Composite current collector with metal material functional layer, preparation method of composite current collector, pole piece and battery

Abstract

The invention discloses a composite current collector with a metal material functional layer, a preparation method of the composite current collector, a pole piece and a battery. The composite current collector comprises a base film layer, a metal layer on the surface of at least one side of the base film layer and a functional layer arranged on the surface of one side, far away from the base film layer, of the metal layer, the functional layer comprises a metal material, the thickness relation ratio of the functional layer to the metal layer is (0.5-10): 1, and the thickness range of the functional layer is 0.5-10 [mu] m; the relation between the electrical resistivity R1 of the functional layer and the electrical resistivity R2 of the metal layer is 105 [omega] mgt; r1gt, R1gt; and R2. Through the three-layer structural design of the base film layer, the metal layer and the metal material functional layer and multi-dimensional parameter gradient control, the core problems that the conductivity and the protective property of a traditional composite current collector are difficult to consider, the interface bonding is weak, the high-temperature stability is poor and the like are effectively solved, and the dual goals of performance balance and industrialization adaptation are achieved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a composite current collector with a functional layer of metallic material, its preparation method, electrode, and battery. Background Technology

[0002] Current mainstream current collector technologies mainly employ single metal foil or simple composite structures. Single metal foil current collectors typically use pure copper or pure aluminum foil with a thickness between 6 and 20 micrometers, prepared through rolling or electrolysis. This material relies on the conductivity of the metal itself, but the grain size is uneven, and it is prone to coarsening at high temperatures, resulting in insufficient mechanical strength and high-temperature stability.

[0003] Simple composite current collectors are composed of a metal layer (such as copper or aluminum) and a polymer base film (such as PET or PP). Although this structure combines the conductivity of metals with the flexibility of polymer base films, it has obvious problems: the interfacial bonding between the metal layer and the base film is weak, and it is prone to delamination during high-temperature processing; the grain growth of the metal layer is uncontrollable, making it difficult to balance conductivity and strength.

[0004] The main shortcomings of existing technologies include: uncontrollable grain growth; during high-temperature heat treatment of traditional metal layers, the grain growth rate is either too fast or too slow. Too fast growth leads to grain coarsening, material embrittlement, and decreased conductivity, while too slow growth results in high energy consumption and low production efficiency; poor interface performance; the thermal expansion coefficients of the metal layer and the functional layer or base film do not match, making it easy to generate microcracks during thermal cycling; insufficient density of the functional layer, which cannot effectively block element diffusion; and limited overall performance; it is difficult to balance conductivity and mechanical strength. Mechanical stability is poor when high conductivity is required, and resistivity increases when high strength is required. Summary of the Invention

[0005] The purpose of this invention is to provide a composite current collector with a functional layer of metallic material, its preparation method, electrode, and battery, thereby improving the high-temperature stability, interface optimization, and performance balance of existing current collectors.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: The first aspect of this application provides a composite current collector having a functional layer of metal material, including a base film layer, a metal layer on at least one surface of the base film layer, and a functional layer disposed on the surface of the metal layer away from the base film layer; the functional layer comprises a metal material. The thickness ratio of the functional layer to the metal layer is 0.5~10:1, and the thickness of the functional layer ranges from 0.5 to 10 μm; the resistivity R1 of the functional layer and the resistivity R2 of the metal layer are related by a ratio of 10:1. 5 Ω m >R1>R2.

[0007] To optimize the above technical solution, the specific limitations also include: The relationship between the particle size of the functional layer and the particle size of the metal layer is that the average particle size of the functional layer is less than or equal to 0.17 times the average particle size of the metal layer.

[0008] The lattice constant difference between the functional layer and the metal layer at their interface is ≤30%.

[0009] Furthermore, the thermal conductivity of the base film layer is less than the thermal conductivity of the functional layer, which in turn is less than the thermal conductivity of the metal layer.

[0010] Furthermore, the thermal conductivity of the base film layer is 0.1~50 W / mK, the thermal conductivity of the functional layer is 50~100 W / mK, and the thermal conductivity of the metal layer is >200 W / mK.

[0011] The second aspect of this application provides a method for preparing a composite current collector with a functional layer of metallic material, comprising the following steps: S1: Prepare a base transition layer on a polymer film substrate; S2: Prepare a metal layer on the surface of the metal underlayer transition layer; S3: Prepare a functional layer containing metallic material on the surface of the metal layer; S4: Perform heat treatment at 500~800℃ to control the growth rate of functional layer grains within the range of 1~50μm / h, then cool to obtain the final composite current collector.

[0012] The heat treatment in step S4 specifically includes the following gradient stages: First gradient stage: The initial composite current collector is heated to 650-800℃ at a rate of 100-120℃ / min and held at that temperature for 2-5 minutes; the metal layer grain growth rate is 25-50μm / h, and the grain size is 2-3μm; in the functional layer, the inner metal material closest to the metal layer receives the energy transferred by the metal layer and recrystallizes rapidly, with a grain growth rate of 40-50μm / h and a grain size of 0.8-1.5μm; Second gradient stage: Then, the temperature is reduced to 450-600℃ at a rate of 15-25℃ / min, and held at this temperature for 4-6 minutes; the growth rate of metal layer grains is reduced to 10-20μm / h, and the grain size continues to grow slowly to a final size of 3-5μm; in the functional layer, the inner metal material grains near the metal layer gradually stop growing, and the metal material grains in the middle part mainly grow in this stage, with a growth rate of 20-30μm / h, and the resulting grain size is 0.2-1μm.

[0013] After the heat treatment in step S4 is stopped, the temperature is reduced to below 300℃ at a cooling rate of 10~15℃ / min; the growth of metal layer grains basically stops; in the functional layer, the metal material grains in the middle part gradually stop growing, and the outermost metal material grains mainly grow in this stage, with a growth rate of 1~10μm / h, and the final grain size is ≤100nm.

[0014] A third aspect of this application provides an electrode comprising the aforementioned composite current collector having a functional layer of metallic material.

[0015] A fourth aspect of this application provides a battery comprising the aforementioned electrode.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention constructs a support-conductivity-protection functional system through a three-layer structure of base film layer-metal layer-metal material functional layer and grain gradient, effectively solving the core problems of traditional composite current collectors such as difficulty in balancing conductivity and protection, weak interface bonding, and poor high-temperature stability, while taking into account both performance balance and industrial adaptability.

[0017] At the structural design level, the appropriate thickness ratio of the functional layer and the metal layer can be adapted to the structural strength and performance requirements of different scenarios, avoiding the functional layer being too thick and affecting conductivity or too thin and losing its protective capability. The resistivity gradient design allows the metal layer to act as a low-resistivity current main channel to reduce Joule heating, while the moderately high resistance of the functional layer achieves controllable heat generation and uniform heat dissipation, avoiding local hot spots and balancing interface protection and current sharing. By limiting the particle size difference between the functional layer and the metal layer, a nano-fine-grained to micro-coarse-grained gradient interface structure is formed. The fine grains of the functional layer improve the interface density and mechanical strength and block the diffusion of high-temperature elements, while the coarse grains of the metal layer ensure a low-resistivity path and reduce grain boundary resistance. The two work together to achieve complementary protective and conductive functions and strengthen the interface bonding. The optimized matching of the lattice constants at the interface between the functional layer and the metal layer improves interface compatibility, reduces the probability of electron scattering and contact resistance, while alleviating thermal cycling stress concentration, inhibiting the initiation and propagation of microcracks, and improving thermal shock resistance and battery cycle life. The thermal conductivity gradient of the three-layer structure creates an orderly heat dissipation path, avoiding heat accumulation and excessive local temperature differences, thus improving overall thermal stability. Through the reasonable combination of the thermal conductivity of each layer, it reduces the aging of the base film, achieves efficient heat regulation, and significantly improves the safety of battery fast charging and its resistance to thermal runaway.

