Electrodes for energy storage devices

Abstract

The present invention provides electrodes for producing batteries with optimal energy density, power density, and cycle life. [Solution] The electrodes for electrochemical energy storage devices formed by electrostatic deposition utilize composite particles, which include an attached binder and optionally conductive particles, along with active material (AM) particles, formed by sufficient interaction forces between individual component particles to form effective composite particles that can overcome particle separation during electrostatic charging, fluidization, and / or mechanical transport. The secondary binder particles undergo deaggregation to form subparticles attached to the AM particles having a predetermined morphology. Smaller conductive particles, typically carbon black (CB) or similar carbon, bind to the binder and adhere to the AM particles. The result is a composite particle attached to withstand the separation force imposed on the current collector by electrostatic deposition.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority to a U.S. provisional patent application filed on 31 January 2022 and assigned serial number 63 / 304,907 entitled “Electrode for Energy Storage Device,” and a U.S. non-provisional patent application filed on 5 April 2022 and assigned serial number 17 / 713,722 entitled “Electrode for Energy Storage Device.” The entire contents of the aforementioned provisional and non-provisional applications are incorporated herein by reference.

[0002] 1. Technical field This disclosure relates to electrochemical energy devices and related manufacturing methods. The disclosed electrochemical energy devices generally include electrodes, which at least partially include a coating layer formed by depositing dry composite particles onto a conductive substrate by electrostatic deposition. The composite particles include active material particles and binder particles surrounding the active material particles, which are generally formed from the de-aggregation of binder aggregates and adhere to the surface of the active material particles through particle-to-particle adhesion forces. [Background technology]

[0003] 2. Background technology An electrochemical energy storage device has electrodes containing a conductive current collector layer, typically a coating layer communicating with a copper or aluminum sheet. The coating layer may also contain a cathode active material and an anode active material, and is often combined with a conductive material and a binder material to form a structure that readily discharges and receives (is charged) charge in response to an applied electrical load or charging potential. The formation of the electrochemical active material, binder, and conductive particles may vary depending on the chemical properties and production method of the applicable battery.

[0004] Conventional approaches to battery manufacturing use solvent-based approaches to form electrodes. These typically involve binder solutions or suspensions to flow or apply electrochemical active materials and conductive particles onto a conductive current collector foil. Conventional methods generally involve solvents, which impose handling, ventilation, and safety issues, and require drying time due to the evaporation of liquid solvents or for the components within the coated layer to fuse. [Overview of the project] [Problems that the invention aims to solve]

[0005] In general, to produce batteries with optimal energy density, power density, and cycle life, it is desirable to form a coating layer in which electrochemical active material, conductive particles, and binder are uniformly dispersed at a density that promotes electrical communication between the electrochemical active material and the current collector. Improvements are desired in the method of applying the coating layer and in the electrochemical active material formed thereby. These and other objectives are satisfied by the methods and apparatus of the present disclosure. [Means for solving the problem]

[0006] An electrode for an electrochemical energy storage device is provided, formed from an electrostatic deposition process, using a composite particle comprising electrochemically active material (or active material "AM") particles, attached binder particles, and optionally conductive particles, formed by sufficient interaction between individual component particles to form effective composite particles that can overcome / resist the forces separating particles during electrostatic charging and fluidization in the electrostatic deposition process.

[0007] Commercially available binder or conductive materials are generally available in the form of aggregates formed by the physical interaction of multiple primary particles, often referred to as secondary particles. According to this disclosure, binder aggregates undergo deaggregation to form subparticles, which adhere to AM particles having a predetermined and / or desirable morphology. It should be noted that conductive aggregates also form subparticles through deaggregation. Subparticles contain one or more primary particles having a smaller size than the original aggregate. In the formation of the advantageous energy storage devices of this disclosure, binder particles and conductive particles are incorporated in the form of subparticles.

[0008] Typically, according to this disclosure, carbon black (CB) or similar carbon is bound to a binder and adheres to AM particles together with the binder. The result is a composite particle exhibiting sufficient adhesion to withstand the separating forces imposed during the electrostatic deposition process. In a typical electrostatic spray deposition (ESD) process, the composite particles disclosed herein are aerated and fluidized by a gas flow and carried by the gas flow to deposit on a conductive current collector in a uniform pattern and density. Alternative electrostatic deposition approaches may also be used.

[0009] The composite particle layer deposited on the current collector may be further densified according to this disclosure to form electrodes for a battery. The uniformity of the deposited composite particle layer is important for the performance of the resulting battery. The uniformity of the deposited composite particle layer involves, in particular, stoichiometric agreement between the deposited layer and the feed material powder mixture, as well as stoichiometric and morphological agreement within the deposited layer.

[0010] In the battery industry, there is considerable commercial interest in applying electrostatic deposition techniques to form solvent-free electrode coatings for lithium-ion batteries. In particular, ESD technology is attractive because it can significantly reduce energy consumption in the manufacturing process, thereby drastically lowering the cost of battery production. Since the composite electrode powder is directly deposited onto the metal current collector through electrostatic spray deposition, in principle, the use of electrostatic deposition techniques enables simpler and more flexible electrode coating in the manufacture of energy storage devices.

[0011] In conventional applications, electrostatic deposition techniques are widely used in dry powder coating of conductive components. In conventional applications of electrostatic deposition coating techniques, the quality of the coating layer, particularly its uniformity, is directly related to and depends on the properties of the particles contained in the coating powder. These properties include particle size, dielectric constant, conductivity, density, and morphology. According to this disclosure, the properties of the particles related to the coating powder are selected so that the electrostatic deposition coating formed with the disclosed composite particles advantageously promotes / produces uniform electrodes for battery applications.

[0012] The configurations described herein can, advantageously, meet the need for reliable batteries across a wide range of end-use applications, particularly electric vehicles (EVs), where a considerable current draw is imposed to provide sufficient automotive performance. Unfortunately, as mentioned above, conventional approaches to battery manufacturing employ solvent-based approaches to form electrodes. These typically involve binder solutions or suspensions to flow or apply electrochemical active materials and conductive particles onto conductive current collector foil. Conventional methods involve solvents, which impose handling, ventilation, and safety issues, and require drying time due to the evaporation of liquid solvents or for the components within the coated layer to fuse. Therefore, the configurations described herein substantially overcome the aforementioned disadvantages of solvent-based battery formulations by using an electrostatic deposition approach to provide electrodes containing composite particles on a conductive current collector for dry powder applications.

