Functional fluid and preparation method thereof
By forming a functional layer of composite particles on the surface of the current collector, the problems of discontinuous conductive network and weak interfacial bonding in traditional current collectors are solved, achieving high conductivity, low internal resistance and long life of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-11
- Publication Date
- 2026-04-10
AI Technical Summary
Traditional current collector coatings suffer from discontinuous conductive networks, weak interfacial bonding, and poor structural stability, leading to increased internal resistance and decreased rate performance in lithium-ion batteries during cycling, and easy degradation of conductivity during charge and discharge.
The functional layer of composite particles is adopted. The composite particles include a core and a shell. The core is composed of metal materials, binders and conductive agents, and the shell is composed of oxide materials and coupling agents. A continuous conductive network is formed on the surface of the substrate through spray drying technology, which enhances the adhesion and interfacial bonding force and forms a dense protective layer.
It improves the conductivity and structural stability of lithium-ion batteries, reduces internal resistance, enhances rate performance and lifespan, and improves mechanical strength and fatigue resistance.
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Figure SMS_1
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of current collectors, in particular to a functional fluid and a preparation method thereof. BACKGROUND
[0002] As a key component of lithium ion batteries, the current collector is responsible for collecting and transmitting electric current, and its performance directly affects the overall performance of lithium ion batteries, such as internal resistance, rate performance and cycle life. Traditional current collectors are usually made of metal foils (such as copper foil, aluminum foil), which have single structure and limited functions, and are difficult to meet the development needs of high energy density, high power and long life lithium ion batteries.
[0003] The prior art improves the performance of the battery by surface modification of the current collector, for example, by coating a conductive coating on the surface of the metal foil or setting a porous structure layer to enhance the bonding force between the current collector and the electrode active material or improve the current distribution. However, such coatings often have problems such as discontinuous conductive network, weak interfacial bonding force, poor structural stability, etc., which can lead to increased internal resistance, decreased rate performance, and even coating peeling during the cycle process, affecting the reliability and service life of the battery. In addition, the conductive agent is easily oxidized by the electrolyte or oxygen in the air during the charging and discharging process, leading to the degradation of the conductive performance, and thus affecting the long-term cycle stability of the battery. SUMMARY
[0004] In order to solve the problems of discontinuous conductive network, weak interfacial bonding force and poor structural stability of the coating added on the surface of the existing current collector, the present application provides a functional fluid and a preparation method thereof.
[0005] According to a first aspect of the present application, a functional current collector is provided, which comprises a substrate and a functional layer provided on at least one surface of the substrate, the functional layer containing composite particles, the composite particles comprising a core and a shell coated on the surface of the core; the core contains a metal material, a binder and a conductive agent, the mass fraction of the metal material in the core is 3.5-25%, and the mass fraction of the conductive agent in the core is 34-49%; the shell contains an oxide material and a coupling agent.
[0006] The functional current collector provided by the present application sets a functional layer containing composite particles on the surface of a substrate, the composite particles have a core-shell structure, first, the mass ratio of the metal material and the conductive agent in the inner core of the composite particles is adjusted to the above range, a continuous conductive network can be formed between the metal material and the conductive agent, the conductivity of the functional current collector is improved, thereby reducing the internal resistance of the lithium ion battery using the functional current collector, so that the rate performance of the lithium ion battery is improved, and second, the oxide material and the coupling agent are used as components of the shell, the oxide material can form a dense protective layer to prevent the oxidation of the conductive agent in the inner core, thereby prolonging the service life of the lithium ion battery using the composite current collector, the coupling agent can efficiently modify the surface of the particles and effectively improve the chemical properties of the particle surface, thereby enhancing the interfacial bonding force between the composite particles and between the composite particles and the substrate, and improving the comprehensive performance of the functional current collector.
[0007] Preferably, the metal material includes one of copper powder and aluminum powder.
[0008] The functional current collector provided by the present application can be used as a negative electrode current collector and a positive electrode current collector, when used as a negative electrode current collector, the metal material in the inner core of the composite particles is copper powder, which is used as a conductive phase of the negative electrode current collector, and when used as a positive electrode current collector, the metal material in the inner core of the composite particles is aluminum powder, which is used as a conductive phase of the positive electrode current collector.
[0009] The working environment of the lithium ion battery negative electrode is a low potential (close to the potential of metallic lithium), and aluminum will undergo lithium-aluminum alloying reaction (form Li-Al alloy) at a low potential, resulting in corrosion failure of the current collector, in the present solution, copper is used as a conductive phase of the negative electrode current collector, and copper has excellent chemical stability at a low potential and will not react with lithium.
[0010] The working environment of the lithium ion battery positive electrode is a high potential, and copper is easily oxidized at a high potential, resulting in dissolution of the current collector, and aluminum is used as a conductive phase, in the present solution, aluminum is used as a conductive phase of the positive electrode current collector, and aluminum will form a dense oxide film (Al2O3) at a high potential, which can prevent further reaction of aluminum and has good chemical stability.
[0011] Copper and aluminum are excellent conductive materials among metals (the electrical conductivity of copper is about 5.96×10 7 S / m, and the electrical conductivity of aluminum is about 3.77×10 7In the functional current collector, the metal material (copper powder or aluminum powder) is used as the main conductive phase, which has the following advantages: first, it is beneficial to build a continuous conductive network, ensuring fast electron transmission, which is the core guarantee for the current collection function of the functional current collector; second, the copper powder / aluminum powder can be used as a skeleton support in the composite particles, which can improve the mechanical strength (such as bending resistance and tensile resistance) of the functional current collector, avoiding the problem of structural collapse when relying only on the binder and carbon material; third, the metal material (copper powder / aluminum powder) has a closer contact with the electrode active material and other conductive agents (carbon nanotubes, acetylene black), which can reduce the interface contact resistance between different phases and improve the overall conductivity efficiency.
[0012] Preferably, the binder includes at least one of polyvinylidene fluoride (PVDF) and styrene-butadiene rubber.
[0013] Preferably, the conductive agent includes at least one of acetylene black, conductive carbon black, carbon nanotubes, and graphene.
[0014] Preferably, the oxide material includes at least one of titanium dioxide, silicon dioxide, zirconium oxide, aluminum oxide, and zinc oxide.
[0015] Preferably, the coupling agent includes at least one of a silane coupling agent, an aluminate coupling agent, and a titanate coupling agent, and the silane coupling agent includes at least one of KH-560, KH-550, KH-561, KH-570, and KH-792.
[0016] Preferably, the conductive agent includes acetylene black and carbon nanotubes, and the mass percentage of acetylene black in the core is 5.8-19%, and the mass percentage of carbon nanotubes in the core is 3.5-16%.
[0017] The acetylene black and carbon nanotubes are compounded as the conductive agent in the core of the composite particles, and the mass percentage of acetylene black and carbon nanotubes in the core is controlled within the above range. The carbon nanotubes have high specific surface area and excellent conductivity, which can significantly improve the electrical performance of the functional current collector. The acetylene black can effectively fill the gaps between the particles and enhance the continuity of the conductive network. The synergistic effect of the two can significantly reduce the interface resistance and improve the electron transmission efficiency of the functional current collector.
[0018] Preferably, the core further contains an additive, and the additive includes a dispersing agent and a plasticizer. The mass percentage of the dispersing agent in the core is 1.1-6.5%, and the mass percentage of the plasticizer in the core is 1.1-8%. The dispersing agent includes at least one of sodium polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, and sodium hexametaphosphate. The plasticizer includes at least one of dibutyl phthalate, dioctyl phthalate, tributyl phosphate, and dioctyl adipate.
