KR20200038932A - Electrode for lithium secondary battery and method for manufacturing same - Google Patents

Abstract

It is an object of the present invention to provide an electrode for a lithium secondary battery having excellent safety and sufficiently reduced internal resistance and a method for manufacturing the same. <1> An electrode for a lithium secondary battery in which a porous polyamideimide (PAI) layer is laminated and integrated on the surface of an electrode active material layer, wherein the porous PAI layer has the following characteristics. 1) The ionic conductivity of the porous PAI layer is 0.6 mS / cm or more. 2) The thickness of the porous PAI layer is more than 1 μm and less than 30 μm. <2> On the surface of the metal foil, which is a current collector of the electrode for a lithium secondary battery, a dispersion containing a binder, active material fine particles, and a solvent is applied and dried to form an electrode active material layer on the metal foil, and thereafter, the electrode active material layer A coating film containing PAI and a solvent is coated on the surface to form a coating film, and then, by removing the solvent in the coating film, phase separation occurs in the coating film to form an ion-permeable porous layer, and the electrode active material In a method for producing an electrode for a lithium secondary battery in which a layer and the ion-permeable porous layer are integrally stacked, the PAI contains 4,4'-diaminodiphenyl ether as a diamine component, and the solvent is 5 parts by mass or more and 20 parts by mass or more. Mixed solvent comprising the following amide-based solvent and 95 parts by mass or less and 80 parts by mass or more of tetraglyme (TG) (however, the amide-based solvent and TG are The total amount is 100 parts by mass), characterized in that the manufacturing method of the electrode for a lithium secondary battery.

Description

Electrode for lithium secondary battery and method for manufacturing same

The present invention relates to an electrode for a lithium secondary battery, which is excellent in safety, has a high capacity, and has good charge and discharge cycle characteristics, and a method for manufacturing the same.

In a lithium secondary battery, scratches and irregularities on the surface of the electrode may be the cause, and the electrical insulation of the separator in contact with the electrode may be destroyed. As a result, an electrical internal short circuit may occur.

In order to prevent this internal short circuit, in Patent Document 1, a solution in which a heat-resistant polymer such as polyamide imide (PAI) is dissolved is coated on the positive electrode surface, and then transferred to a coagulating solution containing a poor solvent for PAI. A method for producing a positive electrode for a lithium secondary battery in which a porous PAI layer and a positive electrode are integrated is proposed by immersing the positive electrode, depositing PAI or the like and drying it. However, since the ion permeability of the porous layer made of PAI or the like produced using such a method is not sufficient, there is a problem that the internal resistance of the electrode is increased, and as a result, good charge and discharge characteristics are not obtained. Moreover, the method of obtaining a porous layer using the above-mentioned coagulation liquid has a problem as a production method from the viewpoint of environmental compatibility since wastewater containing a poor solvent is generated from the coagulation bath.

As a method for solving the problem of the method of using such a coagulating solution, Patent Document 2 is applied to a surface of an electrode by applying a uniform solution containing a good solvent and a poor solvent for a heat-resistant polymer such as PAI to the electrode surface and drying it. A method for forming a porous layer has been proposed.

Japanese Patent Publication No. Hei 11-185731 International Publication 2014/106954

However, even in the electrode obtained by this method, in order to be an electrode for a lithium secondary battery that can be charged and discharged in a short time, it is not necessary to have sufficient ion permeability, further improve ion permeability, and to form a porous PAI layer with a lower internal resistance. there was.

Therefore, an object of the present invention is to provide an electrode for a lithium secondary battery having excellent safety and sufficiently reduced internal resistance as a solution to the above-described problems, and a method for manufacturing the same.

The present inventors discovered that the above problem is solved by an electrode in which a porous PAI layer obtained from a PAI solution obtained by specifying the chemical structure of the PAI and specifying the solvent composition of the PAI solution for application is stacked and integrated. It has been completed.

This invention aims at the following.

<1> An electrode for a lithium secondary battery in which a porous PAI layer is laminated and integrated on the surface of an electrode active material layer, wherein the porous PAI layer has the following characteristics.

1) The ionic conductivity of the porous PAI layer is 0.6 mS / cm or more.

2) The thickness of the porous PAI layer is more than 1 μm and less than 30 μm.

