Process for the metallization of electrochemically active powders

Abstract

Materials and methods for coating electrochemically active electrode materials for lithium ion batteries are provided. In one embodiment, an electrochemically active electrode material includes a polymeric coating applied directly to an outer surface of the electrochemically active electrode material; a metal electroplating catalyst adhered to the continuous polymer; and a continuous metal coating that completely covers the metal catalyst and the continuous polymeric coating. The electrochemically active electrode material can comprise a powder containing one or more secondary particles, and the polymeric and metal coatings can be applied to the outer surface of these secondary particles.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 62 / 553,067, filed August 31, 2017, entitled "Process for Metallization of Electrochemically Active Powders". The entire contents of the above-listed application are incorporated herein by reference for all purposes. Technical Field

[0003] This application generally relates to systems and methods for coating electrochemically active powders that form electrodes for electrochemical energy storage devices such as lithium-ion batteries. Background Technology

[0004] A rechargeable battery is an electrochemical energy storage device capable of repeatedly storing and releasing large amounts of electrical energy through the reversible conversion between electrical energy and chemical potential energy. Due to the growing demand from the energy industry and other consumers for batteries with higher energy density, the rechargeable battery industry has shifted towards primarily using lithium-ion batteries. Lithium is one of the most attractive elements for introduction into electrochemical energy storage devices requiring high energy density because it is the lightest and most positively charged metal.

[0005] A typical lithium-ion battery cell includes a positive electrode (cathode), a negative electrode (anode), an ionic electrolyte solution that supports the movement of lithium ions between the two electrodes, and a porous separator that keeps the anode and cathode electrically isolated. Lithium-ion batteries can repeatedly store and release electrical energy through reversible electrochemical reduction and oxidation reactions that occur in the electrochemically active materials incorporated into the positive and negative electrodes. For example, during discharge, lithium ions move from the anode to the cathode through the electrolyte to generate an electric current. Transition metal oxides and phosphates are commonly used as electrochemically active materials in the positive electrode (cathode), while various types of carbon are commonly used as electrochemically active materials in the negative electrode (anode). Such electrochemically active electrode materials are typically used in the form of fine powders, which are applied to a current collector using binders and conductive additives to allow for a high interfacial area for electrochemical reactions and to facilitate lithium-ion transport.

[0006] During the charging and discharging of lithium-ion batteries, electrochemical reactions occur at the interface between the electrolyte and the electrochemically active electrode materials. Specifically, lithium ions move between the active electrode materials and the electrolyte. However, these electrochemically active electrode materials can also catalyze the decomposition of the electrolyte when directly exposed, leading to a decrease in the electrochemical cycling performance of the battery cell and a reduction in coulombic efficiency (discharge capacity divided by charge capacity over a given charge / discharge cycle). Furthermore, the decomposition of organic electrolytes and the subsequent gas generation lower the flash point of the electrolyte, reducing battery safety and increasing the risk of fire.

[0007] Therefore, the surface of electrochemically active electrode materials can be modified, for example, by applying a coating, to prevent or minimize undesirable parasitic side reactions between the active material and the electrolyte, and to improve the cycle life of the battery. Thus, the performance of active electrode materials can be improved by advantageously altering their surface properties without significantly affecting their volumetric properties (energy storage capacity). To minimize the impact on the favorable volumetric properties (especially energy storage capacity) of the original material, such surface modification is preferably as thin as possible while also sufficiently modifying the surface properties. This type of surface modification involves coating the electrochemically active electrode material with a thin, continuous layer of metal or alloy (“powder metallization”) so that the surface properties of the composite material are very similar to those of the alloy or metal coating, and the volumetric properties are very similar to those of the original powder.

[0008] The metal coating on an electrochemically active electrode material can be either electrochemically active or inactive at the potential required for energy storage. Coating the active material with an electrochemically inactive metal can lead to higher conductivity and lower charge transfer resistance, resulting in faster charge and discharge rates. However, depositing an electrochemically inactive metal can significantly reduce the specific capacity of the electrode material.

[0009] On the other hand, coating with electrochemically active metals can lead to: solvent co-intercalation resistance, higher electronic conductivity, lower charge transfer impedance, better cycle life, and higher intercalation capacity. Therefore, the energy density of lithium-ion batteries can be improved by coating active materials with another electrochemically active metal that has higher energy storage capacity. For example, JaeWoo Kim et al. disclosed that silicon powder coated with copper via electrodeposition (ELD) resulted in better cycle life, electronic conductivity, and coulombic efficiency compared to pure silicon powder when used as an anode material in lithium-ion batteries. Gao et al. disclosed that graphite powder coated with copper via ELD exhibited higher solvent co-intercalation resistance than pure graphite when used as an anode material in lithium-ion batteries.

[0010] Several different methods exist for depositing thin metal films (<1µm thick) on metals such as electrochemically active electrode materials. For example, physical vapor deposition (PVD) can produce nanometer-thick films for most metals; however, it is a line-of-sight technique, making it extremely difficult to coat uneven and non-uniform surfaces. Chemical vapor deposition (CVD), on the other hand, can also produce metal coatings of similar thickness to PVD and is less limited by line-of-sight. However, both PVD and CVD require expensive high-vacuum equipment with low throughput, making them economically infeasible for large-scale production of metallization powders.

[0011] Another method for depositing metal films onto a substrate is by electrodeposition from a metal ion solution, where an external power source provides the electrons to reduce the metal ions onto the substrate surface. Traditional electrochemical deposition requires electrical contact between the working electrode (the substrate being plated) and the counter electrode; otherwise, no current flows through the substrate, and no metal is deposited on it. Maintaining constant electrical contact with each particle of a fine powder while ensuring the powder surface is not blocked is impractical; therefore, traditional electrochemical deposition is not a commercially viable method for powder metallization.

[0012] The most widely used metal coating method is electrodeposition (“ELD”), in which an aqueous reducing agent is autocatalytically oxidized on the metal surface, providing an electron source that does not require electrical contact. These electrons conduct electricity through the metal, subsequently reducing solvated metal ions to their metallic form on the surface of the metal deposit, resulting in its thickness growth. An ELD plating bath must include a soluble metal salt providing the metal ion source, a reducing agent capable of autocatalytic oxidation on the metal surface, and a complexing agent to prevent spontaneous decomposition of the plating bath. To initiate ELD on surfaces lacking the catalytic activity for oxidation by a suitable reducing agent, a seed layer of a highly catalytically active metal (referred to herein as a “catalyst”) must first be applied.

[0013] Catalysts are typically layers of discontinuous but substantially tightly packed metal nanoparticles with diameters less than approximately 10 nm. Due to the ELD reaction and metal deposition on the catalyst particles, hemispherical metal islands form on the substrate, gradually increasing in size until adjacent islands merge to form a continuous metal film. The minimum thickness required to obtain a continuous film is the average thickness (total volume / total area) of all the metal islands merging together to form a dense layer. To achieve a low minimum thickness (<150 μm), the diameter of the catalyst particles must be minimized to maximize their surface area density (particle number / area). Ensuring excellent adhesion between the catalyst particles and the substrate (electrochemically active electrode material) is also crucial, as areas where the catalyst particles detach from the electrode material will not be coated with metal.

[0014] Catalyst particles are typically composed of noble metals (PMs) such as palladium, platinum, rhodium, gold, or silver. PMs are used because they exhibit high catalytic activity for the oxidation of most common aqueous reducing agents and readily decrease from a cationic state to an elemental state. In conventional ELD catalyst processes, PM nanoparticles are applied to the substrate surface in one of two ways. In the first method, PM cations are adsorbed onto the substrate surface by immersion in an aqueous solution of a PM salt, typically including a complexing agent. The substrate is then treated with an aqueous reducing agent to nucleate the PM nanoparticles on the surface. In the second method, a PM salt and a reducing agent are typically premixed with a dispersant to form a colloid of PM nanoparticles. The substrate is then treated with the colloid, relying on the physical adhesion of the PM nanoparticles to the substrate surface. Although the use of PM catalysts for ELD on large substrates, particularly in the semiconductor industry, has been extensively studied, research on their use in fine powder metallization is limited. Therefore, the aforementioned conventional metallization processes typically involve developing PM catalysts for use on relatively smooth and uniform surfaces in an environment where the process can be precisely controlled. And due to their high cost, the amount of PM catalyst used is usually small to keep product costs relatively low.

[0015] However, the inventors of this paper have recognized the potential problems of applying the aforementioned metallization methods for large substrates to metallizing fine powders. For example, this ELD metallization process is expensive when used on electrochemically active electrode powders. Because the specific surface area of ​​fine electrochemically active electrode powders is much larger (more than 1000 times) than that of typical large substrates used in conventional ELD metallization processes, up to 1000 times more PM catalysts must be used to catalyze the surface. As mentioned above, PM catalysts include expensive materials, such as palladium, thus significantly increasing the cost of coating electrode powders with PM catalysts using ELD methods.

[0016] For example, this metallization process is not entirely effective in continuously coating the substrate when used on fine electrode powders. Therefore, the coating may not be effective in preventing the active material from decomposing into the electrolyte. In particular, ensuring a sufficiently dense and uniform catalyst layer capable of producing a continuous metal film is more challenging due to the inherently higher surface irregularities of most fine powders compared to conventional large and smooth ELD substrates, and the high shear stresses involved in many powder processing techniques. Therefore, when powder is used as a substrate, the aforementioned method of adhering the catalyst to the substrate is significantly less effective in adhering the catalyst. Because the aforementioned metallization method produces a lower catalyst areal density on the powder compared to conventional large substrates, the resulting metal coating is often discontinuous and / or non-uniform, thus still exposing some of the active electrode material powder to the electrolyte. Therefore, conventional metallization methods still allow electrolyte decomposition reactions to occur on the surface of the electrochemically active material, thereby reducing its performance.

[0017] While some methods exist for powder metallization using ELD, most of these are applied to non-conductive powders for use in conductive inks, adhesives, etc. For example, Oyamada et al. disclosed a method for producing a substantially continuous nickel coating on fine powders for use as a conductive additive. Specifically, Oyamada employed a catalytic process to adsorb palladium ions onto the surface of powders (which can be pretreated to increase adsorption), followed by treatment with an aqueous reducing agent to nucleate palladium nanoparticles on the surface. Alexander et al. disclosed a similar method for coating silicate particles with PM for use in composite castings. Gao et al. and Shukla et al. also demonstrated similar methods in which copper metal was deposited on graphite and fly ash powders, respectively.

