JP2015072758A - Electrode for lithium ion secondary battery, method for manufacturing the same, and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery having high reliability, an electrode capable of constituting the lithium ion secondary battery, and a method for manufacturing the electrode.SOLUTION: An electrode of the present invention includes a body part and a small width part projecting from the body part in plan view and having a smaller width than the body part. An electrode mixture layer containing an active material is formed on one side or both sides of a collector, at the body part and a place including an interface between the small width part and the body part. A surface of the electrode mixture layer and a region from an end of a formation part of the electrode mixture layer to a length at least same with the thickness of the electrode mixture layer at the small width part are covered with a porous insulating layer, and the collector is exposed at at least a part of a place in the small width part, the place being not covered with the insulating layer. In a lithium ion secondary battery of the present invention, at least one of a positive electrode and a negative electrode is the electrode of the present invention.

Description

  The present invention relates to a lithium ion secondary battery having high reliability, an electrode that can constitute the lithium ion secondary battery, and a method for manufacturing the electrode.

  In general, electrodes (positive and negative electrodes) of a lithium ion secondary battery are formed by forming an electrode mixture layer containing an active material on the surface of a metal foil or the like as a current collector. In some cases, a part of the current collector is exposed without forming an electrode mixture layer and used as a current collecting tab for electrical connection with a terminal in the battery (eg, Patent Document 1).

JP 2011-1113827 A

  As described above, an electrode of a type in which a part of a current collector is exposed and used as a current collecting tab is formed by, for example, forming an electrode mixture layer on a part of a metal foil serving as a current collector, and It may be manufactured through a process of punching out so as to include a mixture layer forming part and an exposed part of a current collector.

  However, since the thickness is different between the electrode mixture layer forming portion and the exposed portion of the current collector, the exposed portion of the current collector is less likely to be stressed at the time of punching. Burr is likely to occur at the end near the boundary. When a lithium ion secondary battery is configured using such an electrode with burrs remaining, the burrs come into contact with the counter electrode and cause a decrease in the withstand voltage performance, which causes a decrease in battery reliability.

  Therefore, in a lithium ion secondary battery using an electrode having a form that tends to generate burrs as described above in the manufacturing process, development of a technique that avoids the problem caused by burrs and increases the reliability thereof is required.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a lithium ion secondary battery having high reliability, an electrode that can constitute the lithium ion secondary battery, and a method for manufacturing the same. It is in.

  An electrode for a lithium ion secondary battery of the present invention that has achieved the above object has a main body part and a narrow part that is narrower than the main body part and protrudes from the main body part in plan view. In addition, an electrode mixture layer containing an active material is formed on one side or both sides of a current collector at a position including the boundary between the main body portion and the narrow body portion with the main body portion. The surface of the agent layer and the region of the narrow portion from the end of the electrode mixture layer forming portion to at least the same length as the thickness of the electrode mixture layer are covered with a porous insulating layer The current collector is exposed at least at a part of the narrow portion that is not covered with the insulating layer.

  The electrode for a lithium ion secondary battery of the present invention includes a step of forming an electrode mixture layer containing an active material on a part of the surface of a current collector, the surface of the electrode mixture layer, and the electrode mixture layer Of the exposed portion of the current collector that is not formed, a region from the end of the electrode mixture layer forming portion to at least the same length as the thickness of the electrode mixture layer is covered with a porous insulating layer. The electrode laminate and the step of punching out the electrode laminate according to the method for producing an electrode for a lithium ion secondary battery of the present invention.

  The lithium ion secondary battery of the present invention has a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, and at least one of the positive electrode and the negative electrode is an electrode for a lithium ion secondary battery of the present invention. It is characterized by being.

  ADVANTAGE OF THE INVENTION According to this invention, the lithium ion secondary battery which has high reliability, the electrode which can comprise the said lithium ion secondary battery, and its manufacturing method can be provided.

It is a top view which represents typically an example of the electrode for lithium ion secondary batteries of this invention. It is a principal part enlarged view of the AA line cross section of FIG. It is a top view which represents typically an example of the lithium ion secondary battery of this invention. FIG. 4 is a sectional view taken along line BB in FIG. 3. 3 is a discharge curve obtained by evaluating discharge characteristics of lithium ion secondary batteries of Example 1 and Comparative Example 2. FIG.

  FIG. 1 is a plan view schematically showing an example of an electrode for a lithium ion secondary battery of the present invention, and FIG. 2 is an enlarged view of a main part of the cross section taken along the line AA of FIG.

  The electrode 10 for lithium ion secondary batteries has the main-body part 10a and the narrow part 10b narrower than the main-body part 10a which protruded from the main-body part 10a by planar view. Moreover, the electrode mixture layer 11 containing an active material is formed on both surfaces of the current collector 12 at locations including the boundary between the main body portion 10a and the main body portion 10b of the narrow width portion 10b.

  In addition, the narrow portion 10b is used as a current collecting tab for electrical connection with a terminal in the lithium ion secondary battery, so that at least a part of the current collector 12 is exposed. Yes.

  The surface of the electrode mixture layer 11 and the region of the narrow portion from the end of the formation portion of the electrode mixture layer 11 to at least the same length as the thickness of the electrode mixture layer 11 are a porous insulating layer 13 is covered. That is, in the main body portion 10 a, the surface of the electrode mixture layer 11 is covered with the insulating layer 13. Moreover, in the narrow part 10b, from the location in which the electrode mixture layer 11 is formed and its end (the part indicated by the dotted line in FIG. 1), at least the same length as the thickness of the electrode mixture layer 11 A region (a region up to a position where the length of a in FIG. 1 and FIG. 2 satisfies a ≧ b when the thickness of the electrode mixture layer 11 is b) is covered with the porous insulating layer 13.

  Since the insulating layer 13 is present on the surface of the electrode mixture layer, it partitions the counter electrode (counter electrode mixture layer) in the same manner as a separator used in a normal lithium ion secondary battery. Functions as a separator.

  In ordinary lithium ion secondary batteries, a microporous film made of a thermoplastic resin that is easily heat-shrinkable is generally used for the separator because of its manufacturing method. When the temperature rises, there is a possibility that a short circuit occurs in which the separator is thermally contracted and the positive electrode and the negative electrode are in direct contact with each other. However, in the lithium ion secondary battery electrode of the present invention, the surface of the electrode mixture layer is covered with an insulating layer, and the electrode mixture layer and the insulating layer are in close contact. Even if the internal temperature of the ion secondary battery becomes high and the normal separator heat-shrinks, the insulating layer that does not easily heat-shrink makes the electrode mixture layer and the counter electrode mixture layer in direct contact. Can be prevented. Therefore, if it is the lithium ion secondary battery of this invention, the lithium ion secondary battery excellent in safety | security can be comprised.

