JP2014154360A - Nonaqueous electrolyte secondary battery and collector for the battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a collector for a nonaqueous electrolyte secondary battery, excellent in corrosion resistance (typically, alkali resistance) and capable of achieving low resistance.SOLUTION: The present invention provides a collector 32 including a base material 32a made of metal and a corrosion resistant layer 32b provided on a surface of the base material. The corrosion resistant layer 32b contains a carbon material 33, an alginic acid 34, and a compound 35 having a polyoxyalkylene styrenated phenyl ether structure. When the carbon material 33 is taken as 100 pts.mass, the percentage of the alginic acid 34 is 0.3 pt.mass or more and 10 pts.mass or less, and the percentage of the compound 35 having a polyoxyalkylene styrenated phenyl ether structure is 0.1 pt.mass or more and 2 pts.mass or less. In a preferable embodiment, the corrosion resistant layer 32b has an average thickness of 0.5 μm or more and 6.5 μm or less.

Description

  The present invention relates to a current collector for a non-aqueous electrolyte secondary battery and use thereof. More specifically, the present invention relates to a current collector provided with a corrosion-resistant layer and a non-aqueous electrolyte secondary battery using the current collector.

  A member made of a metal such as aluminum is widely used in various fields, and its durability (such as corrosion resistance) can affect the durability of a product including the member. An example of a product including such a metal member is a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.

An electrode of this type of battery generally includes a metal current collector and an electrode active material layer formed on the current collector. Such an electrode active material layer is provided, for example, by applying a slurry for forming an active material layer (including paste and ink; the same shall apply hereinafter) containing an electrode active material and a binder in a predetermined liquid medium on a current collector. It can be formed by drying. At the time of preparing the slurry, an aqueous solvent (typically water) may be used for the purpose of reducing environmental burden and cost. However, for example, when an aqueous solvent is used at the time of forming the positive electrode active material layer, a constituent element (for example, manganese) of the positive electrode active material is eluted, and the slurry may exhibit high alkalinity. Since the positive electrode current collector is typically made of a metal such as aluminum, the positive electrode current collector can be corroded and generate gas when it comes into contact with a highly alkaline slurry. In such a case, peeling or floating of the positive electrode active material layer may occur, leading to a decrease in battery characteristics (for example, an increase in resistance).
Patent documents 1-4 are mentioned as a technique relevant to this. For example, Patent Document 1 discloses a battery having a configuration in which a positive electrode active material layer contains alginic acid that can relieve the high alkalinity as described above and can also function as a binder.

JP 2011-192644 A JP 2006-134777 A JP 2004-063156 A JP 2003-272619 A

  However, according to the study by the present inventors, when alginic acid is contained in the positive electrode active material layer, resistance (particularly, IV resistance in a low temperature environment) accompanying charging / discharging is remarkably increased, and battery characteristics are greatly deteriorated. There was a thing. Moreover, in order to express the alkaline relaxation (neutralization) effect appropriately, a large amount of addition may be required. This invention is made | formed in view of this point, The objective is to provide the electrical power collector excellent in corrosion resistance (typically alkali resistance). Another object of the present invention is a non-aqueous electrolyte secondary battery using such a current collector, in which corrosion of the current collector is suppressed and excellent battery performance (for example, low temperature) It is to provide a non-aqueous electrolyte secondary battery capable of exhibiting a high input / output density in an environment.

When the present inventors examined the cause of the deterioration of the battery characteristics in Patent Document 1, the surface of the positive electrode active material was coated with alginic acid, and the occlusion and release of charge carriers were inhibited. I found that it was causing. Moreover, since alginic acid has a highly reactive carboxyl group (—COO ⁻ ), when used alone, it binds to the surface of a conductive material such as a carbon material or a positive electrode active material (typically a surface functional group). , Easy to produce aggregates. When a large amount of alginic acid is consumed for bonding with the conductive material and the positive electrode active material, it is not possible to efficiently reduce the alkalinity. For this reason, a large amount of addition is required to exhibit the effect of the alkalinity relaxation. I understood it. Therefore, the present inventors have conducted intensive studies, found a means that can solve this, and completed the present invention.

  According to the present invention, a current collector for a non-aqueous electrolyte secondary battery is provided. Such a current collector includes a metal base material and a corrosion-resistant layer provided on the surface of the base material. The corrosion-resistant layer contains a carbon material, alginic acid, and a compound having a polyoxyalkylene styrenated phenyl ether structure (hereinafter sometimes referred to as “polyoxyalkylene styrenated phenyl ether structure-containing compound”). Yes. Further, when the carbon material is 100 parts by mass, the ratio of the alginic acid is 0.3 parts by mass or more and 10 parts by mass or less, and the ratio of the polyoxyalkylene styrenated phenyl ether structure-containing compound is 0.1 parts by mass. Part to 2 parts by mass.

  The polyoxyalkylene styrenated phenyl ether structure-containing compound can function as a so-called dispersant. For this reason, in the corrosion-resistant layer containing the compound, the constituent material (typically a carbon material) can be more uniformly dispersed, and high homogeneity and denseness can be realized. In addition, by including both the polyoxyalkylene styrenated phenyl ether structure-containing compound and alginic acid in the corrosion-resistant layer, the amount of alginic acid used can be reduced as compared with the conventional one, and the substrate has excellent corrosion resistance. Can be granted. In addition, alginic acid is hydrophilic and therefore difficult to dissolve in organic solvents. For example, even when stored in an organic solvent for a long time in a high-temperature environment, it does not easily swell or deform, and exhibits high shape maintainability. Can do. In addition, by including a carbon material in the corrosion-resistant layer, an increase in resistance due to the formation of the corrosion-resistant layer is suppressed, and the good conductivity of the base material itself can be exhibited without deteriorating. Therefore, the current collector having the above configuration is excellent in corrosion resistance (the generation of gas accompanying corrosion is suppressed) and the resistance is suppressed low. Such a current collector can be suitably used, for example, in an application (for example, production of a positive electrode) that can come into contact with an alkaline solution (for example, a slurry for forming a positive electrode active material layer).

  In the present specification, the “non-aqueous electrolyte secondary battery” refers to a battery provided with a non-aqueous electrolyte (typically, a non-aqueous electrolyte containing a supporting salt in a non-aqueous solvent). Further, in the present specification, the “lithium ion secondary battery” refers to a secondary battery that uses lithium ions as a charge carrier and is charged and discharged by movement of lithium ions between positive and negative electrodes. A secondary battery generally referred to as a lithium ion secondary battery, a lithium polymer battery, a lithium air battery, a lithium sulfur battery, or the like is a typical example included in the lithium ion secondary battery in the present specification.

  Although depending on the pH of the alkaline solution that can be contacted, the average thickness of the corrosion-resistant layer is preferably 0.5 μm or more and 6.5 μm or less. When satisfy | filling the said range, it can suppress suitably corroding by an alkali, maintaining internal resistance lower. Therefore, even more excellent battery characteristics (for example, excellent input / output characteristics in a low temperature environment) can be exhibited, and the effects of the present invention can be exhibited at a high level. The average thickness of the layer can be confirmed by measurement using a micrometer, a thickness meter (for example, a rotary caliper meter) or the like, or observation with an electron microscope (typically SEM: Scanning Electron Microscope).

  In a preferred embodiment, the compound having a polyoxyalkylene styrenated phenyl ether structure (typically a polyoxyethylene styrenated phenyl ether structure) is polyoxyethylene styrenated phenyl ether. Since the above compound is a nonionic surfactant, the load on the environment (environmental toxicity) is low, and since the hydrophilic group does not dissociate into ions, it is difficult to cause an unintended reaction or the like. Therefore, it can be suitably used.

  As another aspect of the present invention, there is provided a nonaqueous electrolyte secondary battery comprising an electrode having an active material layer formed on the surface of any of the current collectors described above and a nonaqueous electrolyte. The current collector disclosed here includes a corrosion-resistant layer that is dense and excellent in corrosion resistance (typically alkali resistance). In the electrode using such a current collector, various problems due to corrosion (for example, generation of gas, peeling of the active material layer, floating, etc.) hardly occur, and thus high battery performance can be exhibited.

