Negative electrode for secondary battery, manufacturing method thereof, and secondary battery comprising the same

Abstract

To provide a negative electrode for a secondary battery that can prevent cracks and peeling of a negative electrode active material layer when a negative electrode is cut, a manufacturing method of the negative electrode, and a secondary battery comprising the negative electrode.SOLUTION: The invention provides a negative electrode for a secondary battery in which a negative electrode active material layer is formed on at least one surface of a current collector, where the negative electrode for a secondary battery satisfies the condition 2, namely, the breaking stress is 3.6 N or more, where the breaking stress is a value measured by pressing the negative electrode active material layer with a linear tip having a width of 2.5 mm and a sharp end at a speed of 10 μm / s.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] [Cross - Reference to Related Applications] This application claims the benefit of priority based on Korean Patent Application No. 10 - 2021 - 0112407 filed on Aug. 25, 2021, and all the contents disclosed in the literature of the Korean patent application are incorporated herein by reference in their entirety.

[0002] The present invention relates to a negative electrode for a secondary battery, a method for manufacturing the same, and a secondary battery including the same.

Background Art

[0003] Due to the technological development and increasing demand for mobile devices, the demand for secondary batteries as an energy source has been rapidly increasing. Among such secondary batteries, lithium secondary batteries, which exhibit high energy density, operating potential, long cycle life, and low self - discharge rate, have been commercialized and widely used.

[0004] In addition, recently, as the interest in environmental issues has grown, research on electric vehicles (EVs), hybrid electric vehicles (HEVs), etc., which replace gasoline vehicles, diesel vehicles, etc., that use fossil fuels and are one of the main causes of air pollution, has been actively conducted. As a power source for such electric vehicles (EVs), hybrid electric vehicles (HEVs), etc., lithium secondary batteries with high energy density, high discharge voltage, and output stability are mainly studied and used.

[0005] Such lithium secondary batteries are generally manufactured by laminating or winding positive and negative electrodes with a separator interposed therebetween, and incorporating this into a secondary battery case together with an electrolyte.

[0006] At this time, the negative electrode is manufactured by applying an active material slurry containing a negative electrode active material to a metal current collector, followed by drying, rolling, and cutting (cutting) with a unit electrode or the like. However, due to the physical properties of the negative electrode, there is a problem in that cracks and / or detachment of the negative electrode active material layer occur during the cutting.

[0007] However, such defects in the negative electrode will rapidly degrade the battery performance during the subsequent manufacture of the secondary battery and also pose a problem in terms of safety.

[0008] Therefore, it is a situation where there is a need to develop a technology that can solve this problem.

Summary of the Invention

Problems to be Solved by the Invention

[0009] An object of the present invention is to provide a negative electrode for a secondary battery that can prevent cracks and detachment of the negative electrode active material layer during negative electrode cutting during the manufacture of the negative electrode, a method for manufacturing the same, and a secondary battery including the same.

Means for Solving the Problems

[0010] A negative electrode for a secondary battery according to an embodiment of the present invention is a negative electrode for a secondary battery in which a negative electrode active material layer is formed on at least one surface of a current collector, wherein the negative electrode satisfies at least one of the following Condition 1 and Condition 2, [Condition 1] The continuous adhesive force in the thickness direction of the negative electrode for the secondary battery is 30 gf / 20 mm or more, [Condition 2] The breaking stress is 3.6 N or more, wherein the breaking stress is a value measured by pressing the negative electrode active material layer at a speed of 10 μm / s with a sharp one-sided flat tip having a width of 2.5 mm.

[0011] At this time, the continuous adhesive force of Condition 1 is the adhesive force between the active material layers per 10 μm in the thickness direction of the negative electrode.

[0012] Further, the negative electrode active material layer contains a negative electrode active material, a conductive material, and a binder. In order to satisfy the condition that the continuous adhesive strength in the thickness direction of the negative electrode is 30 gf / 20 mm or more, the content of the binder contained in each active material layer per 10 μm in the thickness direction of the negative electrode can be 2% by weight or more based on the total weight of each active material layer having a thickness of 10 μm.

[0013] Furthermore, when the negative electrode satisfies the condition 1, the porosity of the negative electrode can be 28% or less, and more specifically, it can be 5% to 28%.

[0014] More specifically, the negative electrode can satisfy all of the condition 1 and the condition 2.