  As shown in FIG. 1, when manufacturing an electrode having a shape having a wide main body portion and a narrower width portion that is narrower and mainly used for a current collecting tab, A method of forming an electrode mixture layer on one side or both sides of a metal foil to be punched into a predetermined shape is generally employed. In this case, for the reasons described above, the shoulder at the boundary between the main body portion and the narrow portion is used. In the portion corresponding to the portion (portion indicated by a dotted circle in FIG. 1), burrs are likely to occur on the current collector. In particular, as shown in FIG. 1, when the shoulder has a curved shape such as an R shape, the occurrence of burrs becomes more prominent.

  It is clear from the examination of the present inventors that the burr is likely to occur in a region from the end of the electrode mixture layer forming portion to a length similar to the thickness of the electrode mixture layer. Yes. Therefore, in the lithium ion secondary battery of the present invention, the insulating layer is provided not only on the surface of the electrode mixture layer but also on the portion where burrs are likely to occur when the electrode is punched. As a result, even if burrs are generated at the location in the electrode punching process, the presence of the insulating layer allows the distance from the counter electrode to be maintained to some extent, so that contact between the burrs and the counter electrode can be suppressed. In addition, since the insulating layer absorbs the thickness difference between the electrode mixture layer forming part and the exposed part of the current collector, burrs themselves are hardly generated. Therefore, if it is the electrode for lithium ion secondary batteries of this invention, the reliable lithium ion secondary battery which can suppress the fall of the withstand voltage performance which may arise by the said burr | flash, for example can be comprised. .

  The insulating layer according to the electrode for a lithium ion secondary battery of the present invention is porous, whereby high lithium ion permeability can be secured and the charge / discharge reaction of the lithium ion secondary battery can be favorably advanced.

  The insulating layer preferably contains an inorganic filler. An insulating layer containing an inorganic filler can be made porous, can ensure high lithium ion permeability, and can be an insulating layer that is less susceptible to deterioration such as heat shrinkage even at high temperatures. .

  As the inorganic filler for the insulating layer, the heat resistant temperature is 150 ° C. or higher, it is stable against the non-aqueous electrolyte of the lithium ion secondary battery, and is moreover not easily oxidized or reduced in the operating voltage range of the lithium ion secondary battery. Those chemically stable are preferred. As used herein, “heat-resistant temperature is 150 ° C. or higher” means that deformation such as softening is not observed at least at 150 ° C.

  The inorganic filler is preferably fine particles in view of dispersion and the like, and alumina, silica and boehmite are preferred. Alumina, silica, and boehmite have high oxidation resistance, and the particle size and shape can be adjusted to desired numerical values, so that it is easy to accurately control the porosity of the insulating layer. As the inorganic filler, for example, those exemplified above may be used alone or in combination of two or more.

  There is no restriction | limiting in particular about the shape of the inorganic filler which concerns on an insulating layer, The thing of various shapes, such as substantially spherical shape (a true spherical shape is included), a substantially ellipsoid shape (including an ellipsoid shape), and plate shape, can be used.

  Moreover, since the permeability | transmittance of ion will fall if the average particle diameter of the inorganic filler which concerns on an insulating layer is too small, it is preferable that it is 0.3 micrometer or more, and it is more preferable that it is 0.5 micrometer or more. Moreover, since an electrical property will deteriorate easily when an inorganic filler is too large, it is preferable that the average particle diameter is 5 micrometers or less, and it is more preferable that it is 2 micrometers or less.

The average particle diameter of the inorganic filler referred to in this specification is a volume-based integration measured by using a laser scattering particle size distribution meter (for example, “LA-920” manufactured by Horiba, Ltd.) and dispersing the negative electrode active material in a medium that does not dissolve. It is the particle size (D _50% ) at 50% in the fraction.

  The insulating layer can be formed, for example, by binding inorganic fillers with a binder. This binder also contributes to adhesion between the insulating layer, the electrode mixture layer, and the current collector.

  Specific examples of the binder include ethylene-vinyl acetate copolymers (EVA, those having a structural unit derived from vinyl acetate of 20 to 35 mol%), ethylene-acrylic acid copolymers such as ethylene-ethyl acrylate copolymers, Fluorine rubber, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), cross-linked acrylic resin, polyurethane, epoxy resin, etc. In particular, a heat-resistant binder having a heat-resistant temperature of 150 ° C. or higher is preferably used. As the binder, those exemplified above may be used alone or in combination of two or more.

  In the case of the insulating layer formed by binding the inorganic filler with the binder, the content of the inorganic filler in the insulating layer is 50 in the total volume of the constituent components of the insulating layer (the total volume excluding the voids). The volume is preferably at least volume%, more preferably at least 70 volume%, further preferably at least 80 volume%, particularly preferably at least 90 volume%. By making the inorganic filler in the insulating layer high as described above, even when the battery using the lithium ion secondary battery electrode of the present invention becomes high temperature, direct contact between the electrode and the counter electrode The occurrence of a short circuit due to can be suppressed better.

  However, if the amount of the inorganic filler in the insulating layer is too large, the amount of the binder will decrease, and the shape stability of the insulating layer will decrease, or the adhesion between the insulating layer and the electrode mixture layer will decrease. There is a risk of doing. Therefore, in the case of the insulating layer formed by binding the inorganic filler with the binder, the content of the inorganic filler in the insulating layer is preferably 95% by mass or less in the total volume of the constituent components of the insulating layer.

  In the case of the insulating layer formed by fixing the inorganic filler with the binder, the binder content is preferably 5% by volume or more in the total volume of the constituent components of the insulating layer, and 50% by volume. Preferably, it is preferably 30% by volume or less, more preferably 80% by volume or less, and particularly preferably 10% by volume or less.

  Further, the insulating layer is formed by irradiating an energy beam to an oligomer that can be polymerized by irradiation with an energy beam, and is composed of a resin [hereinafter referred to as “resin (A)”) having a crosslinked structure at least partially. You can also

  In the insulating layer containing the resin (A), since the resin (A) has a cross-linked structure, even when the temperature in the battery becomes high, deformation due to shrinkage or melting of the resin (A) hardly occurs. Since the shape is maintained well, occurrence of a short circuit between the electrode and the counter electrode is suppressed.

  The resin (A) preferably has a glass transition temperature (Tg) higher than 0 ° C, more preferably 10 ° C or higher, preferably lower than 80 ° C, and 60 ° C or lower. More preferred. If it is resin (A) which has such Tg, it will become possible to form a favorable void | hole in an insulating layer, and the lithium ion permeability | transmittance of an insulating layer can be made favorable. That is, if the Tg of the resin (A) is too low, the pores are easily filled, and it may be difficult to adjust the lithium ion permeability of the insulating layer. Also, if the Tg of the resin (A) is too high, curing shrinkage occurs during the formation of the insulating layer, making it difficult to form good pores, and it may be difficult to adjust the lithium ion permeability of the insulating layer. is there.