[0019] The scheme introduces the dispersant and the plasticizer into the core of the composite particles and controls the mass ratio of the two in the core within the above range, so as to improve the flexibility of the functional current collector.
[0020] Preferably, the average particle size of the core is 4-6 μm, and the thickness of the shell is 50-200 nm.
[0021] Controlling the average particle size of the core and the thickness of the shell of the composite particles in the functional layer of the functional current collector within the above range can improve the stability of the functional current collector during long-term charge-discharge cycles.
[0022] If the average particle size of the core is too large and the thickness of the shell is too large (>200 nm), the ion transport path of the functional current collector will be lengthened, resulting in a decrease in the rate performance of the lithium ion battery using the functional current collector, an increase in the internal resistance of the composite particle material, a decrease in the charge-discharge efficiency of the lithium ion battery, and an increase in the brittleness of the functional layer, thereby causing the functional layer of the functional current collector to be prone to cracking during the cycle process; if the shell thickness is too small (<50 nm), the particles cannot be effectively protected, the active material in the core is prone to corrosion by the electrolyte, and the oxidation resistance is insufficient, resulting in poor long-term cycle stability of the functional current collector.
[0023] Preferably, the thickness of the functional layer is 5-50 μm.
[0024] Preferably, the substrate is a polyethylene terephthalate (PET) substrate.
[0025] According to a second aspect of the present application, a preparation method of a functional current collector is provided, comprising the following steps: S1. Preparing a precursor slurry containing a metal material, a binder, a conductive agent, and a first solvent, wherein the mass ratio of the metal material in the precursor slurry is 30-45%, and the mass ratio of the conductive agent in the precursor slurry is 3-22%; S2. Spraying the precursor slurry on at least one surface of a substrate by spray drying to form a functional layer, thereby obtaining a semi-finished product; S3. Uniformly dispersing an oxide material and a coupling agent in a second solvent to prepare a coating slurry; S4. Atomizing the coating slurry and contacting it with the functional layer of the semi-finished product, and then performing solidification sintering to obtain the functional current collector.
[0026] The method for preparing the functional current collector provided in the present application utilizes spray drying to spray the precursor slurry prepared from a metal material, a binder, a conductive agent and a first solvent on the surface of a substrate to form a functional layer. In the spray drying process, the first solvent volatilizes and the metal material, the binder and the conductive agent form a core. Then, a coating slurry containing an oxide material and a coupling agent is atomized and contacted with the core in the functional layer and is subjected to solidification and sintering. In this process, the atomized coating slurry contacts with the core and is subjected to solidification and sintering to form a shell on the surface of the core. The core and the shell coated on the surface of the core form a composite particle and serve as a component of the functional layer. The metal material contained in the core of the composite particle of the functional layer of the functional current collector prepared by the above method can form a continuous conductive network with the conductive agent, thereby improving the conductivity of the functional current collector, reducing the internal resistance of a lithium ion battery using the functional current collector, and improving the rate performance of the lithium ion battery. Meanwhile, the binder in the core can enhance the adhesion between the component particles (the metal material and the conductive agent) in the core, thereby ensuring the structural stability and flexibility of the functional layer, improving the mechanical strength and fatigue resistance of the functional current collector during the charging and discharging process, the oxide material in the shell can form a dense protective layer to prevent the conductive agent in the core from being oxidized, thereby prolonging the service life of a lithium ion battery using the composite current collector, and the coupling agent can efficiently modify the surface of the particles and effectively improve the chemical properties of the particle surface, thereby enhancing the interfacial bonding force between the composite particles and between the composite particles and the substrate and improving the comprehensive performance of the functional current collector.
[0027] Furthermore, the preparation process of the functional current collector provided in the present application realizes the integration of the atomization and dispersion, drying and granulation and surface coating of the precursor slurry by spray drying, realizes the controllable microstructure composite of the conductive substrate and the functional layer material, is suitable for the large-scale production of high-performance composite current collectors in the fields of lithium ion batteries, supercapacitors and the like, and can complete the one-step connection of the core granulation and surface coating in the same drying equipment, thereby avoiding the traditional segmented transfer link and solving the problems of long segmented process, weak interfacial bonding and poor structural uniformity in the traditional process.
[0028] Preferably, in S1, the metal material is copper powder or aluminum powder.
[0029] In the process of preparing the precursor slurry, if the mass proportion of the copper powder / aluminum powder in the precursor slurry is too high, the viscosity of the prepared precursor slurry will increase, subsequent ball milling will be difficult, and the density of the prepared functional current collector will be too large and the flexibility will decrease. If the mass proportion of the copper powder / aluminum powder in the precursor slurry is too low, the conductive network will be sparse, the conductivity of the finally prepared functional current collector will be insufficient, and the internal resistance of a lithium ion battery using the functional current collector will increase.
[0030] Preferably, the average particle size of the copper powder is 1-5 μm.
[0031] Preferably, the average particle size of the aluminum powder is 2-8 μm.
[0032] The copper powder / aluminum powder used in the present solution is a micron-sized particle, and the average particle size thereof is controlled within the above range, which can ensure the continuity of the conductive network while avoiding the problem of reduced slurry flowability caused by excessively large particles.
[0033] If the average particle size of the copper powder / aluminum powder is excessively large, it will be difficult to refine the copper powder / aluminum powder in the subsequent ball milling process, and the flowability of the precursor slurry prepared therefrom will be poor, which will eventually lead to a decrease in the electrical conductivity of the functional current collector prepared. If the average particle size of the copper powder / aluminum powder is excessively small, the specific surface area of the copper powder / aluminum powder will be excessively large, which will increase the viscosity of the precursor slurry prepared therefrom, making it difficult to atomize in the subsequent spray drying process, and the particles will easily agglomerate during the sintering process.
[0034] Preferably, in S1, the binder comprises at least one of polyvinylidene fluoride (PVDF) and styrene-butadiene rubber.
[0035] Preferably, in S1, the conductive agent comprises acetylene black and carbon nanotubes.
[0036] Preferably, the mass fraction of the acetylene black in the precursor slurry is 5-12%, and the average particle size of the acetylene black is 30-50 nm.
[0037] Preferably, the mass fraction of the carbon nanotubes in the precursor slurry is 3-10%, and the length of the carbon nanotubes is 1-10 μm and the outer diameter thereof is 10-100 nm.
[0038] In the preparation process of the precursor slurry, acetylene black and carbon nanotubes are used as the conductive agent, and the mass fraction of the acetylene black and the carbon nanotubes in the precursor slurry is controlled within the above range. The carbon nanotubes have a high specific surface area and excellent electrical conductivity, which can significantly improve the electrical performance of the functional current collector. The acetylene black can effectively fill the gaps between the particles and enhance the continuity of the conductive network. The synergistic effect of the two can significantly reduce the interfacial resistance and improve the electron transport efficiency of the functional current collector.
[0039] If the mass fraction of the carbon nanotubes in the precursor slurry is excessively high, it will be difficult to disperse the carbon nanotubes in the first solvent, and the carbon nanotubes will easily agglomerate, thereby causing the precursor slurry to separate, which will increase the interfacial resistance of the functional current collector prepared. If the mass fraction of the carbon nanotubes in the precursor is excessively low, there will be insufficient conductive paths to assist the copper powder / aluminum powder in forming a continuous conductive network, which will lead to a decrease in the rate performance of the battery prepared.
[0040] If the mass percentage of acetylene black in the precursor slurry is too high, the viscosity of the precursor slurry will increase, the pores on the surface of the core particles will be blocked in the subsequent coating stage, and the combination between the shell and the core will be affected; if the mass percentage of acetylene black in the precursor slurry is too low, the filling effect will be insufficient, the gap between the copper powder / aluminum powder and the carbon nanotube will be too large, and thus the conductivity of the functional current collector prepared will be reduced.
[0041] Meanwhile, the carbon nanotube with a length of 1-10 μm and an outer diameter of 10-100 nm is conducive to the construction of a three-dimensional conductive framework, and too short, too long or too thick will result in a non-uniform conductive network, thereby reducing the rate performance of the lithium ion battery prepared from the functional current collector. The acetylene black with an average particle size of 30-50 μm can fill the gap between the copper powder / aluminum powder and the carbon nanotube and assist in conduction, and too large or too small particle size will easily lead to agglomeration or increase the viscosity of the slurry.
[0042] Preferably, in S1, the particle size of the binder is 50-200 μm.
[0043] Preferably, in S1, the mass percentage of the binder in the precursor slurry is 12-20%.
[0044] In the preparation process of the precursor slurry, the binder with a particle size of 50-200 μm and the mass percentage of the binder in the precursor slurry controlled between 12-20% can ensure the dissolution and bonding efficiency of the binder and also ensure that the binder has good bonding strength and improves the mechanical strength of the functional current collector.
[0045] Too large particle size of the binder will make it difficult to be fully dissolved in the first solvent, and the bonding strength will be insufficient, and the functional current collector will easily delaminate; too small particle size will easily lead to too high viscosity of the slurry; too high mass percentage of the binder in the precursor slurry will result in too high viscosity of the precursor slurry, making it difficult to be atomized, and the hardness of the finally prepared core and composite particles will be too large and easily brittle; and too low mass percentage of the binder will easily result in insufficient bonding strength and easy peeling between particles, thereby reducing the mechanical strength of the functional current collector.
[0046] Preferably, in S1, the preparation raw material of the precursor slurry further includes an additive, the additive includes a dispersant and a plasticizer, the mass percentage of the dispersant in the precursor slurry is 1-4%, and the mass percentage of the plasticizer in the precursor slurry is 1-5%; the dispersant includes at least one of sodium polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone and sodium hexametaphosphate; and the plasticizer includes at least one of dibutyl phthalate, dioctyl phthalate, tributyl phosphate and dioctyl adipate.
[0047] The dispersant and the plasticizer are added in the preparation process of the precursor slurry, and the mass proportions of the two in the precursor slurry are controlled within the above ranges, which can effectively reduce the agglomeration phenomenon between particles, improve the flowability and uniformity of the precursor slurry, ensure the uniform coating of the functional layer on the surface of the substrate by combining the spray drying and atomization coating processes, avoid the performance fluctuation caused by the local uneven thickness, and ensure the structural uniformity of the product. In addition, the plasticizer can improve the flexibility and processing performance of the binder, so that the composite particles are not easy to break during the molding and subsequent use, and the mechanical performance of the composite current collector is improved.
[0048] If the mass proportion of the dispersant in the precursor slurry is too high, the stability of the precursor slurry will decrease due to excessive dispersion, and the composite particles are easy to break after spray drying; if the mass proportion of the dispersant in the precursor slurry is too low, the dispersion of the precursor slurry will be insufficient, and the copper powder / aluminum powder and carbon nanotubes are easy to agglomerate, which finally leads to poor structural uniformity of the functional current collector.
[0049] If the mass proportion of the plasticizer in the precursor slurry is too high, the plasticization will be excessive, the binding force of the binder will decrease, the composite particles are easy to deform, and too much plasticizer will remain after drying, which affects the conductivity of the functional current collector; if the mass proportion of the plasticizer in the precursor is too low, the flowability of the precursor slurry will be insufficient, and the droplet size will be uneven during atomization, which makes the hardness of the finally prepared functional current collector too high and the flexibility too poor.
[0050] Preferably, the average particle size of the dispersant is 100-300 nm.
[0051] In the preparation process of the precursor slurry, the dispersant with the above particle size range is used, which can slowly dissolve and release the dispersing groups in the first solvent, reducing the risk of rapid aggregation of the dispersant due to too fine particle size of the dispersant.
[0052] Preferably, in S1, the mass proportion of the first solvent in the precursor slurry is 20-30%.
[0053] Preferably, in S1, the first solvent is N-methyl pyrrolidone (NMP).
[0054] In the preparation process of the precursor slurry, the mass proportion of the first solvent NMP is controlled within the above range, which can ensure that the solid content and viscosity of the precursor slurry are within the appropriate range and improve the uniformity of the precursor slurry, thereby improving the performance of the finally prepared functional current collector.
[0055] If the mass ratio of NMP in the precursor slurry is too high, the solid content of the precursor slurry is too low, the drying energy consumption is increased, and the porosity of the composite particles prepared is too high, resulting in insufficient mechanical strength of the functional current collector prepared finally; if the mass ratio of NMP in the precursor slurry is too low, the viscosity of the precursor slurry is too high, the subsequent conveying and atomization are difficult, and the dispersion of each component in the precursor slurry is insufficient during subsequent ball milling, thereby affecting the performance of the functional current collector prepared finally.
[0056] Preferably, in S3, the oxide material comprises at least one of titanium dioxide, silicon dioxide, zirconium oxide, aluminum oxide, and zinc oxide.
[0057] Preferably, in S3, the mass ratio of the oxide material in the coating slurry is 60-90%.
[0058] During the preparation of the coating slurry, controlling the mass ratio of the oxide material within the above range can improve the structural stability and electrolyte corrosion resistance of the functional current collector prepared during the cycle process.
[0059] If the mass ratio of the oxide material in the coating slurry is too high, the brittleness of the coating shell increases, which is prone to cracking, and at this time, the proportion of the coupling agent in the coating slurry is relatively reduced, the interfacial bonding force between the composite particles in the functional layer and between the composite particles and the substrate is weakened, and thus the functional current collector is prone to shedding of the coating shell and the functional layer during the cycle process; if the mass ratio of the oxide material in the coating slurry is too low, it is difficult for the coating slurry to form a continuous and complete coating shell on the surface of the core, the protection of the active material in the core is weakened, and the oxidation resistance and electrolyte corrosion resistance of the functional current collector prepared are reduced.
[0060] Preferably, in S3, the average particle size of the oxide material is 50-200 nm.
[0061] During the preparation of the coating slurry, using the oxide material with a nanoscale size and controlling the average particle size thereof within the above range can ensure the uniformity of the coating shell. If the average particle size of the oxide material is too large, the compactness of the coating shell is easily reduced; if the average particle size of the oxide material is too small, agglomeration is easily occurred during the coating stage, resulting in an increase in defects of the coating shell.
[0062] Preferably, in S3, the coupling agent comprises at least one of a silane coupling agent, an aluminate coupling agent, and a titanate coupling agent, and the silane coupling agent comprises at least one of KH-560, KH-550, KH-561, KH-570, and KH-792.
[0063] Preferably, in S3, the mass ratio of the coupling agent in the coating slurry is 5-30%.
[0064] By controlling the mass ratio of the coupling agent in the shell of the composite particles in the coating slurry within the above range, the conductivity of the functional current collector can be reduced, and the structural stability of the functional current collector in the cycle process can be improved.
[0065] If the mass ratio of the coupling agent in the coating slurry is too high, the thickness of the coating shell will increase, the ion transmission resistance will increase, and excess coupling agent can form an insulating layer at the interface, thereby reducing the conductivity of the prepared functional current collector; if the mass ratio of the coupling agent in the coating slurry is too low, the oxide material will not be firmly combined with the core, the coating shell will be easily peeled off, and the cycle stability of the functional current collector will be reduced.
[0066] Preferably, in S1, the viscosity of the precursor slurry is 800-1500 mPa·s, and the solid content is 65-75 wt%.
[0067] Preferably, in S3, the viscosity of the coating slurry is 300-500 mPa·s.
[0068] Preferably, in S1, the precursor slurry is prepared by the following steps: mixing the metal material, the binder, the conductive agent, and the dispersant, and stirring at a speed of 80-120 r / min for 10-20 min to obtain a solid powder, adding the first solvent to the solid powder and stirring at a speed of 150-200 r / min for 15-25 min to obtain a first mixture, and then adding the plasticizer to the first mixture and stirring at a speed of 250-350 r / min for 25-35 min to obtain the precursor slurry.
[0069] In the preparation process of the precursor slurry, first, solid premixing is performed, that is, the metal material, the binder, the conductive agent, and the dispersant are stirred at a speed of 80-120 r / min for 10-20 min to obtain a solid powder, then solvent dispersion is performed, that is, the first solvent is added to the solid powder and stirred at a speed of 150-200 r / min for 15-25 min to obtain a first mixture, and finally, deep mixing is performed, that is, the plasticizer is added to the first mixture and stirred at a speed of 250-350 r / min for 25-35 min to obtain the precursor slurry. By controlling the speed and stirring time in the solid premixing stage, the solvent dispersion stage, and the deep mixing stage within the above range, the dispersion uniformity of the materials in the first solvent can be improved, the continuous conductive network between the metal material and the conductive agent can be effectively constructed, the conductivity of the prepared functional current collector is improved, the internal resistance of the lithium ion battery using the functional current collector is reduced, and the rate performance of the lithium ion battery is improved.
[0070] If the rotation speed in the solid premixing stage is too high (>120 r / min), the metal materials (copper powder / aluminum powder), conductive agents (carbon nanotubes, acetylene black) and other particles can be broken due to mechanical stress, resulting in uneven distribution of the average particle size, and the aspect ratio of the carbon nanotubes in the conductive agent decreases after breaking, which cannot effectively build a three-dimensional conductive network, ultimately leading to a decrease in the continuity of the conductive network of the functional current collector, resulting in an increase in the internal resistance of the lithium ion battery using the functional current collector; if the rotation speed in the solid premixing stage is too low (<80 r / min), the solid powder mixing will not be sufficient or clumping will occur, resulting in uneven microstructure of the composite particles in the functional layer of the functional current collector prepared, and insufficient conductivity or adhesion in local areas, which is prone to cracks.
[0071] If the stirring time in the solid premixing stage is too long (>20 min), the surfaces of the materials are prone to oxidation, thereby reducing the electrochemical stability of the lithium ion battery using the functional current collector prepared and shortening the cycle life; if the stirring time in the solid premixing stage is too short (<10 min), the solid powder will not be completely mixed uniformly, resulting in poor structural uniformity of the functional current collector prepared.
[0072] If the rotation speed in the solvent dispersion stage is too high (>200 r / min), the slurry can produce bubbles, resulting in uneven dispersion, and the residual bubbles can cause the local conductivity of the functional current collector to deteriorate, and high shear force can damage the structure of the conductive agent carbon nanotubes, resulting in an increase in the porosity of the functional layer of the functional current collector prepared ultimately and a decrease in the mechanical strength; if the rotation speed in the solvent dispersion stage is too low (<150 r / min), the solid powder is prone to insufficient dispersion in the first solvent, resulting in agglomeration, making the conductive network of the functional current collector prepared ultimately sparse, the internal resistance increasing, and the adhesive being unevenly distributed, and the inter-particle bonding being weak.
[0073] If the stirring time in the solvent dispersion stage is too long (>25 min), the first solvent is prone to volatilization and causes the solid content of the slurry to increase, the viscosity of the slurry to be unstable, and further causes the liquid droplets to be unevenly formed during subsequent spray drying, the particle size distribution to be widened, and the performance of the functional current collector prepared ultimately to be deteriorated; if the stirring time in the solvent dispersion stage is too short (<15 min), the solid powder will not be completely dispersed and large particle agglomerates will exist, resulting in an increase in the structural defects of the functional layer of the functional current collector prepared, and a decrease in the performance of the functional current collector prepared ultimately.
[0074] If the rotating speed of the deep mixing stage is too high (> 350 r / min), the temperature of the slurry will rise, which may cause the solvent to volatilize more, the binder to gelify in advance, the viscosity of the slurry to abnormally rise, the subsequent atomization to be difficult, the surface pores of the composite particles to be blocked in the granulation process of the composite particles, and the electrolyte to be difficult to infiltrate.
[0075] If the stirring time of the deep mixing stage is too long (> 35 min), the molecular chain of the binder is broken, the adhesion performance is reduced, the inter-particle bonding force of the functional layer is weak, the functional layer is easy to fall off in the cycle process, and the internal resistance of the lithium ion battery using the functional current collector increases significantly with the increase of the cycle number; if the stirring time of the deep mixing stage is too short (< 25 min), the components in the slurry are difficult to mix fully or even have a concentration gradient, so that the consistency of the functional current collector prepared is poor.
[0076] Preferably, after the plasticizer is added to the mixed solution and stirred at a rotating speed of 250-350 r / min for 25-35 min, the obtained second mixed solution is further subjected to ball milling treatment, including the following steps: zirconia balls with particle sizes of 5 mm, 3 mm and 1 mm are matched in a volume ratio of (0-4):(0-4):(0-3) to obtain a ball milling group, the ball milling group and the second mixed solution are mixed in a mass ratio of (7-9):1, and then ball milling treatment is performed at a revolution speed of 300-400 r / min and a rotation speed of 400-500 r / min for 7-9 h to obtain a precursor slurry.
[0077] The zirconia balls with different particle sizes are matched to form a ball milling group for ball milling treatment of the second mixed solution, and the revolution speed, the rotation speed and the ball milling time are controlled within the above ranges, which can further refine the particles in the second mixed solution, enhance the dispersion degree of the materials, make the prepared precursor slurry more uniform and stable, and further improve the performance of the finally prepared functional current collector.
[0078] Preferably, in S3, the mass ratio of the second solvent in the coating slurry is 8-12%.
[0079] Preferably, in S3, the second solvent is N-methyl pyrrolidone (NMP).
[0080] In the preparation process of the coating slurry, the mass ratio of the second solvent NMP is controlled within the above range, which can improve the electrolyte resistance and mechanical strength of the prepared functional current collector.
[0081] If the mass percentage of NMP in the coating slurry is too high (> 12%), it will cause the porosity of the coated shell to increase after drying, and the electrolyte will seep in to cause the active material in it to dissolve, thereby reducing the mechanical strength of the functional current collector. If the mass percentage of NMP in the coating slurry is too low (< 10%), it will cause the viscosity of the coating slurry to increase, making subsequent atomization difficult, resulting in uneven thickness of the coated shell, and the inner core may not be covered in some local areas, thereby degrading the performance of the functional current collector.
[0082] Preferably, in S3, the coating slurry is prepared by the following steps: adding the oxide material to the second solvent and stirring at a speed of 200-300 r / min for 10-25 min, adding the coupling agent to the system and stirring at a speed of 200-300 r / min for 20-30 min, and ultrasonic treating the obtained dispersion under an ultrasonic frequency of 40-60 kHz and a power of 300-500 W to fully mix the dispersion, thereby preparing the coating slurry.
[0083] In the preparation process of the coating slurry, the oxide material is first added to the second solvent and stirred and mixed, and the stirring speed and time are controlled within the above range, then the coupling agent is added, and the stirring speed and time are controlled within the above range, and then the obtained dispersion is ultrasonic treated, and the ultrasonic frequency and power are controlled within the above range, which can fully mix the materials and form a stable coating slurry, thereby improving the performance of the prepared functional current collector.
[0084] Preferably, in S2, the conditions for spray drying are as follows: the hot gas inlet temperature is 230-270℃, the inlet gas flow rate is 1.3-1.7 m / s, and the outlet temperature is 80-90℃.
[0085] Preferably, in S4, the temperature for solidification and sintering is 180-200℃, and the time is 5-8 min. DETAILED DESCRIPTION
[0086] The technical features in the technical solutions provided by the present application will be further described clearly and completely in combination with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.
[0087] Example 1 A functional current collector includes a PET substrate and a functional layer disposed on both surfaces of the PET substrate, the functional layer containing composite particles, the composite particles including an inner core and a shell coated on the surface of the inner core, the average particle size of the inner core being 5 μm, and the thickness of the shell being 100 nm. The functional current collector provided by the embodiment is prepared by the following steps: S1. A double planetary mixer is selected, copper powder, carbon nanotubes, acetylene black, PVDF, and sodium polyacrylate are added to the stirring kettle and stirred at a speed of 100 r / min for 15 min to obtain a solid powder, NMP is added to the solid powder and stirred at a speed of 200 r / min for 20 min to obtain a first mixed solution, then dibutyl phthalate is added to the first mixed solution and stirred at a speed of 300 r / min for 30 min to obtain a second mixed solution, a ball mill group and the second mixed solution are added to a planetary ball mill in a mass ratio of 8:1 and subjected to ball milling treatment at a revolution speed of 350 r / min and a rotation speed of 450 r / min for 8 h to prepare a precursor slurry with a viscosity of 1200 mPa·s, a solid content of 70%, and a particle size D50=5 μm; The mass ratio of each component in the precursor slurry is as follows: copper powder 40%, carbon nanotubes 8%, acetylene black 7%, PVDF 15%, sodium polyacrylate 2%, dibutyl phthalate 3%, and NMP 25%; The ball mill group is composed of zirconia grinding balls with particle sizes of 5 mm, 3 mm, and 1 mm in a volume ratio of 3:4:3; S2. The precursor slurry is transported to the inlet of the centrifugal atomizer through a pipeline by a screw pump (the flow rate is controlled at 500 mL / min), under the action of centrifugal force, the precursor slurry is thrown out along the centrifugal disc to the surface of the PET substrate and dried in a drying tower (the residence time is 12 s) to form a functional layer on the surface of the PET substrate, and a semi-finished product is obtained; The hot gas inlet temperature of the drying tower is 250°C, the inlet gas flow rate is 1.5 m / s, and the outlet temperature is 85°C; S3. Titanium dioxide (TiO2) is added to NMP and stirred at a speed of 250 r / min for 20 min, silane coupling agent KH-560 is added to the system and stirred at a speed of 250 r / min for 25 min, and the obtained dispersion is subjected to ultrasonic treatment under the conditions of an ultrasonic frequency of 50 kHz and a power of 400 W to fully mix the dispersion, and a coating slurry is prepared; The mass ratio of each component in the coating slurry is as follows: TiO2 80%, KH-560 10%, and NMP 10%; S4. An auxiliary ultrasonic atomizer is installed at the bottom of the drying tower, the frequency of the ultrasonic atomizer is set to 2 MHz, and the power is 1.5 kW, the coating slurry is preheated at 65°C, and then the coating slurry is atomized to a coating liquid with a particle size of about 10 μm by the ultrasonic atomizer, and the coating liquid is reversely contacted with the functional layer of the semi-finished product in the drying tower to prepare a functional current collector. The inlet air temperature of the drying tower is 190℃, and the outlet air temperature is 75℃.
[0088] Example 2 A functional current collector includes a PET substrate and a functional layer disposed on both surfaces of the PET substrate, the functional layer containing composite particles, the composite particles including a core and a shell coated on the surface of the core, the average particle size of the core being 4 μm, and the thickness of the shell being 50 nm. The functional current collector provided in the example is prepared by the following steps: S1. A double planetary mixer is selected, copper powder, carbon nanotubes, acetylene black, PVDF, and sodium polyacrylate are added to the stirring kettle and stirred at a speed of 80 r / min for 20 min to obtain a solid powder, NMP is added to the solid powder and stirred at a speed of 150 r / min for 25 min to obtain a first mixed solution, then dibutyl phthalate is added to the first mixed solution and stirred at a speed of 250 r / min for 35 min to obtain a second mixed solution, a ball mill group and the second mixed solution are added to a planetary ball mill in a mass ratio of 6:1 and subjected to ball milling treatment at a revolution speed of 300 r / min and a rotation speed of 400 r / min for 6 h to prepare a precursor slurry with a viscosity of 1000 mPa·s, a solid content of 65%, and a particle size D50=4 μm; The mass ratio of each component in the precursor slurry is as follows: copper powder 35%, carbon nanotubes 10%, acetylene black 5%, PVDF 12%, sodium polyacrylate 3%, dibutyl phthalate 5%, and NMP 30%.
[0089] The ball mill group is compounded by zirconia grinding balls with particle sizes of 5 mm and 3 mm in a volume ratio of 6:1; S2. The precursor slurry is transported through a pipeline to the inlet of a centrifugal atomizer by a screw pump (the flow rate is controlled at 400 mL / min), under the action of centrifugal force, the precursor slurry is thrown out along the centrifugal disc to the surface of the PET substrate and after drying in the drying tower (the residence time is 10 s), a functional layer is formed on the surface of the PET substrate to obtain a semi-finished product; The inlet air temperature of the drying tower is 190℃, and the outlet air temperature is 75℃. S3. Alumina (Al2O3) is added to NMP and stirred at a speed of 250 r / min for 20 min, silane coupling agent KH-550 is added to the system and stirred at a speed of 250 r / min for 25 min, and the obtained dispersion is subjected to ultrasonic treatment under the conditions of an ultrasonic frequency of 50 kHz and a power of 400 W to fully mix the dispersion, to prepare a coating slurry; The mass ratio of each component in the coating slurry is as follows: Al2O3 70%, KH-550 20%, NMP 10%; S4. An auxiliary ultrasonic atomizer is installed at the bottom of the drying tower, the frequency of the ultrasonic atomizer is set to 1.5 MHz, the power is 1.5 kW, the coating slurry is preheated at 55℃, then the coating slurry is atomized into coating liquid with a particle size of about 10 μm by the ultrasonic atomizer, and the coating liquid is reversely contacted with the functional layer of the semi-finished product in the drying tower, to obtain the functional current collector; The inlet air temperature of the drying tower is 180℃, and the outlet air temperature is 75℃.
[0090] Example 3 A functional current collector includes a PET substrate and a functional layer arranged on both surfaces of the PET substrate, the functional layer contains composite particles, the composite particles include a core and a shell coated on the surface of the core, the average particle size of the core is 6 μm, and the thickness of the shell is 100 nm. The functional current collector provided in the embodiment is prepared by the following steps: S1. A double planetary mixer is selected, copper powder, carbon nanotubes, acetylene black, PVDF, and sodium polyacrylate are added to the stirring kettle and stirred at a speed of 120 r / min for 10 min to obtain a solid powder, NMP is added to the solid powder and stirred at a speed of 250 r / min for 15 min to obtain a first mixed solution, then dibutyl phthalate is added to the first mixed solution and stirred at a speed of 350 r / min for 25 min to obtain a second mixed solution, a ball mill group and the second mixed solution are added to a planetary ball mill in a mass ratio of 10:1 and subjected to ball milling treatment at a revolution speed of 400 r / min and a rotation speed of 500 r / min for 10 h to obtain a precursor slurry with a viscosity of 1500 mPa·s, a solid content of 75%, and a particle size D50=6 μm; The mass ratio of each component in the precursor slurry is as follows: copper powder 45%, carbon nanotubes 5%, acetylene black 10%, PVDF 18%, sodium polyacrylate 1%, dibutyl phthalate 1%, and NMP 20%; The ball mill group is compounded by zirconia grinding balls with particle sizes of 5 mm and 1 mm in a volume ratio of 2:1; S2. The precursor slurry is transported to the feed inlet of the centrifugal atomizer through the pipeline by a screw pump (the flow rate is controlled at 600 mL / min), the precursor slurry is thrown out to the surface of the PET substrate under the action of centrifugal force, and the functional layer is formed on the surface of the PET substrate after drying in the drying tower (the residence time is 15 s) to obtain a semi-finished product. The hot air inlet temperature of the drying tower is 270 DEG C, the air inlet speed is 1.8 m / s, and the air outlet temperature is 85 DEG C; S3. Silica (SiO2) is added to NMP and stirred at a speed of 250 r / min for 20 min, titanate coupling agent KH-560 is added to the system and stirred at a speed of 250 r / min for 25 min, and the obtained dispersion is ultrasonically treated under the conditions of an ultrasonic frequency of 50 kHz and a power of 400 W to fully mix the dispersion, thereby preparing a coating slurry; The mass ratio of each component in the coating slurry is as follows: SiO2 90%, titanate coupling agent 5%, and NMP 5%. S4. An auxiliary ultrasonic atomizer is installed at the bottom of the drying tower, the frequency of the ultrasonic atomizer is set to 2.5 MHz, and the power is 1.5 kW. The coating slurry is preheated at 75 DEG C, and then atomized by the ultrasonic atomizer to obtain coating liquid with a particle size of about 10 μm. The coating liquid is reversely contacted with the functional layer of the semi-finished product in the drying tower, thereby preparing a functional current collector. The air inlet temperature of the drying tower is 200 DEG C, and the air outlet temperature is 75 DEG C.
[0091] Example 4 A functional current collector includes a PET substrate and a functional layer arranged on both surfaces of the PET substrate, the functional layer contains composite particles, the composite particles include a core and a shell coated on the surface of the core, the average particle size of the core is 4.5 μm, and the thickness of the shell is 100 nm. The functional current collector provided in the embodiment is prepared by the following steps: S1. A double planetary mixer is selected, copper powder, carbon nanotubes, acetylene black, PVDF, and sodium polyacrylate are added to the stirring kettle and stirred at a speed of 90 r / min for 18 min to obtain a solid powder, NMP is added to the solid powder and stirred at a speed of 220 r / min for 18 min to obtain a first mixture, then dibutyl phthalate is added to the first mixture and stirred at a speed of 320 r / min for 28 min to obtain a second mixture, a ball milling group and the second mixture are added to a planetary ball mill in a mass ratio of 7:1 and subjected to ball milling treatment at a revolution speed of 330 r / min and a rotation speed of 420 r / min for 7 h, thereby preparing a precursor slurry with a viscosity of 1100 mPa·s, a solid content of 68%, and a particle size D50=4.5 μm. The mass ratio of each component in the precursor slurry is as follows: copper powder 30%, carbon nanotubes 3%, acetylene black 12%, PVDF 20%, sodium polyacrylate 4%, dibutyl phthalate 4%, and NMP 27%. The zirconium oxide grinding balls are compounded by 5 mm, 3 mm and 1 mm grinding balls in a volume ratio of 4:3:3; S2. The precursor slurry is transported into the feeding port of the centrifugal atomizer through the pipeline by using the screw pump (the flow rate is controlled at 500 mL / min), and the precursor slurry is flung out to the surface of the PET substrate under the centrifugal force and forms a functional layer on the surface of the PET substrate after drying (the residence time is 11 s) through the drying tower, to obtain a semi-finished product; The hot air inlet temperature of the drying tower is 240℃, the inlet air flow rate is 1.4 m / s, and the outlet air temperature is 85℃. S3. Zinc oxide (ZnO) is added into NMP and stirred at a speed of 250 r / min for 20 min, and an aluminic ester coupling agent is added into the system and stirred at a speed of 250 r / min for 25 min, and the obtained dispersion liquid is subjected to ultrasonic treatment under the condition of an ultrasonic frequency of 50 kHz and a power of 400 W to fully mix the dispersion liquid, to prepare a coating slurry; The mass proportion of each component in the precursor slurry is as follows: ZnO 60%, aluminic ester coupling agent 30%, and NMP 10%. S4. An auxiliary ultrasonic atomizer is installed at the bottom of the drying tower, the frequency of the ultrasonic atomizer is set to 2 MHz, and the power is 1.5 kW, the semi-finished product is preheated at 60℃, the coating slurry is atomized to a coating liquid with a particle size of about 10 μm by using the ultrasonic atomizer, and the coating liquid is reversely contacted with the functional layer of the semi-finished product in the drying tower, to prepare a functional current collector; The inlet air temperature of the drying tower is 170℃, and the outlet air temperature is 75℃.
[0092] Example 5 The difference between the functional current collector provided in the example and the functional current collector provided in Example 1 is that, in the preparation step S1 of the functional current collector, the precursor slurry does not contain sodium polyacrylate and dibutyl phthalate. The mass proportion of each component in the precursor slurry is as follows: copper powder 40%, carbon nanotube 10%, acetylene black 10%, PVDF 15%, and NMP 25%. Except for the above difference, the materials, formula ratio and preparation operation adopted in the example are strictly consistent with those in Example 1.
[0093] Example 6 The difference between the functional current collector provided in the example and the functional current collector provided in Example 1 is that, in the preparation step S1 of the functional current collector, an equal amount of sodium polyacrylate is used to replace dibutyl phthalate. Except for the above difference, the materials, formula ratio and preparation operation adopted in the example are strictly consistent with those in Example 1.
[0094] Example 7 This example provides a functional flocking fluid, which constitutes the difference compared with Example 1 that, in the preparation step S1 of the functional flocking fluid, an equal amount of dibutyl phthalate is used instead of sodium polyacrylate. Except for the above-mentioned difference, the materials, formula, and preparation operation adopted in this example are strictly consistent with those of Example 1.
[0095] Example 8 This example provides a functional flocking fluid, which constitutes the difference compared with Example 1 that, in the preparation step S1 of the functional flocking fluid, the mass proportion of each component in the precursor slurry is as follows: copper powder 40%, carbon nanotube 8%, acetylene black 7%, PVDF 15%, sodium polyacrylate 0.5%, dibutyl phthalate 4.5%, and NMP 25%.
[0096] Except for the above-mentioned difference, the materials, formula, and preparation operation adopted in this example are strictly consistent with those of Example 1.
[0097] Example 9 This example provides a functional flocking fluid, which constitutes the difference compared with Example 1 that, in the preparation step S1 of the functional flocking fluid, the mass proportion of each component in the precursor slurry is as follows: copper powder 40%, carbon nanotube 8%, acetylene black 7%, PVDF 15%, sodium polyacrylate 1%, dibutyl phthalate 6%, and NMP 23%.
[0098] Except for the above-mentioned difference, the materials, formula, and preparation operation adopted in this example are strictly consistent with those of Example 1.
[0099] Example 10 This example provides a functional flocking fluid, which constitutes the difference compared with Example 1 that: the average particle size of the core of the composite particle is 3 μm, and the shell thickness is 30 nm.
[0100] Except for the above-mentioned difference, the materials, formula, and preparation operation adopted in this example are strictly consistent with those of Example 1.
[0101] Example 11 This example provides a functional flocking fluid, which constitutes the difference compared with Example 1 that: the average particle size of the core of the composite particle is 7 μm, and the shell thickness is 250 nm.
[0102] Except for the above-mentioned difference, the materials, formula, and preparation operation adopted in this example are strictly consistent with those of Example 1.
[0103] In Embodiments 10-11, the average particle size of the core of the composite particles is controlled by adjusting one or more of the average particle size of each material in the precursor slurry, the particle size D50 of the precursor slurry, the solid content of the precursor slurry, and the parameters of the spray drying / ball milling process; the thickness of the shell of the composite particles is controlled by adjusting one or more of the average particle size of the oxide material in the coating slurry, the ratio of each material, and the parameters of the atomization / solidification process.
[0104] Embodiment 12 This embodiment provides a functional current collector, which differs from Embodiment 1 in that, in the preparation step S3 of the functional current collector, the mass ratio of each component in the coating slurry is as follows: TiO2 55%, KH-560 35%, NMP 10%.
[0105] Except for the above-mentioned differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those of Embodiment 1.
[0106] Embodiment 13 This embodiment provides a functional current collector, which differs from Embodiment 1 in that, in the preparation step S3 of the functional current collector, the mass ratio of each component in the coating slurry is as follows: TiO2 92%, KH-560 3%, NMP 5%.
[0107] Except for the above-mentioned differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those of Embodiment 1.
[0108] Embodiment 14 This embodiment provides a functional current collector, which differs from Embodiment 1 in that, in the preparation step S1 of the functional current collector, an equal amount of aluminum powder is used to replace the copper powder.
[0109] Except for the above-mentioned differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those of Embodiment 1.
[0110] Comparative Example 1 A functional current collector includes a PET substrate (thickness: 6 μm) and aluminum films (single-side aluminum film thickness: 1 μm) plated on both surfaces of the PET.
[0111] Comparative Example 2 This comparative example provides a functional current collector, which differs from Embodiment 1 in that, in the preparation step S1 of the functional current collector, the mass ratio of each component in the precursor slurry is as follows: copper powder 25%, carbon nanotubes 12%, acetylene black 14%, PVDF 15%, sodium polyacrylate 2%, dibutyl phthalate 3%, NMP 29%.
[0112] In addition to the above differences, the materials, formulation ratios and preparation operations used in the present comparative example are strictly consistent with those of Example 1.
[0113] Comparative Example 3 The present comparative example provides a functional current collector, which is different from Example 1 in that the mass ratios of the components in the precursor slurry in the preparation step S1 of the functional current collector are as follows: copper powder 50%, carbon nanotubes 2%, acetylene black 3%, PVDF 15%, sodium polyacrylate 2%, dibutyl phthalate 3%, and NMP 25%.
[0114] In addition to the above differences, the materials, formulation ratios and preparation operations used in the present comparative example are strictly consistent with those of Example 1.
[0115] Test Example 1. Test Subjects The present test example takes the functional current collectors prepared in Examples 1-14 and Comparative Examples 1-3 as test subjects to perform relevant performance tests.
[0116] 2. Test Contents (1) Volume Resistivity The volume resistivity of the functional current collector is tested according to the national standard GB / T 1410-2006 (four-probe method), and the specific test steps are as follows: a. Cut the functional current collector into a test sample with a size of 10 mm x 10 mm, and measure the thickness of the test sample 3 times and take the average value; b. Calibrate the BER2500 sheet resistance meter / four-probe meter, set the pressure to 5 MPa, and set the pressure holding time to 15 s; c. Place the test sample between the two electrodes, select the volume resistivity mode, and set the current to 10 -3 ~10 -1 A; d. Measure the resistance of the test sample 3 times, and calculate the average value of the volume resistivity according to p v =R v ×S / d, wherein p v represents the volume resistivity (Ω·cm), R v represents the resistance (Ω), S represents the area (cm 2 ), and d represents the thickness (cm).
[0117] (2) Longitudinal (MD) Tensile Strength and Elongation at Break The MD tensile strength and elongation at break of the functional current collector are tested according to the national standard GB / T 1040.3-2006.
[0118] (3) Corrosion resistance The salt spray test is performed on the functional fluid according to the national standard GB / T 10125-2021, and the time at which the functional fluid begins to corrode in the salt spray is recorded to characterize the corrosion resistance of the functional fluid. The specific test steps are as follows: a. The functional fluid is cut into a test sample with a size of 50 mm x 50 mm, weighed as m0, and the test sample is punched and hung; b. The salt spray chamber is equipped with a neutral salt spray (5% NaCl solution, pH 6.5-7.2), and the temperature is set to 35°C, the spray is 1-2 mL / (h·80 cm 2 ); c. The test sample is hung in the salt spray chamber (angle 15°-30°), and the spray is continuously sprayed for 240 h, and the test sample is observed every 48 h; d. After the test, the test sample is rinsed, dried, weighed as m1, and the corrosion area is used to assist in evaluating the corrosion degree of the functional fluid.
[0119] (4) Coating pull-off force The pull-off force of the coating (i.e., the functional layer) of the functional fluid is tested according to the national standard GB / T 5210-2006, and the pull-off force is used to characterize the bonding force between the functional layer and the substrate of the functional fluid. The specific test steps are as follows: a. The functional fluid is cut into a test sample with a size of 25 mm x 100 mm, and the functional layer is adhered to a metal pull-off block, which is cured at room temperature for 24 h; b. The XLW(PC)-500N pull-off machine is equipped with a pull-off clamp, which is calibrated and set to a speed of 10 mm / min; c. The maximum force is recorded when the functional layer and the substrate are separated vertically, and the average value is calculated as F=F_max / L (the fracture at the bonding site is invalid).
[0120] (5) Mass per unit area After measuring the area and mass of the functional fluid, the mass per unit area of the functional fluid is calculated according to the following formula: mass per unit area (g / m 2 )=mass (g) / area (m 2 ).
[0121] 3. Experimental results Table 1. Test results of the related properties of the functional fluid
[0122] The test results of the related properties of the functional fluid provided in Examples 1-14 and Comparative Examples 1-3 are shown in Table 1.
[0123] Compared with the conventional aluminum film current collector provided in Comparative Example 1, the volume resistivity of the functional current collector provided in Examples 1-14 is lower than that of Comparative Example 1, and the drawing force, MD tensile strength, elongation at break and corrosion resistance of the coating (i.e., the functional layer) in the functional current collector provided in Examples 1-14 are higher than those of Comparative Example 1, which is mainly because the functional current collector provided in Examples 1-14 sets the functional layer containing composite particles with a core-shell structure on the surface of the substrate, the inner core of the composite particles contains a metal material, a binder and a conductive agent, the outer shell contains an oxide material and a coupling agent, a continuous conductive network can be formed between the metal material and the conductive agent, the conductivity of the functional current collector is improved, the volume resistivity of the functional current collector is reduced, at the same time, the introduction of the binder in the inner core can enhance the adhesion between the component particles (metal material and conductive agent) in the inner core, ensure the structural stability and flexibility of the functional layer, and improve the mechanical strength of the functional current collector, and the oxide material and the coupling agent are used as the components of the outer shell, the oxide material can form a dense protective layer to improve the corrosion resistance of the functional current collector, and the coupling agent can efficiently modify the surface of the particles and effectively improve the chemical properties of the particle surface, and enhance the interfacial bonding force between the composite particles and between the composite particles and the substrate.
