Double layer battery adhesive structure

Abstract

The present disclosure provides a "dual layer battery binder structure". A heterogeneous binder electrode assembly and method of forming an electrode for a lithium ion battery is presented. The heterogeneous binder electrode assembly includes: a metal foil current collector; a non-porous layer adhered to the current collector, the non-porous layer including active material particles, a conductive agent, and a binder system including carboxymethyl cellulose and styrene butadiene rubber; and a carboxymethyl cellulose porous layer bonded to the non-porous layer to increase electrolyte permeation and ion transport.

Description

Technical Field

[0001] This disclosure relates to battery manufacturing. Background Technology

[0002] Achieving high power performance in lithium-ion batteries requires a balance between ionic and electrical conductivity, mechanical integrity, and electrolyte permeation into the anode. Conventional single-layer coatings typically optimize one or both of these properties. Mechanical strength can be maintained using electrically insulating binders such as carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR). Summary of the Invention

[0003] An electrode assembly is provided. The electrode assembly includes: a metal foil current collector; a non-porous layer adhered to and in direct contact with the metal foil current collector, the non-porous layer comprising active material particles, a conductive agent, and a binder system containing carboxymethyl cellulose and styrene-butadiene rubber; and a carboxymethyl cellulose porous layer bonded to the non-porous layer, the porous layer facilitating electrolyte permeation and ion transport. The active material particles are selected from natural graphite, artificial graphite, silicon dioxide, or silicon-carbon composites. The porous layer may have a porosity of 40% to 70%, while the non-porous layer may have a thickness of 10 micrometers to 30 micrometers, and the porous layer may have a thickness of 5 micrometers to 15 micrometers. The porous layer may further include a conductive agent to increase electronic conductivity, and the binder system in the non-porous layer may have a carboxymethyl cellulose to styrene-butadiene rubber weight ratio between 1:1 and 3:1. The porous layer may also contain aligned pores to facilitate ion transport. The metal foil current collector may be copper.

[0004] A method for forming an electrode is provided. The method includes: applying a mixed binder slurry containing active material particles, a conductive agent, and a mixture of carboxymethyl cellulose and styrene-butadiene binder to a metal foil current collector; drying the mixed binder slurry to form a non-porous layer adhered to the metal foil current collector; applying a carboxymethyl cellulose slurry on top of the non-porous layer; and drying the carboxymethyl cellulose slurry to form an electrode. The method may further include calendering the non-porous layer to achieve a target density before applying the carboxymethyl cellulose slurry. The carboxymethyl cellulose slurry can be applied by blade coating, and the mixed binder slurry can be dried at a temperature between 80°C and 120°C. The metal foil current collector can be pretreated to increase the adhesion of the non-porous layer. The method may further include adding a surfactant to the carboxymethyl cellulose slurry and incorporating a silicon-based composite as active material particles in the mixed binder slurry and the carboxymethyl cellulose slurry. Additionally, the method may include annealing the electrode at a temperature between 150°C and 250°C after forming the porous layer to increase layer adhesion.

[0005] A negative electrode is provided. The electrode comprises a current collector foil and a styrene-butadiene rubber (SBR) layer, the SBR layer being sandwiched between and laminated with the current collector foil and a carboxymethyl cellulose and SBR binder matrix containing an active material. The thickness of the SBR layer can be between 1 micrometer and 5 micrometers, and the active material can be a blend of natural graphite and artificial graphite in a weight ratio of 2:1 to 3:1. Attached Figure Description

[0006] Figure 1 This is a schematic diagram of a homogeneously coated electrode;

[0007] Figure 2 This is a schematic diagram of a heterogeneous coated electrode;

[0008] Figures 3 to 6 It is a graph showing the electrochemical performance characteristics of a homogeneous coated electrode compared to a heterogeneous coated electrode; and

[0009] Figure 7 This is a flowchart of the process of forming a heterogeneous coated electrode. Detailed Implementation

[0010] According to this disclosure, a detailed embodiment of a heterogeneous binder anode assembly for lithium-ion batteries is provided, including the structural, compositional, and functional advantages of a two-layer coating system. The bottom layer comprises a dual binder composition of CMC and SBR to maintain adhesion and mechanical integrity, while the top layer has a single CMC binder to increase porosity, electrolyte permeability, and electrical conductivity. These embodiments represent an innovative approach to resolving the trade-offs between mechanical strength, conductivity, and wettability inherent in conventional single-layer anode coatings. The accompanying drawings and descriptions are illustrative and highlight key aspects of the layered binder system and its performance benefits. Certain features may be emphasized or simplified to clarify these aspects, and for this purpose, the specific structural and operational details are not intended to limit the invention but rather to provide guidance to those skilled in the art for implementing various embodiments of the claimed invention. This disclosure is contemplated and intended to cover variations in composition, structure, and configuration that remain within the scope of the invention.

