KR20220050449A - Method of evaluating the degree of secession of electrode active material - Google Patents

Abstract

The present invention relates to a method for evaluating electrode active material detachment, comprising the following steps of: manufacturing an electrode having a structure in which an electrode active material layer is formed on a current collector; measuring a weight reduction rate of the electrode before and after sonication; and comparing the weight reduction rate with a reference value to predict whether an electrode active material is detached or not. An objective of the present invention is to provide the method for evaluating the electrode active material detachment capable of minimizing occurrence of defects and process loss.

Description

Electrode active material removal evaluation method {METHOD OF EVALUATING THE DEGREE OF SECESSION OF ELECTRODE ACTIVE MATERIAL}

The present invention relates to a method for evaluating the degree of desorption of an electrode active material, and more particularly, to a method for evaluating the degree of desorption of an electrode active material from a weight reduction rate measurement value before and after sonication of an electrode.

Recently, rechargeable batteries capable of charging and discharging have been widely used as energy sources for wireless mobile devices. In addition, the secondary battery is attracting attention as an energy source for electric vehicles, hybrid electric vehicles, etc., which have been proposed as a way to solve air pollution of conventional gasoline vehicles and diesel vehicles using fossil fuels. Accordingly, the types of applications using secondary batteries are diversifying due to the advantages of secondary batteries, and it is expected that secondary batteries will be applied to more fields and products in the future than now.

These secondary batteries are sometimes classified into lithium ion batteries, lithium ion polymer batteries, lithium polymer batteries, etc. depending on the composition of the electrode and electrolyte. is increasing In general, secondary batteries, depending on the shape of the battery case, a cylindrical battery and a prismatic battery in which the electrode assembly is built in a cylindrical or prismatic metal can, and a pouch-type battery in which the electrode assembly is built in a pouch-type case of an aluminum laminate sheet The electrode assembly built into the battery case consists of a positive electrode, a negative electrode, and a separator structure interposed between the positive electrode and the negative electrode, and is a power generating element capable of charging and discharging. It is classified into a jelly-roll type wound with a separator interposed therebetween, and a stack type in which a plurality of positive and negative electrodes of a predetermined size are sequentially stacked with a separator interposed therebetween.

The positive electrode and the negative electrode are formed by applying a positive electrode slurry containing a positive electrode active material and a negative electrode slurry containing a negative electrode active material to a positive electrode current collector and a negative electrode current collector, respectively, and drying and rolling them. At this time, a small amount of a binder is added to the positive electrode slurry and the negative electrode slurry to prevent the active material from being detached from the current collector.

However, even in this case, the electrode active material is frequently detached from the cut portion of the current collector during the manufacturing process of the electrode, for example, in the process of cutting, notching, slitting, and laminating the electrode. As such, when the electrode active material is detached from the current collector, the possibility of a short circuit due to the detached electrode debris increases, which increases the defect rate of the electrode. That is, since the adhesion of the electrode active material to the current collector is a major factor affecting the manufacturing processability of the battery and the performance of the battery, it is important to predict and evaluate the degree of desorption of the electrode active material. However, since there is no evaluation method for predicting the degree of desorption of the electrode active material, it is difficult to confirm the phenomenon without going through an actual process.

Korean Patent Application Laid-Open No. 10-2017-0068977 discloses a method for measuring the adhesion of an electrode active material to a current collector. Specifically, in the literature, a method of measuring the peel strength of an electrode active material is known in order to confirm the adhesion of the electrode active material to the current collector, and in order to improve this, the electrode is punched, and thus the amount of detachment of the electrode active material is measured A method is disclosed.

However, in the actual process, the electrode active material is mostly detached due to cutting and punching, so it is difficult to accurately measure the electrode adhesion strength only by measuring the peel strength, and the measurement method of directly punching the electrode determines the degree of detachment due to external factors other than punching. The problem is that it cannot be evaluated. In addition, the conventional method has a problem that the evaluation method is complicated and cumbersome, since it is necessary to directly evaluate the degree of detachment of the active material by cutting or punching the electrodes one by one.

Therefore, there is a need to develop a technology capable of predicting and evaluating the degree of desorption of the electrode active material.

