JP2016085876A - Method for manufacturing negative electrode for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a low-resistance negative electrode for a nonaqueous electrolyte secondary battery.SOLUTION: A method for manufacturing a negative electrode for a nonaqueous electrolyte secondary battery comprises the steps of: preparing first moist powder by mixing a negative electrode active material, CMC and an imide-based resin without solvent into a powder mixture and then, adding water to the powder mixture; preparing second moist powder by coating at least part of the surface of first moist powder with SBR; and transferring the second moist powder to a negative electrode current collector.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing a negative electrode for a nonaqueous electrolyte secondary battery.

  In Patent Document 1 (Japanese Patent Laid-Open No. 2013-235684), active material particles and a granulating binder are kneaded to prepare a slurry, and the slurry is granulated by a spray drying method or the like. Making a body is described.

JP 2013-235684 A

  The imide-based resin forms a strong polymer matrix and has excellent heat resistance (heat resistance temperature of 400 ° C. or higher) and excellent mechanical properties. Therefore, it has been proposed to use an imide resin as a binder for a negative electrode of a nonaqueous electrolyte secondary battery. For example, when a negative electrode active material made of an alloy material is used, it is preferable to use an imide resin as a negative electrode binder.

  However, when a negative electrode is produced according to the method described in Patent Document 1 when an imide resin is used as a binder, the imide resin is dissolved in an organic solvent (for example, NMP (N-methylpyrrolidone)) during the production of the slurry. Sometimes. When the obtained melt covers the surface of the negative electrode active material, the resistance of the negative electrode may be increased. The present invention provides a method for producing a negative electrode for a non-aqueous electrolyte secondary battery with low resistance.

  As a method for producing a negative electrode for a non-aqueous electrolyte secondary battery, the present inventors produced wet granulated particles (moist powder) using a negative electrode active material, a binder, and a small amount of a solvent, and the wet granulation thereof. A method of transferring particles to a negative electrode current collector has been proposed. In this method, water can be used as a solvent. Therefore, when an imide resin is used as the binder, the binder can be prevented from dissolving in the solvent (water). Therefore, the present inventors thought that a negative electrode having a low resistance could be manufactured by manufacturing a negative electrode using the above method.

  However, when the negative electrode is produced using the above method, the adhesion between the negative electrode current collector and the granulated particles (granulated material produced by removing the solvent from the wet granulated particles) decreases, The adhesion between the granulated particles was lowered. Therefore, it was found that even when a negative electrode was manufactured using the above method, a low resistance negative electrode could not be manufactured. Based on such consideration, the manufacturing method of the negative electrode for a non-aqueous electrolyte secondary battery of the present invention was completed.

  In the method for producing a negative electrode for a non-aqueous electrolyte secondary battery according to the present invention, a negative electrode active material, carboxymethyl cellulose (CMC) and an imide resin are mixed with powder, and then water is added to the first wet structure. A step of producing granular particles, a step of producing second wet granulated particles by covering at least part of the surface of the first wet granulated particles with styrene-butadiene rubber (SBR), And 2 transferring the wet granulated particles to the negative electrode current collector.

  In the present invention, since dissolution of the imide resin during the production of the first wet granulated particles can be prevented, it is possible to prevent the dissolved imide resin from covering the surface of the negative electrode active material. In addition, since the second wet granulated particles with SBR provided on the surface are transferred to the negative electrode current collector, the negative electrode granulated particles (prepared by removing the solvent (water) from the second wet granulated particles The agglomerated particles) are brought into close contact with the negative electrode current collector or other negative electrode granulated particles by SBR.

  The “imide resin” means a synthetic resin having a polymer skeleton mainly composed of imide bonds, and may further include a bond (for example, an amide bond) different from the imide bond. Examples of the imide resin include polyimide resin and polyamideimide resin.

  “Powder mixing negative electrode active material, CMC and imide resin” means mixing solid negative electrode active material, solid state CMC and solid state imide resin without using any solvent. means. Examples of the solid-state negative electrode active material include a powdered negative electrode active material. The same applies to CMC in the solid state and imide resin in the solid state.

  In the “first wet granulated particles”, particles (for example, any of negative electrode active material, CMC, or imide resin) and particles (for example, any of negative electrode active material, CMC, or imide resin) and It is considered that the particles are adhered to each other by the surface tension of the solvent (water in the present invention) existing between the particles to form a granulated body. The “first wet granulated particle” preferably contains 65% by mass or more of solid content (negative electrode active material, CMC, and imide resin).