  In a preferred embodiment, the electrode is a positive electrode. The active material layer includes at least a positive electrode active material and a water-soluble and / or water-dispersible polymer compound other than alginic acid (hereinafter, such a property may be simply referred to as “aqueous”). Contains. By not containing alginic acid substantially in the positive electrode active material layer, the surface of the positive electrode active material is not covered with alginic acid. For this reason, occlusion and discharge | release of a charge carrier are performed smoothly and the resistance accompanying charging / discharging can be restrained low. Therefore, for example, even when the positive electrode active material layer is formed using an aqueous positive electrode active material layer forming slurry, the current collector is hardly corroded, and excellent battery characteristics (for example, input / output characteristics, particularly in a low temperature environment). Can exhibit the input / output characteristics). Here, “substantially” means that alginic acid is not intentionally contained at least intentionally, and is a term that allows, for example, inevitable mixing (for example, a slight inflow from the corrosion-resistant layer side).

In a preferred embodiment, the polymer compound contained in the active material layer is a cellulosic polymer (typically carboxymethyl cellulose) and / or an ethylene polymer (eg, polytetrafluoroethylene).
The cellulosic polymer has a function as a thickener and the like, and can provide adhesion and flexibility to the positive electrode active material layer. For this reason, for example, even when the positive electrode active material expands / shrinks as the charge carriers are occluded / released, the adhesion with the current collector can be suitably maintained. For example, when forming a positive electrode active material layer using a water-based positive electrode active material layer forming slurry, the fluidity of the slurry can be optimized, and the positive electrode active material layer can be formed with high accuracy. On the other hand, the ethylene-based polymer can function as a binder, and can maintain and improve the adhesion between the positive electrode current collector and the positive electrode active material layer and / or the shape retention of the positive electrode active material layer. In particular, by using a cellulose-based polymer and an ethylene-based polymer in combination, even higher conductivity and shape retention can be realized. For example, a positive electrode active material layer is formed using an aqueous positive electrode active material layer forming slurry. Even in this case, excellent battery characteristics and high durability can be realized.

  As described above, in the non-aqueous electrolyte secondary battery (for example, lithium ion secondary battery) disclosed herein, various problems caused by corrosion of the current collector (for example, due to the effect of using the current collector with a corrosion-resistant layer) Gas generation, separation of the active material layer, floating, etc.) are difficult to occur, and the internal resistance can be reduced. For example, the input / output characteristics are excellent, and even when stored in a high temperature environment, the capacity can be reduced and the generation of gas can be reduced. Therefore, taking advantage of this feature, for example, it can be suitably used as a power source (drive power source) of a hybrid vehicle or an electric vehicle.

It is a perspective view which shows typically the external shape of the nonaqueous electrolyte secondary battery which concerns on one Embodiment. It is a longitudinal cross-sectional view which follows the II-II line | wire in FIG. It is a schematic diagram which shows the structure of the wound electrode body which concerns on one Embodiment. It is a schematic diagram which shows the structure of the positive electrode sheet which concerns on one Embodiment. It is a graph which shows the relationship between the capacity maintenance rate (%) after a cycle test, and a corrosion trace.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, the structure of the negative electrode, the separator and the nonaqueous electrolyte, the construction of the secondary battery, etc.) It can be grasped as a design matter of those skilled in the art based on the prior art. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

≪Current collector≫
The current collector for a non-aqueous electrolyte secondary battery disclosed herein includes a metal base material and a corrosion-resistant layer provided on the surface of the base material. Such a current collector has a high level of both corrosion resistance and conductivity.

<Base material>
The substrate is preferably made of a metal material (that is, made of metal), and is preferably made of a metal having good conductivity. For example, aluminum, copper, nickel, titanium, stainless steel, etc. can be used suitably. The metal material constituting the base material may be substantially one type of metal (inevitable inclusion of inevitable impurities) or an alloy of two or more types of metals. In a preferred embodiment, the substrate is made of aluminum. A current collector provided with an aluminum base material can be suitably employed as a positive electrode current collector of a nonaqueous electrolyte secondary battery, for example.
The shape of the substrate is not particularly limited because it may vary depending on, for example, the shape of the nonaqueous electrolyte secondary battery to be constructed, but may be, for example, a foil shape, a plate shape, a net shape, or a rod shape. In addition, in the nonaqueous electrolyte secondary battery provided with the winding electrode body mentioned later, a foil-shaped thing is mainly used. The average thickness of the foil-shaped substrate is not particularly limited, but it is usually preferably about 5 μm to 50 μm (more preferably 8 μm to 30 μm) in consideration of the energy density and mechanical strength of the battery.

<Corrosion resistant layer>
The corrosion-resistant layer contains a carbon material, alginic acid, and a polyoxyalkylene styrenated phenyl ether structure-containing compound.

  Carbon materials include carbon black (for example, acetylene black, furnace black, ketjen black, channel black, lamp black, thermal black), coke, activated carbon, graphite (natural graphite and its modified products, artificial graphite), carbon fiber One or more selected from (PAN-based carbon fiber, pitch-based carbon fiber), carbon nanotube, fullerene, graphene, and the like can be used. Among these, carbon black (typically acetylene black) can be preferably used.

The properties of such a carbon material are not particularly limited. Usually, the smaller the primary particle size, the larger the specific surface area, which is advantageous for maintaining a conductive path in the corrosion-resistant layer. In the case of the carbon material described above, the particle size of the primary particles constituting the carbon material is preferably in the range of about 1 nm to 500 nm (for example, about 10 nm to 200 nm, typically about 15 nm to 100 nm). In addition, as the “particle size of the primary particles”, at least 30 (for example, 30 to 100) can be used according to an electron microscope (scanning type or transmission type, preferably transmission type electron microscope) photograph. The primary particles are observed, and the arithmetic average value of the obtained particle diameters can be adopted. Further, for the same reason as described above, the specific surface ^{area, 25m 2 / g~1000m 2 / g} ( typically ^{50m 2} / ^g~500m 2 / g, preferably ^{50m 2} / ^g~200m 2 / g, e.g. it is preferably in the range of ^{50m 2 / g~100m 2 / g)} . Furthermore, the bulk density is in the range of 0.01 to 0.5 g / cm ³ (typically 0.05 to 0.3 g / cm ³ , preferably 0.1 to 0.2 g / cm ³ ). preferable. By including a carbon material satisfying one or more (preferably two or more) of the above properties in the corrosion-resistant layer, it is possible to suppress an increase in resistance due to the formation of the corrosion-resistant layer, and good conductivity derived from a metal substrate. Can be maintained. A carbon black such as acetylene black is preferably used to satisfy such properties.

Alginic acid is a 1,4-glycoside bond in which two types of uronic acid, β-D-mannuronic acid (M) and α-L-guluronic acid (G), represented by the general formula: (C ₆ H ₈ O ₆ ) _n Is a linear polyuronide bonded at an arbitrary ratio. Typically, the poly-β-D-mannuronic acid sites in which the Ms are connected to each other, the poly-α-L-guluronic acid sites in which the Gs are connected to each other, and M and G are alternately arranged. It has a structure in which the part is mixed. Since M and G have a highly reactive carboxyl group, alginic acid can suitably function as a binder. Since alginic acid can relax the pH of the alkaline solution, it can be included in the corrosion-resistant layer to realize a highly durable current collector that is hardly corroded even when it comes into contact with, for example, an alkaline slurry. obtain. Furthermore, alginic acid is hydrophilic and thus hardly dissolved in an organic solvent. For example, even when stored in an organic solvent for a long period of time in a high-temperature environment, it does not easily swell, and can exhibit high shape maintainability. .

  As alginic acid, alginic acid and salts and derivatives thereof can be used, and one or more selected from these can be used as appropriate. Of these, various alginates (for example, sodium alginate, potassium alginate, ammonium alginate, etc.) can be preferably used from the viewpoint of solubility, and sodium alginate having particularly high versatility can be suitably employed. Such alginic acid may be extracted from a natural product (comb, seaweed, hijiki, etc.) by a conventionally known method, or may be obtained by purchasing a commercially available product. Examples of commercially available sodium alginate include various grades of “Kimika Argin” (registered trademark) manufactured by Kimika Co., Ltd.

