Current collector, battery pole piece and electrochemical device

Abstract

The invention provides a current collector, a battery pole piece and an electrochemical device. The current collector comprises a phase change regulation and control layer, a functional interlayer arranged on the surface of the phase change regulation and control layer and a metal conductive layer arranged on the surface of the functional interlayer, wherein the phase change regulation and control layer comprises a composite phase change material and a heat conduction network distributed in the composite phase change material. The thermal safety of the battery is remarkably improved through a synergistic mechanism of heat absorption and temperature equalization of the phase change regulation and control layer and intelligent adjustment of current protection of the functional interlayer, namely the phase change material absorbs latent heat at high temperature, the embedded heat conduction network quickly disperses heat, the functional interlayer automatically suppresses local overcurrent through a PTC (Positive Temperature Coefficient) effect, and finally, a circuit is cut off before thermal runaway, so that the thermal safety of the battery is improved. The current collector has active temperature control and self-protection functions, and is especially suitable for a high-energy density battery system. The invention also provides a battery pole piece and an electrochemical device.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and in particular relates to a current collector, a battery pole piece and an electrochemical device. Background Art

[0002] With the widespread application of lithium-ion batteries in electric vehicles, energy storage systems, consumer electronics and other fields, their energy density and power density continue to increase, but the resulting thermal safety issues are also becoming increasingly prominent. During the operation of lithium-ion batteries, especially during high-rate charge and discharge, the internal electrochemical reactions are accompanied by significant Joule heat and polarization heat accumulation. Studies have shown that when the battery temperature reaches 60-80°C, the solid electrolyte interface (SEI) film on the negative electrode surface begins to decompose, resulting in continuous consumption of the electrolyte and side reactions with the exposed active materials. Further heat release may cause thermal runaway. This vicious cycle not only accelerates the degradation of battery performance, but may also cause serious safety accidents such as combustion or explosion. Therefore, how to achieve efficient heat regulation in the early temperature rise stage of the battery has become one of the key challenges to ensure the safety and cycle life of lithium-ion batteries.

[0003] As the core component of lithium-ion batteries that carries active materials and conducts current, the design of the current collector directly affects the thermal-electrical coupling behavior of the battery. Traditional current collectors (such as copper foil and aluminum foil) mainly undertake the current collection function, but face significant limitations in high-energy-density batteries: on the one hand, the thermal conductivity of metal foil is limited, and it is difficult to quickly remove the heat accumulated in local hot spots; on the other hand, a single material cannot dynamically adjust the current distribution in response to temperature changes, resulting in current overload in high-temperature areas and increasing the risk of thermal runaway. In recent years, researchers have tried to improve the thermal and electrical conductivity of current collectors through surface coatings (such as graphene, carbon nanotubes) or composite structures (such as porous metal matrices), but these passive improvements are still difficult to meet the battery's needs for thermal-electrical coordinated management under extreme operating conditions.

[0004] To address the above problems, there is an urgent need to develop a new type of multifunctional composite current collector that can integrate thermal management, current self-regulation and active safety protection. Summary of the Invention

[0005] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, the present invention provides a current collector that significantly improves the thermal safety of the battery through a phase change control layer that absorbs heat to equalize temperature and a functional interlayer that intelligently regulates current. The phase change material absorbs latent heat at high temperatures, the embedded heat conduction network quickly disperses heat, and the functional interlayer automatically suppresses local overcurrent through the PTC (Positive Temperature Coefficient) effect, ultimately cutting off the circuit before thermal runaway, so that the current collector has both active temperature control and self-protection functions, and is particularly suitable for high-energy-density battery systems.

[0006] The present invention also provides a method for preparing a current collector.

[0007] The present invention also provides a battery pole piece.

[0008] The present invention also provides an electrochemical device.

[0009] The first aspect of the present invention provides a current collector, comprising a phase change regulation layer, a functional interlayer arranged on the surface of the phase change regulation layer, and a metal conductive layer arranged on the surface of the functional interlayer, wherein the phase change regulation layer comprises a composite phase change material and a thermal conductive network distributed in the composite phase change material.

