JP2011134589A - Manufacturing method of electrode for secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of reducing the increased reactive resistance (interface resistance), while preventing corrosion of an electrode collector in forming an electrode active material layer using an aqueous paste, and to provide a manufacturing method of an electrode excellent in the electrical performance by using such a technique. <P>SOLUTION: The present invention provides a manufacturing method of an electrode for a secondary battery in which an electrode active material layer mainly consisting of an electrode active material is formed on an electrode collector. The method includes applying a nonaqueous solvent with a specific gravity greater than water on the top surface of the electrode collector to form a barrier layer consisting of the nonaqueous solvent, applying an aqueous paste consisting of at least a mixture of the electrode active material and an aqueous solvent on the top surface of the barrier layer, and evaporating the nonaqueous solvent that forms the barrier layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an electrode including an active material layer formed from a paste-like composition formed using an aqueous solvent.

Lithium secondary batteries (for example, lithium ion batteries), nickel metal hydride batteries, and other secondary batteries are becoming increasingly important as on-vehicle power supplies or personal computers and portable terminals. In particular, a lithium secondary battery that is lightweight and has a high energy density is expected to increase in the future as it is preferably used as a high-output power source mounted on a vehicle.
In one typical configuration of this type of lithium secondary battery, an electrode active material layer (specifically, a positive electrode active material layer and an electrode active material layer mainly composed of an electrode active material capable of reversibly occluding and releasing lithium ions). The negative electrode active material layer is provided with an electrode having a configuration in which the negative electrode active material layer is held on the surface of the electrode current collector.
For example, in the case of a positive electrode, a positive electrode active material such as a lithium transition metal composite oxide is mixed in advance with a highly conductive material powder (conductive material) and a binder in an appropriate solvent to form a positive electrode active material layer. A positive electrode active material layer is formed by preparing a paste-like composition (a paste-like composition includes a slurry-like composition; the same applies hereinafter) and applying the composition to a positive electrode current collector. The

  An aqueous solvent may be used as a solvent to be mixed when preparing the paste composition. A paste-like composition using an aqueous solvent (hereinafter referred to as “aqueous paste”) requires less organic solvent and accompanying industrial waste as compared with a paste-like composition using an organic solvent. Therefore, since there is no equipment and processing costs for that purpose, there is an advantage that the environmental load is generally reduced.

  By the way, an aqueous paste containing a positive electrode active material such as a lithium transition metal composite oxide tends to exhibit alkalinity when lithium ions constituting the oxide or the like are eluted into an aqueous solvent. When such an aqueous paste is applied to a positive electrode current collector made of metal, for example, a positive electrode current collector made of aluminum, corrosion due to alkali occurs, and a film of aluminum oxide is excessively formed on the surface of the positive electrode current collector. Internal resistance may increase. In order to cope with such a problem, Patent Document 1 is cited as a prior art. Patent Document 1 describes a technique that can prevent corrosion of a current collector by applying a coupling agent to the surface of the current collector.

JP 2008-153053 A

However, although the technique described in Patent Document 1 can prevent corrosion of the electrode current collector using an aqueous paste, the coupling agent layer that is no longer required after the electrode active material layer is formed is an electrode. By continuing to exist between the current collector and the electrode active material layer, the coupling agent layer itself can cause interface resistance.
Therefore, the present invention has been created to solve the above-described conventional problems, and its purpose is to form an electrode active material layer using an aqueous paste while suppressing an increase in reaction resistance (interface resistance). It is to provide a technique capable of preventing corrosion of the electrode current collector at the time, and to provide a method for manufacturing an electrode excellent in electrical performance by applying such technique. Another object is to provide a secondary battery including an electrode obtained by such a manufacturing method and a vehicle including the secondary battery.

  In order to achieve the above object, according to the present invention, an electrode for a secondary battery in which an electrode active material layer mainly composed of an electrode active material is formed on an electrode current collector (for example, a lithium secondary battery such as a lithium ion battery). Provided is a method for producing a representative non-aqueous electrolyte secondary battery electrode (typically, a positive electrode). The production method disclosed herein includes applying a non-aqueous solvent having a specific gravity greater than that of water to the surface of the electrode current collector to form a barrier layer made of the non-aqueous solvent, and at least the electrode active material and an aqueous system. It includes applying an aqueous paste mixed with a solvent to the surface of the barrier layer and evaporating the non-aqueous solvent forming the barrier layer.

In the present specification, the term “secondary battery” refers to a battery that can be repeatedly charged, and includes so-called storage batteries such as lithium secondary batteries (typically lithium ion batteries) and nickel metal hydride batteries.
In this specification, the “electrode active material” refers to reversibly occlusion and release (typically insertion and removal) of a chemical species (for example, lithium ion in a lithium ion battery) that serves as a charge carrier in a secondary battery. A possible substance.
In the present specification, the “non-aqueous solvent” may be composed of one kind of molecular species, or may be a mixture of two or more kinds. For example, what is comprised by mixing 2 or more types of organic solvents from which a boiling point mutually differs (for example, molecular weight differs) is included by the nonaqueous solvent here.

In the method for producing an electrode for a secondary battery provided by the present invention, an aqueous paste prepared from at least an electrode active material and an aqueous solvent (that is, a paste-like composition comprising an aqueous solvent) is used as an electrode current collector. Prior to coating, a non-aqueous solvent having a specific gravity greater than that of water is applied to the electrode current collector to form a barrier layer made of the non-aqueous solvent, and then the barrier layer is evaporated.
Thus, by applying a non-aqueous solvent to the electrode current collector in advance, an aqueous paste that tends to be alkaline, such as an aqueous paste using a lithium transition metal composite oxide as an electrode active material, is used. Even when it is applied to the electrode, the reaction between the electrode current collector and the aqueous paste (alkali corrosion reaction or the like) is prevented. In addition, when the electrode active material layer formed by drying the aqueous paste is formed on the electrode current collector by evaporating the non-aqueous solvent after the aqueous paste is applied, the electrode current collector, the electrode active material layer, There is no intervening material that can increase the reaction resistance. Therefore, also it realized high adhesion while suppressing the increase in the reaction resistance and the electrode current collector and the electrode active material layer.
Therefore, according to the present invention, when forming an electrode active material layer using an aqueous paste, the electrode current collector can be prevented from being corroded, and an increase in reaction resistance can be avoided to produce an electrode excellent in electrical performance. A method can be provided.