[0013] As disclosed herein, the desired morphology or structure of the composite particles arises from the deaggregation, mixing, and adhesion between component particles to form active material (AM) particles to which a binder and optionally conductive particles are attached in a form that can withstand electrostatic deposition. When deposited on a conductive current collector substrate, the disclosed AM particles form / define the precise load and microstructure for high-performance batteries. It should be noted that "load" is the mass of a unit coating layer over a specific area, typically mg / cm². 2 It is a unit.

[0014] As disclosed herein, advantageous electrodes are formed on a conductive current collector by electrostatic deposition of composite particles, thereby forming a highly effective electrode / electrochemical energy storage device. The disclosed electrode / electrochemical energy storage device generally comprises a plurality of composite particles adapted for electrostatic deposition on a conductive current collector substrate, each composite particle comprising one or more active material particles, binder particles surrounding the active material particles, and conductive particles attached to the binder particles. The disclosed binder particles are generally formed through the deaggregation of binder aggregates to form subparticles. The binder particles adhere to the surface of the active material particles through interaction forces sufficient to withstand the powder mixing process. The interaction is also sufficient to overcome the separation forces caused by the electrostatic deposition process, which is ideal for maintaining the structure of the composite particles when formed on a conductive current collector substrate by electrostatic deposition. [Effects of the Invention]

[0015] The disclosed electrochemical energy storage device and its production method are highly advantageous in providing effective energy storage functionality without requiring a solvent-based manufacturing method.

[0016] Additional features, functions, and benefits of the disclosed electrochemical energy storage device and related manufacturing methods will become apparent from the subsequent detailed description, particularly in conjunction with the accompanying drawings.

[0017] The aforementioned and other features will become apparent from the description of the following specific embodiments illustrated in the accompanying drawings, and similar reference letters in the drawings refer to the same parts throughout the various drawings. The drawings are not necessarily to scale and instead are intended to illustrate the principles of the invention. [Brief explanation of the drawing]

[0018] [Figure 1] This is a diagram of a composite particle, where composite particle 101C represents the composite particle disclosed herein. [Figure 2] FIG. 1 is a diagram showing a context / exemplary system in which the composite particles (composite particle 101C) of FIG. 1 are deployed in an electrochemical energy storage device. [Figure 3A] FIG. 4 is a diagram showing a composition that is an example of the composite particles of FIG. 1. [Figure 3B] FIG. 5 is a diagram showing a composition that is an example of the composite particles of FIG. 1. [Figure 4] FIG. 10 is a diagram showing the progress through the formation of the composite particles of FIGS. 1 to 3B. [Figure 5A] SEM image of the mixed powder for Sample 1. [Figure 5B] SEM image of the mixed powder for Sample 3. [Figure 5C] SEM image of the mixed powder for Sample 4. [Figure 6A] SEM image of a larger area of the mixed powder for Sample 1. [Figure 6B] SEM image of a larger area of the mixed powder for Sample 3. [Figure 6C] SEM image of a larger area of the mixed powder for Sample 4. [Figure 7A] EDS image (nickel mapping) of the mixed powder for Sample 1. [Figure 7B] EDS image (nickel mapping) of the mixed powder for Sample 3. [Figure 7C] EDS image (nickel mapping) of the mixed powder for Sample 4. [Figure 8A] EDS image (fluorine mapping) of the mixed powder for Sample 1. [Figure 8B] EDS image (fluorine mapping) of the mixed powder for Sample 3. [Figure 8C] EDS image (fluorine mapping) of the mixed powder for Sample 4. [Figure 9] A plot showing the bond strength for electrodes prepared by electrostatic spray deposition using powders at various mixing times and speeds according to the present disclosure. [Figure 10]This is an SEM image of composite particles (NCM 622 / PVDF / carbon) deposited on an Al substrate, as disclosed herein. [Figure 11] This is an EDS mapping image of composite particles (NCM 622 / PVDF / carbon) deposited on an Al substrate, showing the distribution of Ni active particles according to this disclosure. [Figure 12] This is an EDS mapping image of composite particles (NCM 622 / PVDF / carbon) deposited on an Al substrate, showing the distribution of carbon particles relative to Ni active particles according to this disclosure. [Figure 13] This is an EDS mapping image of composite particles (NCM 622 / PVDF / carbon) deposited on an Al substrate, showing the distribution of PVDF binder particles relative to Ni active particles according to this disclosure. [Figure 14] This is a plot of resistance versus mixing time for electrodes fabricated by depositing composite particles onto a substrate using ESD. [Figure 15] This is a plot of bonding strength versus mixing time for electrodes fabricated by depositing composite particles onto a substrate using ESD. [Modes for carrying out the invention]

[0019] The following describes exemplary methods and machines for forming and deploying composite particles in electrochemical energy storage devices, such as rechargeable batteries. Other particle deposition approaches may be used to link the composite particles to current collectors or other energy storage devices that store and release electrical energy (electrons) for providing current in a controlled and efficient manner.

[0020] As described herein, the term “particle” generally refers to a granular amount of particulate matter suitable for mixing and interacting with other particles. The morphology of the particles may be spherical or any other form. Examples referring to individual particles are intended to describe the presence of particles, or interactions affecting some or all of them, in a granular amount of particles, including powder and granular forms. It should be further noted that in battery terminology, “active charge material” is often called “electrochemical active material” or “electrode active material.” Electrostatically deposited materials, as disclosed herein, may also be called “coating layers,” depending on the context.