[0010] One of the technical solutions for the current collector of the present invention has at least the following beneficial effects:

[0011] The phase change control layer absorbs a large amount of latent heat when the battery temperature rises to a critical point (such as 60°C) through the endothermic phase change behavior of the matrix material (such as paraffin, polymer phase change material), thereby buffering the temperature rise rate. After the thermal conductive network is embedded in the matrix, a rapid heat diffusion channel is formed to avoid local accumulation of heat and significantly improve the lateral thermal conductivity of the current collector. The synergistic effect of the matrix material and the thermal conductive network makes the temperature distribution on the electrode surface more uniform under extreme operating conditions such as high temperature or overcharge, delaying the triggering time of SEI film decomposition and electrolyte side reactions. As a result, the current collector of the present invention can suppress local overheating and delay thermal runaway.

[0012] The resistivity of the functional interlayer increases significantly with increasing temperature. When a local area overheats, the current path in that area automatically contracts, forcing the current to flow to the cooler area. This "current-temperature" negative feedback mechanism prevents current overload in hot spots, reduces the risk of lithium dendrite growth, and extends the battery's cycle life (experiments have shown that it can reduce capacity decay by more than 10%). It can also dynamically optimize charge distribution and achieve current self-regulation.

[0013] The current collector of this invention provides active safety protection, including thermally triggered fuse protection. The metal conductive layer and the functional interlayer form a series circuit. When the temperature exceeds a safety threshold, the functional interlayer's resistance increases dramatically or completely shuts off the current path. Compared to traditional current collectors that rely solely on external battery management system protection, this built-in "fuse" provides a faster response and prevents the spread of thermal runaway.

[0014] The multilayer composite structure of the current collector can be prepared by roll-to-roll process with controllable thickness, which is compatible with existing electrode coating and roll pressing processes. The metal conductive layer ensures low interface resistance (<1Ω / cm 2 ), does not affect the energy density and power output of the battery.

[0015] The current collector of this invention achieves a technological leap from "passive heat dissipation" to "active regulation" through a multi-stage protection mechanism combining phase change heat absorption, thermal network temperature equalization, and dynamic current regulation. This makes it particularly suitable for high-energy-density battery systems, such as those with high-nickel ternary elements and silicon-carbon anodes, and provides an innovative material-level solution to thermal safety issues. The multilayer composite current collector structure integrates thermal management, current self-regulation, and active safety protection features, making it suitable for the coordinated thermal-electrical safety regulation of batteries.

[0016] According to some embodiments of the present invention, the composite phase change material includes a metal organic framework compound loaded with graphite or fatty acid.

[0017] Composite phase change materials can be recorded as MOF@PCM.

[0018] According to some embodiments of the present invention, the metal organic framework compound loaded with graphite or fatty acid includes ZIF-8, MOF-199, Bi-MOF and derivatives thereof.

[0019] The porous structure of MOF provides a high specific surface area, significantly improving the thermal cycling stability and latent heat density of phase change materials.

[0020] According to some embodiments of the present invention, in the phase change regulation layer, the mass fraction of the thermal conductive network is 1-15 wt %.

[0021] According to some embodiments of the present invention, in the phase change regulation layer, the mass fraction of the thermal conductive network is 5-12 wt %.

[0022] According to some embodiments of the present invention, in the phase change regulation layer, the mass fraction of the thermal conductive network is 5-10 wt %.

[0023] According to some embodiments of the present invention, in the phase change regulation layer, the mass fraction of the thermal conductive network is 5-7.5 wt %.

[0024] According to some embodiments of the present invention, the thermally conductive network includes a zinc oxide-carbon nanotube heterojunction thermally conductive filler.

[0025] According to some embodiments of the present invention, the zinc oxide-carbon nanotube heterojunction thermal conductive filler is incorporated into the phase change control layer in an amount of 1 to 20 wt %.

[0026] According to some embodiments of the present invention, the zinc oxide-carbon nanotube heterojunction thermal conductive filler is incorporated into the phase change control layer in an amount of 1 to 15 wt %.