[0018] The inventors of this paper have recognized the potential problems of the aforementioned ELD powder metallization method when applied to electrochemically active materials. For example, because PM catalysts do not adhere to electrochemically active materials as well as they do to conventional inert powders in some prior art, they are again affected by the low areal density on the surface of the electrochemically active electrode material, resulting in discontinuous metal coatings. More specifically, the adhesion of the ELD catalyst to the substrate must be excellent to achieve a fully continuous, uniform metal coating with the smallest possible thickness. If the ELD catalyst does not adhere sufficiently to the substrate and does not have a sufficiently high areal density, the uniformity and continuity of the resulting metal coating will be compromised, as the deposition of metal on the substrate depends on the presence of the ELD catalyst on the substrate surface. Therefore, the catalyst layer ideally nucleates into a uniform, closely packed structure, and any catalyst particles detaching from the substrate will result in a discontinuous coating. Any sensitivity of the process (to the surface properties of the substrate or processing conditions) can lead to poor catalyst adhesion.

[0019] Noble metal ELD catalysts tend to adhere less well to electrochemically active electrode powders compared to their conventional ELD substrate counterparts and are often more sensitive to the surface properties of the material. In particular, the surface properties of conventional ELD substrates can be controlled more precisely compared to electrochemically active electrode powders. Since electrochemically active electrode materials in lithium-ion batteries are often poor adsorbents for PM ions, pretreatment may be necessary to enhance the surface functionalization of PM-trapping groups. Relying on surface functionalization to improve PM adsorption can lead to several complications, including making the process more sensitive to impurities on the material surface. This, in turn, may require the use of higher purity and more expensive raw materials. Furthermore, many surface modification techniques that can improve PM adsorption may be incompatible with the electrochemically active materials of lithium-ion batteries. Different pretreatment methods may be required for each material or material class, making the development and scaling up of processes for multiple materials more difficult and costly.

[0020] Furthermore, the high shear stress introduced during electrode material processing can cause catalyst particles to detach from the electrochemically active electrode material. This is due to the fact that the reduction reaction that forms the metal nanoparticles occurs at the substrate-liquid interface, and that the adhesion of these nanoparticles is primarily due to electrostatic interactions. If a colloidal catalyst process is employed, the adhesion force is entirely attributed to electrostatic interactions. Therefore, the adhesion force of nanoparticles is sensitive to the surface chemistry of the material, the composition of the catalyst and electroplating bath (especially ionic strength and pH), and the mechanical stress generated during material processing. Oyamada et al. reported that when using conventional PM ELD catalysts, the surface area of ​​the powder in the ELD electroplating bath must be kept below 10 m². 2 / L (equivalent to approximately 10 g / L for typical lithium-ion active materials). Using such a low solids loading would require larger equipment to achieve the desired production volume, and would also increase waste.

[0021] Several methods employing ELD processes without a catalyst step have been demonstrated. For example, Palaniappa et al. disclosed a method for depositing a discontinuous nickel coating on graphite powder using a thermal activation process without a PM catalyst, and Jae Woo Kim et al. reported a method for depositing a mostly continuous copper metal layer on a silicon powder surface after etching with hydrofluoric acid. However, both of these ELD processes result in poor performance due to the discontinuous coating.

[0022] Some methods for powder metallization have completely abandoned ELD. Li et al. demonstrated different methods for ELD catalysts in which a polyimide film was impregnated with silver ions and then heated in air to thermally reduce the silver and nucleate catalyst particles on the polyimide surface. Dow et al. reported a similar method using copper instead of silver impregnation and an aqueous reducing agent to nucleate catalytic copper nanoparticles on the surface. Theoretically, similar methods could also be used for ELD catalysts if a continuous polyimide layer could be applied to fine powder, although this has not yet been translated into practice.

[0023] Rowe demonstrated a method for coating polymers onto fine powders using a solvent-based process in which powder is dispersed in an organic solvent containing the polymer to be coated, and a non-solvent is slowly added to precipitate the polymer onto the powder surface. Smith-Johannsen et al. disclosed the use of a high-temperature hydrodynamic milling machine to coat polymers onto fine powders by evaporating organic solvents from a polymer solution.

[0024] However, the inventors of this paper have recognized the potential problems with the aforementioned polymer coating and metallization methods. For example, the methods disclosed by Palaniappa et al. and Jae Woo Kim et al. do not provide continuous and / or uniform coatings, resulting in electrolyte degradation by the active electrode material and hindering further improvement in battery cycle life when applied to battery applications. Similarly, the methods described in the prior art for coating polymers onto fine powders are not feasible for coating polyimide-type polymers onto lithium-ion battery active materials. For example, Rowe's solvent / non-solvent-based process relies on the use of mineral silicates to prevent the polymer-coated powder from agglomerating. Any particles adhering to the polyimide surface can lead to discontinuous final metal coatings because they cover catalyst particles nucleated from the polyimide. Furthermore, metal oxides including silicates can be electrochemically active inside lithium-ion batteries and can significantly reduce the battery's initial cycle coulombic efficiency. The high-temperature fluid energy milling process disclosed by Smith-Johannsen et al. is also problematic because the polymer must be melted to flow over the surface of the powder and uniformly coat it. When poly(amic acid) polymers exceed their glass transition temperature and become flowable, they undergo a rapid chemical reaction to form brittle polyimides that do not flow until higher temperatures. Additionally, the polyimides will need to be converted back to their poly(amic acid) form via alkaline hydrolysis to regain their PM-trapping capabilities, and this process may dissolve the polymer coating from the substrate. Both processes require significant solvent usage. Solvents suitable for dissolving poly(amic acid), such as N-methylpyrrolidone, are generally hazardous and lead to increased safety risks and waste disposal costs compared to primarily water-based polymer coating processes.

[0025] The inventors of this paper have recognized that PM catalysts adhere more firmly to electrochemically active electrode powders when a polymer coating is applied to the powder. Therefore, the aforementioned problem can be addressed at least in part by an electrochemically active electrode material comprising: a continuous polymer coating directly coupled to the outer surface of the electrochemically active electrode material; a metal catalyst adhered to the continuous polymer coating for catalyzing an electrodeposition-free (ELD) reaction; and a continuous metal coating completely covering the metal catalyst and the continuous polymer coating. The metal catalyst can adhere more strongly to the polymer than the electrochemically active electrode material itself. Therefore, when the outer surface of the active electrode material includes a continuous polymer coating, the metal catalyst can occupy the outer surface of the electrochemically active electrode material more densely compared to when the outer surface of the active electrode material is bare and uncoated with polymer. In this way, a thinner, more continuous, uniform, and consistent conductive metal coating can be applied to the active electrode material during the subsequent ELD reaction.

[0026] For example, the above problems can be solved at least in part by coated electrochemically active electrode powder, which includes: electrochemically active electrode powder particles; a polymer directly coated onto the outer surface of the electrochemically active electrode powder particles; a metal catalyst coupled to the polymer for catalyzing an electrodeposition-free (ELD) reaction; and a continuous metal coating that completely covers the metal catalyst and the polymer.

[0027] In another embodiment, the above-mentioned problem can be solved at least in part by a method for metallizing powder particles of electrochemically active electrode material, the method comprising: coating the outer surface of the powder particles with a continuous polymer layer; annealing / applying a catalyst for an electrodeposition (ELD) reaction onto the polymer; and depositing a continuous metal layer on the catalyst and the polymer by an electrodeposition process.

[0028] Therefore, by applying a polymer coating to the electrochemically active electrode material, the adhesion of the metal electroplating catalyst to the fine electrochemically active electrode powder can be improved, thereby increasing the areal density of the metal electroplating catalyst on the electrochemically active electrode powder. This leads to a significant reduction in the sensitivity of the ELD process, thus simplifying the development and production of new composite materials. Furthermore, the metal coating is a completely continuous metal coating, exhibiting a sufficiently low thickness (<150 nm) and a uniform surface morphology. Due to the more continuous and uniform coating, and because such a thin metal conductive coating can be manufactured (due to the higher areal density of the metal catalyst) while maintaining a continuous and uniform surface morphology, the charge-discharge performance of batteries containing electrochemically active materials with these coatings can be improved. Moreover, because the metal catalyst adheres more to the electrochemically active material when the polymer coating is applied first, less metal catalyst may be needed, thus reducing the cost of producing such metal-coated electrochemically active powders.

[0029] It will be understood that the above overview is provided to present a simplified version of the selected concepts further described in the detailed embodiments. This is not intended to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims appended to the detailed embodiments. Furthermore, the claimed subject matter is not limited to implementations that address any of the shortcomings pointed out above or in any part of this disclosure. Attached Figure Description

[0030] Figure 1A A schematic diagram of an example method for manufacturing a lithium-ion battery according to at least one embodiment of the present invention is shown, wherein the lithium-ion battery comprises an electrochemically active electrode material coated with a polymer and a metal.

[0031] Figure 1B A schematic diagram of an example method for manufacturing a lithium-ion battery according to at least one embodiment of the present invention is shown, wherein the lithium-ion battery comprises an electrochemically active electrode material coated with a crosslinkable polymer and a metal.

[0032] Figure 2 This invention illustrates at least one embodiment of the present invention, which involves applying a polymer coating to an electrochemically active electrode material before depositing a metal coating onto the electrode material, enabling the battery to, for example, [achieve this effect]. Figure 1A and / or Figure 1B A flowchart illustrating an example method for metallizing electrochemically active electrode materials for lithium-ion batteries.

[0033] Figure 3 A flowchart of an example method for coating electrochemically active electrode materials with polymers according to at least one embodiment of the present invention is shown.

[0034] Figure 4AA flowchart illustrating an example method for applying a metal catalyst for an ELD reaction to a polymer coating of an electrochemically active electrode material, according to at least one embodiment of the present invention, is shown.

[0035] Figure 4B A flowchart illustrating an example method for applying a metal catalyst for an ELD reaction to a crosslinkable polymer coating of an electrochemically active electrode material, according to at least one embodiment of the present invention, is shown.

[0036] Figure 5 A flowchart of an example method for coating electrochemically active electrode materials with metal via an ELD is shown according to at least one embodiment of the present invention.

[0037] Figure 6A A scanning electron microscope (SEM) image of an example electrochemically active electrode material sample comprising a plurality of uncoated secondary particles according to at least one embodiment of the present invention is shown.

[0038] Figure 6B The image shows a scanning electron microscope (SEM) image of an example electrochemically active electrode material sample containing multiple secondary particles of an electrochemically active electrode material sample that has been coated with metal but not yet coated with polymer.

[0039] Figure 6C The image shows a scanning electron microscope (SEM) image of an example electrochemically active electrode material sample containing multiple secondary particles of an electrochemically active electrode material sample coated with metal and polymer according to one or more embodiments of the present invention, without the addition of one or more additives.

[0040] Figure 6D At least one embodiment according to the present invention is shown. Figure 6C A more magnified version of the SEM image shows the metal coating on the secondary particles of an example electrochemically active electrode material sample.

[0041] Figure 6E The image shows a scanning electron microscope (SEM) image of an example electrochemically active electrode material sample comprising multiple secondary particles of an electrochemically active electrode material sample coated with a continuous metal coating and a polymer according to one or more embodiments of the present invention, without the addition of one or more additives.

