JP2008184647A - Composite structure manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce variance of deposition of raw particles on a substrate in a composite structure manufacturing method for manufacturing a composite structure comprising the substrate and a brittle material-formed structure by spraying aerosol containing particles of a brittle material to the substrate to deposit the brittle material-formed structure on the substrate. <P>SOLUTION: In the composite structure manufacturing method, the brittle material-formed structure is manufactured under a condition to satisfy inequality 1 : P1>P2>P3, where P1 denotes a pressure in a space constituted of a nozzle, a substrate and a suction member, P2 denotes a pressure at the connection opening part of a structure forming chamber to a second exhaust mechanism, and P3 denotes the pressure of a connection opening part of the suction member to a first exhaust mechanism. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a composite structure in which an aerosol containing fine particles of brittle material is sprayed on a substrate to form a brittle material structure on the substrate to produce a composite structure composed of the substrate and the brittle material structure. In particular, the present invention relates to a method for producing an electrode for a lithium secondary battery using the production method.

  In recent years, with the development of electronic devices such as portable devices, there is an increasing need for high functionality and miniaturization of electronic devices. A further increase in capacity is also demanded for lithium secondary batteries used as power sources for electronic devices.

  A conventional method for producing an electrode of a lithium secondary battery is generally produced by dispersing a positive electrode active material or a negative electrode active material in a solvent together with a binder and a conductive agent to form a slurry, and applying the slurry to a current collector. It was the target. Of the electrode components containing the active material, the smaller the binder and the conductive agent, the larger the battery capacity per unit volume and the higher the capacity of the battery can be obtained. An electrode having no binder at all (binder-free) could not be produced from the viewpoint of providing bonding force between particles and between a particle and a current collector.

  However, a method for producing a binder-free electrode or the like by a cold spray method or an aerosol deposition method has been proposed (see, for example, Patent Documents 1 to 3).

  In Patent Document 1, a negative electrode is produced by a cold spray method using silicon as a negative electrode active material. In the above-mentioned Patent Document 1, by using plastic deformation of a current collector metal caused by particle collision, an anchor effect is provided between the particles and the current collector, so that the particles are directly bonded to the current collector surface. Yes.

  In Patent Document 2, in addition to directly forming a polycrystalline structure of a brittle material on a substrate by an aerosol deposition method, aerosolized ultrafine particles such as ceramics having a particle size of 10 nm to 5 μm are faster than a nozzle. The structure to be produced is strengthened by irradiating the ultrafine particles and the substrate with a high-speed high-energy beam such as ion, atom, molecular beam, and low-temperature plasma before being injected as an ultrafine particle flow and colliding with the substrate. The device to be disclosed is disclosed.

In Patent Document 3, a nozzle that injects aerosol toward a substrate at high speed, a suction member that is installed in the vicinity of the collision site between the aerosol and the substrate, and sucks in the aerosol regardless of formation of a structure after colliding with the substrate; A particulate collection container that captures and stores brittle material fine particles separated from the gas in the aerosol regardless of the formation of the structure, regardless of the formation of the structure, and a fine particle collection container that is coupled to the fine particle collection container and separated from the brittle material fine particles. By using a composite structure production device that has an exhaust device that discharges the discharged gas out of the structure formation chamber, the fine particles of brittle material are collected in the fine particle collection container without being dissipated into the structure formation chamber, and the collected fine particles are generated as an aerosol. A device that can be returned to the container and reused is disclosed.
JP-A-2005-310502 JP 2000-212766 A JP 2003-119573 A

  However, in Patent Document 3, fine particles in aerosol ejected from a nozzle, specifically, fine particles of submicron to several μm in which primary particles of the order of 10 nm to submicron gather, In a very narrow area, primary particles that are deflected under the influence of the air flow to the high vacuum side in the structure forming chamber extending 360 ° on the substrate from the nozzle tip, or crushed when colliding with the substrate, It may be deflected by colliding with fine particles or primary particles. Therefore, when a film-like brittle material structure is formed on a substrate, a region with extremely low adhesion strength is generated, and there is a variation in adhesion strength between the substrate and the film-like brittle material structure. Variation in film formation such as variation in weight occurs.

