Negative electrode tab and preparation method thereof, negative electrode plate, soft package battery and vehicle

Abstract

The invention provides a negative electrode tab and a preparation method thereof, a negative electrode plate, a soft package battery and a vehicle. The negative tab comprises a substrate; the corrosion-resistant layer is arranged on at least one side of the substrate, a material for forming the corrosion-resistant layer comprises nickel phosphide, and the thickness fluctuation of the corrosion-resistant layer is smaller than or equal to 0.3 mu m. Therefore, the electrolyte resistance of the negative tab is improved.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a negative electrode tab and a preparation method thereof, a negative electrode sheet, a soft-pack battery and a vehicle. Background Art

[0002] The negative electrode tab is easily corroded in an electrolyte environment, causing battery failure. Therefore, special treatment is required on the surface of the negative electrode tab. For example, a coating can be formed on the surface of the negative electrode tab substrate to improve the corrosion resistance of the negative electrode tab. The corrosion resistance of the negative electrode tab in the related art has been limited. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, one object of the present invention is to provide a negative electrode tab and a preparation method thereof, a soft-pack battery and a vehicle. The corrosion-resistant layer on the surface of the negative electrode tab has a uniform thickness, which can improve the bonding ability between the corrosion-resistant layer and the substrate and improve the electrolyte resistance of the negative electrode tab.

[0004] A first aspect of the present invention provides a negative electrode tab, which includes a substrate; a corrosion-resistant layer, wherein the corrosion-resistant layer is arranged on at least one side of the substrate, the material forming the corrosion-resistant layer includes nickel phosphide, and the thickness fluctuation of the corrosion-resistant layer is less than or equal to 0.3μm.

[0005] The negative electrode tab proposed in the present invention has a corrosion-resistant layer including nickel phosphide. By making the thickness fluctuation of the corrosion-resistant layer less than or equal to 0.3 μm, the uniformity of the thickness distribution of the corrosion-resistant layer on the negative electrode tab is improved, the risk of local detachment of the corrosion-resistant layer due to uneven thickness is reduced, the internal bonding force of the corrosion-resistant layer is improved, and the overall electrolyte resistance of the negative electrode tab is improved.

[0006] The negative electrode tab proposed by the present invention also has the following additional technical features:

[0007] According to some embodiments of the present invention, the thickness of the corrosion-resistant layer is 0.6 μm-2.4 μm, thereby increasing the thickness of the corrosion-resistant layer and improving the electrolyte resistance of the negative electrode tab.

[0008] According to some embodiments of the present invention, the corrosion-resistant layer is disposed on at least one side of the substrate in the thickness direction, thereby improving the electrolyte resistance of the negative electrode tab.

[0009] According to some embodiments of the present invention, the material forming the substrate includes copper.

[0010] The second aspect of the present invention provides a method for preparing a negative electrode tab, the method comprising: using an AC power supply to form a corrosion-resistant layer on at least one side of a substrate, the material forming the corrosion-resistant layer comprises nickel phosphide, and the thickness fluctuation of the corrosion-resistant layer is less than or equal to 0.3 μm. As a result, the thickness of the corrosion-resistant layer on the negative electrode tab prepared by the method is more uniform, and the electrolyte resistance is stronger.

[0011] According to some embodiments of the present invention, the method includes placing metal nickel and copper strips in an electroplating solution, the electroplating solution includes nickel salt and phosphate salt, and forming the corrosion-resistant layer on at least one side of the substrate under the action of the AC power supply. Thus, the nickel phosphide layer as a corrosion-resistant layer can reduce the probability of corrosion of the substrate and improve the electrolyte resistance of the negative electrode tab.

[0012] According to some embodiments of the present invention, the forward voltage of the AC power source lasts for a time t1, the reverse voltage lasts for a time t2, and t1:t2=(2-10):1. Thus, the uniformity of the thickness of the corrosion-resistant layer is improved.