[0042] Figure 6F At least one embodiment according to the present invention is shown. Figure 6D A more magnified version of the SEM image shows a continuous metal coating on the secondary particles of an example electrochemically active electrode material sample.

[0043] Figure 7A schematic cross-sectional view of an example secondary particle of an electrochemically active electrode material coated with polymers and metals using at least one coating method described according to the present invention is shown.

[0044] Figure 8 A graph showing example test data comparing the retention capacity of a lithium-ion battery comprising an electrode manufactured according to at least one embodiment of the present invention relative to a lithium-ion battery comprising an uncoated electrode measured at different C rates, wherein the electrode comprises an electrochemically active material coated with a polymer and a metal. Detailed Implementation

[0045] This invention relates to materials and methods for coating electrochemically active electrode materials, such as anodic graphite, with polymers that adhere more readily to metal plating catalysts (e.g., metal catalysts for ELD reactions) than the electrochemically active electrode materials themselves. By coating the active electrode material with a polymer, less metal plating catalyst may be required for the metal plating reaction, and a greater amount of catalyst can adhere to the active electrode material, resulting in a thinner, more continuous, and / or more uniform metal coating on the electrochemically active electrode material when the reaction (e.g., ELD reaction) is carried out.

[0046] like Figure 1A and 1B As shown in the embodiments, the lithium-ion battery includes electrodes, namely a negative electrode (anode) and a positive electrode (cathode). The electrodes are made of electrochemically active materials. For example, the anode can be made of graphite, and the cathode can be made of a high-nickel active cathode material such as lithium nickel manganese cobalt oxide (LiNi). x Mn y Co 1-x-y Composed of O2 or NMC.

[0047] Electrochemically active electrode materials can be in powder form and can include porous secondary particles, as illustrated in the example SEM image of a graphitic mesophase carbon microsphere (MCMB) sample. Figure 2 As described in the example metallization method, an active electrode material can be coated with a polymer, and a catalyst for an ELD reaction can be applied to the polymer coating. This ELD catalyst can then be used to catalyze an ELD reaction that deposits a metal coating onto the polymer coating. Figure 3 An example method for coating a polymer onto an active electrode material is shown. The polymer can include many different compounds. Figure 1A , 1B 4A and 4B illustrate various methods for applying catalysts to different types of polymer coatings. Once the polymer and catalyst are applied to the active electrode material, metals can be coated onto the active electrode material using an ELD reaction, such as... Figure 5 As described in the example methods.

[0048] Through experiments and tests, compared with other metal-coated active electrode materials that do not include a polymer layer and rely on nucleation reactions of noble metal catalysts on the substrate surface, metal-coated active electrode materials including polymer intermediates exhibit a more continuous and / or uniform metal coating, while also possessing greater capacity retention. For example, Figure 6B-6F SEM images illustrating a more continuous and uniform active electrode material with a polymer-coated metal coating and an active electrode material without a polymer coating are shown. Furthermore, Figure 8 Example test results are shown, reporting that battery cells with polymer-coated active electrode materials retain significantly greater capacity at higher C rates than those with other active electrode materials. Furthermore, the coating thickness can be kept sufficiently low (e.g., <150 nm) to avoid negatively impacting the volumetric capacity of the battery cell.

[0049] Therefore, the performance of a battery cell can be improved by more completely and uniformly covering the electrode active material with a conductive metal that promotes lithium-ion transport. Specifically, by more continuously and uniformly covering the electrode active material with a conductive metal such as copper, a higher high-rate discharge capability can be achieved. Furthermore, since a relatively thin coating can be maintained, a higher high-rate discharge capability can be obtained without sacrificing the volumetric capacity of the battery cell. In particular, because the catalyst can adhere to the polymer more easily than the electrochemically active electrode material itself, the planar density of the catalyst on the surface of the active electrode material can be increased. Because the planar density of the catalyst can be increased, the amount of metal coating required to fill the gaps between adjacent catalyst islands is reduced, thus reducing the thickness of the metal coating required to form a completely continuous coating.

[0050] Furthermore, polymer-coated electrode materials can improve the safety of battery cells containing polymer-coated electrode materials because they allow for a more continuous and / or uniform application of the metal coating to the secondary particles of the active material powder. By more completely covering the active electrode material with a metal film, the interaction between the active electrode material and the electrolyte can be minimized, thereby minimizing the decomposition of the active electrode material by the electrolyte and thus improving the flash point of the battery cell.

[0051] For clarity and continuity, it should be understood that multiple different names may be used in the following description to refer to the same concept, idea, or item, and vice versa. For example, it should be understood that “active electrode material” may be used herein to refer to all electrochemically active electrode powders used in lithium-ion batteries, including but not limited to graphite, graphite mesophase carbon microspheres (MCMB), LiCoO2, LiMn2O4 and LiFePO4, lithium nickel manganese cobalt oxide (NMC), etc.

[0052] Furthermore, although this invention primarily relates to electrochemically active materials for metal plating via ELD reaction, it should be understood that other metal plating techniques may also be used without departing from the scope of this invention. Correspondingly, although this invention primarily relates to suitable catalysts for ELD reactions, such as noble metals, it should be understood that other catalysts may also be used without departing from the scope of this invention. For example, one or more of the platinum group metals (platinum, palladium, ruthenium, rhodium, iridium, rhenium) and gold and silver can be used as catalysts in any one or more of the aforementioned metal plating techniques. Additionally, any metal that can be used for ELD plating can be used as a catalyst, such as copper, nickel, cobalt, iron, etc.

[0053] Furthermore, numerous specific details are set forth in the following description to provide a thorough understanding of the proposed concepts. The proposed concepts can be practiced without some or all of these specific details. In other cases, well-known process operations have not been described in detail to avoid unnecessarily obscuring the described concepts. Although some concepts will be described in conjunction with specific embodiments, it should be understood that these embodiments are not intended to be limiting.

[0054] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a” and “described” are intended to include the plural forms, including “at least one,” unless otherwise clearly indicated in the content. “Or” means “and / or.” As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. It will be further understood that when the terms “comprising” and / or “containing” are used in this specification, they indicate the presence of the stated features, areas, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, areas, integers, steps, operations, elements, components, and / or groups thereof. The terms “or combinations thereof” or “mixtures thereof” refer to combinations including at least one of the foregoing elements.

[0055] Unless otherwise defined, all terms (including technical terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will also be understood that terms such as those defined in common dictionaries should be interpreted as having the same meaning as they have in the relevant field and in the context of this invention, and will not be interpreted in an idealized or overly formal manner unless expressly defined herein.

[0056] Turning Figure 1A and 1B It illustrates schematic diagrams of different example processes for manufacturing electrodes for lithium-ion batteries, wherein the lithium-ion battery comprises an electrochemically active material having a layered coating of polymer and conductive metal. Specifically, Figure 1AAn example method for manufacturing lithium-ion batteries is shown, wherein the polymer of the coating of the active material comprises a non-crosslinkable polymer, while Figure 1B A similar method is shown, but for the polymer, it is crosslinkable. Figure 1A and 1B The differences between the two processes described in the text will be explained below relative to... Figure 4A and 4B To elaborate further.

[0057] focus on Figure 1A The illustration shows a schematic diagram 100 of an example method for manufacturing a lithium-ion battery comprising an electrochemically active material, wherein the electrochemically active material comprises a conductive metal coating over a coating of a non-crosslinkable polymer. The electrochemically active electrode material 102 may first be mixed with a solution comprising a non-crosslinkable polymer (e.g., an alkalipolyamate solution 103).

[0058] In a preferred embodiment, the active electrode material 102 may include an electrochemically active material for the anode. For example, the active electrode material 102 may include graphite and / or graphite MCMB, other forms of carbon such as hard carbon, or elements capable of forming alloys with lithium (such as silicon, tin, antimony, or compounds thereof). However, in other embodiments, the active electrode material 102 may include an electrochemically active material for the cathode, such as LiCoO2, LiMn2O4 and LiFePO4, lithium nickel manganese cobalt oxide (NMC), etc.

[0059] The polyamate alkaline solution 103 may include an aromatic polyimide (e.g., lithium polyamate salt) dissolved in a solvent (e.g., water). Therefore, the polyamate alkaline solution 103 can be prepared by first synthesizing a polymer such as an aromatic poly(amic acid) and then dissolving the synthesized polymer in a solvent. The polymer in solution 103 that is highly soluble in the solvent (e.g., water) of solution 103 may have a relatively low molecular weight (<100 kDa), may include a chemical structure with a high energy barrier to rotate around the main chain, may have a basic ability to chelate noble metal (PM) ions, may be able to reduce chelated PM ions to metal nanoparticles by low-temperature heat treatment, preferably in an air atmosphere, may be completely insoluble in water after heat treatment, and may have high electronic and ionic conductivity when used as a component in a lithium-ion battery.

[0060] Therefore, the polymer of polyamic acid salt alkaline solution 103 may include aromatic poly(amic acid), which consists of alternating monomer units of diamine and dianhydride. Upon heat treatment, the poly(amic acid) is converted into an aromatic polyimide. The table below provides examples of suitable monomers for the polymer used in polyamic acid salt alkaline solution 103.

[0061] Dianhydride Diamine 1,4,5,8-naphthalenetetracarboxylic dianhydride 4,4'-diaminobenzophenone 1,4-benzoquinonetetracarboxylic dianhydride 4,4'-oxydianiline 3,3',4,4'-biphenyltetracarboxylic dianhydride benzene-1,4-diamine 4,4'-oxybisphthalic anhydride naphthalene-2,6-diamine benzophenone-3,3',4,4'-tetracarboxylic dianhydride pyromellitic dianhydride

[0062] To synthesize lithium polyamate salt of polyamate alkaline solution 103, polyamic acid can be synthesized first, followed by heat treatment. To synthesize the poly(amic acid) polymer, diamine and dianhydride monomers can be reacted in a suitable solvent, such as N-methyl-2-pyrrolidone (NMP), at a ratio of about 1:1 at a temperature of about 40 to 80°C for 1-8 hours. The concentration of the polymer in the solution can be 5 to 30 wt%, most preferably about 20 wt%. The reaction can be carried out under an inert atmosphere such as nitrogen or argon. The molecular weight of the polymer can be controlled by changing the reaction time and temperature, as well as the purity and ratio of the reactants. To impart chelating ability to the poly(amic acid) PM, a base, preferably an alkali metal hydroxide, and most preferably lithium hydroxide, can be used to neutralize the free carboxylic acid groups. Because the base-neutralized poly(amic acid) is highly water-soluble, it cannot be neutralized after coating the powder, otherwise the polymer coating may completely dissolve in the solution. Therefore, an aqueous solution of lithium hydroxide can be slowly added to an NMP solution of poly(amic acid) and mixed for 10-60 minutes, followed by heat treatment at 50-100°C. The lithium polyamic acid salt can then be separated from the solvent using condenser techniques such as rotary evaporation. Alternatively, the lithium polyamic acid salt can be separated by adding a non-solvent that is miscible with the solvent to precipitate it, followed by filtration to remove the solvent from the precipitate.