[0018] At the fabrication process level, the design of the underlayer transition layer pretreatment and gradient heat treatment further enhances the overall performance of the current collector and ensures the feasibility of industrialization. The underlayer transition layer can effectively improve the bonding strength between the metal layer and the base film, avoiding delamination problems. Through a heat treatment process with controllable temperature and grain growth rate, combined with a three-stage gradient control of high-temperature rapid heating and holding, slow cooling and holding, and uniform cooling, the grain structure can be regulated. The first gradient stage promotes the rapid formation of basic micron-sized grains in the metal layer, and the inner side of the functional layer rapidly recrystallizes with the help of the metal layer energy, improving the interface bonding and conductivity continuity. The second gradient stage allows the metal layer grains to grow slowly to the target size, and the grains in the middle part of the functional layer develop in an orderly manner to form a grain size gradient, taking into account both conductivity and structural density. The cooling stage stops the growth of metal layer grains to stabilize low resistance characteristics, and nanoscale fine grains are formed on the outermost side of the functional layer. Finally, a gradient grain structure is formed in the functional layer, further enhancing the synergistic effect of protection, current equalization, and heat dissipation. Overall, this invention achieves a balance between high-temperature stability, interfacial bonding performance, conductivity, protection, and heat dissipation of composite current collectors through the synergistic effect of grain growth rate control and multi-dimensional gradient structure design. It not only suppresses performance degradation caused by abnormal grain growth, but also extends battery cycle life through structural optimization. Furthermore, the process is compatible with existing technologies and is easy to scale up and apply. Detailed Implementation

[0019] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.

[0021] This invention provides a composite current collector with a metal material functional layer, comprising a base film layer, a metal layer on at least one surface of the base film layer, and a functional layer disposed on the surface of the metal layer away from the base film layer; the functional layer comprises a metal material. The thickness ratio of the functional layer to the metal layer is 0.5~10:1, and the thickness range of the functional layer is 0.5~10μm. This structure establishes a functional system of support-conductivity-protection. The appropriate thickness ratio can be adapted to the structural strength and performance requirements of different scenarios as needed, avoiding the functional layer from being too thick and affecting conductivity or too thin and losing its protective capability.

[0022] The relationship between the resistivity R1 of the functional layer and the resistivity R2 of the metal layer is 10. 5 Ω m>R1>R2. The resistivity gradient design allows the metal layer to serve as the low-resistivity current main channel, reducing Joule heating. The moderately high resistance of the functional layer enables controllable heating and uniform heat dissipation, avoiding local hot spots. At the same time, it takes into account interface protection, current sharing, and the activation of temperature-sensitive protection mechanisms, solving the problem that traditional current collectors cannot balance conductivity and protection.

[0023] In some embodiments, the relationship between the particle size of the functional layer and the particle size of the metal layer is that the average particle size of the functional layer is ≤ the average particle size of the metal layer × 0.17.

[0024] By limiting the particle size of the functional layer and the metal layer, a gradient interface structure of nano-fine grains to micro-coarse grains is formed. The fine grains of the functional layer can improve the interface density and mechanical strength, effectively blocking the element diffusion between the metal layer and the functional layer at high temperatures. The coarse grains of the metal layer ensure a low-resistance pathway and reduce grain boundary resistance. The two work together to achieve complementary protection and conductivity functions, while strengthening the interface bonding force and reducing interface defects, laying the microstructure foundation for subsequent performance optimization.

[0025] In some implementations, the lattice constant difference between the functional layer and the metal layer at their interface is ≤30%. This optimizes interface compatibility, significantly reduces interface dislocation density, lowers the probability of electron scattering at the interface, reduces interface contact resistance, and alleviates stress concentration caused by lattice mismatch during thermal cycling. This effectively suppresses microcrack initiation and propagation, improves the thermal shock resistance of the current collector, extends battery cycle life, and solves the problem of weak interface bonding in traditional composite current collectors.

[0026] In some implementations, the thermal conductivity of the base film layer is less than that of the functional layer, which in turn is less than that of the metal layer. A thermal conductivity gradient is constructed to achieve directional heat dissipation and temperature control: this creates an orderly heat dissipation path from the base film to the metal layer, preventing heat accumulation at the base film or interface, effectively reducing local temperature differences, and improving the overall thermal stability of the current collector; simultaneously, it provides a thermal environment basis for subsequent control of grain growth rate, ensuring uniform microstructure development in each layer and preventing abnormal grain growth due to local overheating.

[0027] In some embodiments, the thermal conductivity of the base film layer is 0.1~50 W / mK, the thermal conductivity of the functional layer is 50~100 W / mK, and the thermal conductivity of the metal layer is >200 W / mK. The low thermal conductivity of the base film reduces heat conduction to the substrate, preventing substrate aging; the thermal conductivity of the functional layer enables heat buffering and uniform distribution; and the high thermal conductivity of the metal layer rapidly dissipates heat. The synergy of these three factors results in a smaller temperature rise of the base film during 5C fast charging and a lower peak temperature during short circuits, significantly improving battery fast charging safety and resistance to thermal runaway.

[0028] This invention also provides a method for preparing a composite current collector with a metallic material functional layer, comprising the following steps: S1: Prepare a base transition layer on a polymer film substrate; S2: Prepare a metal layer on the surface of the metal underlayer transition layer; S3: Prepare a functional layer containing metallic material on the surface of the metal layer; S4: Perform heat treatment at 500~800℃ to control the growth rate of functional layer grains within the range of 1~50μm / h, then cool to obtain the final composite current collector.

[0029] The underlayer transition layer enhances the bonding strength between the metal layer and the base film, preventing delamination. The controlled-speed heat treatment can suppress abnormal grain growth in the functional layer, avoiding both excessively fast rates that lead to grain coarsening and embrittlement, and excessively slow rates that lead to high energy consumption. At the same time, it ensures the compatibility of the microstructure between the functional layer and the metal layer, enabling the current collector to achieve high-temperature stability, high conductivity, and mechanical strength. Furthermore, the process is compatible with existing vapor deposition and electroplating technologies, making it easy to industrialize.

[0030] The heat treatment in step S4 specifically includes the following gradient stages: First gradient stage: The initial composite current collector is heated to 650-800℃ at a rate of 100-120℃ / min and held at that temperature for 2-5 minutes; the metal layer grain growth rate is 25-50μm / h, and the grain size is 2-3μm; in the functional layer, the inner metal material closest to the metal layer receives the energy transferred by the metal layer and recrystallizes rapidly, with a grain growth rate of 40-50μm / h and a grain size of 0.8-1.5μm; Second gradient stage: Then, the temperature is reduced to 450-600℃ at a rate of 15-25℃ / min, and held at this temperature for 4-6 minutes; the growth rate of metal layer grains is reduced to 10-20μm / h, and the grain size continues to grow slowly to a final size of 3-5μm; in the functional layer, the inner metal material grains near the metal layer gradually stop growing, and the metal material grains in the middle part mainly grow in this stage, with a growth rate of 20-30μm / h, and the resulting grain size is 0.2-1μm.