  A preferred embodiment of the production method disclosed herein includes subjecting the surface of the barrier layer to a hydrophilic treatment before applying the aqueous paste to the surface of the barrier layer. Thus, the wettability with respect to the aqueous paste of this barrier layer can be improved by performing the hydrophilic treatment to the surface of the barrier layer which consists of a non-aqueous solvent. As a result, the aqueous paste is more easily fixed on the barrier layer, and repelling of the aqueous paste can be prevented.

  In a preferred aspect of the production method disclosed herein, evaporating the non-aqueous solvent is performed simultaneously with the drying treatment of the aqueous paste applied to the surface of the non-aqueous solvent. Since the barrier layer made of the non-aqueous solvent and the aqueous paste applied on the barrier layer are simultaneously dried (the non-aqueous solvent evaporates), the drying process is completed once, and the number of processes can be reduced.

  In a preferred embodiment of the production method disclosed herein, at least before the drying of the aqueous paste applied to the surface of the non-aqueous solvent is completed (typically 50% or more of the total water content of the paste applied product). E.g., when 60% to 90%, particularly preferably 70% to 80% of the water has disappeared), the evaporation of the non-aqueous solvent is completed. Thus, by completing the evaporation of the non-aqueous solvent before the drying of the aqueous paste is completed, high adhesion between the electrode active material layer formed by drying the aqueous paste and the electrode current collector is realized. The

  In one preferred embodiment of the manufacturing method disclosed herein, the electrode current collector is composed of aluminum material or an alloy thereof. An aluminum material or an alloy thereof has various properties preferable as an electrode current collector (particularly a positive electrode current collector) such as a lithium secondary battery, and has a property of being easily corroded by an alkaline aqueous paste. Therefore, when manufacturing an electrode in which the material constituting the electrode current collector is an aluminum material or an alloy thereof, a barrier layer is formed in advance by applying a nonaqueous solvent to the surface of the electrode current collector. The effect by employ | adopting a structure can be exhibited especially.

In a preferred aspect of the production method disclosed herein, the non-aqueous solvent is a fluorinated organic solvent containing fluorine as a constituent element. The fluorinated organic solvent has a property that the specific gravity is larger than that of water, and a typical fluorinated organic solvent does not mix with water (has a hydrophobic property). Therefore, the effect of adopting the configuration of the present invention in which a barrier layer is formed in advance between the electrode current collector and the aqueous paste can be particularly exhibited.
In addition, when such a fluorine-based organic solvent is used, fluorine remains when the solvent is evaporated. As a result, the electrode current collector and the electrode active material layer are formed on the electrode current collector. compound constituting the C-F bonds such that there is C-F bond is formed, may be disposed between. Due to the presence of the C—F bond, the electrode active material layer after the drying is completed can reduce the amount of moisture in the electrode. Therefore, when a battery is formed using such an electrode, the effect that the irreversible capacity at the time of initial charge can be reduced is also obtained.
Therefore, as another aspect of the present invention, there is provided an electrode for a secondary battery in which an electrode active material layer mainly composed of an electrode active material is formed on an electrode current collector. That is, the electrode for a secondary battery provided by the present invention has a compound containing a C—F bond between the electrode current collector and the electrode active material layer.

  Further, according to the present invention, the secondary battery electrode manufactured by any of the methods disclosed herein or the secondary battery constructed using the secondary battery electrode disclosed herein (for example, a lithium secondary battery). Battery). Since the secondary battery is constructed by using the secondary battery electrode as at least one electrode (preferably positive electrode), it can exhibit better battery performance.

  Such a secondary battery is suitable as a battery mounted on a vehicle such as an automobile. Therefore, according to the present invention, a vehicle including any of the secondary batteries disclosed herein is provided. In particular, since the lightweight and high output can be obtained, the secondary 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). A vehicle (for example, an automobile) provided as a power source of an electric vehicle is preferable.

It is explanatory drawing which shows typically schematic structure of the electrode manufacturing apparatus which concerns on one Embodiment. It is a schematic cross-sectional view of a current collector for explaining a manufacturing intermediate process in the manufacturing method of the electrode according to the embodiment (the positive electrode). It is a schematic cross-sectional view of a current collector for explaining a manufacturing intermediate process in the manufacturing method of the electrode according to the embodiment (the positive electrode). It is a schematic cross-sectional view of a current collector for explaining a manufacturing intermediate process in the manufacturing method of the electrode according to the embodiment (the positive electrode). It is a schematic cross-sectional view of a current collector for explaining a manufacturing intermediate process in the manufacturing method of the electrode according to the embodiment (the positive electrode). The state of the interface between the positive electrode current collector and the positive electrode active material layer according to one embodiment is an explanatory view schematically showing. It is a perspective view which shows typically the external shape of the lithium secondary battery which concerns on one Embodiment. It is a longitudinal cross-sectional view which follows the IV-IV line in FIG. It is a side view which shows typically the vehicle (automobile) provided with the lithium secondary battery which concerns on this invention.

  Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than matters specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

  As a preferred embodiment of a method for producing an electrode for a secondary battery disclosed herein, a lithium secondary battery (typically a lithium secondary battery) in which an electrode active material layer is formed on the surface of an electrode current collector. A method for producing a positive electrode for an ion battery will be described in detail by way of example, but the application target of the present invention is not intended to be limited to such an electrode or battery.

