Preparation method of functional current collector with high tensile strength and battery using same

Abstract

The invention discloses a preparation method of a functional current collector with high tensile strength and a battery using the functional current collector, and relates to the technical field of current collectors. The preparation method of the functional current collector with high tensile strength comprises the following steps: 1, melting and uniformly mixing alloy powder, removing impurities, degassing and casting to obtain an alloy aluminum ingot; 2, after annealing treatment is conducted on the alloy aluminum ingot, the alloy aluminum ingot is extruded into a cylinder shape, then the cylinder shape is drawn and cut into alloy aluminum wires, and the alloy aluminum wires are cleaned, coiled and collected; and 3, evaporating an alloy aluminum wire on the surface of the base film by adopting an evaporation process to obtain the functional current collector with high tensile strength. The alloy powder comprises the following components in percentage by mass: 0.08-3.8% of rare earth metal powder and the balance of aluminum; wherein the rare earth metal powder comprises lanthanum, cerium, neodymium, yttrium, scandium, gadolinium, terbium and dysprosium. The high-tensile-strength functional current collector is provided with the high-density metal coating, so that the safety performance of a battery can be effectively improved, and the service life of the battery is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of current collectors, in particular to a method for preparing a high-tensile-strength functional current collector and a battery using the same. Background Art

[0002] Due to the limitations of traditional current collectors, the development of composite current collector (functional current collector) material industry has been promoted. Functional current collector is the most alternative new current collector material at present. Functional current collector is a material composed of a three-layer composite structure of metal-polymer material-metal. It uses polymer materials such as PET / PP as the intermediate layer base film and deposits a double layer of copper / aluminum conductive layer on the upper and lower surfaces. Compared with traditional current collectors, functional current collectors have the following advantages: (1) It can effectively reduce the amount of metal used, achieve cost reduction and weight reduction, and thus improve the energy density of the battery; (2) The burrs generated when punctured are small and can effectively absorb deformation stress, so it can also effectively avoid the problem of thermal runaway of the battery; (3) Since the polymer material layer will have a circuit-breaking effect, the short-circuit current can be controlled not to increase, thereby effectively controlling the thermal runaway of the battery and even explosion and fire; (4) It has high flexibility, which can make lithium ions deposit more evenly on the surface, inhibit the growth of lithium dendrites, and thus reduce the risk of short circuit in the battery. That is, while reducing costs, functional current collectors can also provide higher safety guarantees for lithium batteries.

[0003] At present, functional current collectors are usually prepared by evaporation, and the core process is one-step evaporation. First, evaporation equipment is used to convert solid aluminum into gaseous aluminum, and oxygen is introduced at the same time to react with aluminum atoms to form aluminum oxide, which is deposited on the base film for primer, forming a 5-15nm aluminum oxide layer; then vacuum is drawn and the base film metal layer is thickened to 1000nm using evaporation equipment. During the evaporation coating process, the evaporation boat is heated to about 1500℃, and the aluminum wire is transported to the center of the evaporation tank of the evaporation boat. After the aluminum wire is melted, it is transformed from liquid to gas, and the metal vapor is deposited on the PET or PE substrate to form a metal conductive layer.

[0004] With the pursuit of production efficiency, the production process has changed from suspended multiple plating to drum single plating. Suspended multiple plating means that the substrate is suspended above the evaporation source. Due to the heat resistance of the substrate, the coating speed is fast, and the thickness of one coating is about 50~90nm, so 10~20 coatings are required, and the production efficiency is low. Drum single plating means that there is a cooling constant temperature roller above the evaporation boat source. During coating, the substrate is close to the cooling roller, which can reduce the coating speed, and the one-time film thickness can reach 1000nm.

[0005] However, the functional current collector obtained by a single drum plating is prone to low tensile strength and low corrosion resistance of the coating layer to the electrolyte, which seriously affects the cycle life of the battery.

[0006] In summary, in order to solve the above problems, the present invention proposes a method for preparing a high tensile strength functional current collector and a battery using the same, which is of great significance. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing a high tensile strength functional current collector and a battery using the same, so as to solve the problems raised in the above background technology.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: A method for preparing a high tensile strength functional current collector comprises the following steps: Step 1: After the alloy powder is melted and mixed, it is removed from the mixture, degassed, and cast to obtain an alloy aluminum ingot; Step 2: After annealing the alloy aluminum ingot, extrude it into a cylindrical shape, then draw and cut it into alloy aluminum wire, clean it, and coil it for collection; Step 3: Use an evaporation process to evaporate the alloy aluminum wire onto the surface of the base film to obtain a composite aluminum current collector, that is, a high tensile strength functional current collector.