The Tg of the resin (A) in the present specification is obtained by applying an insulating layer forming composition (II) described later on a polytetrafluoroethylene sheet, and irradiating ultraviolet rays having a wavelength of 365 nm at an illuminance of 1000 mW / cm ² for 10 seconds. Thereafter, drying is performed at 60 ° C. for 1 hour to form a porous film (insulating layer) containing a resin (A) having a thickness of 20 μm. The porous film is subjected to a differential scanning calorific value in accordance with JISK 7121. It is a value measured using a meter (DSC).

  The resin (A) is obtained by irradiating an energy beam to an oligomer that can be polymerized by energy beam irradiation to polymerize the oligomer. By forming the resin (A) by polymerization of the oligomer, it is possible to form an insulating layer that is highly flexible, for example, it is difficult to peel off when a predetermined portion of the electrode is covered, and the resin (A) It becomes easy to adjust Tg to the above value.

  In forming the resin (A), it is preferable to use a monomer that can be polymerized by irradiation with energy rays together with the oligomer.

  As will be described in detail later, the separator containing the resin (A) is prepared as an insulating layer forming composition containing an oligomer or the like for forming the resin (A) and a solvent, and this is applied to a predetermined portion of the electrode. It is preferable to produce it through a process of forming a resin (A) by irradiating the coating with an energy ray to form a coating film. Here, by adding the monomer together with the oligomer to the composition for forming an insulating layer, it becomes easy to adjust the viscosity of the composition for forming an insulating layer, and the coating property to the electrode is improved, so that the insulating layer has better properties. Can be obtained. Moreover, since the control of the crosslinking density of the resin (A) is facilitated by using the monomer, the adjustment of the Tg of the resin (A) becomes easier.

  Specific examples of the resin (A) include, for example, acrylic resin monomers [alkyl (meth) acrylates such as methyl methacrylate and methyl acrylate and derivatives thereof) and oligomers thereof, and an acrylic resin formed from a crosslinking agent; urethane acrylate And a crosslinking resin formed from an epoxy acrylate and a crosslinking agent; a crosslinking resin formed from a polyester acrylate and a crosslinking agent; and the like. In any of the above resins, the cross-linking agent may be tripropylene glycol diacrylate, 1,6-hexanediol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, dioxane glycol diacrylate, tricyclodecane dimethanol dimer. Divalent or polyvalent, such as acrylate, dimethylol tricyclodecane diacrylate, ethylene oxide modified trimethylolpropane triacrylate, dipentaerythritol pentaacrylate, caprolactone modified dipentaerythritol hexaacrylate, ε-caprolactone modified dipentaerythritol hexaacrylate Acrylic monomer (bifunctional acrylate, trifunctional acrylate, tetrafunctional acrylate, 5-functional acrylate) Rate, etc. hexafunctional acrylate) can be used.

  Therefore, when the resin (A) is the acrylic resin, an oligomer of the acrylic resin monomer exemplified above can be used as an oligomer that can be polymerized by irradiation with energy rays (hereinafter simply referred to as “oligomer”). As the monomer that can be polymerized by irradiation with energy rays (hereinafter simply referred to as “monomer”), the acrylic resin monomers exemplified above and a crosslinking agent can be used.

  Furthermore, when the resin (A) is a cross-linked resin formed from the urethane acrylate and a cross-linking agent, urethane acrylate can be used for the oligomer, and the cross-linking agent exemplified above can be used for the monomer.

  On the other hand, when the resin (A) is a cross-linked resin formed from the above-mentioned epoxy acrylate and a cross-linking agent, an epoxy acrylate can be used for the oligomer, and the cross-linking agent exemplified above can be used for the monomer.

  Furthermore, when the resin (A) is a cross-linked resin formed from the polyester acrylate and a cross-linking agent, polyester acrylate can be used as the oligomer, and the cross-linking agents exemplified above can be used as the monomer.

  In synthesizing the resin (A), two or more of the urethane acrylate, the epoxy acrylate, and the polyester acrylate may be used as the oligomer, and the crosslinking agent (monomer) may be used as the oligomer. Two or more of the bifunctional acrylate, the trifunctional acrylate, the tetrafunctional acrylate, the pentafunctional acrylate, and the hexafunctional acrylate may be used.

  Further, the resin (A) includes a crosslinked resin derived from an unsaturated polyester resin formed from a mixture of an ester composition produced by condensation polymerization of a divalent or polyvalent alcohol and a dicarboxylic acid and a styrene monomer; Various polyurethane resins produced by the reaction of isocyanate and polyol can also be used.

  Therefore, when the resin (A) is a crosslinked resin derived from the unsaturated polyester resin, the ester composition can be used as the oligomer, and the styrene monomer can be used as the monomer.

  When the resin (A) is various polyurethane resins produced by reaction of polyisocyanate and polyol, examples of the polyisocyanate include hexamethylene diisocyanate, phenylene diisocyanate, toluene diisocyanate (TDI), and 4.4'-diphenylmethane diisocyanate. (MDI), isophorone diisocyanate (IPDI), bis- (4-isocyanatocyclohexyl) methane, etc. are mentioned, and examples of the polyol include polyether polyol, polycarbonate polyol, and polyester polyol.

  Therefore, when resin (A) is various polyurethane resins produced | generated by reaction of polyisocyanate and a polyol, the said illustrated polyol can be used for an oligomer and the said illustrated polyisocyanate can be used for a monomer.

  In forming each of the exemplified resins (A), monofunctional monomers such as isobornyl acrylate, methoxypolyethylene glycol acrylate, and phenoxypolyethylene glycol acrylate can be used in combination. Therefore, when the resin (A) has a structural portion derived from these monofunctional monomers, the above-described monofunctional monomers can be used as monomers together with the exemplified oligomers and other monomers. it can.

  However, the monofunctional monomer tends to remain as an unreacted substance in the formed resin (A), and the unreacted substance remaining in the resin (A) elutes into the non-aqueous electrolyte of the lithium ion secondary battery. There is a risk of inhibiting the battery reaction. Therefore, the oligomer and monomer used for forming the resin (A) are preferably bifunctional or higher. Moreover, it is preferable that the oligomer and monomer used for formation of resin (A) are 6 functional or less.

