Conductive material mixtures and layers for manganese-rich cathode electrodes

Abstract

A lithium ion battery having an enhanced electrode structure and a method for forming such an electrode structure are discussed. An electrode assembly includes a precoat layer compressed with a metal current collector, and then a lithium-rich manganese active layer is deposited on the metal current collector and compressed to form the assembly. The disclosed electrode structure reduces internal resistance.

Description

Technical Field

[0001] The present disclosure relates to electrode materials for lithium-ion batteries. Background Art

[0002] Lithium-ion batteries are widely used in various applications. One of the contributing factors to the performance of lithium-ion batteries is the electrode structure, which plays a role in the energy density, power density and cycle life of the battery. In this context, different cathode materials have been investigated to maintain these properties over time. Manganese-rich cathodes have higher internal resistance compared to high-nickel and nickel-cobalt-manganese battery cells. Summary of the invention

[0003] In one aspect, an electrode assembly includes: a current collector; and a slurry of a lithium-rich manganese positive electrode active material, the slurry being interspersed with carbon black, carbon nanotubes, a polymer dispersant configured to spatially exclude particles of the slurry, and a binder configured to adhere the slurry to the current collector after curing. The average secondary particle agglomerate size of the carbon black may be between 5 μm and 50 μm.

[0004] The carbon black in the slurry may also include ultra-high BET carbon black. The slurry may include a ratio of ultra-high BET carbon black to carbon nanotubes in the range of 2:1 to 8:1. The ultra-high BET carbon black may include acetylene black, furnace black, and Ketjen black. The particles of acetylene black may have a particle size of 300 m 2 / g to 500m 2 The Ketjen black particles can be 500m 2 / g to 1,000m 2 The slurry may further include single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0005] The polymer dispersant may also include at least one material selected from the group consisting of polyacrylonitrile (PAV) elastomers and copolymers thereof, polyvinylidene fluoride (PVDF) and modifications thereof, poly(methyl methacrylate) (PMMA), polyacrylates and copolymers thereof, polyethylene oxide and modifications thereof, or other polymer dispersants. The current collector may be a metal foil. The metal foil may be an aluminum foil.

[0006] In another aspect, a battery includes: a current collector; an electrolyte; a separator; and an electrode having a lithium-rich manganese layer, the lithium-rich manganese layer having carbon black, ultra-high BET carbon, a polymer dispersant that spatially facilitates the percolation network of the lithium-rich manganese layer, and a binder configured to adhere the layer to the current collector. The lithium-rich manganese layer of the electrode may also include carbon nanotubes. The lithium-rich manganese layer of the electrode may include a ratio of ultra-high BET carbon black to carbon nanotubes in the range of 2:1 to 8:1. The lithium-rich manganese layer of the electrode also includes a ratio of ultra-high BET carbon black to carbon nanotubes of 6:1.

[0007] The average secondary particle agglomerate size of carbon black can be between 5 μm and 50 μm. The polymer dispersant can include at least one material selected from the group consisting of: polyacrylonitrile (PAV) elastomers and copolymers thereof, polyvinylidene fluoride (PVDF) and modifications thereof, poly(methyl methacrylate) (PMMA), polyacrylates and copolymers thereof, polyethylene oxide and modifications thereof, or other polymer dispersants. The ultra-high BET carbon black can also include acetylene black, furnace black, and Ketjen black. The particles of acetylene black can have a particle size of 300 μm. 2 / g to 500m 2 / g of surface area.

[0008] Another aspect discloses: mixing carbon black, carbon nanotubes, a polymer dispersant configured to sterically exclude particles of the mixture, and a binder to form a slurry; applying the slurry to a current collector; and curing the slurry to the current collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a schematic cross-sectional view of an electrode assembly according to one embodiment of the present disclosure;

[0010] Figure 2 is a schematic cross-sectional view of a slurry layer according to one embodiment of the present disclosure; and

[0011] Figure 3 It is a flow chart of the electrode assembly process. DETAILED DESCRIPTION

[0012] Embodiments are described herein. However, it should be understood that the disclosed embodiments are merely examples and that other embodiments may take different and alternative forms. The drawings are not necessarily drawn to scale. Some features may be enlarged or minimized to show details of particular components. Therefore, the specific structural details and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art.