[0027] According to some embodiments of the present invention, the zinc oxide-carbon nanotube heterojunction thermal conductive filler is incorporated into the phase change control layer in an amount of 5 to 15 wt %.

[0028] According to some embodiments of the present invention, the zinc oxide-carbon nanotube heterojunction thermal conductive filler is incorporated into the phase change control layer in an amount of 6 to 12 wt %.

[0029] According to some embodiments of the present invention, the amount of the zinc oxide-carbon nanotube heterojunction thermal conductive filler incorporated into the phase change control layer is any value of 6wt%, 7wt%, 7.5wt%, 8wt%, 9wt%, 10wt%, 11wt%, or 12wt%, such as 7.5wt%, or a range value formed by any two of the above, such as 7wt% to 9wt%.

[0030] According to some embodiments of the present invention, in the zinc oxide-carbon nanotube heterojunction thermal conductive filler, the mass ratio of zinc oxide to carbon nanotubes is 1:(1-3).

[0031] According to some embodiments of the present invention, in the zinc oxide-carbon nanotube heterojunction thermal conductive filler, the mass ratio of zinc oxide to carbon nanotubes is any value among 1:1, 1:2, 1:3, such as 1:2, or a range formed by any two, such as 1:2-1:3.

[0032] When the temperature exceeds the threshold, the zinc oxide semiconductor-metal phase transition triggers the reconstruction of the thermal conduction path, and the thermal conductivity coefficient jumps from the low temperature state to the high temperature state.

[0033] According to some embodiments of the present invention, the preparation method of the zinc oxide-carbon nanotube heterojunction thermal conductive filler can be synthesized by a hydrothermal method, and the method can be:

[0034] 1. Remove impurities from the multi-walled carbon nanotubes by static air ablation, and then wash them with nitric acid reflux to neutrality;

[0035] 2. Disperse neutral multi-walled carbon nanotubes and surfactant in dimethylformamide, add zinc acetate solution, and hydrothermally react at 60-90℃ for 1-3 hours. 2+ Hydrolysis on the surface of carbon nanotubes generates zinc oxide nanoparticles or nanospheres;

[0036] 3. The product was separated by centrifugation, washed alternately with ethanol and deionized water, and dried to obtain the ZnO-CNT heterostructure.

[0037] According to some embodiments of the present invention, the functional interlayer is a positive temperature coefficient ceramic layer, including BaTiO3-(Bi 0.5 Na 0.5 )At least one of TiO3 material and PbTiO3-thermosetting resin composite material.

[0038] BaTiO3-(Bi 0.5 Na 0.5 ) The preparation method of TiO3 material can be:

[0039] Solid-phase reaction method → ​​pre-sintering (1100–1300°C) → ball milling → pressing → sintering (air or nitrogen atmosphere, 1200–1350°C).

[0040] The preparation method of the PbTiO3-thermosetting resin composite material can be:

[0041] Resin is mixed with PbTiO3 powder → hot pressing (150–200°C) → post-curing.

[0042] The functional interlayer is a positive temperature coefficient ceramic layer. When the temperature exceeds the safety threshold, the resistivity rises sharply and the local current is automatically cut off.

[0043] According to some embodiments of the present invention, the thickness D1 of the phase change control layer is in the range of 4-7 microns.

[0044] According to some embodiments of the present invention, the thickness D2 of the metal conductive layer is in the range of 2-5 microns.

[0045] According to some embodiments of the present invention, the thickness D1 of the phase change control layer and the thickness D2 of the metal conductive layer satisfy the relationship 1.5≤D1 / D2≤3.

[0046] According to some embodiments of the present invention, the thickness D1 of the phase change control layer and the thickness D2 of the metal conductive layer satisfy the relationship 1.8≤D1 / D2≤2.8.

[0047] According to some embodiments of the present invention, the thickness D1 of the phase change control layer and the thickness D2 of the metal conductive layer satisfy the relationship 2≤D1 / D2≤2.5.

[0048] According to some embodiments of the present invention, the thickness D1 of the phase change control layer and the thickness D2 of the metal conductive layer satisfy the relationship D1 / D2=2.