[0013] According to some embodiments of the present invention, the current density of the AC power supply is 2A / dm 2 -5A / dm 2 Thus, the rate of forming the corrosion-resistant layer by electroplating is increased, and the thickness of the corrosion-resistant layer is increased.

[0014] According to some embodiments of the present invention, the method satisfies at least one of the following conditions: the mass concentration of the nickel salt in the electroplating solution is 60g / L-150g / L; the mass concentration of the phosphate salt in the electroplating solution is 10g / -30g / L; the pH of the electroplating solution is 2-5; the temperature of the electroplating solution is 40°C-70°C. Thus, the rate of forming the corrosion-resistant layer by electroplating is increased, the thickness of the corrosion-resistant layer is increased, and the electrolyte resistance of the negative electrode tab is improved.

[0015] According to some embodiments of the present invention, the AC power supply is a pulsed AC power supply.

[0016] According to some embodiments of the present invention, the method further comprises: soaking the substrate having the corrosion-resistant layer in a passivation solution, thereby forming protective groups on the surface of the corrosion-resistant layer away from the substrate.

[0017] The third aspect of the present invention provides a negative electrode plate, comprising the negative electrode tab provided in the first aspect of the present invention or the negative electrode tab prepared by the method provided in the second aspect of the present invention.

[0018] The fourth aspect of the present invention provides a soft-pack battery, comprising the negative electrode sheet provided in the third aspect of the present invention.

[0019] The fifth aspect of the present invention provides a vehicle, comprising the soft-pack battery provided in the fourth aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0021] Figure 1 A schematic diagram of the negative electrode tab structure of an embodiment of the present invention is shown.

[0022] Figure 2 A schematic diagram showing chemical plating in the related art is shown.

[0023] Figure 3 A schematic diagram showing electroplating in the related art is shown.

[0024] Figure 4 A schematic diagram showing electroplating according to one embodiment of the present invention is shown.

[0025] Reference numerals:

[0026] 1: negative electrode tab; 11: substrate; 12: first corrosion-resistant layer; 13: second corrosion-resistant layer. DETAILED DESCRIPTION

[0027] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in this area or the product instructions are used. The reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0028] refer to Figure 2 In the related art, chemical plating is used to form a corrosion-resistant layer on the surface of the substrate. The coating formation speed is slow and the thickness of the formed corrosion-resistant layer is thin, which will affect the electrolyte resistance performance of the negative electrode tab to a certain extent; Reference Figure 3 , a corrosion-resistant layer can also be formed on the surface of the substrate by electroplating. Due to the uneven surface of the substrate, electroplating deposition is preferentially performed at the protruding positions, resulting in uneven thickness distribution of the corrosion-resistant layer. The corrosion-resistant layer on the surface of the substrate has poor bonding with the substrate. Although this method increases the speed of coating deposition and has a lower time cost, it reduces the electrolyte resistance of the negative electrode tab.

[0029] A first aspect of the present invention provides a negative electrode tab, comprising: a substrate; a corrosion-resistant layer, wherein the corrosion-resistant layer is arranged on at least one side of the substrate, the material forming the corrosion-resistant layer comprises nickel phosphide, and the thickness fluctuation of the corrosion-resistant layer is less than or equal to 0.3 μm.

[0030] The negative electrode tab proposed in the present invention has a corrosion-resistant layer including nickel phosphide. By making the thickness fluctuation of the corrosion-resistant layer less than or equal to 0.3 μm, the uniformity of the thickness distribution of the corrosion-resistant layer on the negative electrode tab is improved, the risk of local detachment of the corrosion-resistant layer due to uneven thickness is reduced, the internal bonding force of the corrosion-resistant layer is improved, and the overall electrolyte resistance of the negative electrode tab is improved.

[0031] In the present invention, the thickness fluctuation of the corrosion-resistant layer refers to the difference between the thickness of the corrosion-resistant layer at different positions of the negative electrode tab and the average thickness of the corrosion-resistant layer.