  Therefore, in the composite structure manufacturing apparatus using the aerosol deposition method, in principle, the flow and velocity of the aerosol are determined using the pressure difference in the space region in the aerosol generator, the structure formation chamber, the nozzle injection port, etc. Since the film is formed, the pressure in each space region, the exhaust speed, etc. are controlled, and the fine particles in the aerosol ejected from the nozzle in the very narrow region between the suction member and the substrate are transferred from the nozzle tip to the substrate. It is important to counteract the influence of the air flow to the high vacuum side in the structure forming chamber extending 360 °.

  The present invention aims to solve the above-mentioned conventional problems, and a method for producing a composite structure capable of reducing film formation variation in the aerosol deposition method, in particular, production of an electrode for a lithium secondary battery using the production method It aims to provide a method.

  In the composite structure manufacturing method of the present invention, at least one suction member is provided around at least one nozzle, the first exhaust mechanism connected to the suction member, and at least one provided in the structure forming chamber. A composite in which the structure forming chamber is kept in a low vacuum by a second exhaust mechanism, and an aerosol in which fine particles of brittle material are dispersed in a gas is jetted from the nozzle to collide with the substrate to produce a brittle material structure. In the structure manufacturing method, the pressure of the space formed by the nozzle, the substrate, and the suction member is P1, and the pressure of the connection opening between the structure forming chamber and the second exhaust mechanism is P2. A structure of a brittle material is produced under a condition satisfying (Equation 1), where P3 is a pressure of a connection opening between the suction member and the first exhaust mechanism.

(Expression 1) P1>P2> P3
Further, at least one suction member is provided around at least one of the nozzles, and the first exhaust mechanism connected to the suction member and the at least one second exhaust mechanism provided in the structure forming chamber The structure forming chamber is kept at a low vacuum, and the exhaust speed per unit space volume of the space region surrounded by the tip of the nozzle and the opening of the suction member is set as the structure forming chamber and the second exhaust. A structure of a brittle material is produced in a state where the exhaust velocity per unit space volume of the space region in the connection opening with the mechanism is larger.

  The brittle material fine particles are lithium-containing transition metal oxides.

  According to the composite structure manufacturing method of the present invention, airflow or conductance in a very narrow region between the suction member in the structure forming chamber and the substrate is caused to flow from the connection opening between the structure forming chamber and the second exhaust mechanism. Since it can be generated in the direction of the connection opening between the suction member and the first exhaust mechanism, that is, in the direction opposite to that of the conventional case, the fine particles in the aerosol ejected from the nozzle are applied to the substrate from the nozzle tip. The airflow to the high vacuum side in the structure forming chamber extending 360 ° can be canceled out.

  In addition, since the suction rate of the unit space volume at the opening of the suction member is maximized, the amount of sucked particles is increased, so that the utilization efficiency of the raw material particles is increased and the aerosol fine particle concentration is stably generated over the long term. be able to.

  Accordingly, when the film-like brittle material structure is formed on the substrate, it is possible to reduce the region where the adhesion strength is extremely low, the adhesion strength variation between the substrate and the film-like brittle material structure, and the film-like brittleness. It is possible to reduce film formation variation such as weight variation of the material structure, and a favorable structure can be formed. As a result, it is possible to obtain a binder-free electrode with reduced film formation variation and a binder-free electrode for a lithium secondary battery.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following contents.

(Embodiment 1)
FIG. 1 shows a composite structure manufacturing apparatus 100 according to Embodiment 1 of the present invention. As shown in FIG. 1, the aerosol generator 3 is connected to an argon gas cylinder 1 through a gas transport pipe 2. The aerosol generator 3 is connected to a nozzle 6 installed in the structure forming chamber 5 via an aerosol transport pipe 4. A substrate 7 fixed to the substrate holder 8 is disposed at a position facing the tip of the nozzle 6. A suction cylinder 9 as a suction member is installed around the nozzle 6 so as to open to the substrate 7 side.