<2> On the surface of the metal foil, which is a current collector of the electrode for a lithium secondary battery, a dispersion containing a binder, active material fine particles, and a solvent is applied and dried to form an electrode active material layer on the metal foil, and thereafter, the electrode active material layer A coating film containing PAI and a solvent is coated on the surface to form a coating film, and then, by removing the solvent in the coating film, phase separation occurs in the coating film to form an ion-permeable porous layer, and the electrode active material In a method for producing an electrode for a lithium secondary battery in which a layer and the ion-permeable porous layer are layered and integrated, PAI contains 4,4'-diaminodiphenyl ether (DADE) as a diamine component, and the solvent is 5 parts by mass or more. Mixed solvent consisting of 20 parts by mass or less of an amide-based solvent and 95 parts by mass or less and 80 parts by mass or more of tetraglyme (TG) (however, the amide-based solvent and The total amount of TG is 100 parts by mass), characterized in that the lithium secondary battery electrode manufacturing method.

The manufacturing method of the said electrode for lithium secondary batteries whose content of <3> DADE is 30-100 mol% with respect to the whole diamine component.

Since the electrode for a lithium secondary battery of the present invention is excellent in ion permeability, the internal resistance of the electrode is low and safety is excellent.

Therefore, it can be suitably used as an electrode for a lithium secondary battery that can be charged and discharged in a short time. Moreover, in the manufacturing method of this invention, the electrode of this invention can be manufactured easily by a simple process.

In the electrode for a lithium secondary battery of the present invention, a porous PAI layer is layered and integrated on the surface of the electrode active material layer. The electrode for a lithium secondary battery is an electrode constituting a lithium secondary battery and refers to a positive electrode in which a positive electrode active material layer is bonded to a positive electrode current collector or a negative electrode in which a negative electrode active material layer is bonded to a negative electrode current collector. The electrode active material layer is a generic term for the positive electrode active material layer and the negative electrode active material layer.

As the current collector, metal foils such as copper foil, stainless steel foil, nickel foil, and aluminum foil can be used. Aluminum foil is preferably used for the anode and copper foil for the cathode. The thickness of these metal foils is preferably 5 to 50 μm, and more preferably 9 to 18 μm. The surface of these metal foils may be subjected to a roughening treatment or an antirust treatment for improving the adhesion with the active material layer.

The positive electrode active material layer is a layer obtained by binding positive electrode active material particles with a binder. As a material used as the positive electrode active material particles, it is preferable that lithium ions can be stored and stored, and those generally used as positive electrode active materials for lithium secondary batteries can be mentioned. For example, oxide-based (LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _4, etc.), complex oxide-based (LiCo _1/3 Ni _1/3 Mn _1/3 O _2, etc.), iron phosphate-based (LiFePO ₄ , Li ₂ FePO ₄ F, etc.), there may be mentioned the active material particles, such as polymer based compounds (polyaniline, polythiophene, etc.). Among these, LiCoO ₂ , LiNiO ₂ and LiFePO ₄ are preferred. The positive electrode active material layer may contain about 1 to 30% by mass of conductive particles such as carbon (graphite, carbon black, etc.) particles and metal (silver, copper, nickel, etc.) particles in order to lower its internal resistance.

The negative electrode active material layer is a layer obtained by binding negative electrode active material particles with a binder. As the material used as the negative electrode active material particles, it is preferable that lithium ions can be stored and stored, and those generally used as negative electrode active materials for lithium secondary batteries can be mentioned. For example, particles of an active material such as graphite, amorphous carbon, silicon-based, tin-based, etc. may be mentioned. Among these, graphite particles and silicon-based particles are preferable. Examples of the silicon-based particles include particles such as a silicon simple substance, a silicon alloy, and a silicon-silicon dioxide composite. Among these silicon-based particles, particles of silicon alone (hereinafter sometimes referred to as "silicon particles") are preferable. The silicon alone means crystalline or amorphous silicon having a purity of 95% by mass or more. The negative electrode active material layer may contain about 1 to 30% by mass of conductive particles such as carbon (graphite, carbon black, etc.) particles and metal (silver, copper, nickel, etc.) particles in order to lower its internal resistance.