Korean Patent Publication No. 10-2017-0068977

The present invention has been devised to solve the above problems, and it is possible to minimize the occurrence of defects and process losses by predicting detachment without measuring the adhesion to the electrode active material, laminating the electrode, notching, or the like. An object of the present invention is to provide a method for evaluating the desorption of an active material.

In one example, the electrode active material detachment evaluation method according to the present invention includes manufacturing an electrode having a structure in which an electrode active material layer is formed on a current collector; measuring a weight reduction rate before and after sonication of the electrode; and comparing the weight reduction rate with a reference value to predict whether the electrode active material is defective in detachment.

In a specific example, the step of measuring the weight reduction ratio before and after sonication of the electrode includes the process of measuring the weight reduction ratio before and after applying the ultrasonic wave after applying ultrasonic waves by putting the electrode into a water tank filled with water, drying it.

In a specific example, the electrode active material desorption evaluation method according to the present invention further includes deriving the reference value.

In this case, the step of deriving the reference value includes: manufacturing an electrode specimen and measuring a weight reduction rate before and after sonication of the electrode specimen; The process of cutting the electrode specimen whose weight reduction rate is measured, and confirming the amount of desorption of the electrode active material; and deriving a correlation between the weight reduction rate before and after sonication and the amount of desorption of the electrode active material.

In a specific example, the process of deriving the correlation between the weight reduction rate before and after sonication and the amount of desorption of the electrode active material includes building a database of the amount of desorption of the electrode active material according to the weight reduction rate before and after sonication.

In a specific example, the reference value may be derived from the database.

In a specific example, the step of deriving the reference value includes setting a desorption amount value of an electrode active material that is a criterion for determining whether a defect is present, and before and after sonication of an electrode specimen indicating a desorption amount value of the electrode active material serving as the reference in the database and setting a reference value from the weight reduction rate value.

At this time, when the weight reduction rate before and after sonication is less than the reference value, the electrode may be determined as a good product.

In another example, the method for evaluating desorption of an electrode active material according to the present invention further includes measuring a weight reduction rate before and after sonication of the electrode under different conditions, and predicting whether the desorption of the electrode active material is defective therefrom.

In a specific example, the condition may include the composition of the electrode active material layer or the temperature of the electrode.

In addition, the electrode active material detachment evaluation method according to the present invention further includes deriving a reference value according to the manufacturing conditions of the electrode from the weight reduction rate before and after sonication of the electrode according to the condition.

In a specific example, the electrode may be a negative electrode.

In the electrode active material desorption evaluation method according to the present invention, the desorption degree of the electrode active material can be predicted and evaluated only by measuring the weight reduction rate before and after sonication of the electrode without the need to evaluate the desorption degree by putting it into an actual process after manufacturing the electrode. It can save time and money required for evaluation.

In addition, by predicting the degree of desorption of the electrode active material in advance prior to the input of the electrode, it is possible to minimize the occurrence of defects and process loss.

1 is a flowchart illustrating a procedure of a method for evaluating detachment of an electrode active material according to an embodiment of the present invention.
2 and 3 are flowcharts illustrating a procedure of a method for evaluating desorption of an electrode active material according to another embodiment of the present invention.
4 is a schematic diagram illustrating a method for determining whether an electrode active material is desorbed in the electrode active material desorption evaluation method according to the present invention.
5 is a graph showing the amount of desorption of the electrode active material according to the weight reduction rate before and after sonication of the electrode.
6 is a photograph showing the state after cutting the electrodes according to Preparation Examples 1, 5, 10.

Hereinafter, the present invention will be described in detail. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor should properly understand the concept of the term in order to best describe his invention. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined in

In the present application, terms such as "comprise" or "have" are intended to designate that a feature, number, step, operation, component, part, or a combination thereof described in the specification exists, but one or more other features It is to be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof. Also, when a part of a layer, film, region, plate, etc. is said to be “on” another part, it includes not only the case where the other part is “directly on” but also the case where there is another part in between. Conversely, when a part of a layer, film, region, plate, etc. is said to be “under” another part, it includes not only cases where it is “directly under” another part, but also cases where another part is in between. In addition, in the present application, “on” may include the case of being disposed not only on the upper part but also on the lower part.

Hereinafter, the present invention will be described in detail.

