JP2006210003A - Electrode for battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for an electrode of a battery used under high output condition capable of improving durability of the battery by relaxing unevenness of reaction generated along thickness direction of an activator layer. <P>SOLUTION: The electrode for the battery including a collector, and activator layers formed on the surface of the collector and including an activator increases the specific surface area of the activator from the surface side of the activator layer toward the collector side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery electrode. In particular, the present invention relates to an improvement for improving the durability of a battery electrode.

  In recent years, in order to cope with air pollution and global warming, reduction of the amount of carbon dioxide has been strongly desired. In the automobile industry, there is a great expectation for reducing carbon dioxide emissions by introducing electric vehicles (EV) and hybrid electric vehicles (HEV), and the development of secondary batteries for motor drive that holds the key to their practical application is thriving. Has been done.

As a secondary battery for driving a motor, a lithium ion secondary battery having the highest theoretical energy among all the batteries is attracting attention, and is currently being developed rapidly. Generally, a lithium ion secondary battery includes a positive electrode in which a positive electrode active material or the like is applied to both surfaces of a positive electrode current collector using a binder, and a negative electrode in which a negative electrode active material or the like is applied to both surfaces of a negative electrode current collector using a binder. However, it has the structure connected through the electrolyte layer and accommodated in a battery case (for example, refer patent document 1).
JP 2003-7345 A

  Conventionally, when manufacturing an electrode of a lithium ion secondary battery, an active material slurry containing an active material or a binder is prepared, and this is applied to the surface of a current collector, thereby providing an active material having a uniform composition. It is common to form layers.

  When charging / discharging a battery equipped with an electrode manufactured by such a method, when charging / discharging at a not so high output, even in an active material layer having a uniform composition, the charge / discharge reaction proceeds uniformly. sell.

  However, in response to the demand for higher performance of the battery, when the battery is charged and discharged at a higher output, the charge / discharge reaction does not proceed uniformly in the active material layer having a uniform composition, and the thickness of the active material layer Reaction unevenness may occur along the vertical direction. That is, the progress of the charge / discharge reaction is concentrated on the active material located on the side closer to the electrolyte layer (the side farther from the current collector). As a result, the active material closer to the electrolyte layer repeats more expansion and contraction and deteriorates preferentially, and as a result, the durability of the battery decreases. Moreover, the active material farther from the electrolyte layer (the side closer to the current collector) cannot effectively contribute to the charge / discharge reaction, resulting in waste. Note that the problems described above are significant in bipolar batteries that are being developed with higher output in mind.

  Accordingly, an object of the present invention is to provide a means capable of alleviating reaction unevenness generated along the thickness direction of an active material layer and improving battery durability in a battery electrode used under high output conditions. And

  The present invention is a battery electrode having a current collector and an active material layer including an active material formed on a surface of the current collector, wherein the specific surface area of the active material is the active material layer It increases from the surface side of this to the said collector side, It is an electrode for batteries characterized by the above-mentioned.

  The present invention also provides a step of preparing a first active material slurry containing a first active material, and a second active material slurry containing a second active material having a specific surface area larger than that of the first active material. Applying the first active material slurry and the second active material slurry to the surface of the current collector so that the second active material slurry is applied to the current collector side; And a step of forming a coating film.

  In the active material layer of the battery electrode of the present invention, the specific surface area of the active material increases from the surface side of the active material layer toward the current collector side of the active material layer. Thereby, even in charge / discharge under high output conditions, reaction unevenness along the thickness direction of the active material layer can be alleviated. Therefore, the electrode of the present invention can contribute to improvement of battery durability.

  Embodiments of the present invention will be described below.

(First embodiment)
(Constitution)
The present invention is a battery electrode having a current collector and an active material layer including an active material formed on a surface of the current collector, wherein the specific surface area of the active material is the active material layer It increases from the surface side of this to the said collector side, It is an electrode for batteries characterized by the above-mentioned.

  As described above, when a conventional electrode having an active material layer having a uniform composition is used to charge and discharge a battery under high output conditions, the reaction unevenness is such that the reaction concentrates on the active material closer to the electrolyte layer. May occur. This is presumed to be due to the following reason.

  That is, the resistance accompanying mass transfer in the active material layer is mainly divided into resistance due to electron movement (electron transfer resistance) and resistance accompanying ion movement (ion diffusion resistance). Further, the electron transfer resistance is smaller on the current collector side and larger on the electrolyte layer side. In contrast, the ion diffusion resistance is smaller on the electrolyte layer side and larger on the current collector side. As described above, the electron transfer resistance and the ion diffusion resistance are in an inverse relationship along the thickness direction of the active material layer, and seem to cancel each other at first glance. However, the ion diffusion resistance is considerably larger than the electron transfer resistance. For this reason, the effect of ion diffusion resistance becomes obvious under high output conditions, and the charge / discharge reaction proceeds preferentially in the active material on the side of the electrolyte layer with lower ion diffusion resistance, resulting in uneven reaction. It ends up.

  As a result of intensive studies to solve the above problems, the present inventors have found that reaction unevenness can be alleviated by controlling the specific surface area of the active material contained in the active material layer. It came to complete.

  Hereinafter, the structure of the battery electrode of the present invention will be described with reference to the drawings. In the present invention, the drawings are exaggerated for convenience of explanation, and the technical scope of the present invention is not limited to the forms shown in the drawings. Also, embodiments other than the drawings may be employed.

  In a preferred embodiment of the present invention, as shown in FIG. 1, the active material layer is disposed on the current collector side with respect to the first active material layer containing the first active material and the first active material layer. In addition, the second active material layer including a second active material having a specific surface area larger than that of the first active material is stacked. In the present specification, the terms “first” and “second” included in the active material contained in the active material layer of the battery electrode and the active material slurry prepared in the manufacturing method described later are These are merely used for the purpose of showing that the specific surface areas of the active materials or the specific surface areas of the active materials contained in the respective active material slurries are different. There is no special meaning in the order itself. In addition, the terms “first” and “second” do not limit the types of active materials contained in the active material layer and the types of active material slurries used to manufacture the electrodes to only two types, respectively. Of course, three or more of them may be used.

  FIG. 1 is a schematic view showing an embodiment of the battery electrode of the present invention. The battery electrode 1 in the form shown in FIG. 1 is a bipolar electrode in which a positive electrode active material layer 13 is formed on one surface of a current collector 11 and a negative electrode active material layer 15 is formed on the other surface.