[0011] Unless otherwise expressly stated, all numerical values ​​and ranges in this document, including dimensions, measurements, percentages, weights, layer thicknesses, and similar numerical references, should be interpreted as preceded by the term "about". Even where "about" is not specifically mentioned, this interpretation applies throughout the disclosure to account for typical variations in measurements, manufacturing tolerances, material properties, and intended functionality. For example, when the subbase loading is stated as "0.5 to 3 mg / cm³",... 2 When it says "", it should be understood as "approximately 0.5 to approximately 3 mg / cm³". 2Similarly, if the porosity of the top layer is described as "increased to facilitate electrolyte permeation," this includes reasonable variations to achieve the intended functionality. These inherent variations are included within the scope of this invention, thereby ensuring practical implementation and adaptability across different manufacturing scenarios.

[0012] This disclosure relates to a heterogeneous binder coating system for graphite-based anodes in lithium-ion batteries. The heterogeneous binder coating system uses a dual binder composition of CMC and SBR in the underlayer to achieve strong adhesion and mechanical integrity, while utilizing a single CMC binder in the top layer to increase porosity, electrolyte permeability, and electrical conductivity. The underlayer, applied directly to the current collector, provides adhesion and structural support. The inclusion of SBR in this layer imparts elasticity, thereby reducing the chance of delamination during cycling, while maintaining sufficient mechanical strength in combination with CMC.

[0013] Using only CMC in the top layer overcomes the limitations of the bottom layer by increasing porosity and promoting faster and more uniform electrolyte penetration. The absence of insulating SBR polymer in the top layer also increases electrical conductivity, thereby reducing anode resistance and improving high-rate performance. This layered configuration balances the benefits of both binders, thereby tuning the ionic and electrical conductivity, mechanical stability, and efficient electrolyte penetration of the anode.

[0014] The proposed system offers several performance advantages over conventional homogeneous coatings. The layered configuration improves both ion and electron transport by combining the mechanical strength of the underlayer with the increased conductivity and wetting properties of the top layer. The dual-binder underlayer prevents delamination, thus maintaining long-term mechanical stability even under high-power cycling conditions. The increased porosity of the top layer reduces electrolyte permeation time, thereby reducing processing complexity and formation losses. Furthermore, the system allows for flexibility in material selection, accommodating natural graphite (NG), artificial graphite (AG), blends of both, or composites containing silicon oxide (SiO) or silicon-carbon (SiC).

[0015] Heterogeneous adhesive coating systems also offer customizable layer thicknesses and adhesive ratios to meet specific performance requirements. The underlayer typically has a concentration of 0.5 to 3 mg / cm³. 2 The loading weight, while the top layer ranges from 5 to 10 mg / cm³. 2 Preliminary experiments show that, compared to homogeneous coatings, this system reduces anode resistance by up to 15%, increases high-rate discharge capacity, and shortens electrolyte permeation time by approximately 30%. Furthermore, the anode maintains mechanical integrity over 500 cycles with minimal delamination observed.

[0016] Figure 1This is a conventional electrode design with a homogeneous coating applied to a metal foil current collector (typically copper). The electrode structure is an anode layer consisting of a homogeneous mixture of active material particles, a conductive agent, and a binder system. The binder typically comprises a combination of CMC and SBR to provide both mechanical stability and adhesion to the current collector.

[0017] Homogeneous coatings are characterized by a uniform distribution of their material throughout the anode layer. While this configuration offers a balance between manufacturing simplicity and mechanical strength and ionic / electronic conductivity, it can have limitations. A uniform binder composition can constrain porosity, leading to reduced electrolyte permeation and slower ion transport. Furthermore, the uniform distribution of CMC and SBR binders often results in a trade-off between mechanical integrity and electronic conductivity, as the insulating properties of the SBR can increase resistance within the anode.

[0018] Metal foil current collectors (such as copper) are shown as the substrate for the electrode assembly. It serves as a conductive substrate for electron transport while mechanically supporting the anode layer. A homogeneous coating adheres directly to the current collector. While suitable for standard lithium-ion battery operation, this homogeneous design may struggle to meet the high-power performance requirements of batteries that demand rapid electrolyte wetting, increased ion transport, and robust mechanical properties.