[0031] After the heat treatment in step S4 is stopped, the temperature is reduced to below 300℃ at a cooling rate of 10~15℃ / min; the growth of metal layer grains basically stops; in the functional layer, the metal material grains in the middle part gradually stop growing, and the outermost metal material grains mainly grow in this stage, with a growth rate of 1~10μm / h, and the final grain size is ≤100nm.

[0032] The first gradient stage involves rapid heating and holding at high temperatures, which allows the metal layer to quickly form basic micron-sized grains. The inner side of the functional layer rapidly recrystallizes with the help of the metal layer's energy, forming a grain structure that adapts to the interface and improving interfacial bonding and electrical continuity. The second gradient stage involves slow cooling and holding, which allows the metal layer grains to grow slowly to the target size. The grains in the middle part of the functional layer develop in an orderly manner, forming a grain size gradient. This balances electrical conductivity and structural density, laying the groundwork for grain refinement in the subsequent low-temperature stage and avoiding stress concentration in the overall structure.

[0033] The cooling rate is matched with the grain growth pattern to improve the gradient grain structure of the functional layer and stabilize the overall performance: the growth of the metal layer grains stops, ensuring the stability of low resistance characteristics; nanoscale fine grains are formed on the outermost side of the functional layer, which further improves the interface density and mechanical strength, effectively blocking element diffusion. At the same time, the entire functional layer forms a gradient grain structure with coarser inner side, moderate middle side and ultrafine outer side, which enhances the synergistic effect of protection, current equalization and heat dissipation, and extends the battery cycle life.

[0034] This invention solves the following problems by controlling the growth rate of metal layer grains and designing the functional layer-metal layer gradient structure: High-temperature stability: Inhibits abnormal grain growth and avoids brittleness or electrical conductivity degradation.

[0035] Interface optimization: By gradient matching between the functional layer metal nanocrystals and the metal layer micron coarse grains, the bonding force and thermal shock resistance are improved.

[0036] Performance balance: By combining the low resistivity of the metal layer, the high density of the functional layer, and the gradient design of the low thermal conductivity of the metal layer with that of the functional layer, the composite current collector achieves high electrical conductivity, high mechanical strength, and heat dissipation capability.

[0037] In some embodiments, the metal layer is selected from copper, aluminum, nickel, titanium or alloys thereof; the functional layer is prepared by magnetron sputtering, electron beam evaporation, electroplating, electroless plating or pulsed laser deposition; the metal material of the functional layer can be selected from nickel, chromium, titanium, tungsten, molybdenum, tantalum, zinc, silver, and nitrides, carbides or alloys of the above metals.

[0038] When the metal layer is aluminum foil, the preferred metal material for the functional layer is aluminum, nickel, or chromium, and optional is titanium or zinc; when the metal layer is copper foil, the preferred metal material for the functional layer is nickel, tin, zinc, silver, chromium, titanium, or tantalum, and optional is tungsten or molybdenum.

[0039] In some embodiments of the present invention, the metal layer may be selected from a metal with good electrical conductivity, such as copper, aluminum, nickel, titanium, or alloys thereof. The functional layer is prepared by methods such as magnetron sputtering, electron beam evaporation, electroplating, electroless plating, or pulsed laser deposition. The metal material may be selected from nickel, chromium, titanium, tungsten, molybdenum, tantalum, zinc, silver, and nitrides, carbides, or alloys of the above metals to provide the required density, mechanical strength, and interfacial properties. The matching of the metal layer and functional layer materials must consider interfacial compatibility and electrochemical stability: when the metal layer is aluminum or an aluminum alloy, the functional layer is preferably aluminum, nickel, or chromium. Using homogeneous aluminum as the functional layer achieves optimal interfacial bonding; nickel and chromium provide higher mechanical strength and corrosion resistance, but the heat treatment process needs to be controlled to optimize the interfacial reaction. When the metal layer is copper or a copper alloy, the functional layer is preferably nickel, tin, zinc, silver, chromium, titanium, or tantalum. Nickel and copper can form a strong metallurgical bond, making them an excellent choice; refractory metals such as chromium, titanium, and tantalum can serve as highly efficient diffusion barrier layers. By rationally matching the above materials and combining them with the grain growth rate control of this invention, a composite current collector with high conductivity, high mechanical strength and excellent high temperature stability can be synergistically achieved.

[0040] The present invention also provides an electrode comprising the above-mentioned composite current collector having a functional layer of metallic material.

[0041] The present invention also provides a battery comprising the above-described electrode.

[0042] This invention achieves improved electrode performance and battery compatibility through the above-described solution: The high conductivity of the current collector can reduce the body resistance of the electrode, improve the uniformity of current distribution, and avoid local polarization of the electrode; the high density of the functional layer can reduce electrolyte erosion and element diffusion, and inhibit electrode aging; the excellent mechanical strength and high temperature stability make the electrode less prone to breakage and deformation during winding and charge-discharge cycles, improving the electrode processing yield and cycle reliability.

[0043] Batteries incorporating this electrode feature a gradient structure and controlled performance of the current collector, resulting in high energy density, fast charging capability, and safety, while extending cycle life. Reduced interface contact resistance and improved heat dissipation capacity enhance battery charging and discharging efficiency and reduce Joule heat loss. Enhanced resistance to thermal runaway and cyclic stress significantly reduces the risks of battery bulging and short circuits, making it suitable for diverse applications such as general-purpose, high-energy-density, and high-current applications.

