JP6448681B2 - Lithium secondary battery negative electrode and manufacturing method thereof - Google Patents

Description

The present invention relates to a negative electrode for a lithium secondary battery using a silicon-based material as an active material and a method for producing the same.

Conventionally, a negative active material made of a carbon-based material such as graphite powder is bound to a negative electrode of a lithium secondary battery by an insulating organic polymer binder such as polyvinylidene fluoride or polytetrafluoroethylene, and this is collected into a copper foil or the like. A negative electrode using these carbon-based materials as an active material has a discharge capacity of about 350 mA · h / g at most. Therefore, a negative electrode active material having a larger capacity is used. It has been demanded.

Therefore, a negative electrode using a silicon-based material has been proposed as a next-generation negative electrode active material that can replace these carbon-based materials. Silicon-based materials are known to exhibit a discharge capacity several times that of graphite due to an alloying reaction with lithium, but the volume change associated with charge / discharge is so severe that it is not easy to extend the life of the negative electrode. .

As a method for improving the deterioration of cycle characteristics due to volume changes during repeated charge and discharge, silicon-based particles having an average particle size of 1 to 10 microns are bound using polyimide having excellent mechanical properties, and thermal pressurization is performed. A method of forming a negative electrode active material layer by treatment has been proposed (Patent Documents 1 to 5).

The negative electrode using the polyimide disclosed in the above-mentioned patent document as a binder is repeatedly formed by forming an island-like structure having a space that can absorb the volume expansion during charging when the active material layer is cracked when charged and discharged. Non-Patent Document 1 points out that the capacity retention rate in charge and discharge is improved.

Patent No. 4471836 Patent No. 4270894 Patent No. 4225727 Patent No.4212392 Patent No. 4033720

Proceedings of the 48th Battery Conference, 2B23, p.238 (2007) (Tatsuo Takano, Hidekazu Yamamoto, Atsushi Fukui, Taizo Sunano, Maruo Kanno, Shin Fujiya)

However, even the negative electrode using the polyimide disclosed in the prior art as a binder is not necessarily sufficient in improving the cycle characteristics due to the volume change of the silicon-based material, and further has good cycle characteristics and high discharge capacity. There was a need for a negative electrode.

Therefore, the present invention is to solve the above-described problems, and an object of the present invention is to provide a negative electrode having high discharge capacity and good cycle characteristics in a lithium secondary battery negative electrode using a silicon-based material as an active material. .

As a result of intensive studies to solve the above problems, the present inventors have solved the above problems by using a laminate in which an active material layer having specific characteristics is provided on a current collector as a negative electrode. As a result, the present invention has been completed.
That is, the present invention has the following purpose.

1) A laminate comprising a polyimide as a binder and silicon-based particles as an active material, and an active material layer having a porosity of 25 to 40% provided on a current collector, the silicon-based particles The average particle size of the polyimide is less than 1 μm, and the tetracarboxylic acid component of the polyimide is pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid , 3,3 ′, 4,4′-benzophenonetetra Carboxylic acid, 3,3 ', 4,4'-diphenylsulfone tetracarboxylic acid, 3,3', 4,4'-diphenyl ether tetracarboxylic acid, 2,3,3 ', 4'-benzophenone tetracarboxylic acid, 2 , 3,6,7-naphthalenetetracarboxylic acid, 1,4,5,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 3,3 ', 4,4'-diph Nylmethane tetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,4,9,10-tetracarboxy At least one selected from perylene, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane, and 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexafluoropropane der is, the lithium secondary battery negative electrode bonding strength of the current collector and the active material layer is characterized in der Rukoto least 3.0 N / cm.
2) A laminate comprising a polyimide as a binder and silicon-based particles as an active material, and an active material layer having a porosity of 25 to 40% provided on a current collector, the silicon-based particles And the polyimide has a diamine component of p-phenylenediamine, m-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane. 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane , 1,2-bis (anilino) ethane, diaminodiphenylsulfone, diaminobenz Anilide, diaminobenzoate, diaminodiphenyl sulfide, 2,2-bis (p-aminophen Nyl) propane, 2,2-bis (p-aminophenyl) hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, diaminobenzotrifluoride, 1,4-bis (p-aminophenoxy) benzene, 4,4 '-Bis (p-aminophenoxy) biphenyl, diaminoanthraquinone, 4,4'-bis (3-aminophenoxyphenyl) diphenylsulfone, 1,3-bis (anilino) hexafluoropropane, 1,4-bis (anilino) octafluorobutane, 1,5-bis (anilino) decafluoropentane, Ri least one der selected from 1,7-bis (anilino) tetradecanoyl fluoro heptane, the adhesive strength of the current collector and the active material layer 3 lithium secondary battery negative electrode, characterized in der Rukoto more .0N / cm.
3 ) A dispersion composed of silicon-based particles having an average particle size of less than 1 μm, a polyimide precursor, and a solvent is coated on the current collector, dried and thermally cured to collect an active material layer having a porosity of 25 to 40%. The method for producing a negative electrode for a lithium secondary battery according to 1) or 2) , wherein the negative electrode is formed on a body.