The particle diameter of the active material particles or the conductive particles is preferably 50 μm or less for both the positive electrode and the negative electrode, and more preferably 10 μm or less. On the contrary, even if the particle diameter is too small, binding by the binder becomes difficult, so it is usually 0.1 μm or more, preferably 0.5 μm or more.

The porosity of the electrode active material layer is preferably 5 to 50% by volume for both the positive electrode and the negative electrode, and more preferably 10 to 40% by volume.

The thickness of the electrode active material layer is usually about 20 to 200 μm.

Examples of the binder for binding the active material particles include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, and styrene And other diene copolymer rubbers, polytetrafluoroethylene, polypropylene, polyethylene, and imide polymers. Among these, polyvinylidene fluoride, styrene-butadiene copolymer rubber, and imide polymer are preferred.

The active material layer of the positive electrode or the negative electrode may be coated with a dispersion comprising a binder, active material fine particles, and a solvent and dried to form an electrode active material layer on a metal foil.

In the electrode of the present invention, a porous PAI having high ion permeability is integrally laminated on the surface of the electrode active material layer.

The PAI constituting the porous PAI layer is a polymer obtained by performing a polycondensation reaction of a tricarboxylic acid component and a diamine component as raw materials.

The tricarboxylic acid component of PAI is an organic compound having three carboxyl groups per molecule (including derivatives thereof) and one or more aromatic rings, and among the three carboxyl groups, at least two carboxyl groups form an acid anhydride form They are placed where they can.

As an aromatic tricarboxylic acid component, a benzene tricarboxylic acid component and a naphthalene tricarboxylic acid component are mentioned, for example.

As a specific example of the benzene tricarboxylic acid component, for example, trimellitic acid, hemimelitic acid, and anhydrides thereof and monochloride thereof are exemplified.

As specific examples of the naphthalene tricarboxylic acid component, for example, 1,2,3-naphthalene tricarboxylic acid, 1,6,7-naphthalene tricarboxylic acid, 1,4,5-naphthalene tricarboxylic acid, and anhydrides thereof and mono thereof And chloride.

Among the aromatic tricarboxylic acid components, trimellitic anhydride and trimellitic anhydride (TAC) are preferred.

The tricarboxylic acid components may be used alone or in combination of two or more.

In addition, a part of the tricarboxylic acid component, such as terephthalic acid, isophthalic acid, pyromellitic acid, 3,3 ', 4,4'-biphenyltetracarboxylic acid, 3,3', 4,4'-benzophenonetetracarboxylic acid You may use what was substituted by the component.

The diamine component of PAI is an organic compound having two primary amino groups per molecule (including its derivatives).

It is preferable to contain DADE in the diamine component of PAI to form the porous PAI layer of this invention.

DADE is more preferably 30 to 100 mol%, more preferably 40 to 100 mol%, and particularly preferably 50 to 100 mol%, relative to the total diamine component of PAI. By using DADE as a diamine component in this way, good ion permeability can be ensured when a porous PAI layer is formed. Although the mechanism of the effect by incorporating such DADE is not certain, since the ether bond of DADE and the ether bond of TG, which is a poor solvent of PAI described later, interact with each other, a homogeneous porous structure is formed. Therefore, it is considered that good ion permeability is expressed.

As a specific example of the diamine component used by copolymerizing with DADE, m-phenylenediamine (MDA), p-phenylenediamine, 4,4'-diphenylmethanediamine (DMA), 4,4 ' -Diphenyl ether diamine, diphenyl sulfone-4,4'-diamine, diphenyl-4,4'-diamine, o-toluidine, 2,4-tolylenediamine, 2,6-tolylenedia Min, xylylenediamine, naphthalenediamine, and diisocyanate derivatives thereof.

Among these diamine components, MDA is preferred.

The diamine component used by copolymerization with the said DADE may be used individually or may be used in combination of 2 or more type.

PAI usually has a glass transition temperature of 200 ° C or higher. As the glass transition temperature, a value measured by DSC (differential thermal analysis) is used.

The PAI used in the present invention can be obtained using a known method. That is, for example, a compound obtained by mixing the tricarboxylic acid component and the diamine component as raw materials in approximately equimolar amounts and polymerizing them in the mixed solvent to isolate PAI as a powder can be used.

