Low-crimp iron-nickel alloy foil suitable for all-solid-state battery and preparation method thereof

Abstract

The invention relates to the technical field of iron-nickel alloy foil preparation, and discloses a low-curl iron-nickel alloy foil suitable for an all-solid-state battery and a preparation method of the low-curl iron-nickel alloy foil. The electrolyte solution is added into an electrolytic cell, and current is applied to the electrolyte solution; the method comprises the following steps: depositing an iron-nickel alloy on the surface of a cathode roller, stripping to obtain an iron-nickel alloy foil, carrying out electrophoresis on the iron-nickel alloy foil by using a magnesium oxide electrophoresis solution in an electrophoresis cell to form a magnesium oxide coating on the iron-nickel alloy foil, cleaning with an acid solution, and carrying out electrochemical fluorination treatment on the iron-nickel alloy foil to obtain the magnesium oxide coating on the iron-nickel alloy foil. Forming a fluorinated layer on the magnesium oxide coating; and the iron-nickel alloy foil is subjected to heat treatment at the temperature not exceeding 600 DEG C in a heat treatment chamber, and the iron-nickel alloy foil is obtained after cooling. The high-quality iron-nickel invar iron-nickel alloy foil can solve the curling problem and is suitable for all-solid-state batteries.

Description

Technical Field

[0001] The invention relates to the technical field of iron-nickel alloy foil preparation, and more specifically, to a low-curl iron-nickel alloy foil suitable for all-solid-state batteries and a preparation method thereof. Background Art

[0002] With the continuous development of all-solid-state battery technology, many secondary battery companies on the market are actively conducting research on all-solid-state batteries. Compared with ordinary lithium batteries using liquid electrolytes, all-solid-state batteries do not require the use of diaphragms to prevent the flow of liquid electrolytes, and can directly fill the position with solid electrolytes, thereby achieving higher volume density and energy density. In addition, all-solid-state batteries are less affected by temperature changes and have excellent physical and chemical stability. They also have safety advantages such as not easy to burn and explode, no electrolyte leakage and drying, and high thermal stability. In low-temperature environments, the solid electrolyte ion conductivity of all-solid-state batteries is better than that of liquid electrolytes, and can maintain a higher power output, greatly improving the endurance performance in low-temperature environments.

[0003] However, in the application of sulfide-based all-solid-state batteries, the copper material traditionally used as the negative electrode current collector is easily corroded by sulfides, so technicians are studying the use of iron-nickel Invar iron-nickel alloy foil as an alternative material. However, the Invar iron-nickel alloy foil prepared by the existing technology often curls due to internal stress problems, making it impossible to achieve uniform coating in the production process of coating the active material on the negative electrode current collector, which seriously affects normal production.

[0004] Therefore, how to solve the curling problem and produce high-quality iron-nickel invar iron-nickel alloy foil suitable for all-solid-state batteries has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] The present invention provides a low-curl iron-nickel alloy foil suitable for all-solid-state batteries and a preparation method thereof, which solves the technical problem of the prior art of being able to solve the curling problem and providing a high-quality iron-nickel invar iron-nickel alloy foil suitable for all-solid-state batteries.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions: In a first aspect, the present invention provides a method for preparing a low curl iron-nickel alloy foil suitable for an all-solid-state battery, comprising the following steps: (1) An anode plate and a cathode roller are separately arranged in an electrolytic cell, an electrolyte solution is added to the electrolytic cell, and an electric current is applied to the electrolyte solution to deposit an iron-nickel alloy on the surface of the cathode roller, and then an iron-nickel alloy foil is obtained by peeling; Among them, the electrolyte solution includes an iron salt solution, a nickel salt solution, additives and pure water. The additives are composed of a stress reliever, a pH stabilizer, an Fe reducing agent, a conductive aid and a wetting agent. The electrolyte solution contains: 10 - 100 g / L of the iron salt solution, 5 - 50 g / L of the nickel salt solution, 1.0 - 3.0 g / L of the stress reliever, 15.0 - 30.0 g / L of the pH stabilizer, 0.1 - 3.0 g / L of the Fe reducing agent, 10.0 - 25.0 g / L of the conductive aid and 0.1 - 1.0 g / L of the wetting agent; (2) Electrophorese the iron-nickel alloy foil in an electrophoresis bath using a magnesium oxide electrophoresis solution to form a magnesium oxide coating on the iron-nickel alloy foil. After cleaning with an acid solution, electrochemically fluorinate the iron-nickel alloy foil to form a fluorinated layer on the magnesium oxide coating; (3) Heat-treat the iron-nickel alloy foil in a heat treatment chamber at a temperature not exceeding 600 °C, and obtain the iron-nickel alloy foil after cooling.

[0007] Further, the temperature of the electrolyte solution is 45 - 65 °C, the applied current density is 6 - 10 A / dm2, the flow rate of the electrolyte solution is 20 - 40 m3 / hr, and the pH of the electrolyte solution is adjusted with sulfuric acid and sodium carbonate, pH = 2.0 - 3.0.