  In the present embodiment, each of the positive electrode active material layer 13 and the negative electrode active material layer 15 is composed of three layers (13A, 13B and 13C, and 15A, 15B and 15C). And the average particle diameter of each active material contained in three layers which comprise each active material layer (13,15) is the surface side (namely, collector 11 from the active material layer (13,15)). From the farthest side to the current collector 11 side (positive electrode active material A (13a) → positive electrode active material B (13b) → positive electrode active material C (13c), and negative electrode active material A (15a) → negative electrode active material B (15b) → negative electrode active material C (15c)) decreases. Thereby, the specific surface area of the active material contained in three layers which comprise an active material layer (13,15) is increasing toward the collector 11 side from the surface side of the active material layer.

  By the way, the internal resistance in the active material layer includes contact resistance on the surface of the active material in addition to the above-described resistance due to movement of electrons and ions. This contact resistance is inversely proportional to the surface area of the active material that can participate in the reaction.

  Here, as shown in FIG. 1, the active material (13a, 15a) having a small specific surface area (large average particle diameter) is disposed on the side far from the current collector (13A, 15A), and the side closer to the current collector. When the active material (13c, 15c) having a large specific surface area (small average particle diameter) is disposed on (13C, 15C), the contact resistance becomes relatively large on the side farther from the current collector (13A, 15A). The contact resistance is relatively small on the side closer to the body (13C, 15C). That is, a contact resistance gradient on the surface of the active material occurs in the opposite direction to the ion diffusion resistance gradient that becomes apparent under high output conditions, and the ion diffusion resistance and the contact resistance cancel each other. The internal resistance can be made uniform along the thickness direction. As a result, reaction unevenness under high output conditions is alleviated. Even if the electrode of the present invention contributes to alleviation of reaction unevenness by other mechanisms, the technical scope of the present invention is not affected at all.

  The bipolar electrode as shown in FIG. 1 can be employed in, for example, a bipolar lithium ion secondary battery (hereinafter also simply referred to as “bipolar battery”). Of course, it may be adopted for other batteries.

  Hereinafter, the configuration of the battery electrode of the present invention will be described by taking as an example a case where it is employed in a lithium ion secondary battery. The battery electrode of the present invention is characterized in that the specific surface area of the active material contained in the active material layer increases from the surface side of the active material layer toward the current collector side. There is no particular limitation on the selection of the current collector, active material, binder, supporting salt (lithium salt), ion-conducting polymer, and other compounds added as necessary. Depending on the intended use, it may be selected by appropriately referring to conventionally known knowledge. The battery electrode of the present invention can be applied to both the positive electrode and the negative electrode. For example, when applied to the positive electrode, the current collector and the active material are used as the current collector and the positive electrode active material for the positive electrode. A compound known to act may be employed.

[Current collector]
The current collector 11 is made of a conductive material such as an aluminum foil, a nickel foil, a copper foil, or a stainless steel (SUS) foil. The general thickness of the current collector is 1 to 30 μm. However, a current collector having a thickness outside this range may be used.

  The size of the current collector is determined according to the intended use of the battery. If a large electrode used for a large battery is manufactured, a current collector having a large area is used. If a small electrode is produced, a current collector with a small area is used.

[Active material layer]
An active material layer (13, 15) is formed on the current collector 11. The active material layers (13, 15) are layers containing an active material that plays a central role in the charge / discharge reaction. When the electrode of the present invention is used as a positive electrode, the active material layer contains a positive electrode active material. On the other hand, when the electrode of the present invention is used as a negative electrode, the active material layer contains a negative electrode active material.

As the positive electrode active material, a lithium-transition metal composite oxide is preferable, and examples thereof include a Li—Mn composite oxide such as LiMn ₂ O ₄ and a Li—Ni composite oxide such as LiNiO ₂ . In some cases, two or more positive electrode active materials may be used in combination.

  As the negative electrode active material, the above lithium transition metal-composite oxide or carbon is preferable. Examples of carbon include graphite-based carbon materials such as natural graphite, artificial graphite, and expanded graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon, and hard carbon.

  The active material layers (13, 15) may contain other materials if necessary. For example, a binder, a conductive additive, a supporting salt (lithium salt), an ion conductive polymer, and the like can be included. When an ion conductive polymer is included, a polymerization initiator for polymerizing the polymer may be included.

  Examples of the binder include polyvinylidene fluoride (PVdF) and a synthetic rubber binder.

  A conductive support agent means the additive mix | blended in order to improve the electroconductivity of an active material layer. Examples of the conductive aid include carbon powder such as graphite and various carbon fibers such as vapor grown carbon fiber (VGCF).

Examples of the supporting salt (lithium salt) include Li (C ₂ F ₅ SO ₂ ) ₂ N) (LiBETI), LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO _{3 and the} like.

  Examples of the ion conductive polymer include polyethylene oxide (PEO) -based and polypropylene oxide (PPO) -based polymers. Here, the polymer may be the same as or different from the ion conductive polymer used in the electrolyte layer of the battery in which the electrode of the present invention is employed, but is preferably the same.

  The polymerization initiator is blended to act on the crosslinkable group of the ion conductive polymer and advance the crosslinking reaction. Depending on the external factor for acting as an initiator, it is classified into a photopolymerization initiator, a thermal polymerization initiator and the like. Examples of the polymerization initiator include azobisisobutyronitrile (AIBN), which is a thermal polymerization initiator, and benzyl dimethyl ketal (BDK), which is a photopolymerization initiator.

  The compounding ratio of the components contained in the active material layers (13, 15) is not particularly limited. The blending ratio can be adjusted by appropriately referring to known knowledge about lithium ion secondary batteries.

  Hereinafter, the characteristic structure of the electrode of the present invention will be described in detail. That is, in the electrode of the present invention, the specific surface area of the active material contained in the active material layer increases from the surface side of the active material layer toward the current collector side. According to such a form, the reaction unevenness can be reduced by the mechanism described above.

In the electrode of the present invention, the specific surface area of the active material contained in the active material layer only needs to increase from the surface side of the active material layer toward the current collector side, and other specific forms are not particularly limited. The “specific surface area” is a surface area per unit mass, and the unit is, for example, [m ² / g]. In addition, whether or not “the specific surface area of the active material increases from the surface side of the active material toward the current collector side” is, for example, that the active material layer is made of a current collector having a thickness approximately equal to the particle diameter of the active material. This can be determined by slicing into a plurality of sections parallel to the body surface, measuring the specific surface area of the active material contained in a predetermined area of each section, and comparing each section. Of course, it may be determined by other methods.

  As an example of the form of the active material in the active material layer, first, as described above with reference to FIG. 1, there is a form in which the specific surface area of the active material is controlled by adjusting the average particle diameter of the active material. Can be mentioned. The average particle diameter of the active material is not particularly limited, but is usually about 0.5 to 30 μm. However, it goes without saying that an active material outside this range may be used.