[0063] Lithium polyamate salt can then be dissolved in a solvent (e.g., water) to form a lithium polyamate solution 103. The polymer in the alkaline polyamate solution 103 improves the uniform nucleation of catalyst particles and the adhesion to the active electrode material 102. Therefore, the alkaline polyamate solution 103 can be mixed with the active electrode material 102 to form a thin polymer layer on the electrode material 102. See below for reference. Figure 3 As will be described in more detail, the polyamate alkaline solution 103 and the active electrode material 102 can be mixed, dried, etc., until the polymer in the polyamate alkaline solution 103 is deposited on the active electrode material 102, thereby continuously coating the active electrode material 102. During drying, the polymer-coated active electrode material can aggregate to form large particles. Therefore, after drying the active electrode material 102 and the polyamate lithium solution 103, the resulting particles can be ground into powder, thereby producing polymer-coated active electrode material powder 104.

[0064] The active electrode material powder 104 may include at least one (e.g., multiple) fine powder particles. These powder particles may include secondary particles, which are composed of multiple primary particles. In particular, the secondary particles may be chemically bonded, nanoscale aggregates of primary particles. In contrast, primary particles are basic particles held together by atomic or molecular bonds, which can only be separated into smaller particles by applying ultra-high energy. Therefore, primary particles can be much smaller than secondary particles. For example, the diameter of primary particles may be about 1 μm or smaller, while the diameter of secondary particles in the active electrode material powder may be greater than 1 μm, and the size can increase up to tens of micrometers in diameter. Example secondary particles of electrochemical active electrode material powder are referenced below. Figure 6A-6F Shown and described in more detail.

[0065] The catalyst-containing solution 105 can then be mixed with the polymer-coated active electrode material powder 104 to apply the conductive metal catalyst onto the powder 104, as shown in the following reference. Figure 4A In more detail, this produces a catalytically active electrode material powder 106. The catalyst-containing solution 105 may contain a metal dissolved in a solvent, which can be used as a catalyst in the ELD reaction. For example, the metal may include noble metals such as palladium, rhodium, gold, silver, and platinum. In a preferred embodiment, the catalyst-containing solution 105 may include an aqueous solution of silver nitrate, and the metal catalyst for the ELD reaction may include silver. However, it should be understood that the catalyst-containing solution 105 may contain any soluble silver salt.

[0066] Therefore, the metal catalyst can be annealed to the polymer coating of the active electrode material powder. Thus, the catalytic active electrode material powder 106 includes the same polymer coating as the polymer-coated active electrode material powder 104, except that powder 104 may also include a metal catalyst from the catalyst-containing solution 105. See below for reference. Figure 5 As will be described in more detail, a conductive metal, such as copper, can then be deposited and / or coated onto the catalytically active electrode material powder via an ELD reaction. This may include mixing the catalytically active electrode material powder 106 with one or more of a reduction solution 107 and a metal-containing solution 108 to form an ELD bath 109 (also referred to herein as "electroplating bath 109"). The ELD reaction can be carried out in the ELD bath 109, whereby a metal catalyst from the catalyst-containing solution 105 can catalyze the deposition of the metal from the metal-containing solution 108 onto the electrode material powder.

[0067] The following will be a reference Figure 5In a more detailed description, the reducing solution can be first mixed with the catalytically active electrode material powder 106, and then the metal-containing solution 108 can be slowly added. The reducing solution 107 may include one or more of the following: reducing agent 140, buffer solution 141 composed of weak acid and weak base, polymer surfactant 142, defoamer 143, and additive 144, to control the growth properties of the metal precipitate.

[0068] The reducing agent 140 must generally be stable enough to prevent spontaneous decomposition of the ELD bath 109, but must be sufficiently reactive to allow the ELD reaction to occur at a sufficiently high rate so that virtually all soluble metal salts are reduced after a reasonable amount of time.

[0069] The choice of reducing agent 140 depends on the metal being deposited, as the catalytic activity of each metal or alloy differs for different reducing agents. For example, reducing agent 140 may include one or more of aldehydes such as formaldehyde and glyoxylic acid, hydrazine, sodium hypophosphite, amine complexes of boranes including ammonia borane and dimethylamine borane, and sodium borohydride. The concentration of reducing agent 140 in the reducing solution 107 typically exceeds 100% of the stoichiometric value required to reduce all added metal salts to their metallic form, and can be in the range of 0.10 to 0.50 moles.

[0070] Buffer 141 may be a mixture of a weak acid and a weak base, and may be necessary to prevent significant changes in the pH of ELD bath 109 during the ELD reaction. The pH of ELD bath 109 depends on the reducing agent and can be selected to maximize the reaction rate. ELD bath 109 may be alkaline, with a pH range of about 9.0-13.0, although some reducing agents, such as sodium hypophosphite, may also be used selectively in acidic electroplating baths with a pH of about 3.0-6.0. Because some polyimides are readily hydrolyzed in alkaline solutions, in embodiments where the polymer coating includes polyimide, the pH may be maintained below 11 to prevent the polyimide from dissolving in ELD bath 109. The acid used in buffer 141 may include carboxylic acids, such as formic acid, acetic acid, citric acid, etc., and the base may include ammonia or organic amines. However, in other embodiments where a pH greater than 11 is required, an alkaline hydroxide, such as sodium hydroxide, may be added to raise the pH. For alkaline electroplating baths, alkali can be added to the reducing solution 107 at a concentration of 0.25-2.0M, and acid can be added while measuring the pH until the pH stabilizes at the desired value. For acidic electroplating baths, the reverse operation can be performed.

[0071] Electroplating bath 109 may additionally contain surfactant 142 to wet hydrophobic materials such as carbon and to prevent particle aggregation during the ELD reaction. Since hydrogen evolves from the oxidation of the most suitable reducing agent, surfactants that cause foaming are undesirable and potentially unsafe. Therefore, suitable surfactants are typically polymers with a molecular weight of approximately 2.5 to 25 kDa containing functional groups coordinated to the metal surface. Examples of such polymers include poly(ethylene glycol), poly(vinyl alcohol), and poly(vinylpyrrolidone). The concentration of surfactant in the reducing solution 107 can be 5-25 g / L.

[0072] Defoamer 143 and surfactant 142 can be added to prevent excessive foaming caused by evolving hydrogen, which could pose an explosion risk. Defoamer 143 may include aliphatic alcohols, such as methanol, ethanol, or isopropanol, and may be present in the reducing solution 107 at a concentration of 50-250 mL / L.

[0073] To control the properties of the deposited metal film, particularly its surface morphology, grain size, and impurity concentration, an additive 144 in a concentration ranging from 1 to 50 parts per million can be used in the reducing solution 107. In a preferred embodiment, a two-additive system can be used, where one additive increases the deposition rate (“promoter”) and the other decreases the deposition rate (“inhibitor”). The promoter and inhibitor must be selected such that the relative adsorption of the inhibitor to the promoter increases as the potential on the metal surface becomes more negative. This has the effect of reducing the overpotential in areas of lower negative potential on the metal surface and increasing the overpotential in areas of higher negative potential, substantially preventing nodular growth of the metal film and significantly improving the uniformity of the surface morphology.

[0074] The metal-containing solution 108 includes the metal to be coated onto the electrode material powder 106 during the ELD reaction. More specifically, the metal-containing solution 108 may include one or more of the following: a soluble metal salt 150 of one or more metals to be deposited, a complexing agent 151 for chelating the metal salt 150, and a pH adjuster 152.

[0075] The soluble metal salt 150 may include one or more of the following metals: titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, zirconium, tungsten, molybdenum, tin, antimony, lead, and bismuth. The metal salt 150 may be in the form of a sulfate, nitrate, chloride, acetate, or any other commercially available compound that is readily soluble in water and does not undergo any undesirable reaction in the ELD bath 109. In a preferred embodiment, the concentration of the metal salt 150 may be as high as possible to reduce the overall volume of the solution. Depending on the solubility of the metal salt 150, the concentration in the metal-containing solution 108 may range from 0.25 to 1.50 moles.

[0076] The complexing agent 151 in the metal solution 108 prevents the metal salt 150 from precipitating as a hydroxide at high pH and prevents the spontaneous decomposition of the ELD bath 109. The complexing agent 151 may comprise a multicoordinate carboxylic acid or amine, but the most preferred complexing agent depends on the metal salt present and the desired pH. For example, the complexing agent 151 may comprise one or more of tartaric acid, citric acid, ethylenediamine, ethylenediaminetetraacetic acid (EDTA), and thiourea. The concentration of the complexing agent can range from 10% to 25% exceeding the stoichiometry required to form the metal-ligand complex. For example, in a solution containing 0.50 M copper(II) sulfate, 0.55-0.625 M EDTA or 1.1-1.25 M tartaric acid can be used.

[0077] pH adjuster 152 is added to the metal-containing solution 108 to achieve the same pH as the reduction solution 107. If the reduction solution is acidic, a weak acid, such as citric acid or acetic acid, can be used. If the reduction solution 107 is alkaline, an amine such as ammonia or an alkaline hydroxide such as sodium hydroxide can be used. The amount of pH adjuster 152 used can depend on the structure and concentration of the complexing agent 151 and the target pH. In the metal-containing solution 108, the concentration of the pH adjuster can be in the range of 0.1-1.0 mol. References will follow below. Figure 5 The ELD reaction and the process of coating the catalytic active electrode material powder 106 with a conductive metal are described in more detail.

[0078] Continue Figure 1A The ELD reaction is carried out in an ELD bath 109, with conductive metal-coated catalytic active electrode material powder 106 derived from a metal-containing solution 108. The liquid in bath 109 can then be evaporated, leaving metal-coated active electrode material powder 110, which is coated with a continuous layer of metal from the metal-containing solution 108. An example of metal-coated active electrode material powder 110 is shown below. Figure 6E and 6F The images are shown and described in the SEM images.

[0079] After using a polymer from a polyamic acid salt alkaline solution 103 and a metal-coated electrode material powder from a metal-containing solution 108, the metal-coated active electrode material powder 110 can be used to form an electrode 111 containing the metal-coated active electrode material powder 110. Prior to manufacturing the electrode 111, the metal-coated active electrode material powder 110 can be premixed with one or more conductive additives and / or binders. Manufacturing the electrode 111 may include mixing the metal-coated active electrode material powder 110 with conductive additives and / or binders to form a slurry, coating the slurry onto a conductive substrate, drying the slurry-coated conductive substrate, compressing the coating, and calendering. For example, the metal-coated active electrode material powder 110 can be mixed with one or more slurry additives 132 to form a slurry. Specifically, the slurry additive 132 may include one or more solvents and / or binders, such as polymer binders. Alternatively, the metal-coated active electrode material powder 110 can be mixed with a binder and at least one additive in a non-aqueous solvent to form a slurry. The slurry containing the metal-coated active electrode material powder 110 can then be coated onto a conductive substrate (also referred to herein as a "current collector"), such as a metal foil (e.g., copper foil, lithium foil, aluminum foil), and then dried, pressed, and rolled to form the electrode 111.