  The properties of alginic acid are not particularly limited, but those having a weight average molecular weight (Mw) of 10,000 to 500,000 can be suitably used. When the molecular weight is extremely smaller than the above range, the amount of addition necessary for exhibiting the function as the binder and / or the effect of pH relaxation increases, and the resistance may increase. On the other hand, when the molecular weight is extremely large, the viscosity of the solvent becomes high and the handleability may be lowered, or the dispersion in the solvent may become unstable. The weight average molecular weight (Mw) can be calculated from a molecular weight distribution obtained by general GPC (Gel Permeation Chromatography) -RI (Refractive Index Detector) measurement.

  In the corrosion-resistant layer, the proportion of alginic acid is suitably 0.3 to 10 parts by mass when the carbon material is 100 parts by mass, for example 0.5 to 5 parts by mass. It is preferable that The corrosion-resistant layer disclosed here contains a polyoxyalkylene styrenated phenyl ether structure-containing compound, so that the function as a binder (shape retention) even when the amount of alginic acid used is smaller than in the past. Can be suitably exerted, and excellent corrosion resistance can be imparted to a metal substrate.

  Examples of the polyoxyalkylene styrenated phenyl ether structure-containing compound include polyoxyalkylene styrenated phenyl ether and salts thereof (for example, sulfate (sodium sulfate, ammonium sulfate, etc.), phosphate, phosphate ester, acetate (for example, sodium acetate). , Sulfosuccinate and the like) and derivatives. Such a compound can function as a dispersant in a slurry for forming a corrosion-resistant layer, for example. For this reason, in the corrosion-resistant layer containing the compound, the constituent material (typically a carbon material) can be more uniformly dispersed, and high homogeneity and denseness can be realized. As such a compound, 1 type (s) or 2 or more types can be used suitably from what is generally used as surfactant, for example. Specifically, nonionic surfactants such as polyoxyalkylene styrenated phenyl ether; polyoxyalkylene styrenated phenyl ether ammonium sulfate, polyoxyalkylene styrenated phenyl ether phosphate ester, polyoxyalkylene tridecyl ether phosphate ester And anionic surfactants such as nonionic surfactants can be suitably employed. Nonionic surfactants are preferred because they have a low environmental burden (environmental toxicity) and hardly cause unintended chemical reactions in the corrosion-resistant layer because the hydrophilic groups do not dissociate into ions.

  The polyoxyalkylene group is not particularly limited, but typically may have 2 to 6 carbon atoms (for example, 2 to 4) and / or an average added mole number of about 1 to 500 (for example, 2 to 200). . Specific examples include ethylene oxide and propylene oxide. In other words, the polyoxyalkylene styrenated phenyl ether structure may be a polyoxyethylene styrenated phenyl ether structure, a polyoxypropylene styrenated phenyl ether structure, or the like. Polyoxyethylene styrenated phenyl ether structure-containing compounds include polyoxyethylene styrenated phenyl ether, polyoxyethylene styrenated phenyl ether ammonium sulfate, polyoxyethylene styrenated phenyl ether phosphate ester, polyoxyethylene tridecyl ether phosphate ester Etc. are exemplified. As such a compound, for example, a commercially available product can be used. For example, “Neugen (registered trademark) EA”, “Hitenol (registered trademark) NF”, “Plysurf (registered trademark)” manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Various grades such as "Trademark)" can be adopted.

  In the corrosion-resistant layer, the proportion of the polyoxyalkylene styrenated phenyl ether structure-containing compound is suitably 0.1 to 2 parts by mass when the carbon material is 100 parts by mass, for example 0 More than 1 part by mass and less than 2 parts by mass.

  Although the method of forming such a corrosion-resistant layer is not particularly limited, for example, it can be performed as follows. First, a slurry-like composition (slurry for forming a corrosion-resistant layer) in which a carbon material, alginic acid, and a polyoxyalkylene styrenated phenyl ether structure-containing compound are dispersed or dissolved in an appropriate solvent is prepared. By applying this slurry to the surface of a metal substrate and drying the solvent, the above-mentioned corrosion-resistant layer can be formed. In addition, operation which provides the said slurry can be performed by a conventionally well-known general application means. For example, it can be carried out using an appropriate coating apparatus such as a gravure coater, a slit coater, a die coater, a comma coater, or a dip coater. The solvent can also be dried by a conventionally known general drying means (typically vacuum drying or heat drying).

As the solvent used for the preparation of the slurry for forming the corrosion-resistant layer, as long as the constituent materials of the corrosion-resistant layer (that is, the carbon material, alginic acid, and polyoxyalkylene styrenated phenyl ether structure-containing compound) can be suitably dispersed and / or dissolved. Although not particularly limited, typically, an aqueous solvent, that is, water or a mixed solvent mainly containing water can be preferably used. In general, as the electrolyte of the nonaqueous electrolyte secondary battery, a solution in which a supporting salt (a lithium salt in a lithium ion secondary battery) is dissolved or dispersed in a nonaqueous solvent is used. For this reason, if an organic solvent and a hydrophobic (lipophilic) high binder are used during the formation of the corrosion resistant layer, for example, when the battery is stored for a long time in a high temperature environment, the binder swells and the corrosion resistant layer deteriorates. Can be. Therefore, by forming the corrosion-resistant layer using an aqueous solvent and a highly hydrophilic binder (alginic acid), such deterioration can be prevented and a battery excellent in durability (for example, storage characteristics) can be realized.
The solvent other than water constituting the mixed solvent may be one or more organic solvents (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water. Among them, those in which 80% by mass or more (more preferably 90% by mass or more, more preferably 95% by mass or more) of the aqueous solvent is water can be preferably used. From various viewpoints such as reduction of environmental burden and reduction of waste, an aqueous solvent substantially composed of water (for example, water) is particularly preferable.

The suitable properties of the corrosion-resistant layer are not particularly limited because it may vary depending on the pH of the alkaline solution that can be contacted. ) Is preferably 0.5 μm or more and 6.5 μm or less. Further, the density of the corrosion-resistant layer (the average thickness per one side in the structure having the corrosion-resistant layer on both surfaces of the base material) is 0.5 g / cm ^{3 to} 2.0 g / cm ³ (typically 1.0 g / cm ^3). ˜1.5 g / cm ³ ). Moreover, it is preferable that the porosity of a corrosion-resistant layer is 5 volume%-40 volume% (typically 10 volume%-35 volume%, Preferably it is 15 volume%-30 volume%). When satisfy | filling the said range, it can suppress suitably corroding by an alkali, maintaining internal resistance lower.

  In addition, the corrosion-resistant layer may be provided over the whole surface of a base material, and may be provided only to a part of surface. For example, the aspect by which the said corrosion-resistant layer was provided only to the part which is easy to be influenced by corrosion among the base-material surfaces may be sufficient.

≪Nonaqueous electrolyte secondary battery≫
The present invention also provides a non-aqueous electrolyte secondary battery comprising an electrode having an active material layer formed on the surface of any of the current collectors described above and a non-aqueous electrolyte. As described above, the current collector disclosed herein is excellent in corrosion resistance (typically alkali resistance). Therefore, in a battery using such a current collector, problems due to corrosion (for example, generation of gas, peeling of the active material layer, floating, etc.) hardly occur, and high battery characteristics are stably exhibited over a long period of time. be able to.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings as appropriate. In the following drawings, members / parts having the same action are denoted by the same reference numerals, and redundant description may be omitted. Note that the dimensional relationship (length, width, thickness, etc.) in each drawing does not necessarily reflect the actual dimensional relationship.

  Although not intended to be particularly limited, as a schematic configuration of the nonaqueous electrolyte secondary battery according to one embodiment of the present invention, a flatly wound electrode body (wound electrode body), a nonaqueous electrolyte, As an example, FIG. 1 and FIG. 2 show the schematic configuration of a non-aqueous electrolyte secondary battery (unit cell) in a form in which the battery is accommodated in a flat rectangular parallelepiped (square) container. FIG. 1 is a perspective view schematically showing the outer shape of the nonaqueous electrolyte secondary battery 10 according to the present embodiment. FIG. 2 is a longitudinal sectional view taken along line II-II in FIG.

