JP2009199964A - Manufacturing method for composite layer, control method, electrode, and power storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine a coating nature of a composite layer to a hole-opened collector surface. <P>SOLUTION: The composite layer is coated on the hole-opened collector surface. The hole opened on the collector surface is blocked by the composite agent at coating. In this manner, an electrode is formed by preparing a composite layer on the hole-opened collector surface, accordingly. The composite layer on the hole-opened collector surface is coated by forming in a slurry. Suitable coating nature for embedding the hole with a composite agent can be secured so that the range of shearing stress at certain shearing speed of the mixed composite layer is set to be an index at coating. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for an electrode material, and is particularly effective when applied to a composite layer provided on a current collector of an electrode.

  In recent years, environmental problems with respect to the atmosphere such as exhaust gas in the automobile society have been highlighted. Under such circumstances, development of environmentally friendly electric vehicles and the like is being carried out. In developing an electric vehicle, a power storage device as a power source is particularly actively developed. Various types of power storage devices have been proposed in place of conventional lead storage batteries.

  As power storage devices, power storage devices such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors are currently attracting attention. In such a power storage device, a current collector formed in a foil shape has been used. However, a porous foil current collector having a hole through which ions in the electrolyte can pass has been proposed.

An electrode is configured by providing a composite material for an electrode such as an active material in a predetermined layer thickness on such a perforated current collector. For example, Patent Document 1 describes an electrode manufacturing method in which a composite layer is applied to such a perforated current collector.
JP 2007-280922 A

  By making holes in the current collector used for the electrode as described above, for example, it is easy to pre-dope lithium ions in the negative electrode. That is, the holes of the current collector are ion passage holes. Such an electrode is manufactured by providing a composite material layer made of an active material or the like on a current collector surface having a hole.

  For example, a mixture layer made of an active material or the like is formed into a slurry, and is applied onto a perforated current collector in a wet state. Thereafter, the electrode is manufactured by drying. The coated composite material layer is required to uniformly enter all the holes opened in the current collector.

  However, depending on the composite material layer, there are cases where it can be appropriately coated on a current collector having the same aperture, and there are cases where it cannot be applied. For example, even in a composite material layer having the same composition, the coating properties on the current collector may differ only by changing the particle size of the active material used in the composite material layer. Depending on the composite material layer, various states may occur depending on whether or not it enters the hole formed in the current collector. If this state is overlooked and the electrode is manufactured, the resulting electrode itself will vary in cycle characteristics and the like.

  Until now, the applicability of the composite layer has been controlled by viscosity. At this time, the viscosity measured with a commercially available B-type viscometer was used. However, it has been found that viscosity management is not sufficient as described above. However, no suitable indicator has been found so far.

  In the past, only a characteristic value by a B-type viscometer or the like has been left as data for a composite layer that can be appropriately coated on a perforated current collector surface. The characteristic values and the like have not been grasped in relation to the coating properties of the composite material layer. Therefore, the judgment as to whether or not the composite material layer can be applied has not been surely understood unless the current collector is actually applied. In other words, on-site verification was necessary to determine the coating property of the composite layer.

  This state becomes a fatal obstacle at the stage of entering mass production. Some kind of index is needed to appropriately determine the composite layer that can be coated on the perforated current collector. In other words, it is required that it can be determined in advance whether or not coating is possible, instead of actually coating the current collector.

  An object of the present invention is to provide a technique for determining the applicability of a composite material layer to a perforated current collector.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  In this invention, the applicability | paintability to the electrical power collector of a composite material layer is judged by the shear stress of a composite material layer. In the present specification, the shear stress of the composite layer is defined as the stress generated in the fluid to which a force is applied from the outside. Moreover, the shear rate at the time of measuring such shear stress is defined as a velocity gradient in the fluid.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  In the present invention, by using the shear stress at the shear rate of the composite material layer as an index, appropriate application to the perforated current collector becomes possible. Therefore, it is possible to prevent production of defective electrodes based on poor coating of the composite layer. This facilitates mass production when applying a composite layer to the current collector.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is broadly related to electrodes. This is a technique related to an index for discriminating an appropriate electrode mixture layer when forming an electrode used in a power storage device. By using such an index, it is possible to perform appropriate coating that allows the composite material layer to enter a hole provided on the current collector surface when coating the current collector. That is, by adjusting the characteristics of the composite material layer so as to fall within the index, it is possible to appropriately apply the perforated current collector. Alternatively, the characteristics of the prepared composite material layer can be selected using such an index, and a composite material layer that can be appropriately applied to the current collector can be selected.

  Here, with regard to the coating property of the composite material layer, it is ideal that the coating is performed so that the holes provided in the current collector surface are 100% surely closed. However, for example, when 98% or more and 100% or less of the total number of holes is blocked with a composite layer during coating, it can be considered that it can be used sufficiently. If it is less than 98%, there is a risk of causing partial deterioration and inconvenience such as gas generation. Instead of the number of holes, it may be 98% or more and 100% or less of the total hole area (also referred to as open area). If it is less than 98%, there is a possibility that inconvenience such as gas generation may occur due to partial deterioration.

  Such standard coating that covers 98% or more of the total number of holes or 98% or more of the total hole area (opening area) with the composite layer may be referred to as “appropriate coating” in this specification.