[0080] Then, by assembling electrode 108 with another electrode and separator 114, electrode 111 comprising metal-coated active electrode material powder 110 can be manufactured as lithium-ion battery cell 118. In some embodiments, only one metal-coated electrode 111 can be used to manufacture lithium-ion battery cell 118. In such embodiments, electrode 111 can be manufactured with electrodes of opposite polarity. For example, if the metal-coated electrode includes an anode (e.g., including graphite as an electrochemically active material), a cathode can be used in conjunction with electrode 111 to form battery cell 118. Conversely, if electrode 111 is manufactured as a cathode (e.g., the electrochemically active material of metal-coated active electrode material powder 110 includes one or more of the following: LiCoO2, LiMn2O4 and LiFePO4, lithium nickel manganese cobalt oxide (NMC), etc.), electrode 111 can be used in conjunction with an anode to manufacture battery cell 118. In yet another embodiment, two metal-coated electrodes 111 of opposite polarity can be manufactured and used to form lithium-ion battery cell 118.

[0081] The separator 114 is used to separate the anode 112 and the cathode 116, thereby preventing them from physical contact. In a preferred embodiment, the separator 114 has high porosity, excellent stability to the electrolyte, and excellent liquid retention properties. Example materials for the separator 114 can be selected from nonwoven fabrics or porous membranes made of polyolefins such as polyethylene and polypropylene, or ceramic-coated materials.

[0082] Then you can use electrolyte 117 (from...) Figure 1A (The dashed line in the diagram indicates that) lithium-ion battery cells 118 are filled to produce filled lithium-ion battery cells 120. Lithium-ion battery 118 may also include a housing 114, such as a pouch, which houses the anode 112, cathode 116, separator 114, and electrolyte 117. When battery cell 118 is completed, housing 114 can be sealed so that electrolyte 117 is contained within housing 114.

[0083] As shown in the figure, the electrolyte 117 is in close contact with the components in the lithium-ion battery cell 120. The electrolyte 117 may include lithium salts, organic solvents such as organic carbonates, and additives. The electrolyte 117 is present throughout the lithium-ion battery and is in physical contact with the anode 112, cathode 116, and separator 114.

[0084] The filled lithium-ion battery cell 120 can then undergo battery cell formation, also known as a first charge / discharge cycle, to form a lithium-ion battery cell 122. The lithium-ion battery cell 122 can be a fully manufactured and complete battery cell, ready to be inserted into a lithium-ion battery along with other similarly completed lithium-ion battery cells for use in a lithium-ion battery.

[0085] In addition, other reactions, such as addition reactions, may occur during the formation of the battery cell. In some embodiments, the lithium-ion battery cell may be thermally treated during battery formation. Thermal treatment may affect the kinetics of the battery module reaction. For example, the battery cell may be exposed to temperatures ranging from 30°C to 100°C, such as 35°C, 45°C, 60°C, 80°C, or 100°C, for a period of time ranging from 30 minutes to 7 days.

[0086] In this way, lithium-ion batteries can be manufactured in which electrochemically active materials are coated with polymers and conductive metals and used to form electrodes of at least one battery cell of the lithium-ion battery. Specifically, a lithium-ion battery may include one or more battery cells, wherein the one or more battery cells include a separator, an electrolyte, and two electrodes, namely an anode and a cathode, wherein at least one electrode contains an electrochemically active material having a layered polymer and conductive metal coating.

[0087] Turn now Figure 1B It shows something similar to Figure 1A Example diagram and another example diagram 100 of the method, the difference being in Figure 1B The polymer used in the embodiments to coat the electrochemically active electrode material 102 may include a crosslinkable poly(amic acid)amine salt. Therefore, schematic diagram 100 simply illustrates the use of the polymer described above. Figure 1A Another method for forming the metal-coated electrode 111 using polymers different from those discussed in the paper (e.g., not lithium polyamic acid salts).

[0088] Therefore, instead of the above Figure 1A The aforementioned non-crosslinkable polymer, Figure 1B A method is provided for manufacturing a metal-coated electrode 111 using a crosslinkable poly(amic acid)amine salt 123. Therefore, it is preferable to use a low-temperature heat treatment to... Figure 1B The polyimide in the polymer is crosslinked to improve its electronic conductivity and prevent its dissolution in highly alkaline solutions. The crosslinking agent can be a monofunctional monomer capable of terminating (capping) the polymer chain, such as an aromatic carboxylic anhydride or an aromatic amine. The crosslinking agent must also contain one or more alkynes conjugated with an aromatic ring, including an aromatic ring linked to an amine or anhydride. An example of a suitable crosslinking agent is 4-phenylethynyl phthalic anhydride (PEPA). The crosslinking agent can be added at a molar ratio of 1:20 to 1:100 relative to the total molar number of monomers in the polymer. If the crosslinking agent is an amine, less than an equivalent of the diamine monomer can be added; if it is an anhydride, less than an equivalent of the dianhydride monomer can be added. For example, if the crosslinking agent is PEPA and a crosslinking ratio of 1:50 is used, the monomer mixture is 1 part PEPA, 25 parts diamine, and 24 parts dianhydride. Adding a capping crosslinking agent can significantly reduce the molecular weight of the resulting polymer. It is necessary to ensure that the molecular weight of the polymer is above the critical molecular weight for entanglement; otherwise, the polymer coating may be discontinuous. Therefore, a crosslinking ratio between approximately 1:30 and 1:50 is preferred.

[0089] The synthesis procedure for cross-linked poly(amic acid) is similar to that described above. Figure 1A The synthesis procedure for the uncrosslinked polymer described herein differs in that the poly(amic acid) is neutralized with an organic amine such as diethanolamine or triethylamine instead of an alkaline hydroxide. The resulting thermally crosslinkable poly(amic acid) amine salt is water-soluble and can be coated onto the powder using the same process. After coating the polymer, a thermal crosslinking treatment must be performed for 15-60 minutes at a temperature of 350-425°C, which can be carried out in air or an inert atmosphere such as argon or nitrogen. After cooling, the crosslinked polyimide-coated powder is mixed with an alkaline hydroxide solution 125, preferably lithium hydroxide or sodium hydroxide, for 10-60 minutes. The alkaline hydroxide solution 125 may contain a hydroxide concentration of 0.5-2.5 mol and may be heated to a temperature of 40-80°C. The powder is then removed from the mixture by filtration and washed several times with deionized water to remove any excess hydroxide. The powder is then mixed with a catalyst-containing solution 105 and heated in a manner similar to that used with uncrosslinked polyimide powder to form catalytically active electrode material powder 106, as will be referred to below. Figure 4B A more detailed description.

[0090] Turning Figure 2It shows metallized (e.g., metal plating) electrochemically active electrode materials, such as those described above. Figure 1A and 1B The flowchart of an example method 200 for electrochemically active electrode material 102 described herein is provided. Therefore, method 200 provides a general overview of an example method for coating electrochemically active electrode materials with a conductive metal such as copper.

[0091] Method 200 begins at 202, and includes the following as described above. Figure 1A and 1B The polymer is synthesized in the same or similar manner as described. Therefore, the polymer may include one or more of the following: crosslinkable poly(amic acid)amine salts, aromatic poly(amic acid), aromatic polyimides, lithium polyamate salts, and any other aromatic polyimide-type polymers. As described above... Figure 1A and 1B As described, a different synthesis procedure can be used in the synthesis of crosslinkable poly(amic acid)amine salts compared to lithium polyamic acid salts. The synthesized polymer can then be coated onto an electrochemically active electrode material at 204°C. Specifically, the synthesized polymer can be dissolved in a solvent and then mixed with the electrochemically active electrode, as will be referred to below. Figure 3 To describe in more detail: The polymer coating can be continuous, so that it completely covers the outer surface of the powder particles of the electrochemically active electrode material.

[0092] Then, at position 206, the catalyst can be adhered to the polymer-coated electrochemically active electrode powder, such as the one described above. Figure 1A and 1B The polymer-coated active electrode powder 104 described herein will be further described below with reference to Figure 4. The catalyst may include, for example, a metal catalyst used in ELD reactions. Once the ELD catalyst has adhered to the polymer-coated electrochemically active electrode powder, the ELD reaction can proceed. Thus, at 208, the electrochemically active electrode powder can be coated with a conductive metal via the ELD reaction. Figure 5 The flowchart in the diagram provides more details of an example method for electroplating active electrode powder with a conductive metal (e.g., performing an ELD reaction). Method 200 then concludes.

[0093] Turning Figure 3 It illustrates applying a polymer coating to an electrochemically active electrode material (e.g., the one described above). Figure 1A and 1BThe flowchart illustrates an example method 300 for the electrochemically active electrode material 102 described herein. Method 300 begins at 302 and includes dissolving a synthesized polymer (e.g., lithium polyamate, crosslinkable poly(amic acid)amine) in a solvent. In one embodiment, the solvent may include water. Specifically, based on the amount to be coated onto the powder, the polymer may be dissolved in deionized water at a concentration of about 0.5-5.0% by weight. Method 300 may then proceed from 302 to 304, which includes depositing the synthesized polymer onto the electrochemically active electrode material by mixing the synthesized polymer solution with the electrochemically active electrode material. Specifically, a high-shear mixer is used to mix the polymer solution, for example, the one described above... Figure 1A The polyamic acid alkaline solution 103 described herein and / or the above-mentioned Figure 1B The crosslinkable poly(amic acid)amine salt described herein is mixed with an active material powder to fully disperse the powder in a polymer solution, resulting in an aqueous slurry with a solids loading of 40-70% by weight. In a preferred embodiment, the solids loading can be kept as high as possible while still ensuring complete dispersion of the powder. Based on the geometry and surface area of ​​the powder, the total loading of the polymer (e.g., lithium polyamic acid salt) on the powder can be 1.0-5.0% by weight, and more preferably between 2.0-3.0% by weight. It is preferable to apply as little polymer, such as lithium polyamic acid salt, as possible while still achieving a continuous polymer coating.