  As shown in FIGS. 1 and 2, the nonaqueous electrolyte secondary battery 10 according to the present embodiment includes a wound electrode body 20 and a battery case (outer container) 80. The battery case 80 includes a flat rectangular parallelepiped (rectangular) battery case main body 84 having an open upper end, and a lid 82 that closes the opening. On the upper surface (that is, the lid 84) of the battery case 80, a positive terminal 40 for external connection that is electrically connected to the positive electrode of the wound electrode body 20, and a negative electrode terminal that is electrically connected to the negative electrode of the electrode body 20 60 is provided. In addition, the lid 84 is provided with a safety valve 85 for discharging the gas generated inside the battery case 80 to the outside of the case 80 as in the case of the battery case of the conventional nonaqueous electrolyte secondary battery.

<Battery case 80>
As a material constituting the battery case 80, the same material as that used in a general non-aqueous electrolyte secondary battery can be used as appropriate, and there is no particular limitation. For example, a metal material such as aluminum or steel; a high melting point resin material such as polyphenylene sulfide resin or polyimide resin can be used. Among them, a relatively light metal (for example, aluminum or aluminum alloy) can be preferably employed for the purpose of improving heat dissipation and increasing energy density. The shape (outer shape of the container) of the battery case 80 is, for example, a circular shape (cylindrical shape, coin shape, button shape), hexahedron shape (rectangular shape, cube shape), bag shape, and a shape obtained by processing and deforming them. obtain.

<Winded electrode body 20>
Inside the battery case 80, a long sheet-like positive electrode (positive electrode sheet) 30 and a long sheet-like negative electrode (negative electrode sheet) 50 are flattened via two long sheet-like separators (separator sheets) 70. An electrode body 20 (winding electrode body) 20 wound in the form of a non-aqueous electrolyte (not shown) is accommodated.
FIG. 3 is a schematic diagram showing a configuration of the wound electrode body 20 shown in FIG. As shown in FIG. 3, the wound electrode body 20 according to the present embodiment has a flat and long sheet structure in a stage before assembly. The wound electrode body 20 includes a positive electrode sheet 30, a separator sheet 70, a negative electrode sheet 50, and a separator sheet 70 that are sequentially stacked and wound in the longitudinal direction, and further crushed from the side surface direction to be ablated. It is molded into a flat shape. At both ends of the wound electrode body 20 in the winding axis WL direction, portions 43 of the positive electrode sheet 30 and the negative electrode sheet 70 where the electrode active material layer is not formed (uncoated portion) are respectively separated from the wound core portion. It sticks out. The positive electrode side protruding portion 43 and the negative electrode side protruding portion 43 are respectively provided with a positive electrode current collector plate and a negative electrode current collector plate, and are electrically connected to the positive electrode terminal 40 (FIG. 2) and the negative electrode terminal 60 (FIG. 2), respectively. Has been.

  The width of the negative electrode active material layer 56 is wider than the width of the positive electrode active material layer 36, and typically the negative electrode active material layer 56 covers the positive electrode active material layer 36 in the width direction. Further, the separator sheet 70 covers the negative electrode active material layer 56 in the width direction, thereby ensuring insulation between the positive electrode sheet 30 and the negative electrode sheet 50. That is, the dimensional relationship in the width direction is that the width b1 of the negative electrode active material layer 56 is slightly wider than the width a1 of the positive electrode active material layer 36, and the width c1 of the separator sheet 70 is wider than the width b1 of the negative electrode active material layer 56. , C2 are slightly wider (c1, c2> b1> a1). According to such a configuration, since the negative electrode active material layer 56 is wider than the positive electrode active material layer 36, the acceptability of charge carriers in the negative electrode is increased. For example, the charge carriers are deposited in the negative electrode (for example, precipitation of lithium dendrite). It can suppress suitably.

<Positive electrode sheet 30>
As shown in FIG. 3, the positive electrode sheet 30 includes a long positive electrode current collector 32 in which a corrosion-resistant layer 32b is formed on the surface of a metal substrate 32a, and a longitudinal direction on one or both surfaces of the current collector. And a positive electrode active material layer 36 including at least a positive electrode active material 37. FIG. 4 is a cross-sectional view schematically showing the configuration on one side of the positive electrode 30 shown in FIG. As shown in FIGS. 3 and 4, in this embodiment, the corrosion-resistant layer 32 b is formed over the entire surface of the aluminum foil-like substrate 32 a. The positive electrode active material layer 36 is formed on both surfaces of the positive electrode current collector 32 except for the uncoated portion 43. Here, the term “layer” is simply a term used to distinguish one part in the thickness direction from the other part, and is not necessarily macroscopically and / or microscopically layered (for example, the corrosion-resistant layer 32b and the positive electrode active layer). It is not necessary that the interface with the material layer 36 is visually recognized.

  Such a positive electrode sheet 30 includes, for example, a positive electrode active material layer forming slurry in which a positive electrode active material 37 and a material used as necessary are dissolved or dispersed in an appropriate solvent. It can be produced by applying an appropriate amount to the surface of 32 and removing the solvent by drying. The positive electrode current collector 32 disclosed herein can be excellent in corrosion resistance by including the alginic acid 34 and the polyoxyalkylene styrenated phenyl ether structure-containing compound 35 in the corrosion-resistant layer 32b. Therefore, generation of gas due to corrosion and unevenness of the positive electrode current collector 32 are unlikely to occur, and the positive electrode active material layer 36 is preferably prevented from being lifted or separated from the positive electrode current collector 32.

As the positive electrode active material 37, one or more of various materials conventionally known to be usable as the positive electrode active material of the nonaqueous electrolyte secondary battery 10 can be employed without any particular limitation. For example, lithium nickel oxide (typically LiNiO ₂ ), lithium cobalt oxide (typically LiCoO ₂ ), lithium manganese oxide (typically LiMn ₂ O ₄ ), lithium iron oxide Oxide having a layered structure or spinel structure such as an oxide (typically LiFeO ₂ ); an olivine structure such as lithium manganese phosphate (typically LiMnPO ₄ ) or lithium iron phosphate (typically LiFePO ₄ ) And the like. Among these, from the viewpoint of thermal stability and energy density, lithium nickel cobalt manganese composite having a layered structure (typically a layered rock salt structure belonging to the hexagonal system) containing Li, Ni, Co and Mn as constituent elements. An oxide (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) can be preferably used.

Here, the lithium nickel cobalt manganese composite oxide is an oxide having Li, Ni, Co, and Mn as constituent metal elements, and at least one other metal element (Li, in addition to Li, Ni, Co, and Mn). , Oxides containing transition metal elements and / or typical metal elements other than Ni, Co and Mn). Such metal elements include, for example, magnesium (Mg), calcium (Ca), strontium (Sr), titanium (Ti), zirconium (Zr), vanadium (V), niobium (Nb), chromium (Cr), molybdenum (Mo ), Tungsten (W), iron (Fe), rhodium (Rh), palladium (Pb), platinum (Pt), copper (Cu), zinc (Zn), boron (B), aluminum (Al), gallium (Ga) ), Indium (In), tin (Sn), lanthanum (La), and cerium (Ce). The same applies to lithium nickel oxides, lithium cobalt oxides, and lithium manganese oxides.
The amount of the substitutional constituent element is not particularly limited. For example, it is 0.05% by mass or more (typically 0.1% by mass with respect to 100% by mass in total of the substitution element, Ni, Co, and Mn. As described above, for example, 0.2% by mass or more) and 5% by mass or less (typically 3% by mass or less, for example, 2.5% by mass or less).

For example, the general formula: xLi [Li _1/3 Mn _2/3 ] O _2. (1-x) LiMeO ₂ (wherein Me is one or more transition metals, and x is 0 It is also possible to use a so-called solid solution type lithium-excess transition metal oxide represented by <satisfying x ≦ 1.

  Such a positive electrode active material 37 can be produced by a conventionally known method. More specifically, for example, first, raw material compounds (for example, a lithium source and a transition metal element source) selected according to the composition of the target positive electrode active material 37 are mixed at a predetermined ratio, and this mixture is mixed with an appropriate means. Is fired. And it can obtain by grind | pulverizing, granulating, and classifying the obtained baked material suitably.

