Current collector and preparation method thereof, electrode and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a current collector and a preparation method thereof, an electrode and a lithium ion battery. The current collector comprises a substrate layer, a functional layer and a coating layer, wherein the functional layer is arranged between the substrate layer and the coating layer; the substrate layer is made of an insulating material; the functional layer is of a composite layer structure and comprises metal layers and metal oxide layers which are alternately arranged; and the coating layer is a solid electrolyte layer. The current collector provided by the invention adopts a functional layer structure in which the metal layers and the metal oxide layers are alternated, so that the thermal stability and the safety of the battery under extreme conditions can be improved, and particularly, the current collector has excellent performance in acupuncture, extrusion and short-circuit tests, so that thermal runaway is effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a current collector and its preparation method, an electrode, and a lithium-ion battery. Background Technology

[0002] With the widespread application of lithium-ion batteries in electric vehicles, portable electronic devices, and energy storage systems, their increased energy density has provided greater potential for improving battery range. However, high-energy-density batteries are prone to internal short circuits leading to thermal runaway when subjected to mechanical impacts, which seriously affects the safety of lithium-ion batteries. Especially when lithium-ion batteries experience mechanical damage such as nail penetration, internal short circuits can cause a large release of heat, potentially leading to fires or explosions. Therefore, improving the safety of lithium-ion batteries, particularly under extreme conditions such as nail penetration tests, has become a pressing technical challenge.

[0003] Traditional lithium-ion batteries mostly use metal current collectors such as aluminum or copper. Although metal materials have high conductivity, they cannot effectively isolate short circuit paths when subjected to mechanical deformation, which increases the risk of thermal runaway.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended as a general commentary, nor is it intended to identify key / important components or describe the scope of these embodiments, but rather as a prelude to the detailed description that follows.

[0006] This invention addresses the limitations of existing technologies by providing a more comprehensive solution. It offers a current collector, its preparation method, an electrode, and a lithium-ion battery, thus mitigating the significant risk of thermal runaway in existing metal current collectors, particularly under mechanical deformation. This solution is achieved through a complex combination of techniques, including improved short-circuit path isolation and optimized thermal diffusion and conduction performance.

[0007] In some embodiments, a current collector includes:

[0008] The base layer is made of insulating material; The functional layer is a composite layer structure, consisting of alternating metal layers and metal oxide layers; The coating layer is a solid electrolyte layer; The functional layer is disposed between the base layer and the covering layer.

[0009] In some embodiments, the functional layer is composed of multiple metal layers with the metal oxide layer sandwiched between adjacent metal layers.

[0010] In some embodiments, the thickness ratio of the metal layer to the metal oxide layer is set to 7-10:1.

[0011] In some embodiments, the thickness ratio of the base layer, the functional layer, and the covering layer is set to 2-6 : 0.5-3 : 0.5-2.

[0012] In some embodiments, an adhesive transition layer is provided between the base layer and the functional layer; and / or, the insulating material is selected from one or more composites of polyethylene terephthalate, polypropylene, and polyimide.

[0013] In some embodiments, the solid electrolyte layer is composed of an organic matrix and an inorganic fast ion conductor in a mass ratio of 4:1 to 1:4. The organic matrix is ​​selected from one or more of polyethylene oxide, polyacrylonitrile, and polyvinylidene fluoride; the inorganic fast ion conductor is selected from one or more of lithium aluminum germanium phosphate, lithium lanthanum zirconium oxide, and lithium lanthanum titanium oxide.

[0014] In some embodiments, both the functional layer and the covering layer are provided in two layers, respectively disposed on both sides of the base layer.

[0015] In some embodiments, a method for preparing a current collector as described above includes the following steps: S1: Evaporate the material of the metal layer to deposit it on the side of the substrate layer; S2: Oxidize the outer surface of the metal layer to obtain the metal oxide layer; S3: The material of the metal layer is evaporated and deposited on the outer surface of the metal oxide layer; step S2 is repeated to obtain the functional layer; S4: Spray the slurry of the solid electrolyte layer onto the outer surface of the functional layer.

[0016] In some embodiments, an electrode includes the current collector as described above, or the current collector obtained by the preparation method described above.

[0017] In some embodiments, a lithium-ion battery includes a current collector as described above, or a current collector obtained by the preparation method described above, or an electrode as described above; the lithium-ion battery includes a lithium iron phosphate, lithium manganese iron phosphate, or a ternary battery system, wherein the ternary battery system is made of LiNi. x Co y Mn z M bO2, 0.7≤x≤0.9, 0.1≤y≤0.3, 0.1≤z≤0.3, 0≤b≤0.25, x+y+z+b=1.

[0018] The current collector, its preparation method, electrode, and lithium-ion battery provided in this invention can achieve the following technical effects: The current collector is designed with an alternating functional layer structure of metal and metal oxide layers, which can improve the thermal stability and safety of the battery under extreme conditions. Specifically, it performs well in nail penetration, extrusion and short circuit tests, thus effectively avoiding thermal runaway.

[0019] The above general description and the description below are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0020] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations and drawings do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are shown as similar elements. The drawings are not to be scaled. And wherein: Figure 1 This is a schematic diagram of a current collector structure provided in an embodiment of the present invention; Figure 2 This is a flowchart of the preparation process of a current collector provided in an embodiment of the present invention.

[0021] Figure label: 10. Base layer; 20. Covering layer; 30. Functional layer; 31. Metal oxide layer; 32. Metal layer; 40. Adhesive transition layer. Detailed Implementation

[0022] To provide a more detailed understanding of the features and technical content of the embodiments of the present invention, the implementation of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of the present invention. In the following technical description, for ease of explanation, several details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be implemented without these details. In other cases, well-known structures and devices may be shown in a simplified manner to simplify the drawings.

[0023] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0024] In this embodiment of the invention, the terms "upper," "lower," "inner," "middle," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for better describing the embodiments of the invention and their implementations, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to require them to be constructed and operated in a specific orientation. Furthermore, some of the above terms may be used to indicate other meanings besides orientation or positional relationship; for example, the term "upper" may in some cases indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in the embodiments of the invention according to the specific circumstances.

[0025] Furthermore, the terms "set up," "connect," and "fix" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this invention according to the specific circumstances.

[0026] Unless otherwise stated, the term "multiple" means two or more.

[0027] In this embodiment of the invention, the character " / " indicates that the objects before and after it are in an "or" relationship. For example, A / B means: A or B.

[0028] The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0030] Combination Figure 1 As shown, an embodiment of the present invention provides a current collector, comprising: The base layer is made of insulating material; The functional layer is a composite layer structure, consisting of alternating metal layers and metal oxide layers; The coating layer is a solid electrolyte layer; The functional layer is disposed between the base layer and the covering layer.

[0031] In this embodiment of the invention, an insulating material is used as the base layer for the current collector, providing sufficient structural support. Functional layers are formed on the sides of the base layer, particularly functional layers composed of alternating metal and metal oxide layers. The metal layer provides conductivity, while the metal oxide layer causes stress concentration, generating cracks when subjected to mechanical deformation such as puncture or compression. This preemptively cuts off the electronic pathways of the metal layer, suppressing thermal runaway caused by internal short circuits at its source. This demonstrates excellent thermal isolation and thermal stability, effectively preventing heat accumulation and ensuring battery safety under extreme conditions. The coating layer uses a solid electrolyte layer, which improves the battery's thermal stability, reduces heat accumulation, and decreases the risk of thermal runaway.

[0032] The insulating material of the base layer, including common materials such as rubber and plastic, mainly serves a structural support function. Depending on the application requirements, the insulating material can be made flexible for easy rolling. The metal layer can use traditional current collector materials, including aluminum and copper. The corresponding metal oxide layer material can include one or more of aluminum oxide, copper oxide, zinc oxide, and titanium oxide. Solid electrolyte materials are substances that exhibit ion conductivity under solid conditions, such as common lithium calcium phosphate oxide (Li3PO4) and lithium silicate oxide (Li7La3Zr2O). 12 , LLZO, etc.

[0033] In practical structural designs, functional layers and covering layers can be provided on at least one side of the base layer, as needed. Typically, both sides of the base layer are provided. Figure 1 As shown.

[0034] Optionally, the functional layer is composed of multiple metal layers with the metal oxide layer sandwiched between adjacent metal layers.

[0035] The functional layer used in this embodiment of the invention adopts a structure of multiple metal layers and a metal oxide layer between adjacent metal layers. When the functional layer undergoes mechanical deformation, the metal oxide layer will promptly cut off the electronic pathway of the adjacent metal layer due to the thin structure of both the metal layer and the metal oxide layer, thus suppressing thermal runaway caused by short circuits and improving the safety of the current collector.

[0036] Optionally, the thickness ratio of the metal layer to the metal oxide layer is set to 7-10:1.

[0037] In this embodiment of the invention, the thickness ratio of the metal layer to the metal oxide layer is 7-10:1. Under this thickness ratio, the conductivity of the functional layer is not affected. At the same time, the metal oxide layer can also cut off the electronic path of the metal layer during mechanical deformation, thus suppressing thermal runaway.

[0038] Optionally, the thickness ratio of the base layer, the functional layer, and the covering layer is set to 2-6 : 0.5-3 : 0.5-2.

[0039] The thickness relationship of the three main structural layers of the current collector is set as follows: the thickness ratio of the base layer, functional layer and the coating layer is 2-6 : 0.5-3 : 0.5-2. Since the base layer mainly plays a structural support role, its thickness is relatively large. The functional layer plays an electron transport role, and the coating layer plays a protective role. The combined effect of both allows for the use of relatively thin structural layers, thus saving resources compared to the structure of traditional current collectors.

[0040] Optionally, an adhesive transition layer is provided between the base layer and the functional layer.

[0041] An adhesive transition layer is set between the base layer and the functional layer, especially between the metal layer and the base layer, which greatly improves the bonding ability between the metal layer and the functional layer and the base layer. This prevents the metal layer from peeling off from the base layer during bending or ring forming of the current collector in subsequent operations, thus improving the service life of the entire current collector. More importantly, the bonding between the metal layer and the base layer is stable, making it easier for the metal oxide layer to act on the metal layer when subjected to mechanical deformation, so that electronic short circuits can be quickly cut off.

[0042] The bonding transition layer can be made of polyurethane (PU) or epoxy resin (EP).

[0043] Optionally, the insulating material is selected from one or more composites of polyethylene terephthalate, polypropylene, and polyimide.

[0044] In this embodiment of the invention, the insulating material used in the base layer can be selected from one or more composites of polyethylene terephthalate, polypropylene, and polyimide; preferably, it is a polyethylene terephthalate / polypropylene bilayer composite structure. All of these materials are flexible and can be rolled up, which is convenient for making cylindrical battery cores and has the strength and flexibility required for current collectors.

[0045] Optionally, the solid electrolyte layer is composed of an organic matrix and an inorganic fast ion conductor in a mass ratio of 4:1 to 1:4. The organic matrix is ​​selected from one or more of polyethylene oxide, polyacrylonitrile, and polyvinylidene fluoride; the inorganic fast ion conductor is selected from one or more of lithium aluminum germanium phosphate, lithium lanthanum zirconium oxide, and lithium lanthanum titanium oxide.

[0046] In this embodiment of the invention, the solid electrolyte layer is composed of a mixture of an organic matrix and an inorganic fast ion conductor. The two materials are mixed evenly, which facilitates contact and fixation with the functional layer to form a stable structure.

[0047] The mass ratio between the organic matrix and the inorganic fast ion conductor is 4:1 to 1:4, and the organic matrix is ​​selected from one or more of polyethylene oxide, polyacrylonitrile, and polyvinylidene fluoride; the inorganic fast ion conductor is selected from one or more of lithium aluminum germanium phosphate, lithium lanthanum zirconium oxide, and lithium lanthanum titanium oxide. The corresponding components can be dispersed by ball milling with solvent to form a uniform slurry, which is then sprayed onto the surface of the functional layer. After the solvent evaporates and dries, a composite solid electrolyte layer can be obtained.

[0048] In some embodiments, a method for preparing a current collector as described above includes the following steps: S1: Evaporate the material of the metal layer to deposit it on the side of the substrate layer; S2: Oxidize the outer surface of the metal layer to obtain the metal oxide layer; S3: The material of the metal layer is evaporated and deposited on the outer surface of the metal oxide layer; step S2 is repeated to obtain the functional layer; S4: Spray the slurry of the solid electrolyte layer onto the outer surface of the functional layer.

[0049] In embodiments of the present invention, such as Figure 2 As shown, the method of setting a functional layer on the side of the substrate layer involves evaporating the material of the metal layer at high temperature and depositing it on the surface of the substrate layer. The thickness of the deposition can be limited as needed. Then, the outer surface of the deposited metal layer is oxidized to form a metal oxide layer. Then, the outer surface of the metal oxide layer is evaporated and deposited again to obtain another metal layer. This process is repeated to obtain the functional layer.

[0050] In this embodiment of the invention, a metal layer is deposited on the surface of the substrate layer by deposition, and a metal oxide layer is formed by oxidation on the outer side of the metal layer, so that the three layers are tightly bonded and the structure is stable.

[0051] In structures where both outermost functional layers are metal layers, no further oxidation treatment is required during fabrication when the outermost layers are metal layers.

[0052] Finally, a slurry of a solid electrolyte layer is sprayed onto the outside of the functional layer to obtain the current collector.

[0053] In some embodiments, an electrode includes the current collector as described above, or the current collector obtained by the preparation method described above.

[0054] In some embodiments, a lithium-ion battery includes a current collector as described above, or a current collector obtained by the preparation method described above, or an electrode as described above; the lithium-ion battery includes a lithium iron phosphate, lithium manganese iron phosphate, or a ternary battery system, wherein the ternary battery system is made of LiNi.x Co y Mn z M b O2, 0.7≤x≤0.9, 0.1≤y≤0.3, 0.1≤z≤0.3, 0≤b≤0.25, x+y+z+b=1.

[0055] The present invention will be described in detail below using specific manufacturing examples of lithium-ion batteries.

[0056] Example 1 1. Preparation method of current collector a) Preparation and surface treatment of the substrate layer A polyethylene terephthalate (PET) film with a thickness of about 1.5 μm is selected as the core substrate layer, and then the PET is combined with a 1.5 μm polypropylene (PP) film to form a double-layer substrate structure through a hot pressing process at 140℃.

[0057] b) Apply adhesive transition layer Using a slot coating device, epoxy resin (EP) solution is uniformly coated onto the pretreated PET surface, with the dry film thickness controlled at 0.5 μm. The sample is then placed in a vacuum oven at 100°C for 15 min to dry and cure, forming a dense and strong adhesive layer. The function of this adhesive layer is to enhance the interfacial bonding force between the metal layer and the substrate layer, prevent the subsequent metal deposition layer from peeling off during bending or ring formation, and improve the process stability and service life of the current collector.

[0058] c) Vacuum evaporation of Al / Al2O3 functional layer The functional layer is prepared using a roll-to-roll vacuum evaporation device: a substrate layer with a bonding transition layer is passed through the evaporation chamber at a speed of 5 m / min. First, an aluminum wire is heated to 1300℃ to evaporate it, depositing a pure Al layer of about 50 nm thick on the surface of the bonding transition layer. Then, oxygen is precisely injected (the flow rate is controlled within the process range) to rapidly oxidize the Al layer surface to form an amorphous Al2O3 layer of about 5 nm thick. The "Al deposition-oxidation" process is repeated 20 times to form an "Al / Al2O3 staggered multilayer structure" with a thickness of about 1.0 μm on both sides of the substrate. This Al / Al2O3 staggered multilayer structure preferentially generates microcracks during mechanical deformation (such as needle punching and extrusion) through the stress concentration effect of the heterogeneous interface, cutting off the electronic path in advance and suppressing thermal runaway caused by internal short circuits from the root. This is the core design for achieving high safety in current collectors.

[0059] d) Outer layer coated with organic-inorganic composite solid electrolyte layer A composite electrolyte layer is coated on the side of the metal layer facing the positive electrode active material: polyethylene oxide (PEO) and lithium lanthanum zirconium oxide (LLZO) are mixed at a mass ratio of 1:1, added to acetonitrile solvent and ball-milled for 2 hours to prepare a uniform slurry; the slurry is coated on the surface of the metal layer by spraying, and after drying, a 1.5 μm thick composite electrolyte layer is formed; subsequently, a hot pressing process (120℃, 0.3 MPa) is used to enhance its good interfacial contact with the intermediate function, and the total thickness of the composite current collector is 9.0 μm.

[0060] The current collector of this invention comprises: a base layer material such as polyethylene terephthalate (PET) / polypropylene (PP) / polyimide (PI) to provide sufficient flexibility and structural support; a multilayer aluminum coating, wherein each aluminum layer is interposed with an aluminum oxide (Al2O3) layer, which is formed by controlling oxygen injection during vacuum evaporation; and an organic (ethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polycarbonate (PEC), etc.)-inorganic (lithium aluminum germanium phosphate (LAGP, Li)) coating on the surface of the aluminum foil. 1.5 Al 0.5 Ge 1.5 (PO4)3), lithium lanthanum zirconium oxide (LLZO, Li7La3Zr2O) 12 ), Lithium lanthanum titanium oxide (LLTO, Li 0.33 La 0.557 TiO3) solid electrolyte layer. Solid electrolyte layer can improve the thermal stability of battery and reduce heat release when puncture or short circuit occurs, thereby improving the safety of lithium battery.

[0061] The novel composite current collector structure proposed in this invention, combined with an organic-inorganic solid electrolyte coating, significantly improves the safety of lithium batteries under extreme conditions. This design, through multi-layer aluminum coating and solid electrolyte encapsulation, effectively interrupts the current path and suppresses heat generation during a short circuit, thereby preventing thermal runaway.

[0062] The total thickness of the current collector can be set to 6-15 μm, wherein the thickness of the base layer is 2-6 μm, the thickness of the functional layer is 0.5-3 μm, and the thickness of the coating layer is 0.5-2 μm. The thickness of the bonding transition layer can be 0.5-1.5 μm.

[0063] The current collector has a weight density of less than or equal to 2.0 g / cm³, compared to traditional 8-12 μm aluminum foil (2.7 g / cm³). 3 Weight reduction ≥26%. The tensile strength of the current collector is ≥50 MPa (longitudinal direction, MD), and the elongation at break is ≥10% (transverse direction, TD), which is superior to that of traditional current collectors.

[0064] The current collector of this invention can be used with lithium iron phosphate, lithium manganese iron phosphate, or ternary lithium (LiNi) lithium. x Co y Mn z M b The battery system (O2, 0≤b≤0.25, x+y+z+b=1) specifically refers to the positive and / or negative electrode of the battery. The battery system also includes a separator and an electrolyte.

[0065] 2. Method for manufacturing positive electrode plates Take the positive electrode active material (Li1Ni) 0.8 Co 0.1 Mn 0.1 O2), conductive carbon black, carbon nanotubes, and polyvinylidene fluoride (PVDF) were thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 96:1:1:2 to obtain a positive electrode coating material. This positive electrode coating material was then coated onto the aforementioned current collector. After drying and cold pressing, a positive electrode sheet was obtained with a compaction density of 3.6 g / cm³. 3 .

[0066] 3. Method for manufacturing negative electrode plates The negative electrode sheet comprises a polypropylene-based copper foil current collector and a negative electrode coating material coated on both sides of the current collector. The negative electrode coating material comprises 20.0 wt% deposited silicon carbon, 76.0 wt% graphite, 0.5 wt% single-walled carbon nanotubes (SWCNTs), 0.9 wt% conductive carbon black (Super P), 1.0 wt% sodium carboxymethyl cellulose (CMC), 0.8 wt% polyacrylic acid (PAA), and 0.8 wt% styrene-butadiene rubber (SBR). These substances are added to deionized water and stirred to form the negative electrode coating material. The negative electrode coating material is then coated onto both sides of the current collector. After drying and cold pressing, the negative electrode sheet is formed with a compaction density of 1.55 g / cm³. 3 .

[0067] 4. Preparation of electrolyte An electrolyte was prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC) in a mass percentage ratio of 16.0: 22.0: 52.0: 5.0: 5.0.

[0068] 5. Preparation of the diaphragm A high porosity (approximately 40%) membrane was selected. The thickness of the PE base membrane in the membrane was 9 μm, the thickness of the ceramic coating on both sides of the base membrane was 1.0 μm, and the thickness of the PVDF coating was 1.0 μm.

[0069] 6. Assembly of lithium-ion batteries After the positive and negative electrode sheets are rolled and slit, they are wound together with the separator according to a set process to form a 21700 cylindrical battery core. Subsequently, the battery core is fixed to a pre-made connecting piece by welding and then installed into a metal battery casing. After completing key processes such as electrolyte injection, sealing, and formation, the lithium-ion battery described in Example 1 is obtained. This lithium-ion battery uses a cylindrical casing with an external dimension of 21.0 mm in diameter and 70.0 mm in length, conforming to the 21700 standard specification.

[0070] Example 2 The difference between this embodiment and Embodiment 1 is that the substrate material is 3μm PET (non-PET / PP double-layer structure), while all other aspects are the same as in Embodiment 1.

[0071] Example 3 The difference between this embodiment and Embodiment 1 is that the substrate material is 3μm PP (non-PET / PP double-layer structure), while all other aspects are the same as in Embodiment 1.

[0072] Example 4 The difference between this embodiment and Embodiment 1 is that the substrate material is 3μm PI (non-PET / PP double-layer structure), while all other aspects are the same as in Embodiment 1.

[0073] Example 5 The difference between this embodiment and Embodiment 1 is that the metal oxide layer in the functional layer is CuO (not Al2O3), while everything else is the same as in Embodiment 1.

[0074] Example 6 The difference between this embodiment and Embodiment 1 is that the metal oxide layer in the functional layer is ZnO (not Al2O3), while everything else is the same as in Embodiment 1.

[0075] Example 7 The difference between this embodiment and Embodiment 1 is that the metal oxide layer in the functional layer is TiO2 (not Al2O3), while everything else is the same as in Embodiment 1.

[0076] Example 8 The difference between this embodiment and Embodiment 1 is that the organic matrix in the coating layer is PAN (not PEO), while everything else is the same as in Embodiment 1.

[0077] Example 9 The difference between this embodiment and Embodiment 1 is that the organic matrix in the coating layer is PAN (not PVDF), while everything else is the same as in Embodiment 1.

[0078] Example 10 The difference between this embodiment and Embodiment 1 is that the solid electrolyte in the coating layer is LAGP (not LLZO), while everything else is the same as in Embodiment 1.

[0079] Example 11 The difference between this embodiment and Embodiment 1 is that the solid electrolyte in the coating layer is LLZO (not LLZO), while everything else is the same as in Embodiment 1.

[0080] Example 12 The difference between this embodiment and Embodiment 1 is that the mass ratio of organic matrix to inorganic fast ion conductor in the coating layer is 4:1, while all other aspects are the same as in Embodiment 1.

[0081] Example 13 The difference between this embodiment and Embodiment 1 is that the mass ratio of organic matrix to inorganic fast ion conductor in the coating layer is 2:1, while all other aspects are the same as in Embodiment 1.

[0082] Example 14 The difference between this embodiment and Embodiment 1 is that the mass ratio of organic matrix to inorganic fast ion conductor in the coating layer is 1:2, while all other aspects are the same as in Embodiment 1.

[0083] Example 15 The difference between this embodiment and Embodiment 1 is that the mass ratio of organic matrix to inorganic fast ion conductor in the coating layer is 1:4, while all other aspects are the same as in Embodiment 1.

[0084] Example 16 The difference between this embodiment and Embodiment 1 is that the substrate material is a 2μm PET / PP double-layer structure, the functional layer thickness is 1μm (2 sides), the coating layer thickness is 1μm (2 sides), and the total thickness of the composite current collector is 6.0μm. All other aspects are the same as in Embodiment 1.

[0085] Example 17 The difference between this embodiment and Embodiment 1 is that the substrate material is a 5μm PET / PP double-layer structure, the functional layer thickness is 1.5μm (2 sides), the coating layer thickness is 2.5μm (2 sides), and the total thickness of the composite current collector is 14.0μm. All other aspects are the same as in Embodiment 1.

[0086] Comparative Example 1 The difference between this comparative example and Example 1 is that no metal oxide is introduced into the functional layer; it is entirely made of Al foil. Everything else is the same as in Example 1.

[0087] Comparative Example 2 The difference between this comparative example and Example 1 is that the coating layer does not contain a solid electrolyte layer; otherwise, they are the same as in Example 1.

[0088] Comparative Example 3 The difference between this comparative example and Example 1 is that the substrate material is a 1μm PET / PP double-layer structure, the functional layer thickness is 0.5μm (2 sides), the coating layer thickness is 0.5μm (2 sides), and the total thickness of the composite current collector is 4.0μm. All other aspects are the same as in Example 1.

[0089] Method for determining the mass ratio of organic matrix to inorganic fast ion conductor in the coating layer: The coating layer sample was completely peeled off from the current collector, pulverized into fine powder, and dried in a vacuum drying oven at 60℃ for 2 hours to remove moisture and residual solvent. 10 mg of the dried sample was placed in the alumina crucible of the thermogravimetric analyzer (TGA) and heated from room temperature to 500℃ at a heating rate of 5-10℃ / min under a nitrogen atmosphere (flow rate 40 mL / min). The TGA curve was recorded. The mass loss in the low-temperature range (200–500℃) corresponds to the amount of organic matrix decomposition (m1). m1 / 10 is the mass percentage of the organic matrix. The experiment was repeated 3 times and the average value was taken to ensure the accuracy of the results.

[0090] Method for determining the weight density of composite current collectors: First, the current collector is cut into regular sheets (e.g., 1cm × 1cm). The length, width, and thickness are measured using a laser thickness gauge, and the volume (V, unit cm³) is calculated. Then, the sample mass (m, unit g) is accurately weighed using an electronic balance. Finally, the weight density (g / cm³) is calculated using the formula ρ = m / V. During the testing process, the sample should be kept flat and free from warping, and moisture interference should be eliminated under dry conditions.

[0091] Methods for determining the tensile strength and elongation at break of composite current collectors: The tensile properties of the current collector were tested on an electronic universal testing machine, following GB / T 1040 or ASTM D882 standards. At a tensile rate of 50 ± 0.5 mm / min, current collector samples with dimensions of 50 mm × 10 mm were clamped between the machine fixtures, and stress-strain curves were recorded to obtain the maximum tensile load and elongation at break. The tensile strength was calculated by dividing the maximum load by the cross-sectional area, i.e., tensile strength σ = Elongation at break is the percentage of elongation at fracture relative to the initial length, i.e., elongation at break ε = × 100%. Before testing, the sample thickness must be measured and it must be ensured to be flat and free of warping. At least 5 sets of samples should be measured for each group and the average value should be taken. The data obtained can be used to evaluate the flexibility and structural stability of the current collector.

[0092] 70% Deformation Extrusion Test: After charging the lithium-ion battery to 100% charge, it was placed horizontally on the extrusion test platform. A cylindrical steel rod with a diameter of 32mm was used as the extrusion head, and extrusion force was applied to the battery thickness direction at a rate of 10mm / min. At the same time, the battery thickness change was monitored in real time by a displacement sensor. Extrusion was stopped immediately when the battery deformation reached 70% of the original thickness. The highest temperature on the battery surface was continuously recorded during the extrusion process, and the battery did not catch fire or explode.

[0093] 10mΩ external short-circuit test: The external short-circuit test method for lithium-ion batteries is as follows: The cell is first charged at a constant current of 1C to the rated voltage (e.g., 4.2V), then charged at a constant voltage until the charging current is ≤0.1C. The initial internal resistance and voltage are recorded. Subsequently, a 10mΩ low-resistance wire is used to directly connect the positive and negative terminals of the battery to trigger a short circuit. The test is conducted at 25℃, with real-time monitoring of the short-circuit current, battery surface temperature, and voltage changes. The test standard is that the battery must not catch fire or explode during the short circuit, and the maximum surface temperature must be <150℃.

[0094] Needle prick test experiment: The battery to be tested was fully charged to 100% SOC and placed in a 25℃ environment for 2 hours to stabilize. Then, the battery was fixed on an insulating clamp, ensuring that its positive and negative terminals were horizontal. Using a 3mm diameter stainless steel needle, perpendicular to the battery surface and along the direction between the positive and negative terminals, the needle was inserted into the battery at a constant speed of 10±1mm / s until it was completely penetrated (the penetration depth should exceed 90% of the battery thickness). After insertion, the needle was kept still, and the battery status was continuously observed for 5 minutes. Any abnormal phenomena such as fire, explosion, or smoke were recorded, and temperature changes were monitored using a thermocouple attached to the battery surface.

[0095] The specific results are as follows: Table 1

[0096] As shown in Table 1, comparing Examples 1 to 4 reveals that the current collector material of different substrate layers has a certain impact on the safety performance of lithium batteries. Example 1 (PET / PP) exhibited a relatively low surface temperature (76.8℃) in the nail penetration test, demonstrating good thermal stability and heat dissipation ability. Its surface temperature in the short-circuit test was 124.5℃, indicating that the material can effectively avoid heat accumulation and prevent thermal runaway. Although Examples 2 (PET) and 3 (PP) had slightly higher surface temperatures in the nail penetration test, they still passed all tests, and their temperature rises in the short-circuit test were 126.3℃ and 127.6℃, respectively, demonstrating good thermal stability. Conversely, Example 4 (PI) had a surface temperature of 128.9℃ in the short-circuit test, indicating that this material is weak in thermal management, with a faster rate of heat accumulation, which may lead to a higher risk of thermal runaway.

[0097] From a mechanistic perspective, the differences in thermal response between substrate materials primarily stem from their thermal conductivity and thermal stability. The lower surface temperature of the PET / PP substrate combination reflects its strong thermal management capabilities and good thermal conductivity, enabling it to effectively dissipate heat and prevent heat buildup under extreme conditions. In contrast, the higher surface temperature of the PI substrate material indicates its poor thermal conductivity, making it difficult to dissipate heat effectively, leading to a rapid increase in surface temperature during short circuits. Furthermore, polypropylene (PP) and polyethylene terephthalate (PET) are superior to PI in terms of coefficient of thermal expansion and mechanical properties, making them more resilient and thermally stable under external impacts or short circuits.

[0098] Table 2

[0099] As shown in Table 2, comparing Examples 5 to 7 reveals the performance differences of different metal oxide types as functional layer materials under various extreme tests, reflecting the significant impact of these materials on the thermal management and safety of lithium-ion battery current collectors. Example 1 (Al2O3) exhibited a low surface temperature (76.8℃) in the nail penetration test, demonstrating good thermal insulation and stability, effectively preventing heat accumulation and ensuring battery safety under extreme conditions. In the short-circuit test, the surface temperature was 124.5℃, indicating that the material effectively reduces heat conduction and prevents thermal runaway. Examples 5 (CuO) and 6 (ZnO) exhibited higher surface temperatures of 135.5℃ and 136.4℃, respectively, indicating that these two materials have high thermal conductivity, leading to rapid heat accumulation during short circuits and increasing the risk of thermal runaway. Example 7 (TiO2) showed a short-circuit test surface temperature of 139.9℃, further reflecting the material's high thermal conductivity, which may lead to a larger area of ​​heat accumulation, thus increasing safety risks.

[0100] From a mechanistic perspective, the differences between metal oxide types mainly stem from their thermal conductivity and thermal insulation properties. As a material with low thermal conductivity, Al2O3 can effectively isolate heat and prevent it from propagating within the current collector, thereby maintaining a lower surface temperature and reducing the possibility of thermal runaway.

[0101] Table 3

[0102] As shown in Table 3, comparing Examples 1, 8, and 9, Example 1 (PEO) exhibited a lower surface temperature (76.8°C) in the nail penetration test, demonstrating good thermal stability and heat dissipation ability, effectively preventing heat accumulation and ensuring battery safety under extreme conditions. In the short-circuit test, the surface temperature was 124.5°C, indicating that the material effectively reduces heat conduction and prevents thermal runaway. Example 8 (PAN) showed a higher surface temperature (79.6°C), indicating that its thermal response was slightly higher than PEO, but still within a reasonable range; its short-circuit test surface temperature was 126.4°C, showing good thermal stability. Example 9 (PVDF) exhibited the highest surface temperature (85.6°C) in the nail penetration test, indicating that the material is more sensitive in terms of thermal response and accumulates heat quickly; although its surface temperature in the short-circuit test was 124.3°C, the lower temperature rise compared to the nail penetration test alleviated some safety concerns, but certain safety hazards may still exist.

[0103] From a mechanistic perspective, the differences in organic matrix types mainly stem from their thermal conductivity, thermal stability, and structural characteristics. As a material with low thermal conductivity, PEO can effectively isolate heat during nail penetration and short-circuit tests, preventing its propagation within the current collector and maintaining a low surface temperature, thereby reducing the risk of thermal runaway.

[0104] Table 4

[0105] As shown in Table 4, comparing Examples 1, 10, and 11, it is evident that different solid electrolyte types (LLZO, LAGP, LLTO) have a significant impact on the thermal management and safety of the lithium battery current collector when used as the outer solid electrolyte layer material. Example 1 (LLZO) exhibited a surface temperature of 76.8°C in the nail penetration test, demonstrating good thermal stability and heat dissipation capabilities, effectively preventing heat accumulation and ensuring battery safety under extreme conditions. In the short-circuit test, the surface temperature was 124.5°C, indicating that the material effectively reduces heat conduction and prevents thermal runaway. Example 10 (LAGP) had a surface temperature of 79.2°C in the nail penetration test, slightly higher than LLZO but still within a reasonable range. Its short-circuit test surface temperature was 134.5°C, indicating that the material has relatively strong thermal stability and thermal management capabilities. Example 11 (LLTO) exhibited a high surface temperature of 80.7°C in the needle penetration test, showing a high thermal response and a rapid heat accumulation rate; its short-circuit test surface temperature was 136.5°C, further reflecting the material's high thermal conductivity, which may lead to a large area of ​​heat accumulation, thereby increasing safety risks.

[0106] From a mechanistic perspective, the differences between solid electrolyte types mainly stem from their thermal conductivity, thermal stability, and electrical conductivity. LLZO, as a solid electrolyte with low thermal conductivity, exhibits a low surface temperature in nail penetration and short-circuit tests, effectively isolating heat and preventing heat buildup, thus reducing the risk of thermal runaway. LAGP has higher thermal conductivity, resulting in a slightly higher surface temperature in nail penetration and short-circuit tests, but it remains within a safe range, demonstrating good thermal stability. LLTO's higher thermal conductivity makes heat conduction easier, leading to faster heat buildup and a higher surface temperature in short-circuit tests, increasing the risk of thermal runaway.

[0107] Table 5

[0108] As shown in Table 5, comparing Examples 1, 12 to 15, Example 1 (mass ratio 1:1) exhibited a lower surface temperature (76.8℃) in the needle penetration test, demonstrating better thermal stability and heat dissipation ability. In the short-circuit test, the surface temperature was 124.5℃, effectively suppressing heat accumulation. Example 12 (mass ratio 4:1) had a needle penetration test temperature of 85.6℃ and a short-circuit test temperature of 127.6℃, while Example 15 (mass ratio 1:4) had a needle penetration test temperature of 89.6℃ and a short-circuit test temperature of 132.5℃. This indicates that the ratio of organic matrix to inorganic fast ion conductor in the solid electrolyte has a certain impact on thermal stability. Mechanistically, the mass ratio of the solid electrolyte affects the thermal conductivity and thermal insulation capability of the material. In contrast, the lower surface temperature at a mass ratio of 1:1 indicates the better thermal insulation properties of the organic solid electrolyte, which helps control heat accumulation.

[0109] The surface temperatures of the needle penetration test in Examples 13 (mass ratio 2:1), 14 (mass ratio 1:2), and 15 (mass ratio 1:4) gradually increased to 82.7°C, 87.6°C, and 89.6°C, respectively, while the short-circuit test temperatures also gradually increased to 131°C, 133°C, and 132.5°C, respectively. With the change in the ratio of organic to inorganic fast ion conductors, the thermal response of the battery under extreme conditions gradually increased. A higher ratio of inorganic fast ion conductors (e.g., 1:4) may lead to higher thermal conductivity and more rapid heat conduction, resulting in an increase in surface temperature.

[0110] Table 6

[0111] As shown in Table 6, comparing Examples 1, 16, and 17, Example 1 (current collector thickness 9 μm) exhibited a lower surface temperature (76.8 °C) in the needle penetration test, demonstrating good thermal stability and heat dissipation ability. In the short-circuit test, the surface temperature was 124.5 °C, effectively suppressing heat accumulation. Example 16 (current collector thickness 7 μm) showed a significantly higher surface temperature of 106.7 °C, indicating that the thinner current collector accumulated heat more quickly during needle penetration, potentially leading to a higher surface temperature. The temperature in the short-circuit test was 135.6 °C, further reflecting the impact of current collector thickness on thermal management. Example 17 (current collector thickness 14 μm) had a surface temperature of 77.6 °C in the needle penetration test, slightly higher than Example 1, but still within a lower range. Its short-circuit test temperature was 128.5 °C, showing good thermal stability. Mechanistically, the thickness of the current collector has a significant impact on thermal conductivity and thermal insulation capabilities. Thinner current collectors (such as in Example 16) have higher thermal conductivity, allowing heat to be easily conducted through them, leading to faster heat accumulation and an increase in surface temperature. Thicker current collectors (such as in Example 17) provide better thermal insulation, reducing heat conduction and maintaining a lower surface temperature. The current collector thickness in Example 1 is moderate, achieving a good balance in thermal management and ensuring the safety and stability of the battery under extreme conditions.

[0112] Table 7

[0113] As shown in Table 7, comparing Comparative Examples 1 to 3 with Example 1, it can be seen that Comparative Example 1 (functional layer without Al2O3) failed the needle penetration test, with a surface temperature reaching 360.0℃, far higher than Example 1, indicating that this design lacks effective thermal isolation, and heat accumulates rapidly inside the battery, increasing the risk of thermal runaway. Although it passed the short-circuit test, the temperature reached 138.7℃, indicating that the lack of an Al2O3 intermediate layer makes heat conduction uncontrolled, posing a serious safety hazard. Comparative Example 2 (outermost layer without organic matrix / solid electrolyte coating) failed multiple tests, with a surface temperature as high as 425.0℃ in the needle penetration test and 486.5℃ in the short-circuit test, exhibiting extremely poor thermal stability. The lack of an organic matrix / solid electrolyte coating results in ineffective heat isolation and management, greatly increasing the risk of thermal runaway, indicating that the coating of the outer solid electrolyte layer is crucial for battery safety. Comparative Example 3 (current collector thickness 4 μm) also failed multiple tests, with a surface temperature as high as 503.6℃ in the needle penetration test and 523.6℃ in the short-circuit test. This indicates that the excessively thin current collector design leads to rapid heat conduction, failing to effectively isolate the heat source and resulting in extremely high surface temperatures, severely impacting the battery's thermal management performance and safety. Mechanistically, the comprehensive design of Example 1, through optimizing the functional layer (Al2O3), the outer coating of the organic matrix / solid electrolyte, and an appropriate current collector thickness, effectively suppresses heat accumulation and conduction, ensuring the battery's thermal stability under extreme testing conditions. In contrast, Comparative Examples 1, 2, and 3 lack thermal isolation functions, have inadequate coating materials, or have excessively thin current collector designs, leading to rapid heat accumulation, a dramatic increase in surface temperature, and ultimately, the risk of thermal runaway.

[0114] In summary, this invention proposes an optimized current collector design for lithium-ion batteries. By rationally selecting the functional layer (such as Al2O3), the outer organic matrix / solid electrolyte coating, and the current collector thickness, the thermal stability and safety of the battery under extreme conditions are significantly improved. In the nail penetration test (3 mm diameter steel nail, 10 mm / s penetration speed), the highest surface temperature of the lithium-ion battery is ≤100 °C, without ignition or explosion; in the 10 mΩ external short-circuit test, the highest surface temperature is ≤90 °C, without ignition or explosion; and in the 70% deformation compression test, the highest battery temperature is <120 °C, without ignition or explosion. The excellent performance of this design in nail penetration, compression, and short-circuit tests effectively avoids thermal runaway.

[0115] The foregoing description and accompanying drawings fully illustrate embodiments of the invention to enable those skilled in the art to practice them. Other embodiments may include structural and other changes. The embodiments represent only possible variations. Individual components and functions are optional unless explicitly required, and the order of operation may vary. Some portions and features of some embodiments may be included or substituted for portions and features of other embodiments. Embodiments of the invention are not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from their scope. The scope of the invention is limited only by the appended claims.

Claims

1. A current collector, characterized in that, include: The base layer is made of insulating material; The functional layer is a composite layer structure, consisting of alternating metal layers and metal oxide layers; The coating layer is a solid electrolyte layer; The functional layer is disposed between the base layer and the covering layer.

2. The current collector according to claim 1, characterized in that, The functional layer is composed of multiple metal layers with a metal oxide layer sandwiched between adjacent metal layers.

3. The current collector according to claim 2, characterized in that, The thickness ratio of the metal layer to the metal oxide layer is set to 7-10 :

1.

4. The current collector according to any one of claims 1-3, characterized in that, The thickness ratio of the base layer, the functional layer, and the covering layer is set to 2-6 : 0.5-3 : 0.5-2.

5. The current collector according to claim 4, characterized in that, An adhesive transition layer is provided between the base layer and the functional layer; and / or, the insulating material is selected from one or more composites of polyethylene terephthalate, polypropylene, and polyimide.

6. The current collector according to claim 5, characterized in that, The solid electrolyte layer is composed of an organic matrix and an inorganic fast ion conductor in a mass ratio of 4:1 to 1:

4. The organic matrix is ​​selected from one or more of polyethylene oxide, polyacrylonitrile, and polyvinylidene fluoride; the inorganic fast ion conductor is selected from one or more of lithium aluminum germanium phosphate, lithium lanthanum zirconium oxide, and lithium lanthanum titanium oxide.

7. The current collector according to any one of claims 1-3, characterized in that, Both the functional layer and the covering layer have two layers, which are respectively located on both sides of the base layer.

8. A method for preparing a current collector as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Evaporate the material of the metal layer to deposit it on the side of the substrate layer; S2: Oxidize the outer surface of the metal layer to obtain the metal oxide layer; S3: The material of the metal layer is evaporated and deposited on the outer surface of the metal oxide layer; Repeat step S2 to obtain the functional layer; S4: Spray the slurry of the solid electrolyte layer onto the outer surface of the functional layer.

9. An electrode, characterized in that, Includes the current collector as described in any one of claims 1 to 7, or the current collector obtained by the preparation method described in claim 7.

10. A lithium-ion battery, characterized in that, The current collector includes the current collector as described in any one of claims 1 to 7, or the current collector obtained by the preparation method described in claim 8, or the electrode as described in claim 9; the lithium-ion battery includes lithium iron phosphate, lithium manganese iron phosphate, or a ternary battery system, wherein the ternary battery system is made of LiNi. x Co y Mn z M b O2, 0.7≤x≤0.9, 0.1≤y≤0.3, 0.1≤z≤0.3, 0≤b≤0.25, x+y+z+b=1.

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