[0032] According to some embodiments of the present invention, the corrosion-resistant layer is disposed on at least one side of the substrate in a thickness direction. Figure 1 The negative electrode tab 1 includes a substrate 11, a first corrosion-resistant layer 12 is provided on one surface of the substrate 11, and a second corrosion-resistant layer 13 is provided on the other surface of the substrate 11, and the first corrosion-resistant layer 12 and the second corrosion-resistant layer 13 both include nickel phosphide.

[0033] According to an embodiment of the present invention, both the first corrosion-resistant layer 12 and the second corrosion-resistant layer 13 are nickel phosphide layers.

[0034] According to some embodiments of the present invention, the thickness of the corrosion-resistant layer may be 0.6 μm-2.4 μm. For example, it may be 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm or 2.4 μm, etc., or may be a range of any of the above values. Thus, the thickness of the corrosion-resistant layer is increased, the probability of the substrate of the negative electrode tab being corroded by the electrolyte is reduced, and the electrolyte resistance of the negative electrode tab is improved.

[0035] According to some embodiments of the present invention, the first corrosion-resistant layer 12 and the second corrosion-resistant layer 13 are both nickel phosphide layers, the thickness of the first corrosion-resistant layer 12 and the second corrosion-resistant layer 13 are independently 0.6 μm-2.4 μm, and the thickness fluctuation of the first corrosion-resistant layer 12 and the second corrosion-resistant layer 13 is less than or equal to 0.3 μm. Therefore, nickel phosphide is used as the corrosion-resistant layer to reduce the corrosion of the electrolyte on the substrate 11 and improve the electrolyte resistance of the negative electrode tab 1.

[0036] According to some embodiments of the present invention, the material forming the substrate 11 includes copper.

[0037] According to a specific embodiment of the present invention, the substrate 11 is a copper substrate. By forming a corrosion-resistant layer containing nickel phosphide on at least one side of the copper substrate 11, the corrosion of the copper substrate by the electrolyte is reduced, and the electrolyte resistance of the negative electrode tab is improved.

[0038] According to some embodiments of the present invention, the corrosion-resistant layer may further include a brightener to improve the brightness of the corrosion-resistant layer.

[0039] The second aspect of the present invention provides a method for preparing a negative electrode tab, referring to Figure 4 , the method comprises: using an alternating current power supply to form a corrosion-resistant layer on at least one side of the substrate, the material forming the corrosion-resistant layer comprises nickel phosphide, and the thickness fluctuation of the corrosion-resistant layer is less than or equal to 0.3 μm. Thus, when an alternating current power supply is used for electroplating, even if the surface of the substrate is uneven and the plating layer is preferentially deposited at the protruding position, the reverse current can reversely dissolve the thicker corrosion-resistant layer formed at the protruding position, preventing the corrosion-resistant layer from being continuously deposited at the protruding position, resulting in uneven thickness distribution, thereby improving the density of the corrosion-resistant layer, improving the uniformity of the thickness distribution of the corrosion-resistant layer on the surface of the substrate, improving the internal bonding force of the corrosion-resistant layer, and improving the overall electrolyte resistance performance of the negative electrode tab.

[0040] According to some embodiments of the present invention, the method includes placing metal nickel and copper strips in an electroplating solution, the electroplating solution includes nickel salt and phosphate salt, and forming the corrosion-resistant layer on at least one side of the substrate under the action of the AC power supply. Thus, a nickel phosphide layer can be formed on the surface of the copper substrate, reducing the probability of the copper substrate being corroded and improving the electrolyte resistance of the negative electrode tab.

[0041] According to some embodiments of the present invention, the thickness of the corrosion-resistant layer may be 0.6 μm-2.4 μm. For example, it may be 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm or 2.4 μm, etc., or may be a range of any of the above values. Thus, the thickness of the corrosion-resistant layer is increased, the probability of the substrate of the negative electrode tab being corroded by the electrolyte is reduced, and the electrolyte resistance of the negative electrode tab is improved.