[0009] Furthermore, the alloy powder comprises the following components: by mass fraction, 0.08-3.8% rare earth metal powder and the rest aluminum.

[0010] Furthermore, the alloy powder includes the following components: by mass fraction, 0.02-1% lanthanum, 0.02-1% cerium, 0.01-0.5% neodymium, 0.01-0.5% yttrium, 0.005-0.2% scandium, 0.005-0.2% gadolinium, 0.005-0.2% terbium, 0.005-0.2% dysprosium, and the rest is aluminum.

[0011] Furthermore, in step 1, the melting temperature is 780-850°C.

[0012] Furthermore, in step 2, the parameters of the annealing treatment are: annealing temperature is 380-420° C., and annealing time is 6-18 hours.

[0013] Furthermore, the diameter of the cylindrical aluminum alloy ingot is 5-10 mm.

[0014] Furthermore, the diameter of the alloy aluminum wire is 1.5-2.5 mm.

[0015] Furthermore, the specific process of step three is as follows: (1) fixing the base film on the winding roller, performing film reeling and tension adjustment, controlling the tension at the film unwinding end to be 110-150N, and the tension at the film rewinding end to be 80-120N; (2) placing the alloy aluminum wire in the evaporation equipment, evaporating the evaporation chamber to a vacuum, and preheating the evaporation boat temperature to 1400-1550°C, starting evaporation, and allowing the alloy aluminum wire to be evaporated onto both surfaces of the base film to obtain a high tensile strength functional current collector.

[0016] Furthermore, the parameters of the evaporation process are: the vacuum degree is 3~6×10 -3 Pa, wire feeding rate is 400~500mm / min, film running speed is 8~12m / min, and the temperature of cooling roller is -25~-15℃.

[0017] Under the premise of satisfying the physical properties and appearance properties of the composite aluminum current collector, the present invention adds rare earth elements to the metal layer of the composite aluminum current collector to change the grain size of the metal layer, thereby achieving the purpose of increasing the density of the metal layer of the composite aluminum current collector. For the same substance, the larger the packing density value, the smaller the gap between particles. Furthermore, grain refinement can significantly improve the strength and hardness of the metal, thereby improving the tensile strength of the composite aluminum current collector. This is because the grain boundary is an obstacle to the movement of dislocations. The finer the grains, the larger the total area of ​​the grain boundaries, the greater the obstruction to the movement of dislocations, and the greater the tensile strength of the material.

[0018] Furthermore, a lithium battery using a high tensile strength functional current collector.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are: (1) The high tensile strength functional current collector prepared by the present invention has the characteristic of high tensile strength. When the battery pole piece is rolled, the functional current collector is not easily deformed, thereby improving the cycle life of the battery; (2) The high tensile strength functional current collector prepared by the present invention is used in lithium batteries and can withstand the pressure and temperature changes inside the battery; during the charge and discharge process, the functional current collector can automatically adjust the change in battery volume, thereby improving the safety performance of the battery; (3) The metal coating density on the high tensile strength functional current collector prepared by the present invention is relatively high, which enhances the peeling force of the metal coating to a certain extent and also improves the electrolyte corrosion resistance of the functional current collector; in addition, due to the higher density of the metal coating, the internal resistance of the high tensile strength functional current collector prepared by the present invention is smaller, which can reduce the loss of the battery during discharge and improve the cycle life of the battery. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] It should be noted that the purchasers of all raw materials involved in the present invention include, without any special restrictions, illustratively: In the following embodiments, Lanthanum, cerium, neodymium, yttrium, scandium, gadolinium, terbium, and dysprosium, all with a purity of ≥99.99%, were purchased from Ganzhou Kemingrui Nonferrous Metal Materials Co., Ltd.; Aluminum, purity ≥99.99%, purchased from Pingyin Guanghui Aluminum Co., Ltd.; The electrolyte, model EC / EMC / DMC / LiF6, was purchased from Jiangxi Jinhui Lithium Battery Materials Co., Ltd.

