Current collector, method for manufacturing the same, secondary battery, battery module, battery pack, and electric device

Abstract

The application provides a current collector and a preparation method thereof, and a secondary battery, a battery module, a battery pack and a power utilization device comprising the current collector. The current collector comprises a support layer, a binder layer and a metal layer, wherein the binder layer is arranged between the support layer and the metal layer, the binder layer comprises an organic binder and inorganic particles, the thickness D0 of the binder layer is 1.0-5.0 μm, optionally 1.0-3.0 μm, the inorganic particles comprise large particles with a median particle size D 50大 and small particles with a median particle size D 50小 , and the median particle sizes of the large particles and the small particles satisfy the following relationships: D 50大 >D 50小 ; D 50大 =(0.5-0.9)×D0; and D 50小 =(0.1-0.4)×D0.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a current collector, a method for preparing the current collector, and a secondary battery, battery module, battery pack, and power-consuming device including the current collector. Background Technology

[0002] In recent years, with the increasingly widespread application of lithium-ion batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. Due to the significant advancements in lithium-ion battery technology, higher requirements have been placed on its energy density, cycle performance, and safety performance.

[0003] Existing technologies have employed composite current collectors with a three-layer structure (metal layer-support layer-metal layer) to improve battery energy density and safety. In this structure, reducing the metal layer thickness significantly increases energy density; furthermore, thinning the metal layer enhances overall cell safety, and the thermal contraction of the intermediate support layer helps mitigate thermal runaway. However, during cold pressing, the electrodes of composite current collectors exhibit significantly greater elongation than ordinary current collectors, leading to electrode deformation, strip breakage, and wrinkling. Furthermore, in cells with this electrode structure, the electrodes near the weld lines are prone to wrinkling under cyclic expansion forces, degrading cell performance. Additionally, the greater elongation of the support layer compared to the metal layer makes delamination between the support and metal layers more likely, ultimately resulting in poor processing performance of the composite current collector. In addition, the interface between the metal layer and the support layer in the composite current collector is prone to burrs during cutting, and the metal layer may fall off after immersion in electrolyte, which can lead to safety issues and cell performance problems.

[0004] To address this, existing technologies have introduced an organic binder layer between the metal layer and the support layer to improve the adhesion of the composite current collector, thus solving problems such as burrs during slitting. However, in composite current collectors with an organic binder layer, the metal layer adheres directly to the organic binder, which has a very low elastic modulus. This results in a significant decrease in the elastic modulus of the current collector, leading to excessive cold-pressing elongation of the composite current collector electrode. Consequently, it fails to solve problems such as cold-pressing breakage and electrode wrinkling, and it is difficult to avoid delamination between the metal layer and the support layer.

[0005] Therefore, existing composite current collectors still need improvement in terms of simultaneously possessing sufficient adhesive strength and significantly improved elastic modulus. Summary of the Invention

[0006] In view of the above-mentioned problems in the background art, the purpose of this application is to provide a composite current collector that simultaneously possesses sufficient adhesive strength and significantly improved elastic modulus, thereby improving the processing performance of the composite current collector and enhancing the safety and long-term stability of the battery using the composite current collector.

[0007] To achieve the above objectives, in one aspect, this application provides a current collector comprising:

[0008] Support layer;

[0009] Adhesive layer; and

[0010] Metal layer, in which

[0011] The adhesive layer is disposed between the support layer and the metal layer.

[0012] The adhesive layer comprises organic adhesive and inorganic particles.

[0013] The thickness D0 of the adhesive layer is 1.0–5.0 μm, and can be selected as 1.0–3.0 μm.

[0014] The inorganic particles include those with a median particle size of D. 50大 Large particles and median particle size of D 50小 The median particle size of the large particles and the small particles satisfies the following relationship:

[0015] D 50大 >D 50小 ;

[0016] D 50大 = (0.5~0.9)×D0; and

[0017] D 50小 = (0.1~0.4)×D0.

[0018] Therefore, this application improves the interface between the metal layer and the support layer by setting an adhesive layer comprising organic binder and inorganic particles between the current collector and the metal layer, and by optimizing the thickness of the adhesive layer and the size of the inorganic particles. This enhances the adhesion and solves problems such as electrode wrinkling, curvature, and breakage during the cold pressing process of the current collector, thereby improving the dynamic performance of the battery using this current collector. Simultaneously, the elastic modulus of the current collector is increased, reducing its cold pressing elongation, further resolving issues such as electrode wrinkling, curvature, and breakage during the cold pressing process. Therefore, through the above-mentioned design of this application, the processing performance of the current collector is greatly improved, and the safety and long-term stability of the battery using this current collector are significantly enhanced.

[0019] In any embodiment, the inorganic particles account for 50 wt% to 85 wt%, and optionally 60 wt% to 80 wt%.

[0020] In any embodiment, based on the total mass of the inorganic particles, the mass percentage of the large particles is 70 wt% to 90 wt%, and the mass percentage of the small particles is 10 wt% to 30 wt%.

[0021] In any embodiment, the median particle size D of the large particles is... 50大 The particle size is 700–4500 nm; and / or, the median particle size D of the small particles is... 50小 The range is 100–2000 nm.

[0022] In any embodiment, the adhesive layer further includes carbon nanotubes, optionally comprising less than or equal to 10% of the total mass of the adhesive layer.

[0023] In any embodiment, the inorganic particles are selected from one or more of alumina, silicon carbide, silicon nitride, calcium oxide, silicon oxide, boehmite, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, barium sulfate, and boron carbide, and may be selected as alumina.

[0024] In any embodiment, the support layer comprises one or more selected from polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polysulfide, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, derivatives thereof, crosslinks thereof, and copolymers thereof.

[0025] In any embodiment, the organic binder is selected from one or more of polypropylene, carboxymethyl cellulose, polyacrylate, styrene-butadiene rubber, sodium polyacrylate, polyurethane, polyethyleneimine, polyvinylidene fluoride, chloroprene rubber, nitrile rubber, silicone rubber, polyvinyl acetate, urea-formaldehyde resin, phenolic resin, epoxy resin, silane coupling agent, titanate coupling agent, zirconium coupling agent, aluminate coupling agent, and borate coupling agent, and may be selected from one or more of polyurethane and polyacrylate, and more preferably polyurethane.

[0026] In any embodiment, the metal layer is an aluminum foil or a copper foil.

[0027] In a second aspect, this application provides a method for preparing a current collector, comprising:

[0028] Provide a support layer;

[0029] Inorganic particles and organic binders are uniformly dispersed in a solvent to prepare a slurry for forming a binder layer;

[0030] The slurry is applied to one surface of the support layer to form a coating for forming an adhesive layer;

[0031] The coating is pre-baked;

[0032] A metal layer is provided on the pre-baked coating to form a laminate for forming a current collector;

[0033] The laminate is subjected to high-temperature pressing, followed by curing.

[0034] A current collector with an adhesive layer disposed between the support layer and the metal layer is formed;

[0035] Optionally, the surface of the metal layer of the current collector can be physically or chemically etched to reduce the thickness of the metal layer.

[0036] The thickness D0 of the adhesive layer is 1.0–5.0 μm, and can be optionally 1.0–3.0 μm.

[0037] The inorganic particles include those with a median particle size of D. 50大 Large particles and median particle size of D 50小 The median particle size of the large particles and the small particles satisfies the following relationship:

[0038] D 50大 >D 50小 ;

[0039] D 50大 = (0.5~0.9)×D0; and

[0040] D 50小 = (0.1~0.4)×D0.

