JP2011253684A - Battery manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery manufacturing method, by which in a battery with a porous layer formed on a surface of at least one of an electrode and a separator, exfoliation of the porous layer can be suppressed further.SOLUTION: The battery manufacturing method that the invention offers is a method for manufacturing a battery with a porous layer including inorganic filler and binder and formed on a surface of at least one of an electrode and a separator. The battery manufacturing method includes: a first dispersion step (S12) for mechanically dispersing inorganic filler in solvent thereby to form an inorganic filler coating material; a second dispersion step (S14) for mechanically dispersing binder in the inorganic filler coating material thereby to form a coating material for porous layer formation; and a step (S20) for applying the coating material for porous layer formation to a surface of at least one of an electrode and a separator and drying it thereby to form a porous layer. In the method, the dispersion force for mechanically dispersing the binder in the second dispersion step is set to be smaller than the dispersion force for mechanically dispersing the inorganic filler in the first dispersion step.

Description

  The present invention relates to a battery manufacturing method, and more particularly to a battery manufacturing method in which a porous layer containing an inorganic filler and a binder is formed on at least one surface of an electrode and a separator.

  In recent years, lithium-ion batteries, nickel-metal hydride batteries, and other secondary batteries have become increasingly important as power sources for vehicles or as power sources for personal computers and portable terminals. In particular, a lithium secondary battery that is lightweight and has a high energy density is expected to be preferably used as a high-output power source for mounting on a vehicle.

  In this type of lithium secondary battery, a separator is provided between the positive electrode and the negative electrode. This separator ensures insulation between the positive and negative electrodes. In a battery having such a configuration, when a conductive foreign material such as a metal is mixed in the battery, it is assumed that the foreign material penetrates the separator and bridges between the positive and negative electrodes to induce an internal short circuit. In order to prevent such an internal short circuit, it has been studied to form a heat-resistant porous layer made of an inorganic filler on the surface of either the positive electrode or the separator. For example, Patent Document 1 discloses a secondary battery in which a porous film containing filler fine particles and a binder (binder) is formed on the surfaces of positive and negative electrodes or a separator. In this publication, the production of the porous film is carried out by preparing a slurry in which filler fine particles and a binder are dispersed and mixed by a thin film swirling mixer, and applying and drying the slurry on the positive and negative electrodes or the surface of the separator. Patent documents 2-6 are mentioned as other conventional technology about this kind of porous layer.

JP 2006-164596 A International Publication No. 2006/038532 Pamphlet JP 2005-222780 A JP 2007-038643 A JP 2002-225418 A JP 2007-273123 A

  However, when the filler fine particles and the binder are dispersed and mixed as in Patent Document 1, the binder is destroyed by collision with the hard filler fine particles having a small particle size, and the binding force is reduced. In some cases, the adhesive strength of the porous layer formed by using the material decreases. If the adhesive strength of the porous layer is lowered, the porous layer is peeled off during repeated charging and discharging, and the internal short circuit of the battery, which is the original purpose, cannot be prevented. In order to suppress such exfoliation of the porous layer, it is conceivable to increase the amount of binder in the porous layer, but as the amount of binder added increases, the porosity of the porous layer decreases, so the high rate characteristics Can be a factor of lowering.

  The present invention has been made in view of the above points, and its main object is to manufacture a battery that can further prevent the peeling of the porous layer in a battery in which the porous layer is formed on at least one surface of the electrode and the separator. Is to provide a method.

  The manufacturing method provided by the present invention is a method for manufacturing a battery in which a porous layer containing an inorganic filler and a binder is formed on at least one surface of an electrode and a separator, and the inorganic filler is mechanically dispersed in a solvent. A first dispersion step of forming an inorganic filler coating, a second dispersion step of forming a porous layer forming coating by mechanically dispersing a binder in the inorganic filler coating, and the porous layer forming coating. And a step of forming a porous layer by applying and drying on at least one surface of an electrode and a separator. Here, the dispersion force for mechanically dispersing the binder in the second dispersion step is set to be smaller than the dispersion force for mechanically dispersing the inorganic filler in the first dispersion step. To do.

  In the manufacturing method according to the present invention, prior to the addition of the binder, first, an inorganic filler is dispersed in a solvent to form an inorganic filler paint (first dispersion step), and then the binder is added to the inorganic filler paint to form a first. The binder is dispersed with a weaker force than the dispersion step (second dispersion step). In this way, the dispersion of the inorganic filler and the binder are separately performed, and the relationship between the dispersion forces of the two steps (first dispersion step> second dispersion step) is appropriately adjusted, thereby colliding with the inorganic filler. Thus, the porous layer-forming coating material can be produced with extremely good dispersibility of the inorganic filler and the binder (that is, the inorganic filler and the binder are uniformly dispersed) without destroying the binder. By using such a coating material for forming a porous layer, it is possible to manufacture a battery including a porous layer having good adhesion to an electrode or a separator.

  In a preferred embodiment of the production method disclosed herein, the dispersion of the inorganic filler in the first dispersion step and the dispersion of the binder in the second dispersion step are performed using the same rotary disperser, and the first The rotational speed of the rotary disperser in the second dispersion step is made smaller than the rotational speed of the rotary disperser in the first dispersion step. Thereby, the relationship of the dispersion force as described above (first dispersion step> second dispersion step) can be controlled more easily.