[0021] Particle aggregation often occurs in bulk granular materials, including electrochemical active materials, binder materials, and conductive materials, relating to the manufacture of electrochemical energy storage devices according to this disclosure. All of these materials take the form of particles, which may also be in the form of aggregates, meaning that multiple primary particles interact through relatively weak forces that are broken up through agitation and mixing. In common nomenclature, aggregates refer to secondary particles, which are broken up upon agitation into primary particles or subparticles. The processes and methods discussed herein generally work to form individual primary particles from broken, agitated, or stirred subparticles of aggregates, but the particles as defined herein include primary particles, secondary particles, subparticles of aggregates, and any interactions or bonding between certain types of particles. In other words, clusters of primary particles, often called secondary particles or aggregates, are generally expected to separate upon agitation into smaller particles, but certain aggregates remain intact and can still define particles of the respective active material, binder, or conductive material, meaning those particles and / or any form of their subparticles. Therefore, although particles may be broken down into multiple subparticles, each of them is still a particle. In addition, the force applied during the stirring process may be sufficient to pulverize the aggregated particles.

[0022] Figure 1 is a diagram of the composite particles disclosed herein. The configuration herein applies a solvent-free (dry) electrostatic spray deposition (ESD) coating technique for the manufacture of battery composite electrodes with high uniformity. The disclosure further enables a composite powder mixing process that produces a suitable composite powder mixture for ESD electrode coating. Alternative applications include any electrochemical storage device, such as a fuel cell.

[0023] A battery has a cathode and an anode. In a typical lithium-ion battery, the cathode and anode are based on a composite electrode powder mixture. The composite electrode powder mixture generally contains active electrode material particles (AM), binder material particles (binder), and conductive material particles (CB). Active electrode materials include cathode materials, for example, lithium metal oxide-based cathode materials: NCM (lithium nickel cobalt manganese oxide), LMO (lithium manganese oxide), NCA (lithium nickel cobalt aluminum oxide), LCO (lithium cobalt oxide), and lithium polyanion-type cathode materials: LFP (lithium iron phosphate), LiMn x Fe 1-x PO4, Li2FeSiO4, and carbonaceous anode materials, graphite, Si, Si-based composites, SiO x Examples include lithium alloyable materials or lithium transition metal oxide anode materials. In a typical sodium-ion battery, the cathode material is a sodium transition metal oxide, for example, Na 2 / 3 Fe 1 / 2 Mn 1 / 2O2, sodium polyanion materials such as Na2MnSiO4, Prussian Blue Analogues cathode materials such as Na2MnFe(CN)6. And as anode materials, there are carbonaceous anodes, materials capable of forming alloys with sodium, sodium transition metal oxides or Prussian Blue Analogues anode materials. Transition metal oxide-based cathode materials such as NCM are semiconductors with an electronic conductivity of 10 -6 ~10 -7 S / cm.

[0024] Typical binder materials are polymeric materials such as PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), PEO (polyethylene oxide) or PMMA (poly(methyl methacrylate)), SBR (polystyrene butadiene rubber binder), CMC (carboxymethyl cellulose binder) or PAA (polyacrylic acid), which are electrical insulators. The binder material may also be a polymer electrolyte such as a PEO / lithium triflate polymer electrolyte. Furthermore, the binder may be a solid-state electrolyte composite composed of an inorganic solid electrolyte and a polymeric binder, a polymer electrolyte binder or an organic binder, such as a Li3InCl6 / PMMA composite, an LLZO / polymer electrolyte composite.

[0025] Examples of conductive materials include electrically conductive carbon black (CB), carbon nanotubes or graphene. In addition, some functional additives may be included in the composite electrode. These additives may be, for example, silica, alumina, zirconium oxide or any combination thereof.

[0026] The true density of the cathode material is generally 4–5 g / cc for NCM and 3.6 g / cc for LFP. The true density of the binder is typically in the range of 1–2 g / cc. The typical particle size for the active material is in the range of 1–40 μm. The binder material typically has a primary particle size of 100–1000 nm and an aggregate size of 5–30 μm. The conductive material typically has a primary particle size of 40–80 nm. The conductive current collector is typically Al foil and Cu foil, with or without a prime layer to enhance adhesion between the coated layer and the conductive substrate. Such a primer layer may be applied to the conductive substrate before deposition.

[0027] Referring to Figure 1, the electrodes formed by electrostatic spray deposition (ESD) for an electrochemical energy storage device according to this disclosure include a plurality of composite particles adapted for electrostatic deposition on a conductive current collector substrate. Each of the plurality of composite particles (or at least the majority of composite particles) includes an active material particle and a binder particle surrounding the active material particle. According to this disclosure, the binder particles are formed either by breaking down a binder aggregate into subparticles or by directly introducing pre-fabricated subparticles. In either case, the binder particles adhere to the surface of the active material particles through binding forces greater than the interaction forces that break down during such stirring, based on the forces introduced into the system through stirring of the binder aggregate. Conductive additives may be added to form the composites.

[0028] In Figure 1, particles in range 100 depict cathode materials that serve as an example for electrochemical energy storage devices. In the composite electrode powder mixture, the weight ratio of the active material is typically over 80%, while the weight ratio of the binder and conductive material is less than 20%, in order to enable sufficient gravimetric energy density and acceptable / beneficial power density for the battery. The composite electrode powder mixture is prepared by a mixing process to enable uniform dispersion of the component particles. Figure 1 illustrates several dispersion patterns of component particles 101A, 101B, and 101C in a composite electrode powder mixture thoroughly mixed through dry mixing. The component particles include AM, binder, and conductive particles; however, as will become clear in the following discussion, in some configurations, the conductive material is not required and / or is not included in the composite electrode.

[0029] Generally, AM particles 111 are the largest particles, binder particles 112 are smaller but varied (shown as hatched and shaded), and conductive particles 113 (shown as solid lines) are in the smallest particle size range. However, in certain embodiments, the size and size relationships can vary considerably. In particle 101A, the binder 112 is either large sub-particle size or in the form of aggregates. The active material 111 particles retain their initial morphology during dry mixing. In static powder form, all particles are well dispersed, but there are no strong interactions between AM 111, binder 112, and CB (conductive) particles 113.

[0030] Particle 101B indicates that the binder 112 aggregates are advantageously broken down during the mixing process, and the subparticle size is smaller than that of the active material 111. The active material particles retain their initial morphology during dry mixing. When 101A is used, in the static powder form, particles 111, 112, and 113 may be well dispersed, but there are no strong interaction forces between the AM, binder, and CB particles.