[0049] According to some embodiments of the present invention, the thickness D3 of the functional interlayer is 1 micrometer to 5 micrometers.

[0050] According to some embodiments of the present invention, the thickness D3 of the functional interlayer is 1 micrometer to 4 micrometers.

[0051] According to some embodiments of the present invention, the thickness D3 of the functional interlayer is 2 micrometers to 3 micrometers.

[0052] If the functional interlayer is too thin, its function will be weak; if the functional interlayer is too thick, the energy density of the battery will be reduced, and if the ceramic layer is too thick, the current collector will become brittle.

[0053] According to some embodiments of the present invention, the metal conductive layer is copper metal or aluminum metal, and the metal materials on both sides thereof are consistent.

[0054] When the current collector is a positive electrode current collector, aluminum metal is selected, and when the current collector is a negative electrode current collector, copper metal is selected.

[0055] The second aspect of the present invention provides a method for preparing the current collector of the present invention, comprising the following steps: incorporating a thermal conductive network into the composite phase change material to obtain the phase change regulation layer, depositing the functional interlayer on the surface of the phase change regulation layer, and performing vapor deposition on the surface of the functional interlayer to form the metal conductive layer.

[0056] A third aspect of the present invention provides a battery electrode, comprising a foil base layer and an active material layer provided on the surface of the foil base layer, wherein the foil base layer is the current collector of the present invention.

[0057] The battery pole piece realizes the coordinated regulation of "heat, electricity and power" through the integrated design of materials, structure and function, providing an innovative pole piece solution for high-safety and long-life batteries.

[0058] Thermal safety performance has been comprehensively improved. The phase change control layer (PCM + thermal conductivity network) enables the electrode to absorb heat from the electrode-electrolyte interface under thermal abuse conditions (e.g., above 100°C), delaying the decomposition of the SEI film and the reaction or decomposition of the electrolyte with the anode. Experimental data shows that it can delay the triggering of thermal runaway by more than 60% or even prevent thermal runaway. The zinc oxide-carbon nanotube heterojunction thermal conductivity network ensures that the electrode's lateral thermal conductivity at high temperatures approaches that of traditional metal foil, effectively eliminating "hot spots" caused by uneven coating or localized lithium deposition.

[0059] Dynamic current regulation can suppress dendrites. The PTC properties of the functional interlayer (such as BaTiO3-based ceramics) enable the electrode to automatically reduce the current density in the area when it is locally overheated (the resistivity can increase by 3 to 5 orders of magnitude), forcing the current to flow to the low-temperature area:

[0060] For the negative electrode: reduce the uneven deposition of lithium metal, and reduce the probability of dendrites piercing the separator by 60% after 1000 cycles;

[0061] For positive electrode sheets: suppress the concentrated current at the cracks of high-nickel material particles and alleviate the dissolution of transition metals.

[0062] Compatible with structural stability and process. After optimizing the thickness ratio of the metal conductive layer (Cu / Al) and the phase change control layer (D1 / D2 = 1.5-3), the electrode's resistance to bending and fracture during rolling is improved while maintaining ≥98% coating adhesion. The thickness design of the functional interlayer (0.5-3 microns) makes the interface resistance between the metal layer and the active material layer <1Ω / cm 2, the energy density loss of the whole battery is <1.5% (compared with traditional composite current collector).

[0063] Active fuse protection is provided. When the temperature exceeds a safety threshold (e.g., 130°C), the impedance of the functional interlayer increases dramatically, shutting off the current, and the phase change layer undergoes a phase change, shutting off the local current within 1ms (100 times faster than a BMS response), preventing heat spread. Tests have shown that batteries using this electrode did not catch fire or explode during needle penetration tests.

[0064] A fourth aspect of the present invention provides an electrochemical device comprising the current collector or battery electrode of the present invention.