The porous PAI layer of the present invention needs to have an ion conductivity of 0.6 mS / cm or more. The ion conductivity is preferably 0.7 mS / cm or more, more preferably 0.8 mS / cm or more, and even more preferably 0.9 mS / cm or more. In an electrode in which a porous layer made of a heat-resistant polymer such as polyamide imide (PAI) is stacked and integrated, a porous layer exhibiting such high conductivity is not conventionally known, and is used as a porous PAI layer of the present invention.

The ion conductivity of the porous PAI layer can be determined by an alternating current impedance method, which is a known evaluation method. Specifically, the impedance of a cell made of a laminated electrode impregnated with an electrolyte and a cell made of an unstacked electrode is measured to obtain the resistance value (Ω) of the real parts in the Nyquist plot of both cells, and from the resistance value of the laminated electrode It can be calculated using the following calculation formula from the value "A" (Ω) obtained by subtracting the resistance value of the unstacked electrode.

  Ion conductivity (mS / cm) = 0.1 * B / (A * C)

Here, C is the electrode area (cm ² ), and B is the thickness of the porous PAI layer (μm). On the other hand, this ionic conductivity is a value evaluated as a laminated electrode in an electrolytic solution, and is not necessarily the same value as the ionic conductivity in the bulk state of a normal polymer material.

The porous PAI of the present invention needs to have a thickness of more than 1 μm and less than 30 μm, and preferably more than 5 μm and less than 25 μm. More preferably, it is more than 5 μm and less than 20 m. When the thickness is 1 μm or less, the insulating properties of the porous PAI layer are insufficient, and safety as an electrode may not be secured. In addition, if the thickness is 30 μm or more, the ion permeability is impaired, and when used as an electrode, the internal resistance increases.

The thickness of the porous PAI indicates a value calculated by obtaining an SEM image obtained by observing an electron microscope at a magnification of 500 times the cross section of the electrode in which the porous PAI is laminated and integrated.

On the surface of the electrode active material layer, for example, a coating liquid containing PAI and a solvent is applied to form a coating film, and then, by removing the solvent in the coating film, phase separation occurs in the coating film, resulting in a porous PAI layer. Can form.

This coating liquid can be obtained by dissolving the above-mentioned PAI powder in a solvent. As a solvent used here, it is preferable to use a mixed solvent composed of an amide-based solvent that is a good solvent for PAI and a TG (boiling point: 275 ° C), which is a poor solvent for PAI. As specific examples of the amide solvent, N-methyl-2-pyrrolidone (NMP, boiling point: 202 ° C), N, N-dimethylformamide (boiling point: 153 ° C), N, N-dimethylacetamide (DMAc , Boiling point: 166 ° C). These amide solvents may be used alone or in combination of two or more. Among these, NMP is preferable. Here, the good solvent means a solvent having a solubility in PAI of 1% by mass or more at 25 ° C. Poor solvent means a solvent having a solubility in PAI of less than 1% by mass at 25 ° C.

The mixed solvent is preferably 5 parts by mass or more and 20 parts by mass or less of an amide-based solvent and 95 parts by mass or less of 80 parts by mass or more of TG, and 10 parts by mass or more and 20 parts by mass or less of an amide-based solvent. It is more preferable to use a mixed solvent composed of 90 parts by mass or less and 80 parts by mass or more of TG. However, it is assumed that the mixed solvent is made by mixing an amide-based solvent and a TG positive solvent so that the total amount thereof is 100 parts by mass. By using such a mixed solvent, when the coating film is dried and removed, phase separation due to the boiling point difference of the solvent constituting the mixed solvent occurs efficiently in the coated film, thereby forming a porous layer having high ion permeability. In addition, the electrode active material layer and the porous PAI can be integrally stacked.

To the PAI coating liquid, well-known additives such as various surfactants and organic silane coupling agents may be added within a range not impairing the effects of the present invention. Further, a polymer other than PAI may be added to the PAI coating solution within a range not impairing the effects of the present invention. Furthermore, fillers such as alumina, silica, boehmite, and kaolin may be added as necessary.