  In a preferred aspect of the production method disclosed herein, the dispersion of the inorganic filler in the first dispersion step and the dispersion of the binder in the second dispersion step are performed using the same ultrasonic disperser, and the first The ultrasonic amplitude of the ultrasonic dispersion machine in the 2 dispersion step is made smaller than the ultrasonic amplitude of the ultrasonic dispersion machine in the first dispersion step. Thereby, the relationship of the dispersion force as described above (first dispersion step> second dispersion step) can be controlled more easily.

  In a preferred aspect of the production method disclosed herein, the dispersion treatment time of the second dispersion step is made shorter than the dispersion treatment time of the first dispersion step. In this case, the destruction of the binder due to the collision with the inorganic filler is more effectively suppressed, and a porous layer with better adhesion to the electrode or the separator can be obtained.

  In a preferred embodiment of the production method disclosed herein, the dispersion of the inorganic filler in the first dispersion step and the dispersion of the binder in the second dispersion step are performed using different dispersers. In this case, by selecting a disperser having a much smaller dispersion force in the second dispersion step, the above-described dispersion force relationship (first dispersion step> second dispersion step) can be more easily controlled and the same Since the destruction of the binder is more effectively suppressed as compared with the case of using this disperser, a porous layer with better adhesion to the electrode or the separator can be obtained.

  In a preferred embodiment of the production method disclosed herein, metal compound particles having an average particle size of 0.3 μm to 2.0 μm are used as the inorganic filler. Such a hard metal compound with a small particle size has desirable properties (such as heat resistance, insulation and porosity of the porous layer) as a constituent material of the porous layer, while destroying the binder by collision during dispersion. It is particularly beneficial to apply the configuration of the present invention because it is easy.

  In a preferred embodiment of the production method disclosed herein, the electrodes are a positive electrode and a negative electrode that are arranged to face each other with the separator interposed therebetween. Then, the porous layer is formed on the negative electrode side surface of the separator, which is an interface between the separator and the negative electrode. Since the separator has poor wettability with respect to the coating material for forming the porous layer and the surface unevenness is smaller than that of the electrode, the adhesion with the porous layer tends to be lower than that of the electrode. Therefore, when the porous layer is formed on the separator side, it is particularly useful to apply the configuration of the present invention.

  A battery obtained by any one of the above-described methods disclosed herein exhibits excellent battery performance because the porous layer has a strong adhesive force and suppresses peeling of the porous layer over a long period of time. For example, it is possible to provide a battery that satisfies at least one (preferably all) of low heat generation due to an internal short circuit, excellent high rate characteristics, and good productivity.

  Such a battery (especially a secondary battery such as a lithium secondary battery having excellent high rate characteristics) is suitable as a battery mounted on a vehicle such as an automobile. Therefore, according to the present invention, it is possible to provide a suitable secondary battery for a power source of a vehicle (for example, a lithium secondary battery for a vehicle excellent in high rate characteristics). Further, there is provided a vehicle including any of the batteries disclosed herein (which may be in the form of an assembled battery in which a plurality of batteries are connected). In particular, since the light weight and high output can be obtained, the battery is a lithium secondary battery (typically a lithium ion battery), and the lithium secondary battery is used as a power source (typically a hybrid vehicle or an electric vehicle). A vehicle (for example, an automobile) provided as a power source of the vehicle is preferable.

It is sectional drawing which shows typically the principal part of the electrode body which concerns on one Embodiment of this invention. It is process drawing explaining the manufacturing flow of the porous layer which concerns on one Embodiment of this invention. It is a figure which shows typically the battery which concerns on one Embodiment of this invention. It is a figure explaining the wound electrode body which concerns on one Embodiment of this invention. It is a side view of the vehicle carrying the battery which concerns on one Embodiment of this invention.

  Embodiments according to the present invention will be described below with reference to the drawings. In the following drawings, members / parts having the same action are described with the same reference numerals. Note that the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship. In addition, matters other than those particularly mentioned in the present specification and matters necessary for the implementation of the present invention (for example, for the manufacturing method of active materials, the configuration and manufacturing method of separators and electrolytes, the construction of batteries and other batteries) Such general techniques, etc.) can be grasped as design matters of those skilled in the art based on the prior art in this field.

  Although not intended to be particularly limited, the battery according to this embodiment will be described below mainly using a lithium secondary battery (typically, a lithium ion battery) as an example.

  As shown in FIG. 1, the lithium secondary battery according to an embodiment of the present invention includes an electrode body 80 having a structure in which a positive electrode 10 and a negative electrode 20 are stacked with a separator 30 interposed therebetween. Similarly to a typical lithium secondary battery, the electrode body 80 is composed of predetermined battery constituent materials (active materials for positive and negative electrodes, current collectors for positive and negative electrodes, separators, and the like). In this embodiment, a positive electrode active material layer 14 containing a positive electrode active material is formed on a positive electrode current collector (here, foil-like aluminum) 12 in the positive electrode 10. In the negative electrode 20, a negative electrode active material layer 24 containing a negative electrode active material is formed on a negative electrode current collector 22 (here, foil-like copper).

  In addition, a porous layer 32 including an inorganic filler and a binder is formed on the surface of at least one of the positive electrode 10, the negative electrode 20, and the separator 30. In this embodiment, the porous layer 32 is provided at the interface between the separator 30 and the negative electrode 20 and is formed so as to cover the surface of the separator 30 on the negative electrode 20 side. The porous layer 32 includes an inorganic filler (typically in particulate form) and a binder, and the binder is bound between the inorganic filler particles and between the inorganic filler particles and the separator. A large number of pores are formed between the adjacent inorganic filler particles in a portion not bound by the binder. Sufficient battery output can be obtained by holding the electrolytic solution in the pores (that is, by impregnating the porous layer 32 with the electrolytic solution).