[0041] In a third aspect, this application provides a method for preparing a current collector, comprising:

[0042] Provide a metal layer;

[0043] Inorganic particles and organic binders are uniformly dispersed in a solvent to prepare a slurry for forming a binder layer;

[0044] The slurry is applied to one surface of the metal layer to form a coating for forming an adhesive layer;

[0045] The coating is pre-baked;

[0046] A support layer is provided on the pre-baked coating to form a laminate for forming a current collector;

[0047] The laminate is subjected to high-temperature pressing, followed by curing.

[0048] A current collector with an adhesive layer disposed between the support layer and the metal layer;

[0049] Optionally, the surface of the metal layer of the current collector can be physically or chemically etched to reduce the thickness of the metal layer.

[0050] The thickness D0 of the adhesive layer is 1.0–5.0 μm, and can be optionally 1.0–3.0 μm.

[0051] The inorganic particles include those with a median particle size of D. 50大 Large particles and median particle size of D 50小 The median particle size of the large particles and the small particles satisfies the following relationship:

[0052] D 50大 >D 50小 ;

[0053] D 50大 = (0.5~0.9)×D0; and

[0054] D 50小 = (0.1~0.4)×D0.

[0055] In any embodiment, carbon nanotubes are uniformly dispersed in a solvent along with inorganic particles and a binder.

[0056] In any embodiment, the pre-baking is carried out at a temperature of 50–90°C.

[0057] In any embodiment, the pressing is performed at a temperature 5 to 20°C lower than the melting point of the adhesive; alternatively, the pressing is performed under a pressure of 30T or more.

[0058] In a fourth aspect, this application provides a secondary battery comprising:

[0059] positive electrode;

[0060] negative electrode;

[0061] Electrolytes; and

[0062] Diaphragm, in which

[0063] At least one of the positive electrode and the negative electrode includes the current collector of the first aspect of this application.

[0064] In a fifth aspect, this application provides a battery module that includes the secondary battery of the fourth aspect of this application.

[0065] In a sixth aspect, this application provides a battery pack that includes the battery module of the fifth aspect of this application.

[0066] In a seventh aspect, this application provides an electrical device comprising at least one of the secondary battery of the fourth aspect of this application, the battery module of the fifth aspect of this application, and the battery pack of the sixth aspect of this application.

[0067] In the current collector of this application, by incorporating inorganic particles of both large and small sizes into the binder layer disposed between the support layer and the metal layer, the adhesive force of the current collector can be improved while simultaneously increasing its elastic modulus. This enhances the processing performance of the current collector and improves the safety and long-term stability of the battery using it. The current collector of this application achieves a discharge internal resistance (DCR) comparable to that of a metal current collector. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of a current collector according to one embodiment of this application.

[0069] Figure 2 These are photographs of the electrode sheets obtained after secondary battery cycling in Comparative Example 3(a) and Example 7(b).

[0070] Figure 3 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0071] Figure 4 yes Figure 3 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0072] Figure 5 This is a schematic diagram of a battery module according to one embodiment of this application.

[0073] Figure 6 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0074] Figure 7 yes Figure 6 An exploded view of a battery pack according to one embodiment of this application is shown.

[0075] Figure 8 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0076] Explanation of reference numerals in the attached figures:

[0077] 1 battery pack

[0078] 2 upper box

[0079] 3 lower cabinets

[0080] 4 battery modules

[0081] 5 Secondary batteries

[0082] 51 housing

[0083] 52 Electrode Assembly

[0084] 53 Top Cover Assembly

[0085] 6 sets of fluids

[0086] 61 metal layers

[0087] 62 Adhesive Layer

[0088] 63 Supporting layers

[0089] 7 Inorganic Particles Detailed Implementation

[0090] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the current collector and its preparation method, secondary battery, battery module, battery pack, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0091] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0092] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0093] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0094] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0095] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0096] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0097] In this application, the median particle size refers to the particle size corresponding to the cumulative volume distribution percentage of the inorganic particles reaching 50%. In this application, the median particle size D of the inorganic particles... 50 Particle size can be determined using laser diffraction particle size analysis. For example, according to standard GB / T 19077-2016, a laser particle size analyzer (e.g., Malvern Master Size 3000) can be used for determination.

[0098] This application provides a current collector, which includes:

[0099] Support layer;

[0100] Adhesive layer; and

[0101] Metal layer, in which

[0102] The adhesive layer is disposed between the support layer and the metal layer.

[0103] The adhesive layer comprises organic adhesive and inorganic particles.

[0104] The thickness D0 of the adhesive layer is 1.0–5.0 μm, and can be selected as 1.0–3.0 μm.

[0105] The inorganic particles include those with a median particle size of D. 50大 Large particles and median particle size of D 50小 The median particle size of the large particles and the small particles satisfies the following relationship:

[0106] D 50大 >D 50小 ;

[0107] D 50大 = (0.5~0.9)×D0; and

[0108] D 50小 = (0.1~0.4)×D0.

[0109] Although the mechanism is not yet clear, the applicant unexpectedly discovered that by setting an adhesive layer comprising organic binders and inorganic particles between the support layer and the metal layer, this application significantly improves the adhesion between the metal layer and the support layer. This prevents the metal layer from detaching after rolling, electrolyte immersion, and long-term cycling, thus improving the long-term stability of the battery including this current collector. Furthermore, the adhesive layer of a specific thickness greatly improves the interface between the metal layer and the support layer, solving the problem of burrs appearing during substrate cutting, thereby enhancing the safety of the battery cell.

[0110] In this application, as Figure 1 As shown, inorganic particles with both large and small particles are mixed into the binder layer to improve the elastic modulus of the binder layer. Furthermore, by optimizing the thickness of the binder layer and the size combination of the inorganic particles, the elastic modulus of the entire composite current collector is improved. This solves the problems of electrode wrinkling, curvature, and strip breakage caused by excessive cold pressing elongation in existing composite current collectors, and greatly improves the processing performance of the current collector.

[0111] Specifically, in this application, by controlling the size of the inorganic particles included in the adhesive layer, the dispersibility of the inorganic particles can be ensured, thereby effectively improving the elastic modulus of both the adhesive layer and the current collector. If the size of the inorganic particles is too small, it will be difficult to fully realize the effect of improving the elastic modulus. If the size of the inorganic particles is too large, the dispersibility may deteriorate, and undesirable local bumps may appear in the current collector after cold pressing. In this application, the inorganic particles include those with a median particle size of D. 50大 Large particles and median particle size of D 50小 Small particles (D) 50大 >D 50小 If the inorganic particles consist only of small particles, slippage can easily occur between them; if the inorganic particles consist only of large particles, many voids in the binder layer will be difficult to fill, ultimately negatively impacting the improvement of the elastic modulus. In this application, by combining appropriately sized large and small particles, and ensuring that the thickness D0 of the binder layer and the median particle size of the large and small particles satisfy D... 50大 = (0.5~0.9)×D0 and D 50小 The relationship between D0 and (0.1~0.4)×D0 optimizes the combination of adhesive layer thickness and inorganic particle size, thereby fully leveraging the effect of inorganic particles in the adhesive layer in enhancing the elastic modulus.

[0112] Therefore, the current collector of this application has a significantly improved elastic modulus, and the cold pressing elongation is greatly reduced during the cold pressing process. This reduces the risk of peeling between the metal layer and the support layer after cold pressing, reduces the number of cold pressing breakages, and reduces the elongation difference (cold pressing electrode arc height) between the active material region and the tab region of the electrode sheet using this current collector. This solves the problems of electrode wrinkling and breakage, greatly improves the processing performance of the current collector in the manufacturing of secondary batteries, and greatly improves the dynamic performance of secondary batteries using this current collector.

