Binder for electrodes

Abstract

The present disclosure provides a binder for an electrode. A lithium ion battery component is presented. A lithium ion battery component having an electrode with a current collector and an electrode sheet laminated on the current collector, the electrode sheet comprising a conductive agent and a polar crosslinkable copolymerized binder having a butadiene isomer and acrylonitrile, the polar crosslinkable copolymerized binder mechanically binding the conductive agent in a spatially stable dispersion, and is configured to permit volume expansion of the electrode sheet during charging of the electrode and to promote volume shrinkage of the electrode sheet during discharging.

Description

Technical Field

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

[0002] For lithium-ion batteries, polyvinylidene fluoride (PVDF) has been the material of choice for cathode binders and plays an important role in electrode formulations. However, PVDF has structural limitations, which lead to insufficient lithium ion conductivity, which may be more pronounced in high voltage / oxidative cell chemistries. In addition, PVDF lacks the necessary functionality for effectively dispersing conductive materials (such as carbon black, carbon nanotubes (CNTs) and their equivalents) within the electrode matrix. This deficiency typically requires the incorporation of additional dispersants into the electrode formulation to ensure sufficient power output and maintain low direct current internal resistance (DC-IR) characteristics. However, the inclusion of these non-binder type additives impairs the loading of the cathode active material, subsequently reducing the volumetric energy density of the cell. Given these constraints, there is a need to explore and develop alternative binder materials. Summary of the Invention

[0003] In one aspect of the present disclosure, a lithium-ion battery component is provided. The lithium-ion battery component comprises an electrode having a current collector and an electrode sheet laminated thereon. The electrode sheet includes a conductive agent and a polar cross-linkable copolymeric binder comprising butadiene isomers and acrylonitrile. The polar cross-linkable copolymeric binder mechanically binds the conductive agent in a sterically stable dispersion and is configured to permit volume expansion of the electrode sheet during charging and promote volume contraction of the electrode sheet during discharge. At least 50% of the butadiene isomers in the polar cross-linkable copolymeric binder may be reduced 1,4-butadiene isomers. In some configurations, 99% of the butadiene isomers in the polar cross-linkable copolymeric binder may be reduced 1,4-butadiene isomers. Less than 10% of the butadiene isomers in the polar cross-linkable copolymeric binder may be unsaturated butadiene isomers. The ratio of acrylonitrile to butadiene isomers may range from 1:0.1 to 1:0.9. The conductive agent may include carbon black. The conductive agent may also include carbon nanotubes. The electrode sheet may include a lithium-rich manganese electrode material.

[0004] In another aspect of the present disclosure, a method is proposed. Initially, a polar cross-linkable copolymeric binder having butadiene isomers and acrylonitrile is mixed with a conductive agent to produce a spatially dispersed mixture. The method continues by adding electrode active materials to the mixture and forming a self-supporting electrode film. The electrode film is then rolled together with a current collector to form a laminated electrode. The ratio of acrylonitrile to butadiene isomers in the polar cross-linkable copolymeric binder can be at least 1:0.2. Less than 10% of the butadiene isomers in the polar cross-linkable copolymeric binder can be unsaturated butadiene isomers. At least 50% of the butadiene isomers in the polar cross-linkable copolymeric binder can be reduced 1,4-butadiene isomers. An additional step in the method can include blending the polar cross-linkable copolymeric binder with polyvinylidene fluoride. The blending can be carried out in a ratio ranging from 0.001:1 to 1:1, with a preferred ratio being a 0.2:1 ratio.