  Hereinafter, each component of the positive electrode of the lithium secondary battery according to the present embodiment will be described. The positive electrode for a lithium secondary battery according to the present embodiment can have the same configuration as the conventional one. As a positive electrode current collector constituting such a positive electrode, a conductive material made of a metal having good conductivity is used as in the current collector used in the positive electrode of a conventional lithium secondary battery (typically, a lithium ion battery). A member is preferably used. For example, aluminum or an alloy containing aluminum as a main component can be used. The shape of the positive electrode current collector can vary depending on the shape of the lithium secondary battery, and is not particularly limited, and may be various forms such as a rod shape, a plate shape, a sheet shape, a foil shape, and a mesh shape. Typically, a sheet-like positive electrode current collector made of aluminum is used.

Next, a description will be given material constituting the positive electrode active material layer formed on a surface of the positive electrode current collector.
The positive electrode active material constituting the positive electrode active material layer of the positive electrode according to the present embodiment is not particularly limited in composition and shape as long as it is a positive electrode active material having properties that can achieve the object of the present invention. Typical positive electrode active material, composite oxides containing lithium and at least one transition metal element. For example, cobalt lithium composite oxide (LiCoO ₂ ), nickel lithium composite oxide (LiNiO ₂ ), manganese lithium composite oxide (LiMn ₂ O ₄ ), or nickel-cobalt-based LiNi _x Co _1-x O ₂ ( 0 <x <1), cobalt / manganese-based LiCo _x Mn _1-x O ₂ (0 <x <1), nickel / manganese-based LiNi _x Mn _1-x O ₂ (0 <x <1) and LiNi as represented by _{x Mn 2-x O 4 (} 0 <x <2), a so-called binary lithium-containing composite oxide containing two kinds of transition metal elements, or nickel cobalt containing three transition metal elements A ternary lithium-containing composite oxide such as manganese may be used.
The positive electrode active material has a general formula of LiMAO ₄ (where M is at least one metal element selected from the group consisting of Fe, Co, Ni and Mn, and A is P, Si, S and is an element selected from the group consisting of V. polyanionic compound are expressed in) it is also preferably used. In the above general formula, A is P and / or Si (for example, LiFePO ₄ , LiFeSiO ₄ , LiCoPO ₄ , LiCoSiO ₄ , LiFe _0.5 Co _0.5 PO ₄ , LiFe _0.5 Co _0.5 SiO ₄ given as _{LiMnPO 4, LiMnSiO 4, LiNiPO 4} , LiNiSiO 4) is particularly preferred polyanionic compound.

  The compound which comprises such a positive electrode active material can be prepared and provided by a conventionally well-known method, for example. For example, the oxide can be prepared by mixing several raw material compounds appropriately selected according to the atomic composition at a predetermined molar ratio and firing the mixture at a predetermined temperature by an appropriate means. Further, the fired product is pulverized, granulated and classified by an appropriate means to obtain a granular positive electrode active material powder substantially composed of secondary particles having a desired average particle size and / or particle size distribution. be able to. It should be understood that characterizes any out process itself present invention of the positive electrode active material (lithium-containing composite oxide powder and the like).

  In addition, when a conductive material is included in the positive electrode active material layer formed on the positive electrode according to the present embodiment, the conductive material may be any material that has been conventionally used in this type of secondary battery. It is not limited to the conductive material. For example, carbon materials such as carbon powder and carbon fiber can be used. As the carbon powder, various carbon blacks (for example, acetylene black, furnace black, ketjen black), graphite powder, and the like can be used. Among these, you may use together 1 type, or 2 or more types.

  Furthermore, as a binder (binder) contained in the positive electrode active material layer formed in the positive electrode according to the present embodiment, an aqueous paste (typically a paste or slurry) is used as the composition for forming the positive electrode active material layer. Therefore, a polymer material that dissolves or disperses in water can be preferably employed. Cellulose polymers such as carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), etc .; polyvinyl alcohol (PVA) And the like are exemplified. Examples of polymer materials that can be dispersed in water (water-dispersible) include fluorine-based polymers such as polyethylene oxide (PEO), polytetrafluoroethylene (PTFE), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). Resins; vinyl acetate copolymers; rubbers such as styrene butadiene rubber (SBR).

  Here, the “aqueous paste” is a concept indicating a composition using water or a mixed solvent mainly composed of water (aqueous solvent) as a dispersion medium of the active material. As the solvent other than water constituting the 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.

Next, the manufacturing method of the positive electrode (typically positive electrode sheet) for lithium secondary batteries which concerns on this embodiment is demonstrated, referring FIG. 1 and FIG. 2A-FIG. 2D.
As shown in FIG. 1, the electrode manufacturing apparatus 200 according to this embodiment is roughly divided into an unwinding roll 205, a non-aqueous solvent application unit 220, a hydrophilic treatment unit 225, a paste application unit 230, a drying furnace 235, and a winding unit. A take-up roll 210 is provided.
As shown in FIG. 1, first, an aluminum sheet-like positive electrode current collector (electrode current collector) 62 having a thickness of about 10 μm to 30 μm is prepared. Then, the positive electrode current collector 62 is sent out from the unwinding roll 205, and a nonaqueous solvent (nonaqueous solvent having a specific gravity larger than water) is applied to the entire surface of the positive electrode current collector 62 in the nonaqueous solvent application unit 220. Then, a barrier layer 63 made of a non-aqueous solvent is formed (see FIG. 2A).