A porous PAI having good ion permeability can be formed by applying the PAI coating solution to the surface of the electrode active material layer, drying at 100 to 150 ° C, and then performing heat treatment at 250 to 350 ° C as necessary. The porosity of the formed porous PAI can be 30 to 90% by volume. In addition, the average pore diameter of the imide porous layer can be 0.1 to 10 μm. By setting the porosity and the average pore diameter in such a range, good ion permeability is ensured. The porosity and the average pore diameter can be adjusted by selecting the type of the amide-based solvent in the PAI coating solution and the blending amount of TG. Moreover, porosity can also be adjusted by selecting drying conditions.

On the other hand, porosity (% by volume), when the apparent density of the imide porous layer is A (g / cm ³ ) and the true density of PAI is B (g / cm ³ ), it can be calculated using the following calculation formula. .

Porosity (% by volume) = 100-A * (100 / B)

In applying the PAI coating solution to the electrode surface, a method of continuously applying by roll-to-roll or a method of applying by single sheet may be adopted, and any method may be used. As the coating device, a die coater, multilayer die coater, gravure coater, comma coater, reverse roll coater, doctor blade coater, or the like can be used.

After forming a porous PAI film by applying and drying the above-mentioned coating liquid on a base material having a releasability such as a polyester film or aluminum foil, the electrode of the present invention is laminated integrally on the electrode active material, and thereafter. , It can also be obtained by peeling a substrate having release properties.

The electrode (anode and cathode) of the present invention can be configured by stacking a separator for a lithium secondary battery made of porous polyolefin or the like between the electrodes. Moreover, the electrode of this invention can also be used as an electrode for configuring a so-called "separatorless" cell without using such a separator.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples. Meanwhile, the present invention is not limited by examples.

The electrode (cathode) active material layers used in the following Examples and Comparative Examples were obtained as follows.

88 parts by mass of graphite particles (average particle diameter: 8 μm) as the negative electrode active material, 5 parts by mass of carbon black (acetylene black) as a conductive aid, and 7 parts by mass of PVDF as a binder resin are uniformly dispersed in N-methyl-2-pyrrolidone Thus, a negative electrode active material dispersion having a solid content concentration of 25% by mass was obtained. This dispersion was applied to a copper foil having a thickness of 18 μm, which is a negative electrode current collector, and the obtained coating film was dried at 150 ° C. for 20 minutes, followed by heat pressing to provide a negative electrode active material layer having a thickness of 100 μm formed on the copper foil (N- 1) was obtained.

The ion conductivity of the electrode obtained in the following examples and comparative examples was evaluated by the following method.

An electrode obtained by stacking and integrating a porous PAI layer on the surface of N-1 was punched into a circular shape having a diameter of 1.6 cm to form a symmetrical cell composed of an electrode / separator made of a polyethylene porous film (thickness of 20 μm) / electrode, Solvent: A mixed solvent in which ethylene carbonate and dimethyl carbonate are mixed at a ratio of 1: 1 by volume, electrolyte: 1M LiPF ₆ ) is injected, and stored in a flat cell made of stainless steel (manufactured by Takumi Kiken). C-1). On the other hand, in the same manner as described above, an evaluation cell (C-2) was obtained using N-1 (unlayered electrode).

The impedances of C-1 and C-2 were measured using an AC impedance measuring device (Celltest System 1470E manufactured by Solartron Analysis). The measurement conditions were as follows.

<Measurement conditions>

  Measurement temperature: 25 ℃

  Frequency range: 100 mHz to 1 MHz

  Amplitude: ± 10mV

The resistance value (Ω) of the real part in the Nyquist plot obtained by this AC impedance measurement is determined, and the resistance value (R-2) of C-2 is subtracted from the resistance value (R-1) of C-1, and this is 2 The value (A) divided by was taken as the resistance value (?) Of the porous PAI layer, and the ion conductivity of the porous PAI layer was calculated using the following calculation formula.

  Ion conductivity (mS / cm) = 0.0391 * B / A

Here, B represents the thickness (μm) of the porous PAI layer.