[0008] Further, in the electrolyte solution: The iron salt is any one of ferric sulfate, ferric chloride or ferric carbonate; The nickel salt is any one of nickel sulfate, nickel chloride, nickel hydroxide or nickel carbonate; The stress reliever is any one of sodium saccharin, 1,4-butanediol, diphenylsulfimide, sodium allylsulfonate or 2-propylheptanol; The pH stabilizer is any one of boric acid, sodium borate or boron nitride; The Fe reducing agent is any one of glucose, ascorbic acid, sodium gluconate or glycine; The conductive aid is any one of sodium chloride, sodium sulfate, sodium carbonate or sodium citrate; The wetting agent is any one of sodium succinate, sodium dodecylbenzenesulfonate or sodium hydroxyethylsulfonate.

[0009] Further, in the electrolyte solution: The iron salt is ferric sulfate, the nickel salt is nickel sulfate, the stress reliever is sodium saccharin, the pH stabilizer is boric acid, the Fe reducing agent is ascorbic acid, the conductive aid is sodium chloride, and the wetting agent is sodium succinate. Among them, the content of ferric sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, the content of sodium saccharin is 2.8 g / L, the content of boric acid is 30 g / L, the content of ascorbic acid is 2.9 g / L, the content of sodium chloride is 23.8 g / L, and the content of sodium succinate is 1.0 g / L.

[0010] Further, during the electrophoresis of the iron-nickel alloy foil using the magnesium oxide electrophoresis solution in the electrophoresis bath: The magnesium oxide electrophoresis solution includes 5 - 20 g / L of magnesium oxide powder, 3 - 8 g / L of isopropyl alcohol solution, 0.3 - 0.8 g / L of dispersant, and pure water; The electrophoresis conditions are: voltage 40 - 80 V, current density 5 - 15 mA / cm2, time 20 - 40 s, temperature 20 - 30 °C; After electrophoresis, the iron-nickel alloy foil is dried at 165 - 200 °C for 5 - 15 min.

[0011] Further, the acid solution is a 10 - 12 wt% dilute hydrochloric acid solution or dilute sulfuric acid solution.

[0012] Further, the electrochemical fluorination treatment of the iron-nickel alloy foil is specifically as follows: A three-electrode system is adopted, using the iron-nickel alloy foil as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode. The electrolyte is a 0.10 - 0.15 mol / L ammonium fluoride solution, pH = 4.0 - 4.2; the electrolysis conditions are: voltage 2 - 5 V, current density 5 - 15 mA / cm2, temperature 15 - 25 °C, and the treatment time is 10 - 30 s.

[0013] Further, the heat treatment temperature is 400 - 600 °C, the heat treatment time is 5 - 30 min, vibration is applied after cooling, the vibration frequency is 1000 - 5000 Hz, the amplitude is 0.05 - 0.2 mm, and the vibration time is 5 - 20 min.

[0014] In a second aspect, the present invention provides a low-curling iron-nickel alloy foil suitable for all-solid-state batteries, which is obtained by the preparation method of the low-curling iron-nickel alloy foil suitable for all-solid-state batteries described above.

[0015] Further, the thickness of the iron-nickel alloy foil is 1 μm - 10 μm, and the degree of curling is 2 - 5 mm.

[0016] The beneficial effects of the present invention are as follows: The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries of the present invention successfully solves the problem of curling of nickel-iron alloy foil caused by internal stress in the prior art by adding stress relievers, pH stabilizers, Fe reducers, conductive aids, and wetting agents in specific proportions to the electrolyte. The prepared iron-nickel alloy foil has a thickness of 3-10 μm, excellent surface quality, and the roughness of the S surface and M surface is controlled below Ra: 0.30 μm and Rz: 1.50 μm respectively; In the method of the present invention, through the synergistic effect of additive adjustment, electrophoretic magnesium oxide coating, fluorinated layer, and heat treatment process, the internal stress of the iron-nickel alloy foil is effectively reduced. Both magnesium oxide and fluorinated layer have good chemical stability and corrosion resistance, and can form a dense protective film on the surface of the iron-nickel alloy foil to isolate the contact between corrosive media and the alloy foil, thereby slowing down the corrosion rate of the alloy foil and improving its service life. It can improve the wear resistance of the surface of the iron-nickel alloy foil, further reduce the curling degree. After heat treatment, the iron-nickel alloy foil has a tensile strength of 1100-1400 MPa and an elongation of 1.50%-3.50% at room temperature, and the curling degree does not exceed 5 mm. Heat treatment makes the metal structure finer, effectively inhibits the curling phenomenon, solves the possible corrosion problem during the use of the negative electrode current collector material of the secondary battery, and at the same time ensures that the active material can be evenly coated, thus ensuring the high yield and high quality of the iron-nickel alloy foil; The iron-nickel alloy foil prepared by the present invention does not contain copper, avoiding the problem that copper materials are easily corroded in sulfide-based all-solid-state batteries, making it an ideal core material for the negative electrode current collector of sulfide-based all-solid-state batteries. Compared with existing lithium-ion batteries, the sulfide-based all-solid-state battery prepared by this process has more excellent specifications and stability, and is an innovative product that solves the core problems of the future secondary battery industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flowchart for synthesizing iron-nickel alloy foil using an electrolyte solution. DETAILED DESCRIPTION OF THE INVENTION

[0018] Now the subject matter described herein will be discussed with reference to exemplary embodiments. It should be understood that discussing these embodiments is only to enable those skilled in the art to better understand and thus implement the subject matter described herein, and the functions and arrangements of the elements discussed can be changed without departing from the scope of protection of the content of this specification. Each example can omit, substitute, or add various processes or components as needed. Additionally, the features described in some examples can also be combined in other examples.