As the non-aqueous solvent, a solvent having a specific gravity greater than that of water can be suitably used. In particular, those not compatible with water (that is, not mixed with water) are preferable. A typical example is a fluorine-based organic solvent, that is, a linear polymer composed of C and F (typically perfluorocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, etc.) or a mixture thereof. For example, the product name “Florinato (registered trademark)” manufactured by Sumitomo 3M Limited can be suitably used.
Here, it is preferable to adjust the boiling point of the non-aqueous solvent in order to complete the evaporation of the non-aqueous solvent before the drying of the aqueous paste described below is completed. The boiling point of the nonaqueous solvent is preferably about 100 ° C to 150 ° C. As a method of adjusting the boiling point of the nonaqueous solvent, for example, a method of controlling the molecular weight of water-insoluble agents. For example, when perfluorocarbon (for example, “Fluorinart (registered trademark)” described above) is used as the non-aqueous solvent, it is preferably a perfluorocarbon having 8 to 10 linear carbon atoms. When the linear carbon number is too smaller than the above range, the boiling point of the non-aqueous solvent becomes too low and the evaporation may be completed quickly. For this reason, when the evaporation of the non-aqueous solvent is completed, the aqueous paste still contains sufficient solvent (typically water), and the corrosion reaction occurs when the alkaline solvent comes into contact with the positive electrode current collector. There is a fear. On the other hand, if the straight-chain carbon number is too larger than the above range, the boiling point of the non-aqueous solvent becomes too high and the evaporation may be completed late. For this reason, when the aqueous paste is completely dried to form the positive electrode active material layer, a non-aqueous solvent still exists between the positive electrode current collector and the positive electrode active material layer, and then the non-aqueous solvent evaporates. Therefore, the adhesion between the positive electrode current collector and the positive electrode active material layer may be reduced.

It is preferable to apply the non-aqueous solvent so that the thickness of the barrier layer made of the non-aqueous solvent is about 1 μm to 5 μm (for example, 0.16 mg / cm ^{2 to} 0.8 mg / cm ² ). More preferably, the thickness of the barrier layer is about 2 μm to 3 μm (for example, 0.32 mg / cm ^{2 to} 0.48 mg / cm ² ). If the thickness of the barrier layer is more than 5 μm, the surface of the barrier layer (non-aqueous solvent) is subjected to a hydrophilization treatment which will be described later, and the hydrophilic layer is applied to the barrier layer whose wettability is improved. Even if the aqueous paste is applied, the barrier layer and the aqueous paste may not be well bound and the aqueous paste may be repelled. On the other hand, if the thickness of the barrier layer is less than 1 μm, the applied aqueous paste may break through the barrier layer (non-aqueous solvent) that has been subjected to a hydrophilic treatment and contact the current collector surface to cause corrosion. .
In addition, as a method of applying the non-aqueous solvent in the non-aqueous solvent application unit 220, for example, by using an appropriate application device such as a gravure coater, a slit coater, or a die coater, the non-aqueous solvent is applied to the positive electrode current collector 62. An aqueous solvent can be applied.

The barrier layer 63 made of a non-aqueous solvent thus formed generally has substantially no polar functional group and thus tends to have high hydrophobicity and water repellency. When an aqueous paste is applied to such a hydrophobic barrier layer, since the wettability of the barrier layer with respect to the aqueous paste is low, the thickness of the applied aqueous paste (and thus the thickness of the positive electrode active material layer obtained after drying) ) Tends to be non-uniform depending on the location.
Therefore, as shown in FIG. 1, after forming the barrier layer 63 made of the non-aqueous solvent, it is preferable to perform a hydrophilic treatment on the surface of the barrier layer 63 in the hydrophilic treatment section 225 (see FIG. 2B). As a typical example of the hydrophilization treatment, a treatment for introducing a polar functional group (hydroxy group in this embodiment) 65 into the barrier layer 63 can be preferably employed. Preferable examples of the polar functional group include polar functional groups containing oxygen (O) (hydroxy group, carboxyl group, aldehyde group, keto group, etc.). In particular, it is effective to perform a hydrophilization treatment capable of introducing at least one selected from a hydroxy group and a carboxyl group. The hydrophilic treatment for introducing the polar functional group containing oxygen includes chemical species containing oxygen (for example, oxygen gas (O ₂ ), ozone (O ₃ ), oxide ion (O ²⁻ ), oxygen radical, oxygen plasma. Or the like) to the barrier layer 63. For example, such a chemical species is applied to the barrier layer 63 by applying a corona discharge treatment, a plasma treatment, an ultraviolet irradiation treatment, or the like (typically, the treatment is performed in an atmosphere containing oxygen). 63 surfaces can be supplied.

Next, an aqueous paste obtained by dispersing a positive electrode active material (for example, lithium cobaltate particles), a conductive material (for example, graphite), and a binder (for example, CMC) in a predetermined solvent (for example, ion-exchanged water) (that is, A positive electrode active material layer forming paste) 67 is prepared.
Then, as shown in FIG. 1, in the paste application unit 230, the prepared aqueous paste 67 is applied onto the barrier layer 63 that has been subjected to a hydrophilic treatment (see FIG. 2C). As a method of applying the aqueous paste 67 in the paste application unit 230, a technique similar to a conventionally known method can be appropriately employed. For example, the aqueous paste 67 can be suitably applied on the barrier layer 63 by using an appropriate application device such as a slit coater, a die coater, or a gravure coater.