[0124] By comparing the data of Examples 1, 5, 6, 7, 8 and 9, it can be seen that the introduction of the dispersant and the plasticizer into the inner core of the composite particles and the control of the mass ratio of the two in the inner core within a certain range can make the functional current collector have good MD tensile strength and elongation at break at the same time.
[0125] The above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the above examples, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced by equivalents, and these modifications or replacements are within the protection scope of the present application.
Claims
1. A functional current collector, characterized in that: The functional current collector includes a substrate and a functional layer disposed on at least one surface of the substrate. The functional layer contains composite particles, and the composite particles include a core and a shell covering the surface of the core. The core contains metallic material, a binder, and a conductive agent. The metallic material accounts for 34-49% of the mass of the core, and the conductive agent accounts for 3.5-25% of the mass of the core. The outer shell contains oxide materials and coupling agents.
2. The functional current collector as described in claim 1, characterized in that: The metallic material includes one of copper powder and aluminum powder, and / or the binder includes at least one of polyvinylidene fluoride and styrene-butadiene rubber, and / or the conductive agent includes at least one of acetylene black, conductive carbon black, carbon nanotubes, and graphene, and / or the oxide material includes at least one of titanium dioxide, silicon dioxide, zirconium oxide, aluminum oxide, and zinc oxide, and / or the coupling agent includes at least one of silane coupling agent, aluminate coupling agent, and titanate coupling agent, and the silane coupling agent includes at least one of KH-560, KH-550, KH-561, KH-570, and KH-792.
3. The functional current collector as described in claim 2, characterized in that: The conductive agent includes acetylene black and carbon nanotubes, wherein the mass percentage of acetylene black in the core is 5.8-19%, and the mass percentage of carbon nanotubes in the core is 3.5-16%.
4. The functional current collector as described in claim 1, characterized in that: The core also contains additives, including dispersants and plasticizers, wherein the dispersant accounts for 1.1% to 6.5% of the mass of the core, and the plasticizer accounts for 1.1% to 8% of the mass of the core. The dispersant includes at least one of sodium polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, and sodium hexametaphosphate; The plasticizer includes at least one of dibutyl phthalate, dioctyl phthalate, tributyl phosphate, and dioctyl sebate.
5. The functional current collector as described in claim 1, characterized in that: The average particle size of the core is 4~6 μm, and the thickness of the shell is 50~200 nm.
6. The functional current collector as described in claim 1, characterized in that: The thickness of the functional layer is 5~50 μm.
7. A method for preparing a functional current collector, characterized in that, Includes the following steps: S1. Prepare a precursor slurry containing a metallic material, a binder, a conductive agent, and a first solvent, wherein the metallic material accounts for 30-45% of the mass of the precursor slurry, and the conductive agent accounts for 3-22% of the mass of the precursor slurry; S2. Spray drying is used to coat the precursor slurry onto at least one surface of the substrate to form a functional layer, thereby obtaining a semi-finished product; S3. The oxide material and coupling agent are uniformly dispersed in the second solvent to prepare the coated slurry; S4. The coating slurry is atomized and brought into contact with the functional layer of the semi-finished product, and then cured and sintered to obtain the functional current collector.
8. The method for preparing the functional current collector as described in claim 7, characterized in that: In step S1, the metal material is copper powder or aluminum powder, wherein the average particle size of the copper powder is 1~5 μm and the average particle size of the aluminum powder is 2~8 μm.
9. The method for preparing the functional current collector as described in claim 7, characterized in that: In S1, the conductive agent includes acetylene black and carbon nanotubes; The acetylene black accounts for 5-12% of the mass of the precursor slurry, and the particle size of the acetylene black is 30-50 nm. The carbon nanotubes account for 3-10% of the mass of the precursor slurry, and the length of the carbon nanotubes is 1-10 μm and the outer diameter is 10-100 nm.
10. The method for preparing the functional current collector as described in claim 7, characterized in that: In step S1, the particle size of the adhesive is 50~200 μm. And / or, In step S1, the binder accounts for 12-20% of the mass of the precursor slurry.
11. The method for preparing the functional current collector as described in claim 7, characterized in that: In step S1, the raw materials for preparing the precursor slurry also include additives, which include dispersants and plasticizers. The dispersant accounts for 1-4% of the mass of the precursor slurry, and the plasticizer accounts for 1-5% of the mass of the precursor slurry. The dispersant includes at least one of sodium polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, and sodium hexametaphosphate; The plasticizer includes at least one of dibutyl phthalate, dioctyl phthalate, tributyl phosphate, and dioctyl sebate.
12. The method for preparing the functional current collector as described in claim 7, characterized in that: In step S3, the oxide material accounts for 60-90% of the mass of the coating slurry, and the particle size of the oxide material is 50-200 nm. And / or, In step S3, the coupling agent accounts for 5-30% of the mass of the coated slurry.
13. The method for preparing the functional current collector as described in claim 7, characterized in that: In S1, the precursor slurry has a viscosity of 800-1500 mPa·s and a solid content of 65-75 wt%. And / or, In S3, the viscosity of the coating slurry is 300~500 mPa·s.
14. The method for preparing the functional current collector as described in claim 11, characterized in that, In step S1, the precursor slurry is prepared by the following steps: mixing the metal material, the binder, the conductive agent, and the dispersant, and stirring at 80-120 r / min for 10-20 min to obtain a solid powder; adding the first solvent to the solid powder and stirring at 150-200 r / min for 15-25 min to obtain a first mixture; then adding the plasticizer to the first mixture and stirring at 250-350 r / min for 25-35 min to obtain the precursor slurry.
15. The method for preparing the functional current collector as described in claim 14, characterized in that, After adding the plasticizer to the mixture and stirring at 250-350 r / min for 25-35 min, the process further includes ball milling the obtained second mixture as follows: Zirconia grinding balls with particle sizes of 5 mm, 3 mm, and 1 mm are mixed in a volume ratio of (0-4):(0-4):(0-3) to obtain a grinding ball group. The grinding ball group is mixed with the second mixture in a mass ratio of (7-9):1 and then ball milled at an orbital speed of 300-400 r / min and a rotational speed of 400-500 r / min for 7-9 h to obtain the precursor slurry.
16. The method for preparing the functional current collector as described in claim 7, characterized in that, In step S3, the coating slurry is prepared by the following steps: adding the oxide material to the second solvent and stirring at 200-300 r / min for 10-25 min; adding the coupling agent to the system and stirring at 200-300 r / min for 20-30 min; and subjecting the resulting dispersion to ultrasonic treatment at an ultrasonic frequency of 40-60 kHz and a power of 300-500 W to ensure that the dispersion is fully mixed, thereby obtaining the coating slurry.
17. The method for preparing the functional current collector as described in claim 7, characterized in that, In step S2, the spray drying conditions are as follows: hot air inlet temperature is 230~270℃, inlet air velocity is 1.3~1.7 m / s, and outlet air temperature is 80~90℃. And / or, In S4, the curing and sintering temperature is 180~200℃ and the time is 5~8 min.