1 is a flowchart illustrating a procedure of a method for evaluating detachment of an electrode active material according to an embodiment of the present invention.

Referring to FIG. 1 , the method for evaluating desorption of an electrode active material according to the present invention includes manufacturing an electrode having a structure in which an electrode active material layer is formed on a current collector (S10); Measuring the weight reduction rate before and after sonication of the electrode (S11); and comparing the weight reduction rate with a reference value to predict whether the electrode active material is defective or not (S12).

As described above, in the prior art, the electrode manufactured for desorption evaluation had to be put into the actual process or put into an apparatus that simulates the actual process and the degree of desorption had to be directly evaluated. There is a problem that the device cannot reflect all situations.

The electrode active material desorption evaluation method according to the present invention can predict and evaluate the desorption degree of the electrode active material only by measuring the weight reduction rate before and after sonication without the need to evaluate the desorption degree by putting it into an actual process after manufacturing the electrode. You can save time and money to do it.

In addition, by predicting the degree of desorption of the electrode active material before and after the electrode is inserted through the measurement of the weight reduction rate before and after sonication, the occurrence of defects and process loss can be minimized.

Hereinafter, each step of the evaluation method according to the present invention will be described in detail.

<Production of electrode>

First, an electrode to be evaluated is manufactured.

The electrode may have a structure in which an electrode active material layer is formed by applying an electrode slurry including an electrode active material on a current collector, drying and rolling the electrode slurry.

The current collector may be a positive electrode current collector or a negative electrode current collector, and the electrode active material may be a positive electrode active material or a negative electrode active material. In addition, the electrode slurry may further include a conductive material and a binder in addition to the electrode active material.

In addition, the electrode may be a positive electrode or a negative electrode, and more specifically, may be a negative electrode in which an active material desorption issue frequently occurs.

In the present invention, the positive electrode current collector is generally made to have a thickness of 3 to 500 μm. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel. Carbon, nickel, titanium, silver, etc. surface-treated on the surface of the can be used. The current collector may increase the adhesion of the positive electrode active material by forming fine irregularities on the surface thereof, and various forms such as a film, sheet, foil, net, porous body, foam body, and non-woven body are possible.

In the case of a sheet for a negative electrode current collector, it is generally made to a thickness of 3 to 500 μm. Such a negative current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel. Carbon, nickel, titanium, a surface-treated material such as silver, aluminum-cadmium alloy, etc. may be used. In addition, like the positive electrode current collector, the bonding strength of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven body, and the like.

In the present invention, the positive active material is a material capable of causing an electrochemical reaction, as a lithium transition metal oxide, containing two or more transition metals, for example, lithium cobalt oxide (LiCoO ₂ ) substituted with one or more transition metals. ), layered compounds such as lithium nickel oxide (LiNiO ₂ ); lithium manganese oxide substituted with one or more transition metals; Formula LiNi _1-y M _y O ₂ (wherein M = Co, Mn, Al, Cu, Fe, Mg, B, Cr, Zn or Ga, including at least one of the above elements, 0.01≤y≤0.7) Lithium nickel-based oxide represented by; Li _1+z Ni _1/3 Co _1/3 Mn _1/3 O ₂ , Li _1+z Ni _0.4 Mn _0.4 Co _0.2 O ₂ , etc. Li _1+z Ni _b Mn _c Co _{1-(b+c+d )} M _d O _(2-e) A _e (where -0.5≤z≤0.5, 0.1≤b≤0.8, 0.1≤c≤0.8, 0≤d≤0.2, 0≤e≤0.2, b+c+d <1, M = Al, Mg, Cr, Ti, Si or Y, and A = F, P or Cl) a lithium nickel cobalt manganese composite oxide; Formula Li _1+x M _1-y M' _y PO _4-z X _z where M = transition metal, preferably Fe, Mn, Co or Ni, M' = Al, Mg or Ti, X = F, S, or N, and -0.5≤x≤+0.5, 0≤y≤0.5, 0≤z≤0.1 olivine-based lithium metal phosphate represented by), but is not limited thereto.

The negative electrode active material includes, for example, carbon such as non-graphitizable carbon and graphitic 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, halogen; 0<x≤1;1≤y≤3;1≤z≤8); lithium metal; lithium alloy; silicon-based alloys; tin-based alloys; 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 , 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.