[0042] According to some embodiments of the present invention, the AC power supply is a pulsed AC power supply.

[0043] According to some embodiments of the present invention, the forward voltage of the AC power source lasts for a time t1, and the reverse voltage lasts for a time t2, and t1:t2=(2-10):1. For example, it can be 2:1, 3:1, 5:1, 8:1 or 10:1, or can be a range of any of the above values.

[0044] As an example, when t1:t2 is 3:1, the forward voltage is applied for 3 seconds and then the reverse voltage is applied for 1 second.

[0045] According to some embodiments of the present invention, the current density of the AC power supply may be 2A / dm 2 -5A / dm 2For example, it can be 2A / dm 2 、3A / dm 2 , 4A / dm 2 or 5A / dm 2 etc., or can be any range of the above values. Thus, the rate of electroplating is increased and the cost is reduced.

[0046] According to some embodiments of the present invention, the mass concentration of the nickel salt in the electroplating solution may be 60 g / L-150 g / L, for example, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L, or may be a range of any of the above values. Thus, the electroplating rate is increased.

[0047] According to some embodiments of the present invention, the mass concentration of the phosphate salt in the electroplating solution may be 10 g / -30 g / L, for example, 10 g / L, 15 g / L, 20 g / L, 25 g / L or 30 g / L, or may be a range of any of the above values. Thus, the electroplating rate is increased.

[0048] According to some embodiments of the present invention, the pH of the electroplating solution may be 2-5, for example, 2, 3, 4 or 5.

[0049] According to some embodiments of the present invention, the temperature of the electroplating solution is 40° C.-70° C. For example, it can be 40° C., 45° C., 50° C., 55° C., 60° C., 65° C. or 70° C., or can be a range consisting of any of the above values.

[0050] According to some embodiments of the present invention, the method may further include: cleaning the copper strip before electroplating the copper strip.

[0051] According to some embodiments of the present invention, the cleaning includes: degreasing the copper strip using ultrasound. Specifically, the frequency of the ultrasound can be 20KHz-40KHz, for example, 20KHz, 24KHz, 28KHz, 32KHz, 36KHz or 40KHz, or can be a range of any of the above values. Thus, the cleaning effect is improved.

[0052] According to some embodiments of the present invention, the cleaning may further include: electrolytically degreasing the copper strip after the degreasing. Specifically, the current density during electrolytic degreasing may be 10 mA / dm 2 -100mA / dm 2 , for example, it can be 10mA / dm 2 , 20mA / dm 2 、30mA / dm2 , 40mA / dm 2 , 50mA / dm 2 、60mA / dm 2 、70mA / dm 2 、80mA / dm 2 , 90mA / dm 2 or 100mA / dm 2 The above-mentioned arbitrary numerical ranges may also be used.

[0053] According to some embodiments of the present invention, the cleaning may further include: after the electrolytic degreasing, pickling the copper strip. Specifically, the copper strip is placed in an acidic solution to remove an oxide layer on the surface of the copper strip. As an example, the acidic solution may be 10% sulfuric acid.

[0054] According to some embodiments of the present invention, the cleaning may further include activating the copper strip after the pickling. Specifically, the copper strip may be activated using dilute phosphoric acid.

[0055] According to some embodiments of the present invention, after forming a nickel phosphide layer on at least one side of the substrate using pulsed alternating current, the method may further include a process of immersing the substrate formed with the corrosion-resistant layer in a passivation solution to form a passivating group on the surface of the corrosion-resistant layer away from the substrate, thereby further improving the corrosion resistance of the negative electrode tab.

[0056] As an example, the composition of the passivation solution may refer to the composition of the passivation solution commonly used in the art. Specifically, the passivation solution may include phosphoric acid or a phosphoric acid compound, a trivalent chromium compound, a zirconium compound, a fluoride, an acrylic resin crosslinking agent, an auxiliary agent, and the like.