[0044] The technical solution of the present invention will be further described in detail below with reference to specific embodiments: Example 1 In this embodiment, the polymer base film is made of PET and has a thickness of 6 μm; the metal layer is made of copper and has a thickness of 2 μm; the functional layer is made of nickel and has a thickness of 2 μm, with a thickness ratio of 1:1 between the functional layer and the metal layer. The preparation method of this functional current collector includes the following steps: 1. Place the commercially available PET film in the magnetron sputtering chamber and evacuate to a vacuum level of 5×10⁻⁶. -3 Pa, argon gas with a flow rate of 50 sccm was introduced, sputtering was performed using copper target and nickel-chromium alloy target (target ratio 13:1), power of 200W, deposition time of 5min, to form a base transition layer with a thickness of 6nm; 2. The plated part obtained in step 1 is used as the cathode, and a pure copper plate is used as the anode. The plating solution composition includes: 120 g / L CuSO4, 120 g / L H2SO4, and 60 ppm Cl. - The transition layer was thickened to a 2μm copper metal layer by using 20ppm pyridinium propane sulfonate (PPS) and 20ppm N,N-diethylpropynylamine formate (PABS) with a current density of 1.2A / dm² and an electroplating time of 4min. 3. Using the plated part obtained in step 2 as the cathode and a pure nickel plate as the anode, the plating solution composition includes: 300 g / L NiSO4·6H2O, 150 g / L NiCl2·6H2O, and 52 g / L H3BO3, with the current density set at 2.5 A / dm³. 2 The electroplating time was 3 min 14 s, and a 2 μm nickel functional layer was obtained; 4. Synergistic gradient heat treatment The composite current collector with the deposited functional layer is then placed in an inert gas-protected (argon atmosphere) tubular annealing furnace for heat treatment. This step uses a precisely designed heat treatment curve to simultaneously control the recrystallization / growth of the metal layer and the gradient structuring of the functional layer. Heat treatment process: (1) First stage (rapid recrystallization and interfacial bonding): raise the temperature to 650℃ at a rate of 100℃ / min and hold for 3 minutes; Cu metal layer: At this high temperature, the cold-worked copper layer undergoes rapid recrystallization and grain growth; its grain growth rate is controlled at ~30μm / h, and the grains grow from the initial 1-2μm to about 2-3μm, forming a stable low-resistance path. Ni functional layer: At the same time, the nickel layer near the copper layer receives the highest energy and undergoes rapid recrystallization, with rapid grain growth (rate ~45 μm / h), forming the first metal material layer (relatively coarse grains, with a grain size of about 0.8-1 μm). This layer interdiffusion occurs at the interface with the copper layer, forming a strong metallurgical bond, while reducing the interfacial contact resistance. (2) Second stage (structural stabilization and gradient transition): The furnace temperature is slowly reduced to 550℃ at a rate of 20℃ / min, and held at this temperature for 5 minutes; Cu metal layer: The metal layer grains continue to grow slowly to the final size of ~3-4μm, the growth rate drops to ~15μm / h, and the structure tends to be stable; Ni functional layer: This stage corresponds to the middle part of the functional layer. The grain growth rate drops to ~25μm / h, forming a second metal material layer of appropriate size, which plays a transitional role. This structure achieves a balance between density and conductivity, and plays a role in stress buffering and transition. (3) Third stage (surface densification): Turn off the heating power and let the sample cool with the furnace (average cooling rate of about 10-15℃ / min) to below 300℃ before taking it out; Cu metal layer: Grain growth has essentially ceased; Ni functional layer: During the slow cooling process, the growth of grains on the outermost side of the functional layer is effectively suppressed (rate <5μm / h), thus preserving the nanoscale fine-grained structure (third metal material layer) and achieving high density and mechanical strength.

[0045] In this embodiment, the resistivity R1 of the functional layer is 3.5 × 10⁻⁶. -7 Ω m, the resistivity R2 of the metal layer is 1.72×10 m. -8 Ω m; the average particle size of the metal layer is 3.5 μm, and the average particle size of the functional layer is 0.3 μm; at the interface, the lattice constant of the metal layer is 0.3615 nm, and the lattice constant of the functional layer is 0.3524 nm; the base film layer is carbonized during heat treatment, and its thermal conductivity is 25 W / mK; the thermal conductivity of the functional layer is 70 W / mK, and the thermal conductivity of the metal layer is 401 W / mK.

[0046] Example 2 Step 3 in this embodiment is: The plated part obtained in step 2 is used as the cathode, and the pure tin plate is used as the anode. The plating solution composition includes: 8 mL / L Sn 2+ 80 mL / L methanesulfonic acid, 0.8 g / L stabilizer, 0.24 g / L HG11 brightener, with a current density set at 2.5 A / dm³. 2 The electroplating time was 10 min, resulting in a 2 μm tin functional layer; Everything else is the same as in Example 1.

[0047] In this embodiment, the resistivity R1 of the functional layer is 1.8 × 10⁻⁶. -7 Ω m, the resistivity R2 of the metal layer is 1.72×10 m. -8 Ω m; the average particle size of the metal layer is 3.5 μm, and the average particle size of the functional layer is 0.32 μm; at the interface, the lattice constant of the metal layer is 0.3615 nm, and the lattice constant of the tin-nickel alloy functional layer is adjusted to 0.3780 nm, with a lattice difference of about 4.6%; the base film layer is carbonized during heat treatment, and its thermal conductivity is 25 W / mK; the thermal conductivity of the functional layer is 62 W / mK, and the thermal conductivity of the metal layer is 401 W / mK.

[0048] Example 3 Steps 1 to 3 in this embodiment are as follows: 1. Place the commercially available PET film in the magnetron sputtering chamber and evacuate to a vacuum level of 5×10⁻⁶. -3 Pa, argon gas with a flow rate of 50 sccm was introduced, and sputtering was performed using aluminum target and nickel-chromium alloy target (target ratio 13:1), with a power of 200W and a deposition time of 5 min, to form a base transition layer with a thickness of 6 nm. 2. The transition layer of the plated part obtained in step 1 is thickened by vacuum evaporation to obtain a 2μm aluminum metal layer; 3. Using the plated part obtained in step 2 as the cathode and a pure nickel plate as the anode, the plating solution composition includes: 300 g / L NiSO4·6H2O, 150 g / L NiCl2·6H2O, and 52 g / L H3BO3, with the current density set at 2.5 A / dm³. 2 The electroplating time was 3 min 14 s, and a 2 μm nickel functional layer was obtained; Everything else is the same as in Example 1.

[0049] In this embodiment, the resistivity R1 of the functional layer is 3.5 × 10⁻⁶. -7 Ω m, the resistivity R2 of the metal layer is 2.68 × 10 m. -8 Ω m; the average particle size of the metal layer is 4.0 μm; the average particle size of the functional layer is 0.35 μm; at the interface, the lattice constant of the metal layer is 0.4050 nm; the lattice constant of the functional layer is 0.3524 nm; the base film is carbonized during heat treatment and has a thermal conductivity of 25 W / mK; the thermal conductivity of the functional layer is 70 W / mK, and the thermal conductivity of the metal layer is 237 W / mK.

[0050] Example 4 The scheme in this embodiment is basically the same as that in embodiment 1, except that the thickness of the copper metal layer in this embodiment is 2μm; the thickness of the nickel functional layer is 1μm, and the thickness ratio of the functional layer to the metal layer is 0.5:1.

[0051] In this embodiment, the resistivity R1 of the functional layer is 3.4 × 10⁻⁶. -7 Ω m, the functional layer structure is more compact, and the resistivity is slightly reduced; the resistivity R2 of the metal layer is 1.72×10 -8 Ω m; the average particle size of the metal layer is 3.5 μm, and the average particle size of the functional layer is 0.25 μm, with the functional layer having finer grains; at the interface, the lattice constant of the metal layer is 0.3615 nm, and the lattice constant of the functional layer is 0.3524 nm; the base film layer is carbonized during heat treatment, with a thermal conductivity of 25 W / mK; the thermal conductivity of the functional layer is 69 W / mK, and the thermal conductivity of the metal layer is 401 W / mK.

[0052] Example 5 The scheme in this embodiment is basically the same as that in embodiment 1, except that the thickness of the copper metal layer in this embodiment is 1 μm; the thickness of the nickel functional layer is 3 μm, and the thickness ratio of the functional layer to the metal layer is 3:1.

[0053] In this embodiment, the resistivity R1 of the functional layer is 3.6 × 10⁻⁶. -7 Ω m, the functional layer has slightly coarser grains and a slight increase in resistivity; the resistivity R2 of the metal layer is 1.71×10 -8 Ω m; the average particle size of the metal layer is 3.0 μm, and the growth of metal layer grains is restricted; the average particle size of the functional layer is 0.32 μm; at the interface, the lattice constant of the metal layer is 0.3615 nm, and the lattice constant of the functional layer is 0.3524 nm; the base film layer is carbonized during heat treatment, and its thermal conductivity is 25 W / mK; the thermal conductivity of the functional layer is 71 W / mK, and the thermal conductivity of the metal layer is 400 W / mK.

