ANODE ELECTRODE

Abstract

An anode electrode is provided. The anode electrode comprises an anode current collector and an anode active material layer arranged on the anode current collector. The anode active material layer includes an electrochemically active material, a dispersing polymer binder, an adhesive polymer binder, and a conductive filler. The electrochemically active material includes graphite. The dispersing polymer binder exhibits amphiphilic properties, comprising a hydrophobic domain and a hydrophilic domain, which stabilizes hydrophobic carbon particles in water. The adhesive polymer binder has a glass transition temperature that provides flexibility, durability, and cohesive strength between the carbon particles.The conductive filler comprises a conductive carbon that reduces the pore channel and charge transfer resistance at the interface between the binder and the active material.

Description

INTRODUCTION

[0001] The present disclosure relates to battery cells and in particular to anode electrodes formed using an aqueous anode slurry.

[0002] Electric vehicles (EVs), such as battery electric vehicles (BEVs), hybrid vehicles, and / or fuel cell vehicles, comprise one or more electric motors and a battery system with one or more battery cells, modules, and / or packs. A battery control module is used to manage the charging and discharging of the battery system during charging and / or driving. Electric vehicle manufacturers are striving for higher power density to increase the range of electric vehicles.

[0003] Battery cells comprise anode electrodes, cathode electrodes, and separators arranged in a predetermined sequence within a casing. The anode electrodes include an anode current collector and an anode active material layer applied to one or both sides of the anode current collector. The anode active material layer is often applied to the anode current collector as a slurry. However, sometimes the materials of the anode active material layer do not mix well, and the slurry may not adhere satisfactorily to the anode current collector.

[0004] While existing methods and systems attempt to provide an anode electrode with satisfactory electrochemical performance and can fulfill their specific purpose, there is still a need for a new and improved anode electrode. Accordingly, a more efficient and higher-quality anode electrode is required. SUMMARY

[0005] According to several aspects of the present disclosure, an anode electrode is provided. The anode electrode comprises an anode current collector and an anode active material layer arranged on the anode current collector. The anode active material layer comprises an electrochemically active material, a dispersing polymer binder, an adhesive polymer binder, and a conductive filler. The electrochemically active material comprises graphite. The dispersing polymer binder exhibits amphiphilic properties, comprising a hydrophobic domain and a hydrophilic domain that stabilizes hydrophobic carbon particles in water. The adhesive polymer binder has a glass transition temperature that provides flexibility, durability, and cohesive strength between the carbon particles.The conductive filler comprises a conductive carbon that reduces the pore channel and charge transfer resistance at the interface between the binder and the active material.

[0006] According to another aspect of the revelation, the anode electrode contains graphite, which includes natural graphite and / or synthetic graphite.

[0007] According to another aspect of the disclosure, the anode electrode has an electrochemically active material comprising less than 10 wt% silicon (Si), silicon oxide (SiO), lithium silicon oxide (LiSiO), silicon oxide composite (SiO-c), nanostructured silicon (nano-Si) and / or Si contained in a nanocage.

[0008] According to another aspect of the disclosure, the anode electrode contains an electrochemically active material comprising between 94 wt.% and 97 wt.% of the anode electrode.

[0009] According to another aspect of the disclosure, the anode electrode has a binder consisting of a dispersing polymer comprising natriated and / or lithiated carboxymethylcellulose (CMC).

[0010] According to another aspect of the disclosure, the natriated or lithiated carboxymethylcellulose (CMC) has a degree of substitution (DS) of less than 0.8.

[0011] According to another aspect of the disclosure, the natriated or lithiated carboxymethylcellulose (CMC) has a molecular weight of more than 300 kilodaltons (kDa).

[0012] According to another aspect of the disclosure, the natriated or lithiated carboxymethylcellulose (CMC) comprises a mixture of at least a first CMC with a degree of substitution (DS) of 0.7 and a second CMC with a DS of 1.2.

[0013] According to another aspect of the disclosure, the binder consisting of dispersing polymer comprises sotriated or lithiated polyacrylic acid.