[0094] The resulting mixture / slurry is then dried into a solid at point 306. For example, the mixture / slurry of the polymer solution and the electrochemically active electrode material can be vacuum dried at a temperature of 60-100°C. After drying, the resulting solid, comprising the electrochemically active electrode material coated with the synthetic polymer, is ground into a coarse powder at point 308. In one embodiment, the solid can be ground to a particle size of no more than 0.5 mm, preferably 0.1-0.5 mm. The powder particles can then be ball-milled at point 310 using a non-solvent. Specifically, the coarse powder, the non-solvent, and the grinding media can be loaded into a rotary ball mill chamber. The purpose of the non-solvent is to swell and plasticize the polymer, such as lithium polyaminate, thereby dispersing it uniformly on the surface of the powder by mechanical grinding, while avoiding powder agglomeration. Suitable non-solvents are preferably low molecular weight polar aprotic organic solvents, such as esters, ketones, or carbonates. For example, the non-solvent may include acetone, as it is the lowest molecular weight ketone and is inexpensive and readily available. The grinding media preferably have a spherical shape with a diameter between 1-10 mm, and most preferably about 5 mm in diameter. The grinding media are preferably made of a high-density material that is durable and non-reactive to the components being ground.

[0095] The powder may comprise about 10-30% of the grinding chamber volume, while the grinding media may comprise about 20-50% by volume. Non-solvents may be added so that the resulting slurry has a solids content of about 25-50% by weight, excluding the weight of the grinding media. About 20-50% of the grinding chamber may still be unfilled. The rotary mill is preferably operated at 10-400 rpm, most preferably 50-200 rpm. The material may be ground continuously for 0.5-4.0 hours until a thick slurry free of agglomerates is obtained.

[0096] Then, at 312, the grinding media and non-solvents can be removed to form polymer-coated powder particles, for example, as described above. Figure 1A and 1B The polymer-coated active electrode material powder 104 described herein. Specifically, the grinding media is separated from the slurry by passing the mixture through a sieve that allows the slurry to pass through but not the grinding media. The desired solids are then removed from the non-solvent by filtration, resulting in a non-agglomerated powder coated with lithium polyamate. This powder can be further dried before further processing, preferably under vacuum at a temperature between 20-80°C. The powder particles coated with lithium polyamate may include secondary particles, and the lithium polyamate coating may be continuous (covering the entire outer surface of the secondary particles), relatively smooth, and substantially uniform in thickness. Once the secondary powder particles have been coated with the polymer coating, method 300 proceeds to... Figure 4A Method 400 of 402 or Figure 4B Method 450 of 452. Specifically, if lithium polyamate is used as the polymer in the polymer coating, method 300 can proceed to... Figure 4A If poly(amic acid)amine is used as the polymer in the polymer coating, then method 300 can proceed to... Figure 4B .

[0097] Continue marching to Figure 4A The method 400 illustrates adhering a catalyst to a polymer-coated chemically active electrode material powder, for example, a lithium polyamic acid salt coating on a polymer-coated active electrode material powder 104.

[0098] Method 400 from Figure 3 Method 300 continues at 312 and begins by mixing lithium polyamate salt-coated powder particles with a catalyst-containing solution (e.g., the one described above). Figure 1A and 1BThe catalyst-containing solution 105 described herein is mixed to deposit the catalyst onto the polymer-coated powder particles. The catalyst can be a catalyst used for ELD reactions, such as one or more noble metals including palladium, platinum, rhodium, gold, silver, etc. In one embodiment, the polymer-coated powder can be mixed with an aqueous solution of silver nitrate for 5-30 minutes. The powder loading in the mixture can be 5-25% by weight. In a preferred embodiment, the powder loading in the mixture can be 15% by weight. Silver nitrate can be added at a molar ratio corresponding to the free carboxylic acid ester groups in the lithium polyamate salt at a 1:1 ratio. The required amount of silver nitrate can be calculated based on the molecular weight of the poly(amic acid) repeating unit and the number of carboxylic acid groups in each repeating unit. Depending on the loading of the lithium polyamate salt on the powder and the powder loading in the mixture, the concentration of silver nitrate can be about 1-20 g / L.

[0099] Then, after mixing the polymer-coated powder particles in a catalyst solution (e.g., a silver nitrate solution), method 400 proceeds from 402 to 404. At 404, method 400 includes separating the powder particles from the mixture by filtration. Then, at 406, the powder particles can be washed several times with deionized water until all excess silver nitrate is removed. After washing at 406, method 400 can proceed to 408, which includes annealing the catalyst to the powder particles by heating and then cooling them. In one embodiment, the powder particles can be heated in air to a temperature of 250-300°C for 15-60 minutes, and then cooled to room temperature before further processing. Method 400 then proceeds to... Figure 5 Method 500, part 502.

[0100] Alternatively, Figure 4B An example method 450 is shown to adhere a catalyst to a poly(amic acid)amine coating on a polymer-coated electrochemically active electrode material powder (e.g., polymer-coated active electrode material powder 104). Therefore, if a poly(amic acid)amine salt is used as the polymer for the polymer-coated electrochemically active electrode material, method 450 can be derived from... Figure 3 Method 300 begins at step 312. Method 450 can be substantially the same as Method 400, except that, as described in steps 402-408 of Method 400, prior to mixing, separating, rinsing, and annealing the catalyst and powder particles, Method 450 may include an additional step of mixing the polymer-coated powder particles with an alkaline hydroxide solution. Although lithium polyamic acid salts are neutralized with alkaline hydroxide during synthesis, poly(amic acid)amine salts are neutralized with organic amines such as diethanolamine or trimethylamine during their synthesis. Therefore, the poly(amic acid)amine salt is not mixed with the alkaline hydroxide solution until it has been coated onto the polymer-coated electrochemically active electrode powder particles.

[0101] Method 450 begins at 451 and includes crosslinking the poly(amic acid)amine salt by heating. For example, the polymer-coated electrochemically active electrode powder particles containing a poly(amic acid)amine salt coating can be heated to a temperature of 350-425°C for 15-60 minutes, which can be carried out in air or an inert atmosphere such as argon or nitrogen. After cooling, method 450 can continue from 451 to 452, which includes mixing the polymer-coated powder particles with an aqueous solution of alkaline hydroxide. For example, the crosslinked polyimide-coated powder can be mixed with an aqueous solution of alkaline hydroxide, preferably lithium hydroxide or sodium hydroxide, for 10-60 minutes. The alkaline hydroxide solution can have a hydroxide concentration of 0.5-2.5 mol and can be heated to a temperature of 40-80°C.

[0102] Then, method 450 continues from 452 to 454, which includes removing powder particles from the mixture by filtration. After filtration, method 450 can continue from 454 to 456, which includes rinsing the powder particles with deionized water. In particular, the powder can be washed with deionized water several times to remove any excess hydroxide. The powder is then mixed with silver nitrate and subjected to the same process as described above. Figure 4A The uncrosslinked polyimide powder described in method 400 is heated in a similar manner. Therefore, method 450 can proceed to steps 458-464, which can be performed in accordance with the above-mentioned references. Figure 4A Steps 402-408 described are the same as or similar to those described above. After performing steps 458-464, method 450 can then proceed to... Figure 5 Method 500, specifically 502.

[0103] Continue marching to Figure 5 It illustrates performing an ELD reaction to deposit a conductive metal (e.g., copper) onto a polymer-coated electrochemically active electrode powder containing an ELD catalyst (e.g., the one described above). Figure 1A and 1B Example method 500 is described in the section on the catalytic active electrode material powder 106). Therefore, method 500 can be derived from... Figure 4B 464 or Figure 4A 408 continues its journey.

[0104] Method 500 begins at 502 and includes heating the reducing solution (e.g., the one described above). Figure 1A and 1B The reducing solution 107 described herein can be heated to 50-80°C. Furthermore, during the ELD reaction (steps 508-514) and / or when a metal-containing solution (e.g., as described above) is applied... Figure 1A and 1BThe metal-containing solution 108 described herein can be heated further before being added to the reduction solution and catalytic powder particles. This can be achieved by adding a buffer (e.g., as described above). Figure 1A and 1B Buffer 141 described in the text), surfactant (e.g., the one mentioned above) Figure 1A and 1B Surfactant 142 described in the text), defoamer (e.g., the above-mentioned surfactant 142), and defoamer (e.g., the above-mentioned surfactant 142). Figure 1A and 1B Defoamer 143 described herein) and additives (such as those mentioned above) Figure 1A and 1B The reducing solution is prepared by dissolving additive 144 described herein in sufficient deionized water to achieve 80-90% of the final volume of the reducing solution. The reducing agent (e.g., the one described above) can be used to prepare the reducing solution. Figure 1A and 1B The reducing agent 140 described herein is dissolved alone in deionized water (10-20% of the final volume) and added immediately before use to prevent decomposition before the ELD reaction begins (e.g., just before the metal-containing solution is added at 508).

[0105] Method 500 can proceed from 502 to 504, which includes mixing catalytic powder particles with a reduction solution to disperse the powder. Therefore, the reduction solution (before adding the reducing agent) is heated to a desired temperature, and then the catalytic powder is added to the solution and mixed until fully dispersed. Next, at 506, a reducing agent is added to a reaction mixture containing the reduction solution and the mixed catalytic powder particles. The reducing agent may be dissolved in deionized water before being added to the reaction mixture. After a waiting time of 10 seconds to 5 minutes, a portion of the total metal-containing solution is added to the mixture. The reduction solution, the metal-containing solution, and the dispersed powder particles may include an ELD bath (e.g., as described above). Figure 1A and 1B The ELD bath 109 described in the text is used, and the ELD reaction can proceed once the metal-containing solution is added at 508.

[0106] Depending on the solid loading of the reaction mixture, 5-20% of the total volume of the metal source solution can be added initially (at 508). Method 500 can then proceed from 508 to 510, which involves mixing the reaction mixture (ELD bath) for a period of time to allow the ELD reaction to proceed. The ELD reaction can be allowed to proceed for 30-120 minutes, or until the reaction is nearly stopped, as demonstrated by the significant reduction in hydrogen evolution.

[0107] Then, the remaining portion of the metal-containing solution is added at 512. In one embodiment, the remaining portion of the metal source solution may be added slowly over a span of 30-240 minutes to limit the rate of the ELD reaction. The ELD bath may be continuously mixed throughout the ELD reaction. Thus, method 500 can proceed from 512 to 514, which involves continuing to mix the reaction mixture in the ELD bath for a period of time (until the reaction stops). For example, after all the metal source solution has been added, the reaction may be allowed to proceed for an additional 30-120 minutes until a considerable number of metal ions are no longer dissolved in the reaction mixture.

[0108] Then, method 500 continues from 514 to 516, which includes removing the powder from the solution by filtration. Subsequently, at 518, the powder can be rinsed with deionized water. In one embodiment, several equal portions of deionized water can be used to remove impurities from the powder. Then, at 520, the powder can be vacuum dried to form a metal-coated electrochemically active electrode powder (e.g., as described above). Figure 1A and 1B The metal-coated active electrode material powder 110 described herein can be dried under vacuum to remove residual moisture without oxidizing the metal surface. Then method 500 ends.

[0109] Turn now Figure 6A-6F It shows various SEM images of example secondary particles from electrochemically active electrode materials. In particular, it shows SEM images of electrochemically active anode materials including graphite. More specifically, it shows SEM images of mesophase carbon microspheres (MCMB).