[0022] Example 1: A method for preparing a high tensile strength functional current collector: Step 1: Weigh the raw material components according to the alloy powder formula, mix them evenly, add them into the furnace, heat them to 800°C, then reduce the vacuum degree of the furnace, remove impurities and degassing, and then cast to obtain alloy aluminum ingots; The alloy powder comprises the following components: by mass fraction, 0.2% lanthanum, 0.2% cerium, 0.1% neodymium, 0.1% yttrium, 0.05% scandium, 0.05% gadolinium, 0.05% terbium, 0.05% dysprosium, and the remainder is aluminum; Step 2: Place the alloy aluminum ingot in an annealing furnace, heat it to 400°C, and keep it warm for 12 hours to complete the annealing treatment; then extrude it into a cylindrical alloy aluminum ingot of φ8mm; finally, draw and cut it into alloy aluminum wire of φ2mm, clean it, and coil it for collection; Step 3: Use the evaporation process to evaporate the alloy aluminum wire onto the surface of the PP base film to obtain a high tensile strength functional current collector: (1) Fix a 6 μm thick PP base film on a winding roller, and adjust the film tension. The tension at the film unwinding end is controlled to be 130 N, and the tension at the film rewinding end is controlled to be 100 N. (2) After placing the alloy aluminum wire in the evaporation equipment, the evaporation chamber is evacuated to a vacuum, and the evaporation boat temperature is preheated to 1500 ° C. The evaporation is started, and the alloy aluminum wire is evaporated onto both surfaces of the PP base film to obtain a high tensile strength functional current collector. The parameters of the evaporation process are: vacuum degree is 5×10 -3 Pa, the wire feed rate was 450 mm / min, the film running speed was 10 m / min, and the temperature of the cooling roller was -20 °C.

[0023] Example 2: A method for preparing a high tensile strength functional current collector: Step 1: Weigh the raw material components according to the alloy powder formula, mix them evenly, add them into the furnace, heat them to 800°C, then reduce the vacuum degree of the furnace, remove impurities and degassing, and then cast to obtain alloy aluminum ingots; The alloy powder comprises the following components: by mass fraction, 1% lanthanum, 1% cerium, 0.5% neodymium, 0.5% yttrium, 0.2% scandium, 0.2% gadolinium, 0.2% terbium, 0.2% dysprosium, and the remainder is aluminum; Step 2: Place the alloy aluminum ingot in an annealing furnace, heat it to 400°C, and keep it warm for 12 hours to complete the annealing treatment; then extrude it into a cylindrical alloy aluminum ingot of φ8mm; finally, draw and cut it into alloy aluminum wire of φ2mm, clean it, and coil it for collection; Step 3: Use the evaporation process to evaporate the alloy aluminum wire onto the surface of the PP base film to obtain a high tensile strength functional current collector: (1) Fix a 6 μm thick PP base film on a winding roller, and adjust the film tension. The tension at the film unwinding end is controlled to be 130 N, and the tension at the film rewinding end is controlled to be 100 N. (2) After placing the alloy aluminum wire in the evaporation equipment, the evaporation chamber is evacuated to a vacuum, and the evaporation boat temperature is preheated to 1500 ° C. The evaporation is started, and the alloy aluminum wire is evaporated onto both surfaces of the PP base film to obtain a high tensile strength functional current collector. The parameters of the evaporation process are: vacuum degree is 5×10 -3 Pa, the wire feed rate was 450 mm / min, the film running speed was 10 m / min, and the temperature of the cooling roller was -20 °C.