[0054] Example 6 The scheme in this embodiment is basically the same as that in embodiment 1, except that the thickness of the copper metal layer in this embodiment is 1 μm; the thickness of the nickel functional layer is 5 μm, and the thickness ratio of the functional layer to the metal layer is 5:1.

[0055] In this embodiment, the resistivity R1 of the functional layer is 3.7 × 10⁻⁶. -7 Ω m, the resistivity R2 of the metal layer is 1.70×10 m. -8 Ω m; the average particle size of the metal layer is 2.8 μm, and the average particle size of the functional layer is 0.38 μm; at the interface, the lattice constant of the metal layer is 0.3615 nm, and the lattice constant of the functional layer is 0.3524 nm; the base film layer is carbonized during heat treatment, and its thermal conductivity is 25 W / mK; the thermal conductivity of the functional layer is 73 W / mK, and the thermal conductivity of the metal layer is 399 W / mK.

[0056] Example 7 The scheme in this embodiment is basically the same as that in embodiment 1, except that: the functional layer is made of chromium metal material, and the heat treatment parameters are adjusted so that the lattice constant of the metal layer (copper) at the interface is 0.3615nm and the lattice constant of the functional layer (chromium) is 0.4700nm, with the difference in lattice constant being exactly 30%.

[0057] In this embodiment, the resistivity R1 of the functional layer is 4.0 × 10⁻⁶. -7 Ω m, the resistivity of the chromium-based functional layer is slightly higher; the resistivity R2 of the metal layer is 1.72 × 10⁻⁶. -8 Ω m; the average particle size of the metal layer is 3.5 μm, and the average particle size of the functional layer is 0.32 μm; the base film layer is carbonized during heat treatment and has a thermal conductivity of 25 W / mK; the thermal conductivity of the functional layer is 75 W / mK, and the thermal conductivity of the metal layer is 401 W / mK.

[0058] Example 8 The scheme in this embodiment is basically the same as that in embodiment 1, except that the material and heat treatment parameters of the functional layer and the metal layer are adjusted to reverse the order of thermal conductivity, that is, the thermal conductivity of the base film layer < the thermal conductivity of the metal layer < the thermal conductivity of the functional layer.

[0059] Specific adjustments: The metal layer is made of titanium alloy (low thermal conductivity copper-titanium alloy, copper-titanium mass ratio 9:1), and the functional layer is made of tungsten-molybdenum alloy (high thermal conductivity tungsten-molybdenum alloy, tungsten-molybdenum mass ratio 7:3); other preparation steps and parameters are the same as in Example 1.

[0060] In this embodiment, the resistivity R1 of the functional layer is 4.2 × 10⁻⁶. -7 Ω m; the resistivity R2 of the metal layer is 1.72 × 10 m. -8 Ω m; the average particle size of the metal layer is 3.5 μm, and the average particle size of the functional layer is 0.30 μm; at the interface, the lattice constant of the metal layer is 0.3615 nm, and the lattice constant of the functional layer is 0.3580 nm; the base film layer is not completely carbonized, and the thermal conductivity is stable at 0.1 W / mK.

[0061] Comparative Example 1 This comparative heat treatment procedure does not have a second stage (structural stabilization and gradient transition). The temperature is raised to 650°C at a rate of 100°C / min and held for 3 minutes before the heating power is turned off. The sample is then allowed to cool with the furnace (average cooling rate of about 10-15°C / min) to below 300°C before being removed. Other procedures are the same as in Example 1.

[0062] In this comparative example, the resistivity R1 of the functional layer is 4.2 × 10⁻⁶. -7 Ω m, without a transition stage, with disordered grain structure and increased resistivity; the resistivity R2 of the metal layer is 1.80 × 10 -8 Ω The resistivity increases due to uneven grain growth. The average grain size of the metal layer is 2.5 μm, and the rapid cooling results in insufficient and uneven grain growth. The average grain size of the functional layer is 0.45 μm, with uneven grain size and an overall coarse appearance. At the interface, the lattice constant of the metal layer is 0.3625 nm, while that of the functional layer is 0.3545 nm, with a lattice difference of approximately 2.2%, but the interface structure is disordered. The base film layer carbonizes during heat treatment, resulting in a thermal conductivity of 25 W / mK. The thermal conductivity of the functional layer is 65 W / mK, with a disordered structure and decreased thermal conductivity. The thermal conductivity of the metal layer is 390 W / mK, with uneven grain size and decreased thermal conductivity.

[0063] Comparative Example 2 The heat treatment procedure for this comparative example is as follows: First stage (rapid recrystallization and interfacial bonding): raise the temperature to 500℃ at a rate of 80℃ / min and hold for 3 minutes; The second stage (structural stabilization and gradient transition): the furnace temperature is slowly reduced to 400℃ at a rate of 10℃ / min, and held at this temperature for 5 minutes. The third stage (surface densification): turn off the heating power and allow the sample to cool with the furnace (average cooling rate of about 10-15℃ / min) to below 300℃ before taking it out.

[0064] In this comparative example, the resistivity R1 of the functional layer is 4.8 × 10⁻⁶. -7 Ω m, low temperature leads to insufficient recrystallization, resulting in a significant increase in resistivity. The resistivity R2 of the metal layer is 1.90 × 10⁻⁶. -8 Ω Low temperature inhibits copper recrystallization, leading to an increase in resistivity. The average grain size of the metal layer is 2.0 μm, indicating slow grain growth at low temperatures. The average grain size of the functional layer is 0.50 μm, showing insufficient grain refinement and a loose structure. At the interface, the lattice constant of the metal layer is 0.3610 nm, while that of the functional layer is 0.3520 nm, with a lattice difference of approximately 2.6%, but no effective metallurgical bonding occurs at the interface. During heat treatment, the base film layer partially carbonizes into a mixture of carbon and organic matter, resulting in a thermal conductivity of 10 W / mK. The thermal conductivity of the functional layer is 62 W / mK, indicating a loose structure and a decrease in thermal conductivity. The thermal conductivity of the metal layer is 385 W / mK, indicating fine and uneven grains and a decrease in thermal conductivity.

[0065] Comparative Example 3 This comparative example uses a conventional copper composite current collector with a 6μm thick PET film, a 6nm thick copper-nickel underlay transition layer, a 4μm thick copper metal layer, and no functional layer.

[0066] In this comparative example, the resistivity of the metal layer is 1.75 × 10⁻⁶. -8 Ω m; the average particle size of the metal layer is 4.5 μm; the thermal conductivity of the base film is 0.25 W / mK, and the thermal conductivity of the metal layer is 402 W / mK.

[0067] Comparative Example 4 The scheme of this comparative example is basically the same as that of Example 1, except that: the functional layer is made of molybdenum metal material, and the heat treatment parameters are adjusted so that the lattice constant of the metal layer (copper) at the interface is 0.3615 nm and the lattice constant of the functional layer (molybdenum) is 0.4880 nm, with a lattice constant difference of 35%.

[0068] In this comparative example, the resistivity R1 of the functional layer is 5.2 × 10⁻⁶. -7 Ω The large lattice difference leads to numerous interface defects and a significant increase in resistivity; the resistivity R2 of the metal layer is 1.85 × 10⁻⁶. -8 Ω m; the average particle size of the metal layer is 3.5 μm, and the average particle size of the functional layer is 0.38 μm; the base film layer is carbonized during heat treatment, and its thermal conductivity is 25 W / mK; the thermal conductivity of the functional layer is 78 W / mK, and the thermal conductivity of the metal layer is 401 W / mK; the interface bonding is loose and delamination is prone to occur.