  As shown in FIG. 2, it is possible to provide a gradient of the specific surface area of the active material by changing the surface state of the active material. FIG. 2 is a schematic view showing another embodiment of the battery electrode of the present invention.

  Also in the electrode of the form shown in FIG. 2, the positive electrode active material layer 13 and the negative electrode active material layer 15 are each composed of three layers (13A ′, 13B ′, and 13C ′, and 15A ′, 15B ′, and 15C ′). It is comprised by. And in this form, the average particle diameter of each active material contained in three layers which comprise each active material layer (13, 15) is substantially the same between each layer. However, the surface state of the active material contained in each layer is different. That is, the active material is on the surface so that the specific surface area of the active material included in the three layers constituting the active material layer (13, 15) increases from the surface side of the active material layer toward the current collector 11 side. Has been processed. An example of such surface treatment is heat treatment. In general, the specific surface area of the active material can be reduced by heat-treating the active material under higher temperature conditions. Therefore, at the time of manufacturing the electrode having the form shown in FIG. 2, each active material contained in the three layers constituting the active material layer (13, 15) is collected from the surface side of the active material layer (13, 15). Toward the body 11 (positive electrode active material A ′ (13a ′) → positive electrode active material B ′ (13b ′) → positive electrode active material C ′ (13c ′) and negative electrode active material A ′ (15a ′) → negative electrode active Substance B ′ (15b ′) → negative electrode active material C ′ (15c ′)) may be heat-treated at a lower temperature. If possible, active materials having different specific surface areas obtained by means other than heat treatment may be used.

  As described above, also in the electrode having the form shown in FIG. 2, the specific surface area of the active material increases from the surface side of the active material layer toward the current collector side. For this reason, also in this embodiment, the internal resistance of the active material layer is made uniform along the thickness direction by the same mechanism as that described for the embodiment shown in FIG. 1, and reaction unevenness under high output conditions can be alleviated. .

  As shown in FIG. 3, a gradient of the specific surface area of the active material may be provided by employing a plurality of active materials having different specific surface areas and changing the blending ratio of the plurality of active materials. FIG. 3 is a schematic view showing still another embodiment of the battery electrode of the present invention.

  Also in the electrode of the form shown in FIG. 3, the positive electrode active material layer 13 and the negative electrode active material layer 15 each have three layers (13A ″, 13B ″, and 13C ″, and 15A ″, 15B ″, and 15C ″). It is comprised by. However, in this embodiment, two types of positive and negative active materials (positive electrode active material A (13a) and positive electrode active material C (13c), and negative electrode active material A) used in the form shown in FIG. (15a) and negative electrode active material C (15c)) are employed. And these compounding ratios are changed between three layers which comprise an active material layer (13,15). Specifically, the active materials contained in the positive electrode active material layer A ″ (13A ″) and the negative electrode active material layer A ″ (15A ″) are all active materials having a larger average particle diameter (positive electrode active material A or negative electrode). Active material A) (A: C = 100: 0 (mass%)). On the other hand, the active materials contained in the positive electrode active material layer C ″ (13C ″) and the negative electrode active material layer C ″ (15C ″) are all active materials having a smaller average particle diameter (positive electrode active material C or negative electrode active material C). (A: C = 0: 100 (mass%)). The positive electrode active material layer B ″ (13B ″) and the negative electrode active material layer B ″ (15B ″) each contain the same amount of the above two active materials (A: C = 50: 50 (mass%) )).

  The average particle size of the active material contained in the positive electrode active material layer B ″ (13B ″) is equal to the average particle size of the active material contained in the positive electrode active material layer A ″ (13A ″) and the positive electrode active material layer C ″ (13C ″). It is a value between the average particle diameter of the active material contained in. On the other hand, the average particle diameter of the active material contained in the negative electrode active material layer B ″ (15B ″) is equal to the average particle diameter of the active material contained in the negative electrode active material layer A ″ (15B ″) and the negative electrode active material layer C ″ ( 15C ″) is a value between the average particle diameters of the active materials. Therefore, also in the electrode shown in FIG. 3, the average particle diameter of the active material decreases from the surface side of the active material layer toward the current collector side as in the case shown in FIG. Specific surface area increases. For this reason, also in this embodiment, the internal resistance of the active material layer is made uniform along the thickness direction by the same mechanism as that described for the embodiment shown in FIG. 1, and reaction unevenness under high output conditions can be alleviated. .

  In addition, when changing the compounding ratio of a plurality of active materials having different average particle diameters, the specific value of the compounding ratio is not particularly limited, and a desired value of the average particle diameter (or specific surface area) of the active material is taken into consideration. Then, it may be adjusted as appropriate.

  In the form shown in FIG. 3, the gradient of the specific surface area of the active material is provided by changing the blending ratio of a plurality of active materials having different average particle diameters. However, in some cases, as shown in FIG. You may provide the gradient of the specific surface area of an active material by changing the compounding ratio of the several active material from which the surface state employ | adopted in the form shown shows.

  As described above, the case where the positive electrode active material layer 13 and the negative electrode active material layer 15 are each composed of three layers has been described as an example. However, in the case where the active material layers (13, 15) are composed of a plurality of layers, The number is not particularly limited, and can be appropriately determined in consideration of a desired gradient of the specific surface area and ease of production. The number of layers constituting each active material layer (13, 15) is preferably 2 to 10 layers, more preferably 2 to 5 layers. If the number of layers constituting each active material layer exceeds 10, the production of the electrode may be complicated. However, in some cases, the active material layer may be formed of more than 10 layers. The number of layers constituting each of the positive electrode active material layer 13 and the negative electrode active material layer 15 may be the same or different.

  In the above-described embodiment in which the active material layer is composed of a plurality of layers, the specific surface area of the active material changes discretely from the surface side of the active material layer toward the current collector side. However, if possible, the electrode of the present invention may be formed by continuously changing the specific surface area of the active material as shown in FIG. 5 without forming the active material layer from a plurality of layers.

(Production method)
The present application also provides a method of manufacturing a battery electrode. That is, the second aspect of the present invention is a step of preparing a first active material slurry containing the first active material (first active material slurry preparation step), and a specific surface area larger than that of the first active material. A step of preparing a second active material slurry containing a second active material, and the first active material slurry and the second active material slurry so that the second active material slurry is applied to the current collector side. And a step of forming a coating film by applying an active material slurry to the surface of a current collector. According to such a method, the battery electrode having the configuration shown in FIGS. 1 to 4 can be manufactured.