[0031] Particle 101C represents a composite particle where the binder aggregates are broken down during the mixing process, and the size of the subparticles 112 is smaller than that of the active material 111. The active material particles retain their original morphology during mixing. In static powder form, the binder particles and conductive particles are individually coated onto the surface of the active material particles by surface melting, van der Waals forces, or various potential physical interactions and chemical bonding. The composite particle 101C is suitable for electrostatic deposition on a current collector substrate based on the binder subparticles stirred to break down the aggregates, and its interaction forces are sufficient to withstand the separation forces caused by handling of the material, electrostatic deposition on the substrate, and handling after deposition in order to maintain the morphology of the composite particle 101C.

[0032] It should be noted that the significant effect on the binder / active material particle ratio related to the deaggregation of binder particles through the mixing process disclosed herein can be calculated theoretically. Therefore, as shown in Table 1 below, the binder / active material particle ratio increases to 53,819 for an average particle size of 0.1 μm for binder particles, compared to 431 for 0.5 μm binder particles and 54 for 54 μm binder particles. Consequently, the dispersion of binder particles relative to active particles (assuming they are 10 μm) increases by several orders of magnitude according to this disclosure.

[0033] [Table 1]

[0034] A variety of AM particle and composite particle formulations can be achieved. It should be noted that a distinction should be made between AM, binders, and component particles of conductive materials, which are generally obtained as homogeneous bulk granular materials, and composite particles formed for electrostatic deposition by particle-to-particle interaction forces. In example formulations, the active material is formed from transition metal oxides as a cathode material for electrochemical energy storage devices. Typical cathode materials include NCM (lithium nickel cobalt manganese oxide), LFP (lithium iron phosphate), LCO (lithium cobalt oxide), or other suitable formulation chemistry, typically based on their ability to accept and release lithium ions. The cathode material may often be formulated before deposition by a method distinct from that of the bulk material. The active material formed by the disclosed method may also be an anode material for electrochemical energy storage devices. An exemplary application of the active material is for rechargeable batteries, having the chemical properties defined by rechargeable lithium batteries, Li-ion batteries, rechargeable Li-S batteries, solid-state batteries, rechargeable sodium batteries, and sodium-ion batteries. Binder particles are generally formed from one or more polymeric materials, polymer electrolytes, and solid-state electrolyte composites, and the names of several specific compounds are listed above.

[0035] Figure 2 shows a contextual / exemplary system for deploying the composite particles of Figure 1 in a battery. The ESD manufacturing method 200 includes an electrostatic deposition applicator 215 and a hopper 216. The feed material 214 includes a certain bulk amount of the composite particles 101C. The composite particles 101C are generated by a mixer 130 having an agitator 132, or by a similar approach for mixing, combining, and depositing the composite particles 101C. Sources of bulk particles include active material 150-1, binder particles 150-2, and optionally conductive particles 150-3 (generally 150). The feed source 150 is supplied to the mixer 130 in a predetermined amount, generally at least 80% by weight of the active material. The feed source 150 is typically obtained from any suitable commercial or industrial supply as a homogeneous bulk stock and has a granular, particulate, or powdery structure. The particles and powders should be considered interchangeable in the discussion herein.

[0036] After stirring, the binder particles are typically between 200 and 1000 nm, and the conductive particles are between 100 and 500 nm. After stirring, the mixer 130 contains the composite electrode mixture 160 for the feed material 214. The AM particles are typically in the range of 1 to 40 μm and are considerably larger than the attached binder and conductive particles, which will be discussed further below.

[0037] As shown in Figure 2, in the electrostatic deposition apparatus 250, the composite particles shown in Figure 1C are depicted as constituent particles for the cathode material. The active material can be either the cathode material or the anode material, and is formed from either cathode material or anode material particles, respectively. The composite particles from the supply material 214 are aerated and fluidized by a pressurized gas flow, usually dry air. The fluidized composite particles are carried by the gas flow, pass through the electrostatic applicator 215, become charged, move through the electric field, and finally deposit on the grounded conductive current collector 254 to form the composite particle layer 252. The fluidized and carried composite particles are charged in the electrostatic applicator 215 by corona charging or triboelectric charging.

[0038] The product produced by the electrostatic deposition manufacturing method 200 is a coated sheet 253 comprising a composite particle layer 252 and a substrate 254. The electrostatic deposition applicator 215 can be any suitable electrostatic deposition apparatus. Spray treatment is often involved, but other electrostatic deposition approaches may be employed. The coated sheet 253 is densified to form electrodes for an electrochemical energy storage device. The coated sheet 253 can also be preheated before densification. The densification process may or may not be performed under heating. The above process can produce a cathode or anode. The densification process may be repeated, for example, multiple times. For electrostatic charging of the composite particles, the electrostatic applicator can use any suitable electrostatic approach. Examples of electrostatic application include corona charging, triboelectric charging, direct electrode induction charging, or other suitable charging treatments.

[0039] Electrochemical energy storage devices, such as lithium-ion batteries, have a cathode, anode, separator, and electrolyte. The cathode typically includes an active material, such as NCM, a binder material, such as PVDF, and a conductive material, such as carbon black. The anode typically includes an active material, such as graphite, a binder material, such as PVDF or SBR / CMC binder, and / or a conductive material, such as carbon black. The separator is typically a porous polymer film that separates the cathode and anode, allowing ion transport between the cathode and anode. The electrolyte is typically a lithium salt solution, such as a solution of LiPF6 salt and an EC / DMC / EMC solvent, which provides ionic conduction between the cathode and anode.

[0040] In load mode or discharge mode, the anode undergoes oxidation and the cathode undergoes reduction. In charging mode, the anode undergoes reduction and the cathode undergoes oxidation. The energy stored in an electrochemical energy storage device depends not only on the electrochemical energy stored by the active material but also on the content of the active material in the electrodes. Furthermore, the uniformity of the current distribution in the electrochemical energy storage device significantly affects the cycle life of the device. The uniformity of the current distribution is directly related to the uniformity of the electrodes. The structural characteristics of the electrodes, such as porosity and thickness, affect the power capacity of the electrochemical energy storage device.