The internal dimensions of the structure forming chamber 5 are 250 × 250 × 150 mm, and the space volume excluding the substrate holder 8 and the suction cylinder 9 is about 7.5 liters. The suction cylinder 9 is hollow, and the inner diameter of the opening is 10 mm. The space volume provided by the suction cylinder 9 and the nozzle 6 is about 10 cm ³ .

  The distance from the tip of the nozzle 6 to the surface of the substrate 7 is 5 mm. The suction cylinder 9 is located 3 mm away from the surface of the substrate 7, that is, the nozzle 6 is disposed 2 mm inside the opening of the suction cylinder 9.

  In Embodiment 1 of the present invention, a nozzle 6 having a straight shape, an inner diameter of 4 mm, and an outer diameter of 6.25 mm was used so that the effect of the present invention becomes clearer.

  Further, as the substrate holder 8, an XY stage is usually used to form a film-like brittle material structure on the substrate 7 by collision of fine particles while changing the aerosol collision position by swinging the substrate 7. However, in the first embodiment of the present invention, the substrate holder 8 is fixed in order to make the film formation variation clearer and easier to understand.

  As the first exhaust mechanism, the first vacuum pump 11 is connected to the suction cylinder 9 through the first suction pipe 12 and the first particulate collection container 10 and further through the structure forming chamber 5. ing. The first suction pipe 12 is provided with a first adjustment valve 30.

  As a second exhaust mechanism, a second vacuum pump 14 is connected to the structure forming chamber 5 via a second suction pipe 15 and a second particulate collection container 13. The second suction pipe 15 is provided with a second adjustment valve 31.

  The inner diameter of the connection opening between the structure forming chamber 5 and the second suction pipe 15 is 50 mm.

  The exhaust amount and pressure in the first and second exhaust mechanisms are adjusted by changing the opening ratios of the first adjustment valve 30 and the second adjustment valve 31.

  In the first embodiment of the present invention, the first vacuum pump 11 and the second vacuum pump 14 have a maximum exhaust capacity of 135 liters / minute.

  In Embodiment 1 of the present invention, the entire internal pressure of the structure forming chamber 5 is lowered to a certain level by the second exhaust mechanism, but the present invention is not limited to this, and the second exhaust mechanism The structure forming chamber 5 may be decompressed by the first exhaust mechanism without using the mechanism.

  The aerosol generator 3 is filled with brittle material fine particles, for example, fine particle powder of a lithium-containing transition metal oxide. In Embodiment 1 of the present invention, lithium nickel cobaltate was used as the lithium-containing transition metal oxide.

  Here, the brittle material refers to a fracture mode of brittle fracture among inorganic materials and some alloy materials. Non-metallic elements such as semiconductors with high covalent bonding, ceramics, intermetallic compounds, etc. included.

  As the lithium-containing transition metal oxide for the positive electrode, lithium-containing transition metal oxides such as lithium nickelate and lithium cobaltate, and solid solutions thereof are used. In particular, a lithium-containing transition metal oxide containing nickel as a main component is preferable because it tends to be in the form of secondary particles. The lithium nickelate and lithium cobaltate composite oxides are represented by the general formula (Formula 1).

(Chemical formula 1) Li _x M _(1-y) L _y O ₂
The element M is at least one selected from the group consisting of Ni and Co. The element L is at least one selected from the group consisting of alkaline earth metal elements, transition elements other than Ni and Co, rare earth elements, IIIb group elements, and IVb group elements.

  The element L preferably contains at least one selected from the group consisting of Al, Mn, Ti, Mg, Zr, Nb, Mo, W, and Y. These elements may be contained independently and 2 or more types may be contained. Furthermore, it is desirable that the element L is a transition element such as Mn. The preparation method can be synthesized by firing an oxide or hydroxide having a predetermined metal element ratio in an oxidizing atmosphere.

  It is desirable that x and y in the general formula (Formula 1) satisfy 0.85 ≦ x ≦ 1.25 and 0 ≦ y ≦ 0.50. In particular, the range of x representing the lithium content increases or decreases depending on the charge / discharge of the battery, but 0.85 ≦ x ≦ 1 in the fully discharged state, the initial state immediately after the battery assembly, or immediately after the synthesis of the lithium composite oxide. .35, and 1.02 ≦ x ≦ 1.25 is more preferable.