[0014] According to another aspect of the disclosure, the natriated or lithiated carboxymethylcellulose (CMC) is between 0.6 wt.% and 2.5 wt.% of the anode electrode.

[0015] According to another aspect of the disclosure, the anode electrode has a binder consisting of an adhesive polymer comprising styrene-butadiene rubber (SBR), styrene-acrylic rubber, nitrile-butadiene rubber and / or copolymers thereof.

[0016] According to another aspect of the disclosure, the anode electrode comprises a binder consisting of an adhesive polymer with a glass transition temperature of less than 20 °C.

[0017] According to another aspect of the disclosure, the anode electrode comprises a binder consisting of adhesive polymer, which is between 1.5 and 3.0 wt.% of the anode electrode.

[0018] According to another aspect of the disclosure, the anode electrode has a conductive filler comprising carbon black, acetylene black, Ketjen black, carbon nanofibers, graphene, graphene nanoplatelets, carbon nanotubes and / or combinations thereof.

[0019] According to another aspect of the disclosure, the anode electrode has a conductive filler comprising between 0.3 wt.% and 1.2 wt.% of the anode electrode.

[0020] According to several aspects of the present disclosure, an anode electrode is provided. The anode electrode comprises an anode current collector and an anode active material layer. The anode active material layer comprises an electrochemically active material consisting of graphite, a dispersing polymer binder, an adhesive polymer binder, and a conductive filler. The dispersing polymer binder exhibits amphiphilic properties, comprising a hydrophobic domain and a hydrophilic domain that stabilizes hydrophobic carbons in water.

[0021] The dispersing polymer comprises a first carboxymethylcellulose (CMC) with a degree of substitution (DS) of 0.7 and a second CMC with a DS of 1.2. The adhesive polymer binder has a glass transition temperature that provides flexibility, durability, and cohesive strength between the carbon particles. The conductive filler comprises conductive carbon, which reduces the pore channel and charge transfer resistance at the interface between the binder and the active material. The conductive filler is present in the anode electrode at a concentration of between 0.3 wt% and 1.2 wt%.

[0022] According to another aspect of the disclosure, the anode electrode has an electrochemically active material comprising natural graphite and / or synthetic graphite.

[0023] According to another aspect of the disclosure, the anode electrode has a binder consisting of an adhesive polymer comprising styrene-butadiene rubber (SBR), styrene-acrylic rubber, nitrile-butadiene rubber and / or copolymers thereof.

[0024] According to another aspect of the disclosure, the anode electrode comprises an electrochemically active material between 94 wt.% and 96 wt.% of the anode electrode, a dispersing polymer binder between 1.4 wt.% and 2.0 wt.% of the anode electrode, an adhesive polymer binder between 2.2 wt.% and 3.0 wt.% of the anode electrode, and a conductive filler between 0.4 wt.% and 1.0 wt.% of the anode electrode.

[0025] According to several aspects of the present disclosure, a method for forming an aqueous graphite anode is provided. The method comprises preparing a slurry for coating an anode current collector with an anode-active material layer and coating the anode current collector with the slurry to form the anode-active material layer arranged on the aqueous graphite anode. The anode-active material layer comprises an electrochemically active material consisting of graphite, a dispersing polymer binder, an adhesive polymer binder, and a conductive filler. The dispersing polymer binder exhibits amphiphilic properties, comprising a hydrophobic domain and a hydrophilic domain that stabilizes hydrophobic carbons in water.The dispersing polymer comprises a first carboxymethylcellulose (CMC) with a degree of substitution (DS) of 0.7 and a second CMC with a DS of 1.2. The adhesive polymer binder exhibits a glass transition temperature that provides flexibility, durability, and cohesive strength between the carbon particles. The conductive filler includes conductive carbon, which reduces the pore channel and charge transfer resistance at the interface between the binder and the active material. The conductive filler comprises between 0.3 and 1.2 wt% of the anode active material layer.