[0113] In this application, the thickness D0 of the adhesive layer is 1.0–5.0 μm, optionally 1.0–3.0 μm. When an adhesive layer with a thickness within the above-specified range is used, the effect of the inorganic particles in the adhesive layer in enhancing the elastic modulus can be sufficiently guaranteed. When the thickness of the adhesive layer is too small, it is difficult to coat the adhesive layer uniformly, resulting in uneven bonding between the metal layer and the support layer. Gaps or air bubbles may exist in the interface layer, thereby reducing the adhesion of the current collector and adversely affecting the elastic modulus of the current collector. When the thickness of the adhesive layer is too large, inorganic particles may settle and the particle distribution may be uneven during the coating process, which will adversely affect both the adhesion and elastic modulus of the current collector. Furthermore, when an adhesive layer with a thickness within the above-specified range is used, it is also possible to effectively suppress the undesirable increase in discharge internal resistance. The discharge internal resistance (DCR) of the battery using the current collector of this application is comparable to that of the battery using a metal layer as the current collector, thereby effectively suppressing the temperature rise during battery use and improving the cycle life and safety of the battery.

[0114] In some embodiments, the inorganic particles constitute 50 wt% to 85 wt% of the total mass of the adhesive layer, optionally 60 wt% to 80 wt%. In this application, adding inorganic particles to the adhesive layer of the current collector can increase the elastic modulus of the adhesive layer, thereby increasing the overall elastic modulus of the current collector. When the mass percentage of inorganic particles in the adhesive layer is too low, the effect of increasing the elastic modulus may not be fully realized; when the mass percentage of inorganic particles in the adhesive layer is too high, it may reduce the adhesion of the current collector and adversely affect the interfacial properties between the metal layer and the support layer.

[0115] In some embodiments, based on the total mass of the inorganic particles, the mass percentage of large particles is 70 wt% to 90 wt%, and the mass percentage of small particles is 10 wt% to 30 wt%. In this application, by using a combination of large and small particles in the inorganic particles, the effect of the inorganic particles in improving the elastic modulus is fully utilized. When the mass percentage of large particles in the inorganic particles is too low and the mass percentage of small particles is too high, it may be difficult to suppress the slippage between particles in the adhesive layer; when the mass percentage of large particles in the inorganic particles is too high and the mass percentage of small particles is too low, it may be difficult to fully fill the voids in the adhesive layer, ultimately adversely affecting the effect of improving the elastic modulus.

[0116] In some embodiments, the median particle size D of the large particles 50大 The particle size can be 700–4500 nm. When the particle size is too large, the particle dispersibility may deteriorate; when the particle size is too small, it may be difficult to suppress the slippage between particles in the binder layer. Optionally, the median particle size D of the small particles... 50小 The particle size can range from 100 to 2000 nm. When the particle size is too large, it may be difficult to fully fill the voids in the adhesive layer; when the particle size is too small, slippage may easily occur between particles in the adhesive layer, ultimately resulting in an unsatisfactory improvement in elastic modulus.

[0117] In some embodiments, the adhesive layer may further include carbon nanotubes. Carbon nanotubes can fill the gaps between inorganic particles, thereby further improving the elastic modulus of the current collector. Optionally, the mass percentage of carbon nanotubes relative to the total mass of the adhesive layer may be less than or equal to 10%. When the mass percentage of carbon nanotubes in the adhesive layer exceeds 10%, the elastic modulus of the current collector is unlikely to continue to increase with increasing carbon nanotube content, and it may also have an adverse effect on the adhesion of the current collector.

[0118] In some embodiments, the inorganic particles may be selected from one or more of alumina, silicon carbide, silicon nitride, silicon oxide, boehmite, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, barium sulfate, and boron carbide. In this application, as long as the size of the inorganic particles is within a specified range, they can sufficiently enhance the elastic modulus; therefore, the material of the inorganic particles is not specifically limited. As a non-limiting example, the inorganic particles may be alumina.

[0119] In some embodiments, the support layer comprises one or more selected from polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polysulfide, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, derivatives thereof, crosslinks thereof, and copolymers thereof. In this application, by providing a support layer, the thickness of the metal layer can be reduced, which is beneficial to improving the overall battery safety. Furthermore, the thermal shrinkage of the support layer can mitigate or eliminate the adverse effects of thermal runaway in the event of thermal runaway. Therefore, the material of the support layer is not specifically limited as long as it can perform the above-mentioned functions.

[0120] In some embodiments, the organic binder is selected from one or more of polypropylene, carboxymethyl cellulose, polyacrylate, styrene-butadiene rubber, sodium polyacrylate, polyurethane, polyethyleneimine, polyvinylidene fluoride, chloroprene rubber, nitrile rubber, silicone rubber, polyvinyl acetate, urea-formaldehyde resin, phenolic resin, epoxy resin, silane coupling agent, titanate coupling agent, zirconium coupling agent, aluminate coupling agent, and borate coupling agent. In this application, the organic binder is not limited in terms of material as long as it can improve the adhesion between the metal layer and the support layer. For example, the organic binder may be one or more of polyurethane and polyacrylate, and more preferably polyurethane.

[0121] In some embodiments, the metal layer is aluminum foil or copper foil. It is worth noting that the current collector of this application can be used as a positive electrode current collector or a negative electrode current collector in a secondary battery. When the current collector of this application is used as a positive electrode current collector in a secondary battery, the metal layer can be aluminum foil. When the current collector of this application is used as a negative electrode current collector in a secondary battery, the metal layer can be copper foil.

[0122] This application also provides a method for preparing a current collector, comprising:

[0123] Provide a support layer;

[0124] Inorganic particles and organic binders are uniformly dispersed in a solvent to prepare a slurry for forming a binder layer;

[0125] The slurry is applied to one surface of the support layer to form a coating for forming an adhesive layer;

[0126] The coating is pre-baked;

[0127] A support layer is provided on the pre-baked coating to form a laminate for forming a current collector;

[0128] The laminate is subjected to high-temperature pressing, followed by curing.

[0129] A current collector with an adhesive layer disposed between the support layer and the metal layer is formed;

[0130] Optionally, the surface of the metal layer of the current collector can be physically or chemically etched to reduce the thickness of the metal layer.

[0131] The thickness D0 of the adhesive layer is 1.0–5.0 μm, and can be optionally 1.0–3.0 μm.

[0132] The inorganic particles include those with a median particle size of D. 50大 Large particles and median particle size of D 50小 The median particle size of the large particles and the small particles satisfies the following relationship:

[0133] D 50大 >D 50小 ;

[0134] D 50大 = (0.5~0.9)×D0; and

[0135] D 50小 = (0.1~0.4)×D0.

[0136] This application provides a method for preparing a current collector, comprising:

[0137] Provide a metal layer;

[0138] Inorganic particles and organic binders are uniformly dispersed in a solvent to prepare a slurry for forming a binder layer;

[0139] The slurry is applied to one surface of the metal layer to form a coating for forming an adhesive layer;

[0140] The coating is pre-baked;

[0141] A support layer is provided on the pre-baked coating to form a laminate for forming a current collector;

[0142] The laminate is subjected to high-temperature pressing, followed by curing.

[0143] A current collector with an adhesive layer disposed between the support layer and the metal layer is formed;

[0144] Optionally, the surface of the metal layer of the current collector can be physically or chemically etched to reduce the thickness of the metal layer.

[0145] The thickness D0 of the adhesive layer is 1.0–5.0 μm, and can be optionally 1.0–3.0 μm.

[0146] The inorganic particles include those with a median particle size of D. 50大 Large particles and median particle size of D 50小 The median particle size of the large particles and the small particles satisfies the following relationship:

[0147] D 50大 >D 50小 ;

[0148] D 50大 = (0.5~0.9)×D0; and

[0149] D 50小 = (0.1~0.4)×D0.

[0150] The preparation method of this application can effectively prepare the current collector of the first aspect of this application.