[0013] The various features shown and described with reference to any one of the accompanying drawings may be combined with features shown in one or more other drawings to produce embodiments not explicitly shown or described. The combinations of features shown provide representative embodiments for typical applications. However, for specific applications or implementations, various combinations and modifications of features consistent with the teachings of the present disclosure may be desired.

[0014] Lithium manganese-rich electrode (LMR) electrodes may have increased internal resistance when in a low state of charge (SOC) region, which can affect cell performance and efficiency. LMR active materials and carbon nanotubes (CNTs), known for their conductive properties, are used to form a slurry layer on the current collector. This slurry combines carbon black, ultra-high surface carbon, carbon nanotubes, and a dispersant. The interfacial resistance of the electrode assembly can be increased by incorporating ultra-high surface area carbon as characterized by the Brunauer, Emmett, and Teller method (BET carbon). The carbon black characterized by this method can be acetylene black (a type of carbon black). The interaction between the pre-coat layer and the cathode can form an interface with reduced surface charge transfer resistance. The dispersant can be a polymer dispersant, which is used to disperse the particles of the slurry in a more uniform manner, thereby providing a more uniform particle distribution. This can also reduce agglomeration. The polymer dispersant uses steric or electrostatic stabilization to help the particles remain well dispersed in the slurry.

[0015] The combination of conductive materials (such as acetylene black and ultra-high BET carbon) with CNTs establishes a conductive layer and reduces the resistance in the cathode electrode. In one embodiment, the LMR cathode can integrate ultra-high BET carbon, acetylene black, dispersants and other conductive materials in specific ratios to achieve increased resistance reduction. This combination can vary depending on the results and production methods.

[0016] In the experimental procedure, samples were prepared for comparison with a nominal LMR cathode electrode. The specific composition of the 3.5Ah LMR soft pack battery sample is a high BET carbon black, carbon nanotubes and dispersant of 6:1:1, respectively. However, the specific composition of the sample can be a high BET carbon black, carbon nanotubes and dispersant between 6:1:0.8 and 6:1:1.2, respectively. The battery cell formation and cycle capacity measurement test evaluates the charge capacity of a sample with a specific composition relative to a comparative LMR sample after electronic charging and discharging. The rate of the charge or discharge current as a fraction of the battery capacity or cycle capacity utilized is expressed in capacity units (C). The results in Table 1 below show that the cycle capacity of the Example 1 sample is increased based on a higher C rate capacity test condition relative to the comparative sample 1.

[0017]

[0018] Table 1: Formation and first cycle capacity test results of 3.5Ah soft pack battery

[0019] In a further experimental procedure, another sample was prepared for comparison with a nominal LMR cathode electrode. The specific composition of the 3.5Ah LMR soft pack cell sample is high BET carbon black, carbon nanotubes and dispersant of 6:1:1, respectively. However, the specific composition of the sample may be high BET carbon black, carbon nanotubes and dispersant between 6:1:0.8 and 6:1:1.2, respectively. A cell internal resistance measurement test was performed, which measures the direct cell internal resistance (DC-IR) at 50% state of charge (SOC). The comparative samples and embodiments were charged and discharged at 1C, which was applied for 10 seconds and after which the internal resistance and output of the samples were measured at room temperature. The results in Table 2 below show that the DC-IR at 50% SOC is lower for the Example 1 sample relative to the comparative sample LMR cell.

[0020]

[0021] Table 2 DC-IR test results of 3.5Ah soft pack battery at 50% SOC

[0022] Now referring to the accompanying drawings, Figure 1 A schematic cross-sectional view of an electrode assembly 10 according to one embodiment of the present disclosure is shown. The electrode assembly 10 has a current collector 12 and a slurry layer 14. The current collector 12 serves as a base layer and may be a metal current collector, which may be an aluminum foil. The slurry layer 14 is deposited onto the current collector 12 and may include carbon nanotubes 16, ultra-high surface carbon black 18, a binder 20, a dispersant 22, and a cathode material 24. The binder 20 (which may be an acrylic acid, such as modified polyvinylidene fluoride (PVDF)) may also include a blend of polymer beads and BaTiO3. The blending ratio of the BaTiO3 particles in the binder 20 may be in the range of about 10% to about 80%. The cathode material 26 may be lithium-rich manganese (LMR) particles that promote primary electrochemical reactions. The ultra-high surface carbon black 18 and carbon nanotubes 16 of the slurry layer 14 may have a weight between 2:1 and 8:1. In some embodiments, the weight ratio of the ultra-high surface area carbon black 18 to the carbon nanotubes 16 in the slurry layer 14 may be 6:1.

