Electrode for lithium ion secondary battery and lithium ion secondary battery

Abstract

The present invention provides an electrode that suppresses the influence of heat generation caused by an external impact on a lithium-ion secondary battery. The present invention provides a lithium-ion secondary battery electrode, characterized by having a metal foil, a conductive layer formed on at least a part of the above-mentioned metal foil, and an active material layer formed on at least a part of the surface of the above-mentioned conductive layer on the side opposite to the metal foil side. The above-mentioned conductive layer contains conductive particles and an insulating resin. The above-mentioned active material layer contains a first active material layer and a second active material layer. The above-mentioned first active material layer and the above-mentioned second active material layer are laminated in such a way that the above-mentioned first active material layer is on the side closer to the above-mentioned conductive layer, and the above-mentioned second active material layer has a larger porosity than the above-mentioned first active material layer.

Description

Technical Field

[0001] The present invention relates to an electrode for a lithium ion secondary battery and a lithium ion secondary battery. Background Art

[0002] Lithium ion secondary batteries are widely used as power sources for portable electronic devices because they are lighter in weight and have a higher energy density than nickel-cadmium batteries, nickel-metal hydride batteries, etc. In addition, they have become a strong candidate as a power source for hybrid vehicles and electric vehicles. Moreover, with the miniaturization and high functionality of portable electronic devices in recent years, further high energy density is expected for lithium ion secondary batteries that are these power sources.

[0003] Although existing lithium ion secondary batteries are also at a high level in terms of safety, further improvement is expected in terms of safety due to their high capacity and high output. For example, when a lithium ion secondary battery is overcharged, it may generate heat. In addition, heat may also be generated due to the occurrence of an internal short circuit. Further, since a lithium ion secondary battery includes a non-aqueous electrolyte containing an organic solvent, as heat is generated, the organic solvent chemically decomposes to generate gas, and adverse conditions such as an increase in the internal pressure of the battery may occur.

[0004] Regarding such problems, a technique of providing a conductive layer on the surface of a current collector is proposed in Patent Document 1.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: International Publication No. 2017 / 014245 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] However, in the lithium ion secondary battery described in Patent Document 1, there are technical problems such as insufficient response to locally rapid heat generation caused by an external impact. The inventors of the present invention repeatedly conducted in-depth research and found that, in addition to controlling the current generated in the short-circuited portion, a structure for dissipating the heat generated in the short-circuited portion is formed, thereby solving the technical problems.

[0010] The invention was developed in view of the above technical problems, and provides an electrode that suppresses the influence of heat generation caused by an external impact on a lithium ion secondary battery.

[0011] Means for Solving the Technical Problems

[0012] In order to achieve the above object, the electrode for a lithium ion secondary battery provided by the present invention is characterized in that it has a metal foil, a conductive layer formed on at least a part of the metal foil, and an active material layer formed on at least a part of the surface of the conductive layer on the side opposite to the metal foil side. The conductive layer contains conductive particles and an insulating resin. The active material layer contains a first active material layer and a second active material layer. The first active material layer and the second active material layer are laminated in such a way that the first active material layer is on the side closer to the conductive layer, and the second active material layer has a larger porosity than the first active material layer.

[0013] When an impact is applied to the lithium ion secondary battery of the present invention and an internal short circuit occurs, the insulating resin contained in the conductive layer flows into the short circuit portion, and the short circuit resistance increases, so that the amount of current generated due to the internal short circuit can be suppressed. In addition, since the porosity of the second active material layer of the electrode is large, the thermal conductivity is reduced. Therefore, the movement of heat generated from the internal short circuit portion is less likely to cause between the opposing positive and negative electrodes, and preferentially moves through the current collector with high heat dissipation. Therefore, the temperature of the short circuit portion is not likely to rise, and the influence of heat generation can be reduced.

[0014] In addition, when the occupied area per unit area of the conductive particles when observing the conductive layer in the thickness direction is set as A, and the occupied area per unit area of the insulating resin is set as B, it is preferably 0.11 ≤ A / B ≤ 1.0.

[0015] Accordingly, without reducing the output of the lithium ion secondary battery, the resistance of the short circuit portion can be increased, and the effect of the present invention can be further improved.

[0016] In addition, when the porosity of the second active material layer in the active material layer is set as C, and the porosity of the first active material layer is set as D, it is preferably 1.2 ≤ C / D ≤ 3.5.