  It has been found that the index of the composite layer that can be appropriately applied may be indicated by the shear stress at the shear rate of the composite layer. That is, it is only necessary to determine whether or not the shear stress at a predetermined shear rate in the composite material layer measured with a commercially available rheometer is within the range of the index. It has been found that if the stress at the time when the composite layer is sheared at a certain speed is within a predetermined range, it is possible to determine appropriate coating.

As an index, it can show in the range of the shear stress in at least two shear rates, for example. For example, as the shear rate, two points of 10 ⁻¹ / second and 10 ² / second can be selected. When the shear rate is 10 ⁻¹ / sec, the lower limit of the shear stress may be 1 Pa or more and the upper limit may be 10 Pa or less. Further, when the shear rate is 10 ² / sec, the lower limit of the shear stress may be 5 Pa or more and the upper limit may be 50 Pa or less.

  In specifying the ranges of the shear rate and shear stress, it is necessary to specify the temperature at the time of measurement. This is because the measurement temperature affects the shear rate and shear stress. Incidentally, the room temperature at the time of measurement is, for example, 25 ° C., and ± 0.5 ° C. is an allowable range. Moreover, in the measurement at this room temperature, the temperature of the compound material layer applied becomes the range of 20 to 25 degreeC, for example.

  Therefore, the values of the shear rate and shear stress in the above ranges may be specified, for example, by the temperature of the composite layer to be measured. For example, what is necessary is just to specify 20 degreeC. Or what is necessary is just to designate the temperature range at the time of the measurement of a compound material layer. For example, what is necessary is just to specify 20 degreeC or more and 25 degrees C or less.

  Alternatively, the room temperature at the time of measurement may be specified. For example, it may be specified as 25 ° C. Alternatively, a room temperature range at the time of measurement may be specified. For example, what is necessary is just to specify 24.5 degreeC or more and 25.5 degrees C or less.

  To be precise, it is preferable to specify the temperature of the composite layer to be applied. However, considering the efficiency at the production site, it is preferable to specify the temperature range rather than the specific temperature. Furthermore, it is preferable if the temperature can be specified at room temperature during measurement. Furthermore, it is more preferable if it can be specified in the temperature range of room temperature. For example, it is possible to assume that the temperature of the composite material layer has reached room temperature by placing the composite material layer coated in the room temperature environment at the time of measurement.

For example, as shown in FIG. 1, such a configuration can be easily understood by forming a graph in which one of orthogonal axes intersecting each other has a shear rate and the other axis has a shear stress. In the case shown in FIG. 1, the upper limit may be equal to or less than the line connecting the shear stresses of 10 Pa and 50 Pa at two shear rates of 10 ⁻¹ / sec and 10 ² / sec. The lower limit is, shear rate ^{10 -1} / sec, or if the 10 ² / shear stress in two points s 1Pa and 5Pa and the line connecting more. Incidentally, in the case of FIG. 1, it is sufficient to set the value at a temperature of 20 ° C. of the coated material layer to be coated.

  For example, the line connecting the two points indicating the upper limit and the lower limit may be a straight line as shown in FIG. However, it is also possible to take a finer shear rate between the two points and to connect an upper limit and a lower limit of the shear stress according to the shear rate. If the upper limit and the lower limit of a plurality of points are respectively connected, a line indicating the upper limit and a line indicating the lower limit are obtained. Of course, the line indicating the upper limit and the line indicating the lower limit may be curves other than a straight line.

Actually, it was measured by setting a plurality of finer shear rates between the shear rates of 10 ^-1 / sec and 10 ² / sec. As a result, it has been found that the linearity as shown in FIG. 1 is obtained for the upper and lower limits of the shear stress at different shear rates. The reason why the lower limit of the shear rate is selected to be 10 ^-1 / sec and the upper limit is set to 10 ² / sec is due to the sagging property of the composite material layer and the reason for leveling. Of course, a shear rate other than 10 ⁻¹ / sec and 10 ² / sec can be used as the basis for setting the shear stress range. In such a case, it may be considered that the line is not straight.

  Incidentally, sagging refers to a phenomenon in which an undried paint hangs down due to gravity, and leveling refers to the smoothness and thickness uniformity of the coating surface.

  In order to increase the accuracy, it may be shown in the range of shear stress at three or more shear rates. For example, the upper limit range may be equal to or less than a line connecting the upper limit ranges of shear stress at three or more shear rates. The lower limit range may be a range equal to or greater than a line connecting the lower limit ranges of the shear stress at three or more shear rates. In this way, it is possible to accurately indicate the range in which the coating property of the composite material layer is judged.

When the shear stress is outside the above range, the composite material layer cannot be appropriately applied. That is, when the shear rate 10Pa at 10 -1 ^/ sec, the shear rate exceeds point shear stress at 10 2 ^/ sec of the line connecting the two points of 50Pa is uncoated portions of such streaks may occur. Alternatively, there may be inconveniences such as unevenness in thickness and the inability to obtain a composite layer having a smooth surface. In addition, when the shear rate is less than a point on a straight line connecting the two points of 1 Pa at a shear rate of 10 ^-1 / sec and a shear rate of 10 ² / sec and a shear stress of 5 Pa, a mixture is formed in the hole provided in the current collector. The layer does not enter, and the leakage occurs. Alternatively, it is conceivable that the paint drips in an undried state, and a composite layer having a smooth surface cannot be obtained.