[0041] Characteristics affected by forming and stacking charged materials include electrode uniformity, amount of active material in the electrodes, electrode porosity, electrical conductivity, electrode processability, power density, and cycle life of the resulting battery, all of which are directly related to energy density.

[0042] In electrostatic processing 200, the charge of the particles is given by the following formula

[0043]

number

[0044] The typical particle size range for cathode materials is 1–40 μm. The typical primary particle size for PVDF binders is 200–300 nm. The typical primary particle size for conductive carbon is 40–50 nm. From the above equation, since the maximum charge of a particle is directly related to the square of the particle radius, the charges of individual powder components in electrostatic deposition will differ by several orders of magnitude.

[0045] Cathode materials typically have a much higher dielectric constant than polymeric binder materials. For example, the dielectric constant of PVDF at 21°C is approximately 8-10, while the dielectric constant of lithium nickel oxide-based cathode materials is on the order of 1000.

[0046] The relaxation time t for charge dissipation from an ideal charged body is: τ = ε0ε r / σ (In the formula, ε r = relative permittivity of powder, and (σ = electronic conductivity of powder) It is given by.

[0047] The electronic conductivity of NCM cathode materials is generally 10 -6 ~10 -7 The value is S / cm, and the PVDF is 10 -14 This is less than S / cm, which results in a difference of several orders of magnitude in the relaxation time for charge dissipation.

[0048] Based on the above analysis, due to significant differences in chargeability and charge dissipation time resulting from differences in conductivity, dielectric constant, particle size, and density, the active material particles, binder particles, and conductive material particles exhibit different electrostatic deposition behaviors during electrostatic deposition.

[0049] In addition, differences in particle size, particle density, morphology, surface roughness, and therefore surface energy will behave differently because they relate to the aerodynamic effects during powder fluidization and mechanical transport to the surface to be coated.

[0050] If there are no strong interaction forces between particles in a mixture, significant separation may occur during coating due to differences in behavior during electrostatic deposition and fluidization, which are related to the properties of the powder. This leads to detrimental effects on the uniformity of the coating in terms of composition, microstructure, and dimensions. Conventional approaches, for example, result in deposited layers 252 with inconsistent stoichiometry due to different deposition patterns originating from individual component particles, starting from the raw material 214.

[0051] In the conventional electrostatic deposition process 200, active material particles, binder particles, and conductive material particles (formed as 101A and 101B) are individually charged when the powder particles pass through a spatially charged zone in a corona-charged, triboelectric, or direct plate electrode electrostatic charging system. Due to differences in chargeability and charge dissipation time, the individual charged particles are deposited on the current collector, resulting in non-uniformity in the deposited layer.

[0052] During the formation of composite particles 101C according to this disclosure, small binder particles and conductive material particles are added / adhered to the surface of the active material particles to form composite particles. During aeration or mechanical transport and deposition of the composite particles, which consist of active material particles with binder and conductive material particles added to their surface, the composite particles become charged and deposited, resulting in uniform deposition on the current collector substrate 254. Furthermore, due to the high resistivity of the binder particles 112, the charge dissipation time of the composite particles is longer than that of pure active material particles, thereby allowing the electrostatic force to be effective during post-coating handling until the binder can be cured. Therefore, the composition of composite particles 101C in the feed material 214 electrode powder mixture is particularly beneficial for electrostatic deposition to achieve a high degree of uniformity.

[0053] Figures 3A and 3B show examples of composite particle compositions in Figure 1. Referring to Figures 1-3A-3B, Figure 3A shows composite particle 101C having AM particles 111 and attached binder particles 112. Figure 3B shows that composite particle 101C further includes conductive particles 113. Depending on the arrangement of the mixer 130, composite particle 101C may be formed by simultaneously mixing the conductive particles 113, active material particles 111 and binder particles 112. In an alternative configuration, composite particle 101C further includes forming composite particle 101C by combining the conductive particles 113 to adhere to the surface of the binder particles 112, and subsequently adhering the combined binder and conductive particles to the surface of the AM particles 111.

[0054] To achieve a composite electrode powder mixture formed of composite particles 101C, any mixing / particle coating equipment, such as an impact mixer or a shear mixer, can be used. Binder aggregates decompose to form subparticles, and conductive material aggregates decompose into smaller particles. These subparticles adhere to the surface of the active material particles by surface melting, van der Waals forces, or various potential physical interactions or chemical bonding, generating sufficiently large interaction forces between individual particles to form effective composite particles that can overcome particle separation during electrostatic charging, fluidization, mechanical transport and / or deposition processes.

[0055] Figure 4 shows the progression through the formation of composite particles (e.g., composite particle 101C) as shown in Figures 1-3B. A key characteristic of mixing and stirring is that, if binder aggregates 112' are present in the raw material source, such aggregates are broken down to form sub-particles 112. Stirring also reduces conductive particles 113' to smaller sub-particles 113 that are better suited to adhesion to AM particles 111. The mixing / stirring disclosed herein is sufficient to break the interaction forces 401 between aggregates and to cause the binder 112 to adhere to the AM particles 111 by a binding force 402 greater than the separation forces encountered through the electrostatic deposition system 200, thereby maintaining the morphology of composite particle 101C and providing a uniform deposition of layer 252.

[0056] The sizes shown in Figure 4 are for illustrative purposes only. In actual production, the size of the binder subparticles 112 is expected to range from 0.1% to 70% of the average size of the active material particles 111. If the average particle size of the active material is greater than 5 μm, it is beneficial if the average subparticle size of the binder is less than 10% of the active material size. If the average particle size of the active material is less than 5 μm, the preferred average subparticle size of the binder is less than 70% of the active material size.

[0057] The granular feed material 150 can be expected to exhibit variability in particle size, and is generally expected to fall within a certain size range, which is normal. As long as the overall range exhibits a typical distribution and average, detached particles outside the range shown herein are unlikely to have a negative effect. Similar distribution ranges can be tolerated for the aggregates and subparticles discussed above, and it cannot be expected that all aggregates / secondary particles will always decompose with strict uniformity.