Since the laminate of the present invention has a high discharge capacity and good cycle characteristics, it can be suitably used as a lithium secondary battery negative electrode. In the production method of the present invention, a negative electrode having a high discharge capacity and good cycle characteristics can be easily produced by a simple process.

2 is a surface SEM image of a negative electrode obtained in Example 1. 2 is a surface SEM image of a negative electrode obtained in Comparative Example 1.

Hereinafter, the present invention will be described in detail.

In the lithium secondary battery negative electrode of the present invention, polyimide is used as a binder for the active material layer. The polyimide used in the present invention refers to an organic polymer having an imide bond in the main chain, such as polyimide, polyamideimide, and polyesterimide, and aromatic polyimide is particularly preferable among polyimides having the following chemical structural formula (1). Used.

Here, R ₁ represents a residue selected from a tetravalent aromatic residue, an aliphatic residue, and an alicyclic residue, and R ₂ represents a divalent aromatic residue, an aliphatic residue, and an alicyclic ring. Represents a residue selected from the group residues.

In the present invention, from the viewpoint of ensuring good cycle characteristics, among these polyimides, Tg (glass transition temperature) by DSC (differential scanning calorimetry) is preferably 150 ° C. or higher, and is in the range of 250 ° C. to 350 ° C. Is more preferable. The true density of these polyimides is preferably 1.2 g / cm ³ or more.

As a compounding quantity to the negative electrode active material layer of these polyimides, it is preferable that it is 1-30 mass%, and 5-25 mass% is still more preferable.

In the lithium secondary battery negative electrode of the present invention, a silicon-based material is used for the active material layer. Here, the silicon-based material means, for example, silicon, a silicon alloy, a silicon / silicon dioxide composite, or the like, and silicon can be preferably used. This silicon-based material can be used in the form of particles, and can be blended with the polyimide as a binder to form a negative electrode active material layer.

The shape of the silicon-based particles may be any shape such as an indefinite shape, a spherical shape, or a fibrous shape. Further, from the viewpoint of ensuring good cycle characteristics, the silicon-based material preferably has an average particle size of 5 μm or less, and more preferably less than 1 μm. The average particle diameter of the silicon-based particles in the present invention can be measured by, for example, a laser diffraction particle size distribution measuring device. In addition, this average particle diameter can be confirmed from the SEM image of the surface after producing a negative electrode using the silicon-based particles.

Moreover, as a compounding quantity of the silicon-type particle | grains to an active material layer, 55 mass% or more is preferable with respect to the active material layer mass, and 60 mass% or more is more preferable.

In order to reduce internal resistance as an electrode, the negative electrode active material layer of the present invention is blended with conductive particles such as carbon particles such as graphite and carbon black and metal particles such as silver, copper and nickel as necessary. can do. The average particle diameter of these carbon particles and metal particles is preferably 5 μm or less. As a compounding quantity to a negative electrode active material layer, it is preferable that it is 1-25 mass%, and 5-20 mass% is still more preferable.