[0026] The above-mentioned features and advantages, as well as further features and advantages of the system and method disclosed herein, are readily apparent from the detailed description, including the claims and examples, in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present disclosure will be better understood with the help of the detailed description and the accompanying drawings, whereby: Fig. 1 An example of a vehicle comprising a battery pack with a plurality of battery cells, illustrated in a perspective view according to the present disclosure, Fig. 2 a battery cell which is in the Fig. 1 battery pack is arranged, as illustrated in a perspective view according to the present disclosure, wherein the battery cell comprises at least one electrode stack with an anode layer using the anode active material disclosed herein, Fig. 3 a graphic representation showing a model carbon dispersion for various dispersing polymer binders used in the anode active material disclosed herein, according to the present disclosure, Fig. 4 shows a graphic representation illustrating the processability of a slurry for various binders consisting of dispersing polymer with a degree of substitution of 0.7, which are used in the anode active material disclosed herein, according to the present disclosure, Fig. 5 shows a graphic representation illustrating the peel strength for different concentrations of adhesive polymers used in the anode active material disclosed herein, according to the present disclosure, Fig. 6 shows a graphic representation illustrating the ion resistance and tortuosity for different concentrations of conductive fillers used in the anode active material disclosed herein, in accordance with the present disclosure, Fig. 7 shows a graphic representation illustrating the ion resistance and tortuosity for different surface areas of conductive fillers used in the anode active material disclosed herein, according to the present disclosure, Fig. Figure 8 shows a flowchart illustrating a process for forming the aqueous graphite anode, which is used in Fig. 2 is shown, illustrated according to the present revelation. DETAILED DESCRIPTION

[0028] Several examples of the revelation, illustrated in the accompanying drawings, will now be discussed in detail. Wherever possible, the same or similar reference symbols will be used in the drawings and the description to refer to identical or similar parts or steps. The following description is merely exemplary and is not intended to limit the present revelation, its application, or its use.

[0029] With reference to Fig. Figure 1 illustrates a vehicle 10 with a battery pack 12 as described in the present disclosure in a perspective view. The battery pack 12 is illustrated with an exemplary vehicle 10. The vehicle 10 is an electric or hybrid vehicle with wheels 11 driven by electric motors / inverters 13. The electric motors / inverters 13 receive energy from the battery pack 12. Although the vehicle 10 is illustrated as a passenger car, it should be noted that the battery pack 12 can also be used for other types of vehicles. For example, the battery pack 12 can be used in watercraft, such as boats, or in aircraft, such as drones or passenger aircraft. Furthermore, the battery pack 12 can be used as a stationary, vehicle-separated, and independent power source. The battery pack 12 includes a container 14 for carrying a plurality of battery cells 18.For example, the battery pack can have 12 fifty or more battery cells 18.

[0030] With the following reference to Fig. 2 is a battery cell 18, which is in the battery pack 12, which is in Fig. Figure 1 shows the arrangement, as illustrated in a perspective view according to one aspect of the present disclosure. Each battery cell 18 has a housing 22 or container and at least one electrode stack 24 comprising a cathode 26, an anode 28, an electrolyte 30, and a separator 31. In some cases, the electrolyte 30 may comprise a solid electrolyte, replacing the liquid electrolyte and separator. Each battery cell 18 may have dozens or hundreds of electrode stacks 24. Each electrode stack 24 is connected to a current collector 32, 34. The electrode stacks are inserted into the housing 22, and the housing 22 is filled with a suitable electrolyte 30. The current collectors 32, 34 are thin metal plates or foils, which are, for example, B. are arranged on both sides of the electrode stack 24 and / or the housing 22 and typically have a thickness between 0.4 and 1 millimeter.The current collectors 32, 34 can be made of copper or aluminum. The current collectors 32, 34 are attached to the electrode stacks 24 to transfer the electric current to an external circuit (not shown).

[0031] With further reference to Fig. 2 The anode electrode 36 comprises an anode current collector 32 and an anode active material layer 38. The anode active material layer 38 comprises a combination of one or more active materials, binders and conductive fillers that optimize the processability and the mechanical and electrochemical properties of the anode electrodes.

