High performance composite current collector and preparation method and application thereof

Abstract

The application provides a high-performance composite current collector, comprising a polymer support layer, an organic metal thin film interface layer, a first conductive layer, a stress compensation layer and a second conductive layer; a preparation method comprises the following steps: performing plasma treatment on a polymer base material; coating an organic metal framework material precursor solution on the front surface of the polymer base material after the plasma treatment to form an organic metal thin film interface layer; depositing a copper seed layer on the surface of the organic metal thin film interface layer; depositing a chromium metal layer on the back surface of the polymer base material, then introducing nitrogen, depositing a chromium nitride layer on the surface of the chromium metal layer, and the chromium metal layer and the chromium nitride layer jointly form a stress compensation layer; depositing a copper seed layer on the surface of the chromium nitride layer; and performing thickening treatment on the two copper seed layers. The application realizes physical and chemical double combination through the MOF interface layer, improves the interface strength, balances the stress through the back compensation layer, reduces the curling, suppresses lithium dendrites through the uniform copper layer, and improves the battery safety and service life.

Description

Technical Field

[0001] This invention belongs to the field of battery manufacturing technology, specifically relating to a high-performance composite current collector, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage, the demand for lithium batteries continues to rise. Traditional metal foil current collectors suffer from low energy density, poor safety, and high manufacturing costs, hindering the further development of lithium batteries. Therefore, current collectors are evolving towards thinner, lighter, safer, and lower-cost designs. Composite current collectors, with their metal-polymer-metal sandwich structure, offer advantages such as improved safety performance, increased energy density, and reduced raw material costs, making them the most promising new type of current collector material for substitution.

[0003] However, existing composite copper current collectors still face the following technical challenges in practical applications. First, the copper layer in composite copper current collectors is typically thin and often exhibits a discontinuous or ultrafine-grained structure formed by magnetron sputtering or electroplating, resulting in numerous defects such as grain boundaries and pinholes. This leads to a higher bulk resistivity than pure copper foil. Simultaneously, the interface between the copper layer and the polymer substrate exhibits contact resistance due to the low surface energy of the substrate and uneven adhesion of the copper layer, increasing the current collector's internal resistance. High internal resistance under high-rate charging conditions leads to a significant increase in ohmic heat and localized temperature rise, exacerbating the risk of battery thermal runaway. Second, during fast charging, the rate and magnitude of volume change in the electrode material increase dramatically. Repeated stress is transmitted through the electrode layer to the current collector, subjecting the composite copper current collector to mechanical tensile and compressive stress. Due to the thinness of the copper layer and its limited interfacial bonding with the substrate, the copper layer is prone to wrinkling, cracking, and even peeling failure under cyclic stress. Third, there is a significant difference in the coefficient of thermal expansion between the polymer substrate and the copper plating. During the coating process and thermal cycling in the operating environment, this difference introduces substantial residual stress, affecting the structural stability of the current collector. Fourth, uneven distribution of copper plating thickness leads to uneven current density distribution on the current collector surface, with localized high current density areas preferentially inducing lithium dendrite nucleation and growth. Furthermore, the relatively smooth surface of traditional composite copper current collectors results in weak interfacial interaction with the electrolyte, failing to effectively guide uniform lithium ion deposition and easily leading to lithium dendrite growth, which in turn causes battery capacity decay and the risk of internal short circuits.

[0004] To address the aforementioned issues, there is an urgent need to develop a composite copper current collector structure and its preparation method that can enhance interfacial bonding, reduce residual stress, improve copper layer uniformity, and, in battery applications, help suppress lithium dendrite growth, reduce capacity decay and internal short circuit risk. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a high-performance composite current collector, its preparation method, and its application. It aims to solve technical defects such as insufficient interfacial bonding between the copper layer and the polymer substrate, residual stress caused by the mismatch of thermal expansion coefficients, and the tendency of uneven copper plating to induce lithium dendrite nucleation and growth, leading to thermal runaway.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] (I) This invention provides a high-performance composite current collector, comprising: Polymer support layer; An organometallic thin film interface layer is deposited on the front side of the polymer support layer; A first conductive layer is deposited on the organometallic thin film interface layer; A stress compensation layer is deposited on the back side of the polymer support layer; the stress compensation layer consists of a chromium metal layer deposited on the surface of the polymer support layer and a chromium nitride layer deposited on the surface of the chromium metal layer; A second conductive layer is deposited on the stress compensation layer.

