KR20180015707A - Powder comprising surface coating layer, Electrode using the same and Manufacturing method thereof - Google Patents

Abstract

A particle coated with a dopamine-based polymer and an electrode containing the same of the present invention have the effect of providing high binding force with a binder and high conductivity by excluding self-polymerized dopamine polymer particles. The electrode for a secondary battery of the present invention does not contain self-polymerized dopamine polymer particles having an average size of 50 to 600 nm, and contains conductive particles coated with a dopamine-based polymer or active material particles coated with a dopamine-based polymer.

Description

TECHNICAL FIELD The present invention relates to a particle coated with a dopamine polymer, a particle layer containing the same, an electrode including the particle layer, and a method of manufacturing the same.

TECHNICAL FIELD The present invention relates to particles coated with a dopamine polymer, a particle layer containing the same, an electrode including the same, and a method of manufacturing the same.

Recently, the lithium secondary battery market is gradually evolving into the large-sized battery market in the conventional small battery industry. Accordingly, the importance of medium and large-sized batteries such as electric vehicles and energy storage systems is growing, and a lot of research is being conducted to satisfy the electrochemical characteristics required thereof.

The characteristics such as lifetime, capacity, stability, and energy density of the battery according to the number of charging / discharging are essential elements for realizing a large-sized battery. Particularly, when the battery is applied to a large-sized battery such as an energy storage system, deterioration of battery life characteristics due to repetitive charging / discharging is a big disadvantage compared to an internal combustion engine. The internal combustion engine has a theoretical reversible lifetime, whereas the battery used in the energy storage system has a irreversible disadvantage that the lifetime decreases as the number of times of charge / discharge increases. .

One of the main causes of deterioration of battery lifetime characteristics is deterioration of electrodes. The electrode breaks down due to the deterioration of the electrode structure, and the electrolyte is decomposed by the reaction with the exposed electrode, which results in a decrease in the electrolytic solution, thereby deteriorating the life characteristics. Therefore, in order to minimize deterioration of the life characteristics of the battery, it is necessary to overcome the deterioration phenomenon of the electrode to prevent the breakdown of the electrode structure and decomposition of the electrolyte.

As a means for overcoming the deterioration phenomenon of the electrode, a binder is used. However, as lithium ions are repeatedly inserted into and detached from the active material due to charging / discharging, the initial bonding ability of the binder is lowered and the structure of the electrode is collapsed.

In order to prevent this, studies have been actively conducted to overcome the deterioration phenomenon of the electrode by increasing the binding force inside the electrode. For example, when a polymer layer that increases binding force with a binder is formed on the surface of the negative electrode active material, the structure collapse of the electrode due to the deterioration phenomenon can be minimized and long life characteristics of the battery can be realized.

Korean Patent No. 10-1190364 discloses a technique for increasing the hydrophilicity of a cathode by coating a negative electrode active material with a dopamine-based monomer by an immersion method. This is because the conventional aging process for inducing the electrolyte wetting to the negative electrode is not accompanied, and thus the electrode and the secondary battery including the electrode can be manufactured in a shorter time.

However, it is difficult to separate and remove the dopant polymer particles generated by the polymerization between the monomers in the immersion coating, so that the internal resistance of the electrode is increased and it is difficult to expect the long life characteristics of the battery. This is because the non-conductive polymer is present in the inside of the electrode in the form of particles, and in this case acts as an element that interferes with the electron flow of the electrode.

Therefore, it is necessary to develop a technique for eliminating or eliminating the generation of the dopamine polymer particles, which is inevitably generated when the dopamine monomer is coated, which can improve the wettability and increase the binding force with the binder.

Korean Patent No. 10-1190364

It is an object of the present invention to provide a dopamine polymer layer on the surface of a particle to improve the binding force inside the electrode to reduce the deterioration phenomenon and minimize the generation of autopolymerized dopamine polymer particles generated in the coating process, Which is capable of minimizing the problem of adversely affecting the operation of a battery due to the presence of a dopamine polymer, an electrode including the dopamine polymer, and a method for producing the same.

It is therefore an object of the present invention to provide a method of controlling the generation of dopamine polymer particles in a coating process.

Accordingly, it is an object of the present invention to provide a secondary battery and a method of manufacturing the same, in which the lifetime characteristics of the battery are remarkably improved according to the number of charge / discharge cycles.

It is also an object of the present invention to provide a method for minimizing the problem of the generation of dopamine polymer particles in a coating process.

The present invention provides a particle coated with a dopamine polymer, an electrode including the same, a secondary battery comprising the same, and a method of manufacturing the same.

A method for producing a conductive particle or an active material particle coated with a dopamine polymer according to an embodiment of the present invention includes the steps of: a) coating a solution containing a dopamine monomer on a conductive particle or an active material particle immediately followed by filtration under reduced pressure, and b) And surface-polymerizing conductive particles or active material particles on which dopamine monomers are formed on the surface obtained through filtration.