[0005] In another aspect of the present disclosure, a lithium-ion battery is provided. The lithium-ion battery comprises a separator and a pair of electrodes sandwiching the separator. At least one of the electrodes comprises an electrode sheet laminated with a current collector, the electrode sheet comprising a conductive agent and a polar, cross-linkable copolymeric binder comprising butadiene isomers and acrylonitrile. The binder mechanically bonds the conductive agent in a sterically stable dispersion that allows the electrode sheet to expand during a charge cycle of the battery and to contract during a discharge cycle. In some configurations, 99% of the butadiene isomers in the polar, cross-linkable copolymeric binder are reduced 1,4-butadiene isomers. The polar, cross-linkable copolymeric binder may have a ratio of butadiene isomers to acrylonitrile of 1:0.2. The polar, cross-linkable copolymeric binder may be blended with polyvinylidene fluoride at a ratio of 0.2:1. The conductive agent dispersed within the electrode sheet may comprise carbon black, carbon nanotubes, or both. The electrode sheet may comprise a lithium-rich manganese electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic diagram of a polar cross-linkable copolymeric binder and its substituent groups according to any one or more aspects of the present disclosure;

[0007] Figure 2 is a schematic diagram of a lithium-ion battery component containing a polar cross-linkable copolymeric binder according to any one or more aspects of the present disclosure; and

[0008] Figure 3 is a flow chart of a manufacturing process according to any one or more aspects of the present disclosure. DETAILED DESCRIPTION

[0009] Embodiments are described herein. However, it should be understood that the disclosed embodiments are merely examples and that other embodiments may take various and alternative forms. The drawings are not necessarily drawn to scale. Some features may be exaggerated or minimized to illustrate details of particular components. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching those skilled in the art.

[0010] 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 may be desired consistent with the teachings of this disclosure.

[0011] Unless expressly stated otherwise, all numerical values ​​and ranges relating to quantities, measurements, percentages, weights, and similar numerical references within this document should be understood as being preceded by the term "about." This applies even when the term "about" is not explicitly used. It is intended that all values ​​and ranges encompass variations that may result from standard measurements, manufacturing processes, material properties, and the intended functions of various aspects of this disclosure. For example, when a composition is described as having "5% by weight of a component," it should be understood to mean "about 5% by weight of a component." In addition, when a numerical value is presented as a range such as "100 to 200 units," the range should be interpreted as actually meaning "about 100 to about 200 units." Such variations are implicitly incorporated within the scope of this disclosure.

[0012] Recognizing the limitations presented by traditional cathode binders (such as PVDF) in lithium-ion batteries, the present disclosure explores alternative binders. In one aspect, the use of copolymers is proposed to increase both lithium ion conductivity and the dispersion of the conductive agent within the electrode matrix. The copolymeric binder can have two main components: butadiene isomers (component A) and acrylonitrile (component B), each component being selected for its contribution to the overall performance of the binder.

[0013] The butadiene isomers that form the backbone of component A are selected for their ability to impart elastomeric flexibility to the binder. This flexibility maintains the structural integrity of the electrode under mechanical influences that occur during the charge and discharge cycles of the battery. In addition, the inherent flexibility provided by the butadiene isomers increases the ability of the binder to promote uniform dispersion of conductive agents (such as carbon black, CNTs and other equivalents) and cathode active materials within the electrode. This uniform dispersion maintains consistent conductivity across the electrode, which in turn contributes to the overall efficiency and performance of the battery.

[0014] Component B (acrylonitrile) brings a unique set of properties to the copolymer. The presence of a negative dipole in the acrylonitrile unit contributes to voltage and oxidative stability, particularly in high-voltage or oxidation-sensitive cell chemistries, such as those involving lithium-manganese-rich (LMR) cathodes. This stability maintains battery performance and life under the conditions required for fast charging and high power output in applications.

[0015] In another aspect of the present disclosure, a polar cross-linkable copolymeric binder is provided, which has a specific ratio of butadiene isomers to acrylonitrile (AB ratio) and a selected percentage of 1,4-butadiene isomers. By adjusting the ratio of unsaturated butadiene within the binder, the present disclosure addresses poor lithium ion conductivity and insufficient dispersion of the conductive agent, and introduces a series of butadiene isomeric structures. These structures increase the flexibility, sustaining voltage, and oxidative stability of the electrode, and improve the dispersion of the conductive agent within the electrode.