The negative electrode active material layer of the present invention has a porosity of 15 to 40% by volume, more preferably 25 to 35% by volume. In the negative electrode of the present invention, by setting the porosity in advance as described above, the stress on the active material layer generated by the volume change accompanying the charge and discharge of the silicon-based material active material can be absorbed by the pores. It is considered that good cycle characteristics can be obtained without causing cracks in the active material layer during charging and discharging. Therefore, if the porosity is outside this range, the desired desirable cycle characteristics are often not obtained.

Here, the porosity is a value calculated from the apparent density of the active material layer, the true density (specific gravity) of each material (silicon-based material, polyimide, conductive particles, etc.) constituting the active material layer, and the blending amount. is there. For example, silicon-based material (true density A g / cm ³⁾ to X wt% polyimide (true density Bg / cm ³⁾ of Y weight%, conductive particles (true density C g / cm ³⁾ the Z mass% blending The porosity (%) when the apparent density of the negative electrode active material layer is D g / cm ³ is calculated from the following calculation formula.

(Equation 1)
Porosity = 100-D (X / A + Y / B + Z / C) (%)

In the present invention, when silicon is used as the silicon-based material, a value of 2.33 g / cm ³ can be used as the true density.

In the present invention, the thickness of the active material layer is arbitrary, but can be about 10 to 300 μm.

In the present invention, the negative electrode active material layer is formed on a current collector to form a negative electrode. As the current collector, a metal foil such as a copper foil, a stainless steel foil or a nickel foil can be used, and a copper foil such as an electrolytic copper foil or a rolled copper foil is preferably used. The thickness of these metal foils is preferably 5 to 50 μm, more preferably 9 to 18 μm. Further, the surface of these metals may be subjected to a roughening treatment or an antirust treatment for improving the adhesion. Moreover, what laminated | stacked the electroconductive contact bonding layer on the surface of these metal foil can also be used with a collector. The conductive adhesive layer can be formed by blending conductive particles such as graphite with an organic polymer compound.

The lithium secondary battery negative electrode of the present invention has a value of 3.0 N / cm or more as the adhesive strength between the current collector and the silicon-based active material layer. By setting the adhesive strength to the above, even if the porosity is in the above range, good adhesion between the current collector and the silicon-based active material layer is ensured, so that good cycle characteristics can be obtained. it is conceivable that.

Here, the adhesive strength is not fixed to the aluminum plate in a state where one conductor layer surface of the test piece is fixed to the aluminum plate using a double-sided adhesive tape for the test piece cut to a width of 10 mm and a length of 100 mm. This is a value obtained by measuring the interface between the silicon-based active material layer on the side and the current collector in a 180 ° direction at a speed of 50 mm / min.

The lithium secondary battery negative electrode of the present invention can be produced, for example, by the following method.

That is, a dispersion composed of silicon-based particles, a polyimide precursor, and a solvent is applied on a current collector, dried and thermally cured, and then an active material having a porosity of 15 to 40% by volume without performing heat and pressure treatment. It can be manufactured by forming a material layer on a current collector.

Here, the polyimide precursor solution is preferably a polyamic acid solution obtained by polymerizing a substantially equal mole of tetracarboxylic dianhydride and diamine as raw materials in a solvent. As reaction temperature at the time of manufacturing this polyamic acid solution, -30-60 degreeC is preferable and -15-40 degreeC is more preferable. In this reaction, the order of addition of the monomer and the solvent is not particularly limited, and may be any order.

Here, tetracarboxylic dianhydrides are, for example, pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid, 3,3 ′, 4. , 4'-diphenylsulfone tetracarboxylic acid, 3,3 ', 4,4'-diphenyl ether tetracarboxylic acid, 2,3,3', 4'-benzophenone tetracarboxylic acid, 2,3,6,7-naphthalenetetra Carboxylic acid, 1,4,5,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 3,3 ′, 4,4′-diphenylmethanetetracarboxylic acid, 2,2-bis ( 3,4-dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,4,9,10-tetracarboxyperile Dianhydrides such as 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane and 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexafluoropropane Can be used alone or as a mixture, but is not limited thereto.

Here, pyromellitic acid and 3,3 ′, 4,4′-biphenyltetracarboxylic acid are particularly preferably used.

