BINDERS FOR ELECTRODES

Abstract

A lithium-ion battery component is presented. The lithium-ion battery component comprises an electrode with a current collector and an electrode foil laminated thereon, which includes conductive agents and a polar crosslinkable copolymer binder of butadiene isomers and acrylonitrile that mechanically binds the conductive agents in a sterically stabilized dispersion and is configured to allow volume expansion of the electrode foil during charging of the electrode and to facilitate volume contraction of the electrode foil during discharging.

Description

FIELD OF TECHNOLOGY

[0001] The disclosure relates to binder materials for lithium-ion batteries. GENERAL STATE OF THE ART

[0002] In lithium-ion batteries, polyvinylidene fluoride (PVDF) has been the material of choice for cathode binders and played a role in electrode formulation. However, PVDF exhibits structural limitations that result in insufficient lithium-ion conductivity, which can be more pronounced in cells with a high-voltage / oxidation chemistry. Additionally, PVDF lacks the necessary functionalities to effectively disperse conductive materials, such as carbon black, carbon nanotubes (CNTs), and their equivalents, within the electrode matrix. This deficiency often requires the inclusion of additional dispersants in the electrode formulation to ensure adequate power delivery and maintain low direct current internal resistance (DC-IR) properties.However, the inclusion of these non-binder-type additives impairs the loading of cathode active materials, ultimately reducing the volumetric energy density of the cell. Given these limitations, there is a need to explore and develop alternative binder materials. SUMMARY

[0003] In one aspect of the disclosure, a lithium-ion battery component is presented. The lithium-ion battery component includes an electrode having a current collector and an electrode foil laminated thereto, including conductive agents and a polar crosslinkable copolymer binder of butadiene isomers and acrylonitrile that mechanically bonds the conductive agents in a sterically stabilized dispersion and is configured to allow volume expansion of the electrode foil during charging of the electrode and facilitate volume contraction of the electrode foil during discharging. At least 50% of the butadiene isomers in the polar crosslinkable copolymer binder may be reduced 1,4-butadiene isomers. In some configurations, 99% of the butadiene isomers in the polar crosslinkable copolymer binder are reduced 1,4-butadiene isomers.Less than 10% of the butadiene isomers in the polar crosslinkable copolymer binder may be unsaturated butadiene isomers. The ratio of acrylonitrile to butadiene isomer may range from 1:0.1 to 1:0.9. The conductive agents may include carbon black. The conductive agents may also include carbon nanotubes. The electrode foil may include lithium- and manganese-rich electrode materials.

[0004] In another aspect of the disclosure, a process is presented. First, a polar crosslinkable copolymer binder of butadiene isomers and acrylonitrile is mixed with conductive agents to create a sterically dispersed mixture. The process continues with the addition of electrode active materials to the mixture and the formation of a self-supporting electrode film. The electrode film is then roll-pressed together with a current collector to form a laminated electrode. The ratio of acrylonitrile to butadiene isomer in the polar crosslinkable copolymer binder can be at least 1:0.2. Less than 10% of the butadiene isomers within the polar crosslinkable copolymer binder can be unsaturated butadiene isomers. At least 50% of the butadiene isomers within the polar crosslinkable copolymer binder can be reduced 1,4-butadiene isomers.An additional step in the process may involve blending the polar crosslinkable copolymer binder with polyvinylidene fluoride. This blending may be in a ratio ranging from 0.001:1 to 1:1, with a ratio of 0.2:1 being preferred.

[0005] In yet another aspect of the disclosure, a lithium-ion battery is presented. The lithium-ion battery includes a separator and a pair of electrodes between which the separator is sandwiched. At least one of the electrodes includes an electrode foil laminated to a current collector and including conductive means and a polar crosslinkable copolymer binder of butadiene isomers and acrylonitrile. This binder mechanically bonds the conductive means in a sterically stabilized dispersion that allows the electrode foil to expand during the battery's charge cycle and contract during discharge. In some configurations, 99% of the butadiene isomers in the polar crosslinkable copolymer binder are reduced 1,4-butadiene isomers. The polar crosslinkable copolymer binder may have a butadiene isomer to acrylonitrile ratio of 1:0.2.The polar crosslinkable copolymer binder can be blended with polyvinylidene fluoride in a ratio of 0.2:1. The conductive agents dispersed in the electrode foil can include carbon black, carbon nanotubes, or both. The electrode foil can include lithium- and manganese-rich electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic representation of a polar crosslinkable copolymer binder and its substituent groups according to one or more aspects of the disclosure; Fig. 2 is a schematic representation of a lithium-ion battery component containing a polar crosslinkable copolymer binder according to one or more aspects of the disclosure; and Fig. 3 is a flow diagram of a manufacturing process according to one or more aspects of the disclosure. DETAILED DESCRIPTION

[0006] Embodiments are described in this specification. It should be understood, however, that the disclosed embodiments are merely examples, and other embodiments may take various and alternative forms. The figures are not necessarily to scale. Some features may be exaggerated or reduced to show details of specific components. Therefore, specific structural and functional details disclosed in this specification are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art.