In one embodiment of the present invention, the coating of step a) may be carried out in an instant dispersion.

In one embodiment of the present invention, the contact time between the solution and the conductive particles or the active material particles during the instant dispersion may be 3 minutes, preferably 30 seconds or less.

In one embodiment of the present invention, the reduced pressure filtration in step a) may be for removing a solution containing excess dopamine-based monomer.

In one example of the present invention, the average thickness of the dopamine-based polymer layer may be 1 nm or less, specifically 0.0001.

The electrode for a secondary battery according to an embodiment of the present invention includes conductive particles or active material particles coated with a dopamine polymer, but does not include self-cured polydopamine particles.

Here, the meaning of " not containing self-polymerizing dopamine polymer particles " means substantially not containing self-polymerizing dopamine polymer particles. For example, an electrode for a secondary battery according to one aspect of the present invention means substantially free of autopolymerized dopamine polymer particles having an average size of 50 to 600 nm, which is inevitably produced by a conventional coating method.

In one example of the present invention, the conductive particles are not particularly limited and may be, for example, carbon-based conductive particles.

In one embodiment of the present invention, the carbon-based conductive particles are not limited to a great extent, and examples thereof include carbon black; Acetylene black; Ketjen Black; Furnace black; Oil-furnace black; Channel black; Lamp black; Summer Black; Columbia carbon; Carbon fiber; Graphene; Graphite; And mixed conductive particles comprising a carbon-based conductive material; , And the like.

The present invention also provides a method for minimizing the formation of autopolymerized dopamine polymer particles in a coating process.

The particle coated with the dopamine polymer of the present invention, the particle layer containing the same, and the electrode including the same can form a dopamine polymer layer on the surface of the particle, thereby improving the binding force inside the electrode, thereby reducing the deterioration phenomenon. The generation of self-polymerized dopamine polymer particles is minimized, thereby minimizing the problem of adversely affecting battery operation due to resistance.

Further, the method of forming the dopamine polymer layer of the present invention on the surface of the particles has the effect of controlling the generation of the dopamine polymer particles in the coating process.

Accordingly, the secondary battery including the electrode has an effect of significantly improving lifetime characteristics of the battery according to the number of charge / discharge cycles.

On the other hand, even if the effects are not explicitly mentioned here, the effects described in the following specification, which are expected by the technical features of the present invention, and the provisional effects thereof are handled as described in the specification of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram showing conductive particles coated with a dopamine polymer. Fig.
Fig. 2 is an image showing an example of a process for producing a conductive particle coated with a dopamine based polymer according to Example 1 (coating O conductive material (shower coating)). In FIG. 2, the left side is an image of one example of the reduced pressure filtration process, and the right side is an image of the surface polymerization process in which the conductive particles separated from the reduced pressure filtration are dried at room temperature.
3 is a graph showing the results of measurement of the conductive particles according to Comparative Example 1 (Coating X conductive material) and Example 1 using a scanning electron microscope (SEM) and an X-ray photoelectron spectroscopy (XPS) . In Fig. 3, the image and the graph on the left are data on the conductive particles of Comparative Example 1, and the image on the right and the graph are the data on the conductive particles coated with the dopamine polymer of Example 1. Fig.
4 is an image showing the results of water dispersion test of the conductive particles (left side) according to Comparative Example 1 and the conductive particles (right side) coated with the dopamine polymer according to Example 1. Fig.
FIG. 5 is a graph showing the results of measuring the internal adhesion force of the electrodes according to Comparative Example 1 and Example 1 using a surface and interfacial cutting analysis system (SAICAS).
6 is a graph showing the results of measuring the life characteristics of Comparative Example 1 and Comparative Example 2 (Coating O conductive material (immersion coating)) and the electrode according to Example 1. Fig.
7 is a graph showing the results of measurement of electrical conductivity characteristics of electrodes according to Comparative Example 1, Comparative Example 2 and Example 1. Fig.
The image on the left side of FIG. 8 shows the result of measurement by Scanning Electron Microscope (SEM) according to Comparative Example 2, and the image on the right side of FIG. 8 shows a self-polymerization And the result of measuring the dopamine polymer particles with a scanning electron microscope.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

The drawings described in the present invention are provided by way of example so that a person skilled in the art can sufficiently convey the idea of the present invention. Therefore, the present invention is not limited to the illustrated drawings, but may be embodied in other forms, and the drawings may be exaggerated in order to clarify the spirit of the present invention.

In addition, unless otherwise defined, technical terms and scientific terms used in the present invention have the same meanings as those of ordinary skill in the art to which the present invention belongs. In the following description and the accompanying drawings, Description of known functions and configurations that may unnecessarily obscure the subject matter will be omitted.