[0019] Figure 2 An electrode 10 with a layered structure is shown, comprising a current collector 12, a dual binder layer 14, and a single binder layer 16. This electrode 10 is a heterogeneous binder system that overcomes the limitations of conventional homogeneous coatings, thereby providing enhanced performance characteristics for lithium-ion batteries. The dual binder layer 14 and the single binder layer 16 are tailored to increase adhesion, mechanical integrity, electrolyte permeation, and ionic / electrical conductivity.

[0020] Current collector 12 serves as the base substrate of electrode 10. Current collector 12 is typically made of conductive metal foil (such as copper) and provides the mechanical support and electronic conductivity necessary for the operation of electrode 10. Current collector 12 maintains electron transport to and from the double adhesive layer 14 and the single adhesive layer 16 during cycling. In some embodiments, current collector 12 may be pretreated to increase the adhesion between current collector 12 and the double adhesive layer 14, thereby further increasing the mechanical stability of electrode 10.

[0021] A dual binder layer 14 is positioned directly on top of the current collector 12 and contains a mixture of two binders 18 in the binder matrix. These binders typically include CMC and SBR, which work together to provide mechanical strength, elasticity, and robust adhesion to the current collector. The dual binder layer 14 also encapsulates an electrode active material 22 (such as graphite or silicon-based composites) and a conductive agent 24 (such as carbon black or acetylene black) within its matrix structure. The electrode active material serves as a primary site for lithium-ion insertion, increasing the overall electronic conductivity of the dual binder layer 14. The composition and structure of the dual binder layer 14, sandwiched between and laminated with the single binder layer 16, maintains strong adhesion to the current collector 12 and provides a mechanically stable substrate for the electrode 10, thereby preventing delamination during cycling.

[0022] A single binder layer 16 is formed on top of a double binder layer 14 and contains a single binder 20, typically CMC. The single binder layer 16 is configured to increase porosity, thereby enabling increased electrolyte permeation and faster ion transport. Like the double binder layer 14, the single binder layer 16 also contains an electrode active material 22 and a conductive agent 24 to maintain ionic and electronic conductivity. The absence of an insulating binder (such as SBR) in the single binder layer 16 reduces resistance and allows for increased electron flow. In some embodiments, the slurry used to form the single binder layer 16 may further include a surfactant to control pore size distribution and increase uniformity.

[0023] Figures 3 to 6 The performance advantages of the disclosed heteroelectrode with a dual binder coating (referred to as the "dual coating") are shown compared to a conventional reference coating (referred to as the "reference coating"). Figures 3 to 6 Evaluate capacity retention, charge / discharge rate, and dynamic charging resistance under various conditions.

[0024] Figure 3 This is a charge rate performance graph showing the capacity retention (%) of the electrode at charge rates (C-rate) ranging from C / 3 to 2C. Capacity retention is an indicator of the electrode's ability to maintain its charge capacity at increasing current rates. The dual binder coating consistently outperforms the reference coating at all charge rates, thus maintaining a higher capacity retention as the rate increases. This improved performance is attributed to the increased ionic conductivity and electrolyte permeability provided by the porous single binder layer, which promotes efficient ion transport even at high charge rates.

[0025] Figure 4 This is a discharge rate performance graph showing the capacity retention (%) at discharge C rates varying from C / 3 to 2C. Similar to... Figure 3The charging rate results show that the dual-binder coating exhibits superior performance compared to the reference coating, thus maintaining a higher capacity percentage. The strong mechanical adhesion of the dual-binder layer ensures structural stability during high-rate discharge, while the increased porosity of the single-binder layer enhances ion transport and mitigates performance loss under high-current conditions.

[0026] Figure 5 This is a Hybrid Pulse Power Characterization (HPPC) resistance plot, showing the dynamic charge resistance (DCR) over a 10-second pulse at a 1C charge rate, plotted as a function of state of charge (SOC%). Compared to the reference coating, the dual-binder coating exhibits a lower DCR value across the entire SOC range. This reduction in resistance is directly related to the increased electronic and ionic pathways provided by the conductive agent and binder system in the dual-binder layers. The lower charge resistance translates to more efficient charging, particularly at intermediate SOC levels where battery performance is crucial.

[0027] Figure 6 The figure shows the discharge HPPC resistance curve of the dynamic DCR within a 10-second pulse at a 1C discharge rate, which also varies with SOC%. Compared to the reference coating, the dual-binder coating shows a significant reduction in DCR at all SOC levels. This improvement reflects the benefits of the heterogeneous binder structure, where the porous single binder layer promotes faster ion transport during discharge, and the mechanically robust dual-binder layer provides consistent performance under cycling conditions.

