Method for immobilizing solid-phase particles

Abstract

To provide a new method for immobilizing solid phase particles different from a conventional method.SOLUTION: A method for fixing solid-phase particles on a surface of a substrate, the method comprising: preparing, as the substrate, a fixing substrate whose surface is at least partially covered with a layer of fine particles in advance; forming a three phase flow including a solid phase containing the solid-phase particles, a gas phase, and a liquid phase, and generating a shock wave in the three phase flow by accelerating the solid-phase particles; and causing the three phase flow to collide with the surface of the fixing substrate, the gas bubbles of the gas phase are contracted, expanded and exploded by the shock waves on the surface of the substrate for fixing, by which the solid-phase particles are fixed on the surface of the substrate by the kinetic energy of the solid-phase particles accompanying the explosion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for immobilizing solid-phase particles. [Background technology]

[0002] [Challenges with all-solid-state batteries] The performance of all-solid-state batteries lies in the thin film and density of the solid electrolyte, but the usual method is to finely align the particle diameter and compactly compress and laminate it. The cell structure is pressed under high pressure, and cracks caused by the attack are mitigated by sandwiching fibers or polymers between them, but a binder is used to directly and strongly adhere the polymers and fibers. The volume of the positive and negative electrode materials changes significantly during the reaction, which can cause battery degradation.

[0003] Furthermore, in recent years, because quantum dots are important for the efficiency of electrode materials, there is a demand for improving the conductivity and reactivity of all solids by closely bonding quantum dots. R2R by coating requires binders and solvents, and there are issues such as a decrease in electrical performance due to the binder, energy loss in the solvent evaporation process, and the need for large-scale drying equipment.

[0004] Patent Document 1 describes an all-solid-state battery having an all-solid-state battery laminate including one or more unit all-solid-state batteries each including a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer stacked in this order, and a resin layer covering the side surface of the all-solid-state battery laminate, the resin layer having a multilayer structure including a first resin layer and a second resin layer in this order from the side closer to the side surface of the all-solid-state battery laminate, and the elastic modulus of the first resin layer is smaller than the elastic modulus of the second resin layer.

[0005] The key design concepts behind the solid-state battery structure in Patent Document 1 are as follows: The all-solid-state battery is made up of stacked layers of "positive electrode," "solid electrolyte," and "negative electrode," and by densely stacking these, it is possible to generate a large amount of power in a compact space. By placing a soft resin that absorbs deformation around the battery, the "problem of cracks and poor contact due to shape changes" is resolved. By covering the outside with a hard resin, the shape of the entire battery unit is kept constant.

[0006] A generally known method for producing such a solid-state battery includes the following steps. (Step 1) The metal foil is fed by a roller and cut to an appropriate length. (Step 2) Apply ultraviolet (UV) curable resin to the cut metal foil. (Step 3) The UV-curable resin on the metal foil is irradiated with UV light to initiate the curing reaction of the resin. (Step 4) The metal foil and the layer of electrode active material are pressed together using a roller. The UV curing agent hardens, completing the adhesion and creating an electrode.

[0007] The above process can be used for both positive and negative electrodes, and is planned to be used particularly for manufacturing positive electrodes. Aiming to solve the issues specific to all-solid-state batteries, there is a need to develop materials that are useful as electrode active materials for all-solid-state batteries from various perspectives, such as high energy density (high potential, high capacity), reduced blocked pores, formability, elastic modulus, volume change, ionic conductivity, mechanical strength, and ease of compounding with solid electrolytes.

[0008] With regard to material processing, a wide range of issues remain, including solid-phase synthesis of solid electrolytes, liquid-phase synthesis of solid electrolytes, construction of electrode-electrolyte interfaces using solid electrolyte precursor solutions, technology for reducing the cathode-solid electrolyte interface resistance, reducing porosity (in the electrode layer), simplifying the pressing process, reducing confining pressure, analysis of electrode ionic and electronic conductivity and improving tortuosity, and suppressing lithium dendrites. Among these, construction of solid-solid interfaces, such as the electrode-electrolyte interface, is of particular importance because it significantly affects the performance of all-solid-state batteries. Electrode active material particles with an average particle size of submicron to approximately 10 μm are often used. It is preferable for the solid electrolyte used in the electrode layer to have a volume less than one-tenth of the electrode active material, i.e., a particle size less than one-half of the electrode active material.

[0009] When manufacturing batteries, pressing at high pressures of several hundred MPa or more is required. One of the issues with this process is the occurrence of cracks in the electrode active material particles. Large local stress occurs at the contact points between highly brittle positive electrode active material particles, causing cracks in the positive electrode active material particles.

[0010] The press rolls used in the process of manufacturing electrodes for lithium-ion batteries require extremely high mechanical precision.

[0011] The process for manufacturing electrodes for lithium-ion batteries can be broadly divided into three steps. First, the electrode materials are applied. Next, there is a press part to thin the applied electrode material to a uniform thickness and increase its density. This is where press rolls are used. Poor mechanical precision of the press rolls directly leads to variations in the thickness of the electrode material. Variations in the electrode material can lead to quality issues, such as variations in battery performance and uneven battery thickness that prevent the battery from fitting into the case. Lithium-ion batteries are made by stacking multiple layers of electrode material, and even variations of just a few microns within a single electrode can result in significant thickness variations when stacked. For this reason, press rolls must have extremely high mechanical precision of less than a few microns. All-solid-state batteries achieve their intended performance with electrodes made by pressing active material (ceramic powder) under high pressure (over 100 MPa). However, when molding ceramic powder, springback can occur depending on the type and characteristics of the active material, which can lead to electrode cracks.

[0012] Next, a conventional method for forming a particle layer that is being considered for use in producing an electrode will be described.

[0013] [Fine particle shot peening method] (referred to as "Prior Art 1") The fine particle shot peening method forms a nanocrystalline grain layer on the surface of the treated material, and is widely known in the industry as a method for increasing fatigue strength through this layer (Non-patent Document 1, Non-patent Document 2).

[0014] This fine particle shot peening is a surface modification technology in which particles of 10 to 100 μm are mixed into a gas and collided at high speed with the surface of a substrate, and by introducing strong processing into the localized area of ​​the outermost surface, a microcrystalline layer, a nanocrystalline layer, and compressive residual stress are added, improving the fatigue strength and sliding function of machine parts, molds, etc. The target is the surface of metal or polymer material, and it is a blasting technology that uses particle collisions.

[0015] [Jet stream impingement mill method] (referred to as "Prior Art 2") Non-Patent Document 3 describes the jet impingement mill method. In this method, a high-speed solid-gas mixed flow with dispersed particles is supplied to a nozzle. A strong swirling flow field is formed inside the vessel, and particle pulverization occurs when particles accelerated by the high-speed jet in a ring-shaped region outside the vessel collide with each other and with the flow channel wall. The velocity at the nozzle can be made supersonic by using a Laval nozzle, making it possible to impart greater pulverization energy to the particles. This is a blasting technology in which supersonic flowing particles are used to remove and clean deposits and solids adhering to surfaces.

[0016] [Multiple spray nozzle injection method] (referred to as "Prior Art 3") Patent Document 2 (Title of Invention: Fluid Spraying Method and Fluid Film Forming Method) describes a fluid spraying method or a film forming method comprising the steps of arranging multiple spray nozzles in a single row, approximately a single row, multiple rows, or in a circle, and staggering the spray timing so that the spray streams from adjacent spray nozzles do not interfere with each other in the air or on the target. This method can also be applied to jet streams, and is a technology that can form films by layering fine particles. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] Japanese Patent Application Publication No. 2019-153535 [Patent Document 2] Japanese Patent Application Publication No. 2018-089543 [Non-patent literature]

[0018] [Non-Patent Document 1] Toshiyuki Sawada, Journal of the Japan Institute of Metals, Vol. 78, No. 6 (2014) 211-217 Effect of shot hardness on surface modification behavior of vacuum carburized material by fine particle shot peening [Non-patent document 2] Hideo Mano, Satoru Kondo, Toru Imura, Akihito Matsumuro, Journal of the Japan Institute of Metals, Vol. 69, No. 2 (2005) 213-216 Effect of nanocrystalline phase formed by shot peening on fatigue strength [Non-patent document 3] Toshihiko Kawachi, Turbomachinery Vol. 24 No. 11 (1996) 661-666 Jet milling and classification of powders Summary of the Invention [Problem to be solved by the invention]

[0019] As described above, various methods have been used to form layers using fine particles. However, coating methods in particular have had problems such as energy loss and the need for large-scale drying equipment.

[0020] An object of the present invention is to provide a novel method for immobilizing solid-phase particles that is different from conventional methods. [Means for solving the problem]

[0021] In order to achieve the above-mentioned object, the present invention provides a method for fixing solid particles on the surface of a substrate, comprising the steps of: preparing a fixing substrate as the substrate, at least a portion of whose surface is covered in advance with a layer of fine particles; forming a three-phase multiphase flow consisting of a solid phase containing the solid particles, a gas phase, and a liquid phase, and applying acceleration to the solid particles to generate shock waves in the three-phase multiphase flow; and causing the three-phase multiphase flow to collide with the surface of the fixing substrate, wherein the shock waves cause gas bubbles in the gas phase to contract, expand, and explode on the surface of the fixing substrate, thereby fixing the solid particles on the surface of the substrate by the kinetic energy of the solid particles associated with the explosion.

[0022] Such a method for fixing solid phase particles is a novel method for fixing solid phase particles, and has advantages such as being simple and easy and not requiring compression bonding under high pressure.

[0023] In this case, the liquid phase preferably consists of water.

[0024] In this way, by using water as the liquid phase, the method can be made inexpensive and simple.

[0025] Furthermore, in this case, it is preferable that the formation of the three-phase multiphase flow and the generation of the shock waves are carried out by accelerating the dispersion of the solid particles in the water to a speed equal to or faster than the speed of sound in water using a pulse jet water flow generator and firing it in a pulse, and injecting the accelerated dispersion of the water into a water flow having a speed lower than that of the accelerated dispersion of the water, thereby applying acceleration to the solid particles and moving the solid particles at a speed equal to or faster than the speed of sound in water, and by mixing gas microbubbles into the dispersion of the water, thereby forming the three-phase multiphase flow.

[0026] Furthermore, in this case, in forming the three-phase multiphase flow, it is preferable that the dispersed water in the pulse jet water flow generator is passed through an orifice and gas is jet-injected into the orifice from inside or outside the dispersed water to mix the gas microbubbles into the dispersed water.

[0027] More specifically, such a configuration can form a three-phase multiphase flow to generate a shock wave. [Effects of the Invention]

[0028] The present invention provides a novel method for fixing solid-phase particles, which is simple and has advantages such as a simplified drying step and no need for high-pressure compression. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic diagram showing an example of an apparatus for carrying out the method for immobilizing solid-phase particles of the present invention. [Figure 2] This is a numerical analysis diagram showing the time evolution of bubble shape and isobars when a shock wave in water collides with a cylindrical air bubble. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention will be described in detail below, but the present invention is not limited thereto.

[0031] The present invention provides a method for fixing solid particles on a surface of a substrate, comprising the steps of: preparing a fixing substrate as the substrate, at least a portion of whose surface is covered in advance with a layer of fine particles; forming a three-phase multiphase flow consisting of a solid phase containing the solid particles, a gas phase, and a liquid phase, and applying acceleration to the solid particles to generate shock waves in the three-phase multiphase flow; and causing the three-phase multiphase flow to collide with the surface of the fixing substrate, wherein the shock waves cause gas bubbles in the gas phase to contract, expand, and explode on the surface of the fixing substrate, thereby fixing the solid particles on the surface of the substrate by the kinetic energy of the solid particles resulting from the explosion.

[0032] The present invention will be described with reference to the drawings, in which: Figure 1 is a schematic diagram showing an example of an apparatus for carrying out the method for immobilizing solid-phase particles of the present invention.

[0033] The three-phase multiphase flow generator 100 of FIG. 1 includes a gas phase passage 20 and a mixed phase passage 30 for solid particles and a liquid phase, which is arranged to surround the gas phase passage 20. The mixed phase passage 30 has an orifice 32 formed therein. The tip of the gas phase passage 20 can be located near the orifice 32. A gas phase 27 exists inside the gas phase passage 20, and a jet stream is introduced into the gas phase 27 as a gas phase flow 25. Although the gas phase passage 20 is arranged inside the mixed phase passage 30 in FIG. 1, the gas phase passage 20 may also be arranged outside the mixed phase passage 30 so as to surround it. The mixed phase passage 30 is for passing a mixed phase 37 of particles and a liquid phase, and a mixed phase flow 35 of particles and a liquid phase is introduced as a jet liquid phase flow. In this way, a three-phase mixed phase 47 is formed, and a flow of a three-phase mixed layer (three-phase multiphase flow) 45 is ejected from the three-phase multiphase flow generating device 100.

[0034] A substrate 51 is placed at the destination of the three-phase multiphase flow 47 ejected from the three-phase multiphase flow generating device 100. At least a portion of the surface of this substrate 51 is pre-coated with a layer 53 made of fine particles. The solid particles contained in the three-phase multiphase flow 47 ejected from the three-phase multiphase flow generating device 100 are fixed on the substrate 51, becoming fixed solid particles 55.

[0035] The method for immobilizing solid particles of the present invention will be described below, which is carried out using the three-phase multiphase flow generating apparatus 100 shown in Figure 1. The present invention is a method for immobilizing solid particles 55 on the surface of a substrate 51.

[0036] First, a fixing substrate is prepared as the substrate 51, at least a portion of whose surface is covered in advance with a layer 53 made of fine particles. Here, the layer 53 made of fine particles may consist of a single layer of fine particles, and can be made extremely thin. There are no particular limitations on the method for forming this layer 53 made of fine particles, and a conventional coating method or the like may be used. Since the layer 53 made of fine particles required for the method for fixing solid-phase particles of the present invention can be thin, pressure bonding is not required. Furthermore, there are no particular limitations on the material of the substrate 51, and various metals and other substrate materials can be used.

[0037] Next, a three-phase multiphase flow consisting of a solid phase containing solid particles, a gas phase, and a liquid phase is formed. At the same time, the solid particles are accelerated to generate shock waves in the three-phase multiphase flow. This step can be performed by forming a three-phase mixed layer flow (three-phase multiphase flow) 45 using the three-phase multiphase flow generator 100 shown in FIG. 1. By converting the gas phase flow 25 into a jet stream and the particle-liquid mixed phase flow 35 into a jet liquid phase flow, acceleration can be applied to the solid particles, which allows the solid particles to exceed the sonic speed of the liquid that constitutes the liquid phase, generating shock waves in the three-phase multiphase flow.

[0038] The solid phase particles can range in size from nanoparticles or quantum dot-sized particles to particles of several μm, up to about 10 μm.

[0039] In this step, the liquid phase is preferably water. By using water as the liquid constituting the liquid phase, an inexpensive and simple method can be achieved. Although an organic solvent such as alcohol can also be used as the liquid constituting the liquid phase, the use of water is most preferred.

[0040] In this step, the formation of a three-phase multiphase flow and the generation of shock waves are preferably performed as follows. First, water is used as the liquid to prepare dispersed water containing solid particles. A mixed-phase flow (jet water flow) of particles and liquid (water) passing through the mixed-phase passage 30 is generated by accelerating the dispersed water to a speed greater than the speed of sound in water using a pulse jet water flow generator and ejecting it in pulses. The accelerated dispersed water is injected into a water flow slower than the accelerated dispersed water, thereby accelerating the solid particles. This causes the solid particles to move at a speed greater than the speed of sound in water. By mixing gas microbubbles into this dispersed water through the gas-phase passage 20, a three-phase multiphase flow 47 can be formed.

[0041] In this case, in the step of forming a three-phase multiphase flow, the dispersed water in the pulse jet water flow generator is passed through the orifice 32 in FIG. 1, and gas is jet-injected into the orifice 32 from inside or outside the dispersed water, thereby mixing gas microbubbles into the dispersed water.

[0042] Next, the three-phase flow 47 is caused to collide with the surface of the fixing substrate, which is made up of the substrate 51 and the layer 53 of fine particles. In this way, the shock waves cause the gas bubbles in the gas phase to contract, expand, and explode on the surface of the fixing substrate, and the kinetic energy of the solid particles caused by the explosion allows the solid particles to be fixed on the surface of the substrate 51.

[0043] The method for fixing solid-phase particles of the present invention can be called a "new thin-film formation method." Unlike the "microparticle shot peening method" (Prior Art 1), the present invention is characterized in that the substrate surface subjected to impact is a layer of an inorganic or composite material formed of microparticles of 0.1 to 100 μm in size (a layer containing mesoscopic quantum dot aggregates, hereinafter referred to as the "microparticle grain layer"). The microparticles to be impacted can be smaller than the largest or smallest (0.1 μm) of the microparticles forming the substrate surface. That is, typically, nanoparticles or quantum dot-sized microparticles (hereinafter referred to as "quantum dot particles") can be impacted onto the microparticle layer. Another major difference between Prior Art 1 (microparticle shot peening method) and Prior Art 2 (jet stream collision mill method) is that quantum dot particles recoil upon impact and are embedded inside the microparticles in the microparticle layer, and furthermore, the quantum dot particles aggregate with each other on the surface to form a new layer (hereinafter referred to as the "quantum dot layer") composed of quantum dot particles.

[0044] Furthermore, prior art 3 (multiple spray nozzle injection method) is a film formation technology that can use jet flows and is designed to prevent the spray flows from the multiple spray nozzles from interfering with each other in the air or on the substrate surface. In contrast, while the present invention is also a film formation technology that uses jet flows, in principle, it is different from prior art 3 in that it only requires the formation of a three-phase multiphase flow of gas, liquid, and solid phases.

[0045] As described above, the present invention is completely novel compared to conventional fine particle shot peening techniques, jet stream collision milling, and multiple spray nozzle injection techniques. Furthermore, it has a novelty (1) that differs from general conventional techniques that simply spray fine particles onto a substrate surface and allow them to adhere or solidify by drying or sintering, or form a fine particle layer by printing techniques using ink containing fine particle pigments. Furthermore, there has been no report to date of a technology that can simultaneously recoil quantum dot particles and embed them inside the particle layer, and there is no industrial technology that can achieve this, making this technology novel (2).

[0046] Furthermore, the present invention is capable of colliding quantum dot particles, and the technical concept of adding sufficient momentum to embed a quantum dot particle into a layer of particles in a three-phase flow of gas, liquid, and solid phases, relative to the minute weight of the quantum dot particle, has never existed before. Therefore, the present invention utilizes this new technical concept, and in this respect has novelty (3) as a new principle (new principle patentability).

[0047] Furthermore, the present invention utilizes the principle of generating shock waves in water, whereas in conventional jet flow film formation technology, the shock waves used are generated in gas (air, nitrogen, argon, helium), and has a novelty (4) that is fundamentally different from that of the present invention.

[0048] While prior art 3 (multiple spray nozzle injection method) requires that each spray stream not interfere with each other in the air or on the target object, this invention does not require this. In principle, it is sufficient to form a three-phase multiphase flow of gas, liquid, and solid phases, and is a technology that does not depend on the method or process for forming the three-phase multiphase flow (novelty (5)).

[0049] Furthermore, the present invention is based on a technical concept that requires that a shock wave be generated in the liquid phase before the multiphase flow reaches the surface of the substrate, and that the gas-phase microbubbles of the multiphase flow can be mixed as a third phase into the particles in the multiphase fluid containing the liquid phase and the particle-solid phase before a shock wave is generated at the tip of the particles in the flow direction. An example of a specific method for this is shown in the Examples, but the present invention is not limited to this method (Novelty (6) - New Technical Concept).

[0050] Furthermore, even if the three-phase flow separates before reaching the substrate surface, the separated three-phase flow becomes particles flying in space as an isolated system, and a shock wave instantly passes through the particles and collides with the substrate surface. At this time, the shock wave collides with unbroken microbubbles present near the substrate surface, thereby realizing the technical concept of the present invention (Novelty (7) - New Technical Concept).

[0051] [Detailed explanation of the new principle patentability of the present invention] Hereinafter, the solid-phase particles used in the present invention will be described as quantum dot particles. (1) Kinetic energy of quantum dot particles The weight of a single quantum dot particle is, for example, 5.24 g / cm for a 10 nm cubic FeO quantum dot. 3 )(L=8.47nm(0.847A)) 10* / (8.47)*5.24*(10^(-9*3))= 6.18654E-27. [m][g]→[m][kg]E-3. ...(Formula 1) If we calculate the kinetic energy for this mass, Ek= (1 / 2)*(6.18654E-24)*v 2 J [m*kg] ················(Formula 2) This becomes:

[0052] (2) Quantum dot association energy The main forces acting between colloidal particles are the London-vander Waals attractive force and the electrostatic repulsive force (repulsion) due to the surface charge of the particles. If the attractive force is large, the particles will aggregate, and if the repulsive force is large, the particles will remain dispersed and stable (DLVO theory). The total potential energy V acting between the particles is T is the electrostatic repulsive energy V R and the attractive van der Waals potential V A It is expressed as the sum of V T =V R + V A Generally, the potential curve has a quadratic minimum Vmin, and in many cases the depth of Vmin is shallow, about a few kT. The kinetic energy Ek (J: Joule) of an object with mass m (kg) moving at a velocity v (m / s) is E k =(1 / 2)mv 2 where k is the Boltzmann constant, 1.381 × 10 -23 JK -1 So, when T=300K Ek=1.381*10^(-23)*300=4.14*10^21 J [m / kg] (Formula 3) (the cohesive energy at which quantum dot particles aggregate in solution).

[0053] (3) Particle velocity of quantum dot particles Here, if (2) and (3) are equal, the value of V is V 2 = (4.14*10^21) / ( (1 / 2)*(6.18654E-24)) V=3.6584E+22 m / s (Formula 4) (particle velocity of the energy required for the quantum dot particle).

[0054] (4) Acceleration of particles due to bubble explosion caused by shock waves a) In the present invention, "fixing on the surface of a substrate" means, in other words, "embedding quantum dot particles inside a layer of inorganic or composite material (a layer containing mesoscopic quantum dot aggregates, called a "particle layer") on the surface of a substrate, which is formed of particles of 0.1 to 100 μm. b) The value of the particle layer (Equation 3) above is the potential (J / 2 particle bond) when two particles are assumed to be associated with each other in the particle layer, and the speed of the quantum dot particle required to dissociate and embed it within the particle layer by collision energy greater than this potential is the calculated result (Equation 4). It is impossible to obtain this particle speed with ordinary jet flow generation equipment.

[0055] Since a completely different method was required, they conducted intensive research and found that it was feasible to use a method in which "shock waves are generated in water, causing bubbles to collide with the shock waves on the surface of the substrate, causing the bubbles to explode, and at the same time causing microparticles to be present and accelerated by the explosive force" (adding acceleration to microparticles by causing bubbles to explode due to shock waves).

[0056] (5) Results of feasibility study A) How the shock wave is generated is as follows: a pulsed jet water flow generator is used to inject a pulsed jet into a low-velocity water flow at a speed faster than the speed of sound in water (1400 m / s), generating a shock wave as a conical warhead wave with the tip of the quantum dot particle, which is moving at a speed faster than the speed of sound, as its apex. Furthermore, gas is mixed into this jet flow to generate and mix microbubbles. Until the mixed liquid hits the substrate surface, the microbubbles are subjected to a certain amount of shock wave pressure, but they maintain their distorted shape and do not explode.

[0057] B) The gas microbubbles are formed by using an orifice to jet gas into a liquid phase in which solid particles are dispersed. This creates a three-phase mixed flow of solid particles, gas microbubbles, and liquid. This mixed flow is then subjected to a shock wave that causes the microbubbles to move through space as a multiphase flow.

[0058] c) The method of generating and mixing the fluid is the above method a) which is an example, and is not limited to this method.

[0059] d) To understand what happens when this mixed-phase flow impinges on the surface of a substrate, we performed a numerical analysis of the interaction between a bubble and an underwater shock wave. Here, we used the Hybrid Particle Level Set method in the Ghost Fluid method to improve mass conservation, and corrected the physical quantities near the interface using a one-dimensional Riemann exact solution, which can suppress numerical oscillations at the interface of a gas-liquid two-phase flow. Figure 2 shows the results of this numerical analysis, showing the time evolution of the bubble shape and isobars when a shock wave in water impinges on a cylindrical air bubble.

[0060] As shown in Figure 2, part of the shock wave passes through the bubble, while most of the remaining part is reflected within the bubble, after which a strong expansion wave is formed behind the bubble. At (vi), a jet is generated from the interface on the side where the shock wave hits the bubble, and at (vii) and (viii), the pressure wave propagating within the bubble hits the downstream bubble surface, and the jet hits the downstream bubble surface, generating extremely high pressure at the collision surface. The maximum pressure at the point where the jet hits reaches approximately 58 GPa, causing an explosion toward the wall. At this moment, the quantum dot particles are accelerated by the explosive force toward the wall (perpendicular to the substrate) and become embedded in the particle layer.

[0061] [Inventive step due to the new technological concept of this invention for various problems] [Issue 1] The electrolyte in lithium-ion batteries is a flammable and dangerous material, posing a risk of fire and explosion. To address this issue, development is underway on non-flammable all-solid-state batteries, which use a solid electrolyte. Microparticles of inorganic materials are used as the non-flammable material, but to improve conductivity and durability, not only is it necessary to increase the contact between the microparticles, but technology is also essential and important for compactly sealing the microparticles so that their crystal surfaces are bonded. Furthermore, the inorganic materials used in the positive and negative electrodes of batteries undergo changes in their crystal structure due to the movement of lithium ions into and out of the particle crystals, which causes the battery to expand and contract. This reduces durability and performance, posing a major challenge that must be resolved.

[0062] [Challenge 2] Furthermore, there is a need for mass-production technology, known as R2R technology, in which the thinnest possible film (e.g., 0.1 to 100 μm) is laminated (at least four layers) over a given area (e.g., 50 cm x 50 cm) and the film is continuously wound in the longitudinal direction. Such film is cut to a certain length to form strips, which are then folded and stacked to increase the storage capacity per volume. To achieve this, the bulge caused by the folding must be minimized as much as possible. Theoretically, this is a right-angle fold, but in practice, the bend is a semicircle, with the radius minimized. The smaller the radius, the greater the deterioration in performance due to cracks, durability, and separation and peeling of the laminations. Therefore, there is a need to develop a laminate structure that is resistant to bending and to apply presses with optimal strength to the thin film laminates.

[0063] [Challenge 3] Pressing is an extremely important process, and typically uses press rolls. Pressure is applied between a pair of press rolls to compress and roll the electrode material. The thickness of the electrode material is determined by the mechanical precision of the press rolls, such as the roundness, cylindricity, and runout. If the mechanical precision of the press rolls is poor, this will directly lead to variations in the thickness of the electrode material, resulting in variations in battery performance and quality issues such as batteries being too thick to fit into a case. Lithium-ion batteries are made by stacking multiple layers of electrode material, so even a variation of just a few microns in a single electrode can result in significant thickness variation when stacked. Therefore, press rolls are required to have extremely high mechanical precision of less than a few microns.

[0064] [Challenge 4] This type of pressing requires high pressures of several hundred MPa or more, and cracking of electrode active material particles is one of the major challenges during this process. High local stress occurs at the contact points between brittle cathode active material particles, leading to cracks in the cathode active material particles, posing a significant quality control challenge. Furthermore, in all-solid-state batteries using sulfide-based solid electrolytes, high-potential cathode active materials (4 V or higher) often result in high resistance at the cathode / electrolyte interface. A commonly used method to reduce the resistance at this cathode / electrolyte interface is to coat the cathode active material particles with a 5–10 nm thick oxide-based solid electrolyte. (The Micromeritics No. 64 (2021) 9-17 DOI: 10.24611 / micromeritics.2021006 Fundamentals and Research Trends of Powder-Molded All-Solid-State Batteries) The most widely used method for coating particles is tumbling fluidized spray coating. They are made by spraying a coating sol onto active material particles of several to 10 μm in size while rolling and fluidizing them, then drying and baking them. In short, the current state of all-solid-state lithium-ion battery manufacturing is at the level of the artisanal techniques of a small factory that applies a pigment top coat, and does not yet reach a high level of technology in terms of reproducibility of high-performance functions, durability, etc.

[0065] [Summary of Issues] As mentioned above, existing manufacturing methods for all-solid-state batteries have many technical issues that need to be resolved in terms of quality control, durability, yield, and performance improvement.

[0066] [Issue 5] A drying process is required to evaporate the solvent in the ink used for printing, and in R2R mass production machines, a 50 to 80 meter long belt transport is required for the drying process, which poses major challenges in terms of cost and carbon emissions during the drying process.

[0067] [Inventive Step 1 of the Invention] The present invention has the inventive step of solving all of these problems at once. That is, according to the present invention, high-pressure pressing is not required, and it is possible to encapsulate particles so that their crystal faces are closely and compactly bonded together, which results in higher performance than with high-pressure pressing. Furthermore, there is no problem with cracking of electrode active material particles that occurs during the high-pressure pressing process, and long belt conveyance for the drying process is not required, which significantly reduces carbon emissions.

[0068] [Inventive step 2] This invention makes it possible to stack quantum dot particles in various sizes, and through new, highly functional stacking and coating (quantum dot coating) with a dense structure that far surpasses conventional pressing methods, it is possible to create new industrial products using quantum dots.

[0069] [Inventive Step 3] The quantum dots used in this invention have a small mass and the volume of each particle is extremely small, but since the number of particles sprayed is large, the total mass is at a practical level.In addition, since the spray speed is at the sonic level, the deposition speed on the surface is high, making it suitable for mass production.

[0070] [Inventive Step 4] The technology of the present invention can be used for components and products that use stacked quantum dot semiconductors, such as solar cells, LEDs, electronic components, semiconductor components, semiconductor products, and optoelectronic products, so by changing the manufacturing process of these products to the process of the present invention, high performance, high durability, and high yield production can be achieved, and manufacturing costs can also be reduced. [Example]

[0071] A more specific example of the method for immobilizing solid particles using the three-phase multiphase flow generating device 100 of FIG. 1 will be described.

[0072] Argon gas was used as the gas phase to be passed through the gas phase passage 20. The argon gas had a pressure P of 0.3 to 0.6 MPa, a maximum flow rate Qmax of 500 NL / min, a temperature T of 20 to 30°C, and Mac (shock wave velocity) of >1.0.

[0073] The mixture of particles (20 nm iron sulfide quantum dots) and liquid (water) was passed through the mixed-phase passage 30. The pressure (P) of this mixture was 0.3-0.6 MPa, the flow rate (Q) was 100-200 ml / min, the temperature (T) was 20-30°C, and the shock wave velocity (Mac) was greater than 1.0.

[0074] In this case, two shock waves (Mac>1.0)—one for gas (argon gas) and one for liquid (a solid-liquid mixture of quantum dots and water)—overlap at the same location. According to the principle of superposition, when two shock waves overlap at the same location, the displacements of each wave are added together, resulting in the synthesis of a water shock wave and an air shock wave, forming a new shock wave. Furthermore, the 20-nm quantum dot diameter is smaller than the wavelength of light and can be considered a dissolved ionic species. Therefore, the inertial and viscous drags associated with the Reynolds number of particles and fluids in hydrodynamics are negligible. In other words, the quantum dot velocity is equal to the Mac velocity of the liquid. A new shock wave is formed in the mixture of the liquid, quantum dots, and microvalves (a three-phase mixed jet flow) and is ejected from the nozzle exit as a jet flow (three-phase multiphase flow47).

[0075] By placing a substrate 51, at least a portion of whose surface is covered with a layer 53 made of fine particles, in front of the three-phase multiphase flow 47, the quantum dots contained in the three-phase multiphase flow 47 are fixed onto the substrate 51.

[0076] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and that provides similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0077] 20...gas phase passage, 25...gas phase flow (jet stream), 27...gas phase, 30... mixed phase passage, 32... orifice, 35...Flow of mixed phase of particle and liquid (jet liquid flow), 37...Flow of mixed phase of particle and liquid, 45...Three-phase mixing layer flow (three-phase multiphase flow), 47...Three-phase mixed phase, 51...substrate, 53...layer of fine particles, 55...fixed solid-phase particles, 100...Three-phase multiphase flow generator.

Claims

1. 1. A method for immobilizing solid phase particles on a surface of a substrate, comprising: a step of preparing a fixing substrate as the substrate, at least a part of the surface of which is coated with a layer made of fine particles in advance; forming a three-phase multiphase flow consisting of a solid phase containing the solid particles, a gas phase, and a liquid phase, and applying acceleration to the solid particles to generate shock waves in the three-phase multiphase flow; causing the three-phase multiphase flow to impinge on a surface of the fixing substrate; and A method for fixing solid particles, characterized in that the shock wave causes gas bubbles in the gas phase to contract, expand, and explode on the surface of the fixing substrate, and the kinetic energy of the solid particles accompanying the explosion fixes the solid particles on the surface of the substrate.

2. 2. The method for immobilizing solid-phase particles according to claim 1, wherein the liquid phase is water.

3. The formation of the three-phase multiphase flow and the generation of the shock wave, a pulse jet water flow generator is used to accelerate the water dispersion containing the solid particles to a speed equal to or faster than the speed of sound in water, and the water dispersion is fired in a pulse, and the accelerated water dispersion is injected into a water flow having a speed lower than that of the accelerated water dispersion, thereby applying acceleration to the solid particles and moving the solid particles at a speed equal to or faster than the speed of sound in water; forming the three-phase multiphase flow by mixing gas microbubbles into the dispersed water; 3. The method for immobilizing solid-phase particles according to claim 2, wherein the method is carried out by:

4. In forming the three-phase multiphase flow, The dispersed water in the pulse jet water flow generator is passed through an orifice; 4. The method for immobilizing solid particles according to claim 3, wherein the gas microbubbles are mixed into the dispersion water by jetting gas into the orifice from inside or outside the dispersion water.

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