[0023] The carbon nanotubes 16 of the slurry layer 14 can include a mixture of single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT). The ratio of the mixture can be determined by the mechanical properties of the application, and MWCNT provides mechanical strength due to its multi-layer concentric cylindrical structure, while SWCNT has a higher conductivity. The different geometric shapes and sizes between SWCNT and MWCNT can make it better dispersed in the doping layer. The ultra-high surface carbon black 18 (commonly referred to as "BET carbon") of the slurry layer 14 is a form of carbon black with a large surface area. The Brunauer, Emmette and Teller (BET) method (a technique for measuring the surface area of ​​porous materials) is used to quantitatively characterize the surface area of ​​this expansion. The surface characteristics of BET carbon are related to its adsorption capacity. Carbon that particularly shows surface characteristics characterized by BET will be referred to as ultra-high BET carbon 18. Ultra-high BET carbon black 18 can be acetylene black, furnace black, Ketjen black or any other suitable form of carbon black. The surface area of ​​ultra-high BET carbon acetylene black 18 is preferably between 300 m 2 / g to 500m 2 / g, and the surface area of ​​the ultra-high BET carbon Ketjen Black 18 is preferably between 500m 2 / g to 1,000m 2 / g.

[0024] The dispersant 22 of the slurry layer 14 can be selected from a class of polymer dispersants, including but not limited to polyacrylonitrile (PAV) elastomers and copolymers thereof, polyvinylidene fluoride (PVDF) and modified substances thereof, poly(methyl methacrylate) (PMMA), polyacrylates and copolymers thereof, polyethylene oxide and modified substances thereof. The dispersant 22 plays a role in the dispersion of the particles of the slurry layer 14. Specifically, the dispersant can control the secondary particle agglomerates to have an average particle size of carbon black between 5 μm and 50 μm. In addition, the dispersant 22 can promote better contact between the particles of the slurry layer 14. This can further promote electron transport during battery operation, which can increase capacity and charge retention. In addition, these dispersants 22 can reduce the sedimentation rate of the particles of the slurry layer 14. The stabilization mechanism adopted by the dispersant 22 mainly includes steric hindrance. The dispersant 22 can also adopt electrostatic repulsion, solvent interaction and other forces, such as hydrogen bonds or van der Waals forces, depending on the specific chemical properties of the dispersant and the particle surface.

[0025] Figure 2A schematic cross-sectional view of a slurry layer 26 is depicted, which includes carbon nanotubes 28, ultra-high surface carbon black 30, a binder 32 (which can be acrylic acid, such as modified PVDF), a dispersant 34, and a cathode material 36. The binder 32 can also include a blend of polymer beads and BaTiO3. The blending ratio of the BaTiO3 particles in the binder 32 is in the range of about 10% to about 80%. The cathode material 36 can be lithium-rich manganese (LMR) particles that promote primary electrochemical reactions. The ultra-high surface carbon black 30 and the carbon nanotubes 28 of the slurry layer 26 can have a weight between 2:1 and 8:1. In some embodiments, the weight ratio of the ultra-high surface carbon black 30 to the carbon nanotubes 28 in the slurry layer 26 can be 6:1.

[0026] The carbon nanotubes 26 of the slurry layer 28 can include a mixture of SWCNT and multi-walled carbon nanotubes MWCNT. The ratio of the mixture can be determined by the mechanical properties of the application, MWCNT provides mechanical strength due to its multi-layer concentric cylindrical structure, and SWCNT has a higher conductivity. The different geometric shapes and sizes between SWCNT and MWCNT can make it better dispersed in the doped layer. Carbon that particularly shows surface properties characterized by BET will be referred to as ultra-high BET carbon 30. Ultra-high BET carbon black 30 can be acetylene black, furnace black, Ketjen black or any other suitable form of carbon black. The surface area of ​​ultra-high BET carbon acetylene black 30 is preferably between 300m 2 / g to 500m 2 / g, and the surface area of ​​the ultra-high BET carbon Ketjen Black 30 is preferably between 500m 2 / g to 1,000m 2 / g.