[0016] Now refer to Figure 1 , a schematic diagram of a polar cross-linkable copolymeric binder 10 is shown. The polar cross-linkable copolymeric binder 10 can be incorporated into lithium-ion batteries. The binder combines a butadiene isomer 12 in the A group for imparting flexibility to the elastomer with an acrylonitrile 14 in the B group for increasing chemical stability and adhesion. Specifically, the butadiene component 12 allows the binder to flexibly adapt to volume changes during battery cycling, thereby mitigating any electrode cracking and increasing overall electrode flexibility. Compositions with no more than 10% unsaturated butadiene isomers are preferred for oxidative stability. The formulation promotes the dispersion of conductive agents (such as carbon black and CNTs) along with cathode active materials to achieve uniform conductivity and electrode integrity. The cathode active material can be any suitable active material, such as an LMR-based active material.

[0017] Acrylonitrile 14 is selected for its negative dipole from the CN group, thereby maintaining voltage and oxidative stability. Its strong adhesion to the conductive particles increases particle dispersion and adhesion to the current collector, while also increasing the oxidation resistance of the binder. The formulation can have a ratio of A to B ranging from 1:0.1 to 1:0.9, with a preferred ratio of 1:0.2. The butadiene component 12 is treated so that the reduced 1,4-butadiene isomers account for at least 50% of the butadiene isomers 12 to achieve a mixture with primarily unsaturated isomers. In some configurations, it may be preferred to have more than 99% of the butadiene isomers be 1,4-butadiene isomers. In the electrode formulation, the polar cross-linkable copolymer binder 10 can be utilized alone or in combination with other binders such as PVDF. For mixed systems, the binder ratio of AB to PVDF can vary from 0.001:1 to 1:1, with a preferred ratio of 0.2:1.

[0018] exist Figure 2 , a lithium-ion battery component 16 is shown. The lithium-ion battery component 16 shown is a lithium-ion battery cell. The lithium-ion battery cell 16 has a separator 18 sandwiched between a pair of electrodes 20 and 22. The electrode 20 has an electrode sheet 24 laminated with a current collector 26, the electrode sheet having a conductive agent 28 that is sterically stabilized by a polar cross-linkable copolymer 10, which mechanically binds the conductive agent 28 dispersed in a sterically stabilized dispersion 30. The sterically stabilized dispersion 30 is configured to permit volume expansion of the electrode sheet 24 during charging of the electrode 20 and to promote volume contraction of the electrode sheet 24 during discharge. Although the electrode 20 is shown with the electrode sheet 24, the electrode sheet can be incorporated into either or both electrodes. The conductive agent 28 can be carbon black, carbon nanotubes, or any other material with suitable electrochemical properties. The electrode sheet 24 includes an active material 32. Depending on the application, the active material 32 can be an anode or cathode material, such as lithium or graphite.

[0019] To form the electrode sheet 24, the polar cross-linkable copolymer 10 is mixed with the conductive agent 28 until the conductive agent 28 is sterically stabilized. A suitable active material 32 is then added to the binder 10 along with the sterically stabilized conductive agent 28 to form the electrode sheet 24. Suitable active materials can be LMR-based active materials or other traditional active materials. The conductive agent 28 can be carbon black, CNTs, or other equivalents. The active material 32 can optionally be mixed with other thermoplastic binders (such as PVDF).

[0020] Figure 3 is a flow chart of a manufacturing method 36 according to one or more embodiments of the present disclosure. At step 38, method 36 involves mixing a polar cross-linkable copolymeric binder comprising butadiene isomers and acrylonitrile with a conductive agent to produce a spatially dispersed mixture. This step achieves a uniform distribution of the conductive agent within the binder. In some configurations, the polar cross-linkable copolymeric binder has a ratio of acrylonitrile to butadiene isomers of at least 1:0.2, and less than 10% of the butadiene isomers are unsaturated, of which a minimum of 50% are reduced 1,4-butadiene isomers. In other configurations, the polar cross-linkable copolymeric binder can be blended with PVDF in a ratio from 0.001:1 to 1:1 (with a preferred ratio of 0.2:1). Proceeding to step 40, the electrode active material is then added to the previously prepared spatially dispersed mixture. This addition forms a self-supporting electrode film, which is a fundamental component in the structure of the electrode.