[0069] Comparative Example 5 The scheme of this comparative example is basically the same as that of Example 1, except that the thickness of the copper metal layer is 4 μm and the thickness of the nickel functional layer is 1 μm, and the thickness ratio of the functional layer to the metal layer is 0.25:1.

[0070] In this comparative example, the resistivity R1 of the functional layer is 3.9 × 10⁻⁶. -7 Ω m, the functional layer is too thin, resulting in a porous structure and increased resistivity; the resistivity R2 of the metal layer is 1.72×10. -8 Ω m; the average particle size of the metal layer is 3.8 μm, and the average particle size of the functional layer is 0.32 μm; at the interface, the lattice constant of the metal layer is 0.3615 nm, and the lattice constant of the functional layer is 0.3524 nm; the base film layer is carbonized during heat treatment, and its thermal conductivity is 25 W / mK; the thermal conductivity of the functional layer is 80 W / mK, and the thermal conductivity of the metal layer is 401 W / mK.

[0071] The tensile strength of this comparative example is 215 MPa, indicating that the functional layer is too thin and the mechanical strength is significantly reduced; the sheet resistance is 29 mΩ, indicating that the functional layer is not sufficiently supported and the current conduction is uneven; the adhesion is 28 N / m, indicating that the interfacial bonding area is insufficient and the bonding force is weakened; the sheet resistance increases by 72.3% after cycling, indicating that the functional layer cannot effectively block element diffusion and the performance deteriorates severely after high-temperature cycling.

[0072] Comparative Example 6 The scheme of this comparative example is basically the same as that of Example 1, except that the thickness of the copper metal layer is 1 μm and the thickness of the nickel functional layer is 12 μm, and the thickness ratio of the functional layer to the metal layer is 12:1.

[0073] In this comparative example, the resistivity R1 of the functional layer is 4.1 × 10⁻⁶. -7 Ω m, excessively thick functional layers lead to uneven grain growth and increased resistivity; the resistivity R2 of the metal layer is 1.70×10 -8 Ω m; the average particle size of the metal layer is 2.7 μm, and the average particle size of the functional layer is 0.42 μm; at the interface, the lattice constant of the metal layer is 0.3615 nm, and the lattice constant of the functional layer is 0.3524 nm; the base film layer is carbonized during heat treatment, and its thermal conductivity is 25 W / mK; the thermal conductivity of the functional layer is 67 W / mK, and the thermal conductivity of the metal layer is 398 W / mK.

[0074] The tensile strength of this comparative example is 356 MPa. The functional layer is too thick, which slightly improves the mechanical strength, but the redundancy is too large. The sheet resistance is 38 mΩ, which is caused by the excessive thickness of the functional layer, resulting in an increase in overall resistance. The adhesion is 32 N / m, which is caused by stress concentration at the interface and a decrease in bonding strength. The sheet resistance growth rate after cycling is 68.9%, which is caused by excessive internal stress in the functional layer, making it easy to generate microcracks during cycling.

[0075] Comparative Example 7 The scheme of this comparative example is basically the same as that of Example 1, except that: tungsten metal is used for the functional layer, the heat treatment parameters are adjusted to shorten the first-stage holding time to 1 minute, and the resistivity R1 of the functional layer is 1.2 × 10⁻⁶. -5 Ω m, the resistivity R2 of the metal layer is 1.72×10 m. -8 Ω m.

[0076] In this comparative example, the average particle size of the metal layer is 3.5 μm, and the average particle size of the functional layer is 0.33 μm; at the interface, the lattice constant of the metal layer is 0.3615 nm, and the lattice constant of the functional layer (tungsten) is 0.3165 nm; the base film is carbonized during the heat treatment process, and its thermal conductivity is 25 W / mK; the thermal conductivity of the functional layer is 74 W / mK, and the thermal conductivity of the metal layer is 401 W / mK.

[0077] The tensile strength of this comparative example is 302 MPa; the sheet resistance is 89 mΩ, indicating that the resistivity of the functional layer is too high; the adhesion is 41 N / m, indicating good interfacial bonding; the sheet resistance increases by 81.5% after cycling, indicating that the high resistance of the functional layer leads to excessive Joule heating.

[0078] Comparative Example 8 The scheme of this comparative example is basically the same as that of Example 1, except that the metal layer is replaced with aluminum, the functional layer is replaced with silver, and the corresponding preparation steps are adjusted to adapt to the material properties. Other preparation steps and heat treatment parameters are the same as those in Example 1. The specific steps are adjusted as follows: 1. Place the commercially available PET film in the magnetron sputtering chamber and evacuate to a vacuum level of 5×10⁻⁶. -3 Pa, argon gas with a flow rate of 50 sccm was introduced, and sputtering was performed using aluminum target and nickel-chromium alloy target (target ratio 13:1), with a power of 200W and a deposition time of 5 min, to form a base transition layer with a thickness of 6 nm. 2. The transition layer of the plated part obtained in step 1 is thickened by vacuum evaporation to obtain a 2μm aluminum metal layer; 3. Using the plated part obtained in step 2 as the cathode and the pure silver plate as the anode, and adapting the plating solution composition to the silver plating, the current density is set to 2.5 A / dm³. 2 By adjusting the electroplating time, a 2μm silver functional layer was obtained; In this comparative example, the resistivity R1 of the functional layer is 1.65 × 10⁻⁶. -8 Ω m, the resistivity R2 of the metal layer is 2.68 × 10 m. -8 Ω m; the functional layer material is silver; the average particle size of the metal layer is 4.0 μm, and the average particle size of the functional layer is 0.4 μm; at the interface, the lattice constant of the metal layer (aluminum) is 0.405 nm, and the lattice constant of the functional layer (silver) is 0.4085 nm; the base film is carbonized during heat treatment, and its thermal conductivity is 25 W / mK; the thermal conductivity of the functional layer is 425 W / mK, and the thermal conductivity of the metal layer is 237 W / mK.

[0079] The tensile strength of this comparative example is 231 MPa, indicating poor material compatibility and moderate mechanical strength; the sheet resistance is 21 mΩ, indicating that the resistivity of the functional layer is too low, making it impossible to achieve controllable heating and uniform heat dissipation; the adhesion is 35 N / m, indicating weak interfacial bonding between the aluminum metal layer and the silver functional layer; the sheet resistance increases by 43% after cycling, indicating insufficient interfacial compatibility and performance degradation during cycling.

[0080] The testing method is as follows: (1) Tensile strength: Place the functional current collector between the clamps of the universal electronic testing instrument, ensuring that the sample is flat and wrinkle-free, and that its long axis is parallel to the direction of tension; start the tensile testing machine and begin to separate the clamping points at the standard specified rate to apply tension to the sample; when the sample reaches the rupture point and breaks, record and display the corresponding load value. At this time, record the load value required for the sample to break as the tensile strength.

[0081] (2) Sheet resistance: Place the functional current collector on the sample stage and use a four-probe sheet resistance meter to test the sheet resistance of the sample.