[0032] The anode active material comprises electrochemically active materials, e.g., graphite. The graphite can have a variety of geometries, e.g., plate-shaped, rounded, or spherical, as well as combinations thereof. Additionally, the anode active material may contain less than 10 wt% silicon (Si) or lithium silicon oxide (LiSiO₂). x ), silicon oxide (SiO₂) xThe anode active material may include lithium silicon oxide and graphite, silicon oxide and graphite, silicon oxide composite (SiO-c), nanostructured silicon (nano-Si), nanocage silicon, and / or combinations thereof. The anode active material may include graphite, which may further include natural graphite and / or synthetic graphite. Furthermore, the electrochemically active anode material may comprise approximately 94 wt% to 97 wt% (e.g., 94 wt% to 96 wt%) of the anode electrode. In this context, the term "approximately" is well understood among experts. Alternatively, the term "approximately" may also be understood to mean plus or minus 0.1 wt%.

[0033] The anode active material comprises a dispersing polymer binder. This dispersing polymer binder exhibits amphiphilic properties, including a hydrophobic domain and a hydrophilic domain that stabilizes hydrophobic carbons in water. The dispersing polymer binder may include sodium-treated (NaCMC) and / or lithiated (CMC-Li) carboxymethylcellulose (CMC). The dispersing polymer binder may have a low degree of substitution (DS). As illustrated by the model carbon dispersion shown in Fig. As shown in Figure 3, a polymer with a lower DS improves the dispersion of graphite in water and enhances electrochemical performance. For example, NaCMC with a DS of 0.7, which is shown in Fig. As shown in Figure 3, improved dispersion and slurry quality is achieved due to the lower viscosity in Pascal-seconds (Pa-s) at a higher shear rate (1 / second). In one example, the dispersing polymer binder exhibits a degree of substitution of less than 0.8 and preferably a degree of substitution between 0.6 and 0.8.

[0034] The anode active material comprises a dispersing polymer binder to provide sufficient adsorption coverage, which imparts electrostatic stability to the resulting anode slurry. A smooth, homogeneous slurry leads to a fourfold increase in peel strength and increased flexibility of the resulting anode active material on the anode current collector 32. Generally, the dispersing polymer binder comprises between 0.6 wt.% and 2.5 wt.% of the anode active material, depending on the graphite used. As shown in the graphical representation of Fig. As illustrated in Figure 4, the use of NaCMC with a DS of 0.7 at approximately 2.0 wt% provides a more stable anode active material in the form of a slurry. The s-shaped curves shown in Figure 4 illustrate this. Fig. Figure 4 shows signs of agglomeration or the presence of lumps, which is undesirable. For example, the dispersing polymer binder may comprise approximately 1.5 wt% to 2.5 wt% of the anode active material when synthetic or platelet graphite is used. When natural or rounded graphite is used, the dispersing polymer binder may comprise approximately 0.6 wt% to 1.4 wt% of the anode active material. In one example, the anode active material comprises a dispersing polymer binder consisting of 2.0 wt% NaCMC with a degree of substitution of 0.7. In this context, the term "approximately" is well understood among experts. Alternatively, the term "approximately" may also be understood to mean plus or minus 0.1 wt%.

[0035] Furthermore, the dispersing polymer binder can have a high molecular weight to improve the cohesive force between the particles. For example, the dispersing polymer binder can have a molecular weight of more than 300 kilodaltons (kDa).

[0036] The dispersing polymer binder can comprise a mixture of several polymers, each with different properties, to delay or prevent gelation during a drying process. For example, the dispersing polymer binder can include a first polymer with a degree of substitution of 0.7 and a second polymer with a degree of substitution of 1.2. In another example, the dispersing polymer binder can include a first polymer with a molecular weight of approximately 300 kDa and a second polymer with a molecular weight of approximately 400 kDa. In this context, the term "approximately" is well-known among those skilled in the art. Alternatively, the term "approximately" can also be understood to mean plus or minus 10 kDa.