[0017] Accordingly, without reducing the output of the lithium ion secondary battery, the heat generated at the internal short circuit portion can be effectively dissipated through the current collector, and the effect of the present invention can be further improved.

[0018] Advantages of the Invention

[0019] According to the present invention, it is possible to obtain an electrode for a lithium ion secondary battery that can reduce the influence of heat generation even when an impact is applied to the lithium ion secondary battery and an internal short circuit occurs, and a lithium ion secondary battery using the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic cross-sectional view of a laminate of a lithium ion secondary battery according to an embodiment of the present invention.

[0021] Description of the Reference Numerals

[0022] 1... positive electrode active material, 1a... first positive electrode active material layer, 1b... second positive electrode active material layer, 2... conductive layer provided on the positive electrode, 3... positive electrode current collector, 4... separator, 5... negative electrode active material, 5a... first negative electrode active material layer, 5b... second negative electrode active material layer, 6... conductive layer provided on the negative electrode, 7... negative electrode current collector, 8, 9... lead wires, 10... laminate of the lithium ion secondary battery. Detailed implementation mode

[0023] Hereinafter, embodiments suitable for the present invention will be described for the present invention. In addition, the present invention is not limited to the following embodiments.

[0024] 〈Lithium ion secondary battery〉

[0025] Figure 1 It shows a schematic cross-sectional view of the laminate of the lithium ion secondary battery of this embodiment.

[0026] By manufacturing a positive electrode composed of 1, 2, and 3, a negative electrode composed of 5, 6, and 7, and a separator 4 impregnated with an electrolyte in the manner as Figure 1 such, a laminate 10 of the lithium ion secondary battery can be manufactured. Here, the positive electrode can be manufactured by forming a positive electrode active material layer 1 on the positive electrode current collector 3 or on a conductive layer 2 formed on the positive electrode current collector, and the negative electrode can be manufactured by forming a negative electrode active material layer 5 on the negative electrode current collector 7 or on a conductive layer 6 formed on the negative electrode current collector. However, in order to exert the effects of the present invention, in addition to forming a conductive layer 2 between the positive electrode current collector 3 and the positive electrode active material layer 1, or forming a conductive layer 6 between the negative electrode current collector 7 and the negative electrode active material layer 5, it is also necessary to form the positive electrode active material layer 1 by dividing it into two layers, namely the positive electrode active material layer 1a and 1b, or form the negative electrode active material layer 5 by dividing it into two layers, namely the negative electrode active material layer 5a and 5b. In addition, 8 and 9 in the drawings respectively represent the lead-out electrodes of the positive electrode and the negative electrode.

[0027] 〈Metal foil with a conductive layer〉

[0028] The metal foil with a conductive layer of this embodiment is characterized by having: a metal foil, a conductive layer formed on at least a part of the above metal foil, and an active material layer formed on at least a part of the side of the above conductive layer opposite to the metal foil, and the above conductive layer contains conductive particles and an insulating resin.

[0029] When an impact is externally applied to a lithium-ion secondary battery and an internal short-circuit condition occurs, in a lithium-ion secondary battery without such a countermeasure, the resistance of the short-circuit portion formed by the active material layers constituting the positive electrode and the negative electrode or only the current collector is low. Therefore, a large current is generated. However, according to the present embodiment, since the conductive layer of the current collector contains an insulating resin, when an internal short-circuit occurs, the insulating resin flows into the short-circuit portion, increasing the resistance of the short-circuit portion and suppressing the generation of a large current.

[0030] The metal foil only needs to be a conductive plate material. For example, as the negative electrode, thin metal plates (metal foils) such as copper, nickel, their alloys, and stainless steel can be used. As the positive electrode, thin metal plates (metal foils) such as aluminum, their alloys, and stainless steel can be used.

[0031] The ratio of the conductive particles and the insulating resin contained in the conductive layer can be obtained based on the areas of the two when observing the metal foil forming the conductive layer from the thickness direction (i.e., looking down from the side opposite to the conductive layer). When the area occupied by the conductive particles in a specified area is set as A and the area of the insulating resin is set as B, it is preferably 0.11 ≤ A / B ≤ 1.0. By being within this range, the resistance of the short-circuit portion can be maintained at a sufficiently high value, and the rate characteristics during normal use of a lithium-ion secondary battery can also be maintained at a better value. Since the conductive particles in the conductive layer function as an electron conduction path between the current collector and the active material layer, when the proportion of the conductive particles is small, the rate characteristics may deteriorate.