Also, units of% used unclearly in the present invention means weight percent.

The present invention provides a conductive particle or an active material particle coated with a dopamine polymer substantially free from self-polymerized dopamine polymer particles, an electrode including the same, a secondary battery comprising the same, and a method of manufacturing the same.

Here, the meaning of " not containing self-polymerizing dopamine polymer particles " means substantially not containing self-polymerizing dopamine polymer particles. For example, the secondary battery according to an embodiment of the present invention means that substantially no self-polymerized dopamine polymer particles having an average size of 50 to 600 nm, which are inevitably produced by a conventional coating method, are contained. Therefore, it means that the dopant polymer is present only as a coating layer on the surfaces of the conductive particles or the active material particles, without substantially containing the self-polymerizing dopamine polymer particles. The self-cured polydopamine particle means a polydopamine particle formed by self-polymerization of monomers existing in a solution state.

A method for producing a conductive particle or an active material particle coated with a dopamine polymer which does not contain substantially self-polymerizing dopamine polymer particles according to an example of the present invention comprises the steps of: a) dissolving a solution containing a dopamine monomer in a conductive particle or an active material particle Followed by filtration immediately after coating, and b) surface polymerization of conductive particles or active material particles having a dopamine-based monomer formed on the surface obtained through the above-mentioned vacuum filtration.

The " coating " in the step a) means that a solution containing a dopamine-based monomer is formed on the surface of the conductive particles, wherein the dopamine-based monomer is wetted without being polymerized on the surface of the conductive particles.

The "surface polymerization" in the step b) means that the dopamine-based monomer self-polymerizes at the particle surface. A schematic diagram of the conductive particles or the active material particles coated with a surface-polymerized dopamine polymer is shown in Fig.

Further, the solution which is subjected to the steps a) and b) is wetted on the surface of the particles, and then polymerized to finally coat the polymer is referred to as " shower coating ".

The solution has a pH condition at which the dopamine monomer can polymerize, and the pH may be in the range of, for example, 7 to 12, preferably 8 to 10. Since the dopamine monomer has the self-polymerization property in the solution in the pH range, it is preferable that the pH range of the solution satisfies the above range for the surface polymerization in the step b).

Specifically, the dopamine-based monomer may comprise a compound having a catechol group or derivative thereof. The compound having the catechol or derivative thereof may include the following formula (1). Herein R ₁₁ to R ₁₂ are each independently selected from hydrogen or C 1 -C 5 alkyl, and at least one of them may be hydrogen, and may further include a substituent not shown in the following formula (1).

[Chemical Formula 1]

The compound represented by Formula 1 is subjected to self-polymerization with polydodamine in the pH range described above. These dopamine monomers can be autopolymerized in solution-based buffer solutions such as low-cost and environmentally-friendly distilled water. Whereby the polypodamine layer can be formed on the surfaces of the conductive particles or the active material particles. For example, the compound of Formula 1 may include dopamine, and the dopamine may be polymerized by a reaction represented by Formula 2 below to form polydodamine.

(2)

However, when the conductive particles or the active material particles are immersed in a solution containing a self-polymerizable dopamine monomer to form a dopamine polymer layer on the particle surface, the dopamine monomer is not polymerized only on the particle surface, Whereby self-polymerized dopamine polymer particles as shown in Fig. 8 are formed. It is important that the self-polymerizing dopamine polymer particles have an adverse effect of greatly lowering the conductivity of the electrode and the battery, so that it is most important to exclude it.

In order to separate the autopolymerized dopamine polymer particles, centrifugation, immersion, or the like may be used. However, this method can not completely remove self-polymerized dopamine polymer particles. Therefore, the electrodes made of the conductive particles or the active material particles coated with the dopamine polymer necessarily include self-polymerized dopamine polymer particles, and thus have a fatal disadvantage that the conductivity is remarkably lowered. However, when the coating of step a) and the step of filtration under reduced pressure and the surface polymerization of step b) are carried out sequentially, autopolymerized dopamine polymer particles are produced and incorporated together with the conductive particles or the active material particles coated with the dopamine polymer There is an effect that it can be prevented in advance.

Therefore, the electrode having the particle layer made of the conductive particle or the active material particle coated with the dopamine polymer and the binder can not only maintain the high conductivity of the conductive particle or the active material particle as it is, There is an effect that a sufficient binding force is exhibited. Therefore, the structure collapse due to deterioration of the electrode can be suppressed, and the lifetime of the electrode and the battery including the electrode can be remarkably improved.

In one embodiment of the present invention, the step a) is a step of coating a solution containing the dopamine monomer on the conductive particles or the active material particles, followed by filtration under reduced pressure. Specifically, it may be a step of bringing the dopant monomer into contact with the surfaces of the conductive particles or the active material particles for a short time to form a thin liquid phase layer. Therefore, self-polymerized dopamine polymer particles are not formed and a thin solution layer can be formed on the surface of the conductive particles. That is, self-polymerizing dopamine polymer particles may not be produced or may be excluded.