[0028] Figure 7 This is method 26 for fabricating a heterogeneous electrode assembly using a layered binder method to form an electrode with increased mechanical integrity, ionic and electronic conductivity, and efficient electrolyte permeation. In step 28, a slurry containing active material particles, a conductive agent, and a binder mixture of CMC and SBR is applied to a metal foil current collector. The metal foil (typically copper) serves as the conductive substrate of the electrode. The dual binder slurry forms the base layer of the electrode, thereby combining the adhesive and elastic properties of the SBR with the structural support of the CMC. The active material particles (such as graphite or silicon-based composites) enable lithium-ion intercalation, while the conductive agent (such as carbon black or acetylene black) promotes efficient electronic conductivity throughout the layer. In some embodiments, the slurry may include a surfactant to increase the dispersion of the binder and conductive agent to maintain a uniform layer structure. Additionally, the metal foil current collector may be pretreated to increase the adhesion between the current collector and the dual binder layer.

[0029] In step 30, the applied slurry is dried to form a non-porous layer that adheres firmly to the metal foil current collector. This dense layer provides a mechanically robust foundation for the electrode, thereby reducing the chance of delamination during battery cycling. Depending on the binder composition and processing requirements, the drying process is typically carried out at a temperature ranging from 80°C to 120°C. Calendering may be performed after drying to achieve the target density and mechanical strength of the non-porous layer, maintaining a stable substrate for subsequent layers.

[0030] In step 32, a second slurry comprising CMC is applied on top of the dried non-porous layer. This single-binder slurry forms a porous layer of the electrode, specifically designed to increase electrolyte permeation and ion transport. By eliminating SBR, this layer reduces resistance and increases porosity, thereby enabling faster and more uniform ion diffusion during operation. Surfactants can be added to the CMC slurry to control pore size distribution and increase uniformity throughout the porous layer.

[0031] In step 34, a single binder slurry is dried to form a porous layer, which adheres to a non-porous substrate layer, thereby completing the heterogeneous electrode assembly. The drying process of this layer is configured to maintain porosity for effective electrolyte wetting and excellent ionic conductivity. After drying, the electrode assembly can undergo an annealing process at a temperature between 150°C and 250°C to increase interlayer adhesion and further improve mechanical integrity. This stepwise method 26 produces a bilayer structure that incorporates the mechanical integrity of the substrate layer and the increased transport properties of the porous layer. Method 26 is applicable to a variety of active materials and conductive agents, making it suitable for high-power and fast-charging applications in lithium-ion batteries.

[0032] While specific embodiments of heterogeneous binder anode systems, such as the use of copper foil current collectors, double binder underlayers, and single binder top layers to improve performance, are described in detail, these examples are not intended to limit the invention to these particular configurations. This disclosure uses illustrative language to explain the principles and advantages of the invention, but should not be construed as limiting the scope of the invention. Variations and modifications to the compositions, structures, and processing methods may be made without departing from the core principles of the invention. Furthermore, the described features and elements can be combined or rearranged in various configurations to create additional embodiments. For example, the use of alternative anode materials (such as synthetic graphite or silicon-based composites) or adjustments to layer thickness, binder ratios, or manufacturing processes also fall within the scope of the invention. All such variations are contemplated and are considered to be within the scope of the claims.

[0033] According to the present invention, an electrode assembly is provided comprising: a metal foil current collector; a non-porous layer adhered to and in direct contact with the metal foil current collector, the non-porous layer comprising active material particles, a conductive agent, and a mixture of an adhesive system containing carboxymethyl cellulose and styrene-butadiene rubber; and a carboxymethyl cellulose porous layer bonded to the non-porous layer, the porous layer being configured to facilitate electrolyte permeation and ion transport.

[0034] According to an embodiment, the active material particles in the non-porous layer are selected from the group consisting of natural graphite, artificial graphite, silicon dioxide, and silicon-carbon composites.

[0035] According to an embodiment, the porous layer has a porosity of 40% to 70%.

[0036] According to an embodiment, the non-porous layer has a thickness of 10 micrometers to 30 micrometers.

[0037] According to an embodiment, the porous layer has a thickness of 5 micrometers to 15 micrometers.

[0038] According to an embodiment, the present invention is further characterized by the conductive agent in the porous layer.

[0039] According to an embodiment, the adhesive system in the non-porous layer has carboxymethyl cellulose and styrene-butadiene rubber in a weight ratio between 1:1 and 3:1.

[0040] According to an embodiment, the porous layer includes aligned pores to facilitate ion transport.