  In the case of using an oligomer and a monomer in combination for forming the resin (A), the ratio of the oligomer to the monomer used is 20:80 to 95: 5 in terms of mass ratio from the viewpoint of facilitating the adjustment of Tg. It is preferable to set it as 65: 35-90: 10. That is, the resin (A) formed using the oligomer and the monomer preferably has a mass ratio of 20:80 to 95: 5 between the unit derived from the oligomer and the unit derived from the monomer. 65:35 to 90:10 is more preferable.

  The insulating layer containing the resin (A) can be formed of only the resin (A), but may contain an inorganic filler (the inorganic filler illustrated above) together with the resin (A). By containing an inorganic filler, the strength and dimensional stability of the insulating layer can be further increased.

In the case where the inorganic filler in the insulating layer containing a resin (A) also is contained, the volume _{V A} of the resin (A), the ratio _V A / _{V B} the volume _{V B} of the inorganic filler is 0.6 or more It is preferable that the number is 3 or more. When the V _A / V _B is in the above-mentioned value, for example, a wound electrode body (particularly a square shape) can be obtained by using the electrode for a lithium ion secondary battery of the present invention by the action of the resin (A) rich in flexibility. Even when it is bent as in the case of a wound electrode body having a flat cross section used for a battery or the like, the occurrence of defects such as cracks in the insulating layer can be suppressed more favorably.

When the insulating layer containing the resin (A) also contains an inorganic filler, the V _A / V _B is preferably 9 or less, and more preferably 8 or less. When V _A / V _B is in the above value, the effect of improving the strength and dimensional stability of the insulating layer due to the inclusion of the inorganic filler can be exhibited better.

  The thickness of the insulating layer is preferably 0.5 μm or more, and more preferably 1 μm or more, from the viewpoint of better ensuring the above-described effect by forming it. However, if the insulating layer is too thick, the proportion of components not involved in the battery reaction in the lithium ion secondary battery increases, which may cause a reduction in the energy density of the battery. Therefore, the thickness of the insulating layer is preferably 10 μm or less, and more preferably 6 μm or less.

  If the insulating layer is porous, the porosity (the porosity determined from the apparent volume calculated from the thickness and area of the insulating layer and the density of each component constituting the insulating layer) Is preferably 20 to 80%.

  In the narrow portion, the insulating layer has at least the same length as the thickness of the electrode mixture layer from the end portion of the electrode mixture layer forming portion in addition to the electrode mixture layer forming portion (surface of the electrode mixture layer). [In other words, the length (μm) of a in FIG. 1 and FIG. 2 is set to 1 or more times the thickness (μm) of the electrode mixture layer], but a in FIG. 1 and FIG. The length (μm) is preferably at least 3 times the thickness (μm) of the electrode mixture layer. In this case, the reliability of the lithium ion secondary battery using the electrode can be further increased. However, since the exposed part of the current collector plays a role as a current collecting tab of the electrode for the lithium ion secondary battery, the narrow part is insulated from the exposed part of the current collector in the narrow part. It is not preferable that the region covered with the layer is too large. Specifically, the length (μm) in FIG. 1 and FIG. 2 is 30 times or less the thickness (μm) of the electrode mixture layer. Is preferred.

  The electrode for lithium ion secondary batteries of this invention is used for the positive electrode or negative electrode of a lithium ion secondary battery.

  When the electrode for a lithium ion secondary battery of the present invention is a positive electrode, the electrode mixture layer (positive electrode mixture layer) contains a conductive additive, a binder and the like together with the positive electrode active material.

As the positive electrode active material, a conventionally known positive electrode active material for a lithium ion secondary battery, for example, an active material capable of inserting and extracting lithium ions is used. As a specific example of such a positive electrode active material, for example, a layered structure represented by Li _{1 + x} MO ₂ (−0.1 <x <0.1, M: Co, Ni, Mn, Al, Mg, etc.) Lithium-containing transition metal oxide, LiMn ₂ O ₄ and spinel-structured lithium manganese oxide obtained by substituting some of its elements with other elements, LiMPO ₄ (M: Co, Ni, Mn, Fe, etc.) Type compounds. Specific examples of the lithium-containing transition metal oxide having a layered structure include LiCoO ₂ and LiNi _1-x Co _xy Al _y O ₂ (0.1 ≦ x ≦ 0.3, 0.01 ≦ y ≦ 0. 2) and other oxides containing at least Co, Ni and Mn (LiMn _1/3 Ni _1/3 Co _1/3 O ₂ , LiMn _5/12 Ni _5/12 Co _1/6 O ₂ , LiNi _{3 / 5} Mn _1/5 Co _1/5 O ₂ etc.).

  Examples of the conductive additive related to the positive electrode mixture layer include graphite (graphite carbon material) such as natural graphite (flaky graphite, etc.) and artificial graphite; acetylene black, ketjen black, channel black, furnace black, lamp black. And carbon materials such as carbon black, carbon black, and the like. In addition, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), or the like can be used for the binder related to the positive electrode mixture layer.

  The thickness of the positive electrode mixture layer is preferably, for example, 10 to 100 μm per one side of the current collector. Moreover, as a composition of a positive mix layer, it is preferable that the quantity of a positive electrode active material is 60-95 mass%, for example, it is preferable that the quantity of a binder is 1-15 mass%, and the quantity of a conductive support agent. Is preferably 3 to 20% by mass.

  As the current collector when the electrode for the lithium ion secondary battery of the present invention is a positive electrode, the same current collector as that used for the positive electrode of a conventionally known lithium ion secondary battery can be used. An aluminum foil having a thickness of 10 to 30 μm is preferable.

  When the electrode for a lithium ion secondary battery of the present invention is a negative electrode, the electrode mixture layer (negative electrode mixture layer) contains a binder together with the negative electrode active material, and, if necessary, a conductive aid or the like. Contains.

  Examples of the negative electrode active material include graphite materials such as natural graphite (flaky graphite), artificial graphite, and expanded graphite; graphitizable carbonaceous materials such as coke obtained by calcining pitch; furfuryl alcohol resin ( Carbon materials such as non-graphitizable carbonaceous materials such as amorphous carbon obtained by low-temperature firing of PFA), polyparaphenylene (PPP), and phenol resins. In addition to the carbon material, lithium or a lithium-containing compound can also be used as the negative electrode active material. Examples of the lithium-containing compound include lithium alloys such as Li—Al, and alloys containing elements that can be alloyed with lithium such as Si and Sn. Furthermore, oxide-based materials such as Sn oxide and Si oxide can also be used.

  As the binder and the conductive auxiliary agent related to the negative electrode mixture layer, the same materials as those exemplified above as the binder and the conductive auxiliary agent related to the positive electrode mixture layer can be used.