[Example 1]

In a dry nitrogen gas atmosphere, 0.07 mol of DADE and 0.03 mol of MDA were added to a glass reaction vessel, and 0.1 mol of NMP and triethylamine were added thereto, followed by stirring to obtain an NMP solution having a solid content concentration of 15% by mass. Then, while maintaining this solution at 10 ° C or lower, 0.1 mol of TAC NMP solution (solid content concentration: 20% by mass) was slowly added dropwise with stirring. After completion of dropping, the solution was returned to room temperature, and stirring was continued for 2 hours. The obtained solution was poured into a large amount of water to cause precipitation of PAI, and this was filtered and washed to obtain a yellow solid, and then heated to 200 ° C to dry and imidize the PAI powder ( AP). The Tg of the AP by DSC was 285 ° C. Next, AP was dissolved in a mixed solvent of NMP and TG to obtain a PAI coating solution (L-1) having a solid content concentration of 9% by mass. Here, the mixing ratio of NMP and TG was 85% by mass relative to the mixed solvent mass. By applying L-1 to the surface of the electrode (N-1) and drying at 150 ° C for 20 minutes, an electrode (P-1) having a porous PAI layer having a thickness of 10 μm was obtained. Table 1 shows the evaluation results of the porous PAI layer.

[Example 2]

The electrode (P-2) on which the porous PAI layer was formed was obtained in the same manner as in Example 1 except that only 0.1 mol of DADE was used as the diamine and the thickness of the porous PAI layer was 8 μm. Table 1 shows the evaluation results of the porous PAI layer.

[Example 3]

An electrode (P-3) having a porous PAI layer was obtained in the same manner as in Example 1 except that "a mixture of 0.05 mol of DADE and 0.05 mol of MDA" was used as the diamine. Table 1 shows the evaluation results of the porous PAI layer.

[Example 4]

An electrode (P-4) having a porous PAI layer was obtained in the same manner as in Example 1 except that "a mixture of 0.03 mol of DADE and 0.07 mol of MDA" was used as the diamine. Table 1 shows the evaluation results of the porous PAI layer.

[Example 5]

DMAc was used as an amide-based solvent, and a porous PAI layer-formed electrode (P-5) was obtained in the same manner as in Example 1 except that the thickness of the porous PAI layer was 6 μm. Table 1 shows the evaluation results of the porous PAI layer.

[Example 6]

An electrode (P-6) having a porous PAI layer was obtained in the same manner as in Example 1 except that "a mixture of 0.05 mol of DADE and 0.05 mol of DMA" was used as the diamine. Table 1 shows the evaluation results of the porous PAI layer.

[Example 7]

An electrode (P-7) having a porous PAI layer was obtained in the same manner as in Example 1, except that the thickness of the porous PAI was 15 μm. Table 1 shows the evaluation results of the porous PAI layer.

[Example 8]

An electrode (P-8) having a porous PAI layer was obtained in the same manner as in Example 1 except that the TG amount of the mixed solvent was 82% by mass relative to the mixed solvent mass. Table 1 shows the evaluation results of the porous PAI layer.

[Example 9]

The electrode (P-9) on which the porous PAI layer was formed was obtained in the same manner as in Example 1 except that the TG amount of the mixed solvent was 82% by mass relative to the mixed solvent mass, and the thickness of the porous PAI layer was 15 μm. Table 1 shows the evaluation results of the porous PAI layer.

[Example 10]

The electrode (P-10) in which the porous PAI layer was formed was obtained in the same manner as in Example 1 except that the TG amount of the mixed solvent was 87% by mass relative to the mixed solvent mass. Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 1]

An electrode (R-1) on which a porous PAI layer was formed was obtained in the same manner as in Example 1 except that "a mixture of 0.01 mol of DADE and 0.09 mol of MDA" was used as the diamine. Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 2]

An electrode (R-2) on which a porous PAI layer was formed was obtained in the same manner as in Example 1 except that "a mixture of 0.01 mol of DADE and 0.09 mol of DMA" was used as the diamine. Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 3]

An electrode (R-3) on which a porous PAI layer was formed was obtained in the same manner as in Example 1, except that "a mixture of 0.01 mol of DADE and 0.09 mol of MDA" was used as the diamine, and the thickness of the porous PAI layer was 6 μm. Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 4]

An electrode (R-4) having a porous PAI layer was obtained in the same manner as in Example 1, except that the TG amount of the mixed solvent was 75% by mass relative to the mixed solvent mass. Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 5]