  Further, as the brittle material for the negative electrode, silicon, tin alloy, or the like can be used.

  When the substrate 7 is used as a positive electrode current collector, a foil or sheet made of aluminum, stainless steel, nickel, titanium, carbon, conductive resin, or the like can be used, and further, an aluminum foil, an aluminum alloy foil, or the like is used. It is preferable. The thickness of the positive electrode core material is not particularly limited, but is preferably in the range of 1 to 200 μm, for example.

  In Embodiment 1 of the present invention, argon is used as a carrier gas that is a component of a gas for transporting a brittle material, but a rare gas such as helium can also be used. The carrier gas not only transports brittle materials, but is also involved in the atmosphere during film formation, and the inert activity generated by the inert atmosphere is less likely to disappear, resulting in strong bonding. Becomes easier to obtain. Furthermore, the use of a light element gas such as helium makes it possible to increase the collision speed of particles, and a dense film having a high bonding force can be obtained.

  Hereinafter, the operation of the composite structure manufacturing apparatus 100 according to Embodiment 1 of the present invention will be described.

  The argon gas cylinder 1 is opened and the argon gas is fed into the aerosol generator 3 and at the same time, the aerosol generator 3 is operated to generate an aerosol in which brittle material fine particles and argon gas are mixed in an appropriate ratio. At the same time, the first vacuum pump 11 and the second vacuum pump 14 are operated to generate a differential pressure between the aerosol generator 3 and the structure forming chamber 5. The aerosol generated in the aerosol generator 3 is accelerated by the differential pressure and is sprayed from the nozzle 6 toward the substrate 7 through the aerosol transport pipe 4. As described above, in the first embodiment of the present invention, the substrate holder 8 is fixed in order to make the film formation variation clearer and easier to understand.

  At this time, many fine particles contained in the aerosol bounce off in four directions after colliding with the substrate 7 regardless of the formation of the structure. The amount of scattered fine particles in the structure forming chamber 5 can be suppressed by sucking the rebounding fine particles with the suction cylinder 9 provided in the vicinity of the collision position between the substrate 7 and the aerosol. The sucked aerosol particles are introduced into the first particle collection container 10 through the first suction pipe 12, and the argon gas and the brittle material particles are separated in the first particle collection container 10. Thereafter, the argon gas is sucked into the first vacuum pump 11, and the brittle material particles are accumulated in the first particle collection container 10.

  Next, the pressure relationship in the composite structure manufacturing apparatus 100 according to Embodiment 1 of the present invention will be described.

  In the structure forming chamber 5, the pressure in the vicinity of the nozzle 6 from which the aerosol is injected, that is, the space formed by the nozzle 6, the substrate 7, and the suction cylinder 9 is P1. Let P2 be the pressure at the connection opening between the structure forming chamber 5 and the second suction pipe 15. The pressure at the connection opening between the suction cylinder 9 and the first suction pipe 12 is P3. P1 is the highest among the pressures in P1 to P3, and the aerosol deflects when a pressure difference occurs. Therefore, in either case of (Equation 1) or (Equation 2), it is not possible to introduce the fine particles scattered in the suction cylinder 9 Is possible.

(Expression 1) P1>P2> P3
(Expression 2) P1> P3 ≧ P2
In particular, in the aerosol sprayed from the nozzle 6 toward the substrate 7, as will be described later, (Equation 1) is more effective in reducing the highly deflectable aerosol and increasing the straight traveling aerosol. It is.

  Further, the exhaust speed per unit space volume of the space area surrounded by the tip of the nozzle 6 and the opening of the suction cylinder 9 is set as the space area of the connection opening between the structure forming chamber 5 and the second suction pipe 15. By making it larger than the exhaust velocity per unit space volume in, it becomes possible to reduce the deflection of the aerosol and to reduce the film formation variation. Furthermore, it is possible to greatly reduce the amount of brittle material fine particles that dissipate in the structure forming chamber 5.