[0110] Figure 6A A first SEM image 600 of an example secondary particle 602 of bare MCMB without coating is shown. Thus, the bare graphite outer surface 604 of the secondary particle 602 is shown as exposed in FIG. 6.

[0111] Figure 6B A second SEM image 610 of the secondary particles 602 of the MCMB, which are coated with a conductive metal coating but without a polymer coating (the secondary particles 602 are coated using a method in the prior art that does not coat the secondary particles 602 with a polymer before applying the metal coating), is shown. Figure 6B The metal coatings in it include copper coating 606.

[0112] Figure 6C A third SEM image 620 of the secondary particles 602 of the MCMB, coated with a polymer coating and a conductive copper coating 606, is shown. The above reference can be used. Figure 1A-5 One or more coating methods are described, in which secondary particles 602 are coated with a polymer and a conductive copper coating 606. However, without the use of additives (such as those described above) Figure 1A and1B In the case of additive 144 described in the text, coating Figure 6C Secondary particles 602 in the middle. Figure 6D It shows Figure 6C A further magnified fourth image 630 of the third SEM image 620.

[0113] Figure 6E A fifth SEM image 640 of the secondary particles 602 of the MCMB, coated with a polymer coating and a conductive copper coating 606, is shown. The above reference can be used. Figure 1A-5 One or more coating methods are described, in which secondary particles 602 are coated with a polymer and a conductive copper coating 606. Furthermore, with Figure 6C and 6D In contrast to the secondary particles 602, when using additives (such as those mentioned above) Figure 1A and 1B In the case of additive 144 described in the text, coating Figure 6C Secondary particles 602 in the middle. Figure 6F It shows Figure 6E A magnified sixth image 650 of the fifth SEM image 640.

[0114] As from Figure 6A-6E The SEM images show that, compared to secondary particles without a polymer coating, the polymer-coated metallized secondary particles contain a more continuous, smooth, and uniform metal coating. In particular, the MCMB graphite catalyzed according to one or more embodiments disclosed herein did not exhibit metal particle separation during processing, indicating a significant improvement in adhesion compared to methods without polymers (prior art). Due to the better adhesion of the catalyst layer, the copper coating deposited on this material (… Figure 6C-6F ) compared to MCMB graphite without a polymer layer ( Figure 6B It is significantly more continuous and has fewer nodules. However, Figure 6C and 6D The copper deposits in the coating still exhibit some discontinuity and a nodular surface morphology. Adding 1-50 ppm of inhibitors (e.g., benzotriazole, "BTA") and promoters (sodium 3-(mercaptopropyl)sulfonate, "MPS") is effective in suppressing this nodular growth, resulting in a fully continuous copper coating with a uniform surface morphology, such as... Figure 6E and 6F As shown. Based on approximately 2m 2 Based on the specific surface area of ​​the original powder and a copper loading of approximately 12% by weight, the thickness of the copper layer is calculated to be approximately 150 nm.

[0115] Turning Figure 7It shows a schematic cross-sectional view 700 of an example secondary particle of an electrochemically active electrode material coated with a polymer and a conductive metal according to one or more embodiments of the present disclosure. Specifically, Figure 7 It shows the use of the above Figure 1A-5 Examples of the structure, morphology and layering of polymer coatings on secondary particles of electrochemically active electrode materials, catalysts, and conductive metal coatings when one or more coating and / or metallization methods described herein are used to coat electrochemically active electrode materials with the above-described components.

[0116] therefore, Figure 7 A schematic cross-sectional view of an example secondary particle of metal-coated active electrode material powder 110 is shown. The metal-coated active electrode material powder 110 includes electrochemically active electrode material 702, which can be used with the aforementioned... Figure 1A and / or Figure 1B The electrochemically active electrode material 702 described herein is the same as or similar to that described elsewhere. Therefore, the electrochemically active electrode material 702 may include, for example, graphite. The electrochemically active electrode material may be coated with two layers: a polymer coating 704 and a metal coating 706 located between the outer surfaces 705 of the electrochemically active electrode material 702. The polymer coating 704 comprises a polymer (e.g., aromatic polyimide), and the metal coating 706 comprises a conductive metal (e.g., copper). Figure 7 As can be seen from the embodiments, the polymer coating 704 and the metal coating 706 can be completely continuous and substantially uniform in thickness. Therefore, the polymer coating 704 can be completely continuous around the outer surface 705 of the secondary particles of the electrochemically active electrode material 702 (completely covering all outer surfaces 705). Although the two coatings 704 and 706 are depicted as having the same thickness, it should be understood that in other embodiments, the thicknesses of coatings 704 and 706 can differ from each other. The thickness of the polymer coating 704 can be 50-200 nm. The thickness of the metal coating 706 can be less than 150 nm and can be 75 or 150 nm.

[0117] As mentioned above Figure 1A-1B As described in 3-4B, a catalyst can be applied to the polymer coating 704, followed by a low-temperature heat treatment 408 (e.g., as described above). Figure 4A and 4B The catalyst particles 708 are fixed / annealed to the polymer coating 704 at 250-300°C as described in the text. Figure 7As illustrated in the example, catalyst particles 708, such as silver particles, can protrude into the polymer coating 704, but cannot protrude into or extend into the electrochemically active electrode material 702. Therefore, during the process of applying the catalyst to the polymer coating 704 and heating it, the catalyst particles 708 become embedded in the polymer coating 704. Catalyst particles 708 can also protrude into the metal coating 706. The areal density of catalyst particles 708 on the surface of the polymer coating 704 of the electrochemically active electrode material 702 can be approximately 500-10,000 particles / μm. 2 .

[0118] As shown, the metal coating 706 can be completely continuous around the polymer coating 704 and the catalyst particles 708. That is, the metal coating 706 can completely cover the catalyst particles 708, as well as all outward-facing surfaces of the polymer coating 704 that are not covered by the catalyst particles 708.

[0119] Continue marching to Figure 8 The diagram shows a graph 800 reporting example test data for a lithium-ion battery cell, wherein the lithium-ion battery cell includes electrodes having an electrochemically active material coated with a conductive metal according to one or more embodiments of the present disclosure. Specifically, copper-coated MCMB (in...) is used. Figure 8 The curve shown in the middle is 802) and the unmodified MCMB (in Figure 8 Electrodes were prepared using curves 804 and 806 (shown as a "control"). Electrodes were prepared by using the methods described above. Figure 1A and 1B Using the same binder and conductive additive formulation described above, an active material slurry was applied to copper foil to fabricate two electrodes. The electrodes were designed to have the same areal capacity and porosity to isolate the effects of the copper coating. Half-cells were assembled opposite lithium foils and discharged at different rates. At a rate of 10C (complete discharge within 6 minutes), the copper-coated MCMB was able to discharge approximately 81% of its nominal capacity (curve 802), while the control discharged only approximately 66% of its nominal capacity (curves 804 and 806).

[0120] In this way, better uniformity and adhesion of catalyst nanoparticles to electrochemically active electrode materials can be achieved through the novel formation mechanism disclosed herein. Unlike conventional methods of nucleation of noble metal nanoparticles on substrate surfaces, in this example, nanoparticles are uniformly nucleated within a noble metal-impregnated polymer bulk. The catalyst nanoparticles then aggregate and migrate to the polymer surface, naturally forming a closely packed structure. Because the adsorption amount of noble metal ions is stoichiometric with the number of repeating polymer units, and the polymer has a uniform composition, the areal loading of the catalyst is proportional to the thickness of the polymer coating. Specifically, the areal density of the catalyst on the surface of the polymer coating of the electrochemically active electrode material can be approximately 500-10,000 particles / μm. 2 .

[0121] Therefore, as long as the polymer coating is continuous and uniform, the catalyst layer will be closely packed and uniform. Due to the inherent lack of defects, this closely packed catalyst structure allows for continuous coatings with thicknesses close to the theoretical minimum. Furthermore, because the polymer has the ability to trap noble metals, the process is insensitive to the surface chemistry of the substrate and requires no additional pretreatment.

[0122] Because catalyst particles migrate from the polymer bulk to its surface, a strong mechanical interlock exists between the catalyst particles and the entanglement within the polymer, resulting in significantly improved adhesion of the catalyst particles and the subsequent ELD metal coating. This type of interlock does not occur when catalyst particles nucleate on the polymer surface using an aqueous reducing agent. This superior adhesion significantly reduces the sensitivity of catalyst performance to the chemical and processing conditions of the ELD process, simplifying the development and optimization of such processes. Compared to existing technologies, this low sensitivity allows for the use of solid loadings three orders of magnitude higher in the ELD reaction, resulting in higher throughput and lower process costs.

[0123] In addition, polymer coating process ( Figure 3 A plasticizer is used to allow the coating to be mechanically thinned by grinding without raising the temperature above the polymer's glass transition temperature. This can produce a completely continuous and uniform polyimide coating at a loading of less than 3%. Furthermore, it can produce agglomerated fine powder without the need for additives to control aggregates, and is primarily water-based. Additionally, this polymer coating process avoids the use of high-temperature or high-pressure equipment.

[0124] Due to the uniform composition and thickness of the polyimide and the uniform nucleation of the catalyst particles derived from it, the catalyst process produces a more uniform catalyst layer. Furthermore, the catalyst process ( Figure 4A and 4BThis results in substantially better adhesion, and because polyimide has sufficient PM-trapping capabilities, the catalyst process is not highly dependent on the surface chemistry of the substrate material. Furthermore, the catalyst process avoids the use of palladium, and the silver yield is higher than that of existing methods.

[0125] In addition, ELD process ( Figure 5 The method is far less sensitive to processing conditions, especially mechanical stress, than methods without polymer coatings. Therefore, it utilizes a higher solids loading, which allows for smaller solution volumes and equipment, thus reducing capital and operating costs and waste generation. Furthermore, additives are used to suppress nodular growth, resulting in a more uniform coating.

[0126] In this way, the metal coatings produced by these methods exhibit: complete or near-complete continuity, a thickness of about 150 nm, allowing the application of continuous coatings with a loading of about 10% by weight, and a more uniform surface morphology resulting in a lower specific surface area.

[0127] In this way, composite materials produced by depositing a metal coating on active material powder exhibit improved high-rate discharge capability and negligible volumetric capacity reduction due to the conductive metal coating, thereby allowing the material to be introduced into existing battery designs with the potential to improve cycle life, energy density and high-rate charging capability.

[0128] The process described herein for coating polymers onto powder surfaces is superior to existing technologies because it does not use large amounts of organic solvents. The initial polymer application is entirely water-based, and the non-solvents used in the milling process can be separated by filtration and then recycled back into the process. This recycling process avoids energy-intensive unit operations such as vaporization and condensation and eliminates the need for any non-solvent purification. The method described herein also eliminates the need for the use of volatile organic compounds in high-pressure or high-temperature equipment.