  Hereinafter, in the electrode 1 having the configuration shown in FIG. 1, the manufacturing method of the negative electrode active material layer 15 will be described in detail in the order of steps, taking as an example the case of manufacturing the positive electrode active material layer 13. Is omitted. The technical scope of the present invention should be determined based on the description of the scope of claims, and is not limited to the following forms.

[First positive electrode active material slurry preparation step]
In this step, a desired positive electrode active material and other components (for example, a binder, a conductive additive, a supporting salt (lithium salt), an ion conductive polymer, a polymerization initiator, etc.) are added in a solvent. The first positive electrode active material slurry is prepared by mixing. Since the specific form of each component blended in the first positive electrode active material slurry is as described in the column of the configuration of the electrode of the present invention, detailed description is omitted here. However, the average particle diameter of the positive electrode active material (first positive electrode active material) used in this step is the positive electrode active material (second positive electrode active material) used in the [second positive electrode active material slurry preparation step] described later. ) Larger than the average particle size. In addition, the specific value of the average particle diameter of the positive electrode active material is not particularly limited.

  A plurality of positive electrode active materials having different average particle diameters may be prepared by purchasing commercially available products, or may be prepared by preparing themselves. As a method for preparing such a positive electrode active material by itself, for example, when pulverizing a positive electrode active material having a larger average particle size to obtain an active material having a smaller average particle size, pulverization conditions (grinding time, An example is a method of appropriately changing the mill method.

  When it is desired to manufacture an electrode having the form shown in FIG. 2, for example, a positive electrode active material having a certain average particle diameter is prepared, and the active material is subjected to heat treatment under a plurality of different conditions to thereby obtain a surface state. It is possible to prepare a plurality of positive electrode active materials having different specific surface areas (that is, specific surface areas and the like). Examples of heat treatment conditions that can be changed at this time include a heat treatment temperature, a heat treatment time, and a gas atmosphere during the heat treatment. The specific form of the heat treatment conditions is not particularly limited, and conventionally known knowledge can be appropriately referred to in the field of active material preparation. For example, the heat treatment is performed at a temperature of about 400 to 1500 ° C. for about 5 minutes to 24 hours. Can be done.

  The kind of solvent and the mixing means are not particularly limited, and conventionally known knowledge about electrode production can be appropriately referred to. As an example of the solvent, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylformamide and the like can be used. When adopting polyvinylidene fluoride (PVdF) as a binder, NMP is preferably used as a solvent.

[Second cathode active material slurry preparation step]
Also in this step, a positive electrode active material slurry is prepared in the same manner as in the above [first positive electrode active material slurry preparation step]. Since the specific form is almost the same as the above [first positive electrode active material slurry preparation step], detailed description is omitted here. However, the average particle diameter of the positive electrode active material (second positive electrode active material) used in this step is the positive electrode active material (first positive electrode active material) used in the above [first positive electrode active material slurry preparation step]. It is smaller than the average particle diameter. In other words, the specific surface area of the positive electrode active material (second positive electrode active material) used in this step is equal to the positive electrode active material (first positive electrode active material) used in the above [first positive electrode active material slurry preparation step]. ) Greater than the specific surface area.

  When it is desired to manufacture an electrode having a positive electrode active material layer composed of three layers as shown in FIG. 1, in addition to the first and second positive electrode active material slurries, a third A positive electrode active material slurry may be prepared and used in a coating process described later. Under the present circumstances, the positive electrode active material used for preparation of the 3rd positive electrode active material slurry is an average particle rather than the positive electrode active material (2nd positive electrode active material) used in said [2nd positive electrode active material slurry preparation process]. Reduce the diameter (increase the specific surface area). The same applies to the fourth and subsequent positive electrode active material slurries. The positive electrode active material used for the preparation of the nth (n is an integer of 2 or more) positive electrode active material slurry is the (n-1) th positive electrode active material. What is necessary is just to make an average particle diameter smaller (large specific surface area) than the positive electrode active material used for preparation of a material slurry.

[Coating process]
Subsequently, a current collector 11 for forming the positive electrode active material layer 13 is prepared. The specific form of the current collector prepared in this step is the same as that described in the column of the configuration of the electrode of the present invention, and a detailed description thereof will be omitted here.

  Subsequently, the plurality of positive electrode active material slurries prepared above are prepared as described above so that the positive electrode active material slurry containing the positive electrode active material having a smaller average particle diameter (large specific surface area) is applied to the current collector side. It is applied to the surface of the current collector 11. That is, first, the third positive electrode active material slurry is applied to the surface of the current collector to form a coating film. Thereafter, a drying process is performed. Thereby, the solvent in a coating film is removed and the active material layer C (13C shown in FIG. 1) located in the most current collector side is formed.

  Thereafter, the second positive electrode active material slurry and the first positive electrode active material slurry are similarly applied in this order to form a coating film, and then subjected to a drying treatment. Thereby, the positive electrode active material layer B (13B) adjacent to the positive electrode active material layer C (13C) formed as described above and the positive electrode active material layer A (13A) adjacent to the positive electrode active material layer B (13B) are formed. Is done. Thus, finally, the positive electrode active material layer of the battery electrode in the form shown in FIG. 1 is completed. When the fourth and subsequent positive electrode active material slurries were prepared, each positive electrode was so applied that the nth positive electrode active material slurry was applied to the current collector side of the (n-1) positive electrode active material slurry. The active material slurry is applied and dried to form a positive electrode active material layer consisting of n layers on the surface of the current collector.

  The application means for applying each positive electrode active material slurry is not particularly limited. For example, a commonly used means such as a coater can be adopted.

  In a more preferred embodiment, the battery electrode manufacturing method of the present invention employs an ink jet method when forming a coating film. By adopting the inkjet method, an extremely thin coating film (for example, a coating film for forming each of 13A, 13B, and 13C shown in FIG. 1) can be easily formed. Moreover, the uniformity of the thickness of such a coating film can also be improved. Hereinafter, a method for forming a positive electrode active material layer using an inkjet method will be described in detail.

  The “inkjet method” means a printing method in which liquid ink is ejected from a nozzle and ink is adhered to an object. The ink jet method is classified into a piezo method, a thermal ink jet method, and a bubble jet (registered trademark) method according to a method of ejecting ink.