Inconvenience in such a case may be, for example, a streak or an omission at the time of coating the current collector layer on the current collector and can be clearly confirmed visually. FIG. 2 (a) schematically shows the state of the leakage, and FIG. 2 (b) schematically shows the state of the streak. When the shear stress of the composite layer is within the range of the above-mentioned index, for example, it is uniformly applied as shown in FIG.

  For example, in FIG. 2A, white spots are visible in the coated mixture layer on the current collector, but they are missing. For example, as shown in the photographs of FIGS. 3A and 3B, such omission may occur due to the absence of the composite material layer in some of the holes of the current collector.

  In FIGS. 2A to 2C, a current collector in which a composite material layer is applied to the center of a rectangular ground portion is shown and schematically shown so that streaks and leakage can be easily understood.

  That is, if the shear stress of the composite material layer is within the range of such an index, the composite material layer can be appropriately coated on the perforated current collector surface. The hole formed in the current collector can be closed with the composite material layer so as to meet the above-mentioned standard when the composite material layer is applied.

  In the case of a composite material layer having a shear stress outside the range of such an index, the hole formed in the current collector cannot be closed during coating. For example, streaks, missing spots and the like shown in FIGS. 2A and 2B are generated, and the mixture layer does not enter the holes of the current collector. Or the case where the coated composite material layer falls out of the hole and cannot properly close the hole occurs.

  One such indicator is related to the composition of the composite layer. That is, it seems to be related to the components constituting the composite layer, the component ratio, the average particle size of the components, the particle size distribution of the components, the viscosity of the slurry formed by mixing these components, and the like. At present, the contribution rate of these individual items to the indicators is unknown. However, the present inventors have found that when the total shear stress as the slurry is within the range of the above-mentioned index, it is possible to perform appropriate coating to close the holes of the perforated current collector.

  However, the coating property of the composite material layer may change depending on the aperture ratio opened in the current collector. Therefore, it has been confirmed that the above index is effective when the aperture ratio of the current collector is in the range of 8% to 60%. If the aperture ratio is less than 8%, pre-doping may not be performed smoothly, and if the aperture ratio exceeds 60%, there is a possibility that a problem in strength may occur.

  The holes provided in the current collector are preferably pre-doped more effectively by the permeation of lithium ions when the aperture ratio is 10% or more. However, if the aperture ratio is too high, the strength of the current collector is lowered, and therefore 10% or more and 60% or less are practical. More preferably, it is 40% or more and 60% or less. Therefore, the above index can be used for an aperture ratio of 40% or more and 60% or less where the pre-doping can be performed more effectively.

  The shear stress was measured as follows, for example. That is, the measurement was performed using a commercially available stress-controlled rheometer manufactured by HAAKE.

  In addition, even if the method of measuring shear stress or the method of defining shear stress is different from the present specification, it can be converted into the shear stress defined in this specification. The above indicators can be used. In such a case, if it falls within the numerical range of the shear stress referred to in this specification, it may be expressed differently from the shear stress referred to in this specification or may be regarded as the shear stress referred to in this specification. Absent.

  Moreover, what is necessary is just to perform using the coating apparatus, such as a die-coater and a comma coater, in the appropriate coating on the collector with a hole of a composite material layer. By using such a coating apparatus, for example, appropriate coating can be performed on a perforated current collector in a range of a layer thickness of 10 μm or more and 200 μm or less (one side). After the appropriate coating, the electrode can be manufactured by drying. If necessary, the coated composite layer may be pressed at a predetermined pressure after appropriate coating and before drying. The electrode thus manufactured can be applied to, for example, a power storage device.

  Examples of the power storage device include batteries such as lithium ion secondary batteries. For example, FIG. 4 shows a main configuration of a lithium ion secondary battery. As shown in FIG. 4, in the lithium ion secondary battery 10, a negative electrode 11 and a positive electrode 12 are stacked with a separator 13 interposed therebetween. An end where a plurality of negative electrodes 11 and positive electrodes 12 are laminated is formed in the negative electrode 11.

  The negative electrode 11 provided at the end is provided with a lithium electrode 14 that functions as a lithium ion supply source to the negative electrode with a separator 13 interposed therebetween. As shown in FIG. 4, the lithium electrode 14 has a configuration in which a metal lithium 14a is provided on a current collector 14b. Lithium ions eluted from the lithium electrode 14 are pre-doped into the negative electrode 11.

  In the negative electrode 11, an active material 11a for the negative electrode is provided on the current collector 11b. The negative electrode active material 11a is formed into a composite material for an electrode together with a binder or the like, and is applied to the surface of the current collector 11b with a predetermined layer thickness. For example, the current collector 11b has an aperture ratio of 60%. The shear stress of the composite layer provided on the current collector 11b is 10 Pa at a shear rate of 10 / sec, and is within the range of the coating property index of the composite layer of the present invention. .

  Further, in the positive electrode 12, an active material 12a for the positive electrode is provided on the current collector 12b. The positive electrode active material 12a is formed into a composite material for an electrode together with a binder or the like, and is applied to the surface of the current collector 12b with a predetermined layer thickness. For example, the current collector 12b has an aperture ratio of 40%. The shear stress of the composite layer provided on the current collector 12b is 10 Pa at a shear rate of 10 / sec, and is within the range of the coating property index of the composite layer of the present invention. .