[0032] Preferably, the insulating resin has a resistance value that can suppress the generation of a large current when an internal short-circuit occurs, and the resistance value is preferably 1.0×10 8 [Ωcm] or more.

[0033] The conductive particles are not particularly limited as long as they are materials with good conductivity, and examples include carbon-based materials, or metal fine powders such as copper, nickel, stainless steel, and iron, mixtures of carbon materials and metal fine powders, and conductive oxides such as ITO. However, from the perspective of compatibility with the resin material, a carbon-based material is particularly preferred. Among the carbon-based materials, for example, carbon black, graphene, carbon nanofibers, carbon nanotubes, carbon nanowalls, and graphite can be cited.

[0034] 〈Double-layer active material layer〉

[0035] The active material layer of the present embodiment is characterized by including a first active material layer and a second active material layer, and the first active material layer and the second active material layer are laminated such that the first active material layer is on the side closer to the conductive layer, and the second active material layer has a larger porosity than the first active material layer.

[0036] The active material layer has the function of controlling the heat conduction generated due to internal short circuit. Since the second active material layer has a large porosity, its thermal conductivity is low. The heat generated at the internal short circuit site is less likely to move between the opposing positive and negative electrodes, but preferentially moves through the current collector with high heat dissipation. Therefore, the local temperature rise at the short circuit site can be further suppressed.

[0037] When the porosity of the second active material layer is C and the porosity of the first active material layer is D, the ratio of the porosity in the active material layer is preferably 1.2 ≤ C / D ≤ 3.5. By being within this range, the reduction in the energy density of the lithium-ion secondary battery is suppressed, and by preferentially dissipating the heat generated at the internal short circuit site from the current collector with high heat dissipation, the local temperature rise at the short circuit site can be further suppressed.

[0038] 〈Measurement of the porosity of the active material layer〉

[0039] For the porosity of each of the first active material layer and the second active material layer, measurement and calculation are performed using cross-sectional SEM. First, the thicknesses of the first active material layer and the second active material layer are measured by cross-sectional SEM, and the density is calculated based on the relationship between the area weight and the thickness. Then, the porosity is calculated based on the following calculation formula.

[0040] Porosity = (1 - density ÷ true density calculated from the material constituting each layer) × 100

[0041] 〈Formation of the conductive layer on the current collector〉

[0042] Conductive particles and insulating resin are mixed and dispersed in solvents such as water and N-methyl-2-pyrrolidone to prepare a paste-like slurry. Then, the slurry is coated on one or both sides of a current collector such as aluminum foil or copper foil using, for example, a comma roll coater to form a coating film with a specified thickness, and the solvent is evaporated by introducing it into a drying furnace. In addition, when coating both sides of the current collector, it is preferable that the thickness of the coating film that becomes the conductive layer is the same on both sides. Alternatively, after the solvent is evaporated, pressure forming can be performed by rolling. The thickness of the conductive layer is preferably 1 [μm] or more and less than 10 [μm]. Thus, in the case where an impact is applied to the lithium-ion secondary battery from the outside and an internal short circuit occurs, it plays a role in further increasing the resistance at the short circuit site, and at the same time, the output is not reduced during normal use.

[0043] 〈Positive electrode〉

[0044] The positive electrode can be fabricated by forming a positive electrode active material layer 1 on a positive electrode current collector 3 or on a conductive layer 2 formed on the positive electrode current collector as described below. Further, in the case where the positive electrode active material layer is formed by dividing it into a first active material layer and the above-mentioned second active material layer, first, the first active material layer is formed on the conductive layer 2 formed on the positive electrode current collector, and the second active material layer is further formed thereon.

[0045] (Positive electrode current collector)

[0046] The positive electrode current collector 3 only needs to be a conductive plate material. For example, metal thin plates (metal foils) such as aluminum or their alloys, and stainless steel can be used.

[0047] (Positive electrode active material layer)

[0048] The positive electrode active material layer 1 mainly consists of a positive electrode active material, a positive electrode binder, and a positive electrode conductive additive in an amount corresponding to the need.