[0065] Electrochemical devices (such as lithium-ion batteries) employing the current collector or battery electrode of the present invention significantly enhance the device's thermal safety and cycling stability through a multi-stage synergistic mechanism: phase change heat absorption buffers temperature rise, a heat conduction network homogenizes the temperature field, a functional layer dynamically regulates current, and a thermally triggered fuse rapidly responds. Experiments have shown that the device can increase the thermal runaway trigger temperature by 10-20%, extend cycle life by 10%-15%, reduce local temperature differences by over 60%, and achieve electrode-level short-circuit protection within 1ms. This device is particularly suitable for high-energy density systems such as high-nickel ternary and silicon-carbon batteries. It addresses the core pain points of traditional batteries, namely the difficulty in suppressing thermal runaway and uncontrollable current distribution, achieving a technological breakthrough from passive protection to active regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a schematic structural diagram of the current collector of the present invention. DETAILED DESCRIPTION

[0067] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0068] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0069] Unless otherwise specified, "room temperature" in the present invention means 25°C±5°C.

[0070] Unless otherwise specified, “about” in the present invention means that the allowable error is within ±2%.

[0071] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0072] Bi-MOF derivatives were purchased from Zhengzhou University.

[0073] Multi-walled carbon nanotubes were purchased from Shanghai MacLean Biotechnology.

[0074] The conventional current collector in Comparative Example 4 was purchased from Zhongyi Technology.

[0075] Example 1

[0076] A current collector having a structure such as Figure 1 As shown. It includes a phase change control layer 1, a functional interlayer 2 provided on the surface of the phase change control layer 1, and a metal conductive layer 3 provided on the surface of the functional interlayer 2. The phase change control layer 1 includes a composite phase change material and a heat conduction network distributed in the composite phase change material. The specific preparation method is:

[0077] 1. A metal-organic framework Bi-MOF derivative was immersed in molten paraffin (80°C) and vacuum-adsorbed for 24 hours to prepare a composite phase-change material with a loading rate ≥ 85%. A zinc oxide-carbon nanotube (ZnO-CNT) heterojunction (CNT:ZnO=2:1) ​​was incorporated into the composite phase-change material and dispersed using ultrasound.

[0078] It should be noted that the incorporation mass fraction of the zinc oxide-carbon nanotube (ZnO-CNT) heterojunction (CNT:ZnO=2:1) ​​is 7.5 wt %. The incorporation method is: the pre-synthesized ZnO-CNT heterojunction is directly dispersed in the molten phase change material (such as paraffin, fatty acid), and uniform mixing is achieved by mechanical stirring.

[0079] Wherein, the preparation method of ZnO-CNT heterojunction is:

[0080] (1) The multi-walled carbon nanotubes were subjected to static air ablation (450°C, 1.5 hours) to remove impurities, and then refluxed with nitric acid and washed until neutral;

[0081] (2) Neutral multi-walled carbon nanotubes and surfactant (sodium dodecylbenzenesulfonate or hexadecyltrimethylammonium bromide, concentration 0.5 wt%) were dispersed in dimethylformamide, and zinc acetate solution was added and hydrothermally reacted at 75 ° C for 2 hours. 2+ Hydrolysis on the surface of carbon nanotubes generates zinc oxide nanoparticles or nanospheres;

[0082] (3) The product was separated by centrifugation, washed alternately with ethanol and deionized water, and dried to obtain a ZnO-CNT heterostructure.

[0083] 2. The above composite material is made into a phase change control layer with a thickness of 5 microns, and a positive temperature coefficient ceramic layer with a thickness of 1 micron is formed on the surface by chemical vapor deposition;

[0084] The preparation method of the phase change control layer is as follows:

[0085] (1) Encapsulating the composite phase change material in polyurethane or silica microcapsules;

[0086] (2) The microcapsules were mixed with polyethylene terephthalate (PET) and prepared into a 5 μm thick matrix using a melt extrusion-biaxial stretching method;

[0087] (3) Relax at 180°C for 5 seconds to eliminate residual stress and improve dimensional stability;

[0088] (4) The substrate is corona treated to enhance the adhesion of subsequent processes, and a 5-micron phase change control layer can be produced.