[0058] The subparticle size of the conductive material is 1 to 100% of the average subparticle size of the binder. Preferably, the subparticle size of the conductive material is less than 30% of the average subparticle size of the binder. Not all of the binder 112 and conductive particles 113 from the constituent particles or component particles will adhere to the active material particles 111. In the electrode powder mixture, more than 50% by weight of binder subparticles should be added to the surface of the active material particles. Preferably, more than 80% by weight of binder subparticles is added to the surface of the active material particles. More than 50% by weight of conductive subparticles is added to the surface of the binder subparticles. Then, more than 50% of binder / conductive composite particles are added to the surface of the active material particles. Preferably, more than 80% by weight of binder and conductive material is added to the surface of the active material particles.

[0059] If the composite electrode mixture does not contain conductive material, binder subparticles are directly attached to the surface of the active material particles.

[0060] The active material powder, binder powder, and / or conductive material powder can be loaded into a mixer and mixed simultaneously. It is preferable to pre-mix the binder and conductive material and then mix them with the active material powder so that the binder and conductive aggregates can be better broken down and the interaction between the binder subparticles and the conductive material can be increased.

[0061] The sizing for some additional particle stocks is as follows: The subparticle size of the conductive material is 1-100% of the average subparticle size of the binder. Preferably, the subparticle size of the conductive material is less than 30% of the average subparticle size of the binder.

[0062] In alternative arrangements, the method for adding / adhering binder / conductive particles to active material particles is not limited to the dry powder mixing described herein. For example, in one exemplary embodiment, binder / conductive material particles may be coated onto active material particles by mixing a suspension or solution of the binder / conductive material with the active material powder. In another exemplary embodiment, binder particles may be coated onto / to the surface of active material particles by a spray drying method.

[0063] In a specific use case, mixer 130 uses a high-shear mixer to agitate an NCM / binder / CB powder mixture having a standard binder subparticle size for electrostatic deposition. The high-shear mixer provides a unique rotating mixing pan with an integrated eccentric mixing tool. The mixing speed can be set within the range of 1 to 30 m / s to disperse and mix particles of different sizes. In this example, an active material (NCM) with a size of approximately 10 μm, a PVDF binder with a primary size of 200 to 300 nm, and conductive carbon with a primary size of 40 to 50 nm were used. AM / binder / CB particles with a weight ratio of 96:2:2 were mixed for 30 minutes using the high-shear mixer. SEM imaging of the mixed particles shows the coating of CB and binder on the surface of the AM. [Examples]

[0064] 1. Material preparation and electrode preparation by electrostatic spray deposition A batch of 700g powder mixture containing heat-treated NMC, PVDF, and carbon black in a weight ratio of 90:7:3 was loaded into a high-shear mixer. Mixing was investigated at different mixing speeds and times (Sample 1: 12 m / s, 10 min; Sample 3: 20 m / s, 20 min; Sample 4: 25 m / s, 20 min).

[0065] The mixed NMC powder was loaded into a hopper in an electrostatic spray deposition system. The dry powder was fluidized by carrying gas under vibration. The fluidized powder was charged with a corona electrostatic spray gun and deposited onto a 15 μm thick grounded Al foil. The coated surface of the Al foil was pre-coated with a PVDF interface layer less than 1 μm thick, applied by the electrostatic spray deposition technique. The deposited sample was heated on a hot plate at 250°C for approximately 1 hour to melt the binder. Finally, the annealed sample was pressed to the desired thickness using a roller press to achieve 35% porosity. This electrode sample is ready for SEM / EDS, adhesion, and electrochemical testing.

[0066] 2. SEM / EDS testing of samples 1, 3, and 4 The mixed powder sample was analyzed by SEM / EDS to evaluate the deaggregation of PVDF / carbon particles and the coating of PVDF / carbon on NMC particles. As shown in Figure 5A, a small aggregate of PVDF / carbon can be observed on the NMC surface, but most of the NMC surface is exposed. The structure of the NMC surface is clearly visible. This indicates that under mixing conditions of 12 m / s for 10 minutes, the NMC surface is barely covered by PVDF / carbon particles.

[0067] As the mixing intensity increases to 20 m / s for 20 minutes (Sample 3, Figure 5B) and 25 m / s for 20 minutes (Sample 4, Figure 5C), the surface of the NMC particles becomes completely covered with PVDF / carbon.

[0068] Figures 6A-6C show larger SEM images of the mixed powder for sample 1 (Figure 6A), sample 3 (Figure 6B), and sample 4 (Figure 6C).

[0069] The corresponding EDS results are shown in Figures 7A (Sample 1, Nickel Mapping), 7B (Sample 3, Nickel Mapping), and 7C (Sample 4, Nickel Mapping), as well as Figures 8A (Sample 1, Fluorine Mapping), 8B (Sample 3, Fluorine Mapping), and 8C (Sample 4, Fluorine Mapping). Elemental mapping images were processed using ImageJ to remove the effect of signal intensity on image quality. The maximum intensity for each element is reported in the image.

[0070] As shown in Figures 7A-7C, the nickel distribution can be perfectly mapped to the corresponding SEM images. The overall shape of individual NMC particles is captured by nickel mapping. The mapping of fluorine, an indicator of PVDF content (Figures 8A-8C), shows the striking differences between the three mixed materials.

[0071] The fluorine mapping image (Figure 8A) after mixing at 12 m / s for 10 minutes does not show an overall spherical shape for the NMC particles. This indicates that most of the PVDF particles remain randomly located in the mixed powder rather than adhering to the NMC particles. The tightly clustered black spot (indicated by the arrow) near the lower left corner of the image also indicates that some aggregates of PVDF particles have not been broken down under low-intensity mixing.