  Next, a method for forming a porous layer according to this embodiment will be described. As the porous layer forming coating material for forming the porous layer, a paste (including a slurry or an ink, the same applies hereinafter) in which an inorganic filler, a binder and a solvent are mixed and dispersed is used. A porous layer can be formed by applying an appropriate amount of this paste to at least one surface of the electrode and the separator and further drying.

  Solvents used in the porous layer-forming paint include organic solvents such as N-methylpyrrolidone (NMP), pyrrolidone, methyl ethyl ketone, methyl isobutyl ketone, ixahexanone, toluene, dimethylformamide, dimethylacetamide, or two of these. The above combination is mentioned. Alternatively, water or a mixed solvent mainly composed of water may be used. As a solvent other than water constituting such a mixed solvent, one or more organic solvents (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water can be appropriately selected and used. Although the content rate of the solvent in the coating material for porous layer formation is not specifically limited, About 30-60 mass% of the whole coating material is preferable.

As said inorganic filler, what has heat resistance and is electrochemically stable within the use range of a battery is preferable. Moreover, the said inorganic filler has an insulating property and the thing with high durability with respect to electrolyte solution is preferable. An example of such a material is a metal compound (typically powdered). Preferred examples include α-alumina (Al ₂ O ₃ ), boehmite (Al ₂ O ₃ .H ₂ O), magnesium hydroxide (Mg (OH) ₂ ), magnesium carbonate (MgCO ₃ ), and the like. One or more of these materials can be used. The average particle size of the metal compound powder is not particularly limited. For example, the volume-based average particle size (D ₅₀ ) measured using a general commercially available particle size meter (laser diffraction type particle size distribution measuring device or the like) is: Preferably, it is about 0.5 μm to 2.0 μm, more preferably 0.5 μm to 1.0 μm.

The binder is for binding an inorganic filler, and the material itself constituting the binder may be the same material as that used for a conventionally known porous layer.
For example, when the solvent for the coating material for forming the porous layer is an organic solvent, a polymer that is dispersed or dissolved in the organic solvent can be used. Examples of the polymer that is dispersed or dissolved in the organic solvent include acrylic resins. As acrylic resin, monomers such as acrylic acid, methacrylic acid, acrylamide, methacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, methacrylate, methyl methacrylate, ethylhexyl acrylate, butyl acrylate, etc. were polymerized in one kind. A homopolymer is preferably used. The acrylic resin may be a copolymer obtained by polymerizing two or more of the above monomers. Further, a mixture of two or more of the above homopolymers and copolymers may be used. In addition to the acrylic resin described above, polyvinylidene fluoride, polytetrafluoroethylene (PTFE), polyacrylonitrile, polymethyl methacrylate, and the like can also be used.
Moreover, when the solvent of the coating material for forming a porous layer is an aqueous solvent, a polymer that is dispersed or dissolved in water can be preferably used as the binder. Examples of the polymer dispersed or dissolved in water include styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), polyethylene (PE), polyacrylic acid (PAA), and the like. .

  The said coating material for porous layer formation can contain the 1 type, or 2 or more types of material which can be used as needed other than an inorganic filler and a binder. An example of such a material is a polymer that functions as a thickening agent for a coating material for forming a porous layer. In particular, when an aqueous solvent is used, it is preferable to contain a polymer that functions as the thickener. As the polymer functioning as the thickener, carboxymethyl cellulose (CMC) or polyethylene oxide (PEO) is preferably used.

  The porous layer forming paint is a paste-like (including slurry or ink) mixture prepared by mechanically dispersing and mixing the above components.

  Here, in the conventional coating material for forming a porous layer, the above-described components are simultaneously charged into a dispersing machine from the beginning and dispersed with a strong dispersion force to produce a paste-like mixture (porous layer forming coating material). However, if each component is dispersed simultaneously with a strong dispersion force from the beginning, the binder is destroyed by collision with a hard inorganic filler with a small particle size, and the binding force is reduced, thereby using the porous layer forming coating material. In some cases, the adhesive strength of the formed porous layer was lowered. If the adhesive strength of the porous layer is lowered, the porous layer is peeled off during repeated charging and discharging, and the internal short circuit of the battery, which is the original purpose, cannot be prevented.

  Therefore, in this configuration, before adding the binder, first, an inorganic filler is dispersed in a solvent to form an inorganic filler paint, and then the binder is added to the inorganic filler paint with a weaker force than the previous dispersion step. Disperse the binder. That is, in this configuration, as shown in FIG. 2, a first dispersion step (step S12) for forming an inorganic filler paint by mechanically dispersing an inorganic filler in a solvent, and a binder in the inorganic filler paint. Including a second dispersion step (step S14) in which a porous layer-forming coating material is formed by mechanical dispersion, and the dispersion force for mechanically dispersing the binder in the second dispersion step is inorganic in the first dispersion step. It sets so that it may become smaller than the dispersion force which disperse | distributes a filler mechanically.

  In this way, the dispersion of the inorganic filler and the binder are separately performed, and the relationship between the dispersion forces of the two steps (first dispersion step> second dispersion step) is appropriately adjusted, thereby colliding with the inorganic filler. Thus, the porous layer-forming coating material can be produced with extremely good dispersibility of the inorganic filler and the binder (that is, the inorganic filler and the binder are uniformly dispersed) without destroying the binder. If such a coating material for forming a porous layer is used, a porous layer having good adhesion to an electrode or a separator can be formed through a subsequent coating / drying step (step S20).