  The piezo method is a method in which ink is ejected from nozzles by deformation of a piezo element that is arranged at the bottom of an ink chamber that stores ink and deforms when an electric current flows. The thermal ink jet method is a method in which ink is heated by an exothermic heater, and the ink is ejected by the energy of steam explosion when the ink is vaporized. The bubble jet (registered trademark) method is a method in which ink is ejected by the energy of steam explosion when the ink is vaporized, similarly to the thermal ink jet method. The thermal ink jet method and the bubble jet (registered trademark) method are different in the portion to be heated, but the basic principle is the same. The ink jet method is not particularly limited. Moreover, you may give a required improvement according to the ink to be used. Since the ink jet system is a technique that is very widely known at present, a detailed description of the ink jet system is omitted here.

  In order to form the positive electrode active material layer 13 using the ink jet method, first, a positive electrode active material ink for forming the positive electrode active material layer (specifically, three layers constituting the positive electrode active material layer are formed). A positive electrode active material ink). The composition of the positive electrode active material ink is the above except that it is processed to make the ink viscosity suitable for the ink jet system (for example, it contains a relatively large amount of solvent). The composition of the positive electrode active material slurry described is almost the same. Therefore, the concept of “positive electrode active material ink” is included in the concept of “positive electrode active material slurry”, and a detailed description of the positive electrode active material ink is also omitted here.

  The compounding ratio of the components contained in the positive electrode active material ink is not particularly limited. However, the viscosity of the positive electrode active material ink should be low enough to apply the ink jet method. Examples of the method for keeping the viscosity low include a method for increasing the amount of the solvent and a method for increasing the temperature of the positive electrode active material ink. However, if the amount of the solvent is excessively increased, the amount of the positive electrode active material per unit volume in the positive electrode active material layer 13 is decreased. Therefore, the amount of the solvent is preferably minimized. It should be noted that the positive electrode active material ink may include an ion conductive polymer, but the polymer tends to increase the viscosity of the ink. The ion conductive polymer and other compounds may be improved so as to reduce the viscosity. The viscosity of the positive electrode active material ink to be used is not particularly limited, but is preferably about 0.1 to 10 cP.

  In order to form the positive electrode active material layer 13 of the electrode shown in FIG. 1, a plurality of positive electrode active materials having different average particle diameters (for example, a first positive electrode active material, a second positive electrode active material, and a third positive electrode active material) A plurality of positive electrode active material inks including each of the positive electrode active materials) may be prepared and applied to the surface of the current collector by the method described later in the same order as described above.

  In order to apply the positive electrode active material ink prepared above, a current collector 11 for forming the positive electrode active material layer 13 is prepared. The specific form of the current collector 11 to be prepared is as already described.

  Thereafter, the current collector 11 is supplied to an ink jet apparatus capable of printing the positive electrode active material ink. Then, the positive electrode active material ink is ejected to the current collector by an ink jet method and is attached to the surface of the current collector 11. The amount of ink ejected from the nozzles of the ink jet apparatus is very small, and is approximately equal in volume. Therefore, the coating film formed by the adhesion of the positive electrode active material ink is very thin and uniform. Moreover, if the inkjet system is used, the thickness of the coating film can be precisely controlled. Furthermore, if an ink jet system is used, a predetermined pattern is designed on a computer, and a coating film having a desired shape is formed by simply printing the pattern. When the thickness of the coating film is insufficient in one printing, the printing may be repeated twice or more on the same surface. That is, the same active material ink may be printed in the same place. Thereby, a coating film having a desired thickness is formed.

  The drying means for drying the coating film is not particularly limited, and conventionally known knowledge about electrode production can be appropriately referred to. For example, heat treatment is exemplified. Drying conditions (drying time, drying temperature, etc.) can be appropriately set according to the coating amount of the positive electrode active material slurry and the volatilization rate of the solvent in the slurry.

  When the coating film does not contain a polymerization initiator, the positive electrode active material layer 13 is completed with the completion of the drying step. When a coating film contains a polymerization initiator, the ion conductive polymer in a coating film is bridge | crosslinked by a crosslinkable group by performing a superposition | polymerization process, and the positive electrode active material layer 13 is completed.

  The polymerization treatment in the polymerization step is not particularly limited, and conventionally known knowledge may be referred to as appropriate. For example, when the coating film contains a thermal polymerization initiator (AIBN or the like), the coating film is subjected to heat treatment. Moreover, when a coating film contains a photoinitiator (BDK etc.), light, such as an ultraviolet light, is irradiated. In addition, the heat processing for thermal polymerization may be performed simultaneously with said drying process, and may be performed before or after the said drying process. The polymerization treatment may be performed every time each layer constituting the positive electrode active material layer is formed, or may be performed after formation of all the layers constituting the positive electrode active material layer.

  By performing the above operation on a plurality of positive electrode active material inks each including a plurality of positive electrode active materials having different average particle diameters, the positive electrode active material layer 13 of the electrode shown in FIG. 1 can be formed.

As described above, the case where the positive electrode active material layer 13 is formed on the surface of the current collector 11 has been described as an example.
The negative electrode active material layer 15 can also be manufactured by the same method as the positive electrode active material layer 13.

  A coating film is formed according to the desired arrangement | positioning form of the electrical power collector and active material layer in the electrode manufactured. For example, when the manufactured electrode is a bipolar electrode, a coating film containing a positive electrode active material is formed on one surface of the current collector, and a coating film containing a negative electrode active material is formed on the other surface. On the other hand, when an electrode that is not a bipolar type is manufactured, a coating film containing either the positive electrode active material or the negative electrode active material is formed on both surfaces of one current collector.

(Second Embodiment)
In 2nd Embodiment, a battery is comprised using the battery electrode of said 1st Embodiment.

  That is, a third aspect of the present invention is a battery having at least one single cell layer in which a positive electrode, an electrolyte layer, and a negative electrode are laminated in this order, and at least one of the positive electrode and the negative electrode is an electrode of the present invention. There is a battery. The electrode of the present invention can be applied to any of a positive electrode, a negative electrode, and a bipolar electrode. A battery including the electrode of the present invention as at least one electrode belongs to the technical scope of the present invention. However, preferably, all of the electrodes constituting the battery are the electrodes of the present invention. By adopting such a configuration, the durability of the battery can be effectively improved.

  The battery of the present invention may be a bipolar lithium ion secondary battery (hereinafter also referred to as “bipolar battery”). FIG. 6 is a cross-sectional view showing a third battery of the present invention, which is a bipolar battery. Hereinafter, although the bipolar battery shown in FIG. 6 will be described in detail as an example, the technical scope of the present invention is not limited to such a form.

  The bipolar battery 10 of this embodiment shown in FIG. 6 has a structure in which a substantially rectangular battery element 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminate sheet 29 that is an exterior.