Examples of the diamine include p-phenylenediamine, m-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4, 4'-diaminodiphenylmethane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,2-bis (anilino) ethane, diaminodiphenyl sulfone, diaminobenzanilide, diaminobenzoate, diaminodiphenyl sulfide, 2 , 2-bis (p-aminophenyl) propane, 2,2-bis (p-aminophenyl) hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, diaminobenzotrifluoride, 1,4-bis (p- Aminophenoxy) benze 4,4′-bis (p-aminophenoxy) biphenyl, diaminoanthraquinone, 4,4′-bis (3-aminophenoxyphenyl) diphenylsulfone, 1,3-bis (anilino) hexafluoropropane, 1,4- Bis (anilino) octafluorobutane, 1,5-bis (anilino) decafluoropentane, 1,7-bis (anilino) tetradecafluoroheptane, etc. can be used alone or as a mixture, but are not limited thereto is not.

Here, p-phenylenediamine, 4,4′-diaminodiphenyl ether, and 2,2-bis [4- (4-aminophenoxy) phenyl] propane are particularly preferably used.

As solid content concentration of polyamic acid, 1-50 mass% is preferable, and 5-25 mass% is more preferable. This polyamic acid solution may be partially imidized.

The viscosity of the polyimide precursor solution at 25 ° C. is preferably 1 to 150 Pa · s, and more preferably 5 to 100 Pa · s.

As a solvent used for the polyimide precursor solution, any solvent can be used as long as it dissolves the polyimide precursor, but an amide solvent is preferably used. Specific examples of the amide solvent include N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc) and the like. It can be used as a preferred solvent.

For example, various additives such as various surfactants and organic silane coupling agents can be added to the polyimide precursor solution as long as the effects of the present invention are not impaired. Moreover, the other polymer may be added in the range which does not impair the effect of this invention.

Next, a dispersion is obtained by mixing and dispersing silicon-based particles and conductive particles, if necessary, in the polyimide precursor solution.

Next, the silicon-based material dispersion is applied onto a metal foil and dried to form a polyimide precursor layer in which the silicon-based material is dispersed. In this drying step, the drying temperature is preferably 150 ° C. or lower, and more preferably 150 ° C. or lower. Next, it is preferable to perform thermosetting at a temperature of 250 ° C to 500 ° C. By this thermosetting, the polyimide precursor is converted to polyimide, and a silicon-based active material layer containing polyimide can be obtained. The polyimide precursor solution may be applied in a plurality of times. The atmosphere for thermosetting is preferably an inert gas atmosphere such as nitrogen gas, but can also be an air atmosphere or a vacuum.

Here, in order to make the porosity of the silicon-based material active material layer within the above range, if the total volume of the particle gap in the negative electrode active material layer exceeds the volume of the polyimide, “the total volume of the particle gap − Since pores corresponding to “the volume of the polyimide” are generated, the particle diameter and shape of the particles to be mixed and dispersed, and the composition of the dispersion described above may be adjusted. In the present invention, by setting the average particle size of the silicon-based particles to less than 1 μm, the porosity defined in the present invention can be obtained without performing the heat and pressure treatment. Although the silicon active material layer can be heat-pressed to adjust the porosity of the silicon active material layer, when the silicon active material layer is heat-pressed, the porosity of the active material surface decreases. However, when it is used as a negative electrode, the electrolyte does not easily penetrate and the discharge capacity tends to decrease. In addition, it is preferable to carry out in the range of (Tg + 50 degreeC)-(Tg + 150 degreeC) of the used polyimide as a process temperature in the case of carrying out a heat | fever pressurization process, As a pressure, the range of 10-100 kg / cm in conversion of a linear pressure It is preferable to carry out with.

When the silicon-based material dispersion is applied to the current collector, either a roll-to-roll continuous application method or a sheet-like application method can be employed, and either method may be used. As a coating apparatus used at this time, a die coater, a multilayer die coater, a gravure coater, a comma coater, a reverse roll coater, a doctor blade coater, or the like can be used.