[0072] As shown in the 20 m / s, 20 min (Sample 3, Figure 8B) and 25 m / s, 20 min (Sample 4, Figure 8C) samples, using higher intensity mixing causes fluorine to concentrate, resulting in the spherical shape of NMC particles. The tightly clustered black spot (indicated by the arrow) near the left center of the fluorine mapping for the 20 m / s, 20 min mixture (Sample 3, Figure 8B) indicates a large aggregate of PVDF particles. From the corresponding SEM image in Figure 6B, it can be seen that the NMC particles are behind this large aggregate of PVDF particles, but the PVDF aggregate completely blocks the nickel X-ray spectrum, which is collected by the detector. Therefore, it is shown as space (indicated by the arrow) in the corresponding nickel mapping image. The large PVDF aggregate is not visible in the powder mixed at 25 m / s, 20 min (Sample 4). A relatively uniform distribution of PVDF particles is achieved and is visible in the corresponding fluorine mapping image in Figure 8C.

[0073] 3. Adhesion Test The electrode bonding strength was evaluated using a pull-off test. The electrode sample was cut into a disc shape with a diameter of 14.3 mm. The electrode disc was attached to a flathead tip with a diameter of 12.7 mm using double-sided tape. The disc was attached to the base with double-sided tape with a compressive force of 15 N, and then pulled, and the maximum tensile force that caused the disc to collapse was recorded. Figure 9 is a plot showing the bonding strength for electrodes prepared by electrostatic spray deposition using powder, i.e., samples 1, 3, and 4, at various mixing times and speeds. The plot in Figure 9 shows that samples prepared with longer mixing times demonstrated better adhesion.

[0074] 4. EDS mapping of electrodes In a further exemplary embodiment of the present disclosure, binder particles undergo deaggregation to form the composite particles described above herein, the composite particles are deposited onto an aluminum foil substrate by electrostatic spray deposition, and then subjected to thermal calendering. In this exemplary embodiment, the concentration is 20 mg / cm³. 2The electrode is characterized by composite particles made from NCM 622 / PVDF / carbon having a loading capacity and a density of 3.7 g / cc. The PVDF and carbon interact with the active particles to provide strong adhesion and conductivity.

[0075] As shown in the SEM image in Figure 10, the composite particles exhibit strong adhesion to the Al substrate.

[0076] As shown in the EDS mapping image in Figure 11, the Ni active particles are uniformly distributed and adhere to the Al substrate.

[0077] As shown in the EDS mapping image in Figure 12, the carbon particles are uniformly distributed and adhere to the Ni active particles.

[0078] As shown in the EDS mapping image in Figure 13, the PVDF binder particles are uniformly distributed and adhere to the Ni active particles (based on imaging methods that show fluorine distribution).

[0079] 5. Results of the mixing study A series of tests were conducted to determine the relationship between the mixing conditions related to the formation of composite particles when deposited on a substrate by ESD, and the performance of these composite particles. A batch of 700g powder mixture containing heat-treated NMC, PVDF, and carbon black in a weight ratio of 96:2:2 was loaded into a high-shear mixer. Mixing was investigated using various mixing speeds and mixing times. The resistance across the thickness of the fabricated electrode was measured by placing the electrode disc between two measuring plates.

[0080] As shown in the plot in Figure 14, the resistance related to the composite particles deposited on the substrate (a measure of the uniformity of the carbon distribution of the composite particles deposited on the substrate) shows that a favorable operating window is established for mixing times between approximately 8 and 35 minutes. For mixing times of less than 8 minutes, unacceptably high resistance levels (approximately 33 ohms) were obtained. Significantly longer mixing times (approximately 50 minutes) did not improve the results, but compared to shorter mixing durations, such as approximately 30 minutes, roughly equivalent resistance performance was demonstrated.

[0081] Looking at Figure 15, the binding strength related to the composite particles deposited on the substrate (a measure of the uniformity and effectiveness of the binder distribution for the composite particles deposited on the substrate) shows that a favorable operating window is established for mixing times between approximately 8 and 35 minutes—the same operating window identified by the resistance measurements described above, with reference to Figure 14. For mixing times of less than 8 minutes, unacceptably low binding strength was obtained. Significantly longer mixing times (approximately 50 minutes) did not improve the results, but compared to mixing for shorter durations, e.g., approximately 30 minutes, roughly equivalent average binding strength and a much wider range of performance were demonstrated.

[0082] Based on the test results shown in Figures 14 and 15, a mixing time between approximately 8 and 35 minutes is effective in forming composite particles exhibiting a superior distribution, and in maintaining the adhesion / addition of binder particles and conductive particles to the active particles according to this disclosure.

[0083] The disclosed electrochemical energy storage devices can be incorporated into various assemblies / subassemblies, such as rechargeable lithium batteries, Li-ion batteries, rechargeable lithium-sulfur batteries, solid-state batteries, rechargeable sodium batteries, and / or sodium-ion batteries.

[0084] While the systems and methods defined herein have been shown and described in particular with reference to their embodiments, those skilled in the art will understand that various modifications in form and detail can be made without departing from the scope of the invention as encompassed by the appended claims.

Claims

1. Conductive current collector substrate, One or more electrostatically deposited coating layers are deposited on a conductive current collector substrate and adhere to the conductive current collector substrate. An electrode including, One or more electrostatically deposited coating layers comprise a plurality of dry mixed composite particles, each of which comprises (i) one or more active material particles and (ii) deaggregation binder particles surrounding each of the one or more active material particles. The deaggregated binder particles adhere to the surface of one or more active material particles through interactions sufficient to withstand the mixing involved in the formation of dry composite particles and overcome the separation forces caused by the deposition of one or more electrostatic deposition coating layers on the conductive current collector substrate. This results in an electrode in which the structure of composite particles is maintained when applied to a conductive current collector substrate.

2. The electrode according to claim 1, wherein one or more active material particles function as a cathode material.

3. The electrode according to claim 2, wherein one or more active material particles are selected from (i) lithium polyanion cathode materials containing lithium transition metal oxides, lithium transition metal sulfides, lithium transition metal phosphates, lithium transition metal silicates, or a combination thereof, or (ii) sodium transition metal oxides, sodium polyanion cathode materials, Prussian blue analog cathode materials, or a combination thereof.