  As described above, the degree of vacuum in the structure forming chamber 5, the degree of vacuum around the substrate 7 and the nozzle 6, the pressure in the aerosol generator 3, and the pressure of the supplied carrier gas are determined by the machine of the structure to be formed. This is a major factor that affects the electrical characteristics and electrical characteristics. Therefore, according to the composite structure manufacturing apparatus 100 of Embodiment 1 of the present invention, the degree of vacuum and the pressure can be controlled, respectively, which can greatly contribute to the stability of the quality of the formed structure. .

  Hereinafter, specific examples of the present invention will be described. The pressure was measured using a Baratron vacuum gauge capable of measuring under a low vacuum of about 1 Pa from atmospheric pressure.

(Example 1)
In Example 1, a positive electrode plate for a lithium secondary battery was manufactured using the composite structure manufacturing apparatus 100 according to Embodiment 1 under the condition of (Equation 1).

  As the substrate 7, a rolled aluminum foil having a thickness of 15 μm was used, and as the brittle material, lithium nickel cobalt oxide was used.

  The aerosol is sprayed from the nozzle 6 toward the substrate 7 while adjusting the flow rate of the argon gas supplied from the argon gas cylinder 1 to 200 sccm, the pressure of the argon gas to 300 kPa, and the pressure in the aerosol generator 3 to 10 kPa. The film was formed at 30 ° C. for 10 seconds.

  During the film formation, the exhaust per unit space volume on the first exhaust mechanism side is increased so that the exhaust speed per unit space volume in the space region surrounded by the tip of the nozzle 6 and the opening of the suction cylinder 9 increases. The speed was made larger than the exhaust speed per unit space volume on the second exhaust mechanism side. Specifically, the exhaust speed per opening cross-sectional area of the suction cylinder 9 is changed by the first adjustment valve 30 and the second adjustment valve 31 to the connection opening between the structure forming chamber 5 and the second suction pipe 15. The film was formed by adjusting so as to be at least twice the exhaust speed per sectional area. When the pressures of P1 to P3 were measured with a Baratron vacuum gauge, P1 was 1000 Pa, P2 was 600 Pa, and P3 was 300 Pa.

(Comparative Example 1)
In this comparative example 1, using the composite structure manufacturing apparatus 100 of the first embodiment, under the condition of (Equation 2), the other conditions were the same as in example 1, and the positive electrode for a lithium secondary battery A plate was made.

  That is, in the first comparative example, unlike the first embodiment, the first regulating valve 30 and the second regulating valve 31 are used to set the exhaust speed per opening cross-sectional area of the suction cylinder 9 to the structure forming chamber 5. And the second suction pipe 15 were adjusted so as to be equal to or higher than the exhaust speed per cross-sectional area of the connection opening. When the pressures of P1 to P3 were measured with a Baratron vacuum gauge, P1 was 1000 Pa, P2 was 600 Pa, and P3 was 620 Pa.

  The effects of the present invention will be described below with reference to FIGS.

  2 shows the results of Example 1, and FIG. 3 shows the results of Comparative Example 1. (A) in FIG. 2 and FIG. 3 is a photograph showing the state of aerosol sprayed onto the aluminum foil 23. (B) in FIG. 2 and FIG. 3 is a diagram schematically showing the state of aerosol sprayed onto the aluminum foil 23 at the AA cross-section line of (a). (C) in FIG. 2 and FIG. 3 is an SEM photograph at point P in (a) above.

  As shown in FIG. 2 and FIG. 3A, the black part having a diameter of about 4 mm in the center of the photograph is the particle film forming part 20, and the part observed white around the particle film forming part 20 is the particle scattering part. 21. As shown in FIGS. 2 and 3 (a) and 3 (b), a particle film forming portion in which nickel cobalt lithium fine particles 22 are densely formed on the aluminum foil 23 due to the injection of the aerosol having high straightness. 20 is formed. Further, around the particle film forming unit 20, there is a particle scattering unit 21 to which the nickel cobalt oxide fine particles 22 are scattered and adhered because the aerosol is deflected.