  As shown in FIG. 6, the battery element 21 of the bipolar battery 10 of this embodiment includes a positive electrode active material layer 13 composed of three layers each including three types of positive electrode active materials having different average particle diameters, and the same average particle diameter. A negative electrode active material layer 15 composed of three layers each containing three different types of negative electrode active materials has a plurality of bipolar electrodes (bipolar electrodes of the form shown in FIG. 1) formed on each surface of the current collector 11. In FIG. 6, the active material layer is composed of three layers as described above, but each active material layer is illustrated as one layer. Each bipolar electrode is laminated via an electrolyte layer 17 to form a battery element 21. At this time, each bipolar electrode and electrolyte layer are arranged so that the positive electrode active material layer 13 of one bipolar electrode and the negative electrode active material layer 15 of another bipolar electrode adjacent to the one bipolar electrode face each other through the electrolyte layer 17. 17 are stacked.

  The adjacent positive electrode active material layer 13, electrolyte layer 17, and negative electrode active material layer 15 constitute one unit cell layer 19. Therefore, it can be said that the bipolar battery 10 has a configuration in which the single battery layers 19 are stacked. In addition, an insulating layer 31 for insulating adjacent current collectors 11 is provided on the outer periphery of the unit cell layer 19. The current collector (outermost layer current collector) (11a, 11b) located in the outermost layer of the battery element 21 has a positive electrode active material layer 13 (positive electrode side outermost layer current collector 11a) or a negative electrode only on one side. One of the active material layers 15 (negative electrode side outermost layer current collector 11b) is formed.

  Further, in the bipolar battery 10 shown in FIG. 6, the positive electrode side outermost layer current collector 11a is extended to form a positive electrode tab 25, which is led out from a laminate sheet 29 which is an exterior. On the other hand, the negative electrode side outermost layer current collector 11 b is extended to form a negative electrode tab 27, which is similarly derived from the laminate sheet 29.

  Hereinafter, members constituting the bipolar battery 10 of the present embodiment will be briefly described. However, since the components constituting the electrode are as described above, the description thereof is omitted here. Further, the technical scope of the present invention is not limited to the following forms, and conventionally known forms can be similarly adopted.

[Electrolyte layer]
A liquid electrolyte or a polymer electrolyte can be used as the electrolyte constituting the electrolyte layer 17.

  The liquid electrolyte has a form in which a lithium salt as a supporting salt is dissolved in an organic solvent as a plasticizer. Examples of the organic solvent that can be used as the plasticizer include carbonates such as ethylene carbonate (EC) and propylene carbonate (PC). Further, as the supporting salt (lithium salt), a compound that can be added to the active material layer of the electrode, such as LiBETI, can be similarly employed.

  On the other hand, the polymer electrolyte is classified into a gel electrolyte containing an electrolytic solution and an intrinsic polymer electrolyte containing no electrolytic solution.

  The gel electrolyte has a configuration in which the above liquid electrolyte is injected into a matrix polymer made of an ion conductive polymer. Examples of the ion conductive polymer used as the matrix polymer include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. In such polyalkylene oxide polymers, electrolyte salts such as lithium salts can be well dissolved.

  In the case where the electrolyte layer 17 is composed of a liquid electrolyte or a gel electrolyte, a separator may be used for the electrolyte layer 17. Specific examples of the separator include a microporous film made of polyolefin such as polyethylene or polypropylene.

  The intrinsic polymer electrolyte has a structure in which a supporting salt (lithium salt) is dissolved in the matrix polymer, and does not include an organic solvent that is a plasticizer. Therefore, when the electrolyte layer 17 is composed of an intrinsic polymer electrolyte, there is no fear of liquid leakage from the battery, and the reliability of the battery can be improved.

  The matrix polymer of the gel electrolyte or the intrinsic polymer electrolyte can exhibit excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, etc. are performed on a polymerizable polymer (for example, PEO or PPO) for forming a polymer electrolyte using an appropriate polymerization initiator. A polymerization treatment may be performed.

[Insulation layer]
In the bipolar battery 10, an insulating layer 31 is usually provided around each unit cell layer 19. The insulating layer 31 is provided for the purpose of preventing the adjacent current collectors 11 in the battery from contacting each other and short-circuiting due to a slight unevenness at the end of the battery cell layer 19 in the battery element 21. It is done. The installation of such an insulating layer 31 ensures long-term reliability and safety, and can provide a high-quality bipolar battery 10.

  The insulating layer 31 only needs to have insulating properties, sealing properties against falling off of the solid electrolyte, sealing properties against moisture permeation from the outside (sealing properties), heat resistance under battery operating temperature, etc. Urethane resin, epoxy resin, polyethylene resin, polypropylene resin, polyimide resin, rubber and the like can be used. Of these, urethane resins and epoxy resins are preferred from the viewpoints of corrosion resistance, chemical resistance, ease of production (film forming properties), economy, and the like.

[tab]
In the bipolar battery 10, the tab (positive electrode tab 25 and negative electrode tab 27) electrically connected to the outermost layer current collector (11a, 11b) is used for taking out the current outside the battery. Take out to the outside. Specifically, the positive electrode tab 25 electrically connected to the positive electrode outermost layer current collector 11 a and the negative electrode tab 27 electrically connected to the negative electrode outermost layer current collector 11 b are formed on the laminate sheet 29. Take out to the outside.

  The material of the tabs (the positive electrode tab 25 and the negative electrode tab 27) is not particularly limited, and a known material conventionally used as a tab for a bipolar battery can be used. Examples thereof include aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof. The positive electrode terminal 25 and the negative electrode terminal 27 may be made of the same material or different materials. As in the present embodiment, the outermost layer current collectors (11a, 11b) may be extended to form tabs (25, 27), or a separately prepared tab may be connected to the outermost layer current collector. Good.

[Exterior]
In the bipolar battery 10, the battery element 21 is preferably housed in an exterior such as a laminate sheet 29 in order to prevent external impact and environmental degradation during use. The exterior is not particularly limited, and a conventionally known exterior can be used. A polymer-metal composite laminate sheet or the like excellent in thermal conductivity can be preferably used in that heat can be efficiently transferred from a heat source of an automobile and the inside of the battery can be rapidly heated to the battery operating temperature.

(Third embodiment)
In the third embodiment, a plurality of the bipolar batteries of the second embodiment are connected in parallel and / or in series to constitute an assembled battery.

  FIG. 7 is a perspective view showing the assembled battery of the present embodiment.

  As shown in FIG. 7, the assembled battery 40 is configured by connecting a plurality of the bipolar batteries of the second embodiment. Specifically, each bipolar battery 10 is connected by connecting the positive electrode tab 25 and the negative electrode tab 27 of each bipolar battery 10 using a bus bar. On one side surface of the assembled battery 40, electrode terminals (42, 43) are provided as electrodes of the entire assembled battery 40.