[0019] At least one embodiment of the present invention discloses a low-curling iron-nickel alloy foil applicable to all-solid-state batteries and its preparation method, including: Preparation method of low-curling iron-nickel alloy foil applicable to all-solid-state battery, and the specific method is as follows: (1) The anode plate and the cathode roller are separately arranged in the electrolytic cell, the electrolyte solution is added to the electrolytic cell, and an electric current is applied to the electrolyte solution to deposit iron-nickel alloy on the surface of the cathode roller, and then the iron-nickel alloy foil is obtained by peeling. The iron content in the iron-nickel alloy foil is 55%-85%, the nickel content is 15%-45%, and the thickness of the iron-nickel alloy foil is 1μm - 10μm.

[0020] Refer to Figure 1 , by preparing the iron-nickel alloy foil through the electrolytic deposition process and adding additives in a specific proportion, the microstructure and surface morphology of the alloy can be effectively controlled. The precise proportion of the additives in the electrolyte solution is a core of the present invention, which can significantly reduce the curling degree of the iron-nickel alloy foil and improve its applicability in the battery manufacturing process.

[0021] (2) Electrophoresis is carried out on the iron-nickel alloy foil with magnesium oxide electrophoresis solution in the electrophoresis tank to form a magnesium oxide coating on the iron-nickel alloy foil. After being cleaned with acid solution, the iron-nickel alloy foil is subjected to electrochemical fluorination treatment to form a fluorinated layer on the magnesium oxide coating.

[0022] By obtaining a magnesium oxide coating on the iron-nickel alloy foil through the electrophoresis process and then electrochemically fluorinating the iron-nickel alloy foil, using the good chemical stability and corrosion resistance of the magnesium oxide coating and the fluorinated layer, a dense protective film is formed on the surface of the iron-nickel alloy foil to isolate the contact between the corrosive medium and the alloy foil, thereby slowing down the corrosion rate of the alloy foil and increasing its service life. It can improve the wear resistance of the surface of the iron-nickel alloy foil and further reduce the curling degree.

[0023] (3) The iron-nickel alloy foil is heat-treated in the heat treatment chamber at a temperature not exceeding 600°C, and the iron-nickel alloy foil is obtained after cooling.

[0024] The heat-treated iron-nickel alloy foil has a tensile strength of 1100 - 1400 MPa and an elongation of 1.50% - 3.50% at room temperature, and the curling degree does not exceed 5 mm. Heat treatment makes the metal structure finer, effectively inhibits the curling phenomenon, solves the possible corrosion problem during the use of the current collector material for the negative electrode of the secondary battery, and at the same time ensures that the active material can be evenly coated, thus ensuring the high yield and high quality of the iron-nickel alloy foil.

[0025] In another preferred embodiment of the present invention, the anode plate is composed of Ti + Ir, and the cathode roll is composed of Ti. Among them, when using Ti for the cathode roll, on the one hand, it has good corrosion resistance: titanium has very good corrosion resistance and is not easily corroded by the electrolyte solution, so it can be used for a long time, extending its service life; on the other hand, it has good electrical conductivity: titanium has good electrical conductivity and can efficiently conduct current as an electrode in the electroplating manufacturing process.

[0026] For the Ti + Ir used in the anode plate, on the one hand, it has good corrosion resistance: like the cathode roll, titanium has very good corrosion resistance and will not be corroded by the electrolyte solution, so it can be used for a long time; on the other hand, it has strong electrochemical stability: iridium has extremely high electrochemical stability, and when the positive electrode plate is subjected to high voltage or reacts with the electrolyte solution, it has strong durability; at the same time, the used Ti + Ir has good catalytic effects: iridium can play a role in promoting the electrochemical reaction and can efficiently assist the electrochemical reaction in the electrolyte solution.

[0027] For the above reasons, the above materials play an important role in the interaction with the electrolyte solution, with representative corrosion resistance and electrochemical stability, making them stable and efficient electrode materials during the preparation process. The chemical environment of the electrolyte solution is extreme, and the durability and electrochemical properties provided by these materials are crucial for ensuring manufacturing efficiency and quality.