[0015] On the other hand, according to another embodiment of the present invention, the porosity of the negative electrode is as follows. A method for manufacturing a negative electrode for a secondary battery, (a) applying a negative electrode active material slurry to at least one surface of a current collector; (b) drying the negative electrode active material slurry to form a negative electrode active material layer; and (c) rolling the negative electrode active material layer to manufacture a negative electrode for a secondary battery; including A method for manufacturing a negative electrode for a secondary battery is provided that satisfies at least one of the following condition 1, condition 3, and condition 4, and the incompatible deformation of the following condition 3 or condition 4 is represented by the following formula 1: [Condition 1] The continuous adhesive strength in the thickness direction of the negative electrode for the secondary battery is 30 gf / 20 mm or more. [Condition 3] The incompatible deformation (Misfit Strain) ε mf generated during drying in step (b) is 0.1% or less. [Condition 4] The incompatible deformation (Misfit Strain) ε mf generated during rolling in step (c) is 0.1% or less. [Formula 1]

[0016] [Number]

[0017] Here, the drying stress (σ) can be obtained by the following Equation 2. [Equation 2]

[0018]

Number

[0019] In the above Equation 2, t s is the thickness of the current collector, t c is the thickness of the dried negative electrode active material layer, Es is the elastic modulus of the current collector, L is the length of the current collector in the direction parallel to the protruding direction of the tab, ν s is the Poisson's ratio of the current collector, and D is the deflection of the current collector due to the drying.

[0020] The rolling stress (σ) can be the rolling load acting per unit area.

[0021] The electrode elastic modulus (E e ) of the negative electrode can be obtained by the following Equation 3. [Equation 3]

[0022]

Number

[0023] In the above Equation 3, E tot is the overall elastic modulus of the current collector and the dried or rolled negative electrode active material layer, E f is the elastic modulus of the current collector, T f is the thickness of the current collector, and T e is the thickness of the dried or rolled negative electrode active material layer.

[0024] According to still another embodiment of the present invention, the present invention also provides a secondary battery including a negative electrode for a secondary battery.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0026] The terms and words used in this specification and the claims should not be construed in a normal and dictionary sense. Instead, in accordance with the principle that the inventors can appropriately define the concept of the terms in order to explain the invention in the best way, they must be construed in a meaning and concept suitable for the technical idea of the present invention. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. Thus, at the time of this application, there can be various equivalents and modifications that can replace these, and the scope of the present invention is not limited to the embodiments described below.

[0027] According to one embodiment of the present invention, A negative electrode for a secondary battery in which a negative electrode active material layer is formed on at least one surface of a current collector, The negative electrode satisfies at least one of the following Condition 1 and Condition 2, [Condition 1] The continuous adhesion force in the thickness direction of the negative electrode for the secondary battery is 30 gf / 20 mm or more, [Condition 2] The breaking stress is 3.6 N or more. The breaking stress is a value measured by pressing the negative electrode active material layer at a speed of 10 μm / s with a sharp one-sided flat tip having a width of 2.5 mm. A negative electrode for a secondary battery is provided.

[0028] Specifically, the continuous adhesion force of the above-mentioned Condition 1 means the adhesion force between the active material layers per 10 μm in the thickness direction of the negative electrode. That is, when measuring the adhesion force between the active material layers per 10 μm, if the adhesion force is less than 30 gf / 20 mm in any section, it is regarded as not satisfying the above-mentioned Condition 1.

[0029] Such a continuous adhesion force is similar to the method of measuring the adhesion force of the manufactured negative electrode. Specifically, double-sided tape is attached to a slide glass, and a negative electrode punched out to 30 mm × 125 mm is placed thereon. Then, a Scotch Magic Tape (registered trademark) with a width of 20 mm is attached to the upper surface of the negative electrode. And, in order to uniformly adhere the negative electrode to the slide glass and the Scotch Magic Tape (registered trademark), it is passed through a laminator at room temperature, and then the Scotch Magic Tape (registered trademark) is pulled at 100 mm / min using a UTM (TA company) device to measure the force of peeling from the negative electrode. At this time, the measurement angle between the slide glass and the negative electrode is 90°. Then, after removing the peeled upper active material layer, the Scotch Magic Tape (registered trademark) is attached, and the force of peeling from the negative electrode is measured by pulling at 100 mm / min using a UTM (TA company) device. The measured value is obtained by continuously removing the peeled active material layer in such a manner and performing an adhesion force test.

[0030] If the adhesion force is less than 30 gf / 20 mm in any one of the measured values obtained in this way, it is determined that the above-mentioned Condition 1 is not satisfied.