[0008] (II) The present invention also provides a method for preparing the above-mentioned high-performance composite current collector, comprising the following steps: The polymer substrate is subjected to plasma treatment; a precursor solution of an organometallic framework material is taken and coated onto the front side of the plasma-treated polymer substrate to form an organometallic thin film interface layer; a copper seed layer is deposited on the surface of the organometallic thin film interface layer; the back side of the plasma-treated polymer substrate is facing the chromium target, and a chromium metal layer is deposited on the surface of the polymer substrate by high-power pulsed magnetron sputtering technology, followed by the introduction of nitrogen gas to deposit a chromium nitride layer on the surface of the chromium metal layer; the chromium metal layer and the chromium nitride layer together form a stress compensation layer; a copper seed layer is deposited on the surface of the chromium nitride layer; the two copper seed layers are thickened to obtain a first conductive layer and a second conductive layer.

[0009] Furthermore, the polymer substrate is a polypropylene film, a polyethylene terephthalate film, or a polyimide film, preferably a biaxially oriented polypropylene film (BOPP).

[0010] Further, the plasma treatment method is as follows: placing the polymer substrate in a plasma treatment chamber, introducing a working gas, and performing plasma treatment under vacuum; the vacuum degree of the plasma treatment chamber is 0.5~2 Pa, the plasma power is 100~300 W, and the treatment time is 30~120 s; the working gas is an argon / oxygen mixture with a volume ratio of 7:3, or the working gas is an argon / nitrogen mixture with a volume ratio of 6:4.

[0011] Further, the method for preparing the organometallic framework material precursor solution includes the following steps: dissolving ZrCl4 and terephthalic acid in N,N-dimethylformamide, adding acetic acid to obtain a UiO-66 precursor solution; wherein the molar ratio of ZrCl4 to terephthalic acid is 1:1, and the Zr content in the UiO-66 precursor solution is... 4+ The concentration is 0.1~0.3 mol / L.

[0012] Furthermore, the method for preparing the organometallic thin film interface layer is as follows: coating an organometallic framework material precursor solution onto the surface of a polymer substrate; heating the coated polymer substrate to 60~85 ℃ and holding it at that temperature for in-situ crystallization; finally cleaning and vacuum drying to obtain the organometallic thin film interface layer.

[0013] Furthermore, the method for preparing the stress compensation layer is as follows: the back side of the plasma-treated polymer substrate faces the chromium target, the front side is shielded by a polytetrafluoroethylene mask, and a chromium metal layer is deposited on the back side of the polymer substrate using high-power pulsed magnetron sputtering technology with the chromium target as the sputtering source and argon as the working gas; then nitrogen is introduced into the deposition chamber, and a chromium nitride layer with a nitrogen content of 10~25 at% and a chromium nitride layer with a nitrogen content of 45~50 at% are sequentially deposited on the surface of the chromium metal layer; the pulse frequency of the high-power pulsed magnetron sputtering is 10~50 Hz, and the duty cycle is 5~15%.

[0014] Furthermore, the thickness of the stress compensation layer is 50-100 nm, the thickness of the chromium metal layer is 10-30 nm, the thickness of the chromium nitride layer with a nitrogen content of 10-25 at% is 10-30 nm, and the thickness of the outermost chromium nitride layer with a nitrogen content of 45-50 at% is 20-40 nm.

[0015] Furthermore, the specific method for depositing the copper seed layer is as follows: using high-power pulsed magnetron sputtering technology, with a Cu target as the sputtering source, controlling the power to be 200~400 W, the working pressure to be 0.1~0.2 Pa, and the temperature to be no more than 40 ℃, a dense copper seed layer is deposited on the surface of the organometallic thin film interface layer / chromium nitride layer.

[0016] Furthermore, the two copper seed layers are thickened by the following steps: the polymer substrate after the copper seed layers are deposited is fed into a vertical continuous electroplating line, a sulfate copper plating system is used, and brighteners, leveling agents, and stress reducers are added, while the current density is controlled at 1~2 A / dm³. 2 Preferably 1.5 A / dm 2 The electroplating temperature is 20~30 ℃, the electroplating time is 20~40 min, and the final copper layer thickness is controlled at 1~3 μm.

[0017] Furthermore, the sulfate copper plating system comprises CuSO4·5H2O and H2SO4; the concentration of CuSO4·5H2O is 180~220 g / L, and the concentration of H2SO4 is 60~80 g / L; the brightener is sodium polydisulfide dipropane sulfonate with a concentration of 2~5 mL / L; the leveling agent is diallyl dimethyl ammonium chloride-sulfur dioxide copolymer with a concentration of 1~3 mL / L; and the stress reducing agent is 2-mercaptobenzothiazole with a concentration of 3~6 mL / L.

[0018] (iii) The present invention also provides the application of the above-mentioned high-performance composite current collector in the preparation of batteries.