  As described above, the electrode unit in which the lithium electrode 14 is disposed at the end and the negative electrode 11 and the positive electrode 12 are laminated with a separator interposed therebetween is configured in a battery by being immersed in an electrolyte solution (not shown). The

  In addition, the power storage device can be configured as a lithium ion capacitor as shown in FIG. In the lithium ion capacitor 100 as well, for example, as shown in the main configuration of FIG. 5, the negative electrode 110 and the positive electrode 120 are stacked with the separator 130 interposed therebetween. An end where the plurality of negative electrodes 110 and the positive electrode 120 are stacked is formed in the negative electrode 110.

  The negative electrode 110 provided at the end is provided with a lithium electrode 140 that is interposed between the separators 130 and functions as a lithium ion supply source to the negative electrode. As shown in FIG. 5, the lithium electrode 140 has a configuration in which a metal lithium 140a is provided on a current collector 140b. Lithium ions eluted from the lithium electrode 140 are pre-doped into the negative electrode 110.

  In the negative electrode 110, an active material 110a for the negative electrode is provided on the current collector 110b. The negative electrode active material 110a is formed into a composite material for an electrode together with a binder or the like, and is applied to the surface of the current collector 110b with a predetermined layer thickness. For example, the current collector 110b has an aperture ratio of 60%. The shear stress of the composite layer provided on the current collector 110b is 10 Pa at a shear rate of 10 / sec, and is within the range of the coating property index of the composite layer of the present invention. .

  In the positive electrode 120, a positive electrode active material 120a is provided on a current collector 120b. The positive electrode active material 120a is formed into a composite material for an electrode together with a binder and the like, and is applied to the surface of the current collector 120b with a predetermined layer thickness. For example, the current collector 120b has an aperture ratio of 40%. The shear stress of the composite layer provided on the current collector 120b is 10 Pa at a shear rate of 10 / sec, and is within the range of the coating property index of the composite layer of the present invention. .

  Furthermore, in the lithium ion capacitor having the above-described configuration, the “positive electrode” refers to the pole on the side where current flows out during discharge, and the “negative electrode” refers to the pole on the side where current flows in during discharge.

  The potential of the positive electrode and the negative electrode after short-circuiting the negative electrode and the positive electrode is preferably, for example, 2.0 V or less. In the lithium ion capacitor of the present invention, the potential of the positive electrode after the positive electrode and the negative electrode are short-circuited by doping of the negative electrode, the positive electrode, or lithium ions to the negative electrode and the positive electrode is preferably set to 2.0 V or less, for example. is necessary. In this way, the capacity is improved.

  In the lithium ion capacitor of the present invention, it is preferable that the electrostatic capacity per unit weight of the negative electrode active material is set to 3 times or more of the electrostatic capacity per unit weight of the positive electrode active material. Furthermore, it is preferable to set the weight of the positive electrode active material to be larger than the weight of the negative electrode active material. By adopting such a configuration, a high voltage and high capacity lithium ion capacitor can be obtained.

  In the above description, a stacked cell configuration is shown, but other cell configurations may be used. A power storage device such as a lithium ion secondary battery or a lithium ion capacitor can also be configured as, for example, a cylindrical cell in which a strip-like positive electrode and a negative electrode are wound through a separator. Or you may comprise in the square cell which laminated | stacked three or more layers of each of the plate-shaped positive electrode and the negative electrode through the separator. Further, a plate-like positive electrode and a negative electrode may be laminated in three or more layers with a separator interposed therebetween, and a large-capacity cell such as a film-type cell enclosed in an exterior film may be configured.

  In the power storage device, a current collector having a hole penetrating the front and back is used for the electrode. On the current collector, a composite material layer made of an active material layer or the like whose coatability is confirmed by the index is provided. 3 and 4 show the case where the composite layer is applied to both sides of the perforated current collector, it is of course possible to apply only on one side.

  In the above description, a lithium ion secondary battery and a lithium ion capacitor have been described as examples of a power storage device including an electrode to which a composite layer that can be appropriately applied is applied. However, as long as a perforated current collector is used, a battery other than the above, an electric double layer capacitor, and the like can be naturally applied.

  As the current collector used in the present invention, for example, aluminum or stainless steel can be used for the positive electrode current collector, and stainless steel, copper, nickel or the like can be used for the negative electrode current collector. Such a current collector is perforated to form a conductive porous body. A metal porous body such as a stainless mesh can be used. The current collector used for the lithium ion supply source may be the same as that used for the positive electrode and negative electrode current collector, but of course, one that does not react with the lithium ion supply source can be used.

  The holes provided in the current collector may be formed, for example, as a metal lath such as an expanded metal, a wire lath, a punching metal, an etching foil, an electrolytic etching foil, a three-dimensionally processed (3D) foil, or the like.

Strictly speaking, the hole of the current collector is a hole having a diameter of 100 μm or more and 1 mm or less in the case of lithium ion, although it depends on the ion species to be passed. As described above, the number of holes having such a diameter may be provided in the range of, for example, 50 / cm ^{2 to} 5000 / cm ² . If the number of holes is more than 5000 / cm ² , for example, the time required for pre-doping is shortened. However, the strength is inferior. Also, if the number of holes is less than 50 / cm ² , the time required for pre-doping will be required even if the strength is satisfactory. The appropriate aperture ratio is preferably 40% or more and 60% or less. With respect to the opening ratio of 40% or more and 60% or less, appropriate coating can be performed on the apertured current collector surface within the index range of the shear stress of the composite material layer.