Although the property of the positive electrode active material 37 is not particularly limited, for example, the particle size may be 20 μm or less (typically 0.1 μm to 20 μm, for example 3 μm to 10 μm). The specific surface area is 0.1 m ² / g or more (typically 0.5 m ² / g or more, for example, 1 m ² / g or more), and 30 m ² / g or less (typically 10 m ² / g). Hereinafter, for example, 5 m ² / g or less). Further, the bulk density can be 1 to 4 g / cm ³ (typically 1.5 to ³ g / cm ³ , preferably 1.8 to 2.4 g / cm ³ ). By using a material satisfying one or more of the properties (particle size, specific surface area, bulk density) described above, the positive electrode active material layer 36 having high density and high conductivity can be formed. Moreover, an appropriate space | gap is hold | maintained in the positive electrode active material layer 36 formed using this positive electrode active material 37, and a non-aqueous electrolyte can osmose | permeate suitably. For this reason, the resistance in the positive electrode active material layer 36 can be further reduced.

In this specification, “particle size” corresponds to a cumulative 50% from the fine particle side in the volume-based particle size distribution measured by particle size distribution measurement based on a general laser diffraction / light scattering method unless otherwise specified. to particle size _{(D 50} particle size, also called median diameter.) refers to. In the present specification, the “specific surface area” refers to a specific surface area (BET specific surface area) measured by a BET method using nitrogen gas (for example, the BET single point method). In the present specification, “bulk density” refers to a value measured by a method defined in JIS K1469 (2003).

  In addition to the positive electrode active material 37, the positive electrode active material layer 36 requires one or more materials that can be used as a constituent component of the positive electrode active material layer 36 in the general nonaqueous electrolyte secondary battery 10. Can be contained accordingly. Examples of such a material include a conductive material and a binder 38.

As a conductive material, what was illustrated as a carbon material which comprises the corrosion-resistant layer 32b can be used, for example. Alternatively, metal fibers (eg, Al, SUS, etc.), conductive metal powders (eg, Ag, Ni, Cu, etc.), metal oxides (eg, ZnO, SnO _2, etc.), synthetic fibers whose surfaces are coated with metal, etc. may be used. Good. Among these, carbon materials such as acetylene black and ketjen black can be preferably used.
The proportion of the conductive material in the positive electrode active material layer 36 is not particularly limited. However, when the positive electrode active material 37 is 100 parts by mass, it is suitably 0.1 to 15 parts by mass, for example, 1 It can be made into 10 mass parts (preferably 2 mass parts-5 mass parts).

  As the binder 38, one or two or more substances conventionally used in the nonaqueous electrolyte secondary battery 10 can be employed without any particular limitation, and it is preferable that the binder 38 does not substantially contain alginic acid. In the case where alginic acid is included in the positive electrode active material layer 36, it is considered that the positive electrode active material 37 is covered with alginic acid and the charge carrier is occluded and released, so that the resistance associated with charge / discharge increases. In particular, such a tendency is remarkable in a low temperature environment (for example, an environment of 10 ° C. or less), and it is considered that battery characteristics (for example, input / output density) are remarkably lowered. However, since the positive electrode current collector 32 disclosed herein includes the corrosion-resistant layer 32b containing alginic acid on the surface thereof, the positive electrode active material layer 36 can exhibit high corrosion resistance without containing alginic acid. In the positive electrode active material layer 36 that does not contain alginic acid, there is no possibility that the positive electrode active material 37 is covered with alginic acid, so that resistance (particularly resistance in a low temperature environment) can be further reduced, and battery characteristics ( For example, output characteristics) can be remarkably improved.

  For example, when the positive electrode active material layer 36 is formed using an aqueous slurry, a polymer material other than alginic acid that can be dissolved or dispersed in water can be preferably used. Cellulose polymers such as carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), etc .; polyvinyl alcohol (PVA) And acrylic polymers such as polymethyl methacrylate (PMMA); urethane polymers such as polyurethane; and the like. Examples of polymer materials that are dispersed in water (water-dispersible) include vinyl polymers such as polyethylene (PE) and polypropylene (PP); ethylene polymers such as polyethylene oxide (PEO) and polytetrafluoroethylene (PTFE). Polymer: Tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA); vinyl acetate copolymer; styrene butadiene rubber (SBR), acrylic acid modified SBR resin Examples thereof include rubbers such as (SBR latex);

  Among these, cellulose polymers such as CMC and ethylene polymers such as PTFE can be preferably used. The cellulosic polymer has a function as a thickener and the like, and can provide adhesion and flexibility to the positive electrode active material layer. For this reason, for example, even when the positive electrode active material expands / shrinks as the charge carriers are occluded / released, the adhesion with the current collector can be suitably maintained. For example, when the positive electrode active material layer 36 is formed using an aqueous slurry, the fluidity of the slurry can be suitably optimized, and the positive electrode active material layer 36 can be formed with high accuracy. The ethylene-based polymer can function as a binder, and can maintain and improve the adhesion between the positive electrode current collector 32 and the positive electrode active material layer 36 and / or the shape retention of the positive electrode active material layer 36. In a preferred embodiment, both the cellulosic polymer and the ethylene polymer are included. Thereby, higher bonding strength and shape retention can be realized.

  The proportion of the binder 38 in the positive electrode active material layer 36 is not particularly limited, but is suitably 0.1 to 15 parts by mass when the positive electrode active material 37 is 100 parts by mass, for example, 1 It can be set to 10 parts by mass. In a preferred embodiment, the cellulose-based polymer and the ethylene-based polymer are 1 part by mass to 7 parts by mass (for example, 1 part by mass to 5 parts by mass), respectively, when the positive electrode active material 37 is 100 parts by mass. Is included. By setting it as the said structure, it can be set as the positive electrode active material layer 36 which was more excellent in adhesiveness and shape retainability.

  FIG. 4 schematically shows the structure of the positive electrode sheet 32 for easy understanding. The conductive material is not shown, and only one side of the base material 32a has a corrosion-resistant layer. 32b and the positive electrode active material layer 36 are described. Furthermore, it is not intended to reflect the actual state of the properties (density, etc.) of the positive electrode active material layer 36.

Mass of the positive electrode current collector 32 per unit area provided is a cathode active material layer 36, the cathode current collector 32 per one surface of ^{5mg / cm 2 ~40mg / cm 2} ( typically 10mg ^/ cm 2 ~20mg ^/ cm ² ) can be on the order. In the configuration having the positive electrode active material layer 36 on both surfaces of the positive electrode current collector 32 as in the embodiment shown in FIG. 3, the mass of the positive electrode active material layer 36 provided on each surface of the positive electrode current collector 32 is approximately the same. It is preferable to make it comparable. Further, the average thickness per one side of the positive electrode active material layer 36 is, for example, 40 μm or more (typically 50 μm or more) and 150 μm or less (typically 100 μm or less). Further, the density of the positive electrode active material layer 36 may be, for example, about 1.5 g / cm ^{3 to} 4 g / cm ³ (typically 1.8 g / cm ^{3 to 3} g / cm ³ ). The porosity (porosity) of the positive electrode active material layer 36 may be, for example, 5% to 40% by volume (preferably 20% to 40% by volume). By setting the properties of the positive electrode active material layer 36 in the above range, the resistance can be kept low while maintaining a desired capacity. For this reason, the output characteristics and energy density of the nonaqueous electrolyte secondary battery can be made compatible at a high level. The properties (porosity, thickness, density) of the positive electrode active material layer 36 can be adjusted by a conventionally known press treatment or the like.

  In the positive electrode 30 as shown in FIG. 4, when the average thickness of the corrosion-resistant layer 32b is t1, and the average thickness of the positive electrode active material layer 36 is t2, the ratio of the average thickness of the corrosion-resistant layer 32b and the positive electrode active material layer 36 (t1 / t2 ) Is preferably in the range of 0.01 ≦ t1 / t2 ≦ 0.1. As described above, although the average thickness t1 of the corrosion-resistant layer 32b is not strictly limited, the average thickness t1 of the corrosion-resistant layer 32b has a correlation with the corrosion preventing effect of the positive electrode current collector 32, so that it has strong alkalinity (for example, pH is 10). -14) In order to prevent corrosion of the positive electrode current collector 32 from the positive electrode active material layer forming slurry, t1 / t2 is 0.01 or more (for example, 0.02 or more, particularly 0.03 or more). Is preferred. In addition, if the average thickness of the corrosion-resistant layer 32b is too thick with respect to t2 of the positive electrode active material layer 36, an increase in resistance becomes remarkable, which is not preferable. From such a viewpoint, t1 / t2 is suitably 0.1 or less, preferably 0.05 or less. Thereby, the corrosion resistance of the positive electrode current collector and the reduction in resistance can be preferably achieved at the same time.