In the step a), the coating may be carried out by an instant dispersion method. That is, the step a) may be a step of instantly dispersing the conductive particles or the active material particles in a solution containing the dopamine-based monomer, coating them, and immediately filtering the resultant under reduced pressure. The instant dispersion may mean a coating method in which conductive particles or active material particles are dispersed in the solution as quickly as possible.

At this time, it is preferable that the contact time between the solution and the conductive particles or the active material particles during the instant dispersion is minimized. For example, the contact time may be 3 minutes or less, preferably 30 seconds or less. In this case, the smaller the lower limit value of the contact time is, the more specifically, 0.001 second can be exemplified.

The reason why the time of the step a) is important is that since the autopolymerization property is activated at the moment when the dopamine monomer is mixed into the solution, self-polymerized dopamine polymer particles are formed with time, and the number thereof is gradually increased . Therefore, it is preferable to minimize the time from when the conductive particles or the active material particles come into contact with the solution until the conductive particles or the active material particles on the surface of the dopamine-based monomer are obtained through the reduced pressure filtration.

As described above, the reduced pressure filtration in step a) may include removing a solution containing excess dopamine-based monomer. Generation of self-polymerized dopamine polymer particles can be prevented in advance by an instant dispersion method or the like, but a small amount of self-polymerized dopamine polymer particles can be produced in some cases. Therefore, after the subsequent vacuum filtration is further performed, excess solution forming the self-polymerized dopamine polymer particles can be removed, so that generation of the self-polymerized dopamine polymer particles can be effectively suppressed.

In addition, since the surface of the conductive particles or active material particles obtained after the filtration under reduced pressure is in a state in which the solution containing the dopamine monomer is wetted in a minimum amount, the conductive particles or the conductive particles having a very thin thickness of the dopamine polymer layer Active material particles can be produced. Therefore, the conductive particles or the active material particles having the dopamine polymer layer formed through steps a) and b) have a sufficient binding force with the binder and can maintain the initial high conductivity of the conductive particles or the active material particles almost intact .

As described above, the step a) may mean the step of forming a monomer layer on the surface of the particles, and the step b) may mean the step of forming a polymer layer on the surface of the monomer layer formed on the surface of the particles. have.

It is preferable that the dopant-based monomer is coated on the surface of the conductive particles or the active material particles in the whole area, but it may be coated on the conductive particles or a part of the area of the active material particles to minimize the deterioration of conductivity. Therefore, it may be more preferable in terms of not containing self-polymerizing dopamine polymer particles.

The pressure during the filtration under reduced pressure in step a) is not particularly limited as long as it is less than atmospheric pressure, and may be, for example, 0.5 atm or less, preferably 0.001 to 0.3 atm. When the above range is satisfied, the dopant solution is wet on the surfaces of the conductive particles or the active material particles, so that the dopamine polymer layer can be formed thinly and stably. The solution containing the excess dopamine monomer is smoothly removed and is not included in the conductive particles or the active material particles in which the dopamine polymer particles themselves are obtained.

The solvent, which is the solution of step a), may be any of various known materials as long as the dopamine-based monomer can be dissolved and not adversely react with the dopamine-based monomer. As a specific example, the solution is distilled water, which is advantageous not only in that the dissolution of the dopamine monomer and the autopolymerization reaction can be easily activated, but also from the viewpoints of economical efficiency and environmental friendliness, but the present invention is not limited thereto.

The content ratio of the dopamine monomer contained in the solution of step a) is not particularly limited, and the degree of polymerization or uniformity of the dopamine polymer layer formed by surface polymerization of the conductive particles or the active material particles by controlling the content ratio Lt; / RTI > As a specific example, the solution may comprise from 0.01 to 5% by weight of dopamine monomer based on the total weight of the solution.

The charging ratio of the conductive particles or the active material particles contained in the solution of step a) may be as long as the solution is wetted on the surfaces of the conductive particles or the active material particles. For example, conductive particles or active material particles of 0.1 to 1,000 It may be one part by weight. However, it is needless to say that the present invention is not limited thereto since the above-mentioned input ratio can be appropriately adjusted in some cases.

As described above, the solution of step a) preferably satisfies a pH range in which the self-polymerization of the dopamine monomer can be activated. Therefore, the solution may further contain a pH adjusting agent, a buffer, and the like. Thus, a method for preparing a conductive particle or an active material particle coated with a dopamine polymer may include a step of mixing a pH adjusting agent, a pH adjusting agent, And adjusting the pH of the solution. The pH adjustment is not limited as there are various well known ones, and the ratio of the content of the pH adjusting agent or the buffer to the solution is not limited as it can be appropriately adjusted so that the pH of the solution can be maintained or maintained at the required pH.