[0007] Various features illustrated and described with respect to any of the figures may be combined with features illustrated in one or more other figures to produce embodiments not explicitly illustrated or described. The illustrated combinations of features provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of this disclosure may be desirable for particular applications or implementations.

[0008] Unless expressly stated otherwise, all numerical values ​​and ranges relating to amounts, measurements, percentages, weights, and similar numerical references within this document should be understood to be preceded by the term "about." This is true even where the term "about" is not expressly used. All values ​​and ranges are intended to encompass variations that may arise from standard measurement, manufacturing processes, material properties, and the intended functionality of aspects of the disclosure. For example, if a composition according to the description has "5% by weight of a component," this should be understood to mean "about 5% by weight of a component." Furthermore, when numerical values ​​are presented as a range, such as "100 to 200 units," this range should be interpreted to effectively mean "about 100 to about 200 units."Such variations are implicitly included within the scope of the present disclosure.

[0009] Given the limitations of conventional cathode binders such as PVDF in lithium-ion batteries, the disclosure explores alternative binders. In one aspect, the use of copolymers is proposed to increase both lithium-ion conductivity and the dispersion of conductive agents within the electrode matrix. The copolymer binders may comprise two main components: butadiene isomers (component A) and acrylonitrile (component B), each selected for its contribution to the overall performance of the binder.

[0010] Butadiene isomers, which form the main chain 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 the mechanical stresses encountered during battery charge and discharge cycles. Furthermore, the inherent flexibility provided by the butadiene isomers increases the binder's ability to facilitate the uniform dispersion of conductive agents (such as carbon black, CNTs, and other equivalents) as well as cathode active materials within the electrode. This uniform dispersion maintains consistent electrical conductivity across the electrode, which in turn contributes to the overall efficiency and performance of the battery.

[0011] Component B, acrylonitrile, imparts a different set of properties to the copolymer. The presence of a negative dipole in the acrylonitrile units contributes to voltage and oxidation stability, particularly in cells with high-voltage chemistries or cells susceptible to oxidation, such as those incorporating lithium- and manganese-rich (LMR) cathodes. This stability maintains battery performance and lifetime under the conditions required for rapid charging and high power output in applications.

[0012] In another aspect of the disclosure, a polar crosslinkable copolymer binder with a specific ratio of butadiene isomers to acrylonitrile (AB ratio) and a selected percentage of 1,4-butadiene isomers is presented. By tuning the ratio of unsaturated butadiene within the binder, the disclosure addresses poor lithium-ion conductivity and insufficient dispersion of conductive agents and introduces an array of isomeric butadiene structures. These structures increase electrode flexibility, maintain voltage and oxidation stability, and increase the dispersion of conductive agents within an electrode.

[0013] With reference now to Fig. Figure 1 shows a schematic representation of a polar crosslinkable copolymer binder 10. The polar crosslinkable copolymer binder 10 can be incorporated into lithium-ion batteries. This binder combines butadiene isomers 12 in the A group to impart elastomeric flexibility with acrylonitrile 14 in the B group to increase chemical stability and adhesion. In particular, the butadiene component 12 allows the binder to flexibly adapt to volume changes during battery cycling, thereby mitigating potential electrode cracking and increasing overall electrode flexibility. A composition with no more than 10% unsaturated butadiene isomers is preferred for oxidation stability. This formulation promotes the dispersion of conductive agents such as carbon black and CNTs along with cathode active materials for uniform electrical conductivity and electrode integrity.The cathode active materials can be any suitable active materials, such as LMR-based active materials.

[0014] Acrylonitrile 14 is selected for its negative dipole from the CN group, which maintains voltage and oxidation stability. Its strong bonding capabilities with conductive particles increase particle dispersion and adhesion to current collectors, while also enhancing the oxidation resistance of the binder. The formulation can have an A to B ratio in the ranges of 1:0.1 to 1:0.9, with a preferred ratio of 1:0.2. The butadiene component 12 is processed such that reduced 1,4-butadiene isomers constitute at least 50% of the butadiene isomers 12 for a mixture with predominantly unsaturated isomeric forms. In some configurations, it may be preferred that over 99% of the butadiene isomers be 1,4-butadiene isomers. In an electrode formulation, the polar crosslinkable copolymer binder 10 can be used 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 ratio of 0.2:1 being preferred.