[0089] The preparation method of 1 micron positive temperature coefficient ceramic layer is as follows:

[0090] Solid-phase sintering method: (1) Ingredients → Ball milling → Pre-sintering (1200°C) → Granulation and compacting → Sintering (air or nitrogen atmosphere, 1250°C) → Annealing (800°C). (2) Ingredients: The main component is barium titanate, with SrTiO3 (10-20 at%) added to control the Curie temperature, and Nb2O5 (0.4 at%) doped to increase the PTC kick ratio.

[0091] 3. Form a 2-micron-thick metal conductive layer on the surface of the ceramic layer by evaporation. When the current collector is a positive electrode current collector, aluminum metal is used; when the current collector is a negative electrode current collector, copper metal is used;

[0092] 4. The positive and negative electrode slurries are uniformly coated on one side of the composite current collector of corresponding polarity, and dried to obtain a pole piece coated with an active material layer on one side; then, the above steps are repeated on the other side of the composite current collector to obtain a positive and negative pole piece coated with active material on both sides;

[0093] 5. The negative electrode sheet, separator, and positive electrode sheet prepared above are stacked and wound in sequence to form a wound electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, dried, and then injected with electrolyte. The lithium-ion battery is obtained through vacuum packaging, static standing, formation, degassing, and trimming.

[0094] Examples 2 to 5

[0095] Except for adjusting the relevant parameters according to Table 1, the remaining parameters are the same as those in Example 1.

[0096] Comparative Examples 1 to 3

[0097] Except for adjusting the relevant parameters according to Table 1, the remaining parameters are the same as those in Example 1.

[0098] Comparative Example 4

[0099] Except for using a conventional current collector, other parameters are the same as those in Example 1.

[0100] Comparative Example 5

[0101] No paraffin was loaded, the thickness of the phase change control layer was 6 μm, and the other parameters were the same as those in Example 1.

[0102] Comparative Example 6

[0103] No zinc oxide-carbon nanotube heterojunction thermal conductive filler was added, and the remaining parameters were the same as those in Example 1.

[0104] Comparative Example 7

[0105] The thickness of the phase change control layer is 6 μm, and the other parameters are the same as those in Example 1.

[0106] Table 1

[0107]

[0108] The test results are shown in Table 2.

[0109] It should be noted that the thermal runaway test uses a hot box test to verify the safety performance of the battery. This test attaches a thermocouple to the surface of the battery and places the battery in a hot box. The battery is heated from a starting temperature (room temperature) to a higher temperature at a heating rate of 5±1℃ / min. The hot box temperature is required to be 150℃, and then it is kept constant at this temperature. The change in battery temperature over time is recorded. The time from when the battery is kept at a constant temperature of 150℃ in the hot box to thermal runaway (the exothermic reaction inside the battery is out of control, causing smoke and combustion) is determined.

[0110] Table 2

[0111] 4.8V overcharge thermal runaway time 90℃ interface impedance increase Example 1 22min 275％ Example 2 27min 300％ Example 3 24min 190％ Example 4 22min 290％ Example 5 15min 230％ Comparative Example 1 7min 120％ Comparative Example 2 12min 50％ Comparative Example 3 15min 50％ Comparative Example 4 3min 30％ Comparative Example 5 7min 190％ Comparative Example 6 16min 200％ Comparative Example 7 14min 40％

[0112] As shown in Table 2, Example 1 (MOF@PCM) experienced thermal runaway for 22 minutes, significantly exceeding the 7 minutes of Comparative Example 1 (paraffin). This demonstrates that MOF-based composite phase-change materials, through their high surface area and stable latent heat absorption, are more effective in delaying thermal runaway. The interfacial impedance increase (275%) in Example 1 (MOF@PCM) was significantly higher than the 120% increase in Comparative Example 1 (paraffin), likely due to changes in electrolyte wettability caused by the porous structure of MOF. Further optimization of interfacial compatibility is possible in the future.

[0113] The thermal runaway time in Example 1 (D1 / D2 = 2.5) was 22 minutes, an 83% improvement over the 12 minutes in Comparative Example 2 (D1 / D2 = 1). This demonstrates that a phase-change layer to metal layer thickness ratio of 1.5 to 3 (the preferred range of the present invention) can balance thermal buffering and electrical conductivity requirements. Regarding interface impedance, the 50% increase in Comparative Example 2 is likely due to the excessively thick metal layer, which reduces overall resistance but sacrifices thermal safety.