  The thickness of the negative electrode mixture layer is preferably 10 to 100 μm per side of the current collector per side of the current collector. Moreover, as a composition of a negative mix layer, it is preferable that the quantity of a negative electrode active material is 80-95 mass%, for example, it is preferable that the quantity of a binder is 1-20 mass%, and uses a conductive support agent. When it does, it is preferable that the quantity is 1-10 mass%.

  For the current collector when the electrode for the lithium ion secondary battery of the present invention is a negative electrode, copper or nickel foil, punching metal, net, expanded metal, or the like can be used, but copper foil is usually used. In the negative electrode current collector, when the thickness of the entire negative electrode is reduced in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 μm, and the lower limit is preferably 5 μm.

  In the electrode for a lithium ion secondary battery of the present invention, in the narrow portion, if the portion for forming the electrode mixture layer is too large, the function as a current collecting tab may be lowered. The region where the electrode mixture layer is provided preferably has a distance from the boundary with the main body (length in the vertical direction in FIG. 1; the same shall apply hereinafter) of 2.5 mm or less. Moreover, it is preferable that the area | region which provides an electrode mixture layer in a narrow part has the distance from the boundary with a main-body part being 0.1 mm or more.

  The electrode for a lithium ion secondary battery of the present invention includes a step of forming an electrode mixture layer (electrode mixture layer forming step) on a part of the surface of the current collector, a surface of the electrode mixture layer, and the electrode. Of the exposed portion of the current collector where no mixture layer is formed, an insulating layer covers the region from the end of the electrode mixture layer forming portion to at least the same length as the thickness of the electrode mixture layer. Thus, it can be produced by the production method of the present invention comprising a step of forming an electrode laminate (electrode laminate forming step) and a step of punching out the electrode laminate (punching step).

  In the electrode mixture layer forming step, for example, a paste in which an active material, a binder, and further a conductive assistant as necessary are dispersed in an organic solvent such as N-methyl-2-pyrrolidone (NMP) or a solvent such as water. Or a slurry-like composition for forming an electrode mixture layer (however, the binder may be dissolved in a solvent), and this is applied to a predetermined portion (a main body portion and a narrow portion) on one or both sides of the current collector Are applied to a portion that is supposed to be a portion including the boundary with the main body portion), and after drying, a calendar treatment is performed as necessary to form an electrode mixture layer.

  In the electrode laminate forming step, an insulating layer is formed at a predetermined position of an integrated product in which the electrode mixture layer is formed on a part of the surface of the current collector to obtain an electrode laminate.

  In the case of an insulating layer constituted by binding an inorganic filler with the above-mentioned binder, an insulating layer forming composition (I) containing an inorganic filler and a binder is prepared, and this is applied to the surface of the current collector. A laminated body for electrodes can be obtained by forming an insulating layer by applying to a predetermined portion of an integrated product having an electrode mixture layer formed on the part and drying.

  The insulating layer forming composition (I) contains an inorganic filler, a binder, and the like, and these are dispersed in a solvent. The binder can be dissolved in a solvent. The solvent used in the insulating layer forming composition may be any solvent that can uniformly disperse the inorganic filler and the like, and can dissolve or disperse the binder uniformly. For example, aromatic hydrocarbons such as toluene, tetrahydrofuran, etc. Common organic solvents, such as the above furans, ketones such as methyl ethyl ketone and methyl isobutyl ketone, are preferably used. In addition, for the purpose of controlling the interfacial tension, alcohols (ethylene glycol, propylene glycol, etc.) or various propylene oxide glycol ethers such as monomethyl acetate may be appropriately added to these solvents. In addition, when the binder is water-soluble or used as an emulsion, water may be used as a solvent. In this case, an alcohol (methyl alcohol, ethyl alcohol, isopropyl alcohol, ethylene glycol, etc.) is added as appropriate to the interface. The tension can also be controlled.

  The composition for forming an insulating layer (I) preferably has a solid content including an inorganic filler and a binder, for example, 10 to 80% by mass.

  In the case of the insulating layer containing the resin (A), an insulating layer forming composition (II) containing at least an oligomer and a solvent is prepared, and this is formed on a part of the surface of the current collector. The coating film formed by applying to a predetermined portion of the integrated product in which the agent layer is formed is irradiated with energy rays to form a resin (A) having a crosslinked structure, and the composition for forming an insulating layer after irradiation with energy rays ( The laminated body for electrodes can be obtained by forming the insulating layer through the step of drying the coating film of II) to form holes.

  The composition (II) for forming the insulating layer uses a composition (slurry or the like) containing an oligomer, a monomer, a polymerization initiator, and further containing an inorganic filler as necessary and dispersed in a solvent. .

  Examples of the solvent that can be used as the solvent for the insulating layer forming composition (II) include the same solvents as those exemplified above as those that can be used for the insulating layer forming composition (I). In addition, the components for controlling the interfacial tension exemplified above as being usable for the insulating layer forming composition (I) may be added to these solvents.

  The solvent includes a solvent (a) having a relatively high affinity for the resin (A) and a solvent having a lower affinity for the resin (A) than the solvent (a) and a higher boiling point than the solvent (a). It is preferable to use (b) in combination. The solvent of the insulating layer forming composition (II) evaporates by drying the coating film of the insulating layer forming composition after energy irradiation, and contributes to the formation of pores. The solvent (a) and the solvent (b) When used together, the pore formation at the time of drying proceeds better, and a large number of highly uniform pores can be formed, so that an insulating layer with more stable lithium ion permeability can be formed throughout. It becomes.

  The composition for forming an insulating layer (II) usually contains an energy ray sensitive polymerization initiator. Specific examples of the polymerization initiator include, for example, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpropiophenone, and the like. Can be mentioned. It is preferable that the usage-amount of a polymerization initiator shall be 1-10 mass parts with respect to 100 mass parts of total amounts (when using only an oligomer) of an oligomer and a monomer.

  In the insulating layer forming composition (II), it is preferable that the solid content including oligomers, monomers, polymerization initiators, and inorganic fillers used as necessary is, for example, 10 to 50% by mass. .

  When applying the insulating layer forming composition (II), a known application method can be employed.

  Next, the coating film formed by applying the insulating layer forming composition (II) is irradiated with energy rays to form a resin (A) having a crosslinked structure.

  Examples of energy rays applied to the coating film of the composition for forming an insulating layer (II) include visible light, ultraviolet light, radiation, and electron beam. However, since safety is higher, visible light or ultraviolet light is used. More preferably, it is used.

Upon irradiation with energy rays, it is preferable to adjust the wavelength, irradiation intensity, irradiation time, and the like as appropriate so that the resin (A) can be formed satisfactorily. As a specific example, for example, the wavelength of the energy beam can be 320 to 390 nm and the irradiation intensity can be 623 to 1081 mJ / cm ² . However, the energy beam irradiation conditions are not limited to the above-described conditions.