<Negative electrode sheet 50>
As shown in FIG. 3, the negative electrode sheet 50 includes a long negative electrode current collector 52 and a negative electrode active material layer 56 formed on one or both surfaces of the current collector along the longitudinal direction. And a negative electrode active material layer 56 containing an active material. In this embodiment, the negative electrode active material layer 56 is formed on both surfaces of the negative electrode current collector 52 except for the uncoated portion 43. Note that the negative electrode sheet 50 is not limited to a specific material, configuration, or the like, and may be one conventionally employed in this type of non-aqueous electrolyte secondary battery 10 or the like.
Such a negative electrode sheet 50 is formed on the surface of the negative electrode current collector 52 with, for example, a negative electrode active material layer forming slurry in which a negative electrode active material and materials used as necessary are dissolved or dispersed in a suitable solvent. It can be prepared by applying an appropriate amount and removing the solvent by drying. As the solvent, any of an aqueous solvent and an organic solvent can be used. For example, water can be used.

  As the negative electrode current collector 52, a conductive material made of a metal having good conductivity (for example, copper, nickel, titanium, stainless steel, etc.), as used in the negative electrode of the conventional non-aqueous electrolyte secondary battery 10 or the like. The material is preferably used. The shape of the negative electrode current collector 52 is not particularly limited because it can be different depending on the shape of the battery to be constructed. For example, a rod-like body, a plate-like body, a foil-like body, a net-like body, or the like can be adopted.

As the negative electrode active material, one or more kinds of various materials known to be usable as the negative electrode active material of the nonaqueous electrolyte secondary battery 10 can be used without any particular limitation. Although not particularly limited, for example, carbon materials such as natural graphite (graphite), artificial graphite, hard carbon (non-graphitizable carbon), soft carbon (graphitizable carbon), carbon black; silicon oxide, titanium oxide , Vanadium oxide, iron oxide, cobalt oxide, nickel oxide, niobium oxide, tin oxide, lithium silicon composite oxide, lithium titanium composite oxide (LTO, for example, Li ₄ Ti ₅ O ₁₂ , LiTi ₂ O ₄ , Li ₂ Ti ₃ O ₇ ), metal oxide materials such as lithium vanadium composite oxide, lithium manganese composite oxide, lithium tin composite oxide; metals such as lithium nitride, lithium cobalt composite nitride, lithium nickel composite nitride Nitride materials; metals such as tin, silicon, aluminum, zinc, lithium, or their gold And the like can be used; elemental metal material made of a metal alloy composed mainly of.

In addition to the above negative electrode active material, the negative electrode active material layer 56 may include one or more materials that can be used as a constituent component of the negative electrode active material layer 56 in the general nonaqueous electrolyte secondary battery 10 as necessary. May be contained. An example of such a material is a binder.
As the binder, for example, an appropriate material can be selected from the polymer materials exemplified as the constituent material of the positive electrode active material layer 36. Specific examples include carboxymethylcellulose (CMC) and styrene butadiene rubber (SBR). In addition, various additives such as a dispersant and a conductive material may be appropriately included as necessary. In addition, the polymer material illustrated as a binder above may be used in order to exhibit the function as a thickener and other additives.

  Although it does not specifically limit, when using a binder, when the said negative electrode active material is 100 mass parts, the ratio for which a binder occupies can be 0.5 mass part-10 mass parts, for example. . When using various additives, such as a dispersing agent, when the said negative electrode active material is 100 mass parts, the ratio for which an additive accounts is 1-10 mass parts (typically 1 mass part- 5 parts by mass).

<Separator sheet 70>
As shown in FIG. 4, in a typical configuration, a separator sheet 70 is interposed between the positive electrode sheet 30 and the negative electrode sheet 50. The separator sheet 70 may be made of any material that insulates the positive electrode active material layer 36 and the negative electrode active material layer 56 and has a nonaqueous electrolyte holding function and a shutdown function. Preferable examples include porous resin sheets (films) made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Such a porous resin sheet may have a single-layer structure or a multilayer structure of two or more layers (for example, a three-layer structure in which a PP layer is laminated on both sides of a PE layer). The average thickness of the separator sheet 70 is not particularly limited, but may be usually 5 μm to 50 μm (typically 10 μm to 40 μm, for example, 10 μm to 30 μm). Moreover, the structure provided with a porous heat-resistant layer may be provided on one side or both sides (typically, one side) of the porous sheet. Such a porous heat-resistant layer can be, for example, a layer containing an inorganic material (inorganic fillers such as alumina particles can be preferably employed) and a binder. Alternatively, it may be a layer containing insulating resin particles (for example, particles of polyethylene, polypropylene, etc.). In addition, in a nonaqueous electrolyte secondary battery (lithium polymer battery) using a solid electrolyte or a gel electrolyte, a separator may not be necessary (that is, in this case, the electrolyte itself may function as a separator). obtain.

<Nonaqueous electrolyte>
As the nonaqueous electrolyte, a solution obtained by dissolving or dispersing a supporting salt (for example, lithium salt, sodium salt, magnesium salt, etc., or lithium salt in a lithium ion secondary battery) in a nonaqueous solvent can be preferably used. Alternatively, the liquid non-aqueous electrolyte may be added with a polymer to form a solid (typically a so-called gel). As the supporting salt, the same salt as that of a general nonaqueous electrolyte secondary battery can be appropriately selected and adopted. For example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li (CF ₃ SO ₂ ) ₂ N Lithium salts such as LiCF ₃ SO ₃ can be used. Such a supporting salt can be used singly or in combination of two or more. Particularly preferred lithium salts, LiPF ₆ and the like. The nonaqueous electrolyte is preferably prepared so that the concentration of the supporting salt is in the range of 0.7 mol / L to 1.3 mol / L.

  As the non-aqueous solvent, organic solvents such as various carbonates, ethers, esters, nitriles, sulfones, and lactones used as non-aqueous electrolytes in general non-aqueous electrolyte secondary batteries are particularly limited. It can be adopted without. Specific examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like. Such a non-aqueous solvent can be used individually by 1 type or in combination of 2 or more types as appropriate. Furthermore, various additives can be appropriately added to the non-aqueous electrolyte as long as the object of the present invention is not significantly impaired. Such additives include, for example, 1 or 2 for improving battery output performance, improving storage stability (suppressing capacity reduction during storage, etc.), improving cycle characteristics, improving initial charge / discharge efficiency, and preventing overcharge. It can be used for the above purpose. Examples of preferred additives include fluorophosphates (typically difluorophosphates such as lithium difluorophosphate), lithium bisoxalate borate (LiBOB), vinylene carbonate (VC), fluoroethylene carbonate (FEC), Biphenyl (BP), cyclohexylbenzene (CHB), etc. are mentioned.

  The non-aqueous electrolyte secondary battery 10 disclosed herein can be used for various applications, but is characterized in that it can exhibit excellent battery performance in a wider temperature range. Therefore, it can be preferably used in applications requiring high energy density and input / output density in a wide temperature range. As such an application, for example, a power source (drive power source) for a motor mounted on a vehicle can be cited. The type of vehicle is not particularly limited, and examples include plug-in hybrid vehicles (PHV), hybrid vehicles (HV), electric vehicles (EV), electric trucks, motorbikes, electric assist bicycles, electric wheelchairs, electric railways, and the like. . Such a non-aqueous electrolyte secondary battery may be used in the form of an assembled battery formed by connecting a plurality of them in series and / or in parallel.

  The following examples further illustrate the present invention. However, it goes without saying that the present invention is not limited to these examples.