[0151] In some implementations, carbon nanotubes can be uniformly dispersed in a solvent along with inorganic particles and organic binders.

[0152] In some embodiments, the pre-baking can be carried out at a temperature of 50–90°C.

[0153] In some embodiments, the high-temperature pressing can be performed at a temperature 5–20°C lower than the melting point of the organic binder. High-temperature pressing at such a temperature allows the organic binder to have a certain degree of fluidity during the pressing process, thereby achieving a tight bond between the metal layer and the support layer. Optionally, the high-temperature pressing can be performed under a pressure of 30T or higher. High-temperature pressing under such pressure can prevent the formation of air bubbles in the interface layer, thus achieving a tight bond between the metal layer and the support layer. This tight bond not only improves the adhesion between the metal layer and the support layer but also effectively prevents corrosive substances such as hydrofluoric acid from penetrating into the interface layer, providing resistance to corrosion in electrolyte environments.

[0154] This application also provides a secondary battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein at least one of the positive electrode and the negative electrode comprises the current collector of this application as described above.

[0155] This application also provides a battery module that includes the secondary battery of this application as described above.

[0156] This application also provides a battery pack that includes the battery module of this application as described above.

[0157] This application also provides an electrical device, which includes at least one of the secondary battery, battery module, and battery pack described above.

[0158] In the current collector of this application, by providing an adhesive layer comprising organic binder and inorganic particles between the support layer and the metal layer of the current collector, and optimizing the thickness of the adhesive layer and the size combination of the inorganic particles, the adhesive force of the current collector can be improved while simultaneously increasing the elastic modulus of the current collector. This enhances the processing performance of the current collector and improves the kinetic performance, safety, and long-term stability of the secondary battery using this current collector. The discharge resistance (DCR) of the current collector in this application is comparable to that of the metal layer, thereby effectively suppressing temperature rise during battery use and improving battery cycle life and safety.

[0159] The secondary battery, battery module, battery pack, and device of this application will be described below with appropriate reference to the accompanying drawings.

[0160] In one embodiment of this application, a secondary battery is provided.

[0161] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0162] [Positive electrode plate]

[0163] The positive electrode sheet may include the current collector of this application serving as the positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes, but is not limited to, lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium nickel manganese aluminum oxide, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel-type lithium manganese oxide, spinel-type lithium nickel manganese oxide, lithium titanate, etc. One or more of these materials may be used as the positive electrode active material.

[0164] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0165] The positive electrode film may optionally include a conductive agent. However, there is no specific limitation on the type of conductive agent, and those skilled in the art can select it according to actual needs. As an example, the conductive agent used for the positive electrode film may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0166] The positive electrode sheet can be prepared according to methods known in the art. The positive current collector used in the positive electrode sheet can be prepared by the current collector preparation method of this application. As an example, the positive active material, conductive agent and binder can be dispersed in a solvent (e.g., N-methylpyrrolidone (NMP)) to form a uniform positive electrode slurry; the positive electrode slurry is coated on the current collector of this application as the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet is obtained.

[0167] [Negative electrode plate]

[0168] The negative electrode sheet may include the current collector of this application as the negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0169] In the secondary battery of this application, the negative electrode active material can be any negative electrode active material commonly used in the art for preparing the negative electrode of a secondary battery. Examples of negative electrode active materials include artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials can be selected from one or more of elemental silicon, silicon oxide compounds (e.g., silicon suboxide), silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys.

[0170] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0171] In the secondary battery of this application, the negative electrode film typically comprises a negative electrode active material and optional binders, optional conductive agents, and other optional additives, and is usually formed by coating and drying a negative electrode slurry. The negative electrode slurry coating is typically formed by dispersing the negative electrode active material, optional conductive agents, and binders in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water.

[0172] As an example, the conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0173] As an example, the adhesive may be selected from one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0174] Other optional additives include thickeners (such as sodium carboxymethyl cellulose (CMC-Na)).

[0175] The negative electrode sheet can be prepared according to methods known in the art. The negative current collector used in the negative electrode sheet can be prepared by the current collector preparation method of this application. As an example, the negative electrode active material, conductive agent, binder and any other components can be dispersed in a solvent (e.g., deionized water) to form a uniform negative electrode slurry; the negative electrode slurry is coated on the current collector of this application as the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet is obtained.

[0176] [Electrolytes]

[0177] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0178] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0179] As an example, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0180] As an example, the solvent may be selected from one or more of the following: fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0181] In some embodiments, the electrolyte may optionally include additives. For example, the electrolyte may include negative electrode film-forming additives, positive electrode film-forming additives, additives to improve battery overcharge performance, additives to improve battery high-temperature performance, additives to improve battery low-temperature performance, etc.

[0182] [Septum]

[0183] The separator separates the positive and negative electrodes, preventing short circuits inside the battery, while allowing active ions to move between the positive and negative electrodes. In the secondary battery of this application, there are no particular restrictions on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0184] In some embodiments, the diaphragm material may be selected from one or more of the following: glass fiber film, nonwoven fabric film, polyethylene (PE) film, polypropylene (PP) film, polyvinylidene fluoride film, and multilayer composite films comprising one or more of these. The diaphragm may be a single-layer diaphragm or a multilayer composite diaphragm, without particular limitation. When the diaphragm is a multilayer composite diaphragm, the materials of each layer may be the same or different, without particular limitation.

[0185] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0186] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte as described above.

[0187] In some implementations, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0188] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 3 This is an example of a square-structured secondary battery 5.

[0189] In some implementations, refer to Figure 4 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0190] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0191] Figure 5 This is battery module 4, used as an example. (See reference...) Figure 5 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0192] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0193] In some embodiments, the battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0194] Figure 6 and Figure 7 This is battery pack 1 as an example. (See reference...) Figure 6 and Figure 7 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0195] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0196] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0197] Figure 8 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0198] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0199] Example

[0200] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0201] Preparation of inorganic particles

[0202] In the embodiments of this application, alumina particles are used as inorganic particles. These particles have a specific median particle size D. 50 The following general methods can be used to prepare alumina particles.

[0203] Commercially available alumina particles are used as raw materials, and further ball milling and screening are performed. For particles larger than 1 μm, sieving is performed two or more times using a sieve to obtain particles of the target size. For example, to prepare particles with a median particle size D... 50 For particles with a diameter of 1.5 μm, particles larger than 1.7 μm can be removed using a 1.7 μm sieve, and then particles smaller than 1.3 μm can be removed using a 1.3 μm sieve to obtain the median particle size D. 50The particles were approximately 1.5 μm in size. Finally, the median particle size D was determined using a particle size analyzer (Malvern Master Size 3000). 50 .

[0204] For particles smaller than 1 μm, centrifugation can be used for further screening to obtain particles of the target size. For example, first, sieve the particles through a 1 μm sieve to remove particles larger than 1 μm. Next, sonicate the obtained particles in an aqueous solution to prepare a suspension, and then centrifuge it at ≤3000 rpm for 20 min. Remove the bottom precipitate and collect the supernatant, then centrifuge it at ≥5000 rpm for 20 min. Remove the supernatant again and collect the precipitate particles. Measure the median particle size D of the precipitate particles using a particle size analyzer. 50 If necessary, further centrifugation and screening should be performed until the median particle size D is obtained. 50 Small particles were selected to meet the target value. Finally, the median particle size D was determined using a particle size analyzer (MalvernMaster, Size 3000). 50 .

[0205] Preparation of current collectors

[0206] In the embodiments of this application, the current collector can be prepared using the following general method.