  Next, the coating film of the composition for forming an insulating layer (II) after irradiation with energy rays is dried to remove the solvent, thereby forming holes. The drying conditions (temperature, time, drying method) may be appropriately selected according to the type of solvent used in the insulating layer forming composition (II) so that it can be removed satisfactorily. Specific examples include, for example, a drying temperature of 20 to 80 ° C., a drying time of 30 minutes to 24 hours, and a drying method using a thermostatic bath, a dryer, etc. in addition to air drying. The method can be adopted.

  In addition, the above-mentioned energy is obtained by adding a material that can be dissolved in a specific solvent (a solvent other than the solvent used in the insulating layer forming composition (II)) to the insulating layer forming composition (II). The resin (A) is contained by a method in which the resin (A) is formed by irradiation and further dried if necessary, and then the material is extracted using the specific solvent to form pores. A porous insulating layer can also be formed.

  Examples of materials that can be dissolved in the specific solvent include polyolefin, polyurethane, and acrylic resin. These materials are preferably used in the form of particles, for example, but the size and amount of use can be adjusted according to the porosity and hole diameter required for the insulating layer. In general, the average particle size of the material (average particle size measured by the same method as the average particle size of the inorganic filler) is preferably 0.1 to 20 μm, and the amount used is for forming an insulating layer. The total solid content in the composition (II) is preferably 1 to 10% by mass.

  In the electrode laminate forming step, the electrode laminate obtained by forming the insulating layer as described above is formed in such a manner that the electrode mixture layer is formed on the body portion and a part of the narrow portion in the next punching step. An electrode for a lithium ion secondary battery is formed by punching into a shape in which an insulating layer is formed at a predetermined portion of the electrode mixture layer and the narrow portion, and the exposed portion of the current collector remains in the narrow portion. Get.

  A known method can be adopted as the punching means in this punching step.

  The lithium ion secondary battery of the present invention has a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, and the lithium ion secondary battery electrode of the present invention is used for at least one of the positive electrode and the negative electrode. In addition, there is no restriction | limiting in particular about another structure and structure, The various structure and structure employ | adopted by the lithium ion secondary battery known conventionally are applicable.

  As described above, in the lithium ion secondary battery of the present invention, the electrode for the lithium ion secondary battery of the present invention may be used only for the positive electrode, and the electrode for the lithium ion secondary battery of the present invention is used only for the negative electrode. Alternatively, the lithium ion secondary battery electrode of the present invention may be used for both the positive electrode and the negative electrode.

  In addition, when using the electrode for lithium ion secondary batteries of this invention only for a positive electrode, the negative electrode of the same structure as the electrode for lithium ion secondary batteries of this invention is used for a negative electrode except having no insulating layer. be able to. Moreover, when using the electrode for lithium ion secondary batteries of this invention only for a negative electrode, the positive electrode of the same structure as the electrode for lithium ion secondary batteries of this invention is used for a positive electrode except not having an insulating layer. be able to.

  The separator according to the lithium ion secondary battery of the present invention has a property (that is, a shutdown function) that the pores are blocked at 80 ° C. or higher (more preferably 100 ° C. or higher) and 170 ° C. or lower (more preferably 150 ° C. or lower). It is preferable that a separator used in a normal lithium ion secondary battery, for example, a microporous membrane made of polyolefin such as polyethylene (PE) or polypropylene (PP) can be used. The microporous film constituting the separator may be, for example, one using only PE or one using PP, or a laminate of a PE microporous film and a PP microporous film. There may be. The thickness of the separator is preferably 10 to 30 μm, for example.

  In the lithium ion secondary battery of the present invention, the positive electrode and the negative electrode are composed of a laminated body (laminated electrode body) configured by overlapping with a separator, and a wound body (winding) in which the laminated body is wound in a spiral shape. As the rotating electrode body), it is used in the lithium ion secondary battery of the present invention.

  The electrode obtained through the punching process has a shape suitable for constituting a laminated electrode body, that is, a rectangular electrode having a small difference between a circle and a width and a length in plan view. For example, a wound electrode body Even in the band-shaped electrode for forming the electrode, the part of the current collector left as an exposed part for use in the current collecting tab is narrower than the body part in which the electrode mixture layer is formed by punching. It is also possible to use a shape (narrow portion), and in this case, the above-described problem due to burrs may occur. However, even in a lithium ion secondary battery using such a wound electrode body, by using the electrode for a lithium ion secondary battery of the present invention as at least one of a strip-shaped positive electrode and a strip-shaped negative electrode, It is possible to suppress the occurrence of problems due to burrs that may occur due to the above, and to ensure high reliability.

  In the case of a laminated electrode body, a method of laminating a plurality of positive electrodes and a plurality of negative electrodes via a plurality of separators can be employed. In addition to this, a plurality of positive electrodes are arranged at regular intervals on one side of a strip-shaped separator (lower separator), and a separator (upper separator) cut according to the shape of each positive electrode is formed on each positive electrode. Put the positive electrode on the lower separator after wrapping each positive electrode in the bag part by heat sealing the peripheral part of the upper separator (peripheral part of the part where the current collector tab of the positive electrode is not pulled out) It is also possible to form a laminated electrode body by arranging the negative electrode between the locations where the positive electrode is included in the bag-shaped part of the folded separator, or at the outermost part in the folded separator at the part not facing it can.

  In addition, a strip separator is used for the lower separator, and a strip separator is also used for the upper separator. A plurality of positive electrodes are arranged on one side of the lower separator at regular intervals. Put each of the separators in a bag shape by heat-sealing the lower separator and the upper separator in the vicinity of the peripheral edge of each positive electrode (near the peripheral edge of the portion where the current collecting tab of the positive electrode is not drawn). After the positive electrode is wrapped, the lower separator and the upper separator are not facing the positive electrode and are folded in a zigzag manner, and the negative electrode is formed between the portions of the folded separator containing the positive electrode in a bag-like part or at the outermost part. A laminated electrode body can also be formed by arranging the electrodes.

For the non-aqueous electrolyte according to the lithium ion secondary battery of the present invention, for example, a solution (non-aqueous electrolyte) in which a lithium salt is dissolved in an organic solvent can be used. The lithium salt is not particularly limited as long as it dissociates in a solvent to form Li ⁺ ions and hardly causes side reactions such as decomposition in a voltage range used as a battery. For example, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ and other inorganic lithium salts, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (n ≧ 2), LiN (RfOSO ₂ ) ₂ [where Rf is a fluoroalkyl group] and the like can be used. .