  “Coating at least a part of the surface of the first wet granulated particles with SBR” includes a case where particles made of SBR are attached to the surface of the first wet granulated particles.

  “Transfer” means that the second wet granulated particles are pressed onto the surface of the negative electrode current collector and then dried.

  In the present invention, it is possible to prevent the dissolved imide-based resin from covering the surface of the negative electrode active material, and to improve the adhesion between the negative electrode current collector and the negative electrode granulated particles and the adhesion between the negative electrode granulated particles. be able to. Thereby, the low resistance non-aqueous electrolyte secondary battery negative electrode can be manufactured.

It is sectional drawing which shows typically the 1st wet granulation particle | grain of one Embodiment of this invention. It is sectional drawing which shows typically the 2nd wet granulation particle | grains of one Embodiment of this invention. It is sectional drawing which shows the negative electrode of one Embodiment of this invention typically.

  The present invention will be described below with reference to the drawings. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

[Method for producing negative electrode for nonaqueous electrolyte secondary battery]
FIG. 1 is a cross-sectional view schematically showing first wet granulated particles according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing the second wet granulated particles of the present embodiment. FIG. 3 is a cross-sectional view schematically showing the negative electrode of the present embodiment.

  In the method for producing a negative electrode for a non-aqueous electrolyte secondary battery (hereinafter simply referred to as “negative electrode”) of the present embodiment, first, the negative electrode active material 11, CMC (not shown), and the imide resin 13 are powder-mixed. Then, add more water and mix. In this way, the first wet granulated particles 10 are produced. Next, at least a part of the surface of the first wet granulated particle 10 is coated with SBR 21. In this way, the second wet granulated particle 20 is produced. Subsequently, the second wet granulated particles 20 are transferred to the negative electrode current collector 31. In this way, the negative electrode 30 is manufactured. The form of the first wet granulated particle 10 is not limited to the form shown in FIG. 1, and the form of the second wet granulated particle 20 is not limited to the form shown in FIG.

  In the present embodiment, water is used as a solvent when the first wet granulated particles 10 are produced. Thereby, since it can prevent that the imide resin 13 melt | dissolves in a solvent, it can prevent that the melt | dissolution of the imide resin 13 coat | covers the surface of the negative electrode active material 11 (FIG. 1). Therefore, insertion and desorption of lithium ions from the negative electrode active material 11 can be performed smoothly.

  In addition, since the second wet granulated particles 20 are transferred to the negative electrode current collector 31, the second wet granulated particles 20 are in close contact with the negative electrode current collector 31 or other second wet granulated particles 20 by the SBR 21. . Therefore, if the solvent is removed from the second wet granulated particles 20, the negative electrode granulated particles are brought into close contact with the negative electrode current collector 31 or other negative electrode granulated particles by the SBR 21 (FIG. 3). Thereby, the contact resistance between the negative electrode granulated particles and the negative electrode current collector 31 can be kept low, and the contact resistance between the negative electrode granulated particles can be kept low.

  In summary, the manufactured negative electrode 30 can smoothly insert and desorb lithium ions from the negative electrode active material 11, and negative electrode granulated particles (particularly, the negative electrode active particles contained in the negative electrode granulated particles). The contact resistance between the substance 11) and the negative electrode current collector 31 and the contact resistance between the negative electrode granulated particles (particularly, the negative electrode active materials 11 included in the negative electrode granulated particles) can be kept low. Thereby, in this embodiment, the low resistance negative electrode 30 can be manufactured. Therefore, the manufacturing method of the negative electrode 30 of this embodiment is applied to a non-aqueous electrolyte secondary battery (for example, a non-aqueous electrolyte secondary battery included in a vehicle power supply, a factory power supply, a household power supply, or the like) that requires a high capacity. It is suitable for the manufacturing method of the negative electrode contained.

  Moreover, since imide resin is used as a binder, the thermal stability of the manufactured negative electrode 30 can be improved. For example, the negative electrode granulated particles and the negative electrode current collector 31 can be brought into close contact with each other even at high temperatures, and the negative electrode granulated particles can be brought into close contact with each other. Thereby, the nonaqueous electrolyte secondary battery excellent in thermal stability can be provided.