[0207] The median particle size D prepared by the method described above 50大 Large particles and median particle size of D 50小 Small particles are mixed in a certain proportion. Optionally, carbon nanotubes may also be added, comprising less than or equal to 15% of the total weight of the binder layer. The above-mentioned large particles, small particles, and optional carbon nanotubes are mixed with polyurethane as an organic binder and stirred evenly in a solvent to prepare a slurry for forming the binder layer.

[0208] The support layer and the aluminum or copper foil, which serves as the metal layer, are placed on two unwinding rollers of a laminating machine. A slurry as described above is applied to the support layer to form a coating for forming the adhesive layer. The coating is pre-baked at a temperature of 50–90°C. A metal layer is then applied to the pre-baked coating to form a laminate for forming the current collector. The laminating machine operates at a speed of 10–80 m / min. The laminate is fed to a laminating roller, where it is subjected to high-temperature pressing at a temperature of 130–190°C and a pressure of 30T or more. The laminate, pressed and wound in the laminating roller, is then fed to a curing chamber and cured at a temperature of 55–70°C to obtain a current collector with an adhesive layer between the support layer and the metal layer.

[0209] In the above general method, the pressing temperature can be adjusted according to the melting point of the binder material. Specifically, the pressing temperature, i.e., the temperature of the composite roller, can be controlled at a temperature 5 to 20°C lower than the melting point of the binder, preferably 1 to 5°C lower.

[0210] If necessary, the above steps can be repeated on the other side of the support layer to complete the bonding between the other side and the metal layer.

[0211] If necessary, the surface of the metal layer can be thinned using physical or chemical etching. Specifically, physical etching involves treating the current collector with a plasma emitter, utilizing the etching effect of the plasma to thin the metal layer. In physical etching, the thickness of the metal layer reduction can be adjusted by the plasma etching time and power. Chemical etching involves treating the current collector using chemical reaction methods, more specifically, by reacting a chemical solution, such as an acid or alkali solution, on the surface of the current collector to thin the metal layer. In chemical etching, the thickness of the metal layer reduction can be controlled by the chemical reaction time and the concentration of the chemical solution.

[0212] Battery manufacturing

[0213] In embodiments of this application, at least one of the positive and negative electrodes of the secondary battery includes the current collector of this application. The secondary battery can be prepared using the following general methods.

[0214] (1) Preparation of positive electrode sheet

[0215] Active material LiNi 0.8 Co 0.1 Mn 0.1 O2 and LiNi 0.5 Co 0.2 Mn 0.3 O2 was mixed in a 17:3 ratio, and conductive agent Denka Black (from Denka Corporation, Japan) and binder polyvinylidene fluoride (HSV 900 from Arkema Group) were mixed in a 95:3:2 weight ratio in an N-methylpyrrolidone solvent system. The mixture was thoroughly stirred to obtain a slurry with a solid content of 70%. Using conventional processes, the positive electrode slurry was uniformly coated onto an aluminum foil or a positive electrode current collector with an aluminum foil as a metal layer, prepared by the above method, using an extrusion coater or transfer coater. The coated material was then dried at 85–110°C, followed by cold pressing, edge trimming, cutting, and slitting to obtain the positive electrode sheet.

[0216] (2) Preparation of negative electrode sheet

[0217] Artificial graphite (negative electrode active material), Super P (conductive agent), sodium carboxymethyl cellulose (CMC) (thickener), and styrene-butadiene rubber latex (SBR) (binder) were mixed in a mass ratio of 97:0.7:1.8:0.5 and added to deionized water as a solvent. The mixture was stirred evenly under vacuum to obtain a negative electrode slurry with a solid content of 56% by weight. The negative electrode slurry was then uniformly coated onto copper foil or a positive electrode current collector with a copper foil as a metal layer prepared by the above method using a conventional process. The coating was dried at 85–110°C, and then cold-pressed, trimmed, cut, and slit to obtain the negative electrode sheet.

[0218] (3) Preparation of electrolyte

[0219] In an argon-atmospheric glove box with a water content of <10 ppm, thoroughly dried lithium salt (LiPF6) was dissolved in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:20:60. Then, vinylene carbonate (VC) was added as an additive, and the mixture was thoroughly mixed to obtain the electrolyte. The concentration of lithium salt was 1 mol / L.

[0220] (4) Preparation of the diaphragm

[0221] Using a 9 μm thick polyethylene (PE) membrane as the base membrane, alumina, sodium carboxymethyl cellulose (CMC), and acrylate in a weight ratio of 93%:3%:4% were added to deionized water and stirred evenly under vacuum to obtain a slurry with a solid content of 55%. The obtained slurry was uniformly coated on both sides of the base membrane with a thickness of 2 μm on each side, and then PVDF was coated on one side to obtain the separator.

[0222] (5) Assembly of lithium-ion batteries

[0223] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for isolation. The resulting laminate is then wound into a square bare cell, tabs are welded on, and the bare cell is installed in a square aluminum casing. The top cover is laser-welded. After vacuum baking at 80°C to remove water, electrolyte is injected and the casing is sealed. Following this, the battery undergoes a series of processes including standing at 45°C, formation (0.02C constant current charging to 3.3V, then 0.1C constant current charging to 3.6V), shaping, and capacity testing to obtain the finished hard-shell lithium-ion battery, with a thickness of 28mm, a width of 97.5mm, and a length of 148mm.

[0224] Performance testing

[0225] (1) Elastic modulus

[0226] The current collector was punched into strips of 15mm × 150mm using a strip sampler. The punched strip samples were then tested using a tensile testing machine. The initial spacing of the tensile testing machine was 50mm, and the sample was stretched at a speed of 50mm / min until it broke. A section of the linear tensile zone before the yield point was taken, and the corresponding stress and strain were recorded. The elastic modulus was calculated using the following formula:

[0227] Elastic modulus = stress / strain.

[0228] (2) Adhesion

[0229] Apply double-sided tape to a smooth steel plate. Cut the current collector to the same width as the double-sided tape and apply it flat to the tape surface. Then, cut surface adhesive tape to the same width as the current collector and attach it to the surface, attaching an A4 paper strip longer than the steel plate to the end. Roll the surface adhesive tape back and forth with a 2.5kg roller until it is flat. Fix one end of the steel plate to a tensile testing machine (INSTRON, 3365), and fix the A4 paper strip with the surface adhesive tape to the other end of the machine. Peel the tape at a speed of 500mm / min to obtain the peel force curve, and calculate the average peel force, which is recorded as the adhesive force of the current collector.

[0230] (3) Cold pressing elongation

[0231] Take a coated electrode sheet with a length greater than 1 m and remove the tab portion. Mark the initial length L0 on the coated electrode sheet, and then cold-press it under a pressure of 30–60 T. The length of the electrode sheet after cold pressing is L1. Calculate the cold-press elongation using the following formula:

[0232] Cold pressing elongation = (L1-L0) / L0×100%.

[0233] (4) Arc height of cold-pressed electrode

[0234] Prepare a 1m long arc plate and a cold-pressed electrode sheet longer than 1m. Align the tabs of the cold-pressed electrode sheet with the two edges of the arc plate, let both sides hang down, and hang 50g weights on both sides with clamps. Then measure the height of the middle position relative to the protrusion of the arc plate (i.e., the height of the protrusion of the top of the arc relative to the two sides), and record it as the arc height of the cold-pressed electrode sheet.

[0235] (5) Number of wrinkles at the base of the ear after circulation

[0236] A fresh battery is charged and discharged at 0.33C at room temperature (25℃), and the initial capacity is recorded as C. It is then cycled at 1C charging and discharging rates at 60℃ until the capacity decays to 80% of the initial capacity. The electrodes are then removed from the cell. The removed electrodes are laid flat on a table, and the number of creases longer than 3mm at the base of each electrode is recorded. The number of creases longer than 3mm is recorded for more than 10 electrodes, and the average value is taken as the number of creases at the base of the electrodes after cycling.