The pH adjusting agent is not limited as long as it can be adjusted to the required pH, and examples thereof include lactic acid or a salt thereof, pyrrolidone carboxylic acid or a salt thereof and an amino acid group (lysine, histidine, arginine, aspartic acid, threonine, serine, glutamic acid, And one or more components selected from glycine, alanine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, halfcysteine, cysteine, asparagine, glutamine or tryptophan and the like.

The buffer is not limited as long as it corresponds to the required pH and may be any buffer such as TRIS buffer, CITRATE buffer, BIS-TRIS buffer, MOPS buffer, phosphate buffer PHOSPHATE buffer, CARBONATE buffer, HEPES buffer, TRICINE buffer, BICINE buffer or TAPS buffer (TAPS buffer).

In one embodiment of the present invention, the conductive particles or the active material particles may be conductive particles or active material particles used in this field. The conductive particles or the active material particles may preferably be particles capable of forming a chemical bond with the dopamine based polymer layer. More preferably, the conductive particles may be carbon-based conductive particles.

As a specific example, the carbon-based conductive particles may include, for example, carbon black; Acetylene black; Ketjen Black; Furnace black; Oil-furnace black; Channel black; Lamp black; Summer Black; Columbia carbon; Carbon fiber; Graphene; Graphite; And mixed conductive particles comprising a carbon-based conductive material; , And the like.

As a specific example, the active material may be a cathode active material in a particulate state or a cathode active material in a particulate state.

The positive electrode active material can be used as long as it is a material capable of reversibly removing / inserting lithium ions, and may be an electrode material used for a positive electrode of a conventional lithium secondary battery. For example, the cathode active material may be an oxide of a layered structure typified by LiCoO ₂ , an oxide of a spinel structure represented by LiMn ₂ O ₄ , or a phosphate-based material of an olivine structure typified by LiFePO ₄ . The lithium-metal oxide of the layered structure is LiMO ₂ (M is a transition metal selected from Co and Ni in one or more of them); LiMO ₂ (M is one of Co and Ni) substituted with a heteroatom selected from Mg, Al, Fe, Ni, Cr, Zr, Ce, Ti, B and Mn, Or two or more transition metals); Li _x Ni _? Co _? M _? O ₂ (real number 0.9 _{? X ?} 1.1, real number 0.7?? 0.9, real number 0.05?? 0.35, real number 0.01? And M is at least one element selected from the group consisting of Mg, Sr, Ti, Zr, V, Nb, Ta, Mo, W, B, Al, Fe, Cr, Mn and Ce); Or Li _x Ni _a Mn _b Co _c M _d O ₂ (real number 0.9 ≦ _x ≦ 1.1, real number 0.3 ≦ a ≦ 0.6, real number 0.3 ≦ b ≦ 0.4, real number 0.1 ≦ _c ≦ 0.4, a + b + c + d = 1 and M is at least one element selected from the group consisting of Mg, Sr, Ti, Zr, V, Nb, Ta, Mo, W, B, Al, Fe, Cr and Ce) have. The lithium-metal oxide of the spinel structure is one or more elements selected from Li _a Mn _2-x M _x O ₄ (M = Al, Co, Ni, Cr, Fe, Zn, Mg, B and Ti, a? 1.1 and a real number of 0? x? 0.2) or Li ₄ Mn ₅ O ₁₂ , and the like. The phosphate-based material of the olivine structure may include LiMPO ₄ (M is Fe, Co, Mn) or the like. The cathode active material may be a single material or a composite of two or more materials (the first cathode active material and the second cathode active material). Such a composite includes a structure in which the first cathode active material and the second cathode active material are simply mixed; A core shell structure which is a core of the first cathode active material and a shell of the second cathode active material; A structure in which a second cathode active material is loaded or embedded in a matrix of the first cathode active material; A structure in which a second cathode active material is coated or supported on a first cathode active material having a zero-dimensional and one-dimensional or two-dimensional nanostructure; Or a laminated structure in which the first cathode active material and the second cathode active material are layered and laminated, respectively. However, it is needless to say that the present invention can not be limited by the specific material and the composite structure of the cathode active material.

The negative electrode active material may be any material conventionally used for a negative electrode of a lithium secondary battery, and the negative electrode active material may be a lithium intercalable material. As a non-limiting example, the negative electrode active material may be selected from the group consisting of lithium (metal lithium), graphitizable carbon, graphitizable carbon, graphite, silicon, Sn alloy, Si alloy, Sn oxide, Si oxide, Ti oxide, Ni oxide, FeO) and lithium-titanium oxide (LiTiO ₂ , Li ₄ Ti ₅ O ₁₂ ), and the like.