[0021] Finally, at step 42, the self-supporting electrode film is rolled together with the current collector. This step forms a laminated electrode, which is a structural element of a lithium-ion battery. Lamination causes the electrode film and the current collector to be integrally bonded, thereby providing mechanical support and electrical connection for the function of the electrode within the battery. In some configurations, the laminated electrode can be further cured by thermal curing, a catalytic process, UV curing, electron beam laser application, or any other suitable method to promote crosslinking. Thermal curing involves heating the material, which triggers a chemical reaction that results in crosslinking of polymer chains within the binder. Catalytic curing promotes chemical reactions at lower temperatures or in shorter times than thermal curing. Utilizing ultraviolet light, UV curing triggers the curing process without the need for heating, resulting in rapid crosslinking of the binder.

[0022] Electron beam curing uses high-energy electrons to initiate crosslinking, providing fast cure times and deep penetration into the material. It's an environmentally friendly option that cures materials without solvents, resulting in robust, chemically resistant films. This method is particularly effective when uniform curing across the entire thickness of the material is required.

[0023] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms encompassed 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 disclosures.

[0024] As previously mentioned, features of the various embodiments may be combined to form additional embodiments of the invention that may not be explicitly described or shown. 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 skilled 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 this disclosure and may be desirable for a particular application.

[0025] According to the present invention, a lithium-ion battery component is provided, comprising: an electrode having a current collector and an electrode sheet laminated on the current collector, the electrode sheet comprising a conductive agent and a polar cross-linkable copolymeric binder having butadiene isomers and acrylonitrile, the polar cross-linkable copolymeric binder mechanically binding the conductive agent in a sterically stable dispersion and being configured to permit volume expansion of the electrode sheet during charging of the electrode and to promote volume contraction of the electrode sheet during discharging of the electrode.

[0026] According to an embodiment, at least 50% of the butadiene isomers in the polar crosslinkable copolymeric binder are reduced 1,4-butadiene isomers.

[0027] According to an embodiment, 99% of the butadiene isomers in the polar crosslinkable copolymeric binder are reduced 1,4-butadiene isomers.

[0028] According to an embodiment, less than 10% of the butadiene isomers in the polar crosslinkable copolymeric binder are unsaturated butadiene isomers.

[0029] According to an embodiment, the ratio of acrylonitrile to butadiene isomers ranges from 1:0.1 to 1:0.9.

[0030] According to an embodiment, the conductive agent includes carbon black.

[0031] According to an embodiment, the conductive agent includes carbon nanotubes.

[0032] According to an embodiment, the electrode sheet includes a lithium-rich manganese electrode material.

[0033] According to the present invention, a method includes: mixing a polar cross-linkable copolymeric binder having butadiene isomers and acrylonitrile with a conductive agent to form a spatially dispersed mixture; adding an electrode active material to the spatially dispersed mixture to form a self-supporting electrode film; and rolling the self-supporting electrode film with a current collector to form a laminated electrode.

[0034] In one aspect of the present invention, the polar crosslinkable copolymeric binder is prepared with a ratio of acrylonitrile to butadiene isomers of at least 1:0.2.

[0035] In one aspect of the present invention, less than 10% of the butadiene isomers in the polar crosslinkable copolymeric binder are unsaturated butadiene isomers.

[0036] In one aspect of the present invention, at least 50% of the butadiene isomers in the polar crosslinkable copolymeric binder are reduced 1,4-butadiene isomers.

[0037] In one aspect of the invention, the method includes blending a polar cross-linkable copolymeric binder with polyvinylidene fluoride in a ratio ranging from 0.001:1 to 1:1.

[0038] In one aspect of the present invention, the ratio of polar cross-linkable copolymeric binder to polyvinylidene fluoride is 0.2:1.