  Moreover, the composite material layer used is comprised with solvents, such as an active material, a binder, a conductive support material as needed, and water, and is formed in a slurry, for example. The active material used for the composite layer is appropriately selected and used in accordance with the type of power storage device and the type of electrode. For example, when the power storage device is a lithium ion secondary battery, the following can be used as the positive electrode active material. For example, a material broadly includes an oxide of at least one metal element selected from Group V elements and Group VI elements of the Periodic Table. Examples of the metal oxide include vanadium oxide (vanadium oxide) and niobium oxide. In particular, vanadium pentoxide is preferable.

Even in such vanadium oxide, for example, vanadium pentoxide (V ₂ O ₅ ) forms a single layer by spreading a pentahedral unit having VO ₅ as a unit in a two-dimensional direction by a covalent bond. By laminating these layers, a layered structure is formed as a whole. Lithium ions can be doped between the layers.

  In the case of the negative electrode of a lithium ion secondary battery, for example, a carbon material that can occlude and release lithium ions such as graphite and PAS can be used. A lithium-based material can also be used. Such lithium-based materials include lithium-based metal materials such as metallic lithium and lithium alloys (eg, Li-Al alloys), intermetallic compound materials of metals and metallic lithium such as tin and silicon, and lithium such as lithium nitride. Compounds can be used.

  Furthermore, a carbon material that can be doped or dedoped with lithium ions can also be used. In such a case, by separately providing a lithium electrode, lithium ions are pre-doped from the lithium electrode to the negative electrode during initial charging. As the lithium ion supply source, metallic lithium or a lithium-aluminum alloy can be used. That is, any substance that contains at least lithium element and can supply lithium ions can be used.

For example, when the power storage device is a lithium ion capacitor, the active material used for the positive electrode is reversibly doped with an anion such as BF ₄ ⁻ , PF ₆ ^−, etc., in which lithium ions and lithium ions form a pair. Anything is possible. Examples of the positive electrode active material include activated carbon, conductive polymer, polyacene-based material, and the like. In particular, it is preferable to use activated carbon that has been subjected to an activation treatment with an alkali such as potassium hydroxide, for example, because the specific surface area is large compared to that that has not been activated.

  Moreover, as a negative electrode active material of a lithium ion capacitor, for example, graphite, a carbon-based material, a polyacene-based material, or the like can be used. Examples of the carbon-based material include non-graphitizable carbon materials. Examples of the polyacene-based substance include PAS that is an insoluble and infusible substrate having a polyacene-based skeleton. Any of the negative electrode active materials can be reversibly doped with lithium ions.

  During initial charging, lithium ions are pre-doped into the negative electrode. As the lithium ion supply source used in such a case, metallic lithium or a lithium-aluminum alloy can be used. That is, any substance that contains at least lithium element and can supply lithium ions can be used.

  Moreover, as a binder used for a compound material layer, binder resins, such as a rubber-type binder or a fluorine resin, a thermoplastic resin, an acrylic resin, can be used, for example. Examples of the rubber binder include SBR and NBR which are diene polymers. Examples of the fluorine resin include polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PDVF). Examples of the thermoplastic resin include polypropylene and polyethylene. Examples of the acrylic resin include 2-ethylhexyl acrylate, methacrylic acid / acrylonitrile / ethylene glycol dimethacrylate copolymer, and the like.

  When the positive electrode active material used in the lithium ion secondary battery is, for example, vanadium oxide, it is soluble in water. Therefore, it is necessary to disperse the binder by mixing it with a non-aqueous solvent.

  Furthermore, the conductive support material used for a compound material layer is mixed as needed. Examples of such conductive aids include conductive carbon such as ketjen black, metals such as copper, iron, silver, nickel, palladium, gold, platinum, indium and tungsten, and conductive metal oxides such as indium oxide and tin oxide. And the like.

  What is necessary is just to form the said active material, a binder, and the conductive support material as needed into a slurry using solvents, such as water and N-methylpyrrolidone, and apply | coat on a collector with predetermined layer thickness. What is necessary is just to apply a pressure of 50 MPa, for example, and to compress in the coated state as needed. Thereafter, for example, it may be vacuum dried at 120 to 250 ° C. for 12 to 24 hours. In this way, an electrode can be manufactured.

The electrode having such a configuration is appropriately selected according to the power storage device, and is provided, for example, via an electrolytic solution. An electrolyte is dissolved in the electrolytic solution. For example, in a lithium ion secondary battery, the electrolytes include CF ₃ SO ₃ Li, C ₄ F ₉ SO ₈ Li, (CF ₃ SO ₂ ) ₂ NLi, (CF ₃ SO ₂ ) ₃ CLi, LiBF ₄ , LiPF ₆ Lithium salts such as LiClO ₄ can be used. Such an electrolyte is dissolved in, for example, a non-aqueous solvent.