  2A and 2B, it can be seen that the particle scattering portion 21 in Example 1 and Comparative Example 1 is smaller in Example 1. Further, from FIG. 2 and FIG. 3 (c), it can be seen that the number of scattered particles is smaller and smaller in Example 1.

  In this way, by setting the pressure to the condition of (Equation 1), it is possible to reduce the highly deflectable aerosol ejected from the nozzle 6 and increase the highly rectilinear aerosol to be ejected onto the substrate 7. it can.

  In addition, the exhaust speed per unit space volume of the space area surrounded by the tip of the nozzle 6 and the opening of the suction cylinder 9 is set as the space area in the connection opening between the structure forming chamber 5 and the second suction pipe 15. By making the exhaust velocity per unit space volume larger than this, the highly deflectable aerosol ejected from the nozzle 6 can be reduced, and the highly straight aerosol can be increased and ejected onto the substrate 7.

  Therefore, according to the method for producing a composite structure of the present invention, a binder-free electrode with reduced film formation variation and a binder-free electrode for a lithium secondary battery can be obtained.

  In addition, the composite structure manufacturing method of the present invention is effective for a composite structure manufacturing method that requires patterning, multiple nozzles, and the like.

  The method for producing a composite structure according to the present invention is to form an electrode plate of a composite structure in which brittle particles-substrate and brittle particles-brittle particles are firmly joined without containing a binder and film formation variation is reduced. In addition, since the utilization efficiency of the raw material particles can be increased, it is useful for a method for manufacturing a composite structure using an aerosol deposition method. Further, it is useful as a method for producing not only lithium secondary batteries but also devices in general using an electrochemical mechanism.

Schematic diagram showing a composite structure manufacturing apparatus according to Embodiment 1 of the present invention. (A) Optical micrograph showing film formation state in Example 1 (b) Schematic diagram of AA cross section line of (a) above (c) Scanning electron micrograph at point P of (a) above (A) Optical micrograph showing film formation state in Comparative Example 1 (b) Schematic diagram of AA cross-sectional line in (a) above (c) Scanning electron micrograph at point P in (a) above

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Argon gas cylinder 2 Gas transport pipe 3 Aerosol generator 4 Aerosol transport pipe 5 Structure formation chamber 6 Nozzle 7 Substrate 8 Substrate holder 9 Suction cylinder 10 First particulate collection container 11 First vacuum pump 12 First suction pipe 13 Second fine particle recovery container 14 Second vacuum pump 15 Second suction pipe 20 Particle film forming part 21 Particle scattering part 22 Nickel cobalt oxide lithium fine particle 23 Aluminum foil 30 First adjustment valve 31 Second adjustment valve 100 Composite Structure manufacturing equipment

Claims (3)

At least one suction member is provided around at least one nozzle, and the structure forming chamber includes a first exhaust mechanism connected to the suction member and at least one second exhaust mechanism provided in the structure forming chamber. In a method for producing a composite structure in which an aerosol in which fine particles of brittle material are dispersed in a gas is jetted from the nozzle to collide with a substrate, and a brittle material structure is produced.
The pressure of the space formed by the nozzle, the substrate, and the suction member is P1, the pressure of the connection opening between the structure forming chamber and the second exhaust mechanism is P2, and the suction member and the first member A method of manufacturing a composite structure, wherein a structure of a brittle material is manufactured under a condition satisfying (Equation 1) when a pressure of a connection opening with one exhaust mechanism is P3.
(Expression 1) P1>P2> P3 At least one suction member is provided around at least one of the nozzles, and the structure is constituted by a first exhaust mechanism connected to the suction member and at least one second exhaust mechanism provided in the structure forming chamber. The formation chamber is maintained at a low vacuum, and the exhaust speed per unit space volume of the space area surrounded by the tip of the nozzle and the opening of the suction member is determined by the structure formation chamber and the second exhaust mechanism. A structure of a brittle material is produced in a state where the exhaust velocity per unit space volume of the space region in the connection opening of
A method for manufacturing the composite structure according to claim 1. The brittle material fine particles are lithium-containing transition metal oxides,
A method for producing the composite material structure according to claim 1.