The conductive material is typically added in an amount of 1 to 30% by weight based on the total weight of the mixture including the positive active material. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, 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.

The binder is a component that assists in bonding between the active material and the conductive material and bonding to the current collector, and is typically added in an amount of 1 to 30% by weight based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, poly propylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butyrene rubber, fluororubber, various copolymers, and the like.

<Measurement of weight loss before and after sonication>

When the electrode manufacturing is completed, a weight reduction rate before and after sonication of the electrode is measured as a factor indicating the degree of detachment of the electrode active material.

The step of measuring the weight reduction rate before and after sonication of the electrode includes the process of measuring the weight reduction rate before and after applying the ultrasonic wave after applying the ultrasonic wave by putting the electrode into a water tank filled with water and drying it.

Specifically, the measurement target electrode is cut to a predetermined size, and then the weight of the electrode is measured before sonication. Then, the electrode is immersed in a beaker containing water, and the beaker is accommodated in a water tank containing water. After that, the electrode is irradiated with ultrasonic waves, and when this process is completed, the electrode is taken out and dried naturally at room temperature, and then the weight of the electrode is measured after sonication. At this time, as described above, sonication is performed in a state in which the beaker containing water and electrodes is accommodated in the water tank, and ultrasonic vibrations generated from the ultrasonic generator may be transmitted to the electrodes contained in the beaker through the water contained in the water tank, but the electrode is immersed in a water bath containing water, and ultrasonic vibrations can be directly applied to the water bath containing the electrodes by connecting an ultrasonic generator to the water bath.

Meanwhile, the weight reduction rate before and after sonication of the electrode may be calculated by Equation 1 below.

[Equation 1]

In the present invention, the weight reduction rate before and after sonication of the electrode is an indicator capable of representing the detachment characteristic of the electrode active material layer. A small weight reduction ratio before and after sonication means that the degree of deformation of the electrode active material layer with respect to an external force is small. That is, the small weight reduction rate before and after sonication indicates that the particles constituting the electrode active material layer are strongly bound to each other, and the particles constituting the electrode active material layer are strongly adhered to the current collector, indicating that the resistance to ultrasonic vibration is large. it means. Conversely, the large weight reduction rate before and after sonication means that the particles constituting the electrode active material layer are weakly bound to each other, and the particles constituting the electrode active material layer are weakly adhered to the current collector, indicating that the resistance to ultrasonic vibration is weak. means that Therefore, the smaller the weight reduction rate before and after sonication of the electrode, the smaller the desorption amount of the electrode active material will be.

<derivation of reference value>

When the weight reduction rate before and after sonication of the electrode is measured, the measured value and the reference value are compared to predict whether the electrode active material is defective in detachment. In this case, the defective detachment means a case in which the amount of detachment of the electrode active material exceeds a predetermined value when the electrode is cut. To this end, the electrode active material desorption evaluation method according to the present invention may further include deriving the reference value. The reference value derivation may be performed prior to the step of manufacturing the electrode.

The deriving the reference value may include: manufacturing an electrode specimen and measuring a weight reduction rate before and after sonication of the electrode specimen; The process of cutting the electrode specimen whose weight reduction rate is measured, and confirming the amount of desorption of the electrode active material; and deriving a correlation between the weight reduction rate before and after sonication and the amount of desorption of the electrode active material.

The electrode specimen may be prepared in the same manner as the electrode to be evaluated. That is, it can be prepared by coating an electrode slurry having the same composition on a current collector having the same thickness and material as that of the electrode to be evaluated, followed by drying and rolling.

The weight reduction rate of the prepared electrode specimen before and after sonication can be measured by the method described above.

As such, when the weight reduction rate before and after sonication of the electrode specimen is measured, a correlation between the weight reduction rate before and after sonication and the amount of desorption of the electrode active material is derived. Specifically, the electrode specimen for which the weight reduction rate is measured before and after sonication is cut, and the amount of detachment of the electrode active material is measured along the cut surface. In this case, the desorption amount of the electrode active material means the weight of the desorbed electrode active material compared to the length of the portion where the desorption occurs. In addition, the correlation between the weight loss rate before and after sonication and the amount of desorption of the electrode active material means a tendency indicated by the measured value of the amount of desorption of the electrode active material according to the measured value of the weight loss rate before and after sonication.