[0082] (3) Electrode adhesion: (3.1) Electrode preparation: ① Homogenization: a. Premixing (dry mixing): Add a certain amount of NCM811 (LiNi) to a double planetary mixer (vacuum type). 0.8 Co 0.1 Mn 0.1 a) Add O2) and conductive agent (carbon nanotubes:Super P=1:1), and stir for 10 min under vacuum of -0.08 MPa and 500 rpm; b) First wet mixing: Add polyvinylpyrrolidone copper (NMP) to the above mixture and stir for 30 min under 1500 rpm and 40°C; c) Second wet mixing: Add polyvinylidene fluoride (PVDF) to the above mixture and stir for 60 min under 2000 rpm; d) Defoaming treatment: Stir for 20 min under vacuum of -0.095 MPa and 500 rpm to obtain a slurry with a solid content of 65 wt% and a viscosity of 4500 cP (25°C), wherein the solid content of NCM, conductive agent and PVDF are 96 wt%, 2 wt% and 2 wt%, respectively. ② Coating: Based on the functional current collector prepared above, the prepared slurry is placed in a coating machine for double-sided coating. The coating parameters are: coating speed 25 m / min, areal density 23.5 mg / cm³. 2 ① Drying temperature: 80℃ (Zone 1) → 110℃ (Zone 2) → 90℃ (Zone 3); air velocity: 12m / s (crossflow hot air). ③ Roll pressing: Place the baked electrode sheets in a roller press for rolling treatment. Parameters: linear pressure 3000N / mm, compaction density 3.5g / cm³. 3 ④ Die-cutting: The prepared electrode is placed in a die-cutting machine and cut into 40mm×60mm samples. ⑤ Edge sealing layer preparation: The cut samples are placed in a precision spraying machine, using polyethylene as raw material, melted at 280℃ and kept at that temperature, and sprayed onto the edges of the electrode to form an edge sealing layer with a thickness of 5μm.

[0083] (3.2) Adhesion test: Under room temperature (25℃) conditions, take a 20mm wide and 120mm long double-sided tape and stick it on a stainless steel plate. Cut an electrode sheet with a size of 50mm×125mm. Then, evenly stick the cut electrode sheet sample on the double-sided tape, with the double-sided tape in the center of the test sample. Use a 2kg standard small pressure roller to press back and forth twice. After completion, take a tape of the same size as the tape on the stainless steel plate and stick it on the sample surface, aligning it with the tape below the sample. Use a 2kg standard small pressure roller to press back and forth twice. Then, fix the prepared sample to the clamp of the peel force testing device and stretch it at an angle of 180° and a speed of 100mm / min. The width is set to the width of the tape. After the test, read the peel force value as the electrode sheet adhesion force.

[0084] (4) Thermal shock resistance: First, an electrode with an active material coating is prepared as a sample to truly reflect the thermal stress under battery operating conditions. The test is carried out in a thermal shock test chamber, with two temperature zones set: high temperature (80℃) and low temperature (-20℃). The sample is rapidly switched between the temperature zones by a high-speed airflow to achieve rapid cooling / heating of the air. The sample stays at each temperature point for 30 minutes to make the temperature of the sample uniform, and the cycle is set to 50 times to test the sheet resistance.

[0085] The results of the experiments conducted on each embodiment and comparative example are shown in Table 1: Table 1 Comparison of test results between each embodiment and the comparative example

[0086] Based on the test data in Table 1 and the performance of each embodiment and comparative example, the specific performance and scenario adaptation analysis is as follows: Example 1 serves as the basic scheme, achieving synergistic optimization of the functional layer and the metal layer: the copper metal layer constructs a low-resistance path with a sheet resistance as low as 18mΩ, meeting the requirements for high current transmission; the gradient structure of the nickel functional layer forms a dense nanocrystalline layer with a tensile strength of 322MPa and excellent impact resistance; the copper-nickel interface achieves a tight metallurgical bond with an adhesion force of 45N / m, and the sheet resistance growth rate after cycling is only 11.1%, significantly improving high-temperature stability. It is suitable for high-energy-density power batteries, balancing fast charging requirements and long cycle life, resulting in optimal overall performance.

[0087] Example 2 replaces the functional layer material with tin and adopts a lightweight design (tin has a lower density than nickel), which can reduce the weight of the current collector and is suitable for weight-sensitive fields such as consumer electronics; however, due to the influence of material properties, the mechanical properties are slightly reduced, the tensile strength is reduced to 295MPa, the sheet resistance is increased to 25mΩ, and the sheet resistance growth rate after cycling reaches 20.0%, which overall meets the basic performance requirements of lightweight scenarios.

[0088] Example 3 uses an aluminum metal layer, verifying the applicability of the present invention to aluminum-based composite current collectors; however, the metallurgical bonding strength of the aluminum-nickel interface is slightly weaker than that of the copper-nickel combination, corresponding to a tensile strength of 307 MPa, sheet resistance of 22 mΩ, and a sheet resistance growth rate of 22.7% after cycling, which can be used as a performance optimization scheme for aluminum-based current collectors.

[0089] Example 4 reduces the thickness of the nickel functional layer to 1 μm (thickness ratio 0.5:1), maintaining the sheet resistance at a low level of 17 mΩ, which is suitable for the mid-to-low-end battery market that is sensitive to cost but has high requirements for conductivity; however, the protective ability of the functional layer is weakened, resulting in a decrease in tensile strength to 281 MPa, and the sheet resistance growth rate after cycling increases to 29.4%, requiring a trade-off between cost and stability.

[0090] Example 5 increases the thickness of the functional layer to 3 μm (thickness ratio 3:1), enhancing the protection of the internal metal layer. The tensile strength is 329 MPa, the adhesion is 47 N / m, and the sheet resistance growth rate after cycling is 15.0%. The performance is balanced, and the sheet resistance of 21 mΩ is still within the acceptable range, making it suitable for high-energy-density batteries or extreme environment applications with high protection requirements.

[0091] In Example 6, the thickness of the functional layer is further increased to 5 μm (thickness ratio 5:1), forming a nanoscale dense protective barrier that effectively blocks element diffusion. The tensile strength reaches 382 MPa, the adhesion force is 50 N / m, the resistance to backflow rate increases by 16.7% after cycling, and the stability is excellent, making it suitable for high-end power batteries or energy storage systems with extremely high performance stability requirements.

[0092] In Example 7, chromium was selected as the functional layer metal material. The difference in interface lattice constant was 30%. Although the resistivity of the functional layer was slightly higher than that in Example 1, the overall performance could still meet the requirements of current collector use, effectively ensuring interface compatibility and avoiding performance degradation caused by too many interface defects.

[0093] In Example 8, the thermal conductivity of the metal layer and the functional layer are reversed, making it impossible to achieve orderly heat dissipation from the base film to the functional layer and then to the metal layer. This causes heat to easily accumulate in the functional layer, reducing the overall thermal stability of the current collector. Furthermore, the material selected to match the reverse thermal conductivity design also results in a slight decrease in the mechanical strength and electrical conductivity of the current collector compared to other examples. The protective-conductive synergy between the functional layer and the metal layer is weakened, leading to mediocre overall performance.

[0094] Comparative Example 1, due to the cancellation of the second-stage heat treatment, lacked a structural stabilization process, resulting in uncontrolled grain growth, loose interfacial bonding, and the inability to form an effective gradient transition structure. Consequently, various properties deteriorated severely: tensile strength plummeted to 247 MPa, sheet resistance increased to 28 mΩ, and adhesion was only 30 N / m. After cycling, the sheet resistance increased by as much as 60.7%, verifying the crucial role of the second-stage heat treatment in structural formation.