[0019] The beneficial effects of this invention are: This invention creatively proposes the use of metal-organic thin films to achieve nanoscale interface strengthening, combined with an asymmetric stress compensation layer. The three-dimensional porous structure of the metal-organic framework interface layer provides a large mechanical interlocking area, and its organic ligands exhibit good compatibility with the biaxially oriented polypropylene substrate. Chemical bonds can be formed between the metal nodes and the copper layer, thus achieving a dual bonding mechanism of physical anchoring and chemical bonding, significantly improving interfacial adhesion. The chromium / chromium nitride compensation layer on the back provides controllable compressive stress, actively counteracting the tensile stress generated by the copper layer on the front, greatly reducing the curl of the composite current collector. Simultaneously, the metal-organic framework layer itself has a certain stress buffering capacity, working synergistically with the compensation layer to achieve stress balance.

[0020] This invention employs high-power pulsed magnetron sputtering technology to deposit a dense, non-porous copper seed layer. Combined with the uniform nucleation sites provided by the surface of the metal-organic framework, this results in a more uniform thickness distribution of the copper layer obtained through subsequent electroplating. The low-stress, highly uniform copper layer helps reduce local current density differences, thereby effectively suppressing lithium dendrite growth and reducing battery capacity decay and the risk of internal short circuits. Attached image description: Figure 1 This is a schematic diagram of the high-performance composite current collector structure of the present invention; The labels in the attached diagram are: 1. Polymer support layer; 2. Organometallic thin film interface layer; 3. Stress compensation layer; 4. First conductive layer; 5. Second conductive layer. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] 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.

[0023] This invention provides a high-performance composite current collector, comprising a polymer support layer, an organometallic thin film interface layer, a first conductive layer, a stress compensation layer, and a second conductive layer; wherein, the organometallic thin film interface layer is deposited on the front side of the polymer support layer, the first conductive layer is deposited on the organometallic thin film interface layer; the stress compensation layer is deposited on the back side of the polymer support layer, and the stress compensation layer is composed of a chromium metal layer deposited on the surface of the polymer support layer and a chromium nitride layer deposited on the surface of the chromium metal layer; the second conductive layer is deposited on the stress compensation layer.

[0024] In the above scheme, an organometallic thin film interface layer is provided on the front side of the polymer support layer. This interface layer can improve the chemical affinity between the polymer surface and the metal conductive layer, realize the chemical anchoring and gradient transition between the polymer substrate and the copper layer, and form a strong transition connection, thereby improving the bonding strength between the first conductive layer and the polymer substrate. In addition, the organometallic thin film interface layer has a porous high specific surface area structure, which can improve the uniformity of copper layer deposition, while providing uniform deposition sites for lithium ions and inhibiting lithium dendrite growth.

[0025] A stress compensation layer is formed by sequentially depositing a chromium metal layer and a chromium nitride layer on the back of the polymer support layer. The chromium metal layer serves as an intermediate transition layer to enhance adhesion, while the chromium nitride layer forms a gradient match with the polymer substrate and the copper layer, effectively offsetting or buffering residual stress caused by differences in thermal expansion coefficients. This balances the global stress of the composite film at the system level and eliminates warping deformation. The first and second conductive layers are located on both sides of the support layer, jointly undertaking the functions of current collection and transmission. Through the above multi-layer structure design, high adhesion between the conductive layer and the polymer substrate, effective suppression of residual stress, and overall structural stability are achieved, thereby reducing internal resistance, suppressing lithium dendrite growth, and improving the rate performance and safety performance of the battery.

[0026] The preparation method of the above-mentioned high-performance composite current collector includes the following steps: Step S1: The polymer substrate is subjected to plasma treatment to activate its surface and improve the adhesion of subsequent coating and deposition; Step S2: Take the precursor solution of the organometallic framework material and coat it on the front side of the plasma-treated polymer substrate to form an organometallic thin film interface layer; deposit a copper seed layer on the surface of the organometallic thin film interface layer. Step S3: With the back side of the plasma-treated polymer substrate facing the chromium target, a chromium metal layer is deposited on the surface of the polymer substrate using high-power pulsed magnetron sputtering technology. Nitrogen gas is then introduced to deposit a chromium nitride layer on the surface of the chromium metal layer. The chromium metal layer and the chromium nitride layer together form a stress compensation layer. A copper seed layer is then deposited on the surface of the chromium nitride layer. Step S4: Thicken the two copper seed layers to obtain the first conductive layer and the second conductive layer.

[0027] In step S1, the polymer substrate is a polypropylene film, a polyethylene terephthalate film, or a polyimide film, preferably a biaxially oriented polypropylene film (BOPP) with a thickness of 10 μm. Biaxially oriented polypropylene film has high mechanical strength and dimensional stability. At the same time, its surface is easily bonded to the organometallic film interface layer after plasma treatment, which is beneficial to improving the overall structural stability and process adaptability of the composite current collector.