In addition, the process of deriving the correlation between the amount of desorption of the electrode active material according to the weight reduction rate before and after sonication includes the process of constructing a database for the amount of desorption of the electrode active material according to the weight reduction rate before and after the sonication. This is to understand the tendency indicated by the measured value of the amount of desorption of the electrode active material with respect to the weight reduction rate before and after sonication as described above. To this end, after manufacturing a plurality of electrode specimens, the weight reduction rate before and after sonication is measured, and the amount of desorption of the electrode active material is measured accordingly, and the result can be accumulated in a storage system such as a memory. data can be recorded. At this time, it is preferable to perform the measurement on as many electrode specimens as possible for the accuracy of the measurement.

When the correlation between the weight reduction rate before and after sonication and the amount of desorption of the electrode active material is derived, a reference value for determining whether the electrode active material is defective is derived from this. This reference value is derived from the database.

Specifically, in the step of deriving the reference value, the value of the desorption amount of the electrode active material serving as a criterion for determining whether defective is set, and the weight before and after sonication of the electrode specimen indicating the desorption amount value of the electrode active material serving as the reference in the database and setting a reference value from the reduction rate value. The value of the desorption amount of the electrode active material serving as a criterion for determining whether the defect is present may be determined according to the performance of the electrode to be implemented.

For example, if the desorption amount of the electrode active material for realizing the performance of the electrode to be achieved is less than x μg/m, the weight reduction rate value before and after sonication of the electrode showing such an electrode active material desorption value in the database is selected as a reference value. can

<Prediction of tally or not>

When the reference value is derived and the measurement of the weight reduction rate before and after sonication of the electrode is completed, it is predicted whether the electrode active material is defective or not. If the weight reduction rate before and after sonication is less than the reference value, the electrode can be judged as a good product. The electrode determined as a good product corresponds to an electrode in which the desorption of the electrode active material is expected to be less than or equal to a predetermined value. In this case, it can be predicted that the electrode manufactured under the same conditions as the evaluation target electrode that received a good judgment is good quality.

The electrode active material detachment evaluation method according to the present invention uses a reference value derived from the weight reduction rate data before and after sonication of the electrode, and the measured value of the weight reduction rate before and after sonication of the electrode without the need to check whether the electrode is detached by putting the manufactured electrode into the actual process It is possible to predict and evaluate the presence of tally only, so that time and cost required for evaluating whether tally or not can be saved. In addition, it is possible to minimize the occurrence of defects and process losses by predicting in advance whether the electrode active material is desorbed or not before the electrode is inserted.

2 and 3 are flowcharts illustrating a procedure of a method for evaluating desorption of an electrode active material according to another embodiment of the present invention.

In another example, the method for evaluating desorption of an electrode active material according to the present invention further includes measuring a weight reduction rate before and after sonication of the electrode under different conditions, and predicting whether the desorption of the electrode active material is defective therefrom. The condition may include the composition of the electrode active material layer or the temperature of the electrode. The composition of the electrode active material layer and the temperature of the electrode are directly related to the adhesion of the electrode active material layer to the current collector. For example, the composition of the electrode active material layer may be changed by varying the binder content, and physical properties of the electrode active material layer may be changed by varying the temperature of the electrode. The present invention can predict the performance of the electrode according to the temperature and the composition of the electrode, etc. by additionally considering variables such as temperature and the composition of the electrode in the evaluation of the desorption of the electrode active material, and to minimize the desorption of the electrode active material in the electrode manufacturing process. Optimal conditions can be derived.

Specifically, referring to FIG. 2 , the method for evaluating desorption of an electrode active material according to the present invention includes manufacturing an electrode having a structure in which an electrode active material layer is formed on a current collector by changing a composition ( S20 ); Measuring a weight reduction rate before and after sonication of the electrode with respect to the electrode (S21); and comparing the measured value of the weight reduction rate before and after the sonication with a reference value to predict whether the electrode active material is defective in detachment (S22).