The electrode (R-5) in which the porous PAI layer was formed was obtained in the same manner as in Example 1, except that the TG amount of the mixed solvent was 65% by mass relative to the mixed solvent mass. Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 6]

An electrode (R-6) having a porous PAI layer was obtained in the same manner as in Example 1, except that the thickness of the porous PAI layer was 35 μm. Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 7]

The electrode (R-7) on which the porous PAI layer was formed was obtained in the same manner as in Example 1 except that only 0.1 mol of DADE was used as the diamine, and the thickness of the porous PAI layer was 35 μm. Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 8]

An electrode (R-8) having a porous PAI layer was obtained in the same manner as in Example 1 except that only 0.1 mol of DMA was used as the diamine. Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 9]

An electrode (R-9) having a porous PAI layer was obtained in the same manner as in Example 1 except that only 0.1 mol of MDA was used as the diamine. Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 10]

An electrode (R-10) on which a porous PAI layer was formed was obtained in the same manner as in Example 1 except that the TG of the mixed solvent was triethylene glycol dimethyl ether (TRG). Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 11]

An electrode (R-11) on which a porous PAI layer was formed was obtained in the same manner as in Example 1 except that the TG of the mixed solvent was diethylene glycol dimethyl ether (DG). Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 12]

An electrode (R-12) having a porous PAI layer was obtained in the same manner as in Example 1 except that the solvent for dissolving the AP obtained in Example 1 was NMP only. Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 13]

An electrode (R-13) on which a porous PAI layer was formed was obtained in the same manner as in Example 1 except that "a mixture of 0.02 mol of DADE and 0.08 mol of MDA" was used as the diamine. Table 1 shows the evaluation results of the porous PAI layer.

[Comparative Example 14]

An electrode (R-14) on which a porous PAI layer was formed was obtained in the same manner as in Example 1 except that "a mixture of 0.02 mol of DADE and 0.08 mol of DMA" was used as the diamine. Table 1 shows the evaluation results of the porous PAI layer.

As described above, in the Examples and Comparative Examples, since the resistance of the porous PAI layer of the present invention having a specific ionic conductivity and thickness is sufficiently lowered, the electrode integrated with this stacking is for a lithium secondary battery with increased safety. It can be suitably used as an electrode. In addition, it can be seen that good cycle characteristics can be obtained by this effect. Further, according to the manufacturing method of the present invention, an electrode having high environmental suitability and excellent safety in a simple process can be manufactured.

The electrode for a lithium secondary battery of the present invention can be suitably used as an electrode for a lithium secondary battery that can be charged and discharged in a short time and has high safety because its internal resistance is sufficiently low. According to the manufacturing method of the present invention, it is possible to manufacture an electrode having high environmental suitability and excellent safety in a simple process.

Claims (3)

An electrode for a lithium secondary battery in which a porous polyamideimide (PAI) layer is laminated and integrated on a surface of an electrode active material layer, wherein the porous PAI layer has the following characteristics.
1) The ionic conductivity of the porous PAI layer is 0.6 mS / cm or more.
2) The thickness of the porous PAI layer is more than 1 μm and less than 30 μm. On the surface of the metal foil, which is the current collector of the electrode for a lithium secondary battery, a dispersion containing a binder and active material fine particles and a solvent is applied and dried to form an electrode active material layer on the metal foil, and thereafter, PAI on the surface of the electrode active material layer. Forming a coating film by applying a coating solution containing a solvent and a solvent, and then removing the solvent in the coating film to cause phase separation in the coating film to form an ion-permeable porous layer, and the electrode active material layer and the In a method for producing an electrode for a lithium secondary battery in which an ion-permeable porous layer is laminated and integrated, PAI contains 4,4'-diaminodiphenyl ether (DADE) as a diamine component, and the solvent is 5 parts by mass or more and 20 parts by mass or more. Mixed solvent comprising the following amide-based solvent and 95 parts by mass or less and 80 parts by mass or more of tetraglyme (TG) (however, the amide-based solvent and TG are Method for manufacturing a lithium secondary battery electrode as set forth in claim 5, characterized in that the weighing is 100 parts by mass). According to claim 2,
The manufacturing method of the electrode for lithium secondary batteries whose content of DADE is 30-100 mol% with respect to the whole diamine component.