[0028] The plasma treatment method involves placing the polymer substrate in a plasma treatment chamber, introducing a working gas, and performing plasma treatment under vacuum. The vacuum level of the plasma treatment chamber is 0.5–2 Pa, the plasma power is 100–300 W, and the treatment time is 30–120 s. The working gas is either an argon / oxygen mixture with a volume ratio of 7:3 or an argon / nitrogen mixture with a volume ratio of 6:4. This plasma treatment introduces polar functional groups (-COOH, -C=O, -OH, -NH2, -CN, -C=N-, etc.) onto the surface of the polymer substrate, increasing reaction sites and thereby enhancing the adhesion between the substrate and the subsequently deposited organometallic thin film interface layer.

[0029] In step S2, the method for preparing the organometallic framework precursor solution is as follows: ZrCl4 and terephthalic acid are dissolved in N,N-dimethylformamide, and acetic acid is added to obtain the UiO-66 precursor solution; wherein, the molar ratio of ZrCl4 to terephthalic acid is 1:1, the molar ratio of acetic acid to ZrCl4 is 30:1, and the ZrCl4 content in the UiO-66 precursor solution is... 4+ The concentration is 0.1~0.3 mol / L. With this ratio and concentration range, a stable organometallic framework precursor can be obtained, which can then be used to form a uniform organometallic thin film interface layer on the polymer substrate surface.

[0030] UiO-66, as a zirconium-based organometallic framework material, possesses extremely high thermal stability and chemical corrosion resistance, which helps maintain the integrity of the interfacial layer structure when facing battery electrolyte erosion. Simultaneously, its ordered pore structure and abundant active sites enhance the bonding force between the polymer substrate and the inorganic copper layer, thereby reducing interfacial contact resistance and improving the overall cycle stability of the composite current collector.

[0031] The method for preparing an organometallic thin film interface layer using the organometallic framework material precursor solution is as follows: the organometallic framework material precursor solution is coated onto the surface of a polymer substrate; the coated polymer substrate is heated to 60~85 ℃ and kept at this temperature for in-situ crystallization, allowing the precursor to grow in situ on the substrate surface to form an organometallic framework thin film; finally, it is cleaned to remove unreacted residues and vacuum dried to obtain the organometallic thin film interface layer. This method can form a uniform, dense organometallic framework thin film with good adhesion to the polymer substrate surface. The preferred thickness of the organometallic thin film interface layer is 80 nm, and the grain size is 15 nm, with (111) oriented crystals accounting for more than 80%. The film exhibits a hierarchical porous structure, consisting of micropores (<2 nm) and mesopores (2~50 nm).

[0032] In step S3, the stress compensation layer is prepared as follows: the back side of the plasma-treated polymer substrate faces the chromium target, the front side is shielded by a polytetrafluoroethylene mask, and a chromium metal layer is deposited on the back side of the polymer substrate using high-power pulsed magnetron sputtering technology with the chromium target as the sputtering source and argon as the working gas; then nitrogen is introduced into the deposition chamber, and a chromium nitride layer with a nitrogen content of 10~25 at% and a chromium nitride layer with a nitrogen content of 45~50 at% are sequentially deposited on the surface of the chromium metal layer; the pulse frequency of the high-power pulsed magnetron sputtering is 10~50 Hz, and the duty cycle is 5~15%.

[0033] More specifically, the stress compensation layer has a thickness of 50–100 nm, the chromium metal layer has a thickness of 10–30 nm, the chromium nitride layer with a nitrogen content of 10–25 at% has a thickness of 10–30 nm, and the outermost chromium nitride layer with a nitrogen content of 45–50 at% has a thickness of 20–40 nm. For the pure chromium metal layer, a body-centered cubic nanocrystal structure with a preferred orientation of the (110) crystal plane is formed to ensure strong adhesion to the polymer. For the chromium nitride layer, a face-centered cubic structure with a preferred orientation of the (200) crystal plane is formed. This layer is used to achieve a smooth lattice transition from Cr to CrN and to alleviate internal stress. The grain size of both the pure chromium metal layer and the chromium nitride layer is nanocrystalline, with an average grain size of <20 nm, preferably 10 nm. This overall structure makes it easier to introduce high-intensity compressive stress through the HiPIMS process.

[0034] The deposited chromium metal layer serves as an intermediate transition layer, exhibiting good adhesion to both the polymer substrate and the chromium nitride layer, and mitigating interfacial stress caused by differences in thermal expansion coefficients. Depositing two chromium nitride layers with different nitrogen contents aims to create a compositional gradient structure. The chromium nitride layer with a nitrogen content of 10–25 at% exhibits good toughness and mechanical properties similar to the chromium metal layer, acting as a stress buffer transition; the chromium nitride layer with a nitrogen content of 45–50 at% possesses higher hardness and elastic modulus, providing effective structural support and stress compensation. This gradient design balances the global stress of the composite film at the system level, eliminating warpage. The selection of pulse frequency and duty cycle (frequency 10–50 Hz, duty cycle 5–15%) is to control the energy and arrival rate of the deposited particles, obtaining a dense, uniform coating structure with controllable internal stress.