[0015] In Fig. 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 includes a separator 18 sandwiched between a pair of electrodes 20 and 22. The electrode 20 includes an electrode foil 24 laminated to a current collector 26 and having conductive agents 28 sterically stabilized by the polar crosslinkable copolymer 10, which mechanically binds the dispersed conductive agents 28 in a sterically stabilized dispersion 30. The sterically stabilized dispersion 30 is configured to allow volume expansion of the electrode foil 24 during charging of the electrode 20 and to facilitate volume contraction of the electrode foil 24 during discharging. While the electrode 20 is shown with the electrode foil 24, the electrode foil may be integrated into one or both electrodes.The conductive means 28 can be carbon black, carbon nanotubes, or any other material with suitable electrochemical properties. The electrode foil 24 contains active materials 32. Depending on the application, the active materials 32 can be either anode or cathode materials, such as lithium or graphite.

[0016] To form the electrode foil 24, the polar crosslinkable copolymer binder 10 is mixed with the conductive agents 28 until the conductive agents 28 are sterically stabilized. Subsequently, the appropriate active materials 32 containing sterically stabilized conductive agents 28 are added to the binder 10 to form an electrode foil 24. Suitable active materials can be LMR-based active materials or other conventional active materials. The conductive agents 28 can be carbon black, CNT, or other equivalents. The active materials 32 can optionally be mixed with other thermoplastic binders, such as PVDF.

[0017] Fig.3 is a flow diagram of a manufacturing process 36 according to one or more embodiments of the disclosure. At step 38, the process 36 includes mixing a polar crosslinkable copolymer binder including butadiene isomers and acrylonitrile with conductive agents to create a sterically dispersed mixture. This step achieves uniform distribution of the conductive agents within the binder. In some configurations, the polar crosslinkable copolymer binder has an acrylonitrile to butadiene isomer ratio of at least 1:0.2, and less than 10% of the butadiene isomers are unsaturated, with at least 50% being reduced 1,4-butadiene isomers. In other configurations, the polar crosslinkable copolymer binder can be blended with PVDF in ratios of 0.001:1 to 1:1, with a ratio of 0.2:1 being preferred.Continuing with step 40, electrode active materials are then added to the previously prepared sterically dispersed mixture. This addition forms a self-supporting electrode film, which is a fundamental component in the structure of an electrode.

[0018] Finally, in step 42, the self-supporting electrode film is roll-pressed together with a current collector. This step forms a laminated electrode, which is a structural element of a lithium-ion battery. The lamination causes the electrode film and the current collector to be integrally bonded, providing mechanical support and electrical connectivity for the functionality of the electrode within a battery. In some configurations, the laminated electrode can be further cured to promote crosslinking through thermal curing, catalytic processes, UV curing, electron beam laser application, or any other suitable method. Thermal curing involves heating the material, which initiates a chemical reaction that results in the crosslinking of polymer chains in the binder.Catalytic curing promotes chemical reactions at lower temperatures or in shorter times compared to thermal curing. UV curing initiates the curing process using ultraviolet light without the need for heat, resulting in rapid crosslinking of the binder.

[0019] Electron beam curing uses high-energy electrons to induce cross-linking, providing fast cure times and the ability to penetrate deep into the material. It's an environmentally friendly option that allows materials to be cured without solvents, producing robust, chemically resistant films. This process is particularly effective when uniform curing across the entire thickness of the material is required.

[0020] While 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 is understood that various changes may be made without departing from the spirit and scope of the disclosed subject matter.

[0021] As previously described, the features of various embodiments may be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments may have been described as providing advantages or being preferred over other prior art embodiments or implementations with respect to one or more desired characteristics, one of ordinary skill in the art will understand that one or more features or characteristics may be compromised to achieve desired overall system attributes depending on the specific application and implementation. These attributes may include, but are not limited to, strength, durability, marketability, appearance, installation, size, serviceability, weight, manufacturability, ease of assembly, etc.Thus, embodiments that are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.

[0022] According to the present invention, a lithium-ion battery component is provided comprising: an electrode having a current collector and an electrode foil laminated thereon, the electrode foil including conductive agents and a polar crosslinkable copolymer binder of butadiene isomers and acrylonitrile that mechanically binds the conductive agents in a sterically stabilized dispersion and is configured to allow volume expansion of the electrode foil during charging of the electrode and to facilitate volume contraction of the electrode foil during discharging of the electrode.

[0023] In one embodiment, at least 50% of the butadiene isomers in the polar crosslinkable copolymer binder are reduced 1,4-butadiene isomers.

[0024] In one embodiment, 99% of the butadiene isomers in the polar crosslinkable copolymer binder are reduced 1,4-butadiene isomers.

[0025] In one embodiment, less than 10% of the butadiene isomers in the polar crosslinkable copolymer binder are unsaturated butadiene isomers.

[0026] According to one embodiment, the ratio of acrylonitrile to butadiene isomer is in the range of 1:0.1 to 1:0.9.