[0031] That is, the inventors of the present application confirmed that when the above-mentioned Condition 1 is satisfied, cracks or detachment of the negative electrode active material layer do not occur during cutting of the negative electrode.

[0032] There are various methods to satisfy such Condition 1. Regardless of the method, when Condition 1 is satisfied, cracks or detachment of the negative electrode active material layer do not occur. However, as an example, in order to satisfy Condition 1, the negative electrode active material layer includes a negative electrode active material, a conductive material, and a binder, and the content of the binder contained in each active material layer per 10 μm in the thickness direction of the negative electrode can be 2% by weight or more based on the total weight of each active material layer having a thickness of 10 μm.

[0033] That is, the binder must be contained in the active material layer per 10 μm in thickness at 2% by weight or more, which has a similar meaning to the fact that the binder must be uniformly distributed at 2% by weight or more anywhere. When the binder is contained at 2% by weight or more in any section in this way, the continuous adhesive force can satisfy Condition 1.

[0034] Also, when the negative electrode satisfies Condition 1, the porosity of the negative electrode can be 28% or less, specifically 5% to 28% or less, and more specifically 10% to 25%.

[0035] The porosity is measured by magnifying the surface of the negative electrode 2,500 times using a field emission scanning electron microscope (FE-SEM) (Hitachi S-4800 Scanning Electron Microscope), and then the area ratio of the surface voids confirmed in an arbitrarily sampled range (horizontal 10 μm or more, vertical 15 μm or more) within the measured photograph to the total area is obtained and converted to volume to obtain it.

[0036] Outside the above range, when the porosity is excessively large, the adhesive force of the negative electrode may decrease, which is not preferable.

[0037] On the other hand, even when Condition 1 is not satisfied, according to the confirmation by the inventors of the present application, when the breaking stress of Condition 2 of the negative electrode is 3.6 N or more as described above, cracks or detachment of the negative electrode active material layer do not occur.

[0038] Specifically, the breaking stress can be 3.6 N or more and 5 N or less.

[0039] The breaking stress can be a value measured by pressing the negative electrode active material layer at a speed of 10 μm / s with a sharp-ended flat-tip chip having a width of 2.5 mm as described above. More specifically, it is a value measured by pressing vertically from above in the 90-degree direction of the negative electrode using a DHR (TA Instruments).

[0040] If the breaking stress satisfies the conditions according to the present invention, cracks or detachment of the negative electrode active material layer do not occur.

[0041] If the breaking stress is outside the scope of the present invention and is excessively small, cracks or detachment of the negative electrode active material layer may occur. If it is excessively large, the flexibility is excessively reduced, which is not preferable. Adjusting the breaking stress can be obtained by adjusting the incompatible deformation during drying and rolling at the manufacturing stage of the negative electrode, as described below.

[0042] Therefore, more specifically, the negative electrode can satisfy all of Condition 1 and Condition 2.

[0043] On the other hand, according to still another embodiment of the present invention, there is provided a method for manufacturing the negative electrode for a secondary battery, (a) applying a negative electrode active material slurry to at least one surface of a current collector; (b) drying the negative electrode active material slurry to form a negative electrode active material layer; and (c) rolling the negative electrode active material layer to manufacture a negative electrode for a secondary battery; including There is provided a method for manufacturing a negative electrode for a secondary battery that satisfies at least one of the following Condition 1, Condition 3, and Condition 4, and the incompatible deformation of Condition 3 or Condition 4 is represented by the following Formula 1. [Condition 1] The continuous adhesive force in the thickness direction of the negative electrode for the secondary battery is 30 gf / 20 mm or more, [Condition 3] The misfit strain generated during drying in step (b) is 0.1% or less, [Condition 4] The misfit strain generated during rolling in step (c) is 0.1% or less. [Formula 1]

[0044]

Number

[0045] As a result of the inventors' intensive research in this application, as described above, in order for the breaking stress of the negative electrode for a secondary battery to have the above value, it was confirmed that the misfit deformation generated during the manufacturing process satisfies at least one of the above Conditions 3 and 4.

[0046] Therefore, when manufacturing the negative electrode so as to satisfy the above Conditions 3 and 4, the effects according to this application can be achieved.

[0047] When the above conditions are satisfied, negative electrode cracks or detachment do not occur as the effects intended by the present invention.

[0048] The above Condition 1 is as described above.

[0049] The misfit deformation of the above Conditions 3 and 4 is obtained by the above Formula 1. At this time, the method for obtaining the above drying or rolling stress and the elastic modulus of the negative electrode is as described below.