[0237] (6) Number of cycles

[0238] A fresh battery is charged and discharged at a rate of 0.33C at room temperature (25°C). The discharge capacity at this time is recorded as the initial capacity C. The battery is then charged and discharged at a rate of 1C at 60°C until the capacity decays to 80% of the initial capacity. The number of cycles at this point is recorded.

[0239] (7) Discharge internal resistance (DCR)

[0240] Adjust the battery to 50% SOC and discharge it at a 4C rate (corresponding to a discharge current of I) for 30 seconds. Record the voltage difference ΔV before and after the 30-second discharge. Calculate the DCR corresponding to 50% SOC using the following formula:

[0241] DCR = ΔV / I.

[0242] (9) 2C discharge capacity retention

[0243] A fresh battery is fully charged at 0.33C at room temperature (25°C) and then discharged; the initial discharge capacity is recorded as C0. Then, the battery is discharged at 2C at room temperature (25°C); the discharge capacity at this point is recorded as C1. The capacity retention rate is calculated using the following formula:

[0244] Capacity retention rate = C1 / C0 × 100%.

[0245] (10) Number of burrs on the cutting end face

[0246] Take a current collector roll of approximately 3000m in length and cut it at a speed of 15m / min. Then, take approximately 12cm long tape and stick it to all positions on the end face. Then fix the tape on a glass slide and observe the surface of the tape under a microscope, counting the number of burrs larger than 200μm.

[0247] Example 1

[0248] The median particle size D prepared by the method described above 50大 Large particles (80% by mass) with a median particle size D of 1500 nm 50小20% by mass of 500 nm small particles were mixed to obtain inorganic particles for preparing the adhesive layer. The above inorganic particles (70% by mass) were mixed with polyurethane (30% by mass) as an organic binder and stirred evenly in N-methylpyrrolidone (NMP) as a solvent to prepare a slurry for forming the adhesive layer.

[0249] The slurry obtained as described above is coated on one surface of polyethylene terephthalate (PET) (4.5 μm thick) serving as a support layer to form a coating for forming an adhesive layer. The coating is pre-baked at approximately 60°C. An aluminum foil (5 μm thick) is provided as a metal layer on the pre-baked coating to form a laminate for forming a current collector. The laminator speed is approximately 20 m / min. The laminate is fed to a laminating roller, where it is subjected to high-temperature pressing at approximately 150°C and approximately 50T of pressure. The laminate, pressed and wound in the laminating roller, is fed to a curing chamber and cured at 60°C. The above process is repeated on the other surface of the support layer and the metal layer to obtain a current collector with an adhesive layer between the support layer and the metal layer. The obtained composite current collector is passed through an alkaline etching bath containing NaOH solution to thin the metal layer to approximately 2 μm, followed by water washing and hot air drying.

[0250] The current collector is used as the positive electrode current collector to further prepare the positive electrode sheet and secondary battery.

[0251] In this embodiment, the thickness D0 of the current collector adhesive layer is 2.0 μm. The inorganic particles in the adhesive layer include large and small particles, with the median particle size of the large particles being D. 50大 Satisfy the following relationship: D 50大 =0.75×D0; Median particle size D of small particles 50小 Satisfy the following relationship: D 50小 =0.25×D0. Based on the total mass of the binder layer, the inorganic particles account for 70 wt% of the mass. Based on the total mass of the inorganic particles, large particles account for 80 wt% of the mass, and small particles account for 20 wt% of the mass.

[0252] Examples 2-5 and Comparative Examples 1-2

[0253] The current collector, positive electrode, and secondary battery were prepared using essentially the same method as in Example 1, except that the thickness of the current collector binder layer is shown in Table 1.

[0254] The current collector elastic modulus, adhesion force, cold pressing elongation, cold pressing electrode arc height, number of wrinkles at the root of the electrode ear after cycling, number of cycles, DCR and 2C discharge capacity retention rate of Examples 1-5 and Comparative Examples 1-2 are also shown in Table 1.

[0255] Table 1

[0256]

[0257] In Comparative Example 1, the adhesive layer thickness D0 was 0.8 μm. In Comparative Example 2, the adhesive layer thickness D0 was 5.2 μm. Compared with Examples 1-5, where the adhesive layer thickness was in the range of 1.0 to 5.0 μm, the current collectors of Comparative Examples 1 and 2, although maintaining a high level of adhesion, exhibited a significantly reduced elastic modulus, resulting in excessively high cold-pressing elongation of the electrode sheet, with the arc height of the cold-pressed electrode sheet reaching over 8.0 mm / m. Furthermore, the battery cycle count decreased, and significant wrinkling of the electrode sheet occurred after cycling, with a large number of wrinkles >3 mm appearing at the root of the electrode tab. Additionally, the battery discharge internal resistance (DCR) increased, and the 2C discharge capacity retention rate decreased. This may be because when the adhesive layer thickness is too small, it is difficult to uniformly coat the adhesive layer onto the support layer; when the adhesive layer thickness is too large, inorganic particles are prone to sedimentation and uneven particle distribution during the coating process. Both of these situations adversely affect the elastic modulus of the current collector.

[0258] Examples 6-11 and Comparative Example 3

[0259] In Examples 6-11, the current collector, positive electrode, and secondary battery were prepared by essentially the same method as in Example 1, except that the mass percentage of inorganic particles based on the total weight of the binder layer is shown in Table 2.

[0260] In Comparative Example 3, no inorganic particles were added to the adhesive layer.

[0261] The current collector elastic modulus, adhesion force, cold pressing elongation, cold pressing electrode arc height, number of wrinkles at the root of the electrode tab after cycling, number of cycles, DCR and 2C discharge capacity retention rate of Examples 6-11 and Comparative Example 3 are also shown in Table 2.

[0262] Table 2

[0263]

[0264] In Comparative Example 3, because the binder layer did not include inorganic particles used to improve the elastic modulus, the elastic modulus of the current collector decreased sharply compared to Examples 6-11, which included inorganic particles. This resulted in a high cold-pressing elongation rate of 2.10% for the electrode and an arc height of 9.5 mm / m for the cold-pressed electrode. Furthermore, the number of battery cycles was significantly reduced, and the electrode showed obvious wrinkling after cycling, with a large number of wrinkles >3 mm appearing at the root of the tab.

[0265] As an example, Figure 2 Photographs of the electrodes obtained after disassembly from the secondary battery in Comparative Example 3(a) and Example 7(b) are shown. Figure 2 As shown in (a), in Comparative Example 3, the electrode exhibited obvious wrinkling. Figure 2 As shown in (b), in Example 7, no wrinkling occurred on the electrode after cycling. Figure 2 It is intuitive to see that by adding inorganic particles, including large and small particles, to the binder layer, the current collector of this application can eliminate the problem of electrode deformation and wrinkling in the prior art secondary batteries when applied to them.

[0266] In Examples 6-9, the mass percentage of inorganic particles is preferably in the range of 50 wt% to 85 wt%. Compared with Examples 10-11, the improvement in elastic modulus is further enhanced, resulting in a further decrease in the cold-pressing elongation rate of the electrode and a further reduction in the arc height of the cold-pressed electrode. In addition, the 2C discharge capacity retention rate of the battery is further improved.

[0267] Examples 12-15 and Comparative Examples 4-7

[0268] The current collector, positive electrode, and secondary battery were prepared using essentially the same method as in Example 1, the only difference being that the median particle size of the large particles was D. 50大 and the median particle size D of small particles 50小 The ratio between the adhesive layer thickness D0 and the adhesive layer thickness D0 is shown in Table 3.

