JP2010086866A - Electrode sheet and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve conductivity of an electrode sheet. <P>SOLUTION: The electrode sheet 100 has an electrode material 108 containing an electrode active material held by a collector 311c. The collector 311c includes a sheet-shaped base material 102 and intermediate layers 104, 106 arranged on a surface of the base material 102. The intermediate layers 104, 106 have a laminated structure where a first film 104 made of conductive metal and a second film 106 made of metallic carbide are interposed in this order on the surface of the base material 102. Then, the electrode material 108 is held on the second film 106. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrode sheet in which an electrode material containing an electrode active material is coated on the surface of a current collector. Such an electrode sheet is used for a battery, for example.

As a constituent element of a battery (for example, a secondary battery such as a lithium ion secondary battery), it is known to use an electrode sheet having a configuration in which an electrode material containing an electrode active material is held on the surface of a current collector. As the current collector, one having at least a surface portion made of a conductive material is used. A typical current collector is a foil (metal foil) made of a conductive metal such as aluminum (Al).
By the way, in order to reduce the internal resistance of the battery and improve the battery performance, it is desirable to improve the conductivity between the electrode material and the current collector. However, the surface of the metal foil may be covered with an oxide film formed during rolling or the like, and the metal surface is easily oxidized, so that a natural oxide film is easily formed. The presence of such an oxide film (that is, metal oxide) can be a factor that decreases the conductivity of the electrode material and the current collector.

In Patent Document 1, the surface of the current collector is etched using any one of plasma etching, sputter etching, and ion beam etching in a reduced-pressure atmosphere before the step of forming the electrode layer on the current collector. In addition, it is described that a film layer having conductivity is formed on the surface of the current collector. In this case, the oxide film on the surface of the current collector is removed by etching, and a film layer having good conductivity is formed on the current collector from which the oxide film has been removed. It is said that the conductivity between the electrode layer and the electrode layer can be improved.
Japanese Patent Laid-Open No. 11-250900

However, the removal of the oxide film by the method described in Patent Document 1 requires a considerable amount of time and energy. Moreover, even if a considerable amount of time and energy is spent, the oxide film is formed again as soon as the removed current collector is left in contact with the air. For this reason, it is difficult to provide an electrode layer on the current collector with the oxide film on the current collector surface completely removed, and the conductivity between the electrode material and the current collector is reduced to some extent by such an oxide film. The fact is that it is unavoidable.
It is an object of the present invention to provide a new electrode sheet that can suppress the influence of such an oxide film to a low level and make the conductivity of the electrode material and the current collector good, and a method for manufacturing the same. Another object of the present invention is to provide a secondary battery and other batteries using such an electrode sheet, and a method for producing the same. Still another object is to provide an assembled battery using the battery and a vehicle having the assembled battery.

In the electrode sheet according to the present invention, an electrode material containing an electrode active material is held by a current collector. In this electrode sheet, the current collector includes a sheet-like base material and an intermediate layer provided on the surface of the base material. The intermediate layer has a laminated structure in which a first film made of a conductive metal and a second film made of a metal carbide overlap each other on the surface of the base material in this order. An electrode material is held on the second film.
According to such an electrode sheet, since the second film made of a metal carbide that is difficult to oxidize is disposed on the current collector surface (interface with the electrode material), the electrode material and the first film are interposed through the second film. The conductivity can be made good.

  The base material can be, for example, a metal foil having an oxide film at the interface with the intermediate layer. In this case, when an external force acts on the current collector, a defect occurs in the oxide film. At this time, since the oxide film is covered with the intermediate layer, the metal exposed from the portion where the defect is generated is oxidized again, unlike the current collector in which the surface of the base material (metal foil) is exposed. Never happen. Such a defect site can be useful for making the electrical conductivity between the first film and the current collector base material good. Therefore, according to the structure of this invention, the electroconductivity of an electrode material and a collector can be made into a favorable state irrespective of presence of an oxide film. In other words, good conductivity between the electrode material and the current collector can be realized even if part or all of the time and energy for removing the oxide film is omitted. That is, the productivity of the electrode sheet can be improved by eliminating the process of removing the oxide film or by performing a simple process (such as an etching process).

  As a constituent material of the first film, for example, a metal containing Al as a main component can be used. The second film can be formed of a metal carbide containing WC as a main component. Moreover, as a base material, aluminum foil can be employ | adopted preferably, for example.

  Such an electrode sheet can be used as at least either a positive or negative electrode sheet in a secondary battery having an electrode body with a separator interposed between positive and negative electrode sheets.

  Hereinafter, an electrode sheet and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to the drawings.

  In the electrode sheet, an electrode material containing an electrode active material is coated on the surface of the current collector. For example, a metal foil such as an aluminum foil or a copper foil is often used as the current collector. If the surface of the metal foil is left as it is, an oxide film is formed. The oxide film may reduce the conductivity between the electrode material and the current collector (metal foil). Even if the electrode material is applied after removing the oxide film, the metal exposed by the above process will be oxidized immediately when exposed to the air. The oxide film on the surface of the current collector is completely removed. It is difficult to obtain a finished electrode sheet. Therefore, the present inventor has devised the present invention by intensively studying whether the conductivity of the electrode material and the current collector can be improved even if the oxide film remains.

In this embodiment, the current collector of the electrode sheet 100 includes a sheet-like base material 102 and intermediate layers 104 and 106 provided on the surface of the base material 102 as shown in FIG. The intermediate layers 104 and 106 have a laminated structure in which a first film 104 made of a conductive metal and a second film 106 made of a metal carbide overlap each other on the surface of the base material 102 in this order. An electrode material 108 is held on the second film 106.
Although the first film 104 and the second film 106 are thin films that are much thinner than the base material 102, in FIG. 1, for convenience of illustration, the first film 104 and the second film 106 are drawn thicker than actual. ing.

  In this embodiment, an aluminum metal foil (aluminum foil) is used for the base material 102 of the current collector. When the aluminum foil 102 is left untreated, the surface is immediately oxidized, and an oxide film (natural oxide film) is formed. The aluminum oxide film has low conductivity and can be damaged by a slight impact.

As shown in FIG. 1, the electrode sheet 100 includes a first film 104 made of a conductive metal and a second film 106 made of a metal carbide on the surface of an aluminum foil 102 as a base material of a current collector. Are stacked in this order. An electrode material 108 is applied to the surface of the second film 106.
According to the electrode sheet 100 having such a configuration, good conductivity is exhibited inside the first film 104 made of a conductive metal. Further, since the first film 104 is covered with the second film 106, an oxide film is prevented from being formed on the surface of the first film 104, and good conductivity between the first film 104 and the second film 106 is achieved. Can be secured. Further, since the second film 106 is made of a metal carbide, it is difficult to be oxidized, and the electrical conductivity between the electrode material 108 and the first film 104 can be made good.

  As the first film 104, for example, aluminum (Al) is preferably used. Aluminum (Al) can be obtained at a low cost as a material for forming the first film 104, and the manufacturing cost can be kept low. Note that the first film 104 is not limited to aluminum (Al), and for example, a metal (eg, stainless steel (SUS)) containing iron (Fe) as a main component may be used. Various stainless steels can be adopted as the stainless steel (SUS) used as the first film 104, and for example, SUS316, SUS304, or the like can be used. Since these stainless steels (SUS) have high corrosion resistance to the electrolytic solution, they are suitable as a constituent material of the first film 104. In addition to Al and SUS, niobium (Nb), tungsten (W), chromium (Cr), and the like may be used as the constituent material of the first film. Other so-called valve metals (valve metals) may be used.

As the second film 106, for example, tungsten carbide (WC) can be used. Tungsten carbide (WC) is suitable for use in the second film 106 of the electrode sheet 100 in terms of conductivity and acid resistance. The metal carbide used for the second film 106 is not limited to tungsten carbide (WC), but, for example, tantalum carbide (TaC), hafnium carbide (HfC), niobium carbide (NbC), molybdenum carbide (Mo ₂ C). Vanadium carbide (VC), chromium carbide (Cr ₃ C ₂ ), titanium carbide (TiC), zirconium carbide (ZrC) may be used. Moreover, you may form with the metal carbide which has either of these metal carbides as a main component.

In this embodiment, an aluminum foil 102 is employed as a base material for the current collector. Note that an oxide film (Al ₂ O ₃ ) having a thickness of the order of nanometers (for example, approximately 5 nm) is formed on the surface of an aluminum foil that is generally distributed as a battery current collector. In this embodiment, the aluminum foil 102 on which the oxide film 102a is formed can be used as a base material.
Further, in this embodiment, aluminum (Al) is used for the first film 104 and tungsten carbide (WC) is used for the second film 106.
The thickness of the first film 104 may be about 5 nm to 1 μm, and preferably about 30 nm to 100 nm in order to ensure appropriate conductivity. In this embodiment, it is approximately 40 nm. Note that the thickness of the first film 104 may be appropriately adjusted in consideration of the type of metal used for the first film 104, the type of the second film 106, and the base material 102. Further, the thickness of the second film 106 is preferably about 5 nm to 50 nm, and in this embodiment, it is about 10 nm.

In such an electrode sheet 100, a first film made of a conductive metal and a second film made of a metal carbide may be formed in this order on the surface of the sheet-like substrate 102 in a reduced-pressure atmosphere.
FIG. 2 shows an example of a film forming apparatus 10 that can be preferably used for carrying out such a film forming process. The film forming apparatus 10 includes a decompression chamber 12, a decompression device 14, a processing atmosphere supply unit 16, a supply reel 22, a film forming roll 24, a take-up reel 26, a first film forming unit 32, a second film forming unit 32, and a second film forming unit 32. And a film forming unit 34.
The decompression chamber 12 is composed of an airtight container having a desired pressure resistance. The decompression device 14 evacuates the decompression chamber 12 by exhausting from the decompression chamber 12 to form a decompressed atmosphere. The processing atmosphere supply unit 16 appropriately supplies a gas necessary for forming an atmosphere suitable for film formation in the decompression chamber 12, such as an inert gas such as argon.
In this embodiment, the base material 102 of the current collector has a belt shape and is wound around the supply reel 22, and is wound around the winding reel 26 after being along the outer periphery of the film forming roll 24.

In this embodiment, the first film forming unit 32 forms a first film (not shown) on the surface of the substrate 102 along the outer periphery of the film forming roll 24 by sputtering. The second film forming unit 34 is disposed on the downstream side of the first film forming unit 32 in the path of the base material 102. The second film forming unit 34 forms a second film (not shown) on the first film (not shown) formed on the base material 102 by sputtering.
In this embodiment, sputtering is employed as a method for forming the first film 104 and the second film 106 in the film forming step.

  As a method for forming the first film 104 and the second film 106 as described above, in a vapor deposition method by sputtering, a metal material for vapor deposition made of a predetermined metal species to be attached as a thin film in a vacuum chamber (vacuum chamber) is used. Install as a target. Then, a rare gas element (sputtering gas, typically argon) that is ionized and accelerated by applying a high voltage to discharge is collided with the target, or sputtered gas ions are collided with the target directly by an ion gun. . As a result, target atoms are knocked out, and the target atoms knocked out from the target surface are deposited on the substrate to form a thin film. Examples of the sputtering deposition method include direct current sputtering, high-frequency sputtering, magnetron sputtering, ion beam sputtering, and the like depending on the method of ionizing the sputtering gas. Any of the above sputter deposition methods may be used. For example, the magnetron sputtering method has an advantage that the gas pressure of the sputtering gas can be controlled over a wide range.

Further, the film forming apparatus 10 is not limited to the one shown in FIG. 2, and the formation of the metal intermediate layer by such a vapor deposition method uses a general commercially available vacuum vapor deposition apparatus of a batch processing method or a continuous processing method. It is carried out by doing. Further, such a vacuum deposition apparatus may be provided with a function capable of performing an accompanying process such as an ashing process in the same decompression chamber. In this case, it is preferable because, for example, an ashing process using argon or the like can be performed on the surface of the metal foil body before sputtering deposition. This is because an ashing treatment for about 1 to 5 minutes is effective in cleaning the rolling oil and the like adhering to the surface of the aluminum metal foil. Although not shown, a simple etching process may be performed in the same decompression chamber before the process of forming the first film 104. Thereby, a part or all of the oxide film on the surface of the metal foil can be easily removed, and the first film 104 can be favorably deposited.
Note that the method for forming the first film 104 and the second film 106 is not limited to sputtering. For example, vacuum deposition, electron beam deposition, ion plating, CVD (Chemical Vapor Deposition), plasma CVD, ion implantation, and the like. The method may be adopted.

In this embodiment, as shown in FIG. 1, a first film 104 made of a conductive metal and a second film 106 made of a metal carbide are formed on the surface of an aluminum foil 102 as a base material of a current collector. , In this order. The electrode material 108 is held on the surface of the second film 106.
Note that the second film 106 may be subjected to corona discharge treatment before the electrode material 108 is applied. Such corona discharge treatment is preferably performed in a mixed atmosphere of nitrogen gas and hydrogen gas. Thereby, when the electrode material 108 is applied to the surface of the second film 106, the adhesion of the electrode material 108 can be improved.

In this electrode sheet 100, the second film 106 is made of a metal carbide and is not easily oxidized, so that the conductivity between the electrode material 108 and the first film 104 can be made good.
Moreover, in this embodiment, the electrode sheet 100 uses the aluminum foil 102 as a base material of a collector. An oxide film 102 a is formed on the surface of the aluminum foil 102. Such an oxide film 102a is partially damaged when an external force is applied. As the inventor presumes, for example, the electrode sheet 100 is pressed after the electrode material 108 is applied, and pressure is also applied when the guide roller is rolled. Such pressure causes defects in the oxide film 102a. Since the oxide film 102a is covered with the first film 104, the site where the defect occurs is not oxidized again. For this reason, it is considered that the electrical conductivity between the first film 104 and the inside of the current collector base material 102 is in a good state through the defective portion.

  In this case, it is not always necessary to remove the oxide film 102a by etching or the like. Regardless of the presence of the oxide film 102a, the conductivity between the first film 104 and the current collector base material 102 is good. Can be. That is, even if the oxide film 102a remains, the required conductivity between the electrode material 108 and the current collector can be ensured. Accordingly, the step of removing the oxide film 102a by etching or the like may be omitted, or a simple etching process may be performed, so that the productivity of the electrode sheet can be improved.

  Such an electrode sheet 100 is used as an electrode sheet for a secondary battery. As an embodiment of the secondary battery, a secondary battery having a wound electrode body can be given. Examples of such secondary batteries include a lithium-ion secondary battery and a nickel-hydride secondary battery. Hereinafter, a lithium ion secondary battery will be described as an example. In the case of other secondary batteries such as a nickel metal hydride secondary battery, the current collector foil, the electrode active material, the electrolytic solution, and the like may be appropriately changed.

  For example, as shown in FIG. 4, the lithium ion secondary battery 1000 is configured in a rectangular metal battery case 300. The wound electrode body 310 is accommodated in the battery case 300.

  In this embodiment, the wound electrode body 310 includes a positive electrode sheet 311 and a negative electrode sheet 313 as band-like electrodes as shown in FIG. Moreover, the 1st separator 312 and the 2nd separator 314 are provided as a strip | belt-shaped separator. The positive electrode sheet 311, the first separator 312, the negative electrode sheet 313, and the second separator 314 are stacked and wound in this order. Here, the positive electrode sheet 311 and the negative electrode sheet 313 correspond to the electrode sheets according to the present invention, respectively. The positive electrode sheet 311 is a positive electrode sheet, and the negative electrode sheet 313 is a negative electrode sheet.

In this embodiment, the positive electrode sheet 311 is coated with an electrode material 311d containing a positive electrode active material (electrode active material) on both surfaces of the current collector 311c. Examples of the positive electrode active material included in the electrode material 311d include a ternary active material (LiNiMnCoO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium cobaltate (LiCoO ₂ ), and lithium nickelate (LiNiO ₂ ). Etc.
In this embodiment, the current collector 311c includes, as shown in FIG. 1, a first film 104 made of conductive metal (here, Al) as an intermediate layer on the surface of a base material 102 made of aluminum foil. The second film 106 made of a metal carbide (here, WC) has a stacked structure in which these layers are stacked in this order. In the positive electrode sheet 311, an electrode material 311 d is coated on the surface of the second film 106.

In this embodiment, the negative electrode sheet 313 is coated with an electrode material 313d containing a negative electrode active material (electrode active material) on both surfaces of a strip-shaped current collector 313c made of copper foil. Examples of the negative electrode active material contained in the electrode material 313d include carbon-based materials such as graphite and amorphous carbon, lithium-containing transition metal oxides, transition metal nitrides, and the like.
Note that the electrode materials 311d and 313d may be, for example, mixed in an aqueous or solvent-based paste with an electrode active material, applied to the current collectors 311c and 313c, and dried.
The separators 312 and 314 are membranes that are permeable to ionic substances. In this embodiment, polypropylene microporous membranes are used.

  In this embodiment, the electrode materials 311d and 313d are applied to one side in the width direction of the current collectors 311c and 313c, and are applied to the edges of the current collectors 311c and 313c on the opposite side in the width direction. Absent. A portion where the electrode materials 311d and 313d are applied to the current collectors 311c and 313c is referred to as a coating portion 311a and 313a, and a portion where the electrode materials 311d and 313d are not applied to the current collectors 311c and 313c is not applied. It is called the engineering parts 311b and 313b.

  As shown in FIG. 5, the wound electrode body 310 is a cross-sectional view in the width direction showing a state in which a positive electrode sheet 311, a first separator 312, a negative electrode sheet 313, and a second separator 314 are sequentially stacked. . The coating part 311a of the positive electrode sheet 311 and the coating part 313a of the negative electrode sheet 313 are opposed to each other with the separators 312 and 314 interposed therebetween. As shown in FIG. 5, uncoated portions 311 b and 313 b of the positive electrode sheet 311 and the negative electrode sheet 313 are separators 312 and 314 on both sides in a direction (winding axis direction) orthogonal to the winding direction of the wound electrode body 310. Each protrudes from. The uncoated portions 311b and 313b of the positive electrode sheet 311 and the negative electrode sheet 313 form positive and negative current collecting portions 311b1 and 313b1 of the wound electrode body 310, respectively.

The wound electrode body 310 is accommodated in the battery case 300 as shown in FIG. As shown in FIG. 4, the battery case 300 is provided with a positive terminal 301 and a negative terminal 303. The positive terminal 301 is electrically connected to the positive current collector 311b1 (see FIG. 5) of the wound electrode body 310. The negative electrode terminal 303 is electrically connected to the negative electrode current collector 313b1 (see FIG. 5) of the wound electrode body 310. An electrolytic solution is injected into the battery case 300. The electrolytic solution can be composed of a nonaqueous electrolytic solution such as a mixed solvent such as diethyl carbonate and ethylene carbonate containing an appropriate amount of an appropriate electrolyte salt (for example, a lithium salt such as LiPF ₆ ).

  In the lithium ion secondary battery 1000, charging / discharging is performed via the positive electrode terminal 301 and the negative electrode terminal 303. At the time of charging / discharging, lithium ions go back and forth through the strip separators 312 and 314 between the coating part 311a of the positive electrode sheet 311 and the coating part 313a of the negative electrode sheet 313.

  Hereinafter, the positive electrode sheet 311 of the lithium ion secondary battery 1000 will be described.

  In this embodiment, as shown in FIG. 1, the current collector 311c constituting the positive electrode sheet 311 is electrically conductive as an intermediate layer on an aluminum foil 102 having an oxide film 102a on the surface from above the oxide film 102a. The first film 104 made of a metal having a metal and the second film 106 made of a metal carbide have a laminated structure in which they are stacked in this order. An electrode material 311 d is applied to the surface of the second film 106. As shown in FIG. 6, the first film 104 and the second film 106 are formed on the positive electrode sheet 311 and the aluminum foil 102 having the oxide film 102a on the surface without removing the oxide film 102a. Without using (that is, using the aluminum foil 102 having the oxide film 102a on the surface as the current collector 311cB as it is), the electrode sheet 100B having a structure in which the electrode material 311dB is directly coated on the oxide film 102a; Compare

  In the electrode sheet 100B shown in FIG. 6, the electrode material 311d is directly coated on the oxide film 102a formed on the surface of the aluminum foil 102 (current collector 311cB) without any treatment. In this case, the conductivity between the electrode material 311 dB and the aluminum foil 102 (current collector 311 cB) is reduced by the oxide film 102 a existing on the surface of the aluminum foil 102. Furthermore, not only the oxide film 102a but also the rolling oil used in the rolling process may adhere to the surface of the aluminum foil 102, and the rolling oil (not shown) is also the electrode material 311dB. This can be a factor of reducing the conductivity with the aluminum foil 102. Further, in the configuration of the electrode sheet 100B, when a potential due to charging / discharging repeatedly acts on the oxide film 102a existing at the interface between the current collector 311cB and the electrode material 311dB, the bonding strength between the electrode material 311dB and the current collector 311cB decreases. In some cases, the deterioration of the battery over time, such as the oxide film 102a being dissolved, may progress quickly.

On the other hand, in the positive electrode sheet 311 shown in FIG. 1, rolling oil or the like attached to the surface of the aluminum foil 102 can be removed in the film forming process for forming the first film 104 and the second film 106. Further, since the first film 104 and the second film 106 described above are formed in order on the surface of the aluminum foil 102, the oxidation of the first film 104 is prevented by using the second film 106 as an antioxidant layer. can do. In addition, a thin film made of a metal carbide (here, WC) harder than the base aluminum foil 102 is formed as the second film 106 on the surface of the current collector 311c. For this reason, an external force tends to act on the surface of the aluminum foil 102 in a subsequent process such as a winding process or a pressing process of the electrode sheet 100, and at this time, the oxide film 102a formed on the surface of the aluminum foil 102 is likely to be damaged. it is conceivable that. Therefore, the conductivity between the electrode material 108 and the aluminum foil 102 can be made favorable through the defect of the oxide film 102 a and the first film 104 and the second film 106.
The aluminum foil 102 and the first film 104 are covered with the second film 106, and it is difficult to form an oxide film again. In addition, compared with the case where the electrode material 108 and the aluminum foil 102 are directly bonded, the potential acting on the aluminum foil 102 during charging and discharging can be suppressed to a low level. Therefore, the possibility that the oxide film 102a on the surface of the aluminum foil 102 is dissolved is low, the progress of deterioration of the battery over time can be suppressed, and the life of the battery can be extended.

Such a secondary battery is schematically shown in FIG. In FIG. 7, reference numeral 311 indicates a positive electrode sheet, and reference numeral 313 indicates a negative electrode sheet. Reference numerals 312 and 314 denote separators. Reference numeral 311c denotes a positive current collector, and reference numeral 313c denotes a negative current collector. Reference numeral 311d indicates a positive electrode material, reference numeral 311d1 indicates a positive electrode active material, reference numeral 313d indicates a negative electrode material, and reference numeral 313d1 indicates a negative electrode active material. In this embodiment, as described above, the structure of the electrode sheet 100 according to the present invention is adopted for the positive electrode sheet 311, the reference numeral 104 indicates the first film, and the reference numeral 106 indicates the second film. .
The positive electrode material 311d and the negative electrode material 313d are stacked with a separator 312 or 314 interposed therebetween. In the lithium ion secondary battery, lithium ions move between the positive electrode material 311d and the negative electrode material 313d during charging and discharging. FIG. 8 shows an equivalent circuit of the lithium ion secondary battery. Here, Rs indicates a direct current resistance flowing through the positive electrode current collector. R1 represents the reaction resistance of the positive electrode, and W represents the diffusion resistance of the positive electrode. Here, the diffusion resistance refers to resistance when lithium ions in the active material or the electrolytic solution diffuse and move. R2 represents the reaction resistance of the negative electrode. C1 indicates the capacitance (capacitance) of the positive electrode, and C2 indicates the capacitance (capacitance) of the negative electrode.

According to the knowledge obtained by the present inventor, the resistance of the secondary battery is, for example, at room temperature (20 ° C.), the reaction resistance R1 of the positive electrode is 14%, the reaction resistance R2 of the negative electrode is 11%, and the diffusion resistance W of the positive electrode. Is 36% and the DC resistance Rs is 39%. At a low temperature (−30 ° C.), the reaction resistance R1 of the positive electrode is 55%, the reaction resistance R2 of the negative electrode is 42%, the diffusion resistance W of the positive electrode is 2%, and the direct current resistance Rs is 1%.
In this embodiment, the structure of the electrode sheet 100 according to the present invention is adopted for the positive electrode sheet 311, and the positive electrode material 311 d and the current collector 311 c have good conductivity, so the positive electrode reaction resistance R 1 And DC resistance Rs can be reduced.
For example, when the electrode material 311d is applied without processing the base material (aluminum foil 102) of the positive electrode current collector 311c (comparative example), the surface of the aluminum foil 102 is made of Al as in this embodiment. In the case where the first film 104 and the second film 106 made of WC are sequentially formed (Example), this embodiment can reduce the reaction resistance R1 and the direct current resistance Rs of the positive electrode.

An example of the experimental result obtained by the present inventor is shown. In this case, as shown in FIG. 9, in the Nyquist plot at room temperature (25 ° C.), the plot A of the example shows better results than the plot B of the comparative example. Further, at room temperature (25 ° C.), the example reduces the cell internal resistance of the secondary battery by about 10.8% as compared with the comparative example. In this case, the Nyquist plot at a low temperature (−30 ° C.) is as shown in FIG. 10, and in this case, the plot A of the example shows a better result than the plot B of the comparative example. In addition, at a low temperature (−30 ° C.), the example reduces the cell internal resistance of the secondary battery by about 6.5% compared to the comparative example.
As described above, the electrode sheet 100 according to the present invention has an effect of reducing the cell internal resistance of the secondary battery.

  In the above embodiment, the electrode sheet 100 according to the present invention is applied to the positive electrode sheet 311. In the battery according to the present invention, an electrode sheet 100 having a configuration as shown in FIG. 1 may be applied to at least one of positive and negative electrode sheets.

  For example, the base material 102 of the current collector is an aluminum foil in the above-described embodiment, but is not limited to an aluminum foil, and may be various metal foils such as a copper foil. For example, when the electrode sheet 100 is used for a positive electrode in a lithium ion secondary battery, an aluminum foil may be used for the base material 102 of the current collector. On the other hand, when the electrode sheet 100 is used for the negative electrode, a copper foil may be used for the base material 102 of the current collector.

  Further, the base material of the current collector is not limited to metal, and may be a resin base material 102A as shown in FIG. 3, for example. As such a resin, for example, polypropylene (PP) can be employed. Thus, in the current collector provided with the resin base material 102A, the surface of the first film 104A made of a conductive metal is covered with the second film 106A. Therefore, an oxide film can be prevented from being formed on the surface of the first film 104A, and good conductivity between the electrode material 108A and the first film 104A can be ensured. In such a configuration, the conductivity of the current collector is preferably ensured mainly by the first film 104A, and the material and thickness of the first film 104 are preferably appropriate so as to obtain desired conductivity.

  When the electrode sheets 100 and 100A shown in FIG. 1 or FIG. 3 are used as positive electrode sheets (positive electrode sheets) of a secondary battery, the first films 104 and 104A of the electrode sheets are positive electrodes during charging of the secondary battery. It is preferable to use a metal species that does not dissolve under potential. Preferred metal species depend on the type of secondary battery, but for example, aluminum, stainless steel, titanium (Ti), niobium (Nb), tantalum (Ta), zirconium (Zr), hafnium (Hf), and tungsten (W 1 type or 2 types or more selected from the group consisting of:

  In addition, when the electrode sheets 100 and 100A shown in FIG. 1 or 3 are used as the negative electrode sheet (negative electrode sheet) of the secondary battery, the first films 104 and 104A of the electrode sheet are formed of the secondary battery. You may comprise by the metal seed | species which does not melt | dissolve under the negative electrode potential at the time of discharge, or the metal seed | species which does not alloy with lithium under the negative electrode potential at the time of charge. A preferable metal species is, for example, copper (Cu) and / or nickel (Ni), although it depends on the type of secondary battery.

  As described above, such an electrode sheet is suitable as an electrode sheet for a secondary battery having an electrode body stacked with an electrode sheet and a separator interposed therebetween. As such a secondary battery, for example, as shown in FIG. 4, a battery in which a wound electrode body 310 is configured and accommodated in a battery case may be used. Although not shown in the drawings, a so-called laminate type secondary battery in which a laminated electrode body that is stacked with an electrode sheet and a separator interposed therebetween is covered with a laminate film may be used.

  Further, for example, as shown in FIG. 11, a plurality of such secondary batteries 1000 are combined to form an assembled battery 1000 </ b> A and are mounted as a power source of the vehicle 1. The power source for the vehicle is repeatedly charged and discharged. However, according to the electrode sheet manufacturing method described above, the performance of the secondary battery can be improved and the life of the secondary battery can be increased. This is useful as a secondary battery manufacturing method and manufacturing apparatus.

  As mentioned above, although the example of the manufacturing method and manufacturing apparatus of an electrode sheet was illustrated, the manufacturing method and manufacturing apparatus of the electrode sheet which concern on this invention are not limited to embodiment mentioned above.

  For example, the secondary battery manufactured using the method for manufacturing an electrode sheet of the present invention is exemplified as an application mounted on a vehicle as a power source, but the present invention improves the performance and extends the life of the secondary battery. Contribute to. For this reason, this invention is suitable for the manufacturing method of the secondary battery used not only for vehicles but for various uses.

Sectional drawing of the electrode sheet which concerns on one Embodiment of this invention. The figure which shows an example of the film-forming apparatus. Sectional drawing of the electrode sheet which concerns on other embodiment of this invention. The figure which shows an example of a secondary battery. The figure which shows an example of a wound electrode body. Sectional drawing of the electrode sheet which concerns on a comparative example. The figure which shows the structure of a secondary battery. The circuit diagram which shows the equivalent circuit of a secondary battery. The figure which shows the Nyquist plot in normal temperature. The figure which shows the Nyquist plot in low temperature. The side view which shows the vehicle carrying a secondary battery as a power supply.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Film-forming apparatus 12 Pressure-reducing chamber 14 Pressure-reducing apparatus 16 Processing atmosphere supply part 22 Supply reel 24 Film forming roll 26 Take-up reel 32 First film forming part 34 Second film forming part 100, 100A Electrode sheet (Example)
100B electrode sheet (comparative example)
102 Aluminum foil (base material of current collector)
102A current collector base material 102a oxide film 104, 104A first film 106, 106A second film 108, 108A electrode material 300 battery case 301 positive electrode terminal 303 negative electrode terminal 310 wound electrode body 311 positive electrode sheet (electrode sheet)
311a Coating part 311b Uncoated part 311b1 Positive electrode current collector 311c Current collector (positive electrode current collector)
311d Electrode material 312, 314 Separator 313 Negative electrode sheet 313a Coated part 313b Uncoated part 313b1 Negative electrode current collector 313c Current collector (negative electrode current collector)
313d Electrode material 1000 Lithium ion secondary battery 1000A battery pack

Claims (15)

An electrode sheet containing an electrode active material is held by a current collector,
The current collector includes a sheet-like base material, and an intermediate layer provided on the surface of the base material,
The intermediate layer has a laminated structure in which a first film made of a conductive metal and a second film made of a metal carbide overlap on the surface of the base material in this order,
An electrode sheet in which an electrode material is held on the second film.   The electrode sheet according to claim 1, wherein the base material is a metal foil having an oxide film at an interface with the intermediate layer.   The electrode sheet according to claim 1, wherein the first film is made of a metal having aluminum (Al) as a main component.   The electrode sheet according to any one of claims 1 to 3, wherein the second film is formed of a metal carbide containing tungsten carbide (WC) as a main component.   The electrode sheet according to claim 1, wherein the substrate is an aluminum foil. A secondary battery having an electrode body with a separator sandwiched between positive and negative electrode sheets,
A secondary battery comprising the electrode sheet according to any one of claims 1 to 5 as at least one of positive and negative electrode sheets.   An assembled battery in which a plurality of the secondary batteries according to claim 6 are combined.   A vehicle on which the assembled battery according to claim 7 is mounted as a power source. An electrode sheet manufacturing method for manufacturing an electrode sheet in which an electrode material containing an electrode active material is coated on the surface of a current collector,
The current collector includes a sheet-like base material, and an intermediate layer provided on the surface of the base material,
On the surface of the sheet-like substrate, in a reduced pressure atmosphere, a film forming step for forming a first film made of a conductive metal and a second film made of a metal carbide in this order;
And a coating process of coating an electrode material on the surface of the second film formed in the film forming process.   The said base material is a metal foil which has an oxide film on the surface, The manufacturing method of the electrode sheet of Claim 9 which forms a said 1st film | membrane from on this oxide film.   The film formation step forms the first film and the second film by any one of vacuum deposition, electron beam deposition, sputtering, ion plating, CVD, plasma CVD, and ion implantation. The method for producing the electrode sheet according to 10.   The method for manufacturing an electrode sheet according to claim 9, wherein the first film is made of a metal mainly composed of aluminum (Al).   The method for manufacturing an electrode sheet according to any one of claims 9 to 12, wherein the second film is formed of a metal carbide containing tungsten carbide (WC) as a main component.   The method for producing an electrode sheet according to claim 9, wherein the base material is an aluminum foil. A method for producing a battery having an electrode body with a separator sandwiched between positive and negative electrode sheets,
The manufacturing method of a battery including the manufacturing method of the electrode sheet in any one of Claim 9 to 14 in the manufacturing method of the electrode sheet of either positive or negative at least.

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