As described above, the conductive particles or the active material particles are preferably carbon-based conductive particles or active material particles. Particularly, the carbon-based conductive particles or the active material particles and the dopamine polymer layer can have high structural stability by chemical bonding. Therefore, the electrode made of the carbon-based conductive particle or the active material particle coated with the dopamine polymer can prevent the electrode structure from being collapsed due to the deterioration phenomenon even at a high charging / discharging times, and thus the lifetime characteristics of the secondary battery can be remarkably improved have.

In one embodiment of the present invention, the step (b) is a step of surface-polymerizing conductive particles or active material particles having a dopamine-based monomer formed on the surface obtained through the reduced pressure filtration. The surface polymerization may be performed as long as the surface polymerization of the dopamine monomer is completed. For example, the surface polymerization may be performed at 10 to 40 ° C for 1 minute or more, preferably 1 to 48 hours. However, it should be understood that the present invention is not limited to the above-described embodiments. Thus, the conductive particles or the active material particles coated with the dopamine polymer may be produced through the step b).

The average thickness of the dopant-based polymer layer is not particularly limited as long as sufficient binding force with the binder and excellent conductivity can be realized, and may be, for example, 1 nm or less, specifically 1 to 0.01 nm. If this is satisfied, the property that the conductivity of the conductive particles or the active material particles can be substantially maintained even though a sufficient binding force with the binder is ensured can be effectively implemented.

Also, the average size of the conductive particles or the active material particles may be as large as can be used for electrode production, and may be, for example, 1 to 1,000 nm.

In a preferred example, the ratio of the average thickness of the dopamine polymer layer to the average size of the conductive particles or the active material particles may be 1/30 or less, specifically 1 / 10,000 to 1/30. If it is not satisfied, the conductivity of the conductive particles or the active material particles is lost as the dielectric properties of the dopamine polymer layer are increased relative to the conductive characteristics of the conductive particles or the active material particles, so that the conductive particles or the active material particles may not be used as electrodes.

The electrode for a secondary battery according to an embodiment of the present invention may include conductive particles or active material particles coated with the dopamine polymer, but may not include self-polymerized dopamine polymer particles. As described above, is substantially free of self-polymerizing dopamine polymer particles.

The electrode may be applied to various batteries known in the art, and preferably to a lithium secondary battery having a relatively high cost.

As a specific example, the electrode includes conductive particles or active material particles coated with the dopamine-based polymer and a binder, but does not include autopolymerized dopamine polymer particles. In addition, the electrode may be formed of a conductive particle or an active material particle coated with the dopamine polymer and an active material layer containing a binder on the current collector. At this time, substantially no self-polymerizing dopamine polymer particles are contained.

In a preferred embodiment, the conductive particles or the active material particles may be chemically bonded to the dopamine based polymer layer as they are preferably carbon-based conductive particles. Further, since the dopamine polymer layer can be hydrogen bonded to the binder, the physical and chemical stability can be remarkably improved. Specifically, the dopamine polymer layer has a hydrophilic group including O, N, H, and the like, and thus can be hydrogen-bonded to the binder. The adhesion force of the electrode in the electrode can be remarkably improved, and deterioration of the electrode due to an increase in the number of times of charging / discharging can be minimized, and the life characteristic can be remarkably improved.

In one embodiment of the present invention, the binder may be any material capable of binding to the conductive particles or the active material particles without chemically reacting with the electrolytic solution, and may be a material capable of hydrogen bonding with the polypodamine coating layer . As a specific example, the binder may be selected from the group consisting of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-trichlorethylene copolymer, polymethylmethacrylate, polyacrylic, polyacrylic acid, poly But are not limited to, acrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpolylane, Styrene-butadiene copolymer, polyimide, polytetrafluoroethylene, or a mixture thereof, and the like can be used as a binder resin, and examples of the binder resin include polyvinyl alcohol, polyvinyl alcohol, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, have.

The method of manufacturing an electrode according to an embodiment of the present invention may include a step of forming an electrode by molding and drying a composition containing the dopant polymer-coated conductive particles or active material particles and a binder. When the composition does not include an active material, the active material may further include an anode active material or a cathode active material. The active material layer may be a positive electrode active material layer including a positive electrode active material or a negative electrode active material layer including a negative electrode active material, which may mean the above-described positive electrode active material or negative electrode active material.

For example, the composition may include 0.1 to 100 parts by weight of the binder with respect to 100 parts by weight of the conductive particles or the active material particles coated with the dopamine polymer.

In one embodiment of the present invention, the drying temperature and the drying time in the step of preparing the electrode are not particularly limited, and may be, for example, 30 to 100 ° C and 0.5 to 5 hours, respectively. However, it should be understood that the present invention is not limited thereto.