[0057] According to some embodiments of the present invention, after the copper strip formed with the nickel phosphide layer is immersed in the passivation solution, the copper strip may be cleaned and dried to accelerate the formation of the protective film.

[0058] The third aspect of the present invention provides a negative electrode plate, comprising the negative electrode tab provided in the first aspect of the present invention or the negative electrode tab prepared by the method provided in the second aspect of the present invention.

[0059] According to some embodiments of the present application, the negative electrode plate includes a negative electrode current collector, and the negative electrode tab is welded to the negative electrode current collector.

[0060] The fourth aspect of the present invention provides a soft-pack battery, comprising the negative electrode sheet provided by the third aspect of the present invention.

[0061] The fifth aspect of the present invention provides a vehicle, comprising the soft-pack battery provided in the fourth aspect of the present invention.

[0062] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0063] Example 1

[0064] (1) Ultrasonic degreasing: Use small bubbles generated by ultrasonic vibration to remove oil and foreign matter on the surface of the copper strip; the ultrasonic frequency is 30KHZ.

[0065] (2) Electrolytic degreasing: Remove the oil stains attached to the surface of the copper strip under the action of electric current; the current density is 50mA / dm 2 , degreasing time is 1 minute.

[0066] (3) Pickling: Place the copper strip in an acidic solution to remove the surface oxide layer; the acid solution is 10% sulfuric acid at a temperature of 40°C.

[0067] (4) Activation: The pickled copper strip is placed in a weak acid solution to activate the surface of the copper strip; dilute phosphoric acid is used in the activation process at a temperature of 40°C.

[0068] (5) Electroplating: Place the copper strip in the plating solution, and under the action of an external pulsed AC power supply, a layer of nickel phosphide is plated on the surface of the copper strip; the duration of the forward and reverse voltages is 3:1 (e.g., a forward voltage is applied for 3 seconds, followed by a reverse voltage for 1 second), the nickel salt in the plating solution is nickel sulfate with a concentration of 90 g / L, the concentration of sodium hypophosphite is 15 g / L, the pH value is 4, and the current density is 3 A / dm 2 , the plating solution temperature is 50℃.

[0069] (6) Surface treatment: 3 g of phosphoric acid, 4 g of chromium nitrate, 1 g of zirconium nitrate, 2 g of sodium fluoride, 4 g of acrylic resin, 1 g of a cross-linking agent obtained by the reaction of isocyanate and maleic anhydride, and sodium hydroxide were placed in 100 g of distilled water and mixed into a uniform plating solution. The copper strip plated with nickel phosphide was placed in the plating solution for surface treatment.

[0070] (7) Cleaning and drying: Wash with hot water and then dry to obtain the negative electrode tab.

[0071] Example 2

[0072] The preparation method of the negative electrode tab is the same as that of Example 1, except that the duration of the forward and reverse voltages is 2:1.

[0073] Example 3

[0074] The preparation method of the negative electrode tab is the same as that of Example 1, except that the duration of the forward and reverse voltages is 5:1.

[0075] Comparative Example 1

[0076] (1) Ultrasonic degreasing: Use small bubbles generated by ultrasonic vibration to remove oil and foreign matter on the surface of the copper strip; the ultrasonic frequency is 30KHZ.

[0077] (2) Electrolytic degreasing: Remove the oil stains attached to the surface of the copper strip under the action of electric current; the current density is 50mA / dm 2 , degreasing time is 1 minute.

[0078] (3) Pickling: Place the copper strip in an acidic solution to remove the surface oxide layer; the acid solution is 10% sulfuric acid at a temperature of 40°C.

[0079] (4) Activation: The pickled copper strip is placed in a weak acid solution to activate the surface of the copper strip; dilute phosphoric acid is used in the activation process at a temperature of 40°C.