[0114] Compared with Example 2 and Comparative Example 3, when Comparative Example 3 has no functional interlayer, the thermal runaway time is only 15 minutes (27 minutes in Example 2), and the interface impedance increases by 50%, indicating that the PTC ceramic layer is crucial for dynamic current regulation and local overheating suppression.

[0115] Example 5 increases the heterojunction content, reduces the increase in interface impedance compared to Example 1, and weakens the thermal regulation function.

[0116] Compared with Example 2 and Comparative Example 5, Comparative Example 5 does not load paraffin, and paraffin is the main component of phase change regulation, which proves that the phase change regulation layer is basically no different from the conventional current collector when no paraffin is loaded.

[0117] Compared with Example 1 and Comparative Example 6, the thermal runaway time is shortened after the heterojunction filler is not added in Comparative Example 6, which indicates that the lack of heterojunction cannot conduct heat well and further heat concentration occurs, leading to thermal runaway.

[0118] Compared with Example 7, Example 2 uses ordinary ceramics in Example 7, and the interface impedance is greatly reduced at high temperature, which shortens the thermal runaway time to a certain extent, illustrating the necessity of PTC ceramics.

[0119] The thermal runaway time of comparative example 4 is only 3 minutes, and the interface impedance increases by 30%, which verifies that the traditional current collector cannot provide active protection under extreme working conditions, highlighting the necessity of the multi-layer structure of the present invention.

[0120] The multilayer current collector of the present invention achieves an optimal balance between thermal safety and electrical performance by synergistically optimizing material selection (MOF@PCM+ZnO-CNT), thickness ratio (D1 / D2≈2) and functional interlayer.

[0121] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the relevant technical field without departing from the spirit of the present invention.

Claims

1. A current collector, characterized in that: It includes a phase change regulation layer, a functional interlayer arranged on the surface of the phase change regulation layer, and a metal conductive layer arranged on the surface of the functional interlayer. The phase change regulation layer includes a composite phase change material and a heat conduction network distributed in the composite phase change material.

2. The current collector according to claim 1, characterized in that The composite phase change material includes a metal organic framework compound loaded with paraffin or fatty acid.

3. The current collector according to claim 1, characterized in that The heat-conducting network includes a zinc oxide-carbon nanotube heterojunction heat-conducting filler; preferably, the zinc oxide-carbon nanotube heterojunction heat-conducting filler is added in an amount of 1 to 20 wt % in the phase change control layer.

4. The current collector according to claim 3, characterized in that In the zinc oxide-carbon nanotube heterojunction thermal conductive filler, the mass ratio of zinc oxide to carbon nanotube is 1:(1.5-3).

5. The current collector according to claim 1, characterized in that The functional interlayer is a positive temperature coefficient ceramic layer, including BaTiO3-(Bi 0.5 Na 0.5 )At least one of TiO3 material and PbTiO3-thermosetting resin composite material.

6. The current collector according to claim 1, characterized in that The thickness D1 of the phase change control layer and the thickness D2 of the metal conductive layer satisfy the relationship 1.5≤D1 / D2≤3.

7. The current collector according to claim 1, characterized in that The thickness D3 of the functional interlayer is 0.5 micrometers to 5 micrometers.

8. A method for preparing the current collector according to any one of claims 1 to 7, characterized in that: The following steps are involved: A heat conduction network is added to the composite phase change material to obtain the phase change control layer, the functional interlayer is deposited on the surface of the phase change control layer, and the surface of the functional interlayer is evaporated to form the metal conductive layer.

9. A battery pole piece, characterized in that: It comprises a foil base layer and an active material layer arranged on the surface of the foil base layer, and the foil base layer is the current collector according to any one of claims 1 to 8.

10. An electrochemical device, characterized in that The present invention comprises the current collector according to any one of claims 1 to 8 or the battery pole piece according to claim 9.

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