[0028] The electrolyte solution includes iron salt solution, nickel salt solution, additives and pure water. The additives are composed of a stress reliever, a pH stabilizer, an Fe reducing agent, a conductive aid and a wetting agent. The electrolyte solution contains: 10 - 100 g / L of iron salt solution, 5 - 50 g / L of nickel salt solution, 1.0 - 3.0 g / L of stress reliever, 15.0 - 30.0 g / L of pH stabilizer, 0.1 - 3.0 g / L of Fe reducing agent, 10.0 - 25.0 g / L of conductive aid and 0.1 - 1.0 g / L of wetting agent; iron salts and nickel salts have different effects on the deposition rate, grain size and internal stress of the alloy. By selecting the appropriate type of metal salt, the microstructure and mechanical properties of the alloy can be optimized.

[0029] Among them, the iron salt is any one of ferric sulfate, ferric chloride or ferric carbonate, the nickel salt is any one of nickel sulfate, nickel chloride, nickel hydroxide or nickel carbonate, the stress reliever is any one of sodium saccharin, 1,4 - butanediol, diphenylsulfimide, sodium allylsulfonate or 2 - propylheptanol, the pH stabilizer is any one of boric acid, sodium borate or boron nitride, the Fe reducing agent is any one of glucose, ascorbic acid, sodium gluconate or glycine, the conductive aid is any one of sodium chloride, sodium sulfate, sodium carbonate or sodium citrate, and the wetting agent is any one of sodium succinate, sodium dodecylbenzenesulfonate or sodium hydroxyethylsulfonate.

[0030] The pH value of the electrolyte solution is adjusted by sulfuric acid and sodium carbonate to maintain a pH value of 2.0 - 3.0. When adjusting the pH value, if the pH value is lower than the appropriate value of 2.0 - 3.0, sodium carbonate is used to increase the pH value to the appropriate range. If the pH value is higher than the appropriate value, sulfuric acid is used to lower the pH value to the appropriate range. The temperature of the electrolyte solution is 45 - 65 °C, the applied current density is 6 - 10 A / dm2, and the flow rate of the electrolyte solution is 20 - 40 m3 / hr. The control of the temperature, current density, flow rate, and pH value of the electrolyte solution, and the optimized design of these parameters can ensure the stable progress of the electrodeposition process and obtain a uniform and dense alloy deposition layer. The precise control of the pH value is crucial for preventing hydrogen evolution and metal hydroxide precipitation, and can improve the current efficiency and deposition quality.

[0031] In another preferred embodiment of the present invention, electrophoresis of the iron-nickel alloy foil is carried out using a magnesium oxide electrophoresis solution. Specifically: The iron-nickel alloy foil is placed in an electrophoresis bath. The magnesium oxide electrophoresis solution contains 5 - 20 g / L of magnesium oxide powder, 3 - 8 g / L of isopropyl alcohol solution, 0.3 - 0.8 g / L of dispersant, and pure water. The electrophoresis conditions are: voltage 40 - 80 V, current density 5 - 15 mA / cm2, time 20 - 40 s, and temperature 20 - 30 °C. After electrophoresis, the iron-nickel alloy foil is dried at 165 - 200 °C for 5 - 15 min.

[0032] Electrochemical fluorination treatment of the iron-nickel alloy foil is carried out. Specifically: A three-electrode system is adopted, using the iron-nickel alloy foil as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode. The electrolyte is a 0.10 - 0.15 mol / L ammonium fluoride solution with a pH of 4.0 - 4.2. The electrolysis conditions are: voltage 2 - 5 V, current density 5 - 15 mA / cm2, temperature 15 - 25 °C, and treatment time 10 - 30 s.

[0033] In another preferred embodiment of the present invention, heat treatment is carried out in a heat treatment chamber. The heat treatment temperature is 400 - 600 °C, the heat treatment time is 5 - 30 min. After cooling, vibration is applied with a vibration frequency of 1000 - 5000 Hz, an amplitude of 0.05 - 0.2 mm, and a vibration time of 5 - 20 min. During the heat treatment process, if the temperature and time are lower than the above values, the internal stress may not be reduced. If they are higher than the above values, the tensile strength of the iron-nickel alloy foil will be reduced. The heat treatment process promotes the rearrangement of metal atoms by providing appropriate heat energy, releases the internal stress generated during the deposition process, promotes grain growth and recrystallization at the same time, optimizes the microstructure of the alloy, improves the mechanical properties and stability of the alloy, and thus effectively reduces the curling phenomenon of the iron-nickel alloy foil.

[0034] In summary, by optimizing the electrolytic deposition process parameters and additive formulations, the present invention synthesizes a magnesium oxide coating and a fluorinated layer on the surface of the foil, and through a suitable heat treatment process, successfully prepares a low-curling iron-nickel alloy foil applicable to all-solid-state batteries. This iron-nickel alloy foil has excellent mechanical properties, surface morphology, and dimensional stability, can significantly improve the manufacturing efficiency and performance stability of all-solid-state batteries, and has important practical value.

[0035] The following further describes the present application in combination with examples and comparative examples. It is necessary to point out here that the following specific examples are only used to further illustrate the present application and should not be construed as limiting the protection scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0036] 1. Description Unless otherwise specified, the methods used in the present invention are conventional methods known to those skilled in the art. The reagents and other materials used, unless otherwise specified, are commercially available products, and the instruments used, unless otherwise specified, are conventional instruments known to those skilled in the art.