[0041] According to an embodiment, the metal foil current collector is copper.

[0042] According to the present invention, a method for forming an electrode includes: applying a mixed binder slurry containing active material particles, a conductive agent, and a mixture of carboxymethyl cellulose and styrene-butadiene binder to a metal foil current collector; drying the mixed binder slurry to form a non-porous layer adhered to the metal foil current collector; applying a carboxymethyl cellulose slurry on top of the non-porous layer; and drying the carboxymethyl cellulose slurry to form an electrode.

[0043] In one aspect of the invention, the method includes calendering the non-porous layer to achieve a target density before applying the carboxymethyl cellulose slurry.

[0044] In one aspect of the invention, the carboxymethyl cellulose slurry is applied by a doctor blade coating.

[0045] In one aspect of the invention, the mixed adhesive slurry is dried at a temperature between 80°C and 120°C.

[0046] In one aspect of the invention, the metal foil current collector is pretreated to increase the adhesion of the non-porous layer.

[0047] In one aspect of the invention, the method includes adding a surfactant to the carboxymethyl cellulose slurry.

[0048] In one aspect of the invention, the active material particles in the mixed binder slurry and the carboxymethyl cellulose slurry comprise a silicon-based composite.

[0049] In one aspect of the invention, the method includes annealing the electrode at a temperature between 150°C and 250°C after forming the porous layer.

[0050] According to the present invention, a negative electrode is provided, comprising: a current collector foil; a carboxymethyl cellulose and styrene-butadiene rubber binder matrix containing active materials; and a styrene-butadiene rubber layer sandwiched and laminated between the current collector foil and the carboxymethyl cellulose and styrene-butadiene rubber binder matrix.

[0051] According to an embodiment, the styrene-butadiene rubber layer has a thickness between 1 micrometer and 5 micrometers.

[0052] According to an embodiment, the active material is a blend of natural graphite and artificial graphite in a weight ratio of 2:1 to 3:1.

Claims

1. An electrode assembly comprising: Metal foil current collector; A non-porous layer is adhered to and in direct contact with the metal foil current collector, the non-porous layer comprising active material particles, a conductive agent, and a binder system containing carboxymethyl cellulose and styrene-butadiene rubber; as well as A carboxymethyl cellulose porous layer is incorporated into the non-porous layer, and the porous layer is configured to facilitate electrolyte permeation and ion transport.

2. The electrode assembly of claim 1, wherein the active material particles in the non-porous layer are selected from the group consisting of natural graphite, artificial graphite, silicon dioxide, and silicon-carbon composites.

3. The electrode assembly of claim 1, wherein the porous layer has a porosity of 40% to 70%.

4. The electrode assembly of claim 1, wherein the non-porous layer has a thickness of 10 micrometers to 30 micrometers.

5. The electrode assembly of claim 1, wherein the porous layer has a thickness of 5 micrometers to 15 micrometers.

6. The electrode assembly of claim 1, further comprising a conductive agent in the porous layer.

7. The electrode assembly of claim 1, wherein the binder system in the non-porous layer comprises carboxymethyl cellulose and styrene-butadiene rubber in a weight ratio between 1:1 and 3:

1.

8. The electrode assembly of claim 1, wherein the porous layer comprises aligned pores to facilitate ion transport.

9. The electrode assembly of claim 1, wherein the metal foil current collector is copper.

10. A method for forming an electrode, comprising: A mixture of binder slurry containing active material particles, conductive agent, and carboxymethyl cellulose and styrene-butadiene binder is applied to a metal foil current collector; The mixed adhesive slurry is dried to form a non-porous layer that adheres to the metal foil current collector; Carboxymethyl cellulose slurry is applied on top of the non-porous layer; as well as The carboxymethyl cellulose slurry is dried to form an electrode.

11. The method of claim 10, further comprising calendering the non-porous layer to achieve the target density prior to applying the carboxymethyl cellulose slurry.

12. The method of claim 10, wherein the carboxymethyl cellulose slurry is applied by a doctor blade.

13. The method of claim 10, wherein the drying of the mixed adhesive slurry is carried out at a temperature between 80°C and 120°C.

14. The method of claim 10, wherein the metal foil current collector is pretreated to increase the adhesion of the non-porous layer.

15. A negative electrode comprising: Current collector foil; Carboxymethyl cellulose and styrene-butadiene rubber binder matrix containing active materials; as well as A styrene-butadiene rubber layer, wherein the styrene-butadiene rubber layer is sandwiched between and laminated with the current collector foil and the carboxymethyl cellulose and styrene-butadiene rubber binder matrix.

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