Alternatively, referring to FIG. 3 , the method for evaluating desorption of an electrode active material according to the present invention includes manufacturing an electrode having a structure in which an electrode active material layer is formed on a current collector (S30); measuring the weight reduction rate before and after sonication of the electrode by varying the temperature of the electrode with respect to the electrode (S31); and comparing the measured value of the weight reduction rate before and after the sonication with a reference value to predict whether the electrode active material is detached (S32).

To this end, the electrode active material detachment evaluation method according to the present invention further includes deriving a reference value according to the condition from the weight reduction rate before and after sonication of the electrode according to the condition. A method of deriving the reference value is the same as described above. Specifically, it is possible to measure the weight reduction rate before and after sonication of the electrode specimen under different conditions, check whether the electrode active material is detached from the electrode specimen, build a database, and derive a reference value according to the condition from the database.

Hereinafter, examples will be given to help the understanding of the present invention be described in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the following examples. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

Example

<Preparation of electrode specimen>

97.6 parts by weight of artificial graphite and natural graphite (weight ratio: 90:10) functioning as an anode active material, 1.2 parts by weight of styrene-butadiene rubber (SBR) functioning as a binder, 1.2 parts by weight of carboxymethyl cellulose (CMC) , a negative electrode mixture was prepared. A negative electrode slurry was prepared by dispersing this negative electrode mixture in ion-exchanged water serving as a solvent. This slurry was coated on both sides of a copper foil having a thickness of 20 μm, dried and compressed to prepare an electrode specimen 1 having an active material layer 2 formed thereon as shown in FIG. 3 .

<Measurement of weight loss before and after sonication>

After 50 electrode specimens were prepared, a weight reduction rate before and after sonication was measured for each electrode specimen.

Specifically, the electrode specimen was cut to a size of 5 cm x 5 cm and the weight before sonication was measured. Then, the cut electrode specimen was immersed in a beaker containing 200 ml of water, and the beaker was accommodated in a water tank containing 3.6 L of water. With respect to the water tank, sonication was performed for 2 minutes at 'up' at ultrasonic intensity using a sonication device (Lab Companion UC-10). When the sonication was completed, the electrode specimen was taken out and the surface moisture was dried naturally at room temperature, and then the sonication weight was measured. Then, the weight reduction rate before and after sonication of the electrode was measured according to Equation 1 below.

[Equation 1]

<derivation of reference value>

Then, the electrode specimen was cut in a direction (A) perpendicular to the coating direction (MD direction) of the electrode as shown in FIG. 4 , and then the amount of desorption of the electrode active material was measured. The desorption amount of the electrode active material is the weight of the desorbed electrode active material compared to the length of the portion where the desorption occurs, and may be calculated as shown in Equation 2 below.

[Equation 2]

From the measurement results, the weight reduction rate before and after sonication of the electrode specimen and the amount of desorption of the electrode active material according to it were databased, and a reference value for judging whether or not the electrode active material was defective was set.

Specifically, the criterion for judging the electrode as a good quality was set to a desorption amount of the electrode active material of 10 μg/m or less. Accordingly, an electrode specimen in the case where the amount of desorption of the electrode active material was 10 μg/m was selected, and a weight reduction rate value before and after sonication of the electrode specimen was set as a reference value. At this time, the reference value of the weight reduction rate before and after sonication was set to 15%.

<Prediction of electrode manufacturing and active material detachment>

11 electrodes were prepared in the same manner as in the method for preparing the electrode specimen described above (Preparation Examples 1 to 11). The weight reduction rate before and after sonication was measured for the electrode. The results are shown in Table 1 and FIG. 5 below.

On the other hand, with respect to the electrode, it was determined that the weight reduction rate before and after sonication was 15% or less as good products.

Experimental example

The electrode was cut in the same manner as described above, and the amount of desorption of the electrode active material was measured in the same manner as described above. The results are shown in Table 1 and FIG. 5 . In addition, pictures showing the appearance after cutting of Preparation Examples 1, 5, and 10 are shown in FIG. 6 . 6, (a), (b) and (c) are photographs showing the appearance after cutting of Preparation Examples 1, 5 and 10, respectively.