[0035] In steps S2 and S3, the specific method for depositing the copper seed layer is as follows: High-power pulsed magnetron sputtering (HiPIMS) or direct current magnetron sputtering (DCMS) is used, with a Cu target as the sputtering source. The power is controlled at 200-400 W, the working pressure at 0.1-0.2 Pa, and the temperature not exceeding 40 °C. A dense copper seed layer of 30-50 nm thickness is deposited on the surface of the organometallic thin film interface layer / chromium nitride layer. Too low a power will result in a slow deposition rate and insufficient film density; too high a power may cause thermal damage to the polymer substrate and organometallic framework layer due to high-energy particle bombardment, leading to increased substrate temperature. The temperature is kept below 40 °C to prevent deformation or performance degradation of the polymer substrate and organometallic framework layer during deposition, ensuring good crystal orientation and structural integrity of the seed layer under low-temperature conditions. The preferred crystal orientation is... <220> With a grain size of 15nm, the copper layer of this orientation has good conductivity and anti-electromigration ability, while the fine grains help to obtain a dense structure, reduce the seed layer resistance, and thus provide a low sheet resistance conductive substrate for subsequent electroplating thickening.

[0036] Furthermore, the two copper seed layers are thickened by the following steps: the polymer substrate after the copper seed layers are deposited is fed into a vertical continuous electroplating line, a sulfate copper plating system is used, and brighteners, leveling agents, and stress reducers are added, while the current density is controlled at 1~2 A / dm³. 2 Preferably 1.5 A / dm 2The electroplating temperature is 20-30 ℃, the electroplating time is 20-40 min, and the final copper layer thickness is controlled at 1-3 μm. The sulfate copper plating system contains CuSO4·5H2O and H2SO4; the concentration of CuSO4·5H2O is 180-220 g / L, and the concentration of H2SO4 is 60-80 g / L; the brightener is sodium polydisulfide dipropane sulfonate, with a concentration of 2-5 mL / L; the leveling agent is diallyl dimethyl ammonium chloride-sulfur dioxide copolymer (PAS-A-5), with a concentration of 1-3 mL / L; and the stress reducing agent is 2-mercaptobenzothiazole, with a concentration of 3-6 mL / L.

[0037] Sulfate copper plating systems are characterized by simple and stable composition and high current efficiency, making them suitable for continuous production. The synergistic effect of brighteners, leveling agents, and stress reducers can refine grains, improve coating smoothness, and reduce internal stress, preventing warping or peeling of thick copper layers due to excessive stress. The current density is controlled at 1~2 A / dm³. 2 The lower range is designed to ensure uniform deposition of copper ions on the surface of the seed layer, avoiding loose coating or dendrite growth due to excessive current; the electroplating temperature is near room temperature, which is beneficial to maintain the activity of additives and the stability of the plating solution, while avoiding thermal deformation of the polymer substrate and maintaining good adhesion to the substrate.

[0038] Example 1 This embodiment provides a high-performance composite current collector, the preparation method of which is as follows: S1: Substrate pretreatment and activation: A 10 μm thick polymer substrate (BOPP) was placed in a plasma treatment chamber, and an argon / oxygen mixture with a volume ratio of 7:3 was introduced. Plasma treatment was carried out under vacuum, with the vacuum level controlled at 1 Pa, the plasma power at 200 W, and the treatment time at 80 s, to complete the double-sided activation of the BOPP.

[0039] S2. Preparation of the metal-organic film (MOF) interface layer: ZrCl4 and terephthalic acid were dissolved in N,N-dimethylformamide, and acetic acid was added to obtain a UiO-66 precursor solution; wherein the molar ratio of ZrCl4 to terephthalic acid was 1:1, and the molar ratio of acetic acid to ZrCl4 was 30:1, and the Zr content in the UiO-66 precursor solution was... 4+ The concentration is 0.2 mol / L.

[0040] Using a slot extrusion coating machine, the UiO-66 precursor solution was coated onto the front side of the plasma-treated polymer substrate with a wet film thickness of 50 nm. The coated polymer substrate was then rapidly transferred to a heating plate at 85 °C and held at that temperature for 5 min to perform in-situ crystallization, allowing the precursor to grow in situ on the substrate surface to form an organometallic framework film. Finally, unreacted residues were removed by ultrasonic cleaning, and the substrate was vacuum dried at 80 °C for 15 min to obtain an organometallic thin film interface layer with a thickness of 80 nm and a porosity of 40%.