  Examples of non-aqueous solvents include chain carbonates, cyclic carbonates, cyclic esters, nitrile compounds, acid anhydrides, amide compounds, phosphate compounds, amine compounds, and the like. More specifically, for example, ethylene carbonate, diethyl carbonate (DEC), propylene carbonate, dimethoxyethane, γ-butyrolactone, n-methylpyrrolidinone, N, N′-dimethylacetamide, acetonitrile, or propylene carbonate and dimethoxyethane Examples thereof include a mixture and a mixture of sulfolane and tetrahydrofuran.

  The electrolyte layer interposed between the positive electrode and the negative electrode may be an electrolyte solution of a non-aqueous solvent in which the electrolyte is dissolved as described above, or a polymer gel (polymer gel electrolyte) containing this electrolyte solution It does not matter. In short, any material that smoothly supports the movement of lithium ions between the positive electrode and the negative electrode may be used.

  On the other hand, in the case of a lithium ion capacitor, for example, an aprotic organic solvent can be used as the electrolytic solution. The aprotic organic solvent forms an aprotic organic solvent electrolyte solution. Examples thereof include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran, dioxolane, methylene chloride, sulfolane and the like. Furthermore, you may use the liquid mixture which mixed 2 or more types of these aprotic organic solvents.

As an electrolyte to be used, any electrolyte that can generate lithium ions can be used. Examples thereof include LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiPF ₆ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) _{2 and the} like.

  The said index concerning this invention can be used for the parameter | index as a target value in composite-material layer manufacture, for example. That is, the shear stress of the composite material layer as a slurry to be coated on the perforated current collector is adjusted by appropriately adjusting the component ratio of each of the composite material layers, the particle size, or the mixing time. Prepare to be within index.

When the shear rate is taken on one axis and the shear stress is taken on the other axis, the value of the composite layer indicated by the coordinates (shear rate, shear stress) should be in the following range. A line connecting coordinates A (10 ^-1 / second, 1 Pa), coordinates B (10 ² / second, 5 Pa) shown in FIG. 1, coordinates C (10 ² / second, 50 Pa), coordinates D (10 ^-1 / It suffices to be within a range sandwiched between lines connecting seconds, 10 Pa). A line connecting coordinates A (10 ^-1 / sec, 1 Pa) and coordinates B (10 ² / sec, 5 Pa) is a line indicating a lower limit. The line connecting the coordinates C (10 ² / sec, 50 Pa) and the coordinates D (10 ⁻¹ / sec, 10 Pa) is a line indicating the upper limit.

  The shear stress at a shear rate other than the above shear rate is, for example, extrapolated from a straight line connecting points A and B, and extrapolated from a straight line connecting points D and C. Each may be determined and used as an index.

Alternatively, the produced composite material layer can also be used as an index for selecting later by coating properties. For example, a composite material layer having a plurality of compositions is manufactured in a trial production or the like in consideration of electrical characteristics. Among such composite material layers, a composite material layer that can be applied to the perforated current collector is selected based on the shear stress. That is, a line connecting coordinates A (10 ⁻¹ / sec, 1 Pa), coordinates B (10 ² / sec, 5 Pa) shown in FIG. 1, coordinates C (10 ² / sec, 50 Pa), coordinates D (10 ⁻¹ ). If it is within the range between the lines connecting the two lines per second and 10 Pa), it may be determined that coating is possible. Such an indicator can be used effectively when the coating property cannot be adjusted in advance by combining the composite layers.

  Alternatively, the composite material layer that can be appropriately coated may be further reclassified based on ease of application or the like. The composite material layer that can be appropriately coated is determined, for example, within the range between the lines. However, even with the same appropriate coatability, there may be differences in ease of application. Then, it can classify | categorize further by the difference of this ease of painting. That is, within the same coating property, it is possible to classify as easy to apply, such as very easy to apply, normal, and slightly difficult to apply. What is necessary is just to carry out storage management of the manufactured composite material layer with such ease of application.

  Furthermore, the ease of painting may be displayed in numerical expression if possible. For example, as long as classification is possible as in the index of the present invention, a numerical value range of shear stress may be set in accordance with ease of application with shear stress measured at a certain shear rate.

  In this way, it is important to classify the composite layers according to the ease of application. Such ease of coating is an extremely important factor for man-hours in mass production. What is necessary is just to store a compound material layer according to the case of coating easily. At the time of actual proper coating, select a mixture layer of the same ease of application from the mixture layers further classified by ease of application within the range of appropriate coating, and apply a uniform level be able to. In this way, production efficiency can be improved.

  In addition, it is fully conceivable that the coating property affects the drying property after appropriate coating in relation to the component composition of the composite material layer. In that case, the composite layer may be classified based on the shearing stress that is an index for determining appropriate coating properties, and in addition, a classification based on drying properties may be added.

  Furthermore, you may add the said classification | category together with the parameter | index concerning this invention as a management item of a composite material layer. That is, the composite material layer is broadly classified by the coating property by such an index, and further classified by the ease of coating. Furthermore, it may be managed so that a suitable mixture layer can be appropriately selected by performing a small classification based on drying properties.

  Next, the use of the shear stress described in the above embodiment as an index will be described more specifically using examples. Needless to say, the present invention is not limited to the following examples.