[0129] The metal coating produced by this process exhibits complete continuity and a smooth surface morphology with a thickness of less than 150 nm. Therefore, continuous metal coatings can be deposited onto active material powders with a metal loading of less than approximately 10% by weight. Although this slightly reduces the gravimetric energy storage capacity of the active material, the reduction in volumetric capacity is negligible due to the low thickness and high density of the metal coating. Therefore, surface modification of active materials using this process is feasible for producing materials with improved properties. For example, the discharge capability of MCMB graphite at a rate of 10C increased by 23% due to the copper coating, while the volumetric capacity was not significantly affected.

[0130] In addition to those shown and described herein, various modifications to the invention will be apparent to those skilled in the art. Such modifications are also intended to fall within the scope of the appended claims. The foregoing description illustrates specific embodiments of the invention but is not intended to limit its practice. The foregoing discussion should be understood as illustrative and should not be considered restrictive in any sense. Although the invention has been specifically shown and described with reference to preferred embodiments, those skilled in the art will understand that various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the claims. All means or steps, as well as corresponding structures, materials, actions, and equivalent substitutions of functional elements in the following claims are intended to include any structure, material, or action for performing a function in combination with other claimed elements specifically claimed.

[0131] Finally, it will be understood that the articles, systems, and methods described above are all embodiments of this disclosure, but are not limiting embodiments, and many variations and extensions are contemplated. Therefore, this disclosure includes all novel and non-obvious combinations and sub-combinations of the articles, systems, and methods disclosed herein, and any and all equivalent substitutions thereof.

Claims

1. An electrochemically active electrode material, comprising: Secondary particles composed of multiple primary particles of the electrochemically active electrode material; A continuous polymer coating that is directly coupled to and completely covers the outer surface of the secondary particles, the continuous polymer coating having a uniform thickness; A metal catalyst for catalyzing the electrodeposition-free ELD reaction, adhered to the continuous polymer coating; and A continuous metal coating that completely covers the metal catalyst and the continuous polymer coating, wherein, The continuous metal coating separates from the secondary particles. Wherein, the secondary particles are aggregates of the primary particles of the electrochemically active electrode material, and The polymer coating comprises at least one of an aromatic polyimide, a lithium polyamic acid salt, an alternating monomer unit of a diamine and a dianhydride, and a cross-linked poly(amic acid)amine salt.

2. The electrochemically active electrode material according to claim 1, wherein, The electrochemically active electrode material includes an electrochemically active material for the anode of a lithium-ion battery.

3. The electrochemically active electrode material according to claim 1, wherein, The electrochemically active electrode material comprises graphite powder.

4. The electrochemically active electrode material according to claim 1, wherein, The electrochemically active electrode material comprises graphite mesophase carbon microspheres (MCMB).

5. The electrochemically active electrode material according to claim 1, wherein, The metal coating contains copper.

6. The electrochemically active electrode material according to claim 1, wherein, The metal catalyst contains a noble metal, including one or more of palladium, platinum, rhodium, gold, and silver.

7. The electrochemically active electrode material according to claim 1, wherein, The polymer coating comprises 1-5% by weight of the secondary particles.

8. The electrochemically active electrode material according to claim 1, wherein, The metal coating comprises 5-20% by weight of the secondary particles.

9. The electrochemically active electrode material according to claim 1, wherein, The metal catalyst comprises 0.01-1.0% by weight of the secondary particles.

10. The electrochemically active electrode material according to claim 1, wherein, The thickness of the metal coating is 75-150 nm.

11. The electrochemically active electrode material according to claim 1, wherein, The metal catalyst is discontinuous on the outer surface of the polymer coating, and the areal density of the metal catalyst on the polymer coating is 500-10,000 particles / μm. 2 .

12. The electrochemically active electrode material according to claim 1, wherein, The metal catalyst is continuous on the outer surface of the polymer coating.

13. The electrochemically active electrode material according to claim 1, wherein, The metal coating has a uniform thickness.

14. The electrochemically active electrode material according to claim 1, wherein, The metal coating has a non-uniform thickness, but includes a substantially smooth outer surface, such that the radial distance between the outer surface of the secondary particle and the outer surface of the metal coating is substantially the same around the entire outer surface of the secondary particle.

15. The electrochemically active electrode material according to any one of claims 1 to 14, wherein, The continuous metal coating is formed via an ELD reaction.

16. A coated electrochemically active electrode powder, comprising: Electrochemically active electrode powder particles, comprising secondary particles composed of multiple primary particles of electrochemically active materials; A continuous coating of polymer that is directly coated onto and completely covers the outer surface of the secondary particles, the continuous coating of polymer having a uniform thickness; A metal catalyst coupled to the polymer for catalyzing the electrodeposition-free ELD reaction; as well as A continuous metal coating completely covers the metal catalyst and the polymer, wherein the continuous metal coating is separated from the secondary particles. Wherein, the secondary particles are aggregates of the primary particles of the electrochemically active material, and The polymer comprises at least one of lithium polyamic acid salt and cross-linked poly(amic acid)amine salt.

17. The coated electrochemically active electrode powder according to claim 16, wherein, The electrochemically active electrode powder particles comprise the secondary particles with a diameter of 1-50 μm.

18. The coated electrochemically active electrode powder according to claim 16, wherein, The electrochemically active electrode powder particles are electrochemically active anode materials used in lithium-ion battery anodes.

19. The coated electrochemically active electrode powder according to claim 16, wherein, The electrochemically active electrode powder particles contain graphite.

20. The coated electrochemically active electrode powder according to any one of claims 16 to 19, wherein, The thickness of the continuous coating of the polymer is 50-200 nm.

21. A battery cell comprising an electrode, the electrode comprising a coated electrochemically active electrode material, the coated electrochemically active electrode material comprising powder particles, the powder particles comprising secondary particles composed of a plurality of primary particles of the electrochemically active electrode material and having a polymer coating and a metal coating, the polymer coating and the metal coating being located on the outer surface of the secondary particles, wherein the polymer coating is located between the outer surface of the secondary particles and the metal coating. in, The polymer coating completely covers the outer surface of the secondary particles. The polymer coating has a uniform thickness, and the metal coating is separated from the secondary particles. Wherein, the secondary particles are aggregates of the primary particles of the electrochemically active electrode material, and The polymer coating comprises at least one of an aromatic polyimide, a lithium polyamic acid salt, an alternating monomer unit of a diamine and a dianhydride, and a cross-linked poly(amic acid)amine salt.

22. The battery cell according to claim 21, wherein, The battery unit is a lithium-ion battery unit.

23. The battery cell according to claim 21, wherein, The electrochemically active electrode material comprises graphite or another electrochemically active material used as the anode in a lithium-ion battery cell.

24. The battery cell according to claim 21, wherein, The powder particles also contain a metal catalyst adhered to the polymer coating for catalyzing the electrodeposition ELD reaction of the metal coating on the secondary particles.

25. The battery cell according to any one of claims 21 to 24, wherein, The capacity of the battery cell at a C-rate of 10C is at least 80% of the maximum capacity of the battery cell.

26. A method for metallizing powder particles of an electrochemically active electrode material, comprising: Secondary particles are formed, consisting of multiple primary particles of the electrochemically active electrode material; The outer surface of the secondary particles is coated with a polymer to form a continuous polymer layer having a uniform thickness. A catalyst for the electrodeposition ELD reaction is applied to the polymer, followed by a low-temperature heat treatment in the range of 250°C to 300°C. as well as Metal is deposited on the catalyst and the polymer by electroless deposition to form a continuous metal layer, wherein the continuous metal layer is separated from the secondary particles. Wherein, the secondary particles are aggregates of the primary particles of the electrochemically active electrode material, and The polymer comprises at least one of an aromatic polyimide, a lithium polyamic acid salt, a diamine and a dianhydride alternating monomer units and a crosslinked poly(amic acid)amine salt.

27. The method according to claim 26, wherein, The electrochemically active electrode material contains graphite.

28. The method according to claim 26, wherein, The catalyst includes a metal catalyst, which includes one or more of the following: palladium, platinum, rhodium, gold, and silver.

29. The method according to claim 26, wherein, The metal includes copper.

30. The method according to claim 26, wherein, Coating the outer surface of the secondary particles with the continuous polymer layer comprises one or more of the following: dissolving the polymer in a solvent to form a polymer solution; mixing the polymer solution with an electrochemically active electrode material containing the secondary particles; drying the polymer solution containing the electrochemically active electrode material into a solid; grinding the solid to form powder particles; ball milling the powder particles with a non-solvent; and removing the powder particles from the non-solvent by filtration.

31. The method according to claim 26, wherein, The catalyst is annealed to the polymer after the polymer has been coated onto the secondary particles.

32. The method according to claim 31, wherein, The annealing includes one or more of the following: depositing the catalyst onto the powder particles containing the continuous polymer layer by mixing powder particles containing the secondary particles with a solution containing the catalyst; separating the powder particles from the solution by filtering the powder from the solution; rinsing the powder particles with deionized water; and heating the powder particles containing the continuous polymer layer and the deposited catalyst.

33. The method according to claim 32, wherein, Annealing the catalyst to the polymer further includes mixing the powder particles containing the continuous polymer layer with an alkaline hydroxide solution before mixing the powder particles containing the secondary particles with the solution containing the catalyst.

34. The method according to claim 32, wherein, The solution containing the catalyst includes an aqueous solution of silver nitrate.

35. The method according to claim 26, wherein, Depositing a continuous metal layer on the catalyst and the polymer by electroless deposition (ELD) includes performing an ELD reaction, wherein performing the ELD reaction includes one or more of the following: mixing powder particles containing the secondary particles with a reducing solution, a reducing agent, and a metal-containing solution; separating the powder particles by filtering the powder particles from the mixture of the reducing solution, the reducing agent, and the metal-containing solution; rinsing the powder particles with deionized water; and drying the powder particles to remove the deionized water.

36. The method according to any one of claims 26 to 35, wherein, After the secondary particles have been coated with the continuous polymer layer and after the catalyst has been annealed to the polymer, the continuous metal layer is deposited on the catalyst and the polymer by ELD.

37. A coated electrochemically active electrode powder, comprising: Secondary particles composed of multiple primary particles of electrochemically active materials; Continuous metal coating; A polymer coating with a uniform thickness is located between the outer surface of the secondary particles and the continuous metal coating; and A metal catalyst applied to the polymer coating for catalyzing the electrodeposition-free reaction. in, The polymer coating completely covers the outer surface of the secondary particles. The metal coating completely covers the metal catalyst and the polymer coating, and is separated from the secondary particles. Wherein, the secondary particles are aggregates of the primary particles of the electrochemically active material, and The polymer coating comprises at least one of alternating monomer units of aromatic polyimide, diamine, and dianhydride.

38. The coated electrochemically active electrode powder according to claim 37, wherein, The thickness of the metal coating is less than 150 nm.

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