[0041] S3. Preparation of the front copper seed layer: High-power pulsed magnetron sputtering (HiPIMS) was used with a Cu target as the sputtering source. The power was controlled at 300 W, the working pressure at 0.2 Pa, and the temperature at 35 °C. A dense copper seed layer with a thickness of 50 nm was deposited on the surface of the metal-organic thin film interface layer. The copper seed layer and the MOF layer were chemically bonded through Zr-O-Cu chemical bonds.

[0042] S4. Preparation of the stress compensation layer: The back side of the plasma-treated polymer substrate was placed facing the chromium target, and the front side was protected by a polytetrafluoroethylene (PTFE) mask. High-power pulsed magnetron sputtering was used, with the chromium target as the sputtering source, argon as the working gas, and the gas flow rate controlled at 40 sccm. The sputtering power of the chromium target was 100 W, the working gas pressure was controlled at 0.5 Pa, the substrate temperature was 50℃, and the pulse power was 600 W to deposit a 20 nm chromium metal layer on the back side of the polymer substrate. Subsequently, nitrogen gas was introduced into the deposition chamber, and a 20 nm chromium nitride layer with a nitrogen content of 20 at% and a 30 nm chromium nitride layer with a nitrogen content of 45 at% were sequentially deposited on the surface of the chromium metal layer. The pulse frequency of the high-power pulsed magnetron sputtering was 40 Hz, and the duty cycle was 10%. Compressive stress was introduced into this thin layer, which canceled out the tensile stress of the copper seed layer on the front side.

[0043] S5. Preparation of the copper seed layer on the back side: High-power pulsed magnetron sputtering (HiPIMS) was used with a Cu target as the sputtering source, and the power was controlled at 300 W, the working pressure at 0.2 Pa, and the temperature at 35 °C to deposit a 50 nm thick dense copper seed layer on the surface of a chromium nitride layer with a nitrogen content of 45 at%.

[0044] S6. The two copper seed layers are thickened to form the first conductive layer and the second conductive layer: The polymer substrate after depositing the copper seed layer is fed into a vertical continuous electroplating line. A sulfate copper plating system (CuSO4·5H2O 200g / L, H2SO4 70g / L) is used, with brightener (sodium polydisulfide dipropane sulfonate, 3 mL / L), leveling agent (diallyl dimethyl ammonium chloride-sulfur dioxide copolymer PAS-A-5, 2 mL / L) and stress reducer (2-mercaptobenzothiazole, 5 mL / L) added. The current density is controlled at 1.5 A / dm³. 2 The electroplating temperature was 25 ℃ and the electroplating time was 30 min. The final copper layer thickness was controlled at 1.2 μm, thus forming a composite copper current collector.

[0045] Example 2 The difference between Example 2 and Example 1 is as follows: In step S2, Zr in the UiO-66 precursor solution 4+ The concentration was 0.1 mol / L; the polymer substrate coated with UiO-66 precursor solution was crystallized on a heating plate at 80 ℃.

[0046] Example 3 The difference between Example 3 and Example 1 is as follows: In step S2, Zr in the UiO-66 precursor solution 4+ The concentration was 0.3 mol / L; the polymer substrate coated with UiO-66 precursor solution was crystallized on a heating plate at 60 ℃.

[0047] Example 4 The difference between Example 4 and Example 1 is as follows: In step S4, the nitrogen contents of the two chromium nitride layers are 10 at% and 45 at% respectively. The thickness of the chromium metal layer is 30 nm, the thickness of the chromium nitride layer with a nitrogen content of 10 at% is 30 nm, and the thickness of the outermost chromium nitride layer with a nitrogen content of 45 at% is 20 nm. The pulse frequency of high-power pulsed magnetron sputtering is 10 Hz, and the duty cycle is 15%.

[0048] Example 5 The difference between Example 5 and Example 1 is as follows: In step S4, the nitrogen contents of the two chromium nitride layers are 25 at% and 50 at% respectively. The thickness of the chromium metal layer is 10 nm, the thickness of the chromium nitride layer with a nitrogen content of 25 at% is 10 nm, and the thickness of the outermost chromium nitride layer with a nitrogen content of 50 at% is 40 nm. The pulse frequency of high-power pulsed magnetron sputtering is 50 Hz, and the duty cycle is 5%.

[0049] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is as follows: Comparative Example 1 does not include step S1, which involves substrate pretreatment and activation.

[0050] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is as follows: In Comparative Example 2, step S2 is omitted. In step S3, a 50 nm thick dense copper seed layer is directly deposited on the front side of the polymer substrate using high-power pulsed magnetron sputtering technology.

[0051] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is as follows: In Comparative Example 3, step S4 is omitted. In step S5, a 50 nm thick dense copper seed layer is directly deposited on the back side of the polymer substrate using high-power pulsed magnetron sputtering technology.

