slurry (step S2).

The method for dispersing the master batch binder resin-conductor composite chips and the electrode active material particles in a solvent may use various dispersion methods such as a dispersion method using a conventional mixer. The master batch binder resin-conductor composite chips dispersed in a solvent together with other components are dissolved in a solvent with a binder resin constituting the composite chip over time or by heating to prepare an electrode active material slurry. As a solvent, any solvent can be used as long as it is used to form an electrode active material slurry and can dissolve the binder resin. For example, acetone or N-methyl pyrrolidone (NMP) may be used.

In addition to the master batch binder resin-conductive composite chips, the binder active material and the conductive particles may be separately added to the electrode active material slurry without departing from the object of the present invention according to a conventional method. The content of the total conductive particles in the electrode active material slurry including the conductive particles contained in the master batch binder resin-conductive composite chips can be controlled according to the conductive content in the electrode active material layer which is typically formed. It may be added to 1 to 20 parts by weight based on 100 parts by weight of the active material particles. In addition, the content of the total binder resin in the electrode active material slurry including the binder resin contained in the master batch binder resin-conductor composite chips may be adjusted according to the content of the binder resin in the electrode active material layer that is typically formed. It may be added to 5 to 30 parts by weight based on 100 parts by weight of the electrode active material particles.

Then, the electrode active material slurry prepared by the method described above is applied on a substrate and dried to form an electrode active material layer (step S3). The electrode active material layer is formed by directly applying it onto a substrate made of a current collector, such as a metal thin film, a mesh-type suspended metal, or a punched metal, and then drying, or a slurry of the electrode active material as a separate support such as a polyethylene terephthalate film. After coating and drying on the substrate, the film peeled from the support may be formed by laminating on a current collector or the like. As the coating method of the electrode active material slurry, a conventional coating method known in the art may be used, and for example, dip coating, die coating, roll coating, comma coating or the like Various methods, such as a mixing method, can be used.

In the electrode active material layer forming method of the present invention, the electrode active material particles are not particularly limited, and conventional electrode active material particles known in the art may be used.

Non-limiting examples of the positive electrode active material particles of the electrode active material particles may be particles of lithium composite oxides such as lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide or the like particles of the sulfur compound, negative electrode active material Non-limiting examples of particles may include lithium metal or lithium alloys, carbon, petroleum coke, activated carbon, lithium adsorbents such as graphite (graphite) and the like.

Hereinafter, examples will be described in order to describe the present invention in more detail. However, embodiments according to the present invention can be modified in many different forms, the scope of the present invention should not be construed as limited by the embodiments described below. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

<Examples>

100 parts by weight of carbon black was added to 100 parts by weight of the molten polyvinylidene fluoride heated and molten, followed by stirring to disperse the conductive particles, followed by melt extrusion and cutting to obtain a cylindrical master batch binder resin having an average diameter of 3 mm. Conductor composite chips were prepared.

Then, 4 parts by weight of the prepared master batch binder resin-conductive composite chip and 92 parts by weight of the positive electrode active material particles of the lithium cobalt composite oxide, and 4 parts by weight of the total amount of the binder resin and the conductive particles in the slurry were separately Vinylidene fluoride and carbon black were added to N-methyl-2 pyrrolidone (NMP) to disperse, and then heated and stirred to dissolve polyvinylidene fluoride in a solvent to prepare a positive electrode active material slurry. The above-described positive electrode active material slurry was coated and dried on a thin film of aluminum (Al) of a positive electrode current collector having a thickness of 20 μm to form a positive electrode active material layer, and then roll press was performed.

Comparative Example

A master batch-type binder resin-conductor composite chip was prepared in the same manner as in Example, except that the content of the binder resin and the conductive agent was adjusted instead of the chip.

As a result of evaluating the dispersibility of the conductive particles in the positive electrode active material layer prepared according to the above-described Examples and Comparative Examples, it was found that the Example is superior to the comparative example.

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate the presently preferred embodiments of the invention and, together with the description of the following preferred embodiments, serve to explain the principles of the invention.

1 is a schematic cross-sectional view of a master batch binder resin-conductive composite chip used in the method of forming an electrode active material layer of the present invention.

Claims (10)

(S1) dispersing the conductive particles in a melt of the binder resin to prepare the master batch binder resin-conductive composite chips having an average diameter of 0.1 to 10 mm, in which the conductive particles are dispersed in the binder resin. ; (S2) dispersing the master batch binder resin-conductor composite chips and electrode active material particles in a solvent, and then dissolving the binder resin of the composite chips in the solvent to prepare an electrode active material slurry; (S3) A method of forming an electrode active material layer of a secondary battery comprising applying and drying the electrode active material slurry on a substrate. The method of claim 1, The method of forming the electrode active material layer of the secondary battery, characterized in that the content of the conductive particles of the master batch binder resin-conductor composite chip is 10 to 80% by weight. The method according to claim 1 or 2, The binder resin is polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, polyurethane, polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polyacrylamide and poly Method of forming an electrode active material layer of a secondary battery, characterized in that any one selected from the group consisting of acetate or a mixture of two or more thereof. The method according to claim 1 or 2, The conductive agent is any one selected from the group consisting of acetylene black, carbon black, Ketjen black, graphite, and mixtures thereof. delete The method according to claim 1 or 2, The electrode active material particle is a method of forming an electrode active material layer of a secondary battery, characterized in that the positive electrode active material of a lithium composite oxide or a sulfur compound. The method according to claim 1 or 2, The electrode active material particles are any one of the negative electrode active material selected from the group consisting of lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, and graphite. Formation method of the active material layer. The method according to claim 1 or 2, The solvent is acetone or N-methyl pyrrolidone (NMP) characterized in that the electrode active material layer forming method of a secondary battery. The method according to claim 1 or 2, The content of the conductive particles of the electrode active material layer is a method for forming an electrode active material layer of a secondary battery, characterized in that 1 to 20 parts by weight based on 100 parts by weight of the electrode active material particles. The method according to claim 1 or 2, The binder resin content of the electrode active material layer is a method for forming an electrode active material layer of a secondary battery, characterized in that 5 to 30 parts by weight based on 100 parts by weight of the electrode active material particles.

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