Next, as shown in FIG. 1, the positive electrode current collector 62 to which the aqueous paste 67 is applied is fed into the drying furnace 235 in a state where a certain tension is applied by the tension roller 215. Then, in the drying furnace 235, evaporation of the barrier layer 63 made of a nonaqueous solvent formed on the positive electrode current collector 62 and drying of the aqueous paste (positive electrode active material layer forming paste) 67 are simultaneously performed (see FIG. 2D). . The drying temperature is about 70 ° C to 160 ° C, preferably 90 ° C to 110 ° C. The drying time is about 10 seconds to 30 seconds, preferably 22 seconds to 26 seconds. At this time, before the drying of the aqueous paste 67 is completed (typically when the aqueous paste is dried by 50% or more, for example, 60% to 90%, particularly preferably about 70% to 80%), the non-aqueous solvent It is preferable that the evaporation of the barrier layer 63 made of is completed. As described above, by adjusting the boiling point of the non-aqueous solvent, the evaporation of the barrier layer 63 can be completed before the drying of the aqueous paste 67 is completed. Thereby, high adhesiveness can be ensured between the positive electrode active material layer 64 formed by drying the aqueous paste 67 and the positive electrode current collector 62. In addition, since the barrier layer 63 interposed between the positive electrode current collector 62 and the positive electrode active material layer 64 is evaporated, an increase in interface resistance between the positive electrode current collector 62 and the positive electrode active material layer 64 is suppressed. can do.
As a method for the drying it is not particularly limited as long as it can remove excess volatile components. For example, an appropriate drying device such as a hot air device, various infrared devices, an electromagnetic induction device, or a microwave device can be used.

  Figure 2E is an explanatory view showing a state of the interface between the positive electrode current collector 62 and the positive electrode active material layer 64 schematically. As shown in FIG. 2E, when the evaporation of the barrier layer 63 made of a non-aqueous solvent is completed, it is contained between the positive electrode current collector 62 and the positive electrode active material layer 64 in a fluorine-based non-aqueous solvent (for example, fluorinate). Fluorine remains, and as a result, there is a compound constituting the C—F bond 68 such that the C—F bond 68 exists between the positive electrode current collector 62 and the positive electrode active material layer 64 (near the interface). . Due to the presence of the C—F bond 68, the positive electrode active material layer 64 after the drying is completed can reduce the amount of moisture in the electrode. Therefore, when a battery is formed using such electrodes, the irreversible capacity during initial charging can be reduced.

  Then, as shown in FIG. 1, a positive electrode sheet (positive electrode) 66 in which the positive electrode active material layer 64 is formed on the positive electrode current collector 62 is wound up by a winding roll 210. In addition, you may press (compress) before winding up the positive electrode collector 62 provided with the said positive electrode active material layer 64 as needed. The press (compression) method, it can be adopted conventionally known roll press method, a method of compression platen press method. In adjusting the thickness, the thickness may be measured with a film thickness measuring instrument, and the press pressure may be adjusted to compress a plurality of times until a desired thickness is obtained.

  The positive electrode sheet (positive electrode) 66 obtained by the above manufacturing method is provided with a barrier layer 63 made of a non-aqueous solvent on the surface of the positive electrode current collector 62 made of an aluminum material or the like in the manufacturing process. Even when the aqueous paste 67 that can be made alkaline by including a lithium transition metal composite oxide (lithium cobaltate particles in the present embodiment) is used, the reaction between the aqueous paste 67 and the positive electrode current collector 62 is prevented. be able to. Further, since the barrier layer 63 has been subjected to a hydrophilic treatment, the wettability of the barrier layer 63 with respect to the aqueous paste 67 is improved. This makes it possible to uniformly apply the aqueous paste 67 on the barrier layer 63 (uniformity of coating thickness due to the prevention of "repelling"). Further, since the evaporation of the barrier layer 63 is completed before the drying of the aqueous paste 67 is completed, the positive electrode active material layer 64 having high adhesion with the positive electrode current collector 62 can be formed.

  Next, an embodiment in the case where a lithium secondary battery is constructed using the positive electrode will be described. First, the negative electrode suitable for use in combination with the positive electrode (positive electrode sheet 66) described above, the separator or the like will be described. The negative electrode can have the same configuration as before. As a negative electrode current collector constituting such a negative electrode, for example, a copper material, a nickel material, or an alloy material mainly composed of them is preferably used. The shape of the negative electrode current collector can be the same as the shape of the positive electrode. Typically, a sheet-like copper negative electrode current collector is used.

The negative electrode active material contained in the negative electrode active material layer formed on the negative electrode may be any material that can occlude and release lithium. For example, carbon materials such as graphite, lithium-titanium oxide (Li ₄ Examples thereof include oxide materials such as Ti ₅ O ₁₂ ), metals such as tin, aluminum (Al), zinc (Zn), and silicon (Si), or metal materials composed of metal alloys mainly composed of these metal elements. . A typical example is the amount of powdery carbon material made of graphite or the like. For example, graphite particles can be preferably used.

  In addition to the negative electrode active material, the negative electrode active material layer formed on the negative electrode can contain one or more materials that can be blended in the positive electrode active material layer as necessary. As such a material, various materials that can function as a binder as listed as a constituent material of the positive electrode active material layer can be similarly used.

  The negative electrode according to the present embodiment is a paste-like composition (hereinafter referred to as negative electrode active material layer formation) in which a negative electrode active material, a binder, and the like are dispersed in an appropriate solvent (water, organic solvent, etc.) similar to the conventional one. Preparation paste). The prepared negative electrode active material layer forming paste is applied to the negative electrode current collector, dried, and then compressed (pressed) to form the negative electrode current collector and the negative electrode active material formed on the negative electrode current collector A negative electrode provided with a layer can be produced.

  Moreover, as a separator used with a positive electrode and a negative electrode, the separator similar to the past can be used. For example, a porous sheet made of resin (a microporous resin sheet) can be preferably used. As a constituent material of such a porous sheet, polyethylene (PE), polypropylene (PP), polyolefin-based resins such as polystyrene are preferred. In particular, a porous structure such as a PE sheet, a PP sheet, a two-layer structure sheet in which a PE layer and a PP layer are laminated, and a three-layer structure sheet in which one PE layer is sandwiched between two PP layers. A polyolefin sheet can be suitably used. When a solid electrolyte or a gel electrolyte is used as the electrolyte, a separator may not be necessary (that is, in this case, the electrolyte itself can function as a separator).