  The organic solvent used for the non-aqueous electrolyte is not particularly limited as long as it dissolves the lithium salt and does not cause a side reaction such as decomposition in a voltage range used as a battery. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; chain esters such as methyl propionate; cyclic esters such as γ-butyrolactone; dimethoxyethane; Chain ethers such as diethyl ether, 1,3-dioxolane, diglyme, triglyme and tetraglyme; cyclic ethers such as dioxane, tetrahydrofuran and 2-methyltetrahydrofuran; nitriles such as acetonitrile, propionitrile and methoxypropionitrile; ethylene Sulfites such as glycol sulfite; and the like. These may be used in combination of two or more. In order to obtain a battery with better characteristics, it is desirable to use a combination that can obtain high conductivity, such as a mixed solvent of ethylene carbonate and chain carbonate. In addition, for the purpose of improving safety such as improvement of charge / discharge cycle characteristics, high-temperature storage properties and prevention of overcharge, these non-aqueous electrolytes may be used in acid anhydrides, sulfonic acid esters, dinitriles, vinylene carbonates, 1,3- Additives (including these derivatives) such as propane sultone, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, and t-butylbenzene may be added as appropriate.

  The concentration of the lithium salt in the non-aqueous electrolyte is preferably 0.5 to 1.5 mol / l, and more preferably 0.9 to 1.25 mol / l.

  Moreover, you may use for the lithium ion secondary battery of this invention what added gelling agents, such as a well-known polymer, to the said nonaqueous electrolyte solution, and was made into the gel form (gel electrolyte).

  Examples of the form of the lithium ion secondary battery of the present invention include a cylindrical shape (such as a rectangular tube shape or a cylindrical shape) using a steel can or an aluminum can as an outer can. In addition, the lithium ion secondary battery of the present invention can be a soft package battery using a laminate film deposited with a metal as an outer package.

  The lithium ion secondary battery of the present invention can be used for various applications to which conventionally known lithium ion secondary batteries are applied.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
<Preparation of positive electrode>
LiCoO _{2 as} positive electrode active material: 100 parts by mass, NMP solution containing PVDF as binder at a concentration of 10% by mass: 20 parts by mass, artificial graphite as conductive aid: 1 part by mass and Ketjen Black: 1 The slurry was mixed with a mass part using a planetary mixer, and NMP was added to adjust the viscosity to prepare a positive electrode mixture-containing slurry.

  The positive electrode mixture-containing slurry is applied to both surfaces of an aluminum foil (positive electrode current collector) having a thickness of 15 μm, and then vacuum-dried at 120 ° C. for 12 hours to form a positive electrode mixture layer on both surfaces of the aluminum foil. Formed. When the positive electrode mixture layer was formed, a part of the aluminum foil was left to be an exposed portion. Thereafter, calendar treatment was performed to adjust the thickness and density of the positive electrode mixture layer. The thickness of the positive electrode mixture layer was 60 μm per one side of the current collector.

  Urethane acrylate as an oligomer ("EBECRYL 8405" manufactured by Daicel Cytex): 80 parts by mass, tripropylene glycol diacrylate as a monomer: 20 parts by mass, bis (2,4,6-trimethylbenzoyl) as a photopolymerization initiator -Phenylphosphine oxide: 2 parts by weight, boehmite as an inorganic filler (average particle size 1 μm): 300 parts by weight, and a volume ratio of 9: 1 of ethyl acetate as the solvent (a) and dodecane as the solvent (b) Mixed solvent: 5 parts by weight (mass basis) of φ1 mm zirconia beads was added to 600 parts by weight of the boehmite, stirred uniformly for 15 hours using a ball mill, and then filtered to prepare an insulating layer forming composition. .

This insulating layer forming composition was applied to the surface of the positive electrode mixture layer formed on both sides of the current collector and the exposed portion of the aluminum foil adjacent to the location where the positive electrode mixture layer was formed, dried, and then exposed to ultraviolet light. By synthesizing the resin (A) by irradiation, an insulating layer having a thickness of 4 μm was formed to obtain a laminate for positive electrode.

  The positive electrode laminate was punched into the shape shown in FIG. 1 to obtain a positive electrode. In the positive electrode obtained, the main body portion on which the positive electrode mixture layer was formed had a width (length in the horizontal direction in FIG. 1): 64.5 mm, a length: 110 mm, and a narrow portion had a width (width in FIG. 1). The length in the direction): 11 mm, the length: 10 mm, and the shoulder portion at the boundary between the main body portion and the narrow portion has an R shape with a radius of curvature of 2 mm. In the narrow portion, the positive electrode mixture layer exists from the boundary with the main body portion to the position of 500 μm upward in FIG. 1, and 80 μm from the end of the positive electrode mixture layer upward in FIG. 1. The insulating layer was also present on the current collector surface up to the position of, and the other portions were exposed portions of the current collector.

<Production of negative electrode>
Water is added to 97.5 parts by mass of natural graphite having a number average particle diameter of 10 μm as a negative electrode active material, 1.5 parts by mass of SBR as a binder, and 1 part by mass of CMC as a thickener. And mixed to prepare a negative electrode mixture-containing paste. This negative electrode mixture-containing paste was applied to both sides of a copper foil having a thickness of 8 μm, and then vacuum-dried at 120 ° C. for 12 hours to form negative electrode mixture layers on both sides of the copper foil. When the negative electrode mixture layer was formed, a part of the copper foil was left to be an exposed portion. Thereafter, calendering was performed to adjust the thickness and density of the negative electrode mixture layer, and then punched into the shape shown in FIG. 1 to obtain a negative electrode. In the obtained negative electrode, the main body portion on which the negative electrode mixture layer was formed had a width (length in the horizontal direction in FIG. 1): 66.5 mm, a length: 112 mm, and a narrow portion had a width (width in FIG. 1). The length in the direction): 11 mm, the length: 10 mm, and the shoulder portion at the boundary between the main body portion and the narrow portion has an R shape with a radius of curvature of 2 mm. Note that an insulating layer is not formed on the negative electrode.

<Formation of laminated electrode body>
While the negative electrode and the positive electrode are alternately placed on a belt-like separator made of a microporous membrane made of PE (thickness 16 μm, porosity 45%), it is folded in a zigzag shape, and the separator is cut at a predetermined location to obtain six positive electrodes A laminated electrode body having seven negative electrodes was obtained.

<Battery assembly>
The laminated electrode body is sandwiched between two aluminum laminate films (170 × 125 mm), three sides of both laminated films placed above and below the laminated electrode body are heat-sealed, and vacuum-dried at 60 ° C. for one day. After that, LiPF ₆ was dissolved at a concentration of 1.2 mol / l in a non-aqueous electrolyte (a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 3: 7) from the remaining one side of both laminate films. Solution). Thereafter, the remaining one side of both laminate films was vacuum-sealed to obtain a lithium ion secondary battery having the structure shown in FIG. 4 with the appearance shown in FIG.