[0080] (5) Chemical plating: The copper strip is placed in a plating solution, wherein the nickel salt is nickel sulfate with a concentration of 150 g / L, the concentration of sodium hypophosphite is 30 g / L, the pH value is 2, and the current density is 4 A / dm 2 The plating solution temperature is 60°C. The potential difference between nickel and copper is used to drive the concentration of the plating solution to evenly plate a layer of nickel phosphide on the surface of the copper strip.

[0081] (6) Surface treatment: 3 g of phosphoric acid, 4 g of chromium nitrate, 1 g of zirconium nitrate, 2 g of sodium fluoride, 4 g of acrylic resin, 1 g of a cross-linking agent obtained by the reaction of isocyanate and maleic anhydride, and sodium hydroxide were placed in 100 g of distilled water and mixed into a uniform plating solution. The copper strip plated with nickel phosphide was placed in the plating solution for surface treatment.

[0082] (7) Cleaning and drying: Wash with hot water and then dry to obtain the negative electrode tab.

[0083] Comparative Example 2

[0084] (1) Ultrasonic degreasing: Use small bubbles generated by ultrasonic vibration to remove oil and foreign matter on the surface of the copper strip; the ultrasonic frequency is 30KHZ.

[0085] (2) Electrolytic degreasing: Remove the oil stains attached to the surface of the copper strip under the action of electric current; the current density is 50mA / dm 2 , degreasing time is 1 minute.

[0086] (3) Pickling: Place the copper strip in an acidic solution to remove the surface oxide layer; the acid solution is 10% sulfuric acid at a temperature of 40°C.

[0087] (4) Activation: The pickled copper strip is placed in a weak acid solution to activate the surface of the copper strip; dilute phosphoric acid is used in the activation process at a temperature of 40°C.

[0088] (5) Electroplating: The copper strip is placed in a plating solution and a layer of nickel phosphide is plated on the surface of the copper strip under the action of a DC power supply; the nickel salt in the plating solution is nickel sulfate with a concentration of 120 g / L, the concentration of sodium hypophosphite is 20 g / L, the pH value is 3, and the current density is 4 A / dm 2 , the plating solution temperature is 60℃.

[0089] (6) Surface treatment: 3 g of phosphoric acid, 4 g of chromium nitrate, 1 g of zirconium nitrate, 2 g of sodium fluoride, 4 g of acrylic resin, 1 g of a cross-linking agent obtained by the reaction of isocyanate and maleic anhydride, and sodium hydroxide were placed in 100 g of distilled water and mixed into a uniform plating solution. The copper strip plated with nickel phosphide was placed in the plating solution for surface treatment.

[0090] (7) Cleaning and drying: Wash with hot water and then dry to obtain the negative electrode tab.

[0091] Performance Testing

[0092] 1. Coating thickness test

[0093] The coating thickness can be measured by storing a Ni metal template in an X-ray thickness gauge, but this test method is only for reference and has a low accuracy rate. Using a metallographic microscope to observe the cross section of the pole ear can clearly and intuitively obtain the true thickness of the coating.

[0094] 2. Electrolyte resistance performance test

[0095] An X-ray thickness gauge was used to measure the average thickness of the nickel phosphide layer in the negative electrode tab of each embodiment / comparative example, that is, the initial average thickness of the nickel phosphide layer; equal volumes of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed to obtain an organic solvent, and then lithium hexafluorophosphate was dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L, the electrolyte was placed in a beaker, and then the tab was placed, and immersed in a 60°C environment for 28 days, and the change in the coating thickness was observed. The average thickness of the nickel phosphide layer after immersion for 28 days was measured using an X-ray thickness gauge.

[0096] 3. Thickness fluctuation test method

[0097] An X-ray thickness gauge was used to test the thickness of the negative electrode tab of each embodiment / comparative example at ten different points (ten different points of one negative electrode tab), and the tab thickness fluctuation was calculated.