  The dispersion of the inorganic filler in the first dispersion step and the dispersion of the binder in the second dispersion step may be performed using the same disperser or different dispersers, but from the viewpoint of productivity. It is preferable to use the same disperser. When the same disperser is used, it is necessary to set the dispersion condition so that the dispersion force of the disperser satisfies the first dispersion step> the second dispersion step. For example, when the first dispersion step and the second step are performed using the same rotary disperser, the rotational speed of the rotary disperser in the second dispersion step is set to the rotational speed of the rotary disperser in the first dispersion step. It is better to set smaller than this. Thereby, the relationship of the dispersion force as described above (first dispersion step> second dispersion step) can be controlled more easily.

More specifically, when a high-speed stirrer such as Claremix (M Technique Co., Ltd.) is used, the dispersion condition is set so that the rotation speed of the high-speed stirrer is first dispersion step> second dispersion step. Good. Preferably, the rotational speed of the second dispersion step is 3/4 or less (typically 1/20 or less and 3/4 or less) of the first dispersion step, more preferably 1/2 or less, The dispersion condition is particularly preferably set to 1/10 or less.
In addition, when using a thin-film swirl type high-speed mixer such as Filmix (manufactured by Primix Co., Ltd.), the dispersion conditions may be set so that the peripheral speed of the mixer is first dispersion step> second dispersion step. Preferably, the peripheral speed of the second dispersion step is 8/9 or less (typically 1/2 or more and 8/9 or less) of the peripheral speed of the first dispersion step, more preferably 7/9 or less, The dispersion condition is particularly preferably set to 2/3 or less.

  The first dispersion step and the second step can be performed using the same ultrasonic disperser, not limited to the rotary disperser as described above. In this case, the dispersion condition may be set so that the amplitude of the ultrasonic disperser satisfies the first dispersion step> the second dispersion step. Thereby, the relationship of the dispersion force (first dispersion step> second dispersion step) can be controlled more easily. Preferably, the amplitude of the second dispersion step is 3/4 or less (typically 1/4 or more and 3/4 or less) of the amplitude of the first dispersion step, more preferably 3/5 or less, particularly preferably. The dispersion condition is set so as to be 1/2 or less. It should be noted that which condition is changed in controlling the dispersion force of various dispersers may be appropriately selected according to the device configuration of the disperser used.

  From the viewpoint of improving the adhesion of the porous layer, it is also effective to change the dispersion treatment time (including the number of dispersion treatments; the same applies hereinafter) in addition to the dispersion force. In the preferred technique disclosed herein, the dispersion processing time of the second dispersion process is set to be shorter than the dispersion processing time of the first dispersion process. According to this configuration, the destruction of the binder due to the collision with the inorganic filler is effectively suppressed, and a porous layer having better adhesion to the electrode or the separator can be obtained. Preferably, the dispersion time of the second dispersion step is 2/3 or less (typically 1/5 or more and 2/3 or less) of the dispersion time of the first dispersion step, more preferably 1/2 or less, The dispersion condition is particularly preferably set to 1/3 or less.

  Furthermore, the first dispersion step and the second dispersion step can be performed using different dispersers. In this case, by selecting a disperser having a much smaller dispersion force in the second dispersion step, the above-described dispersion force relationship (first dispersion step> second dispersion step) can be easily controlled, and the same Since the destruction of the binder is more effectively suppressed as compared with the case of using a disperser, a porous layer having better adhesion with the electrode or the separator can be obtained. Preferably, the first dispersion step is performed using a disperser having a relatively large dispersion force such as a high-speed stirrer (Claremix, etc.), a thin-film swirl type high-speed mixer (Filmmix, etc.), or an ultrasonic disperser, and The second dispersion step may be performed using a disperser having a relatively small dispersion force, such as a pulverizer (ball mill or the like) or a kneader (homodisper or the like).

  A porous layer can be formed by applying the coating material for forming a porous layer thus obtained to at least one surface of the electrode and the separator (here, the surface of the separator) and drying it. The operation of applying the porous layer forming coating to the separator surface can be performed in the same manner as in the case of producing a conventional general porous layer. For example, using a suitable coating device (gravure coater, slit coater, die coater, comma coater, dip coat, etc.), the separator is coated with a predetermined amount of the porous layer forming paint to a uniform thickness. Can be manufactured. Thereafter, the coating material is dried by a suitable drying means (typically a temperature lower than the melting point of the separator, for example, 110 ° C. or lower, for example, 30 to 80 ° C.), thereby removing the solvent in the coating material for forming the porous layer. . By removing the solvent from the porous layer forming paint, a porous layer containing an inorganic filler and a binder can be formed. In this way, a porous layer can be formed on the separator surface. In addition, after drying, the thickness and porosity of a porous layer can be suitably adjusted by performing an appropriate press process (for example, roll press process) as needed. The thickness of the porous layer is preferably about 1 μm to 10 μm, for example. Further, the porosity of the porous layer is preferably about 40% to 70%, for example.

Although not particularly limited, the proportion of the inorganic filler in the entire porous layer is about 80% by mass or more, for example, preferably about 90% by mass or more (typically 90 to 98% by mass).
Moreover, the ratio of the binder to the whole porous layer can be about 20 mass% or less, for example, it is preferable that it is 10 mass% or less (typically 2-10 mass%). If the binder content is too small, the adhesion between the separator and the porous layer may be reduced, and if the binder content is too high, the high-rate discharge characteristics may tend to be reduced.
Furthermore, in the porous layer having a composition containing a thickener, the proportion of the thickener in the porous layer can be about 5% by mass or less, for example, 2% by mass or less (typically 0.5 to 2%). % By mass).