[0024] Example 3: A method for preparing a high tensile strength functional current collector: Step 1: Weigh the raw material components according to the alloy powder formula, mix them evenly, add them into the furnace, heat them to 800°C, then reduce the vacuum degree of the furnace, remove impurities and degassing, and then cast to obtain alloy aluminum ingots; The alloy powder comprises the following components: by mass fraction, 0.02% lanthanum, 0.02% cerium, 0.01% neodymium, 0.01% yttrium, 0.005% scandium, 0.005% gadolinium, 0.005% terbium, 0.005% dysprosium, and the remainder is aluminum; Step 2: Place the alloy aluminum ingot in an annealing furnace, heat it to 400°C, and keep it warm for 12 hours to complete the annealing treatment; then extrude it into a cylindrical alloy aluminum ingot of φ8mm; finally, draw and cut it into alloy aluminum wire of φ2mm, clean it, and coil it for collection; Step 3: Use the evaporation process to evaporate the alloy aluminum wire onto the surface of the PP base film to obtain a high tensile strength functional current collector: (1) Fix a 6 μm thick PP base film on a winding roller, and adjust the film tension. The tension at the film unwinding end is controlled to be 130 N, and the tension at the film rewinding end is controlled to be 100 N. (2) After placing the alloy aluminum wire in the evaporation equipment, the evaporation chamber is evacuated to a vacuum, and the evaporation boat temperature is preheated to 1500 ° C. The evaporation is started, and the alloy aluminum wire is evaporated onto both surfaces of the PP base film to obtain a high tensile strength functional current collector. The parameters of the evaporation process are: vacuum degree is 5×10 -3 Pa, the wire feed rate was 450 mm / min, the film running speed was 10 m / min, and the temperature of the cooling roller was -20 °C.

[0025] Comparative Example 1: Compared with Example 1, Comparative Example 1 is adjusted by using aluminum wire instead of alloy aluminum wire, and other processes remain unchanged, specifically: Step 1: Use the evaporation process to evaporate aluminum wire (φ2mm) onto the surface of the PP base film to obtain a high tensile strength functional current collector: (1) Fix a 6 μm thick PP base film on a winding roller, and adjust the film tension. The tension at the film release end is controlled to be 130 N, and the tension at the film collection end is controlled to be 100 N. (2) After placing the aluminum wire in the evaporation equipment, the evaporation chamber is evacuated to a vacuum, and the evaporation boat temperature is preheated to 1500 ° C. The evaporation is started, and the alloy aluminum wire is evaporated onto both surfaces of the PP base film to obtain a high tensile strength functional current collector. The parameters of the evaporation process are: vacuum degree is 5×10 -3 Pa, the wire feed rate was 450 mm / min, the film running speed was 10 m / min, and the temperature of the cooling roller was -20 °C.

[0026] Performance test: The high tensile strength functional current collectors prepared in Examples 1 to 3 and Comparative Example 1 were subjected to relevant tests, as follows: 1. Physical data test: 1. Tensile strength: (1) Cut the high tensile strength functional current collector into test strips of 100 mm × 15 mm; (2) Use a tensile testing machine to clamp the two ends of the high tensile strength functional current collector strip and move it at a uniform tensile speed of 100 mm / min. When the high tensile strength functional current collector breaks, record the tensile strength and elongation at break; 2. Coating peeling force: (1) Cut the high tensile strength functional current collector into test specimens with a size of 100 mm × 15 mm; (2) Stick 3M-9080A-15 mm tape on a stainless steel plate, and then evenly stick the test specimen on the double-sided tape, use a 2 kg standard small roller to roll back and forth twice, then stick 3M-9080A-14 mm tape on the surface of the test specimen, and use a 2 kg standard small roller to roll back and forth twice; (3) Then place the pressed test specimen on a tensile testing machine for 180° tensile peeling, the speed is 100 mm / min, the width is set to 14 mm, and the maximum peeling strength is recorded; 3. Sheet resistance: Use a sheet resistance meter to measure the sheet resistance of the high tensile strength functional current collector.

[0027] The results of the above physical data test are shown in Table 1 below: Table 1

[0028] Result analysis: By comparing the data of Examples 1 to 3 and Comparative Example 1 in Table 1 above, it can be seen that the alloy aluminum wire prepared by mixing rare earth metals and aluminum has a better tensile strength than ordinary aluminum wire, and the functional current collector obtained by vapor deposition has a higher coating peeling force, which is as high as 1844 N / m, which is much higher than the functional current collector obtained by vapor deposition of ordinary aluminum wire; and its square resistance is also smaller, which can reduce the loss of the battery during discharge.