<Examples 1 to 17>
The positive electrode current collector according to Examples 1 to 17 was produced by the following procedure.
First, acetylene black as a carbon material (trade name “DENKA BLACK (pressed product): FX35” manufactured by Denki Kagaku Kogyo Co., Ltd., DEP oil absorption: 164 ml / 100 g) and sodium alginate as a binder (manufactured by Kimika Co., Ltd.) Trade name “Kimika Argin I-8”) and polyoxyethylene styrenated phenyl ether (trade name “Neugen: EA-87” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a dispersant were prepared. These materials are weighed so as to have a mass ratio shown in Table 1 (for example, in Example 1, carbon material: binder: dispersing agent = 100: 5: 1) and put into a kneader (planetary mixer) as a solvent. Kneaded with ion-exchanged water. The slurry is applied to the entire surface (both sides) of a long aluminum foil (1N30-H material, average thickness of about 15 μm) using a slit coater and dried (drying temperature 120 ° C., 1 minute) for corrosion resistance. A layer was formed. Thus, the positive electrode collector (Examples 1-17) of the form with which the whole surface of the base material made from aluminum was covered with the corrosion-resistant layer of the thickness shown in the column of "average thickness (micrometer)" of Table 1 Obtained. In addition, the value of average thickness represents the arithmetic average thickness of the corrosion-resistant layer provided per one side of a base material.

<Example 18>
A positive electrode current collector (Example 18) was obtained in the same manner as in Example 1 except that carboxymethyl cellulose (trade name “Selogen: BSH-6” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used as the binder.

<Example 19>
In this example, a slurry for forming a corrosion-resistant layer in a non-aqueous system was prepared. That is, the conductive material and polyvinylidene fluoride (PVdF) as a binder are weighed so that the mass ratio of these materials is 100: 5, and charged into a kneader, and N-methyl-2 as a solvent. -Kneaded with pyrrolidone (NMP) to prepare a slurry for forming a corrosion-resistant layer. Otherwise, in the same manner as in Example 1, a positive electrode current collector (Example 19) was obtained.

<Example 20>
Here, an aluminum foil (base material) itself was used as a positive electrode current collector (Example 20) without forming a corrosion-resistant layer.
The structure of the corrosion-resistant layer provided in the positive electrode current collector is summarized in Table 1 below.

[Confirmation of surface quality of corrosion-resistant layer]
The surface quality of the produced positive electrode current collector was confirmed. Here, the surface of the corrosion-resistant layer was observed with a scanning electron microscope (SEM), the number of aggregates (lumps) and pinholes having a diameter of 0.5 mm or more was counted, and the number of generations per 1000 cm ² was calculated. The results are shown in the columns of “Number of aggregates” and “Number of pinholes” in Table 1.

As is apparent from Table 1, Examples 13 and 14 in which the addition amount of polyoxyethylene styrenated phenyl ether was reduced to 0.08 parts by mass with respect to 100 parts by mass of the carbon material, and the addition amount of alginic acid was changed to the carbon material 100. In Example 9 and Example 15 in which the amount was increased to 12 parts by mass with respect to part by mass, many aggregates were generated. The cause of this is considered to be that the dispersibility of the carbon material is insufficient and the alginate is aggregated.
Further, Example 10 and Example 12 in which the addition amount of alginic acid was reduced to 0.1 parts by mass with respect to 100 parts by mass of the carbon material, and the addition amount of polyoxyethylene styrenated phenyl ether was 2 to 100 parts by mass of the carbon material. In Example 8 and Example 11 increased to 2 parts by mass, many pinholes were generated. From this result, it was found that if the proportion of alginic acid is too small, a sufficient corrosion-resistant layer (film) cannot be formed. Similar results were confirmed in Example 16 in which the thickness of the corrosion-resistant layer was 0.3 μm.

  A non-aqueous electrolyte secondary battery (here, a lithium ion secondary battery) was constructed using the produced positive electrode current collector in the following procedure.

<Preparation of positive electrode sheet>
First, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as a positive electrode active material and acetylene black as a conductive material (trade name “Denka Black (pressed product): FX35” manufactured by Denki Kagaku Kogyo Co., Ltd.) Carboxymethylcellulose as a thickener (trade name “Serogen: BSH-6” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and polytetrafluoroethylene as a binder (trade name “Fluon: AD911” manufactured by Asahi Kasei Corporation) ) Was weighed so that the mass ratio of these materials would be 100: 4: 2: 2, charged into a kneader, and kneaded with ion-exchanged water to prepare a positive electrode active material layer forming slurry. The prepared slurry had a pH of approximately 12.1. This slurry is applied in a strip shape with a width of 94 mm on both sides of the positive electrode current collectors according to Examples 1 to 20, and dried (drying temperature 120 ° C., 1 minute) and then subjected to a rolling process using a roll press. Thus, a positive electrode sheet (Example 1 to Example 20, total thickness: 170 μm, length: 4500 mm) having a positive electrode active material layer on both surfaces of the positive electrode current collector was obtained.

[Confirmation of surface quality of corrosion-resistant layer]
About the positive electrode active material layer of the produced positive electrode sheet, surface quality was confirmed similarly to the case of the said corrosion-resistant layer. Here, the number of occurrences of pinholes with a diameter of Φ0.3 mm or more, which is considered to be generation traces of hydrogen gas due to corrosion of the current collector, was counted, and the number of occurrences per 1000 cm ² was calculated. The results are shown in the column of “corrosion marks” in Table 1.

  As is clear from Table 1, the most corrosion marks were confirmed in Example 20 in which the corrosion-resistant layer was not provided. In Example 18 where CMC was used as the binder, approximately half of the corrosion marks were confirmed. Furthermore, corrosion marks were also confirmed in Examples 8 to 16 where the formation of aggregates and pinholes was confirmed in the confirmation of the surface quality of the corrosion-resistant layer. In contrast, in Example 19 using PVdF as a binder and Examples 1 to 7 according to the present invention, no significant corrosion was observed. From this, it was found that suitable corrosion resistance (alkali resistance) was imparted to the current collector.

  Next, natural graphite powder (C) as a negative electrode active material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC, trade name “Selogen: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.” as a thickener. BSH-6 ") was mixed with ion-exchanged water so that the mass ratio of these materials was 100: 1: 1 to prepare a slurry for forming a negative electrode active material layer. This slurry is applied in a strip shape with a width of 100 mm on both sides of a long copper foil (negative electrode current collector) having an average thickness of approximately 12 μm, dried (drying temperature 120 ° C., 1 minute), and then rolled using a roll press. By performing the treatment, a negative electrode sheet (total thickness: 150 μm, length: 4700 mm) having negative electrode active material layers on both surfaces of the negative electrode current collector was obtained.

<Construction of lithium ion secondary battery>
The positive electrode sheet and the negative electrode sheet produced above are combined with a separator sheet (here, alumina is included on one side of a three-layer base material (total thickness 20 μm) in which polypropylene (PP) is laminated on both sides of polyethylene (PE). A separator sheet with a porous heat-resistant layer in which a heat-resistant layer was formed was used, and the active material layers were arranged so as to face each other and wound in an elliptical shape. The wound body is formed into a flat shape by sandwiching it with a flat plate in a normal temperature (25 ° C.) environment and pressurizing (here, pressurizing for 2 minutes with a load of 4 kN / cm ² ). A rotating electrode body was produced. The positive electrode terminal and the negative electrode terminal were welded to the end portions (exposed portions of the positive electrode current collector plate and the negative electrode current collector plate) of the produced wound electrode body, respectively, and then placed in a rectangular battery case. There, a non-aqueous electrolyte (here, a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a volume ratio of 3: 4: 3, LiPF as a supporting salt) ₆ was dissolved at a concentration of 1.0 mol / L, and 125 g of a non-aqueous electrolyte solution in which cyclohexylbenzene (CHB) and biphenyl (BP) were added at a ratio of 1% by mass as gas generating agents was used. The solution was injected, the opening of the battery case was sealed, and a prismatic lithium ion secondary battery (rated capacity: 24.0 Ah) according to Examples 1 to 20 was constructed.

[Measurement of rated capacity (initial capacity)]
The rated capacity of the battery thus constructed was measured according to the following procedures 1 to 3 at a temperature of 25 ° C. and a voltage range of 3.0 V to 4.1 V.
[Procedure 1] After charging to 4.1 V with a constant current of 1 C, pause for 5 minutes.
[Procedure 2] After discharging to 3.0 V with a constant current of 1 C, pause for 5 minutes.
[Procedure 3] After charging to 4.1 V with a constant current of 1 C, charge at a constant voltage until the current value reaches 0.1 C, and then rest for 10 seconds.
[Procedure 4] After discharging to 3.0 V with a constant current of 1 C, constant voltage discharge until the current value reaches 0.1 C, and then rest for 10 seconds.
And the discharge capacity (CCCV discharge capacity) in the procedure 4 was made into the rated capacity (initial capacity). All the batteries of Examples 1 to 20 were confirmed to have a rated capacity.