In one embodiment of the present invention, in the step of forming the electrode, the forming form can be freely selected if it has a structure that can be used as an electrode, so that the shape, structure and size are not limited. For example, the electrode may be a conventional plate-like structure, but the present invention is not limited thereto.

The method of manufacturing the electrode and the method of manufacturing the battery including the electrode belong to well-known techniques, and other known manufacturing methods may be used. Even in the case of a method for manufacturing an electrode or a battery which is not described in this specification, if the electrode including the conductive particle or the active material particle coated with the dopamine polymer and the battery including the electrode are included in the idea of the present invention, It belongs to the invention.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples. However, the present invention is described in more detail with reference to the following Examples. However, the scope of the present invention is not limited by the following Examples.

≪ Preparation of conductive particles coated with dopamine polymer &

Dopamine was added to a buffer solution (10 mM tris buffer solution, pH 8.5) based on distilled water, stirred and dissolved for 30 seconds to prepare a 2 mg / ml solution of dopamine. Immediately, 250 ml of the dopamine solution 5 g of carbon-based conductive particles (Carbon black, Super-P, TIMCAL) was added thereto and dispersed for 30 seconds. The mixture was filtered at a pressure of 0.2 atm under reduced pressure as shown in FIG. 2 to obtain carbon-based conductive particles wetted with the surface of the dopamine solution Respectively. At this time, the elapsed time from the time immediately after dopamine doped in the buffer solution based on distilled water until the carbon-based conductive particles were obtained was 3 minutes. The obtained carbon-based conductive particles were dried at room temperature for 24 hours so that the surface-doped dopamine monomer was surface-polymerized to obtain electrically conductive particles coated with a dopamine polymer that did not contain autopolymerized dopamine polymer particles.

In order to evaluate the characteristics of the conductive particles coated with the prepared dopamine polymer, each property was measured using a scanning electron microscope and X-ray photoelectron spectroscopy, and the results are shown in FIG. 0.5 g of the conductive particles coated with the dopamine polymer was dispersed in 9.5 g of distilled water, and the degree of precipitation with respect to distilled water was measured. The results are shown in FIG.

≪ Preparation of electrode using conductive particle coated with dopamine polymer &

The electrode was prepared using the conductive particles coated with the dopamine polymer. Specifically, a slurry having a composition ratio of 60% by weight of silicon with water as a solvent, 20% by weight of the conductive particles coated with the dopamine polymer prepared in Example 1 and 20% by weight of polyacrylic acid, And dried at 80 DEG C for 2 hours to prepare an electrode having an average thickness of 25 mu m.

In order to evaluate the characteristics of the electrodes, life characteristics and electrical conductivity characteristics according to the binding force characteristics, the number of charging / discharging times, and the electric conductivity were measured. The results are shown in FIG. 5 and Tables 1 and 6, respectively.

Surface and interfacial cutting analysis system (SAICAS) was used to measure the adhesion force inside the electrode. Specifically, after entering the middle layer of the electrode using a diamond blade in a constant velocity mode (horizontal velocity: 2 탆 / sec, vertical velocity: 0.2 탆 / sec), the vertical velocity was changed to 0 탆 / The bonding force inside the electrode was measured through the force measured while cutting in the horizontal direction from the inside of the electrode at the constant speed of 2 탆 / sec. The results are shown in FIG. 5 and Table 1.

A method of measuring lifetime characteristics according to the number of times of charging / discharging of an electrode is as follows: 1.15 M LiPF ₆ in EC / ECM = 3/7 + FEC 5 using a PE separator (Asahi Kasei) wt.% of electrolytic solution. The charge / discharge conditions of the battery were measured by repeating a total of 2,000 times through the PNE Solutions at a voltage of 0.05 to 2 V and 1200 mAh / g at 25 ° C. The results are shown in Fig.

The results for the electrical conductivity characteristics are also shown in Fig.

[Comparative Example 1]

(Carbon black, Super-P, TIMCAL) having an average size of 50 nm and not doped with a dopamine polymer were prepared in the same manner as in Example 1, and evaluated in the same manner as in Example 1 Respectively.

[Comparative Example 2]

The procedure of Example 1 was repeated except that the filtration under reduced pressure in Example 1 was not performed.

Specifically, dopamine was added to a buffer solution (10 mM tris buffer solution, pH 8.5) based on distilled water, stirred and dissolved for 30 seconds to prepare a 2 mg / ml solution of dopamine. Subsequently, 5 g of carbon-based conductive particles (Carbon black, Super-P, TIMCAL) was added to 250 ml of the dopamine aqueous solution and the self-polymerization reaction was induced by immersing the conductive particles in the dopamine aqueous solution for 5 minutes by immersion coating. After three centrifugations to separate the conductive particles from the dopamine aqueous solution, conductive particles coated with the dopamine polymer were obtained.

As a result, in the case of coating by the immersion method, self-polymerized dopamine polymer particles as shown in the image of FIG. 8 were present even when centrifugation was performed three times.