[0029] 2. Electrolyte corrosion resistance test: The high tensile strength functional current collector is immersed in the electrolyte. The electrolyte model is EC / EMC / DMC / LiF6. The electrolyte corrosion resistance is tested after immersion for 1 day, 3 days, 7 days, 15 days, 30 days and 45 days. The specific method is as follows: (1) After the surface of the high tensile strength functional current collector soaked in electrolyte is cleaned with 99.9% alcohol, it is placed in an oven at 25°C for surface drying; (2) After it is dried, it is cut into test specimens with a size of 100 mm × 15 mm; (3) 3M-9080A-15mm tape is attached to a stainless steel plate, and then the test specimen is evenly attached to the double-sided tape, and a 2kg standard small pressure roller is used to roll it back and forth twice, and then 3M-9080A-14mm tape is attached to the surface of the test specimen, and a 2kg standard small pressure roller is used to roll it back and forth twice; (4) The pressed test specimen is then placed on a tensile testing machine for 180° tensile peeling, the speed is 100 mm / min, the width is set to 14 mm, and the maximum peel strength is recorded.

[0030] The test results of electrolyte corrosion resistance are shown in Table 2 below: Table 2

[0031] Conclusion analysis: By comparing the data of Examples 1 to 3 and Comparative Example 1 in Table 2 above, it can be seen that the alloy aluminum wire prepared by mixing rare earth metals and aluminum has a functional current collector obtained by vapor deposition, which has significantly stronger corrosion resistance to the electrolyte than ordinary aluminum wire.

[0032] In summary, the present invention prepares a high tensile strength functional current collector by evaporating an alloy aluminum wire prepared by mixing rare earth metals and aluminum. The metal coating of the high tensile strength functional current collector has a higher density, so that the metal coating peeling force and electrolyte corrosion resistance of the functional current collector are enhanced; at the same time, the high tensile strength functional current collector prepared by the present invention has a smaller internal resistance, which can reduce the loss of the battery during discharge. Applying it in a battery can comprehensively improve the cycle life of the battery.

[0033] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a high tensile strength functional current collector, characterized in that: The following steps are involved: Step 1: After the alloy powder is melted and mixed, it is removed from the mixture, degassed, and cast to obtain an alloy aluminum ingot; Step 2: After annealing the alloy aluminum ingot, extrude it into a cylindrical shape, then draw and cut it into alloy aluminum wire, clean it, and coil it for collection; Step 3: Use the evaporation process to evaporate the alloy aluminum wire onto the surface of the base film to obtain a high tensile strength functional current collector.

2. The method for preparing a high tensile strength functional current collector according to claim 1, characterized in that: The alloy powder comprises the following components: by mass fraction, 0.08-3.8% of rare earth metal powder and the rest of aluminum.

3. The method for preparing a high tensile strength functional current collector according to claim 2, characterized in that: The alloy powder comprises the following components: by mass fraction, 0.02-1% lanthanum, 0.02-1% cerium, 0.01-0.5% neodymium, 0.01-0.5% yttrium, 0.005-0.2% scandium, 0.005-0.2% gadolinium, 0.005-0.2% terbium, 0.005-0.2% dysprosium, and the rest is aluminum.

4. The method for preparing a high tensile strength functional current collector according to claim 1, characterized in that: In step 1, the melting temperature is 780-850° C.; in step 2, the parameters of the annealing treatment are: the annealing temperature is 380-420° C., and the annealing time is 6-18 hours.

5. The method for preparing a high tensile strength functional current collector according to claim 1, characterized in that: The diameter of the cylindrical aluminum alloy ingot is 5-10 mm; the diameter of the aluminum alloy wire is 1.5-2.5 mm.

6. The method for preparing a high tensile strength functional current collector according to claim 1, characterized in that: The specific process of step three is as follows: (1) fix the base film on the winding roller, and adjust the film tension by retracting and releasing the film, and control the tension at the film releasing end to be 110-150N and the tension at the film collecting end to be 80-120N; (2) place the alloy aluminum wire on the evaporation equipment, evacuate the evaporation chamber to vacuum, and preheat the evaporation boat temperature to 1400-1550°C, start evaporation, and evaporate the alloy aluminum wire onto the two surfaces of the base film to obtain a high tensile strength functional current collector.

7. The method for preparing a high tensile strength functional current collector according to claim 6, characterized in that: The parameters of the evaporation process are: vacuum degree is 3~6×10 -3 Pa, wire feeding rate is 400~500mm / min, film running speed is 8~12m / min, and the temperature of cooling roller is -25~-15℃.

8. A battery using a high tensile strength functional current collector, characterized in that: A lithium battery using a high tensile strength functional current collector prepared by the preparation method according to any one of claims 1 to 7.

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