[0049] (Positive electrode active material)

[0050] As the positive electrode active material, as long as it can reversibly adsorb and release lithium ions, deintercalate and intercalate (intercalate) lithium ions, or dope and de-dope lithium ions and the counter anion of the lithium ion (for example, PF6 - ), there is no particular limitation, and known electrode active materials can be used. For example, lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium manganese spinel (LiMn2O4), and the general formula: LiNi x Co y Mn z M a O2 (x + y + z + a = 1, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ a ≤ 1, M is one or more elements selected from Al, Mg, Nb, Ti, Cu, Zn, Cr), lithium vanadium compound (LiV2O5), olivine-type LiMPO4 (where M represents one or more elements selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr or VO), lithium titanate (Li4Ti5O 12 ), LiNi x Co y Al z O2 (0.9 < x + y + z < 1.1) and other composite metal oxides.

[0051] (Positive electrode binder)

[0052] The binder for the positive electrode binds the positive electrode active materials to each other and binds the positive electrode active materials and the current collector. Any binder capable of performing the above binding can be used. For example, fluororesins such as polyvinylidene fluoride (PVdF) and polytetrafluoroethylene (PTFE) can be cited. In addition, in addition to the above, as the binder, for example, cellulose, styrene-butadiene rubber, ethylene-propylene rubber, polyimide resin, polyamideimide resin, etc. can also be used. In addition, as the binder, an electronically conductive conductive polymer and an ionically conductive conductive polymer can also be used. As the electronically conductive conductive polymer, for example, polyacetylene, etc. can be cited. In this case, the binder also functions as a conductive aid particle, so the conductive aid may not be added. As the ionically conductive conductive polymer, for example, a substance having conductivity of ions such as lithium ions can be used. For example, a substance obtained by compounding a monomer of a polymer compound (a polyether-based polymer compound such as polyethylene oxide and polypropylene oxide, polyphosphazene, etc.) and a lithium salt such as LiClO4, LiBF4, LiPF6 or an alkali metal salt mainly composed of lithium can be cited. As the polymerization initiator for compounding, for example, a photopolymerization initiator or a thermal polymerization initiator suitable for the above monomers can be cited.

[0053] (Conductive aid for positive electrode)

[0054] The conductive aid for the positive electrode is not particularly limited as long as it is a substance that makes the positive electrode active material layer have good conductivity, and known conductive aids can be used. For example, carbon-based materials such as graphite and carbon black, and metal fine powders such as copper, nickel, stainless steel, and iron, a mixture of a carbon material and a metal fine powder, and conductive oxides such as ITO can be cited.

[0055] 〈Negative electrode〉

[0056] The negative electrode can be manufactured by forming a negative electrode active material layer 5 on a negative electrode current collector 7 or a conductive layer 6 formed on the negative electrode current collector as described below. In addition, in the case where the negative electrode active material layer is formed by dividing it into a first active material layer and the above second active material layer, first, the first active material layer is formed on the conductive layer 6 formed on the negative electrode current collector, and the second active material layer is further formed on the first active material layer.

[0057] (Negative electrode current collector)

[0058] The negative electrode current collector 7 only needs to be a conductive plate material. For example, metal thin plates (metal foils) such as copper, nickel or their alloys, and stainless steel can be used.

[0059] (Negative electrode active material layer)

[0060] The negative electrode active material layer 5 is mainly composed of a negative electrode active material, a binder for the negative electrode, and a conductive assistant for the negative electrode in an amount corresponding to requirements.

[0061] (Negative electrode active material)

[0062] Examples of the negative electrode active material include graphite, silicon oxide (SiO x ), metallic silicon (Si), etc.

[0063] (Binder for the negative electrode)

[0064] There is no particular limitation on the binder for the negative electrode, and the same binders as those described above for the positive electrode can be used.

[0065] The content of the binder in the negative electrode active material layer 5 is not particularly limited, and is preferably 1 to 20 parts by mass of the entire negative electrode active material layer.

[0066] (Conductive assistant for the negative electrode)

[0067] There is no particular limitation on the conductive assistant for the negative electrode, and the same conductive assistants as those described above for the positive electrode can be used.