  The separator with a porous layer thus obtained has a strong adhesion of the porous layer as described above, and the peeling of the porous layer is suppressed over a long period of time. It can be preferably used as a component of the electrode body incorporated in the housing. For example, a separator with a porous layer manufactured by any of the methods disclosed herein, and a positive electrode and a negative electrode separated by the separator (may be a positive and negative electrode with a porous layer manufactured by applying the present invention). And an electrolyte disposed between the positive and negative electrodes, and can be preferably used as a component of a lithium secondary battery. Structure (for example, metal casing or laminate film structure) and size of an outer container constituting such a battery, or structure of an electrode body (for example, a wound structure or a laminated structure) having a positive / negative electrode current collector as a main component There is no particular restriction on the etc.

  Hereinafter, an embodiment of a lithium secondary battery constructed using the separator 30 with a porous layer manufactured by applying the above-described method will be described with reference to schematic diagrams shown in FIGS. 3 and 4.

  As shown in FIG. 3, the lithium secondary battery 100 according to this embodiment includes a case 50 made of metal (a resin or a laminate film is also suitable). The case (outer container) 50 includes a flat rectangular parallelepiped case main body 52 whose upper end is opened, and a lid 54 that closes the opening. On the upper surface of the case 50 (that is, the lid 54), a positive electrode terminal 72 that is electrically connected to the positive electrode 10 of the wound electrode body 80 and a negative electrode terminal 74 that is electrically connected to the negative electrode 20 of the electrode body are provided. Yes. In the case 50, for example, a long sheet-like positive electrode (positive electrode sheet) 10 and a long sheet-like negative electrode (negative electrode sheet) 20 are laminated together with a total of two long sheet-like separators (separator sheets) 30. A flat wound electrode body 80 produced by winding and then crushing the resulting wound body from the side direction and kidnapping is housed.

  As shown in FIG. 4, the wound electrode body 80 is formed by winding a sheet-like electrode body 82. The sheet-like electrode body 82 has a long (band-like) sheet structure in a stage before assembling the wound electrode body 80. The sheet-like electrode body 82 is formed by laminating the positive electrode sheet 10 and the negative electrode sheet 20 together with the two separator sheets 30 in the same manner as a typical wound electrode body.

The positive electrode sheet 10 is formed by adhering a positive electrode active material layer 14 to both surfaces of a long sheet-like foil-shaped positive electrode current collector 12. However, the positive electrode active material layer 14 is not attached to one side edge along the edge in the width direction of the sheet-like electrode body, and the positive electrode current collector 12 is exposed with a certain width. For the positive electrode current collector 12, an aluminum foil (this embodiment) or other metal foil suitable for the positive electrode is preferably used. The positive electrode active material layer 14 is composed of a positive electrode active material and other positive electrode active material layer forming components (for example, a conductive additive and a binder) used as necessary. As the positive electrode active material, for example, a material mainly composed of a lithium transition metal composite oxide containing lithium and one or more transition metal elements as constituent metal elements is preferably used. Preferable examples include LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ (this embodiment).

  Similarly to the positive electrode sheet 10, the negative electrode sheet 20 is formed by attaching a negative electrode active material layer 24 to both surfaces of a long sheet-like foil-shaped negative electrode current collector 22. However, the negative electrode active material layer 24 is not attached to one side edge along the edge in the width direction of the sheet-like electrode body, and the negative electrode current collector 22 is exposed with a certain width. For the negative electrode current collector 22, a metal foil suitable for copper foil (this embodiment) and other negative electrodes is preferably used. The negative electrode active material layer 24 is composed of a negative electrode active material and other negative electrode active material layer forming components (such as a binder) used as necessary. As the negative electrode active material, one type or two or more types of materials conventionally used in lithium secondary batteries can be used without any particular limitation. Preferable examples include carbon-based materials such as graphite carbon and amorphous carbon (graphite in the present embodiment), lithium-containing transition metal oxides, transition metal nitrides, and the like.

  Examples of the separator sheet 30 used between the positive and negative electrode sheets 10 and 20 include those made of a porous polyolefin-based resin. Alternatively, a separator having a three-layer structure of polypropylene (PP) / polyethylene (PE) / polypropylene (PP) may be used. As described above, the separator sheet 30 of this configuration has the porous layer 32 at the interface with the negative electrode sheet 20. That is, the porous layer 32 is formed so as to cover the surface of the separator 30 on the negative electrode sheet side, and is disposed so as to face the negative electrode active material layer 24 of the negative electrode sheet 20. In a battery having such a configuration, when conductive foreign matter such as metal is mixed in the battery, it is assumed that the foreign matter penetrates the separator and bridges between the positive and negative electrodes to induce an internal short circuit. Such an internal short circuit can be preferably suppressed by forming the porous layer 32 on the surface of the separator 30 as in this configuration.

  When constructing the wound electrode body, the porous layer 32 formed on the surface of the separator 30 and the negative electrode active material layer 24 of the negative electrode sheet 20 are arranged to face each other, and the positive electrode active material of the positive electrode sheet 10 is arranged. The positive electrode sheet 10 and the negative electrode sheet 20 are slightly shifted and overlapped in the width direction so that the material layer non-formed portion and the negative electrode active material layer non-formed portion of the negative electrode sheet 20 protrude from both sides of the separator sheet 30 in the width direction. . As a result, in the lateral direction with respect to the winding direction of the wound electrode body 80, the electrode active material layer non-formation portions of the positive electrode sheet 10 and the negative electrode sheet 20 are respectively wound core portions (that is, the positive electrode active material layer formation portion of the positive electrode sheet 10). And a portion where the negative electrode active material layer forming portion of the negative electrode sheet 20 and the two separator sheets 30 are wound tightly). A positive electrode lead terminal 76 and a negative electrode lead terminal 78 are attached to the positive electrode side protruding portion (that is, the non-forming portion of the positive electrode mixture layer) 10A and the negative electrode side protruding portion (that is, the non-forming portion of the negative electrode mixture layer) 20A, respectively. Are electrically connected to the positive terminal 72 and the negative terminal 74 described above.