As the electrolyte, the same electrolyte as a non-aqueous electrolyte (typically, an electrolytic solution) conventionally used for a lithium secondary battery can be used without particular limitation. Such a non-aqueous electrolyte typically has a composition in which a suitable non-aqueous solvent (organic solvent) contains a lithium salt that can function as an electrolyte. Above the electrolyte can be appropriately selected and used lithium salts conventionally used in lithium secondary batteries. Examples of the lithium salt include LiPF ₆ , LiClO ₄ , LiAsF ₆ , Li (CF ₃ SO ₂ ) ₂ N, LiBF ₄ , LiCF ₃ SO _{3 and the} like. Such electrolytes can be used alone or in combination of two or more. A particularly preferred example is LiPF ₆ . Examples of the non-aqueous solvent include carbonates such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and propylene carbonate (PC). Such non-aqueous solvents can be used alone or in combination of two or more.

Hereinafter, although one form of a lithium secondary battery provided with the said positive electrode sheet (positive electrode) 66 is demonstrated, referring drawings, it does not intend limiting this invention to this embodiment. That is, as long as the positive electrode according to this embodiment is employed, the shape (outer shape and size) of the lithium secondary battery to be constructed is not particularly limited. Battery outer case square shape, may be a shape such as a cylindrical shape, or may be a small button shape. Moreover, the thin sheet | seat type comprised by a laminated film etc. may be sufficient as an exterior. In the following embodiment, a rectangular battery will be described.
In addition, in the following drawings, the same code | symbol is attached | subjected to the member and site | part which show | plays the same effect | action, and the overlapping description may be abbreviate | omitted. Moreover, the dimensional relationship (length, width, thickness, etc.) in each drawing does not necessarily reflect the actual dimensional relationship.

FIG. 3 is a perspective view schematically showing the lithium secondary battery according to the present embodiment. 4 is a longitudinal sectional view taken along line IV-IV in FIG.
As shown in FIGS. 3 and 4, the lithium secondary battery 10 according to the present embodiment includes the above-described lithium secondary battery constituent materials (the active material for each positive and negative electrode, the current collector for each positive and negative electrode, the separator, etc.). An electrode body 50 is provided, and a battery case 15 having a rectangular shape (typically a flat rectangular parallelepiped shape) that accommodates the electrode body 50 and a suitable nonaqueous electrolyte (typically, an electrolyte).

  The case 15 includes a box-shaped case main body 30 in which one of the narrow surfaces in the flat rectangular parallelepiped shape is an opening 20, and the opening 20 is attached (for example, welded) to the opening 20. And a lid 25 for closing. As a material constituting the case 15, the same material as that used in a general lithium secondary battery can be used as appropriate, and there is no particular limitation. For example, a metal (for example, aluminum, steel, etc.) container, a synthetic resin (for example, a polyolefin resin, a high melting point resin such as a polyamide resin, etc.), or the like can be preferably used. The case 15 according to the present embodiment is made of, for example, aluminum.

  The lid body 25 is formed in a rectangular shape that matches the shape of the opening 20 of the case body 30. Further, the lid body 25 is provided with a positive electrode terminal 60 and a negative electrode terminal 70 for external connection, respectively, and a part of these terminals 60, 70 protrudes from the lid body 25 toward the outside of the case 15. It is formed to do. Similarly to the case of the conventional lithium secondary battery, the lid 25 is provided with a safety valve (not shown) for discharging the gas generated inside the case 15 to the outside of the case 15 when the battery is abnormal. It has been. The safety valve can be used without any limitation as long as it has a mechanism that opens and discharges gas to the outside of the case 15 when the pressure inside the case 15 exceeds a predetermined level.

  As shown in FIG. 4, a lithium secondary battery 10 includes a wound electrode body 50 like a normal lithium secondary battery. The electrode body 50 is accommodated in the case main body 30 in a posture in which the winding axis is laid down (that is, in the direction in which the opening 20 is positioned in the lateral direction with respect to the winding axis). The electrode body 50 includes a positive electrode sheet (positive electrode) 66 having a positive electrode active material layer 64 formed on the surface of a long sheet-like positive electrode current collector 62 and a long sheet-like negative electrode current collector (electrode current collector). A negative electrode sheet (negative electrode) 76 having a negative electrode active material layer (electrode active material layer) 74 formed on the surface of 72 is overlapped with two long separator sheets 80 and wound, and the resulting electrode body 50 is obtained. It is formed into a flat shape by crushing it from the side direction and causing it to be ablated.

  Further, in the wound positive electrode sheet 66, the positive electrode current collector 62 is exposed without forming the positive electrode active material layer 64 at one end portion along the longitudinal direction, while the negative electrode is wound. Also in the sheet 76, the negative electrode current collector 72 is exposed at one end portion along the longitudinal direction without forming the negative electrode active material layer 74. A positive electrode terminal 60 is joined to the exposed end of the positive electrode current collector 62, and is electrically connected to the positive electrode sheet 66 of the wound electrode body 50 formed in the flat shape. Similarly, the negative electrode terminal 70 is joined to the exposed end portion of the negative electrode current collector 72 and is electrically connected to the negative electrode sheet 76. The positive and negative electrode terminals 60 and 70 and the positive and negative electrode current collectors 62 and 72 can be joined by, for example, ultrasonic welding, resistance welding, or the like.

  The material and member itself constituting the wound electrode body 50 having the above configuration may be the same as the electrode body of a conventional lithium secondary battery, except that the positive electrode disclosed here (the positive electrode sheet 66) is adopted as the positive electrode. There is no particular limitation.