[0027] According to one embodiment, the conductive particles include soot.

[0028] According to one embodiment, the conductive particles comprise carbon nanotubes.

[0029] According to one embodiment, the electrode foil contains lithium- and manganese-rich electrode materials.

[0030] According to the present invention, a method includes: mixing a polar crosslinkable copolymer binder of butadiene isomers and acrylonitrile with conductive agents to form a sterically dispersed mixture; adding an electrode active material to the sterically dispersed mixture to form a self-supporting electrode foil; and roll-pressing the self-supporting electrode foil with a current collector to form a laminated electrode.

[0031] In one aspect of the invention, the polar crosslinkable copolymer binder is prepared with an acrylonitrile to butadiene isomer ratio of at least 1:0.2.

[0032] In one aspect of the invention, less than 10% of the butadiene isomers in the polar crosslinkable copolymer binder are unsaturated butadiene isomers.

[0033] In one aspect of the invention, at least 50% of the butadiene isomers in the polar crosslinkable copolymer binder are reduced 1,4-butadiene isomers.

[0034] In one aspect of the invention, the method involves blending the polar crosslinkable copolymer binder with polyvinylidene fluoride in a ratio ranging from 0.001:1 to 1:1.

[0035] In one aspect of the invention, the ratio of the polar crosslinkable copolymer binder to polyvinylidene fluoride is 0.2:1.

[0036] According to the present invention, there is provided a lithium-ion battery comprising: a separator; and a pair of electrodes between which the separator is interposed, wherein at least one of the electrodes includes an electrode foil laminated with a current collector and having dispersed conductive agents sterically stabilized by a polar crosslinked copolymer of butadiene isomers and acrylonitrile that mechanically binds the dispersed conductive agents.

[0037] In one embodiment, 99% of the butadiene isomers in the polar crosslinkable copolymer are reduced 1,4-butadiene isomers.

[0038] According to one embodiment, the polar crosslinkable copolymer has a ratio of butadiene isomers to acrylonitrile of 1:0.2.

[0039] According to one embodiment, the polar crosslinkable copolymer is mixed with polyvinylidene fluoride in a ratio of 0.2:1

[0040] According to one embodiment, the conductive agents dispersed in the electrode foil include carbon black, carbon nanotubes, or a mixture of both.

[0041] According to one embodiment, the electrode foil contains lithium- and manganese-rich electrode materials.

Claims

[1] Lithium-ion battery component comprising: an electrode comprising a current collector and an electrode foil laminated thereon, the electrode foil including conductive agents and a polar crosslinkable copolymer binder of butadiene isomers and acrylonitrile that mechanically binds the conductive agents in a sterically stabilized dispersion and is configured to allow volume expansion of the electrode foil during charging of the electrode and to facilitate volume contraction of the electrode foil 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 crosslinkable copolymer 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 crosslinkable copolymer 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 crosslinkable copolymer binder are unsaturated butadiene isomers. [5] The lithium-ion battery component according to claim 1, wherein a ratio of acrylonitrile to butadiene isomer is in the range of 1:0.1 to 1:0.

9. [6] The lithium-ion battery component of claim 1, wherein the conductive means comprises carbon black. [7] The lithium-ion battery component of claim 1, wherein the conductive means comprises carbon nanotubes. [8] The lithium-ion battery component of claim 1, wherein the electrode foil includes lithium- and manganese-rich electrode materials. [9] Method comprising: Mixing a polar crosslinkable copolymer binder of butadiene isomers and acrylonitrile with conductive agents to form a sterically dispersed mixture; Adding electrode active materials to the sterically dispersed mixture to form a self-supporting electrode foil; and Roll pressing the self-supporting electrode foil with a current collector to form a laminated electrode. [10] The process of claim 9, wherein the polar crosslinkable copolymer binder is prepared with an acrylonitrile to butadiene isomer ratio of at least 1:0.

2. [11] The process of claim 9, wherein less than 10% of the butadiene isomers in the polar crosslinkable copolymer binder are unsaturated butadiene isomers. [12] The process of claim 9, wherein at least 50% of the butadiene isomers in the polar crosslinkable copolymer binder are reduced 1,4-butadiene isomers. [13] The method of claim 9, further comprising blending the polar crosslinkable copolymer binder with polyvinylidene fluoride in a ratio ranging from 0.001:1 to 1:

1. [14] The process of claim 13, wherein the ratio of the polar crosslinkable copolymer binder to polyvinylidene fluoride is 0.2:

1. [15] Lithium-ion battery, comprising: a separator; and a pair of electrodes between which the separator is inserted, at least one of the electrodes comprising an electrode foil laminated with a current collector and having dispersed conductive agents sterically stabilized by a polar crosslinked copolymer of butadiene isomers and acrylonitrile that mechanically binds the dispersed conductive agents.

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