[0050] Specifically, the above drying stress (σ) can be a value obtained by the following Formula 2. [Formula 2]

[0051]

Number

[0052] In the above Formula 2, t s is the thickness of the current collector, t c is the thickness of the dried negative electrode active material layer, E sis the elastic modulus of the current collector, L is the length of the current collector in the direction parallel to the protruding direction of the tab, ν s is the Poisson's ratio of the current collector, and D is the degree of deformation of the current collector due to the drying.

[0053] Here, the thickness of the current collector, the negative electrode active material layer, and the length of the current collector can be determined by the naked eye. The elastic modulus and Poisson's ratio of the current collector mean the values of the metal forming the current collector, which are determined values. For example, the elastic modulus of Al is 7.19×10 2 and the Poisson's ratio can be 0.34. The elastic modulus of Cu is 1.25×10 3 and the Poisson's ratio can be 0.34. Also, the degree of deformation of the current collector can be measured by using a laser and a position sensor to measure the degree of bending of the negative electrode. The degree of bending is the value measured by the height of the Z-axis when the negative electrode warped downward or upward when viewed from the side, with the negative electrode dried on a flat holder.

[0054] Also, the rolling stress (σ), different from the drying stress, means the rolling load acting per unit area.

[0055] The rolling load is the rolling applied to the negative electrode during rolling and can be selected by the operator.

[0056] Also, the negative electrode elastic modulus (E e ) can be a value obtained by the following formula 3. [Formula 3]

[0057]

Number

[0058] In the formula 3, E tot is the overall elastic modulus of the current collector and the negative electrode active material layer after drying or after rolling, E f is the elastic modulus of the current collector, T f is the thickness of the current collector, and Te is the thickness of the negative electrode active material layer after drying or the thickness of the negative electrode active material layer after rolling.

[0059] The above E f The elastic modulus of the current collector, the thickness of the current collector, and the thickness of the negative electrode active material layer are as described above. E tot The overall elastic modulus of is the value measured using a DMA device (viscoelastic measurement device).

[0060] When the drying or rolling stress and the negative electrode elastic modulus obtained in this way are substituted into the above formula (1) and the condition that any one of the mismatch deformations is 0.1% or less is satisfied, the breaking stress of the negative electrode becomes 3.6 N or more, and the effects intended by the present invention can be exhibited.

[0061] Therefore, it is possible to determine whether the conditions of the present invention are satisfied from the manufacturing stage, quickly detect defects, and prevent cracks and / or detachment of the negative electrode active material layer, thereby preventing deterioration of the performance and safety of the secondary battery including the same.

[0062] On the other hand, according to still another embodiment of the present invention, the present invention also provides a secondary battery including the negative electrode for a secondary battery.

[0063] Since other manufacturing methods and components of the secondary battery are known in the art, descriptions thereof are omitted in this specification and are included in the scope of the present invention.

[0064] Hereinafter, the present invention will be described in detail based on preferred embodiments of the present invention with reference to Examples, Comparative Examples, and the accompanying drawings.

[0065] <Comparative Example 1> (When the negative electrode continuous adhesion force is 30 gf or less and the drying / rolling mismatch strain is 0.1% or more) Using artificial graphite as the active material, a slurry for the active material layer was prepared by mixing a binder (SBR and CMC mixed at a weight ratio of 2:1), carbon black as a conductive material at a weight ratio of 96:2.5:1.5, and water as a dispersion medium at a weight ratio of 1:2 for the mixture and the dispersion medium.

[0066] Using a slot die, the slurry for the active material layer was coated on one side of a copper (Cu) thin film, which is a negative electrode current collector with a thickness of 10 μm, and dried under vacuum at 130 °C for 1 hour to form an active material layer. The thus formed active material layer was rolled by a roll pressing method to produce a negative electrode having an active material layer with a thickness of 80 μm.

[0067] The porosity of the manufactured negative electrode was 30%. The porosity was measured by magnifying the surface of the negative electrode 2,500 times using a field emission scanning electron microscope (FE-SEM) (Hitachi S-4800 Scanning Electron Microscope), and then the area ratio of the surface voids confirmed in an arbitrarily sampled range (horizontal 10 μm or more, vertical 15 μm or more) in the measured photograph was obtained with respect to the total area and converted to volume.

[0068] <Example 1> (When the continuous adhesion force of the negative electrode is 30 gf or more and the dry / rolling misfit strain is 0.1% or more) In Comparative Example 1, a negative electrode was manufactured in the same manner as in Comparative Example 1, except that the weight ratio of the active material:binder:conductive material was mixed at 96:2.8:1.2 and rolled so that the active material layer had a thickness of 75 μm during rolling. The porosity of the manufactured negative electrode was 25%.