[0068] 〈Electrolyte〉

[0069] As the electrolyte, salts such as LiPF6, LiClO4, LiBF4, LiAsF6, LiCF3SO3, LiCF3, CF2SO3, LiC(CF3SO2)3, LiN(CF3SO2)2, LiN(CF3CF2SO2)2, LiN(CF3SO2)(C4F9SO2), LiN(CF3CF2CO)2, LiBOB can be used. In addition, these salts can be used alone or in combination of two or more.

[0070] The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments.

[0071] Examples

[0072] Hereinafter, the present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to the following examples.

[0073] <Example 1>

[0074] (Formation of the conductive layer on the current collector)

[0075] In Example 1, 1.1 parts by mass of acetylene black as conductive particles, 1.0 part by mass of PVdF as insulating resin, and N-methylpyrrolidone as a solvent were mixed to prepare a slurry for forming a conductive layer. The slurry was coated on both sides of an aluminum foil with a thickness of 12 [μm] and dried at 100 [°C], whereby a positive current collector having a conductive layer with a thickness of 0.90 [μm] was obtained.

[0076] (Fabrication of the positive electrode)

[0077] 96 parts by mass of LiCoO2 as a positive electrode active material, 2 parts by mass of acetylene black as a conductive additive, 2 parts by mass of PVdF as a binder, and N-methylpyrrolidone as a solvent were mixed to prepare a slurry for forming an active material layer. The slurry was coated on both sides of the positive current collector having the conductive layer obtained above and dried at 100 [°C], whereby a first active material layer was obtained. Then, the slurry was coated on both sides of the first active material layer obtained above and dried at 100 [°C], whereby a second active material layer was obtained. Then, pressure forming was performed by roll pressing, thereby obtaining a positive electrode having a positive electrode active material layer.

[0078] (Fabrication of the negative electrode)

[0079] 83 parts by mass of Si as a negative electrode active material, 2 parts by mass of acetylene black as a conductive additive, 15 parts by mass of polyamideimide as a binder, and N-methylpyrrolidone as a solvent were mixed to prepare a slurry for forming an active material layer. The slurry was coated on both sides of a copper foil with a thickness of 10 [μm], dried at 100 [°C], and then pressure forming was performed by roll pressing, and heat treatment was performed at 350 [°C] for 3 hours in a vacuum, whereby a negative electrode having a negative electrode active material layer was obtained.

[0080] (Fabrication of the evaluation lithium-ion secondary battery)

[0081] The positive electrode and the negative electrode fabricated above were placed in an aluminum laminated packaging bag with a separator made of a polyethylene microporous membrane sandwiched therebetween, and a 1 M LiPF6 solution (solvent: ethylene carbonate / diethyl carbonate = 3 / 7 (volume ratio)) as an electrolyte was injected into the aluminum laminated packaging bag, and then vacuum sealed to fabricate an evaluation lithium-ion secondary battery.

[0082] 〈Measurement of rate performance〉

[0083] Regarding the evaluation lithium-ion secondary battery fabricated in Example 1, using a secondary battery charge-discharge test device (manufactured by Hokuto Denko Corporation), in a thermostatic bath at a temperature of 25°C, the voltage range was set to 2.8 [V] to 4.2 [V], and charging and discharging were performed for one cycle at a current value of 0.05C. The capacity was confirmed to be normal. Similarly, after charging at a current value of 0.05C, discharging was performed at a current value of 0.2C or 2C, the discharge capacity at each rate was obtained, and the rate characteristics (100×2C discharge capacity / 0.2C discharge capacity) were obtained. When the resistance value of the conductive layer formed on the positive electrode current collector is low, it does not hinder the movement of electrons at high rates, and thus, a high retention rate is exhibited.

[0084] 〈Measurement of Battery Surface Temperature〉

[0085] Regarding the evaluation lithium-ion secondary battery fabricated in Example 1, using a secondary battery charge-discharge test device (manufactured by Hokuto Denko Corporation), after charging to 4.2 [V] in a thermostatic bath at a temperature of 25 [°C], a nail penetration test was performed. In the nail penetration test, in a thermostatic bath at a temperature of 25 [°C], the above-mentioned evaluation lithium-ion secondary battery was fixed to a phenolic resin plate with a hole having a diameter of 10 [mm], and an iron nail with a diameter of 3 [mm] and a length of 65 [mm] was vertically inserted into the above-mentioned evaluation lithium-ion secondary battery at a speed of 10 [mm / s]. After penetrating 10 [mm] through the battery and maintaining for 3 minutes, the nail was pulled out. After inserting the nail into the battery, the battery surface temperature was measured 30 seconds later.