3 is a graph showing the results of measurement of each conductive particle according to Comparative Example 1 and Example 1 by a scanning electron microscope (SEM) and an X-ray photoelectron spectroscopy (XPS) . In Fig. 3, the image and the graph on the left are data on the conductive particles of Comparative Example 1, and the image on the right and the graph are the data on the conductive particles coated with the dopamine polymer of Example 1. Fig.

In the scanning electron microscope image of FIG. 3, it can be seen that the surface structure of the conductive particles coated with the dopamine polymer of Example 1 and that of the untreated conductive particles of Comparative Example 1 do not differ greatly. Also, in the XPS spectrum, it can be seen that the N peak and the O peak increase. That is, although it is difficult to observe the surface structure of the polypodamine coating layer by a scanning electron microscope, peaks corresponding to polypopamine are observed through the XPS spectrum. Therefore, the surface of the conductive particles of Example 1 is difficult to observe with a scanning electron microscope Of the polyphenylene sulfide layer is formed.

4 is an image for water dispersion test of the conductive particles according to Comparative Example 1 and Example 1. Fig. At this time, the left image is an image in which the conductive particles of Comparative Example 1 are dispersed in water, and the right image is an image in which conductive particles coated with the dopamine polymer of Example 1 are dispersed in water. It was confirmed that the conductive particles coated with the dopamine polymer of Example 1 dispersed well in the distilled water to precipitate slowly, while the untreated conductive particles of Comparative Example 1 quickly precipitated. This is due to the fact that polydopamine contains O, N, H, and other elements and is capable of hydrogen bonding with water molecules. That is, it can be seen that a polydopamine layer is present on the surface of the conductive particles of Example 1.

5 and Table 1 are graphs showing the results of measuring the internal adhesion of the electrode according to Comparative Example 1 and Example 1 using a surface and interfacial cutting analysis system (SAICAS).

Cutting thickness (탆) Average adhesion force (kN / m) Comparative Example 1 15 0.099 Example 1 15 0.117

As shown in Table 1, it was confirmed that the internal adhesion of the electrode including the conductive particles coated with the dopamine polymer of Example 1 was improved by 18% or more. It can also be seen from Fig. 5 that, except for the error range, it has a high internal binding force regardless of the position inside the electrode. This is attributed to the fact that the dopamine polymer layer formed on the surface of the conductive particles and the binder appear by hydrogen bonding.

6 is a graph showing the results of measurement of life characteristics of electrodes according to Comparative Examples 1, 2, and 1. From this, it can be seen that the secondary battery made of the electrode including the conductive particles coated with the dopamine polymer of Example 1 has a capacity of about 1/4 compared to the initial value even when the number of charging / discharging exceeds 2,000 times, It can be seen that the secondary battery made of the electrode including the untreated conductive particles of Example 1 lost the function of the battery with the number of charge / discharge exceeding about 600 times.

In particular, it can be seen from FIG. 6 that in Comparative Example 2 in which the dopamine polymer is coated by the immersion method, the lifetime characteristics are lowered rather than the case of Comparative Example 1 which is not treated. This is considered to be due to the fact that, in the case of Comparative Example 2, the self-polymerization dopamine polymer particles are inevitably included and thus the lifetime characteristics are further degraded as a resistor.

7 is a graph showing the results of measurement of electrical conductivity characteristics of electrodes according to Comparative Example 1, Comparative Example 2 and Example 1. Fig. It can be seen from Fig. 7 that the electrical conductivity of Example 1 and Comparative Example 2 is significantly higher than that of Comparative Example 2 in the same way as the result of the evaluation of the life characteristic. This is considered to be attributable to the fact that, in the case of Comparative Example 2, self-polymerized dopamine polymer particles as shown in FIG. 8 are produced and included together in the process of forming a dopamine polymer layer on the conductive particles.

Therefore, as in Example 1, self-polymerized dopamine polymer particles can be generated and prevented from being included, and it can be seen that the conductivity of the electrode and the lifetime characteristics of the battery are remarkably improved.

10: polymer layer
20: conductive particle or active material particle

Claims (4)

A secondary battery electrode comprising self-polymerized dopamine polymer particles having an average size of 50 to 600 nm, the active material particles comprising conductive particles coated with a dopamine polymer or coated with a dopamine polymer. The method according to claim 1,
Wherein the conductive particles are carbon-based conductive particles. 3. The method of claim 2,
Wherein the carbon-based conductive particles include at least one of carbon black, acetylene black, ketjen black, furnace black, oil-furnace black, channel black, lamp black, summer black, carbon black, carbon fiber, graphene, graphite, Conductive particles, and mixed conductive particles. A secondary battery comprising an electrode for a secondary battery according to any one of claims 1 to 3.

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