[0069] <Example 2> (When the continuous adhesion force of the negative electrode is 30 gf or less, the dry misfit strain is 0.1% or less, and the rolling misfit strain is 0.1% or more) In Comparative Example 1, except that the slurry for the active material layer was dried under vacuum at 100°C for 30 minutes, then dried under vacuum at 110°C for 30 minutes, and again dried under vacuum at 130°C for 30 minutes to form the active material layer, the negative electrode was manufactured in the same manner as in Comparative Example 1. The porosity of the manufactured negative electrode was 30%.

[0070] <Example 3> (When the continuous adhesion force of the negative electrode is 30 gf or less, the drying misfit strain is 0.1% or more / the rolling misfit strain is 0.1% or less) In Comparative Example 1, except that the active material layer during rolling was first rolled to a thickness of 90 μm and then secondarily rolled to a thickness of 80 μm, the negative electrode was manufactured in the same manner as in Comparative Example 1. The porosity of the manufactured negative electrode was 30%.

[0071] <Experimental Example 1> The continuous adhesion forces of the negative electrodes manufactured in Comparative Example 1 and Examples 1 to 3 were measured and are shown in FIGS. 1 to 4 below.

[0072] For the continuous adhesion force of the negative electrode, double-sided tape was attached to a slide glass, and the negative electrode punched out to 30 mm × 125 mm was placed thereon. Then, a Scotch Magic Tape (registered trademark) with a width of 20 mm was attached to the upper surface of the negative electrode. And, in order to uniformly adhere the negative electrode to the slide glass and the negative electrode to the Scotch Magic Tape (registered trademark), it was passed through a laminator (Supernex-synC325, 9 speed levels) at room temperature, and then the Scotch Magic Tape (registered trademark) was pulled at 100 mm / min using a UTM (TA company) device to measure the force of peeling from the negative electrode. At this time, the measurement angle between the slide glass and the negative electrode is 90°. Then, after removing the peeled upper active material layer, the Scotch Magic Tape (registered trademark) was attached, and the force of peeling from the negative electrode was measured by pulling at 100 mm / min using a UTM (TA company) device. The measured value obtained by continuously removing the peeled active material layer in such a manner and performing the adhesion test is meant.

[0073] When considering FIGS. 1 to 4 below, it can be confirmed that the continuous adhesion force of the negative electrode in Comparative Example 1 and Examples 2 and 3 is 30 gf / 20 mm or less in some intervals, while the continuous adhesion force of the negative electrode in Example 1 is 30 gf / 20 mm or more in all intervals.

[0074] <Experimental Example 2> The misfit strain in the drying and rolling processes of the negative electrodes manufactured in Comparative Example 1 and Examples 1 to 3 was calculated and shown in Table 1 below.

[0075]

Table 1

[0076] Referring to Table 1 above, it can be confirmed that in Comparative Example 1 and Example 1, the misfit strain in drying and rolling is both 0.1% or more, while in Examples 2 and 3, at least one of them is 0.1% or less.

[0077] The stress and elastic modulus are obtained by the above formula 2, rolling load and formula 3, and the misfit strain is obtained from formula 1 based on the above values.

[0078] <Experimental Example 3> The breaking stress of the negative electrodes manufactured in Comparative Example 1 and Examples 1 to 3 was measured and shown in Table 2 below.

[0079] The breaking stress is a value measured by using a DHR (TA Co., Ltd.) instrument with a sharp one-sided flat tip having a width of 2.5 mm to press the negative electrode active material layer vertically from above at a speed of 10 μm / s in the 90-degree direction.

[0080]

Table 2

[0081] When considering Table 2 above and comparing it with Experimental Example 2, it can be confirmed that when at least one of the Misfit strains in the drying process or the rolling process is 0.1% or less, the breaking stress becomes 3.6 N or more.

[0082] <Experimental Example 4> The negative electrodes manufactured in Comparative Example 1 and Examples 1 to 3 were notched in half to examine the presence or absence of cracks.

[0083] The presence or absence of cracks was confirmed visually by taking a microscopic photograph of the upper part of the negative electrode in the vertical direction, and the results are shown in FIGS. 5 to 8 below.

[0084] When examining FIGS. 5 to 8, it can be confirmed that cracks occurred only in Comparative Example 1 that did not satisfy all of Condition 1 and Condition 2, or Condition 1, Condition 3, and Condition 4.

[0085] Therefore, it can be seen that when any one of Conditions 1 to 4 of the present invention is satisfied, the effects intended by the present invention can be obtained.

[0086] Those having ordinary knowledge in the field to which the present invention pertains can make various applications and modifications within the scope of the present invention based on the above content.

Industrial Applicability

[0087] Since the negative electrode for a secondary battery according to the present invention satisfies specific conditions, problems such as cracks and detachment of the negative electrode active material layer do not occur during negative electrode cutting. Therefore, there is an effect of solving problems such as performance degradation or safety degradation of a secondary battery including such a negative electrode.

Claims

1. A negative electrode for a secondary battery, comprising a negative electrode active material layer formed on at least one surface of a current collector, The negative electrode for a secondary battery satisfies at least one of the following conditions 1 and 2: [Condition 1] The continuous adhesive strength in the thickness direction of the negative electrode for secondary batteries is 30 gf / 20 mm or more; [Condition 2] The breaking stress is 3.6 N or more. The breaking stress is a value measured by pressing the negative electrode active material layer at a speed of 10 μm / s with a sharp end-shaped tip having a width of 2.5 mm.

2. 2. The negative electrode for a secondary battery according to claim 1, wherein the continuous adhesive strength in condition 1 is an adhesive strength between active material layers per 10 μm in a thickness direction of the negative electrode for a secondary battery.

3. the negative electrode active material layer includes a negative electrode active material, a conductive material, and a binder, 2. The negative electrode for a secondary battery according to claim 1, wherein when the negative electrode for a secondary battery satisfies condition 1, a content of the binder contained in each active material layer per 10 μm in a thickness direction of the negative electrode for a secondary battery is 2 wt % or more based on a total weight of each active material layer having a thickness of 10 μm.

4. 2. The negative electrode for a secondary battery according to claim 1, wherein when said negative electrode for a secondary battery satisfies said condition 1, said negative electrode for a secondary battery has a porosity of 28% or less.

5. 5. The negative electrode for a secondary battery according to claim 4, wherein when the negative electrode for a secondary battery satisfies the condition 1, the porosity of the negative electrode for a secondary battery is 5% to 28%.

6. 2. The negative electrode for a secondary battery according to claim 1, wherein the negative electrode for a secondary battery satisfies both of the condition 1 and the condition 2.

7. A method for producing the negative electrode for a secondary battery according to claim 1, comprising the steps of: (a) applying a negative electrode active material slurry to at least one surface of a current collector; (b) drying the negative electrode active material slurry to form a negative electrode active material layer; and (c) rolling the negative electrode active material layer to produce a negative electrode for a secondary battery; Including, At least one of the following conditions 1, 3, and 4 is satisfied, and the non-compliant deformation of the following condition 3 or 4 is expressed by the following formula 1: [Condition 1] The continuous adhesive strength in the thickness direction of the negative electrode for secondary batteries is 30 gf / 20 mm or more; [Condition 3] The non-conforming deformation (ε ｍｆ ) is 0.1% or less; [Condition 4] The non-conforming deformation (ε ｍｆ ) is 0.1% or less; [Formula 1] [0010] The method for producing a negative electrode for a secondary battery is as follows.

8. The drying stress (σ) is calculated by the following formula 2: [Formula 2] [0025] In the above formula 2, t ｓ is the thickness of the current collector, t ｃ is the thickness of the dried negative electrode active material layer, E ｓ is the elastic modulus of the current collector, L is the length of the current collector in a direction parallel to the protruding direction of the tab, v ｓ 8. The method for producing a negative electrode for a secondary battery according to claim 7, wherein: is the Poisson's ratio of the current collector; and D is the degree of deformation of the current collector due to drying.

9. The method for producing a negative electrode for a secondary battery according to claim 7 , wherein the rolling stress (σ) is a rolling load acting per unit area.

10. Electrode elastic modulus (E ｅ ) is calculated by the following formula 3: [Formula 3] [0030] In the above formula 3, E ｔｏｔ is the overall elastic modulus of the current collector and the negative electrode active material layer after drying or the negative electrode active material layer after rolling, E ｆ is the elastic modulus of the current collector, T ｆ is the thickness of the current collector, and T ｅ is a thickness of the negative electrode active material layer after drying or after rolling, the method for producing a negative electrode for a secondary battery according to claim 7 .

11. A secondary battery comprising the negative electrode for secondary batteries according to claim 1 .

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