Then, the wound electrode body 80 is accommodated in the main body 52 from the upper end opening of the case main body 52 and an electrolytic solution containing an appropriate electrolyte is disposed (injected) in the case main body 52. The electrolyte is lithium salt such as LiPF _6, for example. For example, an appropriate amount (for example, concentration 1M) of a lithium salt such as LiPF ₆ is dissolved in a nonaqueous electrolytic solution such as a mixed solvent of diethyl carbonate and ethylene carbonate (for example, a mass ratio of 1: 1) and used as the electrolytic solution. be able to.

  Thereafter, the opening is sealed by welding or the like with the lid 54, and the assembly of the lithium secondary battery 100 according to the present embodiment is completed. The sealing process of the case 50 and the process of placing (injecting) the electrolyte may be the same as those used in the production of a conventional lithium secondary battery, and do not characterize the present invention. In this way, the construction of the lithium secondary battery 100 according to this embodiment is completed.

  The lithium secondary battery 100 constructed in this way has excellent battery performance because the adhesion between the separator and the porous layer is good as described above, and the peeling of the porous layer is preferably suppressed over a long period of time. It is shown. For example, by constructing a battery (for example, a lithium secondary battery) using the separator with the porous layer, at least one (preferably all) of high safety, excellent high-rate discharge characteristics, and good productivity. A battery that satisfies the above can be provided.

  EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the following examples.

<Test Example 1: Production of porous layer-forming coating material (CLEAMIX)>
In this example, the first dispersion step and the second dispersion step were performed using the same high-speed stirrer (CLEAMIX: manufactured by M Technique Co., Ltd.) to produce a porous layer forming coating material.

  First, in Example 1, 95 parts by weight of alumina powder (AKP3000: manufactured by Sumitomo Chemical) as an inorganic filler and an appropriate amount of N-methylpyrrolidone (NMP: manufactured by Kanto Chemical) as a solvent were added to Claremix, By stirring and mixing for 15 minutes at a rotational speed of 20000 rpm, an inorganic filler coating material in which the inorganic filler was dispersed was formed (first dispersion step). Next, 5 parts by weight of a binder powder composed of a polyacrylic acid derivative as a binder is added to an inorganic filler paint (10 wt% solution), and the mixture is stirred and mixed at a rotational speed of 2000 rpm for 5 minutes, whereby the binder and the inorganic filler are dispersed. A layer-forming coating material was obtained (second dispersion step).

  In Example 2, a coating material for forming a porous layer was produced in the same manner as in Example 1, except that the number of revolutions in the second dispersion step was changed to 15000 rpm. In Comparative Example 1, the coating material for forming a porous layer was prepared in the same manner as in Example 1, except that the number of rotations in the second dispersion step was changed to 20000 rpm, the same as in the first dispersion step. In Comparative Example 2, a porous layer-forming coating material was prepared by dispersing the inorganic filler and the binder all at once from the beginning as in the prior art. Regarding the batch dispersion condition, the rotation speed was 20000 rpm and the treatment time was 20 minutes.

<Test Example 2: Peel strength test (Claire mix)>
A porous layer was formed on the surface of the separator using a total of four types of coating materials for forming a porous layer prepared in Test Example 1, and the peel strength was evaluated. The porous layer was formed as follows.
First, various kinds of porous layer forming coating materials are applied in a strip shape by a gravure coating machine on one side of a separator sheet (polypropylene / polyethylene / polypropylene three-layer structure separator) having a thickness of 20 μm and dried, and a porous layer is formed on one side of the separator sheet. A separator sheet 30 with a porous layer provided with 32 was produced. The coating amount of the coating material for forming a porous layer was adjusted so as to be about 0.8 mg / cm ² (based on solid content). Further, after drying, the thickness of the porous layer was set to about 5 μm.

  And the peeling strength of the obtained separator sheet with a porous layer was measured. This measurement was performed according to JIS-C6481-1995. Specifically, the surface on the porous layer side is fixed on the table with double-sided tape, and the separator sheet is pulled in a direction perpendicular to the surface of the porous layer (peeling angle is 90 ± 5 °), and 20 mm / min. About 65 mm was peeled off continuously at a speed. And the average value of the load between 20 mm-40 mm was measured as peeling strength [N / m]. The result is shown in the corresponding part of Table 1.

  As is clear from Table 1, in Comparative Example 2 in which the inorganic filler and the binder were dispersed from the beginning as in the prior art, only a peel strength as low as 2.1 N / m was obtained. Further, in Comparative Example 1 in which the inorganic filler and the binder were separately dispersed and the rotational speed was set to the first dispersion step = second dispersion step, only peel strength comparable to that in Comparative Example 2 was obtained. In contrast, Examples 1 and 2 in which the inorganic filler and the binder are separately dispersed and the rotation speed is the first dispersion step> the second dispersion step are significantly improved in peel strength as compared with Comparative Examples 1 and 2. did. In particular, in Example 1 in which the rotation speed of the second dispersion process was 1/10 of the rotation speed of the first dispersion process, an extremely high peel strength of 5.8 N / m could be achieved.