  The positive electrode sheet 66 is produced as described above. On the other hand, the negative electrode sheet 76 is produced by forming a negative electrode active material layer 74 on a long negative electrode current collector (for example, a long copper foil) 72. That is, a negative electrode active material layer forming paste is prepared by dispersing a negative electrode active material (for example, graphite) and a binder (for example, PVDF) in an organic solvent (for example, NMP). The prepared paste is applied to the negative electrode current collector 72, dried, and then compressed (pressed) to form the negative electrode active material layer 74. The formation method itself of the negative electrode active material layer 74, the conventional and detailed for not characterize the present invention may be the same explanation is omitted.

The positive electrode sheet 66 and the negative electrode sheet 76 produced above are stacked and wound together with two separators (for example, porous polyolefin resin) 80, and the wound electrode body 50 obtained is rolled into the case body 30 with its winding shaft lying sideways. Non-aqueous electrolysis such as a mixed solvent of EC and DMC (for example, a mass ratio of 1: 1) containing an appropriate amount of a supporting salt (for example, a lithium salt such as LiPF ₆ ) (for example, a concentration of 1M). After injecting the liquid, the lithium secondary battery 10 of the present embodiment can be constructed by mounting the lid 25 on the opening 20 and sealing (for example, laser welding).

  In the above-described embodiment, the present invention is applied to the positive electrode of the lithium secondary battery. However, the present invention is not limited to this embodiment, and the present invention can be applied to the negative electrode of the lithium secondary battery, for example. Further, the present invention is not limited to the lithium secondary battery, and the present invention can be applied to electrodes (positive electrode and negative electrode) of a secondary battery such as a nickel metal hydride battery.

  Several 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 examples.

<Preparation of Positive Electrode for Lithium Secondary Battery According to Example 1>
First, an aluminum foil having a thickness of 15 μm was prepared as a positive electrode current collector, and florinert (manufactured by Sumitomo 3M, trade name “FC-3283”) as a non-aqueous solvent was applied to the surface of the aluminum foil using a gravure coater. Thus, a barrier layer was formed. The coating amount of the water-insoluble agent at this time was 0.4 mg / cm ^2, the thickness of the barrier layer is 2.5 [mu] m. And the hydrophilization process was performed with respect to the surface of the florinate apply | coated to the aluminum foil. Specifically, a corona discharge treatment of 150 W · min / m ² was performed in the atmosphere using a general corona discharge treatment apparatus.
Next, the mass ratio of LiNi _0.7 Co _0.3 Al _0.03 O ₂ as the positive electrode active material, acetylene black, PTFE, CMC, and PEO is 87: 10: 1: 1: 1. Thus, these materials were dispersed in ion exchange water to prepare a positive electrode active material layer forming paste. The paste was applied to both surfaces of the above-described hydrophilic layer so that the total coating amount on both surfaces was 10 mg / cm ² (based on solid content), and then dried at 95 ° C. for 1 minute. After drying, to prepare a positive electrode sheet comprising a positive electrode active material layer of the coating was pressed.

<Preparation of Positive Electrode for Lithium Secondary Battery According to Comparative Example 1>
A positive electrode active material layer forming paste positive electrode active material similar to that in Example 1 was applied to both sides of a 15 μm thick aluminum foil not coated with a nonaqueous solvent, with a total coating amount of 10 mg / cm ² (solid content) on both surfaces. The film was applied at a temperature of 95 ° C. for 1 minute. After drying, to prepare a positive electrode sheet comprising a positive electrode active material layer of the coating was pressed.

[Peel strength test]
Using a commercial tensile tester and evaluated for peel strength of each of the positive electrode active material layer.
The positive electrode sheets for lithium secondary batteries according to Example 1 and Comparative Example 1 prepared above were punched into a circular shape with punches, and test pieces were prepared. And this test piece was fixed to the mount frame of the tensile tester. At this time, the positive electrode current collector was fixed to the gantry so that the positive electrode active material layer was on the upper side in the vertical direction (aluminum foil). Then, one side of double-sided tape (φ10mm) is attached to the lower end of the tension jig, the other side is attached to the positive electrode active material layer, and the tension jig is pulled upward at a rate of 0.5mm / sec. The peel strength (tensile strength) [N / m] when the positive electrode active material layer was peeled from the positive electrode current collector was measured. The measurement results are shown in Table 1.

  As shown in Table 1, according to the peel strength test result, it was confirmed that the positive electrode sheet according to Example 1 had a higher peel strength of the positive electrode active material layer than the positive electrode sheet according to Comparative Example 1. This is because, in the positive electrode according to Comparative Example 1, the positive electrode current collector is corroded by alkali due to the aqueous paste exhibiting alkali in the manufacturing process of the positive electrode, and the corrosive gas (typically hydrogen gas) generated during the corrosion occurs. This is because voids were formed in the positive electrode active material layer, and the positive electrode sheet according to Example 1 was not corroded by alkali.

<Production of Lithium Secondary Battery According to Example 2>
Using the positive electrode sheet according to Example 1, a 18650 type lithium secondary battery (theoretical capacity: 5 Ah) was produced as follows.
Weighing so that the mass ratio of natural graphite as negative electrode active material, CMC, and SBR is 99: 0.5: 0.5, and dispersing these materials in ion-exchanged water to form a negative electrode active material layer A paste was prepared. The paste was applied to both sides of a 10 μm thick copper foil so that the total coating amount on both sides was 5 mg / cm ² (solid content basis), dried, and then pressed to prepare a negative electrode sheet.
As the non-aqueous electrolyte, a solution obtained by dissolving 1 mol / L LiPF ₆ in a mixed solvent of EC, DMC, and EMC in a volume ratio of 3: 5: 2 was used.
The obtained positive electrode sheet and the negative electrode sheet are rolled together with two separator sheets (polypropylene porous separator), and the obtained wound electrode body is crushed into a flat shape, and is cylindrical with the electrolyte. The lithium secondary battery which concerns on Example 2 was produced by accommodating in a container.