  The connection method when connecting the plurality of bipolar batteries 10 constituting the assembled battery 40 is not particularly limited, and a conventionally known method can be appropriately employed. For example, a technique using welding such as ultrasonic welding or spot welding, or a technique of fixing using rivets, caulking, or the like can be employed. According to such a connection method, the long-term reliability of the assembled battery 40 can be improved.

  According to the assembled battery 40 of this embodiment, since each bipolar battery 10 which comprises the assembled battery 40 is excellent in durability, the assembled battery excellent in durability can be provided.

  The connection of the bipolar batteries 10 constituting the assembled battery 40 may be all connected in parallel, all may be connected in series, or a combination of series connection and parallel connection may be used. Also good.

(Fourth embodiment)
In the fourth embodiment, the bipolar battery 10 of the second embodiment or the assembled battery 40 of the third embodiment is mounted as a motor driving power source to constitute a vehicle. As a vehicle using the bipolar battery 10 or the assembled battery 40 as a motor power source, for example, a complete electric vehicle that does not use gasoline, a hybrid vehicle such as a series hybrid vehicle or a parallel hybrid vehicle, and a fuel cell vehicle, etc., wheels are driven by a motor. A driving car can be mentioned.

  For reference, FIG. 8 shows a schematic diagram of an automobile 50 on which the assembled battery 40 is mounted. The assembled battery 40 mounted on the automobile 50 is excellent in durability as described above. For this reason, the automobile 50 equipped with the assembled battery 40 is excellent in durability, and can provide a sufficient output even after being used for a long period of time.

  Although several preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications, omissions, and additions can be made by those skilled in the art. For example, in the second embodiment, the bipolar lithium ion secondary battery (bipolar battery) has been described as an example. However, the technical scope of the battery of the present invention is not limited to the bipolar battery. For example, a non-bipolar lithium ion secondary battery may be used. For reference, FIG. 9 is a cross-sectional view showing an outline of a lithium ion secondary battery 60 that is not bipolar.

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited to only the forms shown in the following examples.

Example 1
<Preparation of positive electrode>
Spinel-type lithium manganate (LiMn ₂ O ₄ ) (average particle size: 0.6 μm, specific surface area: 9.5 m ² / g) (80 g) as a positive electrode active material, acetylene black (10 g) as a conductive auxiliary agent, Then, polyvinylidene fluoride (PVdF) (10 g) as a binder was mixed, and then an appropriate amount of N-methyl-2-pyrrolidone (NMP) as a slurry viscosity adjusting solvent was added to prepare a positive electrode active material slurry C.

Subsequently, as the positive electrode active material, LiMn ₂ O ₄ (average particle size: 1.4 μm, specific surface area: 3.6 m ² / g) was used, except that it was the same as the preparation of the positive electrode active material slurry C described above. The positive electrode active material slurry B was prepared by the method.

Furthermore, the same method as the preparation of the positive electrode active material slurry C described above, except that LiMn ₂ O ₄ (average particle size: 3.2 μm, specific surface area: 1.7 m ² / g) was used as the positive electrode active material. Thus, a positive electrode active material slurry A was prepared.

  On the other hand, an aluminum foil (thickness: 20 μm) was prepared as a positive electrode current collector. The positive electrode active material slurry C prepared above was applied to one surface of the prepared current collector by the doctor blade method to form a coating film. Subsequently, this coating film was dried at 130 ° C. for 10 minutes to form a positive electrode active material layer C (thickness: 10 μm) on the surface of the current collector.

  The positive electrode active material slurry B prepared above was applied to the surface of the positive electrode active material layer C formed above by a doctor blade method to form a coating film. Next, this coating film was dried at 130 ° C. for 10 minutes to form the positive electrode active material layer B on the positive electrode active material layer C.

  The positive electrode active material slurry A prepared above was applied to the surface of the positive electrode active material layer B formed as described above by a doctor blade method to form a coating film. Next, this coating film was dried at 130 ° C. for 10 minutes to form the positive electrode active material layer A on the positive electrode active material layer B, thereby completing the positive electrode.

<Production of negative electrode>
Hard carbon (average particle size: 0.7 μm, specific surface area: 15.6 m ² / g) (90 g) as a negative electrode active material, and polyvinylidene fluoride (PVdF) (10 g) as a binder are mixed, and then the slurry viscosity An appropriate amount of N-methyl-2-pyrrolidone (NMP) as a adjusting solvent was added to prepare a negative electrode active material slurry C.

Subsequently, by the same method as the preparation of the negative electrode active material slurry C described above, except that hard carbon (average particle size: 1.4 μm, specific surface area: 8.3 m ² / g) was used as the negative electrode active material. A negative electrode active material slurry B was prepared.

Furthermore, except that hard carbon (average particle size: 4.0 μm, specific surface area: 2.9 m ² / g) was used as the negative electrode active material, the same procedure as in the preparation of the negative electrode active material slurry C was performed. A negative electrode active material slurry A was prepared.

  On the other hand, a copper foil (thickness: 20 μm) was prepared as a current collector for the negative electrode. The negative electrode active material slurry C prepared above was applied to one surface of the prepared current collector by the doctor blade method to form a coating film. Next, this coating film was dried at 130 ° C. for 10 minutes to form a negative electrode active material layer C (thickness: 10 μm) on the surface of the current collector.

  The negative electrode active material slurry B prepared above was applied to the surface of the negative electrode active material layer C formed above by a doctor blade method to form a coating film. Next, this coating film was dried at 130 ° C. for 10 minutes to form the negative electrode active material layer B on the negative electrode active material layer C.

  The negative electrode active material slurry A prepared above was applied to the surface of the negative electrode active material layer B formed above by the doctor blade method to form a coating film. Next, this coating film was dried at 130 ° C. for 10 minutes to form the positive electrode active material layer A on the negative electrode active material layer B, thereby completing the negative electrode.

<Production of test coin cell>
In order to use as a positive electrode and a negative electrode of a test coin cell, the positive electrode and the negative electrode prepared above were punched to 15 mmφ and 16 mmφ, respectively, using a punch.

Furthermore, a polypropylene microporous film (thickness: 15 μm) was prepared as a separator. Further, as the electrolytic solution, a LiPF ₆ is a lithium salt was prepared which is dissolved in a concentration of 1M in an equal volume mixture of ethylene carbonate and propylene carbonate.

  The negative electrode, separator, and positive electrode obtained above were laminated in this order, and the electrolyte was injected into the separator. Next, a current extraction terminal is connected to each of the negative electrode and the positive electrode, and the battery element is placed in an aluminum laminate film so that the current extraction terminal is exposed to the outside, and sealed in a vacuum to produce a test coin cell. did.