  When the first wet granulated particles 10 are produced using SBR 21 instead of the imide resin 13 and the second wet granulated particles 20 are produced using the imide resin 13 instead of the SBR 21, the second wet granulated particles 20 are produced. It is difficult to sufficiently improve the adhesion between the particle particles 20. Therefore, it becomes difficult to manufacture the low resistance negative electrode 30.

  In addition, SBR 21 is more likely to adhere to the surface of negative electrode active material 11 than imide resin 13. Therefore, when the negative electrode active material 11, the imide resin 13 and the SBR 21 are mixed at the same time, the effect obtained by using the imide resin 13 (adhesive adhesion between the negative granulated particles and the negative electrode current collector 31 even at high temperatures) In addition, it is difficult to obtain negative electrode granulated particles that can be adhered to each other. Below, it shows in order for every process.

<Preparation of first wet granulated particles>
The specific method of powder-mixing the negative electrode active material 11, CMC, and the imide resin 13 is not particularly limited, and it is preferable to powder-mix these using a conventionally known kneading apparatus. The same can be said for the method of mixing the negative electrode active material 11, the CMC and the imide resin 13 with water.

  The negative electrode active material 11 is preferably made of a conventionally known material as a negative electrode active material of a non-aqueous electrolyte secondary battery, but more preferably an alloy-based material such as a silicon-based alloy material, a tin-based alloy material, or a titanium-based alloy material Consists of.

  The compounding quantity of the negative electrode active material 11, the compounding quantity of CMC, and the compounding quantity of the imide resin 13 are not specifically limited. For example, the blending amount of CMC is preferably 0.1% by mass or more and 5% by mass or less with respect to the blending amount of the negative electrode active material 11, and the blending amount of the imide resin 13 is based on the blending amount of the negative electrode active material 11. It is preferable that it is 0.1 mass% or more and 5 mass% or less.

<Preparation of second wet granulated particles>
The second wet granulated particles 20 can be produced according to the following method. An aqueous dispersion of SBR (a structure in which SBR21 is dispersed in water) is added to the first wet granulated particles 10, and these are mixed. As a mixing method, a method similar to the method of mixing the negative electrode active material 11, CMC, and the imide resin 13 can be applied. By this mixing, at least a part of the surface of the first wet granulated particle 10 is coated with the SBR 21, and thus the second wet granulated particle 20 is obtained. The amount of SBR 21 added is not particularly limited, but is preferably 0.1% by mass or more and 1% by mass or less with respect to the compounding amount of the negative electrode active material 11 and is not more than the compounding amount of the imide resin 13.

<Transfer>
The second wet granulated particles 20 can be pressure-bonded to the surface of the negative electrode current collector 31 using a conventionally known molding transfer device. The conditions for drying the second wet granulated particles 20 pressure-bonded to the surface of the negative electrode current collector 31 are not particularly limited, and drying is performed so that the solvent (water) contained in the second wet granulated particles 20 is removed. It is preferable to set conditions.

[Negative electrode]
The negative electrode 30 of this embodiment is obtained according to the manufacturing method of the negative electrode 30 of this embodiment. Therefore, in the negative electrode 30, the negative electrode granulated particles are in close contact with the negative electrode current collector 31 by the SBR 21, and the negative electrode granulated particles are in the negative electrode mixture layer 33 provided on the surface of the negative electrode current collector 31. The SBR 21 is in close contact with each other. In addition, the negative electrode granulated particles are produced by removing the solvent (water) from the second wet granulated particles 20. Therefore, in the negative-granulated particles, SBR 21 exists outside the granulated body containing the negative electrode active material 11, CMC, and the imide resin 13.

  Since the negative electrode 30 is obtained according to the manufacturing method of the negative electrode 30 of the present embodiment, it is possible to prevent the binder (for example, imide resin) from migrating (segregating) due to the removal of the solvent. Specifically, when the negative electrode mixture layer 33 is divided into two equal parts in the thickness direction, the nitrogen element in the negative electrode mixture layer 33 (surface layer side negative electrode mixture layer) located on the side opposite to the negative electrode current collector 31 Of the nitrogen element in the negative electrode mixture layer 33 (current collector side negative electrode mixture layer) located on the negative electrode current collector 31 side can be suppressed to 0.7 or more and 1.3 or less.

  Moreover, since the negative electrode 30 was obtained according to the manufacturing method of the negative electrode 30 of this embodiment, the content of NMP in the negative electrode mixture layer 33 can be suppressed to 1 ppm or less.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to the following.
[Example 1]
<Manufacture of lithium ion secondary batteries>
(Preparation of negative electrode)
Graphite was prepared as a negative electrode active material. Into a planetary mixer, 1 part by mass of CMC and 1 part by mass of polyimide resin (powder) were added to 100 parts by mass of the negative electrode active material and mixed, and then 43 parts by mass of water was added and further mixed. In this way, first wet granulated particles (solid content concentration: 70% by mass) were obtained.

  An aqueous dispersion of SBR was added to the planetary mixer containing the first wet granulated particles (0.5 parts by mass of SBR solid content with respect to 100 parts by mass of the negative electrode active material), and further mixed. In this way, second wet granulated particles were obtained.

  The second wet granulated particles were pressure-bonded to one surface of the Cu foil (negative electrode current collector) using a molding transfer device and then dried. Thereafter, according to the same method, the second wet granulated particles were pressed against the other surface of the Cu foil and then dried. At this time, the second wet granulated particles are formed on each of the negative electrode current collectors so that a portion where the Cu foil is exposed from the second wet granulated particles (negative electrode exposed portion) is formed at one end in the width direction of the negative electrode current collector. Crimped to the surface. The obtained electrode was rolled to a predetermined thickness and then cut into a predetermined size. In this way, a negative electrode was obtained.

(Preparation of positive electrode)
A composite oxide containing Li and three transition metal elements (Ni, Co, and Mn) was prepared as a positive electrode active material. The positive electrode active material, acetylene black (conductive agent) and PVdF (PolyVinylidene DiFluoride, binder) were mixed and diluted with NMP so that the mass ratio was 90: 8: 2. In this way, a positive electrode mixture paste was obtained.

  The positive electrode mixture paste was applied to both surfaces of the Al foil so that one end in the width direction of the Al foil (positive electrode current collector) was exposed, and then dried. The obtained electrode plate was rolled to obtain a positive electrode.

(Production and insertion of electrode body)
A separator made of PE (polyethylene) was prepared. A portion where the Al foil is exposed from the positive electrode mixture layer (positive electrode exposed portion) and a portion where the Cu foil is exposed from the negative electrode mixture layer (negative electrode exposed portion) protrude from the separator in opposite directions in the width direction of the Al foil. In addition, a positive electrode, a negative electrode, and a separator were disposed. Then, the winding axis | shaft was arrange | positioned so that it might become parallel with respect to the width direction of Al foil, and the positive electrode, the separator, and the negative electrode were wound using the winding axis | shaft. The electrode bodies (cylindrical electrode bodies) thus obtained were given pressures in opposite directions to obtain a flat electrode body.

  A battery case having a case body and a lid was prepared. The positive electrode exposed part and the positive electrode terminal provided in the cover body were connected using the positive electrode current collector plate. The negative electrode exposed part and the negative electrode terminal provided in the cover body were connected using the negative electrode current collecting plate. In this way, the lid body was connected to the flat electrode body. Then, the flat electrode body was put in the recess of the case body, and the opening of the case body was closed with a lid.

(Preparation and injection of non-aqueous electrolyte)
EC (ethylene carbonate), DMC (ethyl methyl carbonate), and EMC (dimethyl carbonate) were mixed so that the volume ratio was 3: 4: 3. LiPF ₆ was added to the mixed solvent thus obtained to obtain a nonaqueous electrolytic solution. In the obtained nonaqueous electrolytic solution, the concentration of LiPF ₆ was 1.0 mol / L.

  The obtained non-aqueous electrolyte was poured into the recess of the case body from the injection hole formed in the lid. After reducing the pressure inside the battery case, the injection hole was sealed. Thus, the lithium ion secondary battery of this example (battery capacity is 4 Ah) was obtained.

<Initial charge / discharge>
The obtained lithium ion secondary battery was charged with a current of 4 A until the battery voltage reached 4.1 V, and then discharged with a current of 4 A until the battery voltage reached 3.0 V.

<Evaluation>
(Measurement of migration of polyimide resin)
The lithium ion secondary battery that had been initially charged and discharged was disassembled and the negative electrode was taken out. Nitrogen mapping is performed on the cross section of the negative electrode mixture layer at an arbitrary position of the negative electrode, and the integrated value of the nitrogen atom strength in the surface side negative electrode mixture layer and the integrated value of the nitrogen atom strength in the current collector side negative electrode mixture layer And asked. The migration index was calculated using the following formula 1. The results are shown in Table 1. When the migration index shows a value close to 1, it can be said that the migration of the binder is suppressed in the negative electrode mixture layer during drying.
(Migration index) = (Integrated value of the strength of nitrogen atoms in the negative electrode mixture layer on the surface layer side) ÷ (Integrated value of the strength of nitrogen atoms in the negative electrode mixture layer on the current collector side) Formula 1.

(Measurement of battery resistance)
The lithium ion secondary battery that had been initially charged and discharged was charged at 25 ° C. until the battery voltage reached 3.7 V, and then discharged at a current of 100 A for 10 seconds. The battery resistance was determined by dividing the amount of voltage drop due to this discharge by the discharge current (100 A). The results are shown in Table 1.

(Measurement of change rate of peel strength)
The lithium ion secondary battery that had been initially charged and discharged was disassembled and the negative electrode was taken out. A tape was applied to the surface of the negative electrode mixture layer, and a 90-degree peel test was performed in accordance with JIS Z0237: 2009 (adhesive tape / adhesive sheet test method). In this way, the peel strength before heating was determined.

The negative electrode was heated at 400 ° C. for 10 minutes. Then, the peel strength after heating was calculated | required according to the above-mentioned method, and the rate of change of peel strength was computed using following formula 2. The results are shown in Table 1. It can be said that the negative electrode has better heat resistance when the rate of change in peel strength is close to 1.
(Change rate of peeling strength) = (peeling strength after heating) ÷ (peeling strength before heating) Equation 2.

  In Table 1, “polyimide” means a polyimide resin, and “polyamideimide” means a polyamideimide resin.

  In Table 1, the compounding amount (mass) of the imide resin with respect to the compounding amount (mass) of the negative electrode active material is described in the compounding amount of the imide resin. Similarly, the SBR content is the ratio of the SBR content (mass) to the negative electrode active material content (mass).

  In Comparative Example 5, a negative electrode was prepared using a negative electrode mixture paste (described later). Therefore, in Table 1, the binder of the first wet granulated particles and the binder of the second wet granulated particles of Comparative Example 5 are blank.

[Examples 2-6 and Comparative Examples 1-3]
As shown in Table 1, the first wet granulated particles were prepared by changing the amount of imide resin, and the second wet granulated particles were changed by changing the amount of SBR as shown in Table 1. A lithium ion secondary battery was produced according to the method described in Example 1 except for. Evaluation similar to Example 1 was performed with respect to the obtained lithium ion secondary battery. The results are shown in Table 1.

[Comparative Examples 4 to 7]
A lithium ion secondary battery was produced according to the method described in Example 1 except that the negative electrode was produced according to the following method. Evaluation similar to Example 1 was performed with respect to the obtained lithium ion secondary battery. The results are shown in Table 1.

(Comparative Example 4)
In a planetary mixer, 1 part by mass of a polyimide resin (powder) and 43 parts by mass of NMP were added to and mixed with 100 parts by mass of the negative electrode active material. In this way, first wet granulated particles were obtained.

  According to the method described in Example 1, the first wet granulated particles were pressed against one surface of the Cu foil and then dried. According to the same method, the first wet granulated particles were pressed onto the other surface of the Cu foil and then dried. Thereafter, a negative electrode was produced according to the method described in Example 1.

(Comparative Example 5)
In a planetary mixer, 1 part by mass of CMC, 1 part by mass of polyimide resin (powder) and 100 parts by mass of SBR with respect to 100 parts by mass of the negative electrode active material (0.5 parts by mass of SBR solid content with respect to 100 parts by mass of the negative electrode active material) ) And 87 parts by mass of water were mixed. In this way, a negative electrode mixture paste was obtained.

  The negative electrode mixture paste was applied to both sides of the Cu foil so that one end in the width direction of the Cu foil was exposed, and then dried. The obtained electrode plate was rolled to obtain a negative electrode.

(Comparative Example 6)
In a planetary mixer, 1 part by weight of CMC and an aqueous dispersion of SBR (0.5 parts by weight in SBR solids with respect to 100 parts by weight of the negative electrode active material) were mixed with 100 parts by weight of the negative electrode active material, and then mixed. 43 parts by weight of water was added and further mixed. In this way, first wet granulated particles were obtained.

  Next, 1 part by mass of polyimide resin (powder) was added to the planetary mixer containing the first wet granulated particles, and further mixed. In this way, second wet granulated particles were obtained.

  According to the method described in Example 1, the second wet granulated particles were pressed onto one surface of the Cu foil and then dried. According to the same method, the second wet granulated particles were pressed onto the other surface of the Cu foil and then dried. Thereafter, a negative electrode was produced according to the method described in Example 1.

(Comparative Example 7)
In a planetary mixer, 1 part by mass of CMC, 1 part by mass of polyimide resin (powder) and 100 parts by mass of SBR with respect to 100 parts by mass of the negative electrode active material (0.5 parts by mass of SBR solid content with respect to 100 parts by mass of the negative electrode active material) And 43 parts by weight of water were added and further mixed. In this way, first wet granulated particles were obtained.

  According to the method described in Example 1, the first wet granulated particles were pressed against one surface of the Cu foil and then dried. According to the same method, the first wet granulated particles were pressed onto the other surface of the Cu foil and then dried. Thereafter, a negative electrode was produced according to the method described in Example 1.

<Discussion>
From Examples 1 to 5 and Comparative Example 1, it was found that the battery resistance increased as the amount of the binder (polyimide resin or SBR) increased. The binder may inhibit the battery reaction of the lithium ion secondary battery, and may block pores formed in the negative electrode mixture layer. In Comparative Example 1, it was considered that the pores formed in the negative electrode mixture layer were blocked by the binder, so that the porosity of the negative electrode mixture layer was lowered, and thus the resistance was increased during discharging at a large current. It is done.

  In Comparative Examples 2 and 3, the rate of change in peel strength (= (peel strength after heating) ÷ (peel strength before heating)) was significantly lower than 1. In Comparative Examples 2 and 3, since the blending amount of SBR is larger than the blending amount of the polyimide resin, the adhesion between the negative electrode granulated particles and the Cu foil is reduced at 400 ° C. It is thought that it fell.

  In Comparative Example 4, the battery resistance was high. In Comparative Example 4, since the first wet granulated particles were produced using NMP, the polyimide resin was dissolved in NMP when the first wet granulated particles were produced. It is considered that the battery resistance was increased because the dissolved material covered the surface of the negative electrode active material.

  In Comparative Example 5, the battery resistance was high. In Comparative Example 5, since the negative electrode mixture paste was applied to the negative electrode current collector to prepare the negative electrode, migration of the binder occurred in the negative electrode mixture layer during drying (the migration index was significantly larger than 1). Therefore, it is considered that the battery resistance is increased.

  In Comparative Example 6, a negative electrode could not be produced. In Comparative Example 6, first wet granulated particles were produced using SBR instead of polyimide resin, and second wet granulated particles were produced using polyimide resin instead of SBR. For this reason, it is difficult to sufficiently improve the adhesion between the second wet granulated particles, and it is considered that the negative electrode could not be produced.

  In Comparative Example 7, the rate of change in peel strength (= (peel strength after heating) ÷ (peel strength before heating)) was significantly lower than 1. In Comparative Example 7, since the negative electrode active material, the polyimide resin, and SBR were mixed at the same time, SBR adhered preferentially to the surface of the negative electrode active material rather than the polyimide resin, and thus obtained by using the polyimide resin. It is considered that the effects obtained could not be obtained sufficiently.

  From Examples 1 to 5 and Example 6, it was found that similar results were obtained even when a polyamideimide resin was used instead of the polyimide resin.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  10 1st wet granulated particles, 11 negative electrode active material, 13 imide resin, 20 2nd wet granulated particles, 30 negative electrode, 31 negative electrode current collector, 33 negative electrode mixture layer.

Claims (1)

After the powder mixing of the negative electrode active material, carboxymethyl cellulose and the imide resin, further adding water to produce the first wet granulated particles,
Coating at least part of the surface of the first wet granulated particles with styrene butadiene rubber to produce second wet granulated particles;
A method for producing a negative electrode for a nonaqueous electrolyte secondary battery, comprising: transferring the second wet granulated particles to a negative electrode current collector.

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