<Test Example 3: Production of porous layer-forming coating material (ultrasonic dispersing machine)>
In this example, the first dispersion step and the second dispersion step were performed using the same ultrasonic disperser to produce a porous layer forming coating material.

  That is, in Example 3, the coating material for forming a porous layer was produced in the same manner as in Example 1, except that the dispersing machine was changed to an ultrasonic dispersing machine (manufactured by Ginsen Co., Ltd.). Regarding the ultrasonic dispersion conditions, the first dispersion step was performed with an amplitude of 40 μm, a frequency of 20 kHz, a flow rate of 0.2 L / min, and a processing frequency of 5 laps. In the second dispersion step, the amplitude was 20 μm, the frequency was 20 kHz, the flow rate was 0.2 L / min, and the number of treatments was one round. In Example 4, a porous layer-forming coating material was prepared in the same manner as in Example 3, except that the amplitude of the second dispersion step was changed to 30 μm.

  In Comparative Example 3, a porous layer-forming coating material was prepared in the same manner as in Example 3, except that the amplitude of the second dispersion step was changed to 40 μm, which was the same as that in the first dispersion step. In Comparative Example 4, a porous layer-forming coating material was prepared by dispersing the inorganic filler and the binder all at once from the beginning as in the prior art. The collective dispersion conditions were an amplitude of 40 μm, a frequency of 20 kHz, a flow rate of 0.2 L / min, and a processing frequency of 6 laps.

<Test Example 4: Peel strength test (ultrasonic dispersing machine)>
A porous layer was formed on the surface of the separator using a total of four kinds of porous layer forming paints prepared in Test Example 3, and the peel strength was evaluated. The formation of the porous layer and the peel strength test were performed in the same manner as in Test Example 2 described above. The result is shown in the corresponding part of Table 2.

  As is clear from Table 2, in Comparative Example 4 in which the inorganic filler and the binder were dispersed from the beginning as in the prior art, only a peel strength as low as 2.3 N / m was obtained. Further, in Comparative Example 3 in which the inorganic filler and the binder were separately dispersed and the ultrasonic amplitude was the first dispersion step = second dispersion step, only a peel strength comparable to that in Comparative Example 4 was obtained. On the other hand, Examples 3 and 4 in which the inorganic filler and the binder are separately dispersed and the ultrasonic amplitude is the first dispersion step> the second dispersion step are significantly larger in peel strength than the comparative examples 3 and 4. Improved. In particular, in Example 3 in which the ultrasonic amplitude in the second dispersion step was ½ that of the first dispersion step, an extremely high peel strength of 6.2 N / m could be achieved.

<Test Example 5: Production of paint for forming porous layer (fill mix)>
In this example, the first dispersion step and the second dispersion step were performed using the same thin film swirl type high-speed mixer (Filmix: manufactured by Primix Co., Ltd.) to produce a porous layer forming coating material.

  That is, in Example 5, a coating material for forming a porous layer was produced in the same manner as in Example 1, except that the disperser was changed to Filmix (manufactured by PRIMIX Co., Ltd.). Regarding the dispersion conditions, the first dispersion step was performed at a peripheral speed of 45 m / s and a processing time of 3 minutes. In the second dispersion step, the peripheral speed was 30 m / s and the processing time was 1 minute. In Example 6, a porous layer-forming coating material was prepared in the same manner as Example 5, except that the peripheral speed of the second dispersion step was changed to 40 m / s.

  In Comparative Example 5, a coating material for forming a porous layer was produced in the same manner as in Example 5, except that the peripheral speed in the second dispersion step was changed to 45 m / s, which was the same as that in the first dispersion step. In Comparative Example 6, a porous layer-forming coating material was prepared by dispersing the inorganic filler and the binder all at once from the beginning as in the prior art. The batch dispersion conditions were a peripheral speed of 45 m / s and a processing time of 4 minutes.

<Test Example 6: Peel strength test (fill mix)>
A porous layer was formed on the surface of the separator by using a total of four types of porous layer forming paints prepared in Test Example 5, and the peel strength was evaluated. The formation of the porous layer and the peel strength test were performed in the same manner as in Test Example 2 described above. The result is shown in the corresponding part of Table 3.

  As is apparent from Table 3, Comparative Example 6 in which the inorganic filler and the binder were dispersed all at once from the beginning as in the prior art had a peel strength as low as 1.8 N / m. Further, in Comparative Example 5 in which the inorganic filler and the binder were separately dispersed and the peripheral speed was the first dispersion step = second dispersion step, only a peel strength comparable to that in Comparative Example 6 was obtained. In contrast, in Examples 5 and 6, in which the inorganic filler and the binder are separately dispersed and the peripheral speed is the first dispersion step> the second dispersion step, the peel strength is significantly improved as compared with Comparative Examples 5 and 6. did. Particularly in Example 5 in which the peripheral speed of the second dispersion step was 2/3 of the peripheral speed of the first dispersion step, an extremely high peel strength of 5.2 N / m could be achieved.

<Test Example 7: Production of porous layer-forming coating material (different dispersers)>
In this example, the first dispersion step and the second dispersion step were performed using different dispersers to produce a porous layer forming coating material.