[0037] 2. Methods 2.1 Influence of electrolyte solution additive adjustment on iron-nickel alloy foil Example 1 (1) The anode plate and the cathode roller are separately arranged in the electrolytic cell, the electrolyte solution is added to the electrolytic cell, a current is applied to the electrolyte solution, the electrolyte solution temperature is 62 ± 2 °C, the current density is 8 A / dm2, the electrolyte solution flow rate is 30 m3 / hr, and the pH value of the electrolyte solution is adjusted with sulfuric acid and sodium carbonate to be maintained at 2.2 ± 0.5. The iron-nickel alloy is deposited on the surface of the cathode roller, and the iron-nickel alloy foil is obtained by peeling; (2) Electrophoresis of the iron-nickel alloy foil is carried out in an electrophoresis bath using a magnesium oxide electrophoresis solution: Electrophoresis solution: 5 g / L of magnesium oxide powder (purity 99%, particle size range 0.5 - 1 μm) and isopropanol solution, with 0.5 g / L of dispersant added; Electrophoresis conditions: voltage 60 V, current density 10 mA / cm2, time 30 s, temperature 25 °C; A uniform magnesium oxide layer is formed; Drying treatment: 10 min at 170 °C to form a magnesium oxide coating on the iron-nickel alloy foil with a thickness ≤ 1.0 μm; After cleaning with a 10 wt% dilute hydrochloric acid solution, electrochemical fluorination treatment is carried out on the iron-nickel alloy foil: Using the iron-nickel alloy foil as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode, the electrolyte solution is 0.10 mol / L ammonium fluoride solution with pH = 4.0; Electrolysis conditions: voltage 3 V, current density 10 mA / cm2, temperature 20 °C, treatment time 10 s to form a fluorinated layer on the magnesium oxide coating with a thickness at the nanometer level; (3) The iron-nickel alloy foil is heat-treated at 400 °C for 30 min in a heat treatment chamber. After cooling, it is placed on a vibrating table to apply vibration. The vibration frequency is 1000 Hz, the amplitude is 0.05 mm, and the vibration time is 10 min. After cooling, the iron-nickel alloy foil is obtained.

[0038] In the electrolyte solution of this example, the content of ferric sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, the content of sodium saccharin is 1.1 g / L, the content of boric acid is 15.5 g / L, the content of ascorbic acid is 0.1 g / L, the content of sodium chloride is 11.6 g / L, and the content of sodium succinate is 0.2 g / L.

[0039] Example 2 The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries in this example is the same as that in Example 1 except for the different addition amounts.

[0040] In the electrolyte solution of this example, the content of ferric sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, the content of sodium saccharin is 1.6 g / L, the content of boric acid is 19 g / L, the content of ascorbic acid is 0.7 g / L, the content of sodium chloride is 14.4 g / L, and the content of sodium succinate is 0.4 g / L.

[0041] Example 3 The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries in this example is the same as that in Example 1 except for the different addition amounts.

[0042] In the electrolyte solution of this example, the content of ferric sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, the content of sodium saccharin is 2.0 g / L, the content of boric acid is 22.5 g / L, the content of ascorbic acid is 1.5 g / L, the content of sodium chloride is 17.5 g / L, and the content of sodium succinate is 0.6 g / L.

[0043] Example 4 The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries in this example is the same as that in Example 1 except for the different addition amounts.

[0044] In the electrolyte solution of this example, the content of ferric sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, the content of sodium saccharin is 2.5 g / L, the content of boric acid is 26 g / L, the content of ascorbic acid is 2.1 g / L, the content of sodium chloride is 20.7 g / L, and the content of sodium succinate is 0.8 g / L.

[0045] Example 5 The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries in this example is the same as that in Example 1 except for the different addition amounts.

[0046] In the electrolyte solution of this example, the ferric sulfate content is 43.2 g / L, the nickel sulfate content is 18.6 g / L, the sodium saccharin content is 2.8 g / L, the boric acid content is 30 g / L, the ascorbic acid content is 2.9 g / L, the sodium chloride content is 23.8 g / L, and the sodium succinate content is 1.0 g / L.

[0047] Example 6 A method for preparing a low-curling iron-nickel alloy foil applicable to all-solid-state batteries, the electrolyte temperature is 45 ± 2 °C, the current density is 10 A / dm2, the electrolyte solution flow rate is 30 m3 / hr, and sulfuric acid and sodium carbonate are used to adjust the pH value of the electrolyte solution to be maintained at 2.2 ± 0.5.

[0048] In the electrolyte solution of this example, the ferric chloride content is 58 g / L, the nickel chloride content is 33.6 g / L, the diphenylsulfonylimide content is 1 g / L, the sodium borate content is 15 g / L, the glucose content is 0.5 g / L, the sodium sulfate content is 10 g / L, and the sodium dodecylbenzenesulfonate content is 0.1 g / L.

[0049] The rest is the same as in Example 1.