Example 1
[Production of Negative Electrode] Furfuryl alcohol, which is a raw material of furan resin charcoal, was held at 60 ° C. for 24 hours to cure the resin, thereby obtaining a black resin. The obtained black resin was heated in a static electric furnace to 1200 ° C. in a nitrogen atmosphere over 3 hours, and held at that temperature for 2 hours. After cooling by cooling, the sample taken out was pulverized with a ball mill. The sample which is non-graphitizable carbon powder (hydrogen atom / carbon atom = 0.008) of D50% (50% volume cumulative diameter) = 5.0 μm was obtained by pulverization.

Next, 100 parts by weight of the sample was mixed with a solution obtained by dissolving 10 parts by weight of polyvinylidene fluoride powder in 80 parts by weight of N-methylpyrrolidone. And three types of negative electrode slurries 1, 2, and 3 were obtained by changing mixing conditions. As the physical properties of the slurry, the respective shear stresses at shear rates of 10 ^-1 / second and 10 ² / second were determined. The results are shown in FIG. Incidentally, the values shown in FIG. 6 are values measured at an actual temperature of the slurry of 20 ° C.

  The negative electrode slurries 1, 2, and 3 were uniformly coated on both surfaces of a negative electrode current collector made of a copper expanded metal having a thickness of 32 μm (opening ratio: 50%) with a die coater. Then, after drying and pressing, negative electrodes 1, 2, and 3 having a thickness of 70 μm were obtained. The surface states of the obtained negative electrodes 1, 2, and 3 were observed, and the presence or absence of defects (missing, streaks) was observed. The result is shown in FIG.

The weight per unit area of the negative electrode active material sampled from the entire coating area and averaged was 4.0 mg / cm ² . The basis weight is a value obtained by dividing the amount of the negative electrode active material applied to the current collector by the area including both the front and back surfaces of the negative electrode.

[Production of Positive Electrode] A composition comprising 85 parts by weight of commercially available activated carbon powder having a specific surface area of 2000 m ² / g, 5 parts by weight of acetylene black powder, 6 parts by weight of an acrylic resin binder, 4 parts by weight of carboxymethyl cellulose and 200 parts by weight of water. Mixed. And three types of positive electrode slurries 1, 2, and 3 were obtained by changing mixing conditions. As the physical properties of the slurry, the respective shear stresses at shear rates of 10 ^-1 / second and 10 ² / second were determined. The results are shown in FIG.

  The positive electrode slurries 1, 2, and 3 were evenly coated with a die coater on both surfaces of a positive electrode current collector made of an aluminum expanded metal having a thickness of 35 μm (opening ratio: 50%). Then, after drying and pressing, positive electrodes 1, 2, and 3 having a thickness of 129 μm were obtained. The surface states of the obtained positive electrodes 1, 2, and 3 were observed, and the presence or absence of defects (missing, streaks) was observed. The result is shown in FIG.

The basis weight of the positive electrode active material sampled from the entire coating area and averaged was 3.5 mg / cm ² . The basis weight is an area including both the front and back surfaces of the positive electrode and is a value obtained by dividing the amount of the positive electrode active material applied to the current collector.

[Preparation of Tripolar Laminate Unit] Eleven negative electrodes 1 were cut into 6.0 × 7.5 cm ² (excluding terminal welds). In addition, 10 positive electrodes 1 were cut into 5.8 × 7.3 cm ² (excluding terminal welds). As the separator, a cellulose / rayon mixed nonwoven fabric having a thickness of 35 μm was used. Through the separator, the positive electrode current collector and the negative electrode current collector were arranged so that the terminal welds thereof were on opposite sides, and the positive electrode 1 and the negative electrode 1 were alternately laminated.

  In addition, it laminated | stacked so that the outermost part of an electrode might become the negative electrode 1. FIG. Separators were placed on the top and bottom and four sides were taped. The terminal welded portion (10 sheets) of the positive electrode current collector and the terminal welded portion (11 sheets) of the negative electrode current collector were respectively connected to an aluminum positive electrode terminal and a copper negative electrode terminal having a width of 50 mm, a length of 50 mm, and a thickness of 0.2 mm. Ultrasonic welding. In this way, an electrode laminate unit 1 was obtained.

  Moreover, the electrode laminated unit 2 and the electrode laminated unit 3 were obtained in the same manner except that the positive electrode 2 and the negative electrode 2 and the positive electrode 3 and the negative electrode 3 were used.

  As the lithium electrode, a metal lithium foil bonded to a stainless steel net having a thickness of 80 μm was used. One lithium electrode was disposed on each of the electrode laminate unit 1, the electrode laminate unit 2, and the electrode laminate unit 3 so as to completely face the outermost negative electrode. In this way, the three-pole laminated unit 1, the three-pole laminated unit 2, and the three-pole laminated unit 3 were obtained. The terminal welding part of the lithium electrode current collector was resistance welded to the negative electrode terminal welding part.

  [Production of Cell and Impregnation with Electrolyte] Each of the above-mentioned three-pole laminated units 1, 2, and 3 is placed inside a 3.5 mm laminated film deep-drawn to match the shape of the three-pole laminated units 1, 2, and 3. did. The three sides of the lower and side portions of the laminate film were heat-sealed.