4. The electrode according to claim 1, wherein one or more active material particles function as an anode material.

5. One or more active material particles are (i) carbonaceous anode material, graphite, Si, Si-based composite, SiO x The electrode according to claim 4, selected from (ii) a material capable of alloying with lithium, or a lithium transition metal oxide anode material, or a combination thereof, or (ii) an ion intercalation anode material comprising a material capable of alloying with sodium, or a Prussian blue analog anode, and a sodium metal transition metal oxide anode.

6. The electrode according to claim 1, wherein the structure is incorporated into an assembly selected from the group consisting of a rechargeable lithium battery, a Li-ion battery, a rechargeable lithium-sulfur battery, a solid-state battery, a rechargeable sodium battery, and a sodium-ion battery.

7. The electrode according to claim 1, wherein the deaggregated binder particles are formed from one or more polymeric materials, polymer electrolytes, and solid-state electrolyte composites.

8. The electrode according to claim 7, wherein the polymeric material is selected from polyvinylidene fluoride, polytetrafluoroethylene, polyethylene oxide, poly(methyl methacrylate), polystyrene-butadiene rubber binder, carboxymethylcellulose binder, polyacrylic acid, or a combination thereof.

9. The electrode according to claim 1, wherein the dry mixed composite particles further comprises conductive particles attached to at least one surface of one or more active material particles and deaggregated binder particles.

10. The electrode according to claim 9, wherein the conductive particles are selected from the group consisting of carbon black, carbon nanotubes, carbon fibers, graphene, graphite, or a combination thereof.

11. The electrode according to claim 1, wherein the conductive current collector substrate is selected from Al or Cu foil.

12. The electrode according to claim 11, further comprising a prime layer for enhancing adhesion between one or more electrostatic deposition coating layers and a conductive current collector substrate.

13. The electrode according to claim 1, wherein the size of the deaggregated binder particles is between 0.1% and 70% of the average size of one or more active material particles.

14. The electrode according to claim 1, wherein the average size of one or more active material particles is greater than 5 μm, and the average size of the de-aggregating binder particles is less than 10% of the average size of one or more active material particles.

15. The electrode according to claim 1, wherein the average size of one or more active material particles is less than 5 μm, and the average size of the de-aggregating binder particles is less than 70% of the average size of one or more active material particles.

16. The electrode according to claim 1, wherein the dry mixed composite particles further contain conductive particles, and more than 50% of the deaggregated binder particles and conductive particles are attached to one of the active material particles among one or more active material particles.

17. A method for forming electrodes, A process of forming multiple dry mixed composite particles by combining one or more active material particles and de-aggregating binder particles, wherein the de-aggregating binder particles surround each of the one or more active material particles. A process of depositing multiple dry, mixed composite particles onto the surface of a conductive substrate by electrostatic deposition. Methods that include...

18. A process of de-aggregating aggregates of binder material to form de-aggregated binder particles. The method according to claim 17, further comprising:

19. A process of combining conductive particles with one or more active material particles and de-agglutinating binder particles, wherein the conductive particles are attached to the surface of the de-agglutinating binder particles, and Next, the combined binder and conductive particles are attached to the surface of one or more active material particles to form composite particles. The method according to claim 17, further comprising:

20. The method according to claim 17, wherein the electrostatic deposition process is selected from the group consisting of corona-charged electrostatic deposition, triboelectric electrostatic deposition, and direct electrode-induced electrostatic deposition.

21. The method according to claim 17, comprising combining one or more active material particles and a binder material, and stirring the dry mixture thereof to overcome cohesive forces and form deagglomerated binder particles from the binder material, thereby forming deagglomerated binder particles from the binder material, the deagglomerated binder particles adhering to the surface of one or more active material particles to form composite particles having sufficient interaction forces between the deagglomerated binder particles and one or more active material particles to maintain adhesion during electrostatic charging, fluidization and mechanical transport.

22. The method according to claim 21, wherein the stirring provides sufficient force to pulverize the dry mixture.

23. The process of depositing multiple dry, mixed composite particles onto the surface of a conductive substrate includes depositing multiple composite particles onto the conductive substrate in order to form a coating layer having a predetermined amount of active material. The process further includes densifying the coating layer and conductive substrate through a densification treatment selected from the group consisting of (i) preheating the coating layer and conductive substrate and then performing a densification treatment, (ii) preheating the coating layer and conductive substrate and then densifying them under heating, and (iii) densifying the coating layer and conductive substrate under heating. The method according to claim 21.

24. The method according to claim 23, wherein the densification process is repeated.

25. The method according to claim 21, wherein stirring yields deaggregated binder particles of a size between 200 and 1000 nm.

26. The method according to claim 17, wherein the combining step includes combining conductive particles with one or more active material particles and de-aggregating binder particles to form a plurality of dry mixed composite particles, thereby causing the conductive particles to adhere to the de-aggregating binder particles.

27. De-aggregated binder particles are formed from the binder material by combining one or more active material particles and binder material, and by stirring these dry mixtures so as to overcome cohesive forces and form de-aggregated binder particles from the binder material. During stirring and adhesion to the surface of the conductive substrate, the structure of one or more active particles is maintained. De-aggregated binder particles are formed by the dissociation of aggregates of the binder material. The process of combining one or more active material particles and deagglomerating binder particles to form multiple dry mixed composite particles involves stirring the one or more active material particles and deagglomerating binder particles in a solvent-free manner in order to adhere the deagglomerating binder particles and maintain the morphology of the one or more active material particles during stirring. The method according to claim 17.

28. A step of combining de-aggregated binder particles with conductive particles so that the conductive particles adhere to the de-aggregated binder particles, and A process of attaching combined deaggregated binder particles and conductive particles to the surface of one or more active material particles to form a dry mixed composite particle. It further includes, The dry mixed composite particles contain less than 20% by weight of the total conductive particles and de-aggregated binder particles, and the average size of the binder particles is less than 50% of the average active material particle size. The average size of the conductive particles is less than 30% of the average size of the de-aggregated binder particles. The method according to claim 17.

29. The method according to claim 17, further comprising forming an electrode from a conductive substrate to which dried mixed composite particles are attached.

30. The method according to claim 17, further comprising including a conductive substrate to which dried mixed composite particles are attached in a battery.

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