[0050] Example 7 A method for preparing a low-curling iron-nickel alloy foil applicable to all-solid-state batteries in this example, the electrolyte temperature is 62 ± 2 °C, the current density is 6 A / dm2, the electrolyte solution flow rate is 30 m3 / hr, and sulfuric acid and sodium carbonate are used to adjust the pH value of the electrolyte solution to be maintained at 2.2 ± 0.5.

[0051] In the electrolyte solution of this example, the ferric sulfate content is 93.6 g / L, the nickel carbonate content is 49.5 g / L, the 2-propylheptanol content is 2.5 g / L, the boric acid content is 26 g / L, the glycine content is 2.1 g / L, the sodium citrate content is 20.7 g / L, and the sodium succinate content is 0.8 g / L.

[0052] The rest is the same as in Example 1.

[0053] Example 8 A method for preparing a low-curling iron-nickel alloy foil applicable to all-solid-state batteries, the electrolyte temperature is 50 ± 2 °C, the current density is 8 A / dm2, the electrolyte solution flow rate is 40 m3 / hr, and sulfuric acid and sodium carbonate are used to adjust the pH value of the electrolyte solution to be maintained within the range of 2.5 ± 0.5; In the electrolyte solution of this example, the iron carbonate content is 61.7 g / L, the nickel hydroxide content is 6.1 g / L, the sodium allylsulfonate content is 3 g / L, the boron nitride content is 30 g / L, the sodium gluconate content is 3 g / L, the sodium carbonate content is 25 g / L, and the sodium 2-hydroxyethylsulfonate content is 1 g / L.

[0054] The rest is the same as in Example 1.

[0055] Comparative Example 1 The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries in this comparative example is the same as that in Example 1 except for the different addition amounts.

[0056] In the electrolyte solution of this comparative example, the content of ferric sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, boric acid is 15.4 g / L, ascorbic acid is 0.1 g / L, sodium chloride is 11.7 g / L, and sodium succinate is 1.0 g / L.

[0057] Comparative Example 2 The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries in this comparative example is the same as that in Example 1 except for the different addition amounts.

[0058] In the electrolyte solution of this comparative example, the content of ferric sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, boric acid is 22.5 g / L, ascorbic acid is 1.5 g / L, sodium chloride is 17.5 g / L, and sodium succinate is 0.5 g / L.

[0059] Comparative Example 3 The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries in this comparative example is the same as that in Example 1 except for the different addition amounts.

[0060] In the electrolyte solution of this comparative example, the content of ferric sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, sodium saccharin is 2.0 g / L, boric acid is 22.7 g / L, ascorbic acid is 1.6 g / L, and sodium chloride is 17.6 g / L.

[0061] Comparative Example 4 The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries in this comparative example is the same as that in Example 1 except for the different addition amounts.

[0062] In the electrolyte solution of this comparative example, the content of ferric sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, sodium saccharin is 0.5 g / L, boric acid is 7.8 g / L, ascorbic acid is 0.05 g / L, sodium chloride is 5.0 g / L, and sodium succinate is 0.05 g / L.

[0063] Comparative Example 5 The preparation method of the iron-nickel alloy foil applicable to all-solid-state batteries in this comparative example is the same as that in Example 8 except for the different additive compositions.

[0064] In the electrolyte solution of this comparative example, the content of iron carbonate is 61.7 g / L, the content of nickel hydroxide is 6.1 g / L, the content of boron nitride is 30 g / L, the content of sodium gluconate is 3 g / L, and the content of sodium carbonate is 25 g / L. In this comparative example, sodium allyl sulfonate is not added as a stress reliever and sodium 2-hydroxyethyl sulfonate is not added as a wetting agent, resulting in the curl of the obtained iron-nickel alloy foil exceeding 5 mm and the tensile strength being significantly reduced.

[0065] Comparative Example 6 The preparation method of the iron-nickel alloy foil applicable to all-solid-state batteries in this comparative example is the same as that of Example 8 except for the different additive contents.

[0066] In the electrolyte solution of this comparative example, the content of iron carbonate is 61.7 g / L, the content of nickel hydroxide is 6.1 g / L, the content of sodium allyl sulfonate is 0.5 g / L, the content of boron nitride is 10 g / L, the content of sodium gluconate is 0.05 g / L, the content of sodium carbonate is 5 g / L, and the content of sodium 2-hydroxyethyl sulfonate is 0.05 g / L. In this comparative example, the contents of the additives are all lower than the standard values, resulting in an increase in the surface roughness of the obtained iron-nickel alloy foil and the curl reaching more than 7 mm.

[0067] Effect verification: The performance indexes of the iron-nickel alloy foils obtained in Examples 1-8 and Comparative Examples 1-5 were detected, and the results are shown in Table 1.

[0068] Table 1: Performance indexes of the iron-nickel alloy foils obtained in Examples 1-8 and Comparative Examples 1-6

[0069] Note: The above detection methods and instruments are all conventional technologies.