  Here, FIG. 3 and FIG. 4 will be described. FIG. 3 is a plan view schematically showing a lithium ion secondary battery, and FIG. 4 is a cross-sectional view taken along the line BB of FIG. The lithium ion secondary battery 100 includes a laminated electrode body having a positive electrode 10, a negative electrode 20, and a separator 30 in a laminated film outer package 200 composed of two laminated films, and a zigzag folded structure. An electrolyte solution (not shown) is accommodated, and the laminate film outer package 200 is sealed by heat-sealing the upper and lower laminate films at the outer peripheral portion thereof. In FIG. 4, the layers constituting the laminate film outer package 200 and the layers of the positive electrode 10 and the negative electrode 20 are not shown separately in order to avoid the drawing from becoming complicated.

  Each positive electrode 10 is connected to the positive electrode external terminal 14 by a current collecting tab in the battery 100, and each negative electrode 20 is also connected to the negative electrode external terminal 24 by a current collecting tab in the battery 100. doing. The positive electrode external terminal 14 and the negative electrode external terminal 24 are drawn out to the outside of the laminate film outer package 200 so that they can be connected to an external device or the like.

Comparative Example 1
A positive electrode was produced in the same manner as in Example 1 except that the insulating layer was formed from the end of the positive electrode mixture layer to the position of 30 μm upward in FIG. And the lithium ion secondary battery was produced like Example 1 except having used this positive electrode.

Comparative Example 2
A positive electrode was produced in the same manner as in Example 1 except that the insulating layer was not formed, and a lithium ion secondary battery was produced in the same manner as in Example 1 except that this positive electrode was used.

  The following evaluation was performed about the lithium ion secondary battery of an Example and a comparative example, and the positive electrode and laminated electrode body which were used for these batteries.

<Measurement of positive electrode burr>
About the positive electrode used for the lithium ion secondary battery of an Example and a comparative example, using an optical microscope, the magnification of a burr is made from the cross-sectional direction of a narrow part over the perimeter of a narrow part at a magnification of 200 times. Observed, and the maximum value among them was defined as the burr height.

<Withstand voltage measurement test of laminated electrode body>
500 laminated electrode bodies identical to those used in the lithium ion secondary batteries of Examples and Comparative Examples were produced. These laminated electrode bodies were subjected to a withstand voltage test under the conditions of applied voltage: 500 kV and current threshold value: 60 μA, and the number of defects generated was examined.

<Evaluation of discharge characteristics of lithium ion secondary battery>
About the lithium ion secondary battery of an Example and a comparative example, it carries out constant current charge to 4.2V with the electric current value of 1C, and then performed constant voltage charging with the voltage of 4.2V until the electric current value became 0.05C. After that, discharging was performed at a current value of 1 C until the voltage became 2.5 V, and the discharge characteristics were evaluated.

  Table 1 shows the configurations of the positive electrodes according to the lithium ion secondary batteries of Examples and Comparative Examples, and the number of occurrence of withstand voltage failures determined by the withstand voltage measurement test of the laminated electrode body. Moreover, the discharge curve of the lithium ion secondary battery of Example 1 and Comparative Example 2 obtained by the above-mentioned discharge characteristic evaluation is shown in FIG.

  As shown in Table 1, the positive electrode according to the lithium ion secondary battery of Example 1 in which a porous insulating layer was formed at a predetermined position was the positive electrode according to the lithium ion secondary battery of Comparative Example 2 in which no insulating layer was formed. Compared with, the height of burrs was small and the occurrence of burrs was suppressed. And in the laminated electrode body according to the lithium ion secondary battery of Comparative Example 2, there was a defective in the withstand voltage measurement test, whereas in the laminated electrode body according to the lithium ion secondary battery of Example 1, No failure occurred in the withstand voltage measurement test. Therefore, it can be said that the lithium ion secondary battery of Example 1 has higher reliability than the battery of Comparative Example 2.

  On the other hand, the positive electrode according to the lithium ion secondary battery of Comparative Example 1 in which the porous insulating layer was not properly formed had a lower burr height than the positive electrode according to the battery of Comparative Example 2, Compared with the positive electrode according to the battery of Example 1, its height was increased. In the laminated electrode body according to the lithium ion secondary battery of Comparative Example 1, in the withstand voltage measurement test, compared with the laminated electrode body according to the battery of Comparative Example 1, the number of occurrences was small, but the defective one was defective. Existed. Therefore, it can be said that the battery of Comparative Example 2 is inferior in reliability to the battery of Example 1.

  Further, as shown in FIG. 5, the lithium ion secondary battery of Example 1 has substantially the same discharge curve due to charge / discharge in 1C as the battery of Comparative Example 2, and a porous insulating layer is formed on the positive electrode. However, the discharge characteristics of the battery were well maintained.

10 Electrode for lithium ion secondary battery (positive electrode)
10a body part 10b narrow part 11 electrode mixture layer (positive electrode mixture layer)
12 Current collector 13 Insulating layer 20 Negative electrode 30 Separator 100 Lithium ion secondary battery

Claims (4)

An electrode used in a lithium ion secondary battery,
A main body part, and a narrow part that is narrower than the main body part and protrudes from the main body part in a plan view;
An electrode mixture layer containing an active material is formed on one side or both sides of a current collector at the location including the boundary between the main body portion and the main body portion of the narrow portion,
The surface of the electrode mixture layer and the region of the narrow portion from the end of the electrode mixture layer forming portion to at least the same length as the thickness of the electrode mixture layer are covered with a porous insulating layer. Has been
The current collector is exposed at least at a part of the narrow portion that is not covered with the insulating layer. The electrode for a lithium ion secondary battery, wherein:   The electrode for a lithium ion secondary battery according to claim 1, wherein the insulating layer contains an inorganic filler. A lithium ion secondary battery having a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte,
3. The lithium ion secondary battery according to claim 1, wherein at least one of the positive electrode and the negative electrode is the electrode for a lithium ion secondary battery according to claim 1. It is a manufacturing method of the electrode for lithium ion secondary batteries according to claim 1 or 2,
Forming an electrode mixture layer containing an active material on a part of the surface of the current collector;
Of the surface of the electrode mixture layer and the exposed portion of the current collector not forming the electrode mixture layer, at least the thickness of the electrode mixture layer from the end of the electrode mixture layer forming portion A step of covering the region up to the length with a porous insulating layer to form a laminate for an electrode;
And a step of punching out the electrode laminate. A method for producing an electrode for a lithium ion secondary battery.

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