[0086] <Examples 2 to 11>

[0087] Except for changing the ratio of the conductive particles and the insulating resin contained in the conductive layer, the porosity of the second active material layer in the active material layer, and the porosity of the first active material layer as shown in Table 1, the rest was carried out in the same manner as in Example 1 to obtain the lithium-ion secondary batteries of Examples 2 to 11. In addition, using the obtained lithium-ion secondary batteries, the rate characteristics and the measurement of the battery surface temperature of Examples 2 to 11 were carried out in the same manner as in Example 1.

[0088] The evaluation results of Examples 1 to 11 are shown in Table 1. As in Examples 1 to 11, a conductive layer was formed on the positive electrode current collector, and the porosity of the second active material layer in the active material layer was made larger than the porosity of the first active material layer, whereby a low battery surface temperature was exhibited. In addition, by setting the ratio of the porosity of the second active material layer to the porosity of the first active material layer, i.e., C / D, within an appropriate range, a tendency to exhibit an even lower battery surface temperature was confirmed. In addition, it was confirmed that by setting the ratio of the conductive particles and the insulating resin contained in the conductive layer, i.e., A / B, within an appropriate range, a tendency to exhibit high rate characteristics and a low battery surface temperature was presented.

[0089] <Comparative Examples 1 to 3>

[0090] Except for changing the presence or absence of the conductive layer, the ratio of the conductive particles and the insulating resin contained in the conductive layer, and the porosity of the second active material layer and the porosity of the first active material layer in the active material layer to the values shown in Table 1, lithium ion secondary batteries of Comparative Examples 1 to 3 were obtained in the same manner as in Example 1. In addition, using the obtained lithium ion secondary batteries, the rate characteristics and the measurement of the battery surface temperature of Comparative Examples 1 to 3 were carried out in the same manner as in Example 1.

[0091] The evaluation results of Comparative Examples 1 to 3 are shown in Table 1. In Comparative Example 1, there was no conductive layer, and a relatively high battery surface temperature was presented. In addition, in Comparative Example 2, although A / B of the conductive layer was within an appropriate range, the porosity of the second active material layer was smaller than the porosity of the first active material layer. Therefore, a relatively high battery surface temperature was presented. In addition, in Comparative Example 3, except that there was no conductive layer, the porosity of the second active material layer was also smaller than the porosity of the first active material layer. Therefore, the highest battery surface temperature was presented.

[0092] [Table 1]

[0093]

[0094] Industrial Applicability

[0095] By providing a conductive layer on the current collector and forming the active material layer into two layers of a second active material layer with a large porosity and a first active material layer with a small porosity, a lithium ion secondary battery capable of suppressing the influence of heat generation can be provided.

Claims

1. An electrode for a lithium-ion secondary battery, characterized in that: The electrode for a lithium-ion secondary battery has: A metal foil, A conductive layer formed on at least a part of the metal foil, and An active material layer formed on at least a part of the surface of the conductive layer on the side opposite to the metal foil side, The conductive layer contains conductive particles and an insulating resin, The active material layer contains a first active material layer and a second active material layer, The first active material layer and the second active material layer are laminated in such a way that the first active material layer is on the side closer to the conductive layer, The second active material layer has a higher porosity than the first active material layer, When the porosity of the second active material layer in the active material layer is set as C and the porosity of the first active material layer is set as D, 1.1 ≤ C / D ≤ 3.

6.

2. The electrode for a lithium-ion secondary battery according to claim 1, characterized in that: When the occupied area per unit area of the conductive particles when observing the conductive layer in the thickness direction is set as A and the occupied area per unit area of the insulating resin is set as B, 0.11 ≤ A / B ≤ 1.

0.

3. The electrode for a lithium-ion secondary battery according to claim 1 or 2, characterized in that: When the porosity of the second active material layer in the active material layer is set as C and the porosity of the first active material layer is set as D, 1.2 ≤ C / D ≤ 3.

5.

4. A lithium-ion secondary battery using the electrode for a lithium-ion secondary battery according to any one of claims 1 to 3.

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