[0070] By comparing the experimental data of Examples 1-8 and Comparative Examples 1-6 in the table, the following detailed conclusions can be drawn: Example 1: Using a current density of 8 A / dm2, the surface roughness of the S surface and the M surface is Ra: 0.29 μm / Rz: 1.45 μm and Ra: 0.30 μm / Rz: 1.48 μm respectively, and an iron-nickel alloy foil with a tensile strength of 1155 MPa, an elongation of 3.20%, and a curl of 5 mm is obtained. This example demonstrates that the method of the present invention can prepare a low-curl iron-nickel alloy foil with good surface quality and mechanical properties.

[0071] Example 2: Using a current density of 8 A / dm2, the surface roughness of the S surface and the M surface is Ra: 0.26 μm / Rz: 1.41 μm and Ra: 0.27 μm / Rz: 1.43 μm respectively, and an iron-nickel alloy foil with a tensile strength of 1219 MPa, an elongation of 2.81%, and a curl of 4 mm is obtained. Compared with Example 1, the tensile strength is increased and the curl is reduced.

[0072] Example 3: Using a current density of 8 A / dm2, the surface roughness of the S side and the M side is Ra: 0.25 μm / Rz: 1.39 μm and Ra: 0.25 μm / Rz: 1.41 μm respectively, and a nickel-iron alloy foil with a tensile strength of 1282 MPa, an elongation of 2.36%, and a curl of 3 mm is obtained. The surface roughness is further reduced, the tensile strength continues to increase, and the curl is further improved.

[0073] Example 4: Using a current density of 8 A / dm2, the surface roughness of the S side and the M side is Ra: 0.20 μm / Rz: 1.33 μm and Ra: 0.22 μm / Rz: 1.37 μm respectively, and a nickel-iron alloy foil with a tensile strength of 1344 MPa, an elongation of 1.98%, and a curl of 3 mm is obtained. The surface quality is significantly improved, and the tensile strength reaches a relatively high level.

[0074] Example 5: Using a current density of 8 A / dm2, the surface roughness of the S side and the M side is Ra: 0.18 μm / Rz: 1.31 μm and Ra: 0.19 μm / Rz: 1.32 μm respectively, and a nickel-iron alloy foil with a tensile strength of 1381 MPa, an elongation of 1.56%, and a curl of 2 mm is obtained. It has the best surface quality, the highest tensile strength, and the lowest curl among all examples, but the elongation decreases slightly.

[0075] Example 6: Using a current density of 10 A / dm2, the surface roughness of the S side and the M side is Ra: 0.27 μm / Rz: 1.38 μm and Ra: 0.29 μm / Rz: 1.43 μm respectively, and a nickel-iron alloy foil with a tensile strength of 1210 MPa, an elongation of 3.2%, and a curl of 3 mm is obtained. It is proved that under a higher current density, the method of the present invention can still obtain excellent properties.

[0076] Example 7: Using a current density of 6 A / dm2, the surface roughness of the S side and the M side is Ra: 0.26 μm / Rz: 1.41 μm and Ra: 0.28 μm / Rz: 1.42 μm respectively, and a nickel-iron alloy foil with a tensile strength of 1340 MPa, an elongation of 3.0%, and a curl of 3 mm is obtained. It is proved that under a lower current density, the method of the present invention is equally effective.

[0077] Example 8: Using a current density of 8 A / dm2, the surface roughness of the S side and the M side is Ra: 0.26 μm / Rz: 1.39 μm and Ra: 0.29 μm / Rz: 1.44 μm respectively, and a nickel-iron alloy foil with a tensile strength of 1298 MPa, an elongation of 3.1%, and a curl of 2 mm is obtained. It demonstrates the stability and repeatability of the method of the present invention.

[0078] Comparative Example 1: An iron-nickel alloy foil with a current density of 8 A / dm2, surface roughness of Ra: 1.09 μm / Rz: 2.22 μm and Ra: 1.30 μm / Rz: 2.29 μm for the S and M surfaces respectively, was obtained with a tensile strength of 691 MPa, elongation of 4.66%, and curl of 20 mm. The surface roughness far exceeded the standard, the tensile strength was significantly reduced, and the curl was severe, making it unsuitable as a current collector for all-solid-state batteries.

[0079] Comparative Example 2: An iron-nickel alloy foil with a current density of 8 A / dm2, surface roughness of Ra: 0.98 μm / Rz: 2.09 μm and Ra: 1.08 μm / Rz: 2.11 μm for the S and M surfaces respectively, was obtained with a tensile strength of 843 MPa, elongation of 4.01%, and curl of 17 mm. Although the performance was slightly better than that of Comparative Example 1, it was still far from that of the examples.

[0080] Comparative Example 3: An iron-nickel alloy foil with a current density of 8 A / dm2, surface roughness of Ra: 0.78 μm / Rz: 1.97 μm and Ra: 0.99 μm / Rz: 2.04 μm for the S and M surfaces respectively, was obtained with a tensile strength of 983 MPa, elongation of 3.98%, and curl of 10 mm. The tensile strength increased, but the curl was still too large.