[0027] The dispersant 34 of the slurry layer 14 can be selected from a class of polymer dispersants 34, including but not limited to PAV elastomers and copolymers thereof, PVDF and modified substances thereof, PMMA, polyacrylates and copolymers thereof, or polyethylene oxide and modified substances thereof. The dispersant 34 plays a role in the dispersion of the particles of the slurry layer 26. Specifically, the dispersant can control the secondary particle agglomerates to have an average particle size of carbon black between 5 μm and 50 μm. In addition, the dispersant 34 can promote better contact between the particles of the slurry layer 26. This can further promote electron transport during battery operation, which can increase capacity and charge retention. In addition, these dispersants 34 can reduce the sedimentation rate of the particles of the slurry layer 26. The stabilization mechanism adopted by the dispersant 34 mainly includes steric hindrance. The dispersant 34 also adopts electrostatic repulsion, solvent interaction and other forces, such as hydrogen bonds or van der Waals forces, depending on the specific chemical properties of the dispersant and the particle surface.

[0028] Reference now Figure 3, a flow chart presents a sequential process in the preparation of an electrode assembly according to one embodiment of the present disclosure. The process begins with frame one 38, where a slurry is prepared. This slurry is a mixture comprising carbon black, carbon nanotubes, a polymer dispersant configured to spatially exclude particles within the mixture, and a binder. In frame two 40, the slurry is then applied directly to the current collector. In frame three 42, the applied slurry undergoes a curing process. Curing is used to attach the slurry to the current collector, thereby producing a cohesive electrode assembly.

[0029] The algorithms, methods or processes disclosed or suggested herein may be capable of being delivered to or implemented by a computer, controller or processing device, which may include any dedicated electronic control unit or programmable electronic control unit. Similarly, the algorithms, methods or processes may be stored in many forms as data and instructions executable by a computer or controller, including but not limited to information permanently stored on a non-writable storage medium such as a read-only memory device and information that can be modified and stored on a writable storage medium such as an optical disk, a random access memory device or other magnetic and optical media. The algorithms, methods or processes may also be implemented as software executable objects. Alternatively, the algorithms, methods or processes may be embodied in whole or in part using suitable hardware components (such as application specific integrated circuits, field programmable gate arrays, state machines or other hardware components or devices) or a combination of firmware, hardware and software components.

[0030] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms covered by the claims. The words used in the specification are words of description rather than limitation, and it should be understood that various changes can be made without departing from the spirit and scope of these disclosed materials.

[0031] As previously described, the features of the various embodiments may be combined to form additional embodiments that may not be explicitly described or shown in the present disclosure. Although various embodiments may have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, it will be appreciated by those of ordinary skill in the art that one or more features or characteristics may be compromised to achieve desired overall system properties, depending on the specific application and implementation. These properties may include, but are not limited to, strength, durability, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, and the like. Therefore, embodiments that are described as being less desirable than other embodiments or prior art implementations with respect to one or more characteristics are within the scope of the present disclosure and may be desirable for a particular application.

[0032] According to the present invention, an electrode assembly is provided, which has: a current collector; and a slurry of lithium-manganese-rich positive electrode active material, the slurry being dispersed with carbon black, carbon nanotubes, a polymer dispersant configured to spatially exclude particles of the slurry, and a binder configured to adhere the slurry to the current collector after curing.

[0033] According to one embodiment, the average secondary particle agglomerate size of the carbon black is between 5 μm and 50 μm.

[0034] According to one embodiment, the carbon black of the slurry comprises ultra high BET carbon black.

[0035] According to one embodiment, the slurry includes a ratio of ultra-high BET carbon black to carbon nanotubes in a range of 2:1 to 8:1.

[0036] According to one embodiment, the ultra-high BET carbon black includes acetylene black, furnace black and Ketjen black.

[0037] According to one embodiment, the particles of acetylene black have a diameter of 300 m 2 / g to 500m 2 / g of surface area.

[0038] According to one embodiment, the particles of Ketjen Black have a diameter of 500 m 2 / g to 1000m 2 / g of surface area.

[0039] According to one embodiment, the slurry includes single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0040] According to one embodiment, the polymer dispersant includes at least one material selected from the group consisting of polyacrylonitrile (PAV) elastomers and copolymers thereof, polyvinylidene fluoride (PVDF) and modifications thereof, poly(methyl methacrylate) (PMMA), polyacrylates and copolymers thereof, polyethylene oxide and modifications thereof or other polymer dispersants.

[0041] According to one embodiment, the current collector is a metal foil.