Subsequently, a funnel was inserted into the remaining side where heat fusion was not performed, and 15 g of a propylene carbonate solution as an electrolytic solution was injected with a spoid. Such a propylene carbonate solution was prepared by dissolving LiPF ₆ to a concentration of 1 mol / L with respect to propylene carbonate. Thereafter, the remaining one side was fused under reduced pressure to assemble five film-type cells 1, 2, and 3 each. In addition, the metallic lithium arrange | positioned in a cell is equivalent to 500 mAh / g per negative electrode active material weight.

  [Initial Evaluation of Cell] After leaving for 20 days after impregnation with the electrolytic solution, each of the film type cells 1, 2, and 3 was disassembled. Both cells were completely free of metallic lithium. Accordingly, it was determined that 500 mAh / g of lithium ions was previously doped per unit weight of the negative electrode active material.

  [Evaluation of cell characteristics] The battery was charged at a constant current of 1000 mA until the cell voltage reached 3.8V. After that, constant current-constant voltage charging for applying a constant voltage of 3.8 V was performed for 30 minutes. Next, the battery was discharged at a constant current of 500 mA until the cell voltage reached 2.2V. This cycle of 3.8V-2.2V was repeated, and the cell capacity and energy density in the 10th discharge were evaluated.

  Subsequently, after being left in a constant temperature bath at 60 ° C., a voltage of 3.8 V was continuously applied, and after 1000 hours, the temperature was returned to room temperature to evaluate the cell capacity. The results are shown in FIG. 7 together with the capacity retention after the 3.8 V application test at 60 ° C. However, the data is an average of 3 cells.

  The discharge capacities of the film type cells 1, 2, and 3 were almost equal as shown in FIG. However, the film-type cell 1 without defects was slightly larger. Further, the capacity retention after 1000 hours was lower in the film type cells 2 and 3. This is presumably because the film-type cells 2 and 3 were partially deteriorated because of the use of electrodes with missing or streaks. In addition, it was also confirmed that the film-type cell 1 was better than the film-type cells 2 and 3 in terms of capacity retention.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiments and examples. However, the present invention is not limited to the above-described embodiments and examples, and does not depart from the spirit of the invention. It goes without saying that various changes can be made.

  INDUSTRIAL APPLICABILITY The present invention can be effectively used in the field of determining the appropriate coatability of a composite material layer to a perforated current collector used for an electrode of a power storage device.

It is explanatory drawing which shows the parameter | index of the coating property of the compound material layer concerning this invention. (A) is an omission, (b) is an explanatory view schematically showing an example of each defective coating of streaks, and (c) is an explanatory diagram schematically showing an example of appropriate coating. (A), (b) is the microscope enlarged photograph which showed a mode that a compound-material layer did not enter into the hole of a collector. It is a block diagram which shows typically the structural example of the electrical storage apparatus which has an electrode to which this invention is applied. It is a block diagram which shows typically the structural example of the electrical storage apparatus which has an electrode to which this invention is applied. It is explanatory drawing which shows the result which judged the electrode using the parameter | index of the coating property of this invention. It is explanatory drawing which shows evaluation of the cell using the electrode which agree | coincides with the parameter | index of the coating property of this invention, and the electrode which does not correspond.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Lithium ion secondary battery 11 Negative electrode 11a Active material 11b Current collector 12 Positive electrode 12a Active material 12b Current collector 13 Separator 14 Lithium electrode 14a Metal lithium 14b Current collector 100 Lithium ion capacitor 110 Negative electrode 110a Active material 110b Current collector 120 Positive electrode 120a Active material 120b Current collector 130 Separator 140 Lithium electrode 140a Metallic lithium 140b Current collector

Claims (9)

A method for producing a composite layer for an electrode provided on a current collector having a hole,
A method for producing a composite material layer, comprising determining the applicability of the composite material layer to the current collector using the shear stress of the composite material layer as an index. In the manufacturing method of the compound material layer of Claim 1,
The said shear stress is shown in the range which has the upper limit and lower limit corresponding to a shear rate, The manufacturing method of the composite material layer characterized by the above-mentioned. In the manufacturing method of the composite material layer of Claim 1 or 2,
The shear stress is a relative relationship connecting the coordinates corresponding to the different shear rates of different coordinates (shear rate, shear stress) when one intersecting axis is a shear rate and the other axis is a shear stress. It is shown as a value within the range sandwiched between the lines to be processed. In the manufacturing method of the composite material layer of Claim 3,
The coordinates of the plurality of points are (10 ⁻¹ / sec, 1 Pa), (10 ² / sec, 5 Pa), (10 ² / sec, 50 Pa), (10 ⁻¹ / sec, 10 Pa), A method for manufacturing a composite material layer. In the manufacturing method of the composite material layer of any one of Claims 1-4,
Instead of the shear stress of the composite material layer, or together with the index of the shear stress,
A method for producing a composite layer, wherein an index different from the shear stress obtained based on the index of the shear stress is used. A method for managing a composite layer,
A method for managing a composite material layer, comprising managing the shear stress of the composite material layer as an index. An electrode used in a power storage device,
Either of the manufacturing method of the composite material layer according to any one of claims 1 to 5 or the management method of the composite material layer according to claim 6 is applied to the electrode. Electrode. A power storage device provided with an electrode,
The power storage device according to claim 7, wherein the electrode according to claim 7 is used. The power storage device according to claim 8,
The power storage device is a lithium ion secondary battery or a lithium ion capacitor.