As described above, the negative electrode of the lithium secondary battery of the present invention in which the silicon-based material active material layer containing polyimide is provided on the current collector can be manufactured by a simple process.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited only to these Examples.
In addition, the evaluation method of various characteristics and the synthesis method of the used polyimide precursor solution in the following examples and comparative examples are as follows.

[Evaluation method]
(1) Evaluation of discharge capacity Using the obtained negative electrode, a battery cell having a counter electrode made of lithium metal was constructed, and charging / discharging was repeated under the following conditions, and the first discharge capacity was defined as the discharge capacity. evaluated. Here, the discharge capacity is calculated based on the mass of the silicon-based particles.
○: Discharge capacity of 1000 mAh / g or more ×: Discharge capacity of less than 1000 mAh / g (cell configuration)
-Bipolar pouch cell-Counter electrode: metallic lithium-Electrolyte: 1M LiPF ₆ in EC + EMC + DMC = 1: 1: 1 (volume ratio)
(EC, EMC, and DMC are abbreviations for ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate, respectively.)
Measurement conditions and temperature: 30 ° C
・ Discharge range: 0.01V to 2V
・ Discharge current: 15 mA / g-negative electrode active material layer

(2) Evaluation of cycle characteristics The ratio of the discharge capacity of the 10th time with respect to the discharge capacity of the 2nd time in the said charging / discharging conditions was calculated | required, and the cycle characteristics were evaluated on the following references | standards.
○: Ratio of discharge capacity 0.9 or more ×: Ratio of discharge capacity less than 0.9

[Preparation method of polyimide (PI) precursor solution]
Abbreviations used in the following description are as follows.
<Polyimide raw material>
BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride 4,4′ODA: 4,4′-oxydianiline PDA: p-phenylenediamine <solvent>
NMP: N-methyl-2-pyrrolidone

<Preparation of PI precursor solution P-1>
By reacting approximately equimolar BPDA and 4,4′ODA at 40 ° C. in NMP in a nitrogen gas stream in a three-necked flask, the solid content concentration is 15 mass% and the viscosity at 25 ° C. is 85 Pa · A homogeneous solution of s polyamic acid was obtained. This solution is designated as PI precursor solution P-1.
The PI precursor solution was applied on a clean glass substrate by a bar coater so that the thickness of the heat-cured film was 15 μm, and dried at 130 ° C. for 10 minutes. Next, the temperature was raised from 100 ° C. to 350 ° C. in a nitrogen atmosphere over 2 hours, then heat treated at 350 ° C. for 1 hour, the PI precursor was thermoset and imidized, and then peeled off from the glass substrate to be transparent and nonporous PI film was obtained. This PI film had a DSC Tg of 285 ° C. and a true density of 1.40 g / cm ³ .

<Preparation of PI precursor solution P-2>
A uniform solution made of polyamic acid having a solid content concentration of 15% by mass and a viscosity at 25 ° C. of 88 Pa · s was obtained in the same manner as described above except that 4,4′ODA was changed to PDA. This solution is designated as PI precursor solution P-2.
From this solution, a transparent non-porous PI film having a thickness of 15 μm was obtained in the same manner as described above. This PI film had a DSC Tg of 400 ° C. or higher and a true density of 1.47 g / cm ³ .

<Method for producing silicon particle dispersion>
To the PI precursor solution obtained above, silicon particles having a predetermined average particle diameter and graphite particles having an average particle diameter of 3 μm are added in the composition shown in Table 1, and after stirring to uniformly disperse, NMP is added, Silicon dispersions a to f shown in Table 2 having a solid content concentration of 24.5% by mass were prepared.

[Examples 1-2, Comparative Examples 1-4]
On an electrolytic copper foil (F2-WS, manufactured by Furukawa Electric Co., Ltd.) having a thickness of 18 μm, the silicon particle dispersions a to f are uniform in a sheet-like manner using a bar coater so that the thickness of the coating after thermosetting is 30 to 50 μm. And dried at 130 ° C. for 10 minutes. Next, after heating this laminated body from 100 degreeC to 350 degreeC over 2 hours in nitrogen gas atmosphere, it heat-processed at 350 degreeC for 1 hour, the polyamic acid was thermosetted and imidized. These laminates were used as negative electrode samples without further heat and pressure treatment.