  That is, in Example 7, the coating material for forming the porous layer was produced in the same manner as in Example 1, except that the disperser in the second dispersion step was changed to Homo Disper (manufactured by Primex Corporation). In Example 8, the coating material for forming a porous layer was prepared in the same manner as in Example 3, except that the disperser in the second dispersion step was changed to Homo Disper (manufactured by Primix Co., Ltd.). Moreover, in Example 9, it carried out similarly to Example 5, However, the disperser of the 2nd dispersion | distribution process was changed into the homodisper (made by Primix Co., Ltd.), and the coating material for porous layer formation was produced. Regarding the dispersion conditions of the second dispersion process in Examples 7 to 9, the rotation speed was 1500 m / s and the treatment time was 5 minutes.

<Test Example 8: Peel strength test (different dispersers)>
A porous layer was formed on the surface of the separator using a total of three types of porous layer forming paints prepared in Test Example 7, and the peel strength was evaluated. The formation of the porous layer and the peel strength test were performed in the same manner as in Test Example 2 described above. The result is shown in the corresponding part of Table 4.

  As is apparent from Table 4, Examples 7 to 9 using different dispersers in the first dispersion step and the second dispersion step all achieved extremely high peel strength exceeding 5.5 N / m. . Moreover, it was found from the comparison between Example 7 and Example 1 that the peel strength was further improved as compared with the case where the same disperser (CLEAMIX) was used. Moreover, it was found from the comparison between Example 8 and Example 3 that the peel strength was further improved as compared with the case where the same disperser (ultrasonic disperser) was used. Moreover, it was found from the comparison between Example 9 and Example 5 that the peel strength was further improved as compared with the case where the same disperser (fill mix) was used.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.

  For example, in the above-described embodiment, the case where the porous layer 32 is formed on the negative electrode side surface of the separator 30 at the interface between the separator 30 and the negative electrode 20 is illustrated, but is not limited thereto. For example, the porous layer can be formed on the separator-side surface of the negative electrode 20 (typically, the surface of the negative electrode active material layer) at the interface between the separator 30 and the negative electrode 20. Further, the porous layer can be formed on the surface of the separator 30 on the positive electrode side, which is the interface between the separator 30 and the positive electrode 10. Furthermore, a porous layer can be formed on the separator-side surface of the positive electrode 10 (typically, the surface of the positive electrode active material layer) at the interface between the separator 30 and the positive electrode 10. Regardless of the formation site of the porous layer, according to this configuration, the adhesion (adhesion) between the porous layer and the formation site can be improved.

  Since the battery (for example, lithium secondary battery) according to the present invention has excellent battery performance as described above, it can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Therefore, the present invention, as shown in FIG. 5, is a vehicle 1 (typically an automobile, particularly a hybrid automobile, an electric automobile, a fuel cell automobile, etc.) having such a battery 100 (which may be in the form of an assembled battery) as a power source. A motor vehicle equipped with a simple electric motor).

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Positive electrode 12 Positive electrode collector 14 Positive electrode active material layer 20 Negative electrode 22 Negative electrode current collector 24 Negative electrode active material layer 30 Separator 32 Porous layer 50 Case 52 Case body 54 Lid 72 Positive electrode terminal 74 Negative electrode terminal 76 Positive electrode lead terminal 78 Negative electrode lead terminal 80 Winding electrode body 82 Sheet electrode body 100 Lithium secondary battery

Claims (9)

A method for producing a battery in which a porous layer containing an inorganic filler and a binder is formed on at least one surface of an electrode and a separator,
A first dispersion step of forming an inorganic filler coating by mechanically dispersing the inorganic filler in a solvent;
A second dispersion step of forming a porous layer forming coating by mechanically dispersing a binder in the inorganic filler coating;
Forming a porous layer by applying the porous layer-forming coating material to at least one surface of an electrode and a separator and drying the coating;
Here, the dispersion force for mechanically dispersing the binder in the second dispersion step is set to be smaller than the dispersion force for mechanically dispersing the inorganic filler in the first dispersion step. A battery manufacturing method. Performing the dispersion of the inorganic filler in the first dispersion step and the dispersion of the binder in the second dispersion step using the same rotary disperser; and
The manufacturing method according to claim 1, wherein the rotational speed of the rotary disperser in the second dispersion step is set to be smaller than the rotational speed of the rotary disperser in the first dispersion step. The dispersion of the inorganic filler in the first dispersion step and the dispersion of the binder in the second dispersion step are performed using the same ultrasonic disperser, and
The manufacturing method according to claim 1, wherein the ultrasonic amplitude of the ultrasonic disperser in the second dispersion step is set to be smaller than the ultrasonic amplitude of the ultrasonic disperser in the first dispersion step.   The manufacturing method according to claim 1, wherein the dispersion processing time of the second dispersion step is set to be shorter than the dispersion processing time of the first dispersion step.   The manufacturing method according to claim 1, wherein the dispersion of the inorganic filler in the first dispersion step and the dispersion of the binder in the second dispersion step are performed using different dispersers.   The manufacturing method according to any one of claims 1 to 5, wherein metal compound particles having an average particle size of 0.5 µm to 2.0 µm are used as the inorganic filler. The electrodes are a positive electrode and a negative electrode arranged opposite to each other with the separator interposed therebetween,
The manufacturing method according to claim 1, wherein the porous layer is formed on a surface on the negative electrode side of the separator, which is an interface between the separator and the negative electrode. A lithium secondary battery in which a porous layer containing an inorganic filler and a binder is formed on at least one surface of an electrode and a separator,
The lithium secondary battery manufactured by the manufacturing method as described in any one of Claim 1 to 7.   A vehicle provided with the battery manufactured by the manufacturing method as described in any one of Claim 1 to 7, or the lithium secondary battery of Claim 8.

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