[0269] The current collector elastic modulus, adhesion force, cold pressing elongation, cold pressing electrode arc height, number of wrinkles at the root of the electrode tab after cycling, number of cycles, DCR and 2C discharge capacity retention rate of Examples 12-15 and Comparative Examples 4-7 are also shown in Table 3.

[0270] Table 3

[0271]

[0272] In Comparative Example 4, the median particle size D of the large particles 50大 The ratio between the thickness D0 of the adhesive layer and the thickness D0 is 0.45. In Comparative Example 5, the median particle size of the large particles is D. 50大 The ratio between the thickness D0 of the adhesive layer and the thickness D0 is 0.95. This is related to the median particle size D of the large particles. 50大 The thickness D0 of the adhesive layer satisfies D 50大Compared to Examples 12-13 with a coefficient of (0.5-0.9)×D0, Comparative Examples 4 and 5, while maintaining a high level of adhesion, exhibited a significantly reduced elastic modulus, resulting in excessively high cold-pressing elongation of the electrode sheet and an arc height exceeding 7.5 mm / m. Furthermore, the battery cycle count decreased, and a large number of wrinkles >3 mm appeared at the base of the tabs after cycling. Additionally, the 2C discharge capacity retention rate of the battery decreased. This may be because when the particle size is too large, inorganic particles are not easily dispersed uniformly in the binder layer; conversely, when the particle size is too small, it is difficult to suppress the slippage between particles in the binder layer. Both of these situations adversely affect the elastic modulus of the current collector.

[0273] In Comparative Example 6, the median particle size D of the small particles 50小 The ratio between the thickness D0 of the adhesive layer and the thickness D0 is 0.05. In Comparative Example 7, the median particle size D of the small particles is... 50小 The ratio between the thickness D0 of the adhesive layer and the thickness D0 is 0.5. The ratio between the median particle size D of the small particles... 50小 The thickness D0 of the adhesive layer satisfies D 50小 Compared to Examples 14-15 with D0 = (0.1-0.4)×D0, Comparative Examples 6 and 7, while maintaining a high level of adhesion, exhibited a significantly reduced elastic modulus, resulting in excessively high cold-pressing elongation of the electrode sheet, with an arc height exceeding 7.5 mm / m. Furthermore, the battery cycle count decreased, and a large number of wrinkles >3 mm appeared at the base of the tabs after cycling. Additionally, the 2C discharge capacity retention rate of the battery decreased. This may be because when the small particles are too large, they cannot adequately fill the gaps between large particles; conversely, when the small particles are too small, slippage easily occurs between particles in the binder layer. Both of these situations adversely affect the elastic modulus of the current collector.

[0274] Examples 16-19

[0275] The current collector, positive electrode, and secondary battery were prepared using essentially the same method as in Example 1, except that the mass percentages of large and small particles, based on the total mass of the inorganic particles, are shown in Table 4.

[0276] The current collector elastic modulus, adhesion force, cold pressing elongation, cold pressing electrode arc height, number of wrinkles at the root of the electrode ear after cycling, number of cycles, DCR and 2C discharge capacity retention rate of Examples 16-19 are also shown in Table 4.

[0277] Table 4

[0278]

[0279] In Examples 16 and 17, the mass percentage of large particles is preferably in the range of 70 wt% to 90 wt%, and the mass percentage of small particles is preferably in the range of 10 wt% to 30 wt%. Compared with Examples 18 and 19, the improvement in elastic modulus is further enhanced, resulting in a further decrease in the cold-pressing elongation rate of the electrode sheet and a further reduction in the arc height of the cold-pressed electrode sheet. In addition, the number of battery cycles increases, and no wrinkles >3 mm appear at the root of the tab after cycling. Furthermore, the discharge internal resistance (DCR) of the battery decreases, and the 2C discharge capacity retention rate is further improved.

[0280] Examples 20-22 and Comparative Example 8

[0281] The current collector, positive electrode, and secondary battery were prepared using essentially the same method as in Example 1, except that carbon nanotubes were further added to the binder layer. The mass percentage of the carbon nanotubes is shown in Table 4.

[0282] The current collector elastic modulus, adhesion force, cold pressing elongation, cold pressing electrode arc height, number of wrinkles at the root of the electrode ear after cycling, number of cycles, DCR and 2C discharge capacity retention rate of Examples 20-22 and Comparative Example 8 are also shown in Table 5.

[0283] Table 5

[0284]

[0285] In Examples 20-22, the binder layer further includes carbon nanotubes comprising 10% or less by mass. Compared to Example 1 without added carbon nanotubes, the elastic modulus is further improved, resulting in a further decrease in the cold-pressing elongation of the electrode and a further reduction in the arc height of the cold-pressed electrode. Furthermore, the number of battery cycles increases. Additionally, the 2C discharge capacity retention rate of the battery is further improved. This may be because the carbon nanotubes can further fill the gaps between inorganic particles, thereby further increasing the elastic modulus of the current collector.

[0286] In Comparative Example 8, the mass percentage of carbon nanotubes was 15.0%. It can be seen that the elastic modulus of the current collector did not continue to increase with the increase of carbon nanotubes, but the adhesive force decreased.

[0287] Examples 23-27 and Comparative Example 9

[0288] The current collector was prepared using essentially the same method as in Example 1, except that a copper foil with a thickness of 1.5 μm was used as the metal layer, and the thickness D0 of the binder layer is shown in Table 6. In Preparation Examples 23–27, the current collector was used to prepare the negative electrode sheet and the secondary battery.

[0289] In comparison, no inorganic particles were added to the adhesive layer in Comparative Example 9.

[0290] The current collector elastic modulus, adhesion strength, cold pressing elongation, cold pressing electrode arc height, number of wrinkles at the root of the electrode tab after cycling, number of cycles, DCR and 2C discharge capacity retention rate of Examples 23-27 and Comparative Example 9 are also shown in Table 6.

[0291] Table 6

[0292]

[0293]

[0294] It can be seen that when the current collector of this application is used as the negative electrode current collector of a secondary battery, the excellent effects of this invention can also be achieved. Compared with Comparative Example 9, which does not include inorganic particles in the binder layer, the current collector of this application, prepared using copper foil as the metal layer, has a significantly improved elastic modulus, a significantly reduced cold-pressing elongation of the electrode sheet, and a significantly reduced arc height of the cold-pressed electrode sheet. In addition, the number of cycles of the battery using this current collector increases, and no 3mm wrinkles appear at the root of the tab after cycling. Furthermore, the discharge internal resistance (DCR) of the battery decreases, and the 2C discharge capacity retention rate is improved.

[0295] Preparation Examples 1-3 and Comparative Examples 1-4

[0296] The current collector, positive electrode, and secondary battery were prepared using essentially the same method as in Example 1, except that the high-temperature pressing temperature in the preparation of the current collector was as shown in Table 7.

[0297] The number of burrs and adhesion force on the cut end face of the current collectors prepared in Examples 1-3 and Comparative Examples 1-4 are shown in Table 7.

[0298] The current collector was immersed for 7 days in an electrolyte containing 1 mol / L LiPF6, ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) (volume ratio 20:20:60), and vinylene carbonate (VC) at an injection coefficient of approximately 126 g / Ah, and then the adhesion strength was measured again. The adhesion strength after 7 days of immersion in the electrolyte is also shown in Table 7.

[0299] The battery was cycled at 60°C under 1C charge and 1C discharge conditions until its capacity decayed to 80% of its initial capacity or its voltage suddenly dropped to 0V. The number of cells with internal short circuits per 10 cells was recorded. After storing the battery at 60°C for 60 days, the DCR was measured again, and the DCR growth rate compared to the initial value was calculated. The number of cells with internal short circuits and the DCR growth rate are shown in Table 7.