[0042] According to one embodiment, the metal foil is an aluminum foil.

[0043] According to the present invention, a battery is provided, comprising: a current collector; and an electrode having a lithium manganese-rich layer, wherein the lithium manganese-rich layer has carbon black, ultra-high BET carbon, a polymer dispersant that spatially contributes to the percolation network of the lithium manganese-rich layer, and a binder configured to adhere the lithium manganese-rich layer to the current collector.

[0044] According to one embodiment, the lithium manganese rich layer of the electrode further comprises carbon nanotubes.

[0045] According to one embodiment, the lithium manganese rich layer of the electrode comprises a ratio of ultra-high BET carbon black to carbon nanotubes in a range of 2:1 to 8:1.

[0046] According to one embodiment, the lithium manganese rich layer of the electrode comprises a 6:1 ratio of ultra-high BET carbon black to carbon nanotubes.

[0047] According to one embodiment, the average secondary particle agglomerate size of the carbon black is between 5 μm and 50 μm.

[0048] According to one embodiment, the polymer dispersant includes at least one material selected from the group consisting of polyacrylonitrile (PAV) elastomers and copolymers thereof, polyvinylidene fluoride (PVDF) and modifications thereof, poly(methyl methacrylate) (PMMA), polyacrylates and copolymers thereof, polyethylene oxide and modifications thereof or other polymer dispersants.

[0049] According to one embodiment, the ultra-high BET carbon black includes acetylene black, furnace black and Ketjen black.

[0050] According to one embodiment, the particles of acetylene black have a diameter of 300 m 2 / g to 500m 2 / g of surface area.

[0051] According to the present invention, a method includes: mixing carbon black, carbon nanotubes, a polymer dispersant configured to spatially exclude particles of the mixture, and a binder to form a slurry; applying the slurry to a current collector; and curing the slurry to the current collector.

Claims

1. An electrode assembly, comprising: Current collector; as well as A slurry of lithium-rich manganese positive electrode active material dispersed with carbon black, carbon nanotubes, a polymer dispersant configured to sterically exclude particles of the slurry, and a binder configured to adhere the slurry to the current collector after curing. 2 . The electrode assembly of claim 1 , wherein the average secondary particle agglomerate size of the carbon black is between 5 μm and 50 μm.

3. The electrode assembly of claim 1, wherein the carbon black of the slurry comprises ultra-high BET carbon black.

4. The electrode assembly of claim 3, wherein the slurry comprises a ratio of ultra-high BET carbon black to carbon nanotubes in the range of 2:1 to 8:

1.

5. The electrode assembly of claim 3, wherein the ultra-high BET carbon black comprises acetylene black, furnace black and Ketjen black.

6. The electrode assembly as claimed in claim 5, wherein the particles of acetylene black have a diameter of 300 m 2 / g to 500m 2 / g of surface area.

7. The electrode assembly of claim 5, wherein the particles of Ketjen black have a diameter of 500 m 2 / g to 1000m 2 / g of surface area.

8. The electrode assembly of claim 1, wherein the slurry comprises single-walled carbon nanotubes and multi-walled carbon nanotubes.

9. The electrode assembly of claim 1, wherein the polymer dispersant comprises at least one material selected from the group consisting of polyacrylonitrile (PAV) elastomers and copolymers thereof, polyvinylidene fluoride (PVDF) and modifications thereof, poly(methyl methacrylate) (PMMA), polyacrylates and copolymers thereof, polyethylene oxide and modifications thereof, or other polymer dispersants.

10. The electrode assembly of claim 1, wherein the current collector is a metal foil.

11. The electrode assembly of claim 10, wherein the metal foil is an aluminum foil.

12. A battery comprising: Current collector; as well as An electrode having a lithium-rich manganese layer having carbon black, ultra-high BET carbon, a polymer dispersant that sterically facilitates a percolating network of the lithium-rich manganese layer, and a binder configured to adhere the layer to the current collector.

13. The battery of claim 12, wherein the lithium manganese rich layer of the electrode further comprises carbon nanotubes.

14. The battery of claim 13, wherein the lithium-rich manganese layer of the electrode comprises a ratio of ultra-high BET carbon black to carbon nanotubes in a range of 2:1 to 8:

1.

15. The battery of claim 14, wherein the lithium manganese rich layer of the electrode comprises a ratio of ultra-high BET carbon black to carbon nanotubes of 6:1.

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