WO2023014127A1 - Electrode for electrochemical device comprising dry electrode film and method for manufacturing same - Google Patents

Abstract

A method for manufacturing a dry electrode according to the present invention can determine the degree of microfibrillation of a binder resin from the crystallinity of the binder resin, and on the basis of this, the process conditions of mixed powder for an electrode or an electrode film can be controlled, making it easy and efficient to check and control the process conditions. In addition, the method for manufacturing a dry electrode according to the present invention is advantageous for mass production by passing through kneading and grinding by a high-temperature and low-speed kneader, so that there is no problem of passages being clogged due to aggregation of constituent ingredients.

Description

Electrochemical device electrode including dry electrode film and manufacturing method thereof

This application claims priority based on Korean Patent Application No. 10-2021-0104169 filed on August 6, 2021. The present invention relates to an electrode for an electrochemical device including a dry electrode film and a method for manufacturing the same. In addition, the present invention relates to the dry electrode film and a manufacturing method thereof. In addition, the present invention relates to a mixed powder for an electrode used to manufacture the dry electrode film and a method for manufacturing the same.

Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy and clean energy is increasing. Currently, a secondary battery is a representative example of an electrochemical device using such electrochemical energy, and its use area is gradually expanding. Among these secondary batteries, representative lithium secondary batteries are used not only as an energy source for mobile devices, but also as vehicles that use fossil fuels such as gasoline vehicles and diesel vehicles, which are one of the major causes of air pollution. Its use as a power source for automobiles is being realized, and its use area is expanding to applications such as power auxiliary power sources through gridization. The manufacturing process of such a lithium secondary battery is largely divided into three steps: an electrode manufacturing process, an electrode assembly manufacturing process, and a conversion process. The electrode manufacturing process is again divided into an electrode mixture mixing process, an electrode coating process, a drying process, a rolling process, a slitting process, a winding process, and the like. Among them, the electrode mixture mixing process is a process of mixing components for forming an electrode active layer in which an actual electrochemical reaction occurs in an electrode. It is prepared in the form of a slurry having fluidity by mixing a binder for binding and adhesion to a current collector, and a solvent for imparting viscosity and dispersing powder.

In this way, the mixed composition for forming the electrode active layer is also referred to as an electrode mixture in a broad sense. Thereafter, an electrode coating process of applying the electrode mixture on an electrically conductive current collector and a drying process for removing the solvent contained in the electrode mixture are performed, and the electrode is additionally rolled to manufacture a predetermined thickness.

Meanwhile, as the solvent contained in the electrode mixture evaporates during the drying process, defects such as pinholes or cracks may be induced in the previously formed electrode active layer. In addition, since the inside and outside of the active layer are not dried uniformly, the powder floating phenomenon caused by the difference in solvent evaporation rate, that is, the powder in the area dried first floats and forms a gap with the area dried relatively later, resulting in electrode quality this may deteriorate.

Therefore, in order to solve the above problem, a drying device capable of controlling the evaporation rate of the solvent while uniformly drying the inside and outside of the active layer is being considered, but these drying devices are very expensive and require considerable cost and time to operate. As it is required, there are disadvantages in terms of manufacturing processability. Therefore, in recent years, studies on manufacturing a dry electrode that does not use a solvent have been actively conducted.

The dry electrode is generally manufactured by laminating a free standing film including an active material, a binder, a conductive material, and the like and manufactured in a film form on a current collector. First, an active material, a carbon material as a conductive material, and a fiberizable binder are mixed together in a blender, etc., and the binder is fiberized through a high shear mixing process such as jet-milling. and calendering the mixture into a film form to prepare a free standing film. Then, it is produced by laminating the free-standing film produced after calendering on the current collector.

However, when the above high shear mixing process is applied to a brittle active material, a lot of fine powder having a small powder size is generated, and mechanical performance or electrochemical performance is easily deteriorated. By cutting the flexibility of the free standing film may be reduced.

Therefore, there is an urgent need to develop a dry electrode manufacturing technology capable of solving these problems. In particular, it is necessary to provide a method capable of quantitatively analyzing the uniformity of mixing of a mixture in which the components for preparing the dry electrode film are mixed or the state of the binder (degree of fiberization, etc.) and establishment of process conditions.

The present invention is to solve the above problems, and an object of the present invention is to provide a dry electrode and a method for manufacturing the same, in which micronization of the active material is minimized and fiberization of the binder is maximized.

In addition, an object of the present invention is to provide a dry electrode with improved mechanical properties such as flexibility and strength, and a manufacturing method thereof.

In addition, an object of the present invention is to provide a dry electrode manufacturing method to which process conditions based on the crystallinity of a binder resin are applied.

A first aspect of the present invention relates to an electrode for an electrochemical device, wherein the electrode includes a dry electrode film manufactured by a dry manufacturing process that does not use a solvent, and the dry electrode film includes an electrode active material, a conductive material, and a binder A resin and a binder resin included in the dry electrode film have a crystallinity of 10% or less.

In a second aspect of the present invention, according to the first aspect, the dry electrode film has a tensile strength of 0.5 MPa or more in the machine direction (MD).

In a third aspect of the present invention, in the first or second aspect, the dry electrode film has a tensile elongation of 2% or more.

In a fourth aspect of the present invention, according to any one of the first to third aspects, the electrode film has a porosity of 20 vol% to 50 vol%.

As for a method for manufacturing an electrode for an electrochemical device of the present invention, the electrode is according to any one of the first to fourth aspects, the method comprising: (a) an electrode active material, a conductive material, and a binder resin preparing a powdery blend;

(b) preparing a mixture mass by kneading the powdery mixture at a temperature in the range of 70° C. to 200° C.;

(c) obtaining a mixed powder for an electrode by pulverizing the mass of the mixture; and

(d) calendering the mixed powder for the electrode to obtain a free standing type dry electrode film, wherein the crystallinity (d) of the binder resin included in the dry electrode film obtained in step (d) is It is less than 10%.

In the sixth aspect of the present invention, in the fifth aspect, the crystallinity (c) of the binder resin included in the electrode mixture powder obtained in step (c) is 20% or less.

In the seventh aspect of the present invention, in the fifth or sixth aspect, the crystallinity (a) of the binder resin contained in the mixture obtained in step (a) is 50% or less.

An eighth aspect of the present invention, according to any one of the fifth to seventh aspects, the step (a) is performed under conditions of 500 rpm to 30,000 rpm.

In the ninth aspect of the present invention, in any one of the fifth to eighth aspects, the step (b) is performed at a speed of 100 rpm or less.

In the tenth aspect of the present invention, in any one of the fifth to ninth aspects, the step (b) is performed under a pressure of 0.5 kgf/cm ² to 10 kgf/cm ² .

In the eleventh aspect of the present invention, in any one of the fifth to tenth aspects, the step (b) is performed under normal pressure or higher conditions.

In the twelfth aspect of the present invention, according to any one of the first to fourth aspects, the binder resin includes polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyolefin, or a mixture of two or more of them is to do

In a thirteenth aspect of the present invention, according to any one of the first to fourth aspects, the electrode further includes a current collector, and the dry electrode film is disposed on at least one side or both sides of the current collector. .

A fourteenth aspect of the present invention according to any one of the fifth to eleventh aspects further comprises preparing a current collector, disposing the dry electrode film on at least one side of the current collector, and laminating the dry electrode film.

A fifteenth aspect of the present invention relates to a secondary battery, comprising the dry electrode according to any one of the first to fourth aspects, wherein the dry electrode is a positive electrode, and an electrode assembly including the positive electrode, the negative electrode, and the separator It is built into the battery case together with the lithium-containing non-aqueous electrolyte.

A sixteenth aspect of the present invention relates to an energy storage device including the secondary battery according to the fifteenth aspect as a unit cell.

A seventeenth aspect of the present invention relates to a method for manufacturing electrode powder for manufacturing a dry electrode film, the manufacturing method comprising: (a) preparing a powdery blend including an electrode active material, a conductive material, and a binder resin;

(b) kneading the powdery blend at a temperature in the range of 70° C. to 200° C. to prepare a mixture mass; and

(c) a process of pulverizing the mixture lump to obtain a mixed powder for an electrode; including,

The binder resin included in the electrode powder has a crystallinity of 20% or less,

The binder resin includes polytetrafluoroethylene (PTFE), polyolefin, or a mixture thereof.

An eighteenth aspect of the present invention is a mixed powder for an electrode prepared by the method according to the seventeenth aspect, wherein the mixed powder for an electrode includes an electrode active material, a conductive material, and a binder resin, and the binder resin is polytetrafluorocarbon. It includes polyethylene (Polytetrafluoroethylene, PTFE), PVDF, polyolefin, or a mixture of two or more of them, and the crystallinity of the binder resin included in the mixed powder for the electrode is 20% or less.

A nineteenth aspect of the present invention relates to a method for manufacturing a dry electrode film comprising the steps of calendering the mixed powder for electrode to obtain a free standing type dry electrode film, wherein the mixed powder for electrode is the seventeenth It is obtained by the method according to the aspect, and the crystallinity (d) of the binder resin included in the electrolytic electrode film is 10% or less.

A twentieth aspect of the present invention relates to a dry electrode film produced by the method according to the nineteenth aspect, and has a tensile strength of 0.5 MPa or more in the machine direction (MD), a tensile elongation of 2% or more, and a porosity of is 20 vol% to 50 vol%.

The dry electrode manufacturing process according to the present invention introduces a process of pulverizing after a high-temperature, low-shear mixing process when preparing mixed powder for an electrode, thereby minimizing the pulverization of the active material and preventing the cutting of the fibrous binder. In addition, by manufacturing a dry electrode using the powder mixture for an electrode, there is an effect of improving mechanical properties such as flexibility and strength of the dry electrode.

In addition, the dry electrode manufacturing method according to the present invention can determine and confirm the degree of fine fiberization of the binder resin and whether the process of each step is completed from the crystallinity of the binder resin in each step, and based on this, the process of the mixed powder for electrode or electrode film Conditions can be controlled, making it easy and efficient to check and control process conditions and process completion time.

In addition, the dry electrode manufacturing method according to the present invention is advantageous for fine fiberization by undergoing low shear kneading and pulverization through a kneader, and is advantageous for mass production because there is no problem of clogging of the flow path due to aggregation of components.

1 shows a DSC thermal analysis graph according to Example 1 of the present invention.

2 shows a DSC thermal analysis graph according to Example 2 of the present invention.

3 is a process flow chart showing the manufacturing sequence of the dry electrode of the present invention.

Hereinafter, the present invention will be described in more detail to aid understanding of the present invention.

Terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventor may appropriately define the concept of terms in order to explain his or her invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

Terms used in this specification are only used to describe exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

In addition, throughout the specification, when a certain component is said to "include", it means that it may further include other components without excluding other components unless otherwise stated.

One aspect of the present invention relates to an electrode for an electrochemical device and a method for manufacturing the same. The electrochemical device may be, for example, a secondary battery, and more specifically, the secondary battery may be a lithium ion secondary battery.

In the present invention, the electrode includes a dry electrode film manufactured by a dry manufacturing process in which a solvent for dispersing electrode components is not used during the electrode manufacturing process. The dry electrode film includes an electrode active material, a conductive material, and a binder resin, and the binder resin included in the dry electrode film has a crystallinity of 10% or less. For example, the crystallinity may be 5% or less.

When the crystallinity range is 10% or less, the binder resin is highly fibrous, so flexibility of the dry electrode film can be secured. Therefore, as will be described later, it is easy to manufacture a dry electrode film in the form of a strip in the calendering process to which a roll to roll continuous process is applied, and after manufacturing the electrode film, it is wound or re-wound in a roll form. When shipped, the shape is stably maintained without damage such as fracture or cracking. In addition, it is advantageous to ensure that the binding force with the current collector exceeds a predetermined strength.

Further, in the present invention, the dry electrode film preferably has a tensile strength of 0.5 MPa or more in the machine direction (MD). Meanwhile, the dry electrode film may have a tensile strength of 10.0 MPa or less, 5.0 MPa or less, or 3.0 MPa or less in the machine direction (MD). When the tensile strength satisfies the above range, it is possible to secure sufficient mechanical strength when manufacturing a freestanding type dry electrode, so that manufacturing and handling are easy. On the other hand, if it is less than the above range, the mechanical strength is weak and can be easily broken. On the other hand, when the tensile strength is excessively high, since the tensile elongation increases together, the fairness is lowered as follows and the film thickness is not uniform.

Meanwhile, the dry electrode film preferably has a tensile elongation of 2% or more.

The dry electrode film may have a tensile elongation of 30% or less, 20% or less, or 10% or less.

When the tensile elongation satisfies the above range, sufficient dimensional stability and flexibility can be secured during the manufacture of a freestanding type dry electrode, making manufacturing and handling easy. When the tensile elongation is excessively low, flexibility and dimensional stability It is not preferable because it is low and can be easily broken during manufacturing or transportation. On the other hand, when the above range is exceeded, the flexibility is excessively high, and the dry electrode film may be excessively stretched between rolls in the calendering process described later, and the thickness of the obtained film may not be constant.

Meanwhile, the porosity of the dry electrode film may be 20 vol% to 50 vol%.

A second aspect of the present invention relates to a method for manufacturing the electrode. In the method of manufacturing the electrode, the crystallinity of the binder resin included in the dry electrode film is controlled to 10% or less. In the present invention, the crystallinity is zero or less than 10% in the dry electrode.

In one specific embodiment, the method for manufacturing the electrode

(a) preparing a powdery blend comprising an electrode active material, a conductive material, and a binder resin;

(b) kneading the powdery blend to produce a mass of mixture;

(c) obtaining a mixed powder for an electrode by pulverizing the mass of the mixture; and

(d) calendering the mixed powder for the electrode to obtain a free standing type dry electrode film; includes.

Meanwhile, in one embodiment of the present invention, step (b) may be performed under a temperature condition of 70 °C to 200 °C. For example, the object to which the kneading process is applied may be controlled at a temperature of 70° C. to 200° C.

Here, in the powdery blend obtained in step (a), the crystallinity (a) of the binder resin is 60% or less, preferably 50% or less. In addition, the crystallinity (c) of the binder resin in the electrode mixture powder obtained in step (c) is 20% or less, and the crystallinity (d) of the binder resin in the dry electrode film obtained in step (d) is 10% it is below

In one embodiment of the present invention, determining the completion of each step of (a) to (d) is to check the crystallinity of the product obtained in each step. If the crystallinity of the binder resin of the product in each process step satisfies the crystallinity degree determined in advance in each step, the next step process is performed.

Specifically, in the step (a), when the crystallinity of the binder resin of the powdery blend is 60% or less, preferably 50% or less, the process of step (a) is terminated, and the obtained product is introduced into step (b) .

In addition, in step (c), when the crystallinity of the binder resin in the mixed powder for electrode is 20% or less, the process of step (c) is terminated, and the subsequently obtained result is introduced into step (d).

In addition, the step (d) is regarded as complete when the crystallinity of the binder resin in the obtained dry electrode film satisfies 10% or less.

Alternatively, in steps (a), (b) and (d), the process conditions in which the crystallinity within the range can be controlled are experimentally confirmed in each step, and the experimentally set process is performed in each step. can be applied to

In the present invention, the crystallinity (Xc) can be measured through differential scanning calorimetry (DSC), and is based on the temperature (peak temperature) at the time of crystallization showing the highest enthalpy. Specifically, the crystallinity is expressed in % by dividing the melting enthalpy (ΔH _m ) value actually measured by DSC by the melting enthalpy (ΔH _m ⁰ ) (equilibrium heat of fusion) of a theoretically perfect crystal (crystallinity 100%) and expressed in %, can be calculated by 1. Here, the melting enthalpy value (ΔHm0) of the theoretical perfect crystal may refer to a polymer handbook (J. Brandrup et al., 2003) or academic papers such as Polymer. For example, the melting enthalpy value of a theoretical perfect crystal of PTFE is 85.4 J/g (Polymer Journal 46 (2005) 8872-8882). Meanwhile, thermal analysis of polymers such as DSC can be measured and calculated according to ASTM D3418-21.

[Relationship 1]

Xc(%) = (∆H _m ÷ △H _m ⁰ ) x 100

Hereinafter, a method for manufacturing a dry electrode according to the present invention will be described in more detail.

First, a powdery blend including an electrode active material, a conductive material, and a binder is prepared (step a).

At this time, the mixing to prepare the powdery blend is performed to obtain a uniform blend of the electrode active material, the conductive material, and the binder resin, and preferably to adjust the crystallinity of the binder resin in the obtained powdery blend to 50% or less. It will be. Since the above materials are mixed in the form of powder, it is not limited and various methods may be applied as long as they enable uniform mixing. However, since the present invention is manufactured with a dry electrode that does not use a solvent, the mixing may be performed by dry mixing. For example, it may be performed by injecting the materials into a device such as a mixer or blender.

In one embodiment of the present invention, the mixing time is not particularly limited, but may be performed for 1 second to 20 minutes. For example, it may be performed for 1 second to 10 minutes. On the other hand, the mixing speed is not particularly limited, but may be appropriately controlled within the range of about 500 rpm to 30,000 rpm. For example, it may be controlled in the range of 500rmp to 20,000rpm.

Meanwhile, in one embodiment of the present invention, the temperature of the mixture may be controlled to 70 °C or less or 60 °C or less. When the mixing temperature exceeds 70° C., it may be difficult to obtain a uniform mixture due to the adhesion of the materials to the mixing device. On the other hand, the lower limit of the temperature of the mixture is not particularly limited, and in one embodiment of the present invention, it may be carried out at a temperature of 20 ℃ or more.

As a specific example, the mixing is performed in a mixer at 500 rpm to 20,000 rpm for 30 seconds to 10 minutes or at 5,000 rpm to 20,000 rpm for 30 seconds to 2 minutes in a mixer in terms of high uniformity and control of the crystallinity of the binder resin, and the temperature of the mixture is 70 ° C. or less. It can be prepared by mixing at a temperature of, or 1000 rpm to 15,000 rpm or 10,000 rpm to 15,000 rpm for 30 seconds to 1 minute or 30 seconds to 7 minutes at a temperature of 60 ° C or less.

In the present invention, the crystallinity of the binder resin in the mixture obtained by the mixing is 60% or less, preferably 50% or less. On the other hand, when the crystallinity of the binder resin in the obtained mixture exceeds 60% or 50%, the speed (rpm) is increased and/or the process time is increased to pulverize the binder lumps into primary particles so that they do not agglomerate, , it is desirable to partially advance coarse fiberization.

If the crystallinity of the blend mixture obtained in step (a) is not within the above range and is not high, fiberization of the binder resin is not easy in the low shear kneading process (step b) described later, and fibers are formed on the surface of the binder. It may not be sufficiently formed or the process time required for fiberization of the binder resin may be increased.

On the other hand, when the mixing time is excessively long, the mixing speed is excessively high, or both, the electrode active material may be micronized/damaged or the fibers may be cut. Along with this, there is a possibility that/or non-uniformity of binder fiberization may be caused. Considering this point, in one embodiment of the present invention, the crystallinity of the binder resin in the mixture blend may be controlled to 30% or more, 35% or more, or 40% or more.

In the present invention, the binder resin is not limited to a specific one as long as it can be fibrillated by step (a) and/or step (b) described later.

On the other hand, the binder resin may be fibrous even in step (a), but the fiber formed in step (a) is thick and is difficult to be thinned enough to achieve tensile elongation with tensile strength required in a dry electrode. In the present invention, preferably, the fine fiberization of the binder resin is mainly performed through (b) to be described later.

The fibrillation refers to a treatment of thinning and dividing a high-molecular polymer, and may be performed using, for example, mechanical shear force. The surface of the polymer fibers fibrillated in this way is unraveled, and a large number of fine fibers (fibrils) are generated. Non-limiting examples of the binder resin may include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyolefin, or a mixture of two or more thereof, and in detail, polytetrafluoroethylene ( Polytetrafluoroethylene (PTFE) may be included, and more specifically, polytetrafluoroethylene (PTFE) may be included. Specifically, the polytetrafluoroethylene (PTFE) may be included in an amount of 30% by weight or more based on the total weight of the binder resin. On the other hand, at this time, of course, the binder resin may additionally include polyethylene oxide (PEO) and/or polyvinylidene fluoride-cohexafluoropropylene (PVdF-HFP) in addition to the aforementioned components.

The dry electrode may be a cathode, and the electrode active material may be a cathode active material.

The cathode active material is not limited to a specific component as long as it is in the form of lithium transition metal oxide, lithium metal iron phosphate, or metal oxide. Layered compounds such as lithium cobalt oxide (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ), or compounds substituted with one or more transition metals; lithium manganese oxides such as Li _1+x Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ ; lithium copper oxide (Li ₂ CuO ₂ ); vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ , where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.5, for example For Li(Ni,Co,Mn,Al)O ₂ as Those in which the fraction of Ni among metals other than Li is 50% or more; Formula LiMn _2-x M _x O ₂ where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1 or Li ₂ Mn ₃ MO ₈ where M = Fe, Co, Ni, Cu or Zn) lithium manganese composite oxide; LiMn ₂ O ₄ in which Li part of the formula is substituted with an alkaline earth metal ion; lithium metal phosphate LiMPO ₄ (where M is M = Fe, CO, Ni, or Mn), disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like may be exemplified, and one or more of them may be included. However, it is not limited only to these.

Alternatively, the dry electrode may be an anode, and the active material may be a cathode active material. The negative electrode active material may include carbon such as non-graphitizing carbon and graphite-based carbon; Li _x Fe ₂ O ₃ (0≤x ≤1), Li _x WO ₂ (0≤x≤1), Sn _x Me _1-x Me' _y O _z (Me: Mn, Fe, Pb, Ge; Me' : metal composite oxides such as Al, B, P, Si, elements of groups 1, 2, and 3 of the periodic table, halogens; 0x≤1; 1≤y≤3; 1≤z≤8); lithium metal; lithium alloy; silicon-based alloys; tin-based alloys; silicon-based oxides such as SiO, SiO/C, and SiO ₂ ; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ and metal oxides such as Bi ₂ O ₅ ; conductive polymers such as polyacetylene; A Li-Co-Ni-based material or the like can be used.

However, the dry electrode may be a positive electrode in detail, and therefore, the active material may be a positive electrode active material in detail, and more specifically, lithium transition metal oxide, lithium nickel-manganese-cobalt oxide, lithium nickel- It may be an oxide in which a part of manganese-cobalt oxide is substituted with another transition metal, lithium iron phosphate, and the like.

The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples include graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used, but in detail, 1 selected from the group consisting of activated carbon, graphite, carbon black, and carbon nanotubes for uniform mixing of the conductive material and improvement of conductivity. It may include more than one species, and more specifically, it may include activated carbon.

The mixing ratio of the electrode active material, the conductive material, and the binder may include 80 to 98% by weight: 0.5 to 10% by weight: 0.5 to 10% by weight of the electrode active material: conductive material: binder resin, in detail, 85 to 98% by weight: 0.5 to 5% by weight: 0.5 to 10% by weight may be included.

Outside of the above range, if the content of the binder resin is too large, the binder resin may become excessively fibrous in the subsequent kneading process and affect the process, and if it is too small, sufficient fiberization may not be achieved, resulting in the formation of a mixture lump. There may be a problem of not being able to aggregate to a certain extent, making it difficult to manufacture a dry electrode film, or deteriorating physical properties of the dry electrode film.

In addition, outside the above range, if the content of the conductive material is too large, the content of the active material is relatively reduced, resulting in a capacity reduction problem. If it is too small, sufficient conductivity cannot be secured or the physical properties of the dry electrode film may deteriorate bar, not desirable.

On the other hand, in some cases, a filler, which is a component that suppresses expansion of the electrode, may be additionally added to the mixture, and the filler is not particularly limited as long as it does not cause chemical change in the battery and is a fibrous material. For example, olefinic polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

In one embodiment of the present invention, in the powdery blend obtained in step (a), the crystallinity of the binder resin is checked, and when the determined crystallinity is 60% or less, preferably 50% or less, step (a) The process of may be terminated, and the obtained product may be introduced into step (b). The degree of crystallinity can be confirmed at each step while processes (a) to (d) are performed.

Alternatively, in another embodiment, in the step (a), the process conditions in which the crystallinity of the binder resin of the powdery blend can be controlled to 60% or less, or 50% or less are experimentally confirmed, and the experimentally set process is performed as described above. Step (a) is applicable.

Next, as a process for fiberizing the binder resin with respect to this mixture obtained above, a kneading step is performed (step b).

In this kneading step, since a relatively low shear force is applied at a high temperature as will be described later, there is no risk of pulverization/damage of the electrode active material or cutting of the binder fibers, and mixed particles for electrodes in which the binder resin is finely fibrous can be obtained. In addition, the fiberization binder has high uniformity of fiber thickness and/or length.

The kneading is not limited to a specific method. In one specific embodiment of the present invention, the kneading may be performed through a kneader such as a kneader. For example, a twin screw extruder, a single screw extruder, a batch type kneader, a continuous type kneader, etc. may be used as the kneader.

This kneading is a step of forming a lumpy blend of 100% solid content by combining or connecting the electrode active material and conductive material powders while the binder resin is fibrous.

Specifically, the kneading in step (b) may be controlled at a speed of 10 rpm to 100 rpm. For example, the kneading may be controlled at a speed of 20 rpm or more or 70 rpm or less within the above range.

Meanwhile, in one embodiment of the present invention, the kneading may be performed for 1 minute to 30 minutes. For example, it may be performed for 3 minutes to 10 minutes at a speed of 20 rpm to 70 rpm within the above range.

Meanwhile, in one embodiment of the present invention, in the kneading step, the shear rate may be controlled in the range of 5/sec to 1,000/sec. In a specific embodiment of the present invention, the kneading may be performed for 1 minute to 30 minutes, and the shear rate may be controlled in the range of 10/sec to 500/sec.

The kneading step may be performed under conditions of high temperature and atmospheric pressure or higher.

Specifically, the kneading may be performed at a range of 70°C to 200°C, specifically, 90°C to 150°C. The temperature may be the temperature inside the kneader or the temperature of the object to be kneaded. Alternatively, both temperatures may be controlled within the above range.

Outside of the above range, when performing at a low temperature, when performing the kneading process, fiberization of the binder and lumping due to kneading are not easily performed, so film formation is not easily performed during calendering, and when carried out at too high a temperature, Fiberization of the binder occurs rapidly, and there is a problem that already formed fibers may be cut by excessive shearing force, which is not preferable.

In addition, the kneading process may be performed under a pressure of 0.5 kgf/cm ² to 10 kgf/cm ² , more specifically, under a pressure of 1 kgf/cm ² to 8 kgf/cm ² , for example, at a pressure of 8 kgf/cm ² or less above normal pressure. there is. Outside the above range, if it is carried out at too high a pressure, it is not preferable because there may be problems in that fibers formed by applying excessive shear force and pressure may be cut or the density of the mixture lump may be too high. That is, according to the present application, when performing a low shear kneading process under conditions of high temperature and normal pressure or higher, the intended effect of the present invention can be achieved. Alternatively, it may be carried out under normal pressure or above, specifically, under an atmospheric pressure of 1 atm to 3 atm, or under an atmospheric pressure of 1.1 atm to 3 atm.

Meanwhile, in one embodiment of the present invention, the process conditions in the kneading step may be controlled according to the characteristics of the input material. In a specific embodiment, the process conditions may be appropriately adjusted according to the particle diameter of the injected electrode active material particles. When the particle size of the electrode active material particles is large, fiberization may proceed relatively easily compared to electrode active materials having a small particle size. Accordingly, when the particle size of the electrode active material is large, a relatively low rotation speed and/or shear rate may be applied, and when the particle size of the electrode active material is small, a relatively high rotation speed and/or shear rate may be applied. On the other hand, even in the case of temperature or pressure, it can be adjusted in consideration of these material characteristics.

Next, a step of obtaining mixed powder for an electrode by pulverizing the lumpy blend material prepared through the step of (b) kneading is performed (step c).

Specifically, the lumpy blend produced through the (b) kneading step may be directly put into a calendering process to form a sheet, but in this case, strong pressure and high temperature are required to press the mixture lump to form a thin film, Accordingly, a problem may occur in which the density of the dry electrode film is too high or a uniform film cannot be obtained in terms of thickness or density. Accordingly, according to the present invention, the mass of the mixture prepared in step (b) (blended blend in the form of lumps) is subjected to the crushing step.

At this time, the grinding is not particularly limited, but may be performed using a known grinding device such as a blender or grinder. In a specific embodiment of the present invention, the grinding speed may be controlled within the range of 100 rpm to 30,000 rpm or 3000 rpm to 30,000 rpm. Meanwhile, the grinding time may be appropriately controlled within a range of 1 second to 10 minutes. However, the grinding speed and time are not particularly limited to the above ranges. As a specific example, the grinding is performed at a speed of 500 rpm to 20,000 rpm or 5000 rpm to 20000 rpm for 30 seconds to 10 minutes, or at a speed of 700 rpm to 18000 rpm or 10000 rpm to 18000 rpm for 30 seconds to 5 minutes or 30 seconds to 1 minute can be performed

Outside of the above range, if it is performed at too low rpm or the grinding time is short, there is a problem that sufficient grinding is not performed and powder of an inappropriate size for filming may occur, and if it is performed at too high rpm or for a long time , a lot of fine particles may be generated in the mixture mass, which is not preferable.

In one embodiment of the present invention, the particle size of the electrode mixture powder obtained in step (c) may preferably have a range of 30 μm to 180 μm in consideration of film formation.

In one embodiment of the present invention, the particle size may be measured by applying a particle size distribution analyzer (PSA) (Model Mastersizer 300, Malvem Instruments LTD). Specifically, a laser is irradiated, and the incident laser detects the degree of light scattering scattered by the particles, and through this, the particle diameter can be measured. As the measurement method, a wet method in which particles are dispersed in a solvent for measurement and a dry method in which particles are measured in a powder state may be applied.

Meanwhile, in the present invention, the crystallinity (c) of the binder resin included in the mixed electrode powder is 20% or less, and is lower than the crystallinity (a) of the binder resin included in the powdery blend. Meanwhile, the crystallinity (d) of the binder resin included in the dry electrode film after calendering may be higher. That is, crystallinity may be further reduced through the progress of the calendering step.

On the other hand, when the crystallinity (c) of the binder resin exceeds 20%, it is difficult to manufacture a film of uniform quality in a subsequent calendering process. If the crystallinity of the obtained electrode mixture powder exceeds 20%, the crystallinity can be adjusted by adjusting at least one of the preceding process conditions, kneading time, kneading temperature, rotation speed (rpm), and shear rate. For example, the degree of crystallinity can be adjusted by increasing the kneading time to promote fiberization of the binder.

In one embodiment of the present invention, the crystallinity (c) of the binder resin in the electrode mixture powder obtained in step (c) is preferably 20% or less. When the degree of crystallinity (c) exceeds 20%, fiberization is not sufficient, and the tensile strength and tensile elongation of the dry electrode obtained through the calendering process described below may be reduced.

In one embodiment of the present invention, in the mixed powder for electrode obtained in step (c), the crystallinity of the binder resin is checked, and when the confirmed crystallinity (c) is 20% or less, the process of step (c) , and the obtained result may be put into step (d). The degree of crystallinity can be confirmed at each step while processes (a) to (d) are performed.

Alternatively, in the result obtained in step (c), the process conditions in which the crystallinity of the binder resin can be controlled to 20% or less are experimentally confirmed, and the set process conditions are changed to the steps (b) and/or (c). can be applied to

In this way, when mixed powder for an electrode is obtained, a dry electrode is prepared using this powder for an electrode (step d). Specifically, a step of preparing a dry electrode film by calendering the mixed powder for an electrode prepared by completing the crushing step as described above is performed.

Such calendering may be a step of manufacturing the mixed powder for an electrode by processing it into a film form, for example, by pressing it into a film form to have an average thickness of 50 μm to 300 μm.

In one embodiment of the present invention, the calendering may be performed using a calendering device including a roll press unit in which two rollers are disposed to face each other. The calender may include at least one roll press unit. For example, since a plurality of the roll press units are continuously disposed, compression of the mixed powder for electrodes may be performed in multiple stages. Meanwhile, in the calendering device, the temperature of one or more rollers may be independently controlled at 50° C. to 200° C. Together with or independently of this, the rotation speed ratio of the two rollers in the at least one roll press unit may be controlled in a ratio of 1:1 to 1:3.

Proceeding to such a calendering step can produce a dry electrode film that serves as an electrode mixture. Such a dry electrode film is also referred to as a free standing film or a self-supporting film. Such dry electrode films may have sufficient mechanical strength to be used in the fabrication process of energy storage devices without any external support elements such as current collectors, support webs or other structures. Alternatively, it may be used in manufacturing a battery by combining with a support such as a current collector.

Meanwhile, in one embodiment of the present invention, the obtained dry electrode film has a crystallinity (d) of 10% or less of the binder resin in the dry electrode film. If the crystallinity of the obtained dry electrode film exceeds 10%, the crystallinity can be adjusted by adjusting the gap between the two rollers of the roll press unit or controlling the speed ratio. For example, the degree of fiberization of the binder may be increased by reducing the gap and/or increasing the speed ratio.

In one embodiment of the present invention, in the dry electrode film obtained in step (d), the crystallinity of the binder resin is checked, and when the confirmed crystallinity (d) is 10% or less, the process of step (d) can be terminated The degree of crystallinity can be confirmed at each stage while processes (a) to (d) are performed.

Alternatively, in the dry electrode film obtained in step (d), process conditions in which the crystallinity of the binder resin can be controlled to 10% or less may be experimentally confirmed, and the set process conditions may be applied to step (d). there is.

The dry electrode film produced in this way does not contain a solvent, has little fluidity, is easy to handle, and can be processed into a desired shape to be used in manufacturing various types of electrodes. In addition, if the dry electrode film of the present invention is used for electrode manufacturing, since the drying process for solvent removal can be omitted, not only can the manufacturing process of the electrode be greatly improved, but also problems in the manufacturing of conventional dry electrodes can be eliminated. It is possible to solve problems such as fine powder of an active material or breakage of a fibrous binder.

In addition, since the crystallinity of the binder resin included in the dry electrode film according to the present invention is controlled to 10% or less, the dry electrode film according to the present invention has an advantage of not breaking or cracking when it is wound and stored or unwound again due to increased flexibility. there is. In addition, mechanical strength, such as tensile strength and tensile elongation, can be improved according to the increase in flexibility.

Meanwhile, in the present invention, the dry electrode film may have a porosity of 20 vol% to 50 vol%, and may be preferably controlled to a value of 45 vol% or less or 40 vol% or less within the above range. When the porosity satisfies the above range, it is preferable in terms of various effects. On the other hand, outside the above range, if the porosity is too small, it is difficult to impregnate the electrolyte, which is undesirable in terms of life characteristics and output characteristics, and if it is too large, the volume to express the same capacity increases, in terms of energy density versus volume Not desirable. In one embodiment of the present invention, the porosity is obtained by measuring the apparent density of the dry electrode film and using the actual density calculated based on the actual density and composition of each component by the following [Relational Expression 2] can

[Relationship 2]

Porosity (vol%) = { 1 - (apparent density/actual density)} x 100

In addition, according to the present invention, after calendering, a lamination step of forming the dry electrode film on at least one surface of the current collector may be performed. The lamination may be a step of rolling and attaching the dry electrode film to a predetermined thickness on a current collector. The lamination may also be performed by a lamination roll, and at this time, the lamination roll may be maintained at a temperature of 20° C. to 200° C.

Meanwhile, in one embodiment of the present invention, the bending resistance of the dry electrode prepared above may be less than 10 mm phi (Φ), specifically 8 mm pie (Φ) or less, and more specifically 5 mm pie (Φ) or less. That is, as described above, since the dry electrode manufactured according to the present invention is less likely to break the fibrous binder, flexibility can be improved. The bending resistance may be performed according to the method of the measurement standard JIS K5600-5-1, and specifically, whether or not cracks occur by lifting both ends after contacting the prepared dry electrode with measuring rods of various diameters. It can be obtained by measuring and the minimum diameter at which cracks do not occur.

In addition, the active material loading amount of the dry electrode film may be 3 mAh/cm ² to 15 mAh/cm ² , and in detail, 4 mAh/cm ² to 10 mAh/cm ² .

Here, the loading amount of the active material is a value calculated by the method as shown in [Relationship 3] below.

[Relationship 3]

Loading amount (mAh/cm ² ) = Capacity of active material (mAh/g) x weight content ratio of active material in dry electrode film (wt%) x weight per unit area of dry electrode film (g/cm ² )

On the other hand, the current collector is not particularly limited as long as it does not cause chemical change in the battery and has high conductivity. For example, the surface of stainless steel, aluminum, nickel, titanium, fired carbon, copper, or aluminum or stainless steel. A surface treated with carbon, nickel, titanium, silver, or the like may be used. The current collector may also form fine irregularities on its surface to increase adhesion of the positive electrode active material, and various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics are possible.

Furthermore, the current collector may be coated entirely or partially with a conductive primer for lowering resistance and improving adhesion on the surface of the current collector. Here, the conductive primer may include a conductive material and a binder, and the conductive material may be, for example, a carbon-based material, although it is not limited thereto as long as it is a conductive material. The binder may include a solvent-soluble fluorine-based binder (including PVDF and PVDF copolymer), an acrylic binder, and an aqueous binder.

According to another embodiment of the present invention, a dry electrode manufactured by the dry electrode manufacturing method is provided. The electrode further includes a current collector, and the dry electrode film is disposed on at least one side or both sides of the current collector. In addition, as a secondary battery including the dry electrode, the dry electrode is a positive electrode, and a secondary battery in which an electrode assembly including the positive electrode, the negative electrode, and the separator is embedded in a battery case together with a lithium-containing non-aqueous electrolyte, and An energy storage device comprising a unit cell is provided.

At this time, since the specific structures of the secondary battery and the energy storage device are conventionally known, description thereof is omitted herein.

Meanwhile, in a specific embodiment of the present invention, a dry electrode manufacturing system is provided. The system includes a blender device for mixing raw materials including an electrode active material, a conductive material, and a binder resin; A kneader device for kneading the mixture to prepare a mixture lump; a pulverizing device that pulverizes the mass of the mixture to form mixed powder for an electrode; a calender device for forming the electrode powder into a dry electrode film; and a lamination device for laminating the dry electrode film and the current collector.

Each device of the system and each process performed using the device may have process conditions set in advance so that the binder resin exhibits the crystallinity described above in each step.

In addition, after performing each step process, a sample is taken to measure the degree of crystallinity, and if the standard is not met, the preset process conditions may be modified and reflected.

For example, when the crystallinity of the powder mixture obtained in the blender exceeds 50% or the result of measuring the crystallinity of the obtained mixed powder for an electrode exceeds 20%, each process time may be increased. there is. In addition, when the crystallinity of the electrode film obtained after the calendering process exceeds 10%, the crystallinity can be controlled by reducing the gap between rollers in the roll press unit or increasing the speed ratio.

Meanwhile, the blender device is a mixer for mixing raw materials, and as described above, the blend raw materials may be mixed at a speed of 500 rpm to 30,000 rpm.

The kneader device makes the mixture into a mixture lump through kneading and proceeds with fiberization of the binder. For this purpose, the kneader device may be set to a pressure condition in the range of 70 ° C to 200 ° C and normal pressure or higher. Specifically, 90 °C to 150 °C, 0.5 kgf/cm ² to 10 kgf/cm ² under pressure conditions, and more specifically, 1 kgf/cm ² to 8 kgf/cm ² pressure conditions.

The pulverization device is a device for pulverizing the mass of the mixture obtained in the kneader device to form powder for an electrode, and for example, a blender or a grinder may be used.

The calendering device is a device for compressing the powder for the electrode and molding it into a film form. In one specific embodiment of the present invention, the calendering device includes a roll press unit in which two rollers are disposed to face each other, and a plurality of roll press units are continuously disposed to perform multi-stage compression of powder. can

The lamination device serves to attach and roll the dry electrode film formed by the calender to at least one surface of the current collector, and a roll press device may be used, for example.

The porosity of the dry electrode dry electrode film according to the present invention can be determined by the calendering device and the lamination device. Specific structures of the blender device, the kneader device, the calender device, and the lamination device are conventionally known, and detailed descriptions thereof are omitted herein.

3 is a process flow chart showing a step-by-step method of manufacturing an electrode performed using the devices. Referring to this, first, a powdery mixture is prepared by blending an electrode active material, a binder resin, and a conductive material, and then the crystallinity of the binder resin is measured. If it is confirmed that the crystallinity of the binder resin is 50% or less, the powdery mixture is introduced into the next kneading process. However, if it is confirmed that the crystallinity exceeds 50%, the mixing time may be increased by performing a blending process again on the powdery mixture. At this time, the binder mass is pulverized into primary particles, and coarse fiberization may proceed.

Next, the obtained powdery blend is kneaded to obtain a mixture lump, which is pulverized to obtain a mixed powder for an electrode. If it is confirmed that the crystallinity of the binder resin in the obtained mixed powder for an electrode is 20% or less, the mixed powder for an electrode is introduced into the next calendering process. However, when it is confirmed that the crystallinity exceeds 20%, the mixed powder for electrode is put into the kneading process again.

Next, a dry electrode film is prepared by calendering the obtained mixed powder for an electrode. If the crystallinity of the prepared dry electrode film is confirmed to be 10% or less, the dry electrode film is put into a lamination process to manufacture an electrode. However, if it is confirmed that the crystallinity exceeds 10%, the crystallinity is adjusted by adjusting the distance between the rollers, controlling the speed ratio of the rollers, or both. Meanwhile, the process flow chart according to FIG. 3 can also be used to establish process conditions for achieving the required crystallinity in each step in electrode manufacturing.

Hereinafter, examples, comparative examples, and experimental examples according to the present invention will be described in detail in order to be easily understood by those skilled in the art to which the present invention belongs.

do.

Example 1

As cathode active materials, Li(Ni, Mn, Co, Al)O ₂ , activated carbon and polytetrafluoroethylene (PTFE) were put into a blender at a weight ratio of 96:1:3 and mixed at 15000 rpm for 1 minute to form a powder. A blend was prepared. Next, the temperature of the kneader was stabilized at 150° C., and the mixture was put into the kneader and operated at a speed of 25 rpm under a pressure of 1 kgf/cm ² for 5 minutes to obtain a lump of the mixture. The mixture lump was put into a blender and pulverized at 10000 rpm for 30 seconds to obtain mixed powder for an electrode. Thereafter, the mixed powder for the electrode was put into a lab calender (roll diameter: 200 mm, roll temperature: 100 ° C, roll speed ratio 1.5 conditions) to prepare a dry electrode film. Meanwhile, the positive electrode active material had a particle diameter of about 5 μm to 12 μm.

Example 2

Lithium iron phosphate (LFP), activated carbon, and polytetrafluoroethylene (PTFE) as cathode active materials were put into a blender at a ratio of 94:1.5:4.5 and mixed at 10000 rpm for 1 minute to prepare a powdery blend. Next, the temperature of the kneader was stabilized at 150° C., and the mixture was put into the kneader and operated at a speed of 50 rpm under a pressure of 1 kgf/cm ² for 5 minutes to obtain a lump of the mixture. The mixture lump was put into a blender and pulverized at 10000 rpm for 20 seconds to obtain mixed powder for an electrode. Thereafter, the mixed powder for the electrode was put into a lab calender (roll diameter: 200 mm, roll temperature: 100 ° C, roll speed ratio 1.75 conditions) to prepare a dry electrode film. Meanwhile, the positive electrode active material had a particle diameter of about 2 μm to 3 μm.

Example 3

As cathode active materials, Li(Ni, Mn, Co, Al)O ₂ , activated carbon, and polytetrafluoroethylene (PTFE) were put into a blender at a weight ratio of 96:1:3 and mixed at 15,000 rpm for 1 minute. A powdered blend was prepared. The positive electrode active material had a particle diameter of about 5 μm to about 12 μm.

Next, the temperature of the kneader was stabilized at 150° C., and the powdery blend was put into the kneader and operated at a speed of 25 rpm under a pressure of 1 kgf/cm ² for 2 minutes to obtain a mixture mass. The mixture lump was put into a blender and pulverized at 10000 rpm for 30 seconds to obtain mixed powder for an electrode. Thereafter, the mixed powder for the electrode was put into a lab calender (roll diameter: 200 mm, roll temperature: 100 ° C, roll speed ratio 1.5 conditions) to prepare a dry electrode film.

Comparative Example 1

Lithium iron phosphate (LFP), activated carbon, and polytetrafluoroethylene (PTFE) as cathode active materials were put into a blender at a ratio of 94:1.5:4.5 and mixed at 10,000 rpm for 1 minute to prepare a powdery blend. Next, the temperature of the kneader was stabilized at 150° C., and the mixture was put into the kneader and operated at a speed of 25 rpm under a pressure of 1 kgf/cm ² for 2 minutes to obtain a lump of the mixture. The mixture lump was put into a blender and pulverized at 10000 rpm for 20 seconds to obtain mixed powder for an electrode. Thereafter, the mixed powder for the electrode was put into a lab calender (roll diameter: 200 mm, roll temperature: 100 ° C, roll speed ratio 1.75 conditions) to prepare a dry electrode film. Meanwhile, the positive electrode active material had a particle diameter of about 2 μm to 3 μm.

Comparative Example 2

As cathode active materials, Li(Ni, Mn, Co, Al)O ₂ , activated carbon and polytetrafluoroethylene (PTFE) were put into a super mixer at a weight ratio of 96:1:3 and mixed at 400 rpm for 2 minutes. A powdered blend was prepared.

Next, the temperature of the kneader was stabilized at 150° C., and the mixture was put into the kneader and operated at a speed of 25 rpm under a pressure of 1 kgf/cm ² for 5 minutes to obtain a lump of the mixture. The mixture lump was put into a blender and pulverized at 10,000 rpm for 30 seconds to obtain mixed powder for an electrode. Thereafter, the mixed powder for the electrode was put into a lab calender (roll diameter: 200 mm, roll temperature: 100 ° C, roll speed ratio 1.5 conditions) to prepare a dry electrode film. Meanwhile, the positive electrode active material had a particle diameter of about 5 μm to 12 μm.

Comparative Example 3

As a cathode active material, Li(Ni, Mn, Co, Al)O ₂ , activated carbon, and polytetrafluoroethylene (PTFE) were put into a blender at a weight ratio of 96:1:3 and mixed at 15,000 rpm for 1 minute. . Then, the mixture was mixed for 30 seconds at 800 rpm in a super mixer. At this time, the temperature was maintained at 23° C. and the pressure was controlled at about 85 psi. A powdery blend was obtained in this way. Thereafter, the mixed powder for the electrode was put into a lab calender (roll diameter: 200 mm, roll temperature: 100 ° C, roll speed ratio 1.5 conditions) to prepare a dry electrode film. Meanwhile, the positive electrode active material had a particle diameter of about 5 μm to 12 μm.

As can be seen in [Table 1], in Examples 1 to 3, the crystallinity of the powder blend was 50% or less, the crystallinity of the mixed powder for electrode was 20% or less, and the crystallinity of the dry electrode film was 10% controlled below. 1 is a graph showing the DSC thermal analysis results of Example 1. According to this, it was confirmed that the crystallinity of the mixed powder for electrode (griding) and the dry electrode film (sheet) processed later were lower than those of the powdery blend (Mixing). 2 is a graph showing the DSC thermal analysis results of Example 2. In Example 2, it was confirmed that the crystallinity of the mixed powder for electrodes (Grinding) and the dry electrode film (Sheet) processed later were lower than those of the powdery blend (Mixing). In addition, in the dry electrode films obtained in each example, the tensile strength was confirmed to be 0.5 Mpa or more, and the tensile elongation was also 2% or more. On the other hand, the PTFE of FIG. 2 is a measure of the inherent crystallinity of 100% PTFE before processing, and is listed for comparison with the degree of crystallization of PTFE after processing.

On the other hand, in Comparative Examples 1 to 2, it was confirmed that the crystallinity of the binder resin of the obtained electrode mixture powder exceeded 20%. This means that fiberization was insufficient in the obtained mixed powder for electrodes, and it was difficult to prepare a sheet-shaped dry electrode film through a calendering process thereafter. In particular, in Comparative Example 2, since the crystallinity of the binder resin in the powdery blend exceeded 60%, it was confirmed that sufficient fiberization was not achieved even after the subsequent process. On the other hand, in Comparative Example 3, it was confirmed that the kneading process according to the present invention was not applied, so that fine fiberization was not sufficiently achieved, and therefore, even after calendering, it was confirmed that it could not be made into a sheet.

- Measurement of crystallinity

In each of Examples and Comparative Examples, samples for measuring crystallinity were prepared from the powdery blend, the mixed powder for electrode, and the dry electrode film. For each sample, the crystallinity (Xc) was measured by weighing and introducing about 5 mg to 12 mg of the sample to TA's differential scanning calorimetry (DSC), and increasing the temperature at a rate of 10 ° C / min in a temperature range of 25 to 360 ° C in a nitrogen atmosphere The heat of fusion (Δ heat of fusion) was measured according to the temperature while doing so.

Melting point (Tm) and melting enthalpy (ΔHm) were analyzed based on the temperature (peak temperature) at the time of melting with the highest enthalpy using TA's TROIS program. The crystallinity of each sample is expressed in % by dividing the melting enthalpy (ΔHm) value actually measured by DSC by the melting enthalpy (ΔHm0) value of a theoretically perfect crystal (crystallinity 100%), and was calculated by the above relational expression 1. The melting enthalpy value of the theoretical perfect crystal of PTFE was 85.4 J/g, and reference was made to pages 8872-8882 of Polymer magazine 46 (2005).

- Measurement of tensile strength and tensile elongation

After cutting the dry electrode film obtained in each Example and Comparative Example to a width of 10 mm, it was measured three times at a tensile speed of 5 mm/min using a tensile strength tester, and the results were averaged. Tensile strength is a measure of the stress applied until fracture occurs, and tensile elongation represents the ratio of elongation of a specimen stretched until fracture occurs (%, ratio of length change to original length).

Claims (20)

1. It includes a dry electrode film manufactured by a dry manufacturing process that does not use a solvent, wherein the dry electrode film includes an electrode active material, a conductive material, and a binder resin, and the binder resin included in the dry electrode film has a crystallinity of 10%. An electrode for an electrochemical device of the following.
2. According to claim 1,

   The dry electrode film is an electrode for an electrochemical device having a tensile strength of 0.5 MPa or more in the machine direction (MD).
3. According to claim 1,

   The dry electrode film is an electrode for an electrochemical device having a tensile elongation of 2% or more.
4. According to claim 1,

   The electrode film is an electrode for an electrochemical device having a porosity of 20 vol% to 50 vol%.
5. A method for manufacturing an electrode for an electrochemical device according to claim 1,

   The above method

   (a) preparing a powdery blend comprising an electrode active material, a conductive material, and a binder resin;

   (b) preparing a mixture lump by kneading the powdery mixture under a temperature condition of 70° C. to 200° C.;

   (c) obtaining a mixed powder for an electrode by pulverizing the mass of the mixture; and

   (d) calendering the electrode mixture powder to obtain a free standing type dry electrode film;

   The crystallinity (d) of the binder resin included in the dry electrode film obtained in step (d) is a method for producing an electrode for an electrochemical device that is 10% or less.
6. According to claim 5,

   The crystallinity (c) of the binder resin contained in the mixed powder for electrodes obtained in step (c) is a method for producing an electrode for an electrochemical device that is 20% or less.
7. According to claim 5,

   A method for producing an electrode for an electrochemical device in which the crystallinity (a) of the binder resin contained in the mixture obtained in step (a) is 50% or less.
8. According to claim 5,

   Step (a) is a method for producing an electrode for an electrochemical device that is performed under conditions of 500 rpm to 30,000 rpm.
9. According to claim 5,

   The step (b) is a method for producing an electrode for an electrochemical device that is carried out at a speed of 100 rpm or less.
10. According to claim 5,

    The step (b) is 0.5kgf / cm ² to 10kgf / cm ² Method for producing an electrode for an electrochemical device that is carried out under pressure.
11. According to claim 5,

    Step (b) is a method for producing an electrode for an electrochemical device that is carried out under normal pressure or higher conditions.
12. According to claim 1,

    The binder resin is an electrode for an electrochemical device comprising polytetrafluoroethylene (PTFE), PVDF (Polyvinylidene fluoride), polyolefin, or a mixture of two or more of them.
13. According to claim 1,

    An electrode for an electrochemical device further comprising a current collector, wherein the dry electrode film is disposed on at least one side surface or both sides of the current collector.
14. According to claim 5,

    Preparing a current collector, and disposing and laminating the dry electrode film on at least one side of the current collector.
15. A dry electrode according to claim 1,

    The dry electrode is a positive electrode, and an electrode assembly including the positive electrode, the negative electrode, and the separator is embedded in a battery case together with a lithium-containing non-aqueous electrolyte.
16. An energy storage device comprising the secondary battery according to claim 15 as a unit battery.
17. As for a method for producing electrode powder for producing a dry electrode film,

    The manufacturing method

    (a) preparing a powdery blend comprising an electrode active material, a conductive material, and a binder resin;

    (b) kneading the powdery blend at a temperature in the range of 70° C. to 200° C. to prepare a mixture mass; and

    (c) a process of pulverizing the mixture lump to obtain a mixed powder for an electrode; including,

    The binder resin included in the electrode powder has a crystallinity of 20% or less,

    The binder resin is a method for producing a mixed powder for an electrode comprising polytetrafluoroethylene (PTFE), polyolefin, or a mixture thereof.
18. A mixed powder for an electrode prepared by the method according to claim 17, wherein the mixed powder for an electrode includes an electrode active material, a conductive material, and a binder resin, and the binder resin is polytetrafluoroethylene (PTFE), PVDF , polyolefin, or a mixture of two or more of them, and the crystallinity of the binder resin included in the mixed powder for electrodes is 20% or less.
19. Calendering the mixed powder for electrode to obtain a free standing type dry electrode film, wherein the mixed powder for electrode is obtained by the method according to claim 17, and the binder included in the electrolytic electrode film A method for producing a dry electrode film in which the crystallinity (d) of the resin is 10% or less.
20. A dry electrode film produced by the method according to claim 19, having a tensile strength of 0.5 MPa or more in the machine direction (MD), a tensile elongation of 2% or more, and a porosity of 20 vol% to 50 vol%.

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