Sample Weight reduction rate (%) Judgment Desorption amount (㎍/m) Preparation Example 1 45.41 error 137.0 Preparation 2 37.34 error 141.0 Preparation 3 35.89 error 142.7 Preparation 4 6.14 Good 0.6 Preparation 5 14.54 Good 8.3 Preparation 6 4.23 Good 2.3 Preparation 7 5.74 Good 0.3 Preparation 8 4.95 Good 0.3 Preparation 9 5.00 Good 0.8 Preparation 10 3.25 Good 0.8 Preparation 11 4.73 Good 0.3

Referring to Table 1 and FIGS. 5 and 6, when the weight reduction rate is small, the desorption amount also tends to be small. In addition, the electrode determined to be good quality (the electrode having a weight reduction rate of 15% or less of the set reference value) had an electrode active material desorption amount of less than 10 μg/m, indicating a good electrode desorption degree.

As described above, according to the present invention, since the degree of desorption of the electrode active material can be predicted and evaluated only by measuring the weight reduction rate before and after sonication of the electrode, the time and cost required for evaluating the desorption degree can be saved. In addition, by predicting the degree of desorption of the electrode active material in advance prior to the input of the electrode, it is possible to minimize the occurrence of defects and process loss.

The above description is merely illustrative of the technical spirit of the present invention, and various modifications and variations will be possible without departing from the essential characteristics of the present invention by those skilled in the art to which the present invention pertains. Accordingly, the drawings disclosed in the present invention are for explanation rather than limiting the technical spirit of the present invention, and the scope of the technical spirit of the present invention is not limited by these drawings. The protection scope of the present invention should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Meanwhile, in this specification, terms indicating directions such as up, down, left, right, front, and back are used, but these terms are for convenience of explanation only, and may vary depending on the location of the object or the position of the observer. It is self-evident that it can

1: electrode specimen
2: Active material layer

Claims (12)

manufacturing an electrode having a structure in which an electrode active material layer is formed on a current collector;
measuring a weight reduction rate before and after sonication of the electrode; and
and estimating whether or not the electrode active material is defective by comparing the weight reduction rate with a reference value.
According to claim 1,
Measuring the weight reduction rate before and after sonication of the electrode,
An electrode active material desorption evaluation method, comprising: applying an ultrasonic wave by putting an electrode into a water tank filled with water, drying the electrode, and measuring a weight reduction rate before and after applying ultrasonic wave.
According to claim 1,
The electrode active material detachment evaluation method further comprising the step of deriving the reference value.
4. The method of claim 3,
The step of deriving the reference value is
The process of preparing an electrode specimen and measuring a weight reduction rate before and after sonication of the electrode specimen;
The process of cutting the electrode specimen whose weight reduction rate is measured, and confirming the amount of desorption of the electrode active material; and
An electrode active material desorption evaluation method comprising the process of deriving a correlation between a weight reduction rate before and after sonication and an electrode active material desorption amount.
5. The method of claim 4,
The process of deriving the correlation between the weight reduction rate before and after sonication and the amount of desorption of the electrode active material is,
A method for evaluating desorption of an electrode active material, comprising the process of establishing a database on the amount of desorption of an electrode active material according to a weight reduction rate before and after sonication.
6. The method of claim 5,
The reference value is an electrode active material desorption evaluation method derived from the database.
7. The method of claim 6,
The step of deriving the reference value is
Set the value of the amount of desorption of the electrode active material, which is the standard for determining whether or not there is a defect,
and setting a reference value from the value of the weight reduction rate before and after sonication of the electrode specimen indicating the value of the desorption amount of the electrode active material serving as the reference in the database.
According to claim 1,
An electrode active material detachment evaluation method that judges an electrode as a good product when the weight reduction rate before and after sonication is below the reference value.
According to claim 1,
The electrode active material detachment evaluation method further comprising: measuring a weight reduction rate before and after sonication of the electrode by varying the electrode manufacturing conditions, and predicting whether the electrode active material is defective from this.
10. The method of claim 9,
The manufacturing conditions of the said electrode, the electrode active material detachment evaluation method including the composition of an electrode active material layer, or the temperature of an electrode.
10. The method of claim 9,
The electrode active material detachment evaluation method further comprising deriving a reference value according to the electrode manufacturing conditions from the weight reduction rate before and after sonication of the electrode according to the electrode manufacturing conditions.
According to claim 1,
The electrode is a negative electrode active material desorption evaluation method.

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