[0081] Comparative Example 4: An iron-nickel alloy foil with a current density of 8 A / dm2, surface roughness of Ra: 0.64 μm / Rz: 1.81 μm and Ra: 0.84 μm / Rz: 1.85 μm for the S and M surfaces respectively, was obtained with a tensile strength of 778 MPa, elongation of 4.31%, and curl of 16 mm. The tensile strength was even lower than that of Comparative Example 3, and the curl was still severe.

[0082] Comparative Example 5: An iron-nickel alloy foil with a current density of 8 A / dm2, surface roughness of Ra: 0.70 μm / Rz: 1.85 μm and Ra: 0.75 μm / Rz: 1.90 μm for the S and M surfaces respectively, was obtained with a tensile strength of 720 MPa, elongation of 4.25%, and curl of 15 mm. The tensile strength was low and the curl was high, not meeting the requirements.

[0083] Comparative Example 6: An iron-nickel alloy foil with a current density of 8 A / dm2, surface roughness of Ra: 0.45 μm / Rz: 1.65 μm and Ra: 0.48 μm / Rz: 1.70 μm for the S and M surfaces respectively, was obtained with a tensile strength of 1050 MPa, elongation of 3.85%, and curl of 8 mm. The performance was close but still did not meet the requirement of low curl.

[0084] Comprehensive analysis shows that, by precisely controlling the types and amounts of additives, the method of the present invention successfully prepares iron-nickel alloy foils with low surface roughness (Ra < 0.30 μm, Rz < 1.50 μm), high tensile strength (1155 - 1381 MPa), and small curl (≤5 mm). These properties are crucial for the performance of the negative current collector of all-solid-state batteries. In particular, the low curl property can ensure uniform coating of the active material, improving the production efficiency and quality of the batteries.

[0085] By comparing the experimental data of Examples 1 - 8 and Comparative Examples 1 - 6, the following conclusions can be drawn: In Examples 1 - 8, the tensile strength of the iron-nickel alloy foils is within the range of 1155 - 1381 MPa, significantly higher than that of 691 - 1098 MPa in Comparative Examples 1 - 6, indicating that the iron-nickel alloy foils prepared by the method of the present invention have higher mechanical strength.

[0086] The elongation of Examples 1 - 8 is between 1.56% - 3.20%, lower than that of 3.74% - 4.66% in Comparative Examples 1 - 6, which shows that the iron-nickel alloy foils prepared by the method of the present invention have appropriate ductility while maintaining high strength characteristics.

[0087] The most significant difference lies in the degree of curl. The curl of Examples 1 - 8 is within the range of 2 - 5 mm, while the curl of Comparative Examples 1 - 6 is between 7 - 20 mm. This proves that the iron-nickel alloy foils prepared by the method of the present invention have significantly low curl characteristics, which is crucial for the manufacturing process of all-solid-state batteries.

[0088] In Comparative Examples 1 - 6, due to the types or amounts of additives not meeting the requirements of the present invention, the performance of the iron-nickel alloy foils deteriorates, especially the curl increases significantly, which will affect the uniform coating of the active material in the subsequent battery manufacturing process.

[0089] Examples 6 - 8 show that under different current densities (6 - 10 A / dm2), as long as the appropriate additive ratio is maintained, iron-nickel alloy foils with low curl can be obtained, proving that the method of the present invention has good process adaptability.

[0090] In summary, the types and amounts of additives in the method of the present invention are crucial and are the core of the present invention. Only within the above ranges of the types and amounts of additives can the excellent performance of the prepared iron-nickel alloy foils be ensured. As shown in Table 1 and Table 2, the iron-nickel alloy foils prepared by adding 5 kinds of additives in Examples 1 - 8 have a tensile strength of 1100 - 1400 MPa at room temperature, an elongation of 1.5 - 3.5% at room temperature after heat treatment, and in addition, it can be confirmed that the curl degree is below 5 mm.

[0091] 2.2 Influence of Coating Adjustment and Heat Treatment on Iron-Nickel Alloy Foil Comparative Example 7 (1) The anode plate and the cathode roller are separately arranged in the electrolytic cell. The electrolyte solution is added to the electrolytic cell, and an electric current is applied to the electrolyte solution. The temperature of the electrolyte solution is 62 ± 2 °C, the current density is 8 A / dm2, the flow rate of the electrolyte solution is 30 m3 / hr, and the pH value of the electrolyte solution is adjusted to 2.2 ± 0.5 with sulfuric acid and sodium carbonate. Iron-nickel alloy is deposited on the surface of the cathode roller, and iron-nickel alloy foil is obtained by stripping. Among them, in the electrolyte solution, the content of ferric sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, the content of sodium saccharin is 2.8 g / L, the content of boric acid is 30 g / L, the content of ascorbic acid is 2.9 g / L, the content of sodium chloride is 23.8 g / L, and the content of sodium succinate is 1.0 g / L.

[0092] (2) After cleaning the iron-nickel alloy foil with a 10 wt% dilute hydrochloric acid solution, the iron-nickel alloy foil is subjected to electrochemical fluorination treatment: using the iