JP2008181708A - Manufacturing method of electrode for nonaqueous electrolyte secondary battery, electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrode for a nonaqueous electrolyte secondary battery that reduces damage to a current collector by dispersing impacts generating when active material particles strike against the current collector. <P>SOLUTION: The manufacturing method of the electrode for the nonaqueous electrolyte secondary battery includes a process obtaining aerosol by dispersing active material particles in gas, and a process forming an active material layer on the current collector by intermittently striking the aerosol against the current collector. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a non-aqueous electrolyte secondary battery electrode for forming an active material layer on a current collector, a non-aqueous electrolyte secondary battery electrode, and a non-aqueous electrolyte secondary battery.

In recent years, for the purpose of increasing the capacity of non-aqueous electrolyte secondary batteries, as an electrode manufacturing method, active material particles are dispersed in an air current without melting or evaporating, and the air current is sprayed onto a current collector to obtain active material particles. Has been studied to cause the active material particles to adhere to the current collector surface by this impact force (for example, Patent Documents 1 and 2).
Patent Document 1 proposes a method for producing an electrode by a cold spray method. The particles can be directly bonded to the current collector metal by providing the anchor effect by using the plastic deformation of the current collector metal to bond the particles to the current collector. However, in the cold spray method of Patent Document 1, it is difficult to firmly bond the active material particles to each other. That is, it is difficult to increase the capacity by increasing the thickness of the electrode.

In Patent Document 2, an aerosol in which mixed particles of an active material and a solid electrolyte are dispersed in a gas is sprayed onto a current collector by an aerosol deposition method (hereinafter referred to as an AD method), and the active material and the solid electrolyte are injected. It has been proposed that an electrode is obtained by depositing the mixed particles on a current collector to form an active material layer on the current collector. In the AD method, the electrode can be easily thickened.
However, when an electrode is manufactured by the AD method, it is necessary to use ultrafine particles having a particle size of 3 μm or less, preferably 1 μm or less. If the particle size exceeds 3 μm, the active material layer is not formed densely, In some cases, the breaking strength is reduced, which is not suitable for battery production.
Further, as the positive electrode active material, lithium cobaltate having an average particle diameter of about 10 μm is generally used. However, in the above-described AD method, in order to obtain fine particles that collide with the current collector, it is difficult to further pulverize the fine particles to an average particle size of 1 μm or less, and the yield of the obtained powder is also reduced.

  Further, an aluminum foil having a thickness of 20 μm is generally used for the positive electrode current collector. However, when lithium cobaltate particles having an average particle size of about 10 μm, which are generally used, are jetted onto the current collector by the AD method, the current collector may be deformed due to impact caused by particle collision. In addition, through holes and wrinkles may occur in the current collector. If a battery is constituted by using a positive electrode in which a current collector is deformed or wrinkled, the adhesion with the negative electrode through the separator of the positive electrode is deteriorated. In addition, when a through hole is formed in the current collector, the active material particles are not deposited in the portion where the through hole of the current collector exists, so that the positive electrode capacity is reduced. For these reasons, the charge / discharge characteristics and cycle characteristics of the battery may deteriorate.

As a method for suppressing the deformation of the aluminum foil, it is conceivable to increase the thickness of the aluminum foil, but the battery volume increases and the battery capacity per volume decreases.
In addition, although it is conceivable to reduce the injection speed of the particles injected from the nozzle, the kinetic energy necessary for deposition while adhering to the aluminum foil is not sufficiently given to the active material particles, In addition, the active material particles are difficult to adhere to each other, and the film forming speed is greatly reduced.
JP-A-2005-310502 JP 2005-78985 A

  Therefore, in order to solve the above-described conventional problems, the present invention provides particles having a relatively large particle size made of an active material powder having an average particle size of about 10 μm, which is a general active material for nonaqueous electrolyte secondary batteries. An object of the present invention is to provide a method for producing an electrode for a non-aqueous electrolyte secondary battery capable of forming a uniform active material layer on a current collector by colliding with a current collector made of a metal foil having a thickness of about 20 μm. And In addition, a non-aqueous electrolyte secondary battery electrode is provided in which the active material particles and the active material particles and the current collector are firmly bonded without using a binder, and the capacity density per volume is high. The purpose is to do. Furthermore, it aims at providing the high capacity | capacitance nonaqueous electrolyte secondary battery excellent in cycling characteristics using the said electrode.

Therefore, the method for producing an electrode for a non-aqueous electrolyte secondary battery according to the present invention includes a step of dispersing active material particles in a gas to obtain an aerosol, and intermittently colliding the aerosol with a current collector, thereby collecting the current collector. Forming an active material layer on the electric body.
The gas is preferably at least one selected from the group consisting of inert gas, oxygen gas, nitrogen gas, hydrogen gas, carbon dioxide gas, and dry air.
The active material particle is a lithium-containing composite oxide, or a silicon simple substance, a silicon alloy, a compound containing silicon and oxygen, a compound containing silicon and nitrogen, a simple substance of tin, a tin alloy, a compound containing tin and oxygen, tin And at least one selected from the group consisting of a compound containing carbon and nitrogen, and a carbon material.
The current collector is preferably an aluminum foil, a copper foil, or a nickel foil.
Moreover, this invention relates to the electrode for nonaqueous electrolyte secondary batteries obtained by said manufacturing method.
Furthermore, this invention relates to the nonaqueous electrolyte secondary battery using said electrode.

According to the method for manufacturing an electrode for a non-aqueous electrolyte secondary battery of the present invention, it is possible to disperse the impact when the active material particles collide with the current collector in time series, and therefore the damage to the current collector Can be reduced. Thereby, it can suppress that a wrinkle or a through-hole generate | occur | produces in a collector at the time of active material layer formation. For this reason, even when active material particles having a relatively large particle size having an average particle size of about 10 μm are collided with the current collector, the current collector is not damaged, and the current collector has a thickness of about 20 μm. An active material layer can be formed.
Further, according to the method for producing an electrode for a nonaqueous electrolyte secondary battery of the present invention, without using a binder or a conductive material, the active material particles are firmly bonded to each other and between the active material particles and the current collector, And the electrode for nonaqueous electrolyte secondary batteries with a high capacity | capacitance density per unit volume is obtained.
Furthermore, the non-aqueous electrolyte secondary battery of the present invention can provide a high-capacity non-aqueous electrolyte secondary battery having excellent cycle characteristics by using the electrode.

The present invention relates to a method for producing an electrode for a nonaqueous electrolyte secondary battery by an aerosol deposition method. That is, the method for producing an electrode for a non-aqueous electrolyte secondary battery according to the present invention includes a step of dispersing active material particles in a gas to obtain an aerosol, and intermittently colliding the aerosol with a current collector, thereby A step of intermittently colliding material particles with the current collector, depositing and adhering the active material particles on the current collector, and forming an active material layer on the current collector. Have
Thereby, since the impact when the active material particles collide with the current collector can be dispersed in time series, the damage to the current collector can be reduced. In addition, generation of wrinkles or through holes in the current collector during formation of the active material layer can be suppressed. For this reason, for example, even when active material particles having a relatively large particle size having an average particle size of about 10 μm are collided with a current collector having a thickness of about 20 μm, the current collector is not damaged. An active material layer can be formed on the body.
Further, according to the method for producing an electrode for a nonaqueous electrolyte secondary battery of the present invention, without using a binder or a conductive material, the active material particles are firmly bonded to each other and between the active material particles and the current collector, And the electrode for nonaqueous electrolyte secondary batteries with a high capacity density per volume is obtained.
Furthermore, the non-aqueous electrolyte secondary battery of the present invention can provide a high-capacity non-aqueous electrolyte secondary battery having excellent cycle characteristics by using the electrode.

Hereinafter, an embodiment of a method for producing a nonaqueous electrolyte secondary battery electrode of the present invention will be described with reference to the drawings.
Here, an example of the manufacturing apparatus used for the manufacturing method of the electrode for nonaqueous electrolyte secondary batteries of this invention is shown in FIG. FIG. 1 is a configuration diagram of a manufacturing apparatus based on the AD method. As shown in FIG. 1, a gas cylinder 11 in which a gas for generating aerosol is stored is connected to an aerosol generator 13 via a pipe 12a. A pipe 12 b for sending aerosol to the nozzle 15 is connected between the aerosol generator 13 and the film forming chamber 14. One end of the pipe 12 b is exposed in the aerosol generator 13, and the other end of the pipe 12 b is connected to a nozzle 15 installed in the film forming chamber 14. A substrate (current collector) 16 is disposed on the substrate holder 17 so as to face the nozzle. An exhaust pump 18 for adjusting the degree of vacuum in the film forming chamber 14 is connected to the film forming chamber 14. A predetermined amount of active material powder 20 is charged in the aerosol generator 13 in advance.
In order to obtain an electrode, it is necessary to form an active material layer having a certain area, but a mechanism (not shown) for moving the substrate holder 17 on which the substrate 16 is installed at a constant speed in the horizontal direction or the vertical direction. By providing this, the area of the active material layer can be increased.

  A valve 19 is provided in the middle of a pipe 12 a that connects the gas cylinder 11 and the aerosol generator 13. For example, by alternately opening and closing the valve 19, it is possible to cause the aerosol in a state where particles are dispersed in the gas to intermittently collide with the substrate. The opening and closing of the valve 19 can be controlled by a control device (not shown) such as a computer, for example. By doing in this way, the gas supply (intermittent injection) to the aerosol generator 13 can be controlled automatically.

Next, a process for forming an active material layer using the film forming apparatus will be described. A gas is introduced from the gas cylinder 11 into the aerosol generator 13 through the pipe 12a, and the active material powder 20 is sprinkled into the container to generate an aerosol in which active material particles are dispersed in the gas. The generated aerosol is jetted at high speed from the nozzle 15 toward the substrate 16 through the pipe 12b. The aerosol injection speed is controlled by the shape of the nozzle 15, the length and inner diameter of the pipe 12b, the gas internal pressure of the gas cylinder 11, the exhaust amount of the exhaust pump 18 (internal pressure of the film forming chamber 14), and the like. For example, when the internal pressure of the aerosol generator 13 is tens of thousands Pa, the internal pressure of the film forming chamber 14 is several hundred Pa, and the shape of the opening of the nozzle is a circular shape with an inner diameter of 1 mm, the aerosol generator 13 and the film forming chamber 14, the aerosol injection speed can be set to several hundreds m / sec.
The active material particles in the aerosol that have been accelerated to obtain kinetic energy collide with the substrate 16 and are finely crushed by the impact energy. A dense active material layer is formed by joining the crushed particles to the substrate 16 and joining the crushed particles.

  When the valve 19 is open, the gas is introduced into the aerosol generator 13 and the active material powder is sprinkled into the aerosol generator 13 to generate an aerosol in which active material particles are dispersed in the gas. The aerosol is sprayed from the nozzle 15 toward the substrate 16. When the valve 19 is closed, the above operation is stopped. Aerosol is intermittently injected by opening and closing the valve 19. The number of times the valve 19 is repeatedly opened and closed, the time during which the valve 19 is opened, and the time during which the valve 19 is closed can be controlled by a control mechanism.

The longer the time that the valve 19 is in the open state, the more active material powder is sprayed from the nozzle toward the substrate, the more damage is given to the substrate, and the effect of the present invention is reduced. The opening / closing time of the valve 19 may be set as appropriate according to the active material, the material of the substrate, and the film forming conditions. From the above viewpoint, it may be set on the order of several seconds or less.
In order to control the generation amount of aerosol uniformly, a mechanical vibrator or a stirring blade may be further attached to the aerosol generator 13.

On a current collector made of a metal foil having a thickness of about 20 μm that is generally used for an electrode for a nonaqueous electrolyte secondary battery, active material particles made of an active material powder having an average particle size of about 10 μm are contained in a gas. In the conventional method of forming an active material layer in which aerosol dispersed in the resin is continuously sprayed, damage to the metal foil is large, and the current collector may be deformed, or the current collector may have wrinkles or through holes. .
On the other hand, in the method for manufacturing an electrode for a nonaqueous electrolyte secondary battery according to the present invention, aerosol is intermittently injected from the nozzle to the current collector in the AD method. In this method, unlike the case of continuous injection, since the powder raw material does not collide with the current collector at once, the impact applied to the current collector is mitigated, and even when a thin metal foil is used for the current collector, the current collector No deformation or wrinkles or through holes in the body.

Therefore, in the electrode manufacturing method using the AD method of the present invention, it is possible to use a thinner substrate than before, and it is possible to use an active material powder having a generally used particle size. For example, when a positive electrode is produced by the above method using a lithium-containing composite oxide powder having an average particle diameter of 10 μm as the positive electrode active material and an aluminum foil as the substrate 16, the aluminum foil is as thin as about 5 μm. Can be used.
Further, since it is not necessary to pulverize the active material powder to reduce the impact on the current collector, an electrode having a high energy density per volume can be easily manufactured. By using this electrode, a nonaqueous electrolyte secondary battery having a large capacity density per volume and excellent cycle characteristics can be obtained.
As a method of reducing the current collector damage and suppressing the deformation of the current collector, the amount of gas introduced from the cylinder 11 to the aerosol generator 13 is reduced in the manufacturing apparatus of FIG. A method of reducing the amount of active material particles injected from the nozzle 15 to the substrate 16 can be considered, but it takes a longer time to form the active material layer than in the case of intermittent injection of the aerosol of the present invention. Cost.

Examples of film formation conditions when a positive electrode is made using a metal foil having a thickness of about 20 μm for the positive electrode current collector and a lithium-containing composite oxide powder having an average particle diameter of about 10 μm for the positive electrode active material include: The internal pressure of the film forming chamber 14 is 5 to 5000 Pa, the valve 19 is open for 0.5 to 5 seconds, and the valve 19 is closed for 0.5 to 60 seconds.
In the above, for example, there is a method in which the valve open time and the valve closed time are made constant, and the valve opening and closing are alternately repeated for a fixed time. At this time, the time of the open state and the time of the closed state may be the same, and the time of the open state may be longer or shorter than the time of the closed state.
In addition, if an active material layer having a certain thickness is formed on the current collector, the active material particles do not directly collide with the current collector, and damage to the current collector due to the collision of the active material particles is reduced. As the active material layer is formed, that is, as the film formation time elapses, the frequency of spraying the aerosol onto the current collector may be increased. For example, as the film formation time elapses, the valve open state time may be increased at a constant rate and the valve closed state time may be decreased at a constant rate. Also, for example, the valve opening and closing time is constant until a predetermined time elapses from the start of film formation. May be. In this case, the deposition efficiency can be improved and the deposition time can be shortened.

The active material particles in the aerosol may be primary particles (for example, a particle size of 0.1 to 10 μm) or secondary particles (for example, a particle size of 1 to 50 μm) in which the primary particles are aggregated.
The porosity of the active material layer formed by the above method is, for example, 60 to 10%.
Moreover, the thickness of the active material layer formed by the above method is, for example, 1 to 100 μm.
As the gas used for generating the aerosol, for example, an inert gas such as argon or helium, oxygen gas, nitrogen gas, carbon dioxide gas, dry air, or a mixed gas thereof is used. A reducing gas such as hydrogen gas may be used depending on the material of the active material.

As the positive electrode active material, a known lithium-containing composite oxide capable of inserting and releasing lithium ions is used. As a lithium containing complex oxide, what added aluminum to lithium cobaltate, lithium nickelate, lithium manganate, or these compounds is used, for example. Moreover, these may be used independently and may be used in combination of 2 or more type.
As a board | substrate used as a positive electrode electrical power collector, aluminum foil is mentioned, for example. The thickness of the substrate may be appropriately changed according to the volume capacity density of the non-aqueous electrolyte secondary battery and the thickness of the active material layer to be obtained, but an aluminum foil in the range of 5 to 20 μm that is generally commercially available may be used. If the thickness of the aluminum foil is less than 5 μm, the strength of the foil is so weak that problems such as breakage occur during film formation, and work efficiency is reduced. Moreover, since the volume capacity density of a nonaqueous electrolyte secondary battery will fall when the thickness of aluminum foil exceeds 20 micrometers, the predominance of using the manufacturing method of this invention will fade.

The negative electrode active material is not particularly limited as long as it can electrochemically react with lithium. Since the reactivity with lithium is relatively high and a high capacity is obtained, the negative electrode active material is composed of silicon alone, a silicon alloy, a compound containing silicon and oxygen, a compound containing silicon and nitrogen, a tin simple substance, a tin alloy, It is preferably at least one selected from the group consisting of a compound containing tin and oxygen and a compound containing tin and nitrogen.
Examples of the silicon alloy include SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi ₂ , NbSi. ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , or SiC.
Examples of the compound containing silicon and oxygen include Si ₂ N ₂ O, SiOx (0 <x ≦ 2), SnSiO ₃ , and LiSiO.
Examples of the compound containing silicon and nitrogen include Si ₃ N ₄ and Si ₂ N ₂ O.
An example of the tin alloy is Mg ₂ Sn.
Examples of the compound containing tin and oxygen include SnOx (0 <x ≦ 2) and SnSiO ₃ .
Examples of the compound containing tin and nitrogen include Sn ₃ N ₄ and Sn ₂ N ₂ O.
An example of the carbon material is graphite.
As a board | substrate used as a negative electrode collector, copper foil and nickel foil with a thickness of 5-50 micrometers are mentioned, for example.

The present invention also relates to a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein at least one of the positive electrode and the negative electrode has the electrode for a non-aqueous electrolyte secondary battery of the present invention described above. It is characterized by the use of electrodes obtained by the manufacturing method. For example, a separator made of a microporous film is placed between the positive and negative electrodes.
The nonaqueous electrolyte is not particularly limited as long as it can be generally used in a nonaqueous electrolyte secondary battery. The nonaqueous electrolyte includes, for example, a nonaqueous solvent and a supporting salt that dissolves in the nonaqueous solvent. As the non-aqueous solvent, for example, a cyclic carbonate such as ethylene carbonate or propylene carbonate is used. For example, lithium hexafluorophosphate is used as the supporting salt.

Examples of the present invention will be described in detail below, but the present invention is not limited to these examples. Example 1
Using the same apparatus as in FIG. 1, an electrode was produced by the following method.
The film forming chamber 14 used was a modified commercial vapor deposition apparatus (VPC-400, manufactured by ULVAC). As the aerosol generator 13, a commercially available 1-liter pressure-feed bottle (manufactured by KSK, RBN-S) installed in an ultrasonic cleaner (manufactured by Shimadzu Corporation, SUS-103) was used. The transmission frequency of the ultrasonic cleaner was set to 45 kHz so that the aerosol concentration, that is, the scattering amount of the active material particles in argon increased. Note that a vibrator or an ultrasonic homogenizer may be used instead of the ultrasonic cleaner.

  Next, a pipe 12b having an inner diameter of 1 mm was drawn into the film forming chamber 14 from the aerosol generator 13, and the tip of the pipe 12b was used as an injection nozzle 15. An aluminum foil having a thickness of 15 μm was installed as the substrate 16 at a position 5 mm away from the spray nozzle 15. On the other hand, the pressure-feed bottle and the argon cylinder 11 were connected by a pipe 12a having an inner diameter of 3 mm, and a compressed air valve 19 was provided therebetween.

Using the above apparatus, an electrode was produced as follows.
First, 20 g of lithium cobalt oxide having an average particle diameter of 10 μm (manufactured by Nippon Chemical Industry Co., Ltd.) was charged into the aerosol generator 13. Next, the valve 19 was closed and the exhaust pump 18 evacuated the film formation chamber 14 to the aerosol generator 13. Then, argon gas was sent into the aerosol generator 13 to generate an aerosol in which active material particles were dispersed in the argon gas, and the aerosol was sprayed from the spray nozzle 15 toward the substrate 16 through the pipe 12b. At this time, the flow rate of the argon gas is set to 2 liters / minute, and the compressed air valve 19 is opened by a computer so that the compressed air valve 19 is open for 1 second in 2 seconds and closed for the remaining 1 second. The aerosol was intermittently injected by controlling the open / close state. The film formation time is 10 minutes (5 minutes: jetting, 5 minutes: pause), and the degree of vacuum in the film formation chamber 14 at the time of forming the active material layer is about 500 Pa when the compressed air valve 19 is closed. When the valve 19 is open, the pressure is about 5000 Pa. Here, in order to obtain an electrode in a short time, the substrate holder 17 was not moved but sprayed to one place to form an active material layer, and an electrode having a small area was produced.

<< Comparative Example 1 >>
At the time of electrode preparation, the pneumatic valve 19 is removed, the flow rate of argon gas is adjusted so that the atmospheric pressure in the film forming chamber 14 is about 500 Pa, and the atmospheric pressure in the aerosol generator 13 is about 10000 Pa. It sprayed continuously for 5 minutes toward the board | substrate. Except for this, an electrode was produced in the same manner as in Example 1.

As a result of measuring the thickness of the active material layer using the micrometer for the electrode of Example 1 and the electrode of Comparative Example 1, the thickness of the active material layer of each electrode was 15 μm.
As a result of visually observing the electrodes of Example 1 and Comparative Example 1 obtained above, in the electrode of Comparative Example 1, wrinkles and through holes were found in the current collector. On the other hand, in the electrode of Example 1, no wrinkles or through holes were found in the current collector.

  The electrode of the present invention is suitably used for a non-aqueous electrolyte secondary battery such as a lithium ion battery, a nickel cadmium battery, or a nickel metal hydride battery. The nonaqueous electrolyte secondary battery of the present invention is suitably used as a power source for electronic devices such as portable devices and information devices.

It is a block diagram which shows an example of the manufacturing apparatus used for the manufacturing method of the electrode for nonaqueous electrolyte secondary batteries of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Gas cylinder 12a, 12b Piping 13 Aerosol generator 14 Deposition chamber 15 Nozzle 16 Substrate 17 Substrate holder 18 Exhaust pump 19 Valve 20 Active material powder

Claims (6)

A step of dispersing active material particles in a gas to obtain an aerosol;
A method for producing an electrode for a non-aqueous electrolyte secondary battery, the method including intermittently colliding the aerosol with a current collector to form an active material layer on the current collector.   2. The nonaqueous electrolyte secondary according to claim 1, wherein the gas is at least one selected from the group consisting of an inert gas, oxygen gas, nitrogen gas, hydrogen gas, carbon dioxide gas, and dry air. Manufacturing method of battery electrode.   The active material particle is a lithium-containing composite oxide, or a silicon simple substance, a silicon alloy, a compound containing silicon and oxygen, a compound containing silicon and nitrogen, a simple substance of tin, a tin alloy, a compound containing tin and oxygen, tin The method for producing an electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein the electrode is at least one selected from the group consisting of a compound containing carbon and nitrogen, and a carbon material.   The method for producing an electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein the current collector is an aluminum foil, a copper foil, or a nickel foil.   The electrode for nonaqueous electrolyte secondary batteries obtained by the manufacturing method in any one of Claims 1-4.   A nonaqueous electrolyte secondary battery comprising the electrode according to claim 5.

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