<Production of Lithium Secondary Battery According to Comparative Example 2>
A lithium secondary battery (theoretical capacity 5 Ah) according to Comparative Example 2 was produced in the same manner as Example 2 except that the positive electrode sheet according to Comparative Example 1 was used.

[Reaction resistance measurement]
The lithium secondary batteries according to Example 2 and Comparative Example 2 manufactured as described above were subjected to appropriate conditioning treatment under a temperature condition of 25 ° C. (constant current and constant voltage up to 4.1 V at a charging rate of 0.1 C). The initial charging / discharging process in which the operation of charging at a constant current and constant voltage discharge to 3.0 V at a discharge rate of 0.1 C was repeated three times), and then the SOC was adjusted to 80% SOC. And the reaction resistance was measured with the alternating current impedance method at the frequency of 10 mHz-1MHz on the temperature conditions of -30 degreeC with respect to the lithium secondary battery which concerns on Example 2 and Comparative Example 2. FIG. The obtained resistance values are shown in Table 2.

[Low temperature output measurement]
The lithium secondary battery according to Example 2 and Comparative Example 2, was adjusted to SOC 80% by the constant current and constant voltage charging. Then, under the temperature condition of −30 ° C., each battery in such a charged state is discharged at a constant power of 40 W, 60 W, 80 W and 100 W, and the battery voltage is 2.5 V (discharge cut voltage) from the start of discharge at each discharge power. The time (seconds of discharge) until the time of decrease was measured. The discharge seconds are plotted against the discharge power (W), and the power value at which the discharge seconds are 2 seconds (that is, the output from the SOC 80% state at −30 ° C. to 2.5 V in 2 seconds). Asked. The obtained output is shown in Table 2.

As shown in Table 2, it was confirmed that the reaction resistance at a low temperature (−30 ° C.) was reduced by 12% in Example 2 as compared with Comparative Example 2. Further, from the result of the low temperature output measurement, it was confirmed that the output of Example 2 was increased by 20% compared with the output of Comparative Example 2.
Summarizing the above measurement results, the positive electrode according to Example 1 had a high adhesion between the positive electrode current collector and the positive electrode active material layer because no corrosion reaction due to alkali occurred in the positive electrode current collector. It was shown that Moreover, it was shown that the lithium secondary battery which concerns on Example 2 constructed | assembled using the positive electrode which concerns on Example 1 is excellent in low-temperature output while the raise of reaction resistance is suppressed.

  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.

  The electrode according to the present invention is an electrode that prevents corrosion of the electrode current collector and prevents an increase in reaction resistance. Due to such characteristics, a secondary battery (for example, a lithium secondary battery) including the electrode according to the present invention can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Therefore, according to the present invention, as shown in FIG. 5, a vehicle including such a lithium secondary battery 10 (which may be in the form of an assembled battery formed by connecting a plurality of such batteries 10 in series) as a power source. 100 (typically automobiles, in particular automobiles equipped with electric motors such as hybrid cars and electric cars) can be provided.

DESCRIPTION OF SYMBOLS 10 Lithium secondary battery 15 Battery case 20 Opening part 25 Cover body 30 Case main body 50 Winding electrode body 60 Positive electrode terminal 62 Positive electrode collector (electrode collector)
63 Barrier layer (non-aqueous solvent)
64 Positive electrode active material layer (electrode active material layer)
65 Hydroxy group 66 Positive electrode sheet (positive electrode)
67 aqueous paste 68 C-F bonds 70 negative electrode terminal 72 negative electrode current collector (electrode current collector)
74 Negative electrode active material layer (electrode active material layer)
76 Negative electrode sheet (negative electrode)
80 Separator 100 Vehicle 200 Electrode Manufacturing Device 205 Unwinding Roll 210 Winding Roll 215 Tension Roller 220 Nonaqueous Solvent Application Unit 225 Hydrophilization Processing Unit 230 Paste Application Unit 235 Drying Furnace

Claims (9)

A method for producing an electrode for a secondary battery in which an electrode active material layer mainly composed of an electrode active material is formed on an electrode current collector,
Applying a non-aqueous solvent having a specific gravity greater than that of water to the surface of the electrode current collector to form a barrier layer made of the non-aqueous solvent;
At least the electrode active material and an aqueous solvent and the formed by mixing an aqueous paste to be applied to the surface of the barrier layer,
Evaporating the non-aqueous solvent forming the barrier layer;
A method for producing an electrode for a secondary battery.   The electrode manufacturing method according to claim 1, comprising applying a hydrophilic treatment to the surface of the barrier layer before applying the aqueous paste to the surface of the barrier layer.   The electrode manufacturing method according to claim 1, wherein evaporating the non-aqueous solvent is performed simultaneously with a drying treatment of the aqueous paste applied to the surface of the non-aqueous solvent.   The electrode manufacturing method according to claim 3, wherein the evaporation of the non-aqueous solvent is completed at least before the drying of the aqueous paste applied to the surface of the non-aqueous solvent is completed.   The electrode current collector is composed of aluminum material or an alloy thereof, a method of manufacturing an electrode according to any one of claims 1 to 4.   The non-aqueous solvent, fluorine is fluorine-based organic solvent containing as a constituent element, a method of manufacturing an electrode according to any one of claims 1 to 5. An electrode for a secondary battery in which an electrode active material layer mainly composed of an electrode active material is formed on an electrode current collector,
An electrode for a secondary battery having a compound constituting the C—F bond on the electrode current collector such that a C—F bond exists between the electrode current collector and the electrode active material layer. .   The secondary battery provided with the electrode for secondary batteries obtained by the manufacturing method in any one of Claim 1 to 6, or the electrode for secondary batteries of Claim 7.   A vehicle comprising the secondary battery according to claim 8.

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