[0052] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is as follows: In step S4, the nitrogen contents of the two chromium nitride layers are 25 at% and 45 at% respectively. The thickness of the chromium metal layer is 5 nm, the thickness of the chromium nitride layer with a nitrogen content of 25 at% is 7 nm, and the thickness of the outermost chromium nitride layer with a nitrogen content of 45 at% is 45 nm.

[0053] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is as follows: In step S4, the nitrogen contents of the two chromium nitride layers are 25 at% and 45 at% respectively. The thickness of the chromium metal layer is 35 nm, the thickness of the chromium nitride layer with a nitrogen content of 25 at% is 35 nm, and the thickness of the outermost chromium nitride layer with a nitrogen content of 45 at% is 15 nm.

[0054] Effect test: The performance of the composite current collectors prepared in Examples 1-5 and Comparative Examples 1-5 was measured.

[0055] The measured parameters are: 1) Bonding force: The bonding force test standard for current collectors refers to the "Test Method for Bonding Force of Composite Current Collectors" issued by the China Association of Automobile Manufacturers; 2) Residual stress test: The composite current collectors prepared in Examples 1-5 and Comparative Examples 1-6 were used as samples, and the residual stress was determined by Bruker D8 X-ray diffraction. XRD test conditions: 40kV, 40mA, scan rate 0.08 s / step, step size 0.01°, grazing incidence angle 3°; 3) Rate test: First, fully charge at the standard rate (0.5C), then discharge at the 5C rate, record the discharged capacity, and calculate the capacity retention rate at different rates by dividing the discharge capacity at this rate by the standard rate discharge capacity × 100%. 4) Cycle life: The capacity decay rate was recorded after 1000 cycles of repeated charging and discharging under standard charging and discharging conditions (1C charging, 1C discharging). 5) Lithium dendrite suppression: Assemble composite current collectors into lithium / lithium symmetric cells, at 2 mA / cm²... 2 2 mAh / cm 2 The sample was cycled 100 times under the specified conditions. After disassembly, the surface morphology was observed using a scanning electron microscope (SEM). The absence of needle-like lithium dendrites on the surface and the smooth and dense deposition layer were used as the evaluation criteria for excellent suppression effect.

[0056] The measurement results are shown in Table 1.

[0057] Table 1: Comparison of performance parameters between Examples 1-5 and Comparative Examples 1-5

[0058] As shown in Table 1, the test results of Examples 1-5 and Comparative Examples 1-5 demonstrate that the composite current collector proposed in this invention exhibits significant advantages in all performance aspects. In the examples, the use of plasma activation treatment, MOF interface layer, and stress compensation layer design resulted in low residual stress within the current collector, while also ensuring strong adhesion between the film layer and the polymer substrate. Regarding electrochemical performance, Examples 1-5 exhibited excellent rate performance and cycle life, and effectively suppressed lithium dendrite growth. This is mainly attributed to the MOF interface layer providing excellent ion transport channels and chemical anchoring, while the multilayer chromium nitride stress compensation layer balanced the internal stress generated during deposition, reducing the risk of interface defects and film cracking.

[0059] Compared to the examples, the overall performance of the comparative examples was significantly reduced. Comparative Example 1 omitted the substrate plasma activation pretreatment step, resulting in a lack of sufficient polar groups on the polymer surface to form chemical bonds with subsequent coatings. This led to a significant decrease in interfacial adhesion, increased residual stress, and the formation of numerous dendrites, resulting in reduced rate performance and cycle life. Comparative Example 2 lacked both the MOF interfacial layer and substrate activation treatment. The copper seed layer was directly deposited on the unmodified inert polymer surface, primarily through physical adsorption with extremely weak chemical bonding. The copper layer was easily peeled off, leading to intensified internal polarization and highly uneven lithium deposition, manifested as numerous dendrites and the highest cycle decay rate. Comparative Example 3 retained the front MOF layer and activation treatment but omitted the back stress compensation layer. In this case, the tensile stress generated by the front multilayer structure could not be offset by the back, resulting in high overall residual stress. Comparative Examples 4 and 5 both included stress compensation layers. In Comparative Example 4, the chromium metal layer and low-nitrogen layer were too thin (5 nm and 7 nm), failing to form an effective stress transition, resulting in insufficient adhesion and slight dendrite formation after cycling. In Comparative Example 5, the chromium metal layer and the low-nitrogen layer were too thick. The excessively thick low-nitrogen layer may have hindered electron conduction, resulting in a slightly lower rate performance than in the Example.

[0060] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A high-performance composite current collector, characterized in that, Includes a polymer support layer; An organometallic thin film interface layer is deposited on the front side of the polymer support layer; A first conductive layer is deposited on the organometallic thin film interface layer; A stress compensation layer is deposited on the back side of the polymer support layer; The stress compensation layer consists of a chromium metal layer deposited on the surface of the polymer support layer and a chromium nitride layer deposited on the surface of the chromium metal layer. A second conductive layer is deposited on the stress compensation layer.