<Example 2>
In preparing the positive electrode active material slurries C, B, and A, LiMn ₂ O ₄ (average particle diameter: 1.5 μm, specific surface area: 6.4 m ² / g), LiMn ₂ O ₄ ( Average particle diameter: 1.4 μm, specific surface area: 3.6 m ² / g), and LiMn ₂ O ₄ (average particle diameter: 1.2 μm, specific surface area: 2.5 m ² / g), respectively, In preparing the material slurries C, B, and A, as the negative electrode active material, hard carbon (average particle size: 1.4 μm, specific surface area: 12.6 m ² / g), hard carbon (average particle size: 1. 4 μm, specific surface area: 8.3 m ² / g), and hard carbon (average particle size: 1.6 μm, specific surface area: 4.5 m ² / g), respectively, except that each was used. Test coin cell It was produced.

<Example 3>
In preparing the positive electrode active material slurries C, A, and B, LiMn ₂ O ₄ (average particle diameter: 1.4 μm, specific surface area: 6.4 m ² / g), LiMn ₂ O ₄ ( Average particle diameter: 1.2 μm, specific surface area: 2.5 m ² / g), and an equal mass mixture of the above-mentioned two kinds of LiMn ₂ O ₄ , respectively, and further preparing negative electrode active material slurries C, A, and B when, as a negative electrode active material, hard carbon (average particle diameter: 1.4 [mu] m, a specific surface area: 12.6m ² / g), hard carbon (average particle diameter: 1.6 [mu] m, a specific surface area: 4.5 m ² / A test coin cell was prepared in the same manner as in Example 1 except that g) and the above-mentioned two kinds of hard carbon equimolar mixtures were used.

<Comparative Example 1>
When preparing the positive electrode active material slurries C, B, and A, LiMn ₂ O ₄ (average particle size: 1.4 μm, specific surface area: 3.6 m ² / g) was used as the positive electrode active material, When preparing the negative electrode active material slurries C, B, and A, except that hard carbon (average particle size: 1.4 μm, specific surface area: 8.3 m ² / g) was used as the negative electrode active material. A test coin cell was produced in the same manner as in Example 1 above.

<Evaluation of battery characteristics of test coin cell>
For each of the above examples and comparative examples, five identical test coin cells were prepared, and a 10C constant current cycle test was performed on each test coin cell at a voltage of 2.5 to 4.2 V. The discharge capacity at the time of the first discharge, as well as the discharge capacity after 1 charge / discharge cycle, after 100 times, after 200 times, and after 500 times are measured, and the average value of the five test coin cells is as follows: The capacity maintenance rate was calculated. The results are shown in Table 1 below.

  From the comparison between each example and the comparative example, by increasing the specific surface area of the active material from the surface side of the active material layer toward the current collector side, the battery capacity after the charge / discharge cycle has been maintained at a high value. You can see that This is presumed to be due to the mitigation of the reaction unevenness that occurs along the thickness direction of the active material layer.

  Therefore, the electrode of the present invention can effectively contribute to the improvement of battery durability.

It is the schematic which shows one Embodiment (1st Embodiment) of the electrode for batteries of this invention. It is the schematic which shows other embodiment of the battery electrode of this invention. It is the schematic which shows other embodiment of the battery electrode of this invention. It is the schematic which shows other embodiment of the battery electrode of this invention. It is the schematic which shows other embodiment of the battery electrode of this invention. It is sectional drawing which shows preferable one Embodiment of the bipolar battery of 2nd Embodiment. It is a perspective view which shows the assembled battery of 3rd Embodiment. It is the schematic of the motor vehicle of 4th Embodiment carrying the assembled battery of 3rd Embodiment. It is sectional drawing which shows the outline | summary of the lithium ion secondary battery which is not a bipolar type.

Explanation of symbols

1 Bipolar electrode,
10 Bipolar battery,
11 Current collector,
13 positive electrode active material layer,
13A, 13B, 13C, 13A ′, 13B ′, 13C ′, 13A ″, 13B ″, 13C ″ layers constituting the positive electrode active material layer,
13a, 13b, 13c, 13a ′, 13b ′, 13c ′, 13a ″, 13b ″, 13c ″ positive electrode active material,
15 negative electrode active material layer,
15A, 15B, 15C, 15A ′, 15B ′, 15C ′, 15A ″, 15B ″, 15C ″ layers constituting the negative electrode active material layer,
15a, 15b, 15c, 15a ′, 15b ′, 15c ′, 15a ″, 15b ″, 15c ″ negative electrode active material,
17 electrolyte layer,
19 cell layer,
21 battery elements,
25 positive electrode tab,
27 negative electrode tab,
29 Laminate sheet,
31 insulating layer,
33 positive electrode current collector,
35 negative electrode current collector,
40 battery packs,
50 cars,
60 Lithium ion secondary battery that is not bipolar.

Claims (11)

A battery electrode having a current collector and an active material layer containing an active material formed on a surface of the current collector,
The battery electrode, wherein a specific surface area of the active material increases from a surface side of the active material layer toward the current collector side. The active material layer is
A first active material layer containing a first active material;
A second active material layer including a second active material having a specific surface area larger than that of the first active material, disposed closer to the current collector than the first active material layer;
The battery electrode according to claim 1, which has a configuration in which are stacked.   The battery electrode according to claim 2, wherein an average particle diameter of the second active material is smaller than an average particle diameter of the first active material. A battery having at least one single cell layer in which a positive electrode, an electrolyte layer, and a negative electrode are laminated in this order,
The battery whose at least one of the said positive electrode or the said negative electrode is a battery electrode of any one of Claims 1-3.   The battery according to claim 4, which is a nonaqueous electrolyte battery.   The battery according to claim 4 or 5, which is a bipolar lithium ion secondary battery.   The assembled battery using the battery of any one of Claims 4-6.   A vehicle on which the battery according to any one of claims 4 to 6 or the assembled battery according to claim 7 is mounted. Preparing a first active material slurry containing a first active material;
Preparing a second active material slurry containing a second active material having a specific surface area larger than that of the first active material;
A coating film is formed by applying the first active material slurry and the second active material slurry to the surface of the current collector so that the second active material slurry is applied to the current collector side. And a process of
The manufacturing method of the electrode for batteries which has these.   The manufacturing method according to claim 9, wherein an average particle diameter of the second active material is smaller than an average particle diameter of the first active material.   The manufacturing method of Claim 9 or 10 with which the formation of the said coating film is performed using an inkjet system.

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