[0037] The dispersing polymer binder can include ionically conductive polyacrylic acid. For example, the polyacrylic acid can be a weakly neutralized lithiated polyacrylic acid or a sodium-treated polyacrylic acid.

[0038] The anode active material comprises an adhesive polymer binder with a low glass transition temperature to provide flexibility, durability, cohesive strength between particles, and adhesion to the current collector. The adhesive polymer binder can typically be used as a partially crosslinked particle stabilized in water by a surfactant. Examples of adhesive polymer binders include styrene-butadiene rubber (SBR), styrene-acrylic rubber, nitrile-butadiene rubber, or combinations thereof. The adhesive polymer binder has a low glass transition temperature, e.g., less than 20 °C. The adhesive polymer binder can comprise between approximately 1.5 wt% and 3.0 wt% (e.g., 2.2 wt% and 3.0 wt%) of the anode active material. As shown in the graphical representation of Fig. As shown in Figure 5, increasing the SBR content by 2.0 wt.% to 2.8 wt.% improves the durability of the coating of the anode active material on the anode current collector 32, as indicated by an increased peel strength in Newtons per meter (N / m). In this context, the term "approximately" is well-known among experts. Alternatively, the term "approximately" can also be understood to mean plus or minus 0.1 wt.%.

[0039] The anode active material comprises a conductive filler or conductive carbon additive combined with the anode active material, the dispersing polymer, and the adhesive polymer. The conductive filler or conductive carbon reduces both the pore channel resistance and the charge transfer resistance at the interface between the binder and the active material. Fig. Figure 6 illustrates that a higher proportion of industrial carbon black (wt%) leads to a lower ion resistance in ohm-centimeters squared (Ωcm). 2 ) leads. Fig. Figure 7 illustrates that formulations of the anode active material that increase the carbon content (e.g., 65 m) 2 / g and 140 m 2 / g), improved ion resistance compared to carbon with a smaller surface area (45 m²) 2 / g). The conductive filler may include carbon black (CB), acetylene black, Ketjen black, carbon nanofibers, graphene, graphene nanoplatelets, carbon nanotubes, multi-walled carbon nanotubes, single-walled nanotubes, and / or combinations thereof. In one example, the conductive filler may comprise and be between approximately 0.3 wt% and approximately 1.2 wt% (e.g., 0.4 wt% and 1.0 wt%) of the anode electrode. In another example, the conductive filler may be between approximately 0.5 wt% and approximately 1.0 wt% of the anode electrode. In this context, the term "approximately" is well understood among experts. Alternatively, the term "approximately" may also be understood to mean plus or minus 0.1 wt%.

[0040] With reference to Fig. Section 8 presents a method 100 for forming an anode electrode according to the present disclosure. The method begins in block 102.

[0041] Block 102 shows the preparation of a slurry for coating an anode current collector with an anode active material layer. The anode active material layer comprises the graphite-containing electrochemically active material, the dispersing polymer binder, the adhesive polymer binder, and the conductive filler. The dispersing polymer binder exhibits amphiphilic properties, comprising a hydrophobic domain and a hydrophilic domain that stabilizes hydrophobic carbons in water. The dispersing polymer binder includes a first carboxymethylcellulose (CMC) with a degree of substitution (DS) of 0.7 and a second CMC with a DS of 1.2. The conductive filler comprises a conductive carbon that reduces the pore channel and charge transfer resistance at the interface between the binder and the active material. The conductive filler is present in a concentration between 0.3 wt% and 1.2 wt%.-% of the anode electrode. Preparing the slurry can involve combining the anode active material, the dispersing polymer binder, the adhesive binder, and the conductive filler with water, for example, in a tank with a mixer such as a screw mixer. Carbon and carbon-coated particles, such as the graphite of the anode active material, are generally hydrophobic and tend to agglomerate in water-based solutions rather than remain as individual particles; furthermore, they exhibit low cohesive force, which causes cracking and flaking when applied to an anode current collector.The resulting slurry, however, maximizes processability, slurry quality, dispersion quality, and the mechanical integrity of the anode electrode due to the combination of the anode active material components disclosed herein, thereby providing satisfactory electrochemical performance. The process then proceeds to Block 104.