[50 ° C cycle test]
The battery after the initial capacity check was subjected to a charge / discharge test of 1000 cycles according to the following steps 1 and 2 at a temperature of 50 ° C. and a voltage range of 3.0 V to 4.1 V.
[Step 1] After charging to 4.1 V with a constant current of 2 C, pause for 10 seconds.
[Step 2] After discharging to 3.0 V with a constant current of 2 C, pause for 10 seconds.
After the test, the discharge capacity (battery capacity after the cycle test) was measured in the temperature environment of 25 ° C. in the same manner as the measurement of the initial capacity, and the ratio “(battery capacity after the cycle test / initial capacity) × 100 That is, the capacity retention rate (%) was calculated. Here, the test was carried out with N = 5 for each example, and the arithmetic average value was obtained. The results are shown in the column of “Cycle test” in Table 1. FIG. 5 shows the relationship between the capacity retention rate (%) after the cycle test and the corrosion marks.

  As shown in Table 1 and FIG. 5, it was found that the corrosion marks and the cycle characteristics are generally correlated. For example, Examples 1 to 7 and 19 in which no corrosion marks were confirmed showed a high capacity retention rate of 85% or more (particularly 90% or more). In contrast, as the number of corrosion marks increased, the cycle characteristics tended to decrease, and in Example 20, the capacity retention rate decreased to approximately 55%. The reason is considered that the surface of the positive electrode current collector is corroded and the surface becomes uneven, and the positive electrode active material layer is floated or dropped, thereby increasing the resistance of the positive electrode. Such a result represents the effect of the present invention.

[0 ℃ high rate pulse cycle test]
Further, a high rate pulse cycle test was performed on the battery after the initial capacity confirmation at a temperature of 0 ° C. and a voltage range of 3.0 V to 4.1 V. Specifically, first, in an environment of 25 ° C., the battery was adjusted to a state of charge (SOC) of about 50% of the rated capacity. And this battery was subjected to a charge / discharge test of 50000 cycles in an environment of 0 ° C. according to the following steps 1 to 3.
[Step 1] Pulse charging is performed for 10 seconds at a constant current of 20C.
[Step 2] Pulse discharge is performed for 10 seconds at a constant current of 20C.
[Step 3] Pause for 30 seconds.
However, every time 100 cycles of the charge / discharge pattern consisting of steps 1 to 3, the SOC is adjusted to 50% by charging to SOC 50% with a constant current of 1C and then charging for 2.5 hours at the same voltage.
After the test, the discharge capacity (battery capacity after the low-temperature pulse cycle test) was measured in the temperature environment of 25 ° C. in the same manner as the above-mentioned initial capacity measurement. Capacity) × 100 ”, that is, capacity retention rate (%) was calculated. The results are shown in the column of “Low-temperature pulse cycle test” in Table 1. This result shows the durability when a large current load (input / output) such as pulse charging / discharging is repeated in a low temperature environment.

  As shown in Table 1, Example 20 in which the corrosion-resistant layer was not provided and Example 18 in which CMC was used as the binder showed a low capacity retention rate (approximately 65 to 66%). Moreover, Example 8 and Example 11 which increased the addition amount of polyoxyethylene styrenated phenyl ether with 2.2 mass parts with respect to 100 mass parts of carbon materials, and the addition amount of alginic acid with 12 mass parts with respect to 100 mass parts of carbon materials. Also in Example 9 and Example 15 which were increased in part, the capacity retention rate was 70% or less. Such a tendency was the same in Example 17 in which the thickness of the corrosion-resistant layer was 7 μm. This may be because the resistance component is increased by containing a large amount of polyoxyethylene styrenated phenyl ether and / or alginic acid. On the other hand, when the carbon material is 100 parts by mass, the ratio of alginic acid is 0.3 parts by mass or more and 10 parts by mass or less, and the ratio of polyoxyalkylene styrenated phenyl ether is 0.1 parts by mass or more. In Examples 1 to 7 which are 2 parts by mass or less, a good capacity retention rate of approximately 80% was obtained. Such a result represents the effect of the present invention.

[High temperature storage durability test]
Moreover, the high temperature storage durability test was done with respect to the battery after the said initial capacity confirmation. Specifically, the battery was first adjusted to a SOC of 100% in a temperature environment of 25 ° C. And this battery was preserve | saved for about 2400 hours (100 days) in a 60 degreeC thermostat.
After the test, the discharge capacity (battery capacity after the high temperature storage endurance test) was measured in the temperature environment of 25 ° C. in the same manner as the above initial capacity measurement. Capacity) × 100 ”, that is, capacity retention rate (%) was calculated. Here, each example was tested at N = 50, and the arithmetic average value was obtained. The results are shown in the column of “High temperature storage durability test” in Table 1.

  As shown in Table 1, Example 19 in which a corrosion-resistant layer was formed using PVdF showed the lowest capacity retention rate (approximately 70%). This may be due to the fact that the binder (PVdF) contained in the corrosion-resistant layer is swollen by the non-aqueous solvent, or the solvent (NMP) used for forming the slurry remains. In addition, Example 18 in which a corrosion-resistant layer was formed using CMC, Example 20 in which a corrosion-resistant layer was not provided, and the amount of alginic acid added when forming the corrosion-resistant layer was reduced to 0.1 parts by mass with respect to 100 parts by mass of the carbon material. In Examples 10 and 12, and Example 16 in which the thickness of the corrosion-resistant layer was 0.3 μm, the capacity retention rate was about 90%. This is probably because the current collector was not provided with suitable corrosion resistance (alkali resistance). Such a result represents the effect of the present invention.

  As mentioned above, although this invention was demonstrated in detail, the said embodiment is only an illustration and what changed and modified the above-mentioned specific example is included in the invention disclosed here.

10 nonaqueous electrolyte secondary battery 20 wound electrode body 30 positive electrode sheet (positive electrode)
32 Positive electrode current collector 32a Base material 32b Corrosion resistant layer 33 Carbon material 34 Alginic acid 35 Compound 36 having polyoxyalkylene styrenated phenyl ether structure Positive electrode active material layer 37 Positive electrode active material 38 Binder, thickener 40 Positive electrode terminal 43 Uncoated Part 50 Negative electrode sheet (negative electrode)
52 Negative electrode current collector 56 Negative electrode active material layer 60 Negative electrode terminal 70 Separator sheet (separator)
80 Battery case 82 Lid 84 Container body 85 Safety valve WL Winding shaft

Claims (6)

A current collector for a non-aqueous electrolyte secondary battery,
A metal base and a corrosion-resistant layer provided on the surface of the base;
The corrosion-resistant layer includes a carbon material, alginic acid, and a compound having a polyoxyalkylene styrenated phenyl ether structure,
Here, when the said carbon material is 100 mass parts, the ratio of the said alginic acid is 0.3 mass part or more and 10 mass parts or less, and the ratio of the compound which has the said polyoxyalkylene styrenated phenyl ether structure is 0.00. A current collector that is 1 part by mass or more and 2 parts by mass or less.   The current collector according to claim 1, wherein the corrosion-resistant layer has an average thickness of 0.5 μm or more and 6.5 μm or less.   The current collector according to claim 1 or 2, wherein the compound having a polyoxyalkylene styrenated phenyl ether structure is polyoxyethylene styrenated phenyl ether.   The nonaqueous electrolyte secondary battery provided with the electrode by which an active material layer is formed in the surface of the collector of any one of Claims 1-3, and a nonaqueous electrolyte. The electrode is a positive electrode;
The non-aqueous electrolyte secondary battery according to claim 4, wherein the active material layer includes at least a positive electrode active material and a water-soluble and / or water-dispersible polymer compound other than alginic acid.   The nonaqueous electrolyte secondary battery according to claim 5, wherein the polymer compound contained in the active material layer is a cellulose polymer and / or an ethylene polymer.

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