2. The method for preparing the high-performance composite current collector according to claim 1, characterized in that, Includes the following steps: The polymer substrate is subjected to plasma treatment; Take a metal-organic framework material precursor solution and coat it on the front side of a plasma-treated polymer substrate to form a metal-organic thin film interface layer. A copper seed layer is deposited on the surface of the organometallic thin film interface layer; The back side of the plasma-treated polymer substrate is faced with a chromium target, and a chromium metal layer is deposited on the surface of the polymer substrate using high-power pulsed magnetron sputtering technology. Nitrogen gas is then introduced to deposit a chromium nitride layer on the surface of the chromium metal layer. The chromium metal layer and the chromium nitride layer together form a stress compensation layer. A copper seed layer is deposited on the surface of the chromium nitride layer; The two copper seed layers are thickened to obtain the first conductive layer and the second conductive layer.

3. The method for preparing the high-performance composite current collector according to claim 2, characterized in that, The polymer substrate is a polypropylene film, a polyethylene terephthalate film, or a polyimide film; The plasma treatment method is as follows: the polymer substrate is placed in a plasma treatment chamber, a working gas is introduced, and plasma treatment is performed under vacuum; the vacuum degree of the plasma treatment chamber is 0.5~2 Pa, the plasma power is 100~300 W, and the treatment time is 30~120 s; the working gas is an argon / oxygen mixture with a volume ratio of 7:3, or an argon / nitrogen mixture with a volume ratio of 6:

4.

4. The method for preparing the high-performance composite current collector according to claim 2, characterized in that, The method for preparing the organometallic framework precursor solution includes the following steps: ZrCl4 and terephthalic acid were dissolved in N,N-dimethylformamide, and acetic acid was added to obtain a UiO-66 precursor solution; wherein the molar ratio of ZrCl4 to terephthalic acid was 1:1, and the Zr content in the UiO-66 precursor solution was... 4+ The concentration is 0.1~0.3 mol / L.

5. The method for preparing the high-performance composite current collector according to claim 2, characterized in that, The method for preparing the organometallic thin film interface layer is as follows: The precursor solution of the organometallic framework material is coated onto the surface of the polymer substrate; the coated polymer substrate is heated to 60~85 ℃ and kept at this temperature for in-situ crystallization; finally, it is cleaned and vacuum dried to obtain the organometallic thin film interface layer.

6. The method for preparing the high-performance composite current collector according to claim 2, characterized in that, The method for preparing the stress compensation layer is as follows: The back side of the plasma-treated polymer substrate is faced with the chromium target, and the front side is shielded with a polytetrafluoroethylene mask. High-power pulsed magnetron sputtering technology is used, with the chromium target as the sputtering source and argon as the working gas, to deposit a chromium metal layer on the back side of the polymer substrate. Then, nitrogen gas is introduced into the deposition chamber, and a chromium nitride layer with a nitrogen content of 10~25 at% and a chromium nitride layer with a nitrogen content of 45~50 at% are sequentially deposited on the surface of the chromium metal layer. The pulse frequency of high-power pulsed magnetron sputtering is 10~50 Hz, and the duty cycle is 5~15%.

7. The method for preparing the high-performance composite current collector according to claim 2, characterized in that, The specific method for depositing the copper seed layer is as follows: High-power pulsed magnetron sputtering technology was used, with a Cu target as the sputtering source, and the power was controlled at 200~400 W, the working pressure at 0.1~0.2 Pa, and the temperature at no more than 40 ℃, to deposit a dense copper seed layer on the surface of the organometallic thin film interface layer / chromium nitride layer.

8. The method for preparing the high-performance composite current collector according to claim 2, characterized in that, The two copper seed layers were thickened, specifically as follows: The polymer substrate after depositing the copper seed layer is fed into a vertical continuous electroplating line, using a sulfate copper plating system with brighteners, leveling agents, and stress reducers added, while controlling the current density at 1~2 A / dm³. 2 The electroplating temperature is 20~30 ℃, the electroplating time is 20~40 min, and the final copper layer thickness is controlled at 1~3 μm.

9. The method for preparing the high-performance composite current collector according to claim 8, characterized in that, The sulfate copper plating system comprises CuSO4·5H2O and H2SO4; the concentration of CuSO4·5H2O is 180~220 g / L, and the concentration of H2SO4 is 60~80 g / L. The brightener is sodium polydisulfide dipropane sulfonate with a concentration of 2-5 mL / L; the leveling agent is diallyl dimethyl ammonium chloride-sulfur dioxide copolymer with a concentration of 1-3 mL / L; and the stress reducing agent is 2-mercaptobenzothiazole with a concentration of 3-6 mL / L.

10. The application of the high-performance composite current collector as described in claim 1 in the preparation of batteries.

Images