[0039] According to the present invention, a lithium ion battery is provided, comprising: a separator; and a pair of electrodes sandwiching the separator, at least one of the electrodes comprising an electrode sheet laminated with a current collector, the electrode sheet having a dispersed conductive agent, the dispersed conductive agent being sterically stabilized by mechanically bonding a polar cross-linkable copolymer having butadiene isomers and acrylonitrile to the dispersed conductive agent.

[0040] According to an embodiment, 99% of the butadiene isomers in the polar crosslinkable copolymer are reduced 1,4-butadiene isomers.

[0041] According to an embodiment, the polar cross-linkable copolymer has a ratio of butadiene isomers to acrylonitrile of 1:0.2.

[0042] According to an embodiment, the polar cross-linkable copolymer is mixed with polyvinylidene fluoride at a ratio of 0.2:1.

[0043] According to an embodiment, the conductive agent dispersed in the electrode sheet includes carbon black, carbon nanotubes,

[0044] tube or a mixture of both.

[0045] According to an embodiment, the electrode sheet includes a lithium-rich manganese electrode material.

Claims

1. A lithium-ion battery component comprising: An electrode having a current collector and an electrode sheet laminated on the current collector, the electrode sheet comprising a conductive agent and a polar cross-linkable copolymeric binder having butadiene isomers and acrylonitrile, the polar cross-linkable copolymeric binder mechanically binding the conductive agent in a spatially stable dispersion and being configured to permit volume expansion of the electrode sheet during charging of the electrode and promote volume contraction of the electrode sheet during discharging of the electrode.

2. The lithium ion battery component of claim 1, wherein at least 50% of the butadiene isomers in the polar cross-linkable copolymeric binder are reduced 1,4-butadiene isomers.

3. The lithium ion battery component of claim 2, wherein 99% of the butadiene isomers in the polar cross-linkable copolymeric binder are reduced 1,4-butadiene isomers.

4. The lithium ion battery component of claim 1, wherein less than 10% of the butadiene isomers in the polar cross-linkable copolymeric binder are unsaturated butadiene isomers.

5. The lithium ion battery component of claim 1, wherein the ratio of acrylonitrile to butadiene isomers ranges from 1:0.1 to 1:0.

9.

6. The lithium ion battery component of claim 1, wherein the conductive agent comprises carbon black.

7. The lithium ion battery component of claim 1, wherein the conductive agent comprises carbon nanotubes.

8. The lithium-ion battery component of claim 1, wherein the electrode sheet comprises a lithium-rich manganese electrode material.

9. A method comprising: mixing a polar cross-linkable copolymeric binder having butadiene isomers and acrylonitrile with a conductive agent to form a spatially dispersed mixture; adding an electrode active material to the spatially dispersed mixture to form a self-supporting electrode film; as well as The self-supporting electrode film and a current collector are rolled to form a laminated electrode.

10. The method of claim 9, wherein the polar crosslinkable copolymeric binder is prepared at a ratio of acrylonitrile to butadiene isomers of at least 1:0.

2.

11. The method of claim 9, wherein less than 10% of the butadiene isomers in the polar crosslinkable copolymeric binder are unsaturated butadiene isomers.

12. The method of claim 9, wherein at least 50% of the butadiene isomers in the polar crosslinkable copolymeric binder are reduced 1,4-butadiene isomers.

13. The method of claim 9, further comprising blending the polar cross-linkable copolymeric binder with polyvinylidene fluoride in a ratio ranging from 0.001:1 to 1:

1.

14. The method of claim 13, wherein the ratio of the polar cross-linkable copolymeric binder to polyvinylidene fluoride is 0.2:

1.

15. A lithium-ion battery comprising: partitions; and A pair of electrodes sandwiching the separator, at least one of the electrodes comprising an electrode sheet laminated with a current collector, the electrode sheet having a dispersed conductive agent, the dispersed conductive agent being sterically stabilized by a polar cross-linkable copolymer of butadiene isomers and acrylonitrile that mechanically bonds the dispersed conductive agent.

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