[0095] Comparative Example 2 uses a lower heat treatment temperature and a slower heating rate. Insufficient energy input leads to inadequate recrystallization, poor grain refinement, and the inability to achieve good metallurgical bonding between the metal layer and the functional layer. The tensile strength is only 209 MPa, the sheet resistance is as high as 35 mΩ, the adhesion is poor, and the cycle stability is extremely poor, highlighting the importance of controlling the gradient heat treatment parameters.

[0096] Comparative Example 3 is a traditional copper composite current collector. Due to the lack of functional layer design and gradient structure, a large number of microcracks and interface peeling are generated during high-temperature cycling, resulting in a sharp increase in resistance. This is manifested in a tensile strength of 183MPa, a sheet resistance of 40mΩ, and a sheet resistance growth rate of 87.5% after cycling, which cannot meet the application requirements of high-performance batteries.

[0097] Comparative Example 4 uses molybdenum as the functional layer metal material. The difference in the interfacial lattice constant is controlled to reach 35%, which leads to an increase in interfacial defects, loose bonding, a significant increase in the resistivity of the functional layer, and a tendency to delamination. This proves that exceeding the limit of the lattice constant difference will seriously damage the interfacial compatibility and lead to a decrease in the overall performance of the current collector. This further verifies the necessity of limiting the lattice constant difference in this invention.

[0098] Comparative Example 5 adjusted the thickness ratio of the functional layer to the metal layer to 0.25:1. The functional layer was too thin, resulting in a loose structure and insufficient protection. The tensile strength dropped significantly to 215 MPa, the sheet resistance increased to 29 mΩ, the adhesion was weakened, and the sheet resistance increased by as much as 72.3% after cycling. The performance deteriorated severely after high-temperature cycling, proving that an excessively low thickness ratio would cause the functional layer to lose its effective protective function and make it impossible to achieve a balance between conductivity and protection. This verified the scientific validity of the thickness ratio limit.

[0099] Comparative Example 6 adjusts the thickness ratio of the functional layer to the metal layer to 12:1. The excessive thickness of the functional layer leads to uneven grain growth and internal stress concentration, which not only increases the sheet resistance to 38mΩ, but also reduces the adhesion and deteriorates the cycle stability. This proves that an excessively high thickness ratio will cause performance redundancy and drag down the conductivity, further confirming the necessity of limiting the thickness ratio in this invention.

[0100] Comparative Example 7 used tungsten as the functional layer metal material, and the resistivity of the functional layer was adjusted to 1.2 × 10⁻⁶. -5 Ω The excessive resistivity leads to a sharp decline in overall conductivity and excessive Joule heating. At high temperatures, the grains coarsen further, and the sheet resistance increases by as much as 81.5% after cycling, which cannot meet the basic conductivity requirements of the current collector. This proves that exceeding the resistivity parameter limit will directly cause the current collector to lose its application value, highlighting the core role of the resistivity gradient limitation of this invention.

[0101] In Comparative Example 8, the resistivity of the metal layer and the functional layer are opposite. The experimental results show that the tensile strength is 231 MPa, indicating poor material compatibility and moderate mechanical strength; the adhesion is 35 N / m, indicating weak interfacial bonding; the sheet resistance increases by 43% after cycling, indicating insufficient interfacial compatibility and significant performance degradation during cycling, failing to achieve the synergistic effect of protection and conductivity.

[0102] In summary, the various embodiments of this invention achieve a differentiated balance between conductivity, mechanical strength, and cycle stability through material selection, thickness ratio adjustment, and gradient heat treatment process optimization. Among them, Embodiment 1 exhibits the best overall performance, while the other solutions provide customized solutions for specific needs such as lightweighting, extreme environment protection, cost control, and high stability, offering a rich and feasible technical path for the industrial application of composite current collectors.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A composite current collector with a metallic material functional layer, characterized in that: It includes a base film layer, a metal layer on at least one surface of the base film layer, and a functional layer disposed on the surface of the metal layer away from the base film layer; the functional layer comprises a metallic material; The thickness ratio of the functional layer to the metal layer is 0.5~10:1, and the thickness of the functional layer ranges from 0.5 to 10 μm; the resistivity R1 of the functional layer and the resistivity R2 of the metal layer are related by a ratio of 10:

1. 5 Ω m>R1>R2.

2. The composite current collector with a metallic material functional layer according to claim 1, characterized in that: The relationship between the particle size of the functional layer and the particle size of the metal layer is that the average particle size of the functional layer is less than or equal to 0.17 times the average particle size of the metal layer.

3. The composite current collector with a metallic material functional layer according to claim 1, characterized in that: The lattice constant difference between the functional layer and the metal layer at their interface is ≤30%.

4. The composite current collector with a metallic material functional layer according to claim 1, characterized in that: The thermal conductivity of the base film layer is less than that of the functional layer, which in turn is less than that of the metal layer.

5. The composite current collector with a metallic material functional layer according to claim 4, characterized in that: The base film layer includes at least one of carbon material and organic material, the thermal conductivity of the base film layer is 0.1~50 W / mK, the thermal conductivity of the functional layer is 50~100 W / mK, and the thermal conductivity of the metal layer is >200 W / mK.

6. The method for preparing the composite current collector with a metallic material functional layer according to any one of claims 1 to 5, characterized in that: Includes the following steps: S1: Prepare a base transition layer on a polymer film substrate; S2: Prepare a metal layer on the surface of the metal underlayer transition layer; S3: Prepare a functional layer containing metallic material on the surface of the metal layer; S4: Perform heat treatment at 500~800℃ to control the growth rate of functional layer grains within the range of 1~50μm / h, then cool to obtain the final composite current collector.

7. The method for preparing a composite current collector with a metallic material functional layer according to claim 6, characterized in that: The heat treatment in step S4 specifically includes the following gradient stages: First gradient stage: The initial composite current collector is heated to 650-800℃ at a rate of 100-120℃ / min and held at that temperature for 2-5 minutes; the metal layer grain growth rate is 25-50μm / h, and the grain size is 2-3μm; in the functional layer, the inner metal material closest to the metal layer receives the energy transferred by the metal layer and recrystallizes rapidly, with a grain growth rate of 40-50μm / h and a grain size of 0.8-1.5μm; Second gradient stage: Then, the temperature is reduced to 450-600℃ at a rate of 15-25℃ / min, and held at this temperature for 4-6 minutes; the growth rate of metal layer grains is reduced to 10-20μm / h, and the grain size continues to grow slowly to a final size of 3-5μm; in the functional layer, the inner metal material grains near the metal layer gradually stop growing, and the metal material grains in the middle part mainly grow in this stage, with a growth rate of 20-30μm / h, and the resulting grain size is 0.2-1μm.

8. The method for preparing a composite current collector with a metallic material functional layer according to claim 6, characterized in that: After the heat treatment in step S4 is stopped, the temperature is reduced to below 300℃ at a cooling rate of 10~15℃ / min; the growth of metal layer grains basically stops; in the functional layer, the metal material grains in the middle part gradually stop growing, and the outermost metal material grains mainly grow in this stage, with a growth rate of 1~10μm / h, and the final grain size is ≤100nm.

9. An electrode sheet, characterized in that: A composite current collector having a functional layer of metallic material prepared by the method described in any one of claims 1 to 5 or any one of claims 6 to 8.

10. A battery, characterized in that: It includes the electrode sheet as described in claim 9.

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