Table 3 shows the measurement results of the porosity and adhesion strength of each negative electrode sample, the discharge characteristics, and the evaluation results of the cycle characteristics.
Moreover, the SEM image of the active material layer surface obtained in Example 1 and Comparative Example 1 is shown in FIGS.
As shown in the figure, it can be seen that silicon particles having a predetermined average particle diameter are uniformly dispersed in the negative electrode active material layer together with the graphite particles without agglomeration.

  From the results of Examples 1 and 2 and Comparative Examples 1 to 4, the porosity of the active material layer was set to 15 to 40% which is the range of the present invention, and the adhesive strength between the active material layer and the copper foil was 3.0 N / It can be seen that a high discharge capacity and good cycle characteristics can be obtained by setting the thickness to cm or more. On the other hand, in the negative electrode samples of Comparative Examples 1 and 2 having a porosity exceeding 40%, although the discharge capacity was over 1000 mAh / g, the adhesive strength between the active material layer and the copper foil was low, so the repetition was repeated. It can be seen that the discharge capacity maintenance characteristic in charge and discharge is not sufficient and is not suitable as a negative electrode for a lithium secondary battery. Further, as shown in Comparative Examples 3 to 4, even when the adhesive strength between the active material layer and the copper foil is within the range of the present invention, when the porosity is 15% or less, the discharge capacity is low and the lithium secondary battery is low. It turns out that it is unsuitable as a negative electrode.

Claims (3)

A laminate comprising a polyimide as a binder and silicon-based particles as an active material, and an active material layer having a porosity of 25 to 40% provided on a current collector, the average of the silicon-based particles The particle size is less than 1 μm and the tetracarboxylic acid component of the polyimide is pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid , 3,3 ′, 4,4′-benzophenonetetracarboxylic acid 3,3 ', 4,4'-diphenylsulfone tetracarboxylic acid, 3,3', 4,4'-diphenyl ether tetracarboxylic acid, 2,3,3 ', 4'-benzophenone tetracarboxylic acid, 2,3 , 6,7-Naphthalenetetracarboxylic acid, 1,4,5,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 3,3 ', 4,4'-dipheni Methanetetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,4,9,10-tetracarboxyperylene , 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane, and 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexafluoropropane Ah is, the lithium secondary battery negative electrode bonding strength of the current collector and the active material layer is characterized in der Rukoto least 3.0 N / cm. A laminate comprising a polyimide as a binder and silicon-based particles as an active material, and an active material layer having a porosity of 25 to 40% provided on a current collector, the average of the silicon-based particles The particle size is less than 1 μm, and the diamine component of the polyimide is p-phenylenediamine, m-phenylenediamine, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 3 , 3′-dimethyl-4,4′-diaminodiphenylmethane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane , 1,2-bis (anilino) ethane, diaminodiphenylsulfone, diaminobenzanilide, Diaminobenzoate, diaminodiphenyl sulfide, 2,2-bis (p-aminophenyl) ) Propane, 2,2-bis (p-aminophenyl) hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, diaminobenzotrifluoride, 1,4-bis (p-aminophenoxy) benzene, 4,4 ' -Bis (p-aminophenoxy) biphenyl, diaminoanthraquinone, 4,4'-bis (3-aminophenoxyphenyl) diphenylsulfone, 1,3-bis (anilino) hexafluoropropane, 1,4-bis (anilino) octa fluoro butane, 1,5-bis (anilino) decafluoropentane, Ri least one der selected from 1,7-bis (anilino) tetradecanoyl fluoro heptane, the adhesive strength of the current collector and the active material layer 3. lithium secondary battery negative electrode, characterized in der Rukoto more 0N / cm. A dispersion composed of silicon-based particles having an average particle size of less than 1 μm, a polyimide precursor and a solvent is applied on the current collector, dried and thermally cured, and an active material layer having a porosity of 25 to 40% is formed on the current collector. The method for producing a negative electrode for a lithium secondary battery according to claim 1 or 2 , wherein the negative electrode is formed.