[0042] Block 104 shows the coating of the anode current collector with the slurry to form the anode active material layer on the aqueous graphite anode. Coating the anode current collector may involve spreading or pouring the slurry onto a surface of the anode current collector, for example, using a doctor blade, a slot nozzle coater, or another suitable coating technique.

[0043] The anode electrode and the method disclosed herein are advantageous and beneficial compared to the prior art. The anode active material used in the anode electrode disclosed herein provides a water-based formulation for a robust, high-quality graphite-based electrode. The combination of materials enables improved slurry and electrode quality, mechanical durability, lower electrode internal resistance, and high electrochemical performance. The formulation described herein ensures the stability of the anode active material slurry without agglomeration or clumping, or flaking or cracking, when the anode active material slurry is applied to the current collector.The dispersing polymer binder used in the formulation, with its lower degree of separation, improves the dispersion of graphite in water and enhances electrochemical performance. The concentration of this dispersing polymer binder provides sufficient adsorption coverage, imparting electrostatic stability to the resulting anode-active material slurry. Furthermore, the resulting smooth and homogeneous slurry leads to increased peel strength and greater flexibility of the anode-active material layer. Additionally, the adhesive polymer binder ensures the coating's durability, while the conductive filler improves pore channel tortuosity and reduces ion resistance.

[0044] This description is for illustrative purposes only and is not intended to limit the disclosure, its application, or its use in any way. The comprehensive teachings of the disclosure can be implemented in a whole range of forms. Although this disclosure includes certain examples, the true scope of the disclosure should therefore not be limited to them, since other modifications will become apparent upon study of the drawings, the patent specification, and the following claims.

Claims

[1] Anode electrode, comprising: an anode current collector and an anode active material layer arranged on the anode current collector, the anode active material layer comprising the following: an electrochemically active material that includes graphite, a binder consisting of a dispersing polymer, exhibiting amphiphilic properties comprising a hydrophobic domain and a hydrophilic domain, which stabilizes hydrophobic carbons in water, a binder consisting of an adhesive polymer with a glass transition temperature that provides flexibility, durability and cohesive strength between the carbon particles, and a conductive filler comprising a conductive carbon that reduces the pore channel and charge transfer resistance at the interface between binder and active material. [2] Anode electrode according to claim 1, wherein the graphite comprises natural graphite and / or synthetic graphite. [3] Anode electrode according to claim 1, wherein the electrochemically active material comprises less than 10 wt% silicon (Si), silicon oxide (SiO), lithium silicon oxide (LiSiO), silicon oxide composite (SiO-c), nanostructured silicon (nano-Si) and / or Si contained in a nanocage. [4] Anode electrode according to claim 1, wherein the electrochemically active material comprises between 94 wt.% and 97 wt.% of the anode electrode. [5] Anode electrode according to claim 1, wherein the binder consisting of dispersing polymer comprises sotriated and / or lithiated carboxymethylcellulose (CMC). [6] Anode electrode according to claim 5, wherein the natriated or lithiated carboxymethylcellulose (CMC) has a degree of substitution (DS) of less than 0.

8. [7] Anode electrode according to claim 5, wherein the natriated or lithiated carboxymethylcellulose (CMC) has a molecular weight of more than 300 kilodaltons (kDa). [8] Anode electrode according to claim 5, wherein the natriated or lithiated carboxymethylcellulose (CMC) comprises a mixture of at least a first CMC with a degree of substitution (DS) of 0.7 and a second CMC with a DS of 1.

2. [9] Anode electrode according to claim 5, wherein the binder consisting of dispersing polymer comprises sotriated or lithiated polyacrylic acid. [10] Anode electrode according to claim 5, wherein the natriated or lithiated carboxymethylcellulose (CMC) is between 0.6 wt.% and 2.5 wt.% of the anode electrode.

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