[0300] Table 7

[0301]

[0302]

[0303] In Preparation Examples 1-3, the current collectors were prepared by high-temperature pressing at a temperature 5-20°C lower than the melting point (°C) of the binder. The prepared current collectors exhibited excellent processing performance, with no burrs >200 μm generated during end-face cutting. Furthermore, the current collectors maintained a sufficiently high adhesion strength even after prolonged immersion in the electrolyte. Secondary batteries using these current collectors exhibited excellent long-term stability, with no internal short circuits after long-term cycling, and extremely low DCR growth rate after long-term storage at high temperatures. In contrast, in Comparative Examples 1-4, the high-temperature pressing temperature was not high enough, resulting in a large number of >200 μm burrs on the end-face during cutting, leading to poor processing performance. The adhesion strength of the current collectors was also poor, further decreasing after immersion in the electrolyte for 7 days, and even causing delamination. Secondary batteries using these current collectors exhibited poor long-term stability, with a significant proportion of internal short circuits after long-term cycling, and a significant increase in DCR after long-term storage at high temperatures. The reason may be that in the preparation of Comparative Examples 1 to 4, the pressing temperature was insufficient to give the binder a certain fluidity, resulting in insufficient adhesion between the metal layer and the support layer. Consequently, it was difficult to prevent corrosive substances such as hydrofluoric acid in the electrolyte from penetrating into the interface layer, which easily led to internal short circuits and significant deterioration in long-term stability.

[0304] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

[0305] Industrial application

[0306] The current collector of this application simultaneously possesses improved elastic modulus and enhanced adhesion, solving problems such as electrode wrinkling, curvature, and strip breakage during cold pressing of current collectors. This significantly improves the processing performance of the current collector and greatly enhances the safety and long-term stability of the battery when applied to secondary batteries. Therefore, this application is suitable for industrial applications.

Claims

1. A current collector, comprising: Support layer; Adhesive layer; and Metal layer, in which The adhesive layer is disposed between the support layer and the metal layer. The adhesive layer comprises organic adhesive and inorganic particles. The thickness D0 of the adhesive layer is 1.0~5.0 μm. The inorganic particles include those with a median particle size of D. 50大 Large particles and median particle size of D 50小 The median particle size of the large particles and the small particles satisfies the following relationship: D 50大 >D 50小 ; D 50大 = (0.5~0.9) × D0; and D 50小 = (0.1~0.4) × D0.

2. The current collector according to claim 1, wherein the thickness D0 of the adhesive layer is 1.0~3.0 μm.

3. The current collector according to claim 1, wherein the inorganic particles account for 50 wt% to 85 wt% of the total mass of the binder layer.

4. The current collector according to claim 3, wherein the inorganic particles account for 60 wt% to 80 wt% of the total mass of the binder layer.

5. The current collector according to claim 1, wherein, based on the total mass of the inorganic particles, the mass percentage of the large particles is 70 wt% to 90 wt%; and the mass percentage of the small particles is 10 wt% to 30 wt%.

6. The current collector according to claim 1, wherein the median particle size D of the large particles is... 50大 The median particle size D of the small particles is 700~4500 nm; and / or, the median particle size D of the small particles is... 50小 The range is 100~2000 nm.

7. The current collector according to claim 1, wherein the binder layer further comprises carbon nanotubes.

8. The current collector according to claim 7, wherein the carbon nanotubes account for less than or equal to 10% of the total mass of the binder layer.

9. The current collector according to claim 1, wherein the inorganic particles are selected from one or more of alumina, silicon carbide, silicon nitride, silicon oxide, calcium oxide, boehmite, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, barium sulfate, and boron carbide.

10. The current collector according to claim 1, wherein the inorganic particles are selected from alumina.

11. The current collector according to claim 1, wherein the support layer comprises one or more selected from polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polysulfide, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, derivatives thereof, crosslinks thereof, and copolymers thereof.

12. The current collector according to claim 1, wherein the organic binder is selected from one or more of polypropylene, carboxymethyl cellulose, polyacrylate, styrene-butadiene rubber, sodium polyacrylate, polyurethane, polyethyleneimine, polyvinylidene fluoride, chloroprene rubber, nitrile rubber, silicone rubber, polyvinyl acetate, urea-formaldehyde resin, phenolic resin, epoxy resin, silane coupling agent, titanate coupling agent, zirconium coupling agent, aluminate coupling agent, and borate coupling agent.

13. The current collector according to claim 1, wherein the organic binder is selected from one or more of polyurethane and polyacrylate.

14. The current collector according to claim 1, wherein the organic binder is selected from polyurethane.

15. The current collector according to any one of claims 1 to 14, wherein the metal layer is aluminum foil or copper foil.

16. A method for preparing a current collector, comprising: Provide a support layer; Inorganic particles and organic binders are uniformly dispersed in a solvent to prepare a slurry for forming a binder layer; The slurry is applied to one surface of the support layer to form a coating for forming an adhesive layer; The coating is pre-baked; A metal layer is provided on the pre-baked coating to form a laminate for forming a current collector; The laminate is subjected to high-temperature pressing, followed by curing. A current collector with an adhesive layer disposed between the support layer and the metal layer is formed; The thickness D0 of the adhesive layer is 1.0~5.0 μm, and The inorganic particles include those with a median particle size of D. 50大 Large particles and median particle size of D 50小 The median particle size of the large particles and the small particles satisfies the following relationship: D 50大 >D 50小 ; D 50大 = (0.5~0.9) × D0; and D 50小 = (0.1~0.4) × D0.

17. The method of claim 16, wherein the surface of the metal layer of the current collector is physically or chemically etched to achieve metal layer thinning.

18. The method of claim 16, wherein the thickness D0 of the adhesive layer is 1.0 to 3.0 μm.

19. A method for preparing a current collector, comprising: Provide a metal layer; Inorganic particles and organic binders are uniformly dispersed in a solvent to prepare a slurry for forming a binder layer; The slurry is applied to one surface of the metal layer to form a coating for forming an adhesive layer; The coating is pre-baked; A support layer is provided on the pre-baked coating to form a laminate for forming a current collector; The laminate is subjected to high-temperature pressing, followed by curing. A current collector with an adhesive layer disposed between the support layer and the metal layer is formed; The thickness D0 of the adhesive layer is 1.0~5.0 μm, and The inorganic particles include those with a median particle size of D. 50大 Large particles and median particle size of D 50小 The median particle size of the large particles and the small particles satisfies the following relationship: D 50大 >D 50小 ; D 50大 = (0.5~0.9) × D0; and D 50小 = (0.1~0.4) × D0.

20. The method of claim 19, wherein the surface of the metal layer of the current collector is physically or chemically etched to achieve metal layer thinning.

21. The method of claim 19, wherein the thickness D0 of the adhesive layer is 1.0 to 3.0 μm.

22. The method of claim 19, wherein the carbon nanotubes are uniformly dispersed in a solvent together with inorganic particles and an organic binder.

23. The method according to claim 19, wherein the pre-baking is performed at a temperature of 50 to 90°C.

24. The method of claim 19, wherein the pressing is performed at a temperature 5 to 20°C lower than the melting point of the organic binder.

25. The method according to any one of claims 19 to 24, wherein the pressing is performed at a pressure of 30 T or higher.

26. A secondary battery, comprising: positive electrode; negative electrode; Electrolytes; and Diaphragm, in which At least one of the positive electrode and the negative electrode includes the current collector according to any one of claims 1 to 15.

27. A battery module comprising the secondary battery of claim 26.

28. A battery pack comprising the battery module of claim 27.

29. An electrical device comprising at least one of the secondary battery of claim 26, the battery module of claim 27, and the battery pack of claim 28.

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