[0098] The test results of Example 1 to Example 3, Comparative Example 1 and Comparative Example 2 are shown in Table 1.

[0099] Table 1

[0100]

[0101] The retention rate of the nickel phosphide layer = (average thickness of the nickel phosphide layer after immersion for 28 days / initial average thickness of the nickel phosphide layer) × 100%.

[0102] The calculation method of the thickness fluctuation at different positions is: the absolute value of the difference between the thickness of the negative electrode ear at different positions and the initial average thickness of the nickel phosphide layer.

[0103]

[0104]

[0105] Conclusion: It can be seen from the comparison between Examples 1 to 3 and Comparative Example 1 that the thickness fluctuation of the nickel phosphide layer formed by the present invention through the use of a pulsed AC power supply for electroplating is less than or equal to 0.3 μm, indicating that the present invention can reduce the thickness fluctuation of the nickel phosphide layer while reducing the cost of forming the nickel phosphide layer. In addition, the nickel phosphide layer formed by the pulsed AC power supply has better electrolyte resistance.

[0106] It can be seen from the comparison of Examples 1 to 3 with Comparative Example 2 that the present invention can reduce the thickness fluctuation of the nickel phosphide layer by adopting a pulsed AC power supply instead of a DC power supply for electroplating, thereby improving the uniformity of the thickness distribution of the corrosion-resistant layer on the surface of the substrate and improving the electrolyte resistance of the negative electrode tab.

[0107] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A negative electrode tab, characterized in that: include: substrate; A corrosion-resistant layer is provided on at least one side of the substrate, the material forming the corrosion-resistant layer comprises nickel phosphide, and the thickness fluctuation of the corrosion-resistant layer is less than or equal to 0.3 μm.

2. The negative electrode tab according to claim 1, characterized in that: The thickness of the corrosion-resistant layer is 0.6 μm-2.4 μm.

3. The negative electrode tab according to claim 1 or 2, characterized in that: The corrosion-resistant layer is disposed on at least one side of the substrate in a thickness direction.

4. The negative electrode tab according to claim 1 or 2, characterized in that: The material forming the substrate includes copper.

5. A method for preparing a negative electrode tab, characterized in that: include: An AC power source is used to form a corrosion-resistant layer on at least one side of a substrate. The material forming the corrosion-resistant layer includes nickel phosphide. The thickness fluctuation of the corrosion-resistant layer is less than or equal to 0.3 μm.

6. The method according to claim 5, characterized in that The metal nickel and copper strips are placed in an electroplating solution comprising a nickel salt and a phosphorus salt, and the corrosion-resistant layer is formed on at least one side of the substrate under the action of the alternating current power source.

7. The method according to claim 5 or 6, characterized in that: The forward voltage of the AC power source lasts for a time t1, the reverse voltage lasts for a time t2, and t1:t2=(2-10):

1.

8. The method according to claim 5 or 6, characterized in that: The current density of the AC power supply is 2A / dm 2 -5A / dm 2 .

9. The method according to claim 6, characterized in that Satisfy at least one of the following conditions: The mass concentration of the nickel salt in the electroplating solution is 60g / L-150g / L; The mass concentration of the phosphate salt in the electroplating solution is 10g / -30g / L; The pH of the electroplating solution is 2-5; The temperature of the electroplating solution is 40°C-70°C.

10. The method according to claim 5 or 6, characterized in that: The AC power source is a pulse AC power source.

11. The method according to claim 5 or 6, characterized in that: Also includes: The process of soaking the substrate formed with the corrosion-resistant layer in a passivation solution.

12. A negative electrode plate, characterized in that: The invention comprises the negative electrode tab according to any one of claims 1 to 4 or the negative electrode tab prepared by the method according to any one of claims 5 to 11.

13. A soft pack battery, characterized in that: Including the negative electrode sheet as described in claim 12.

14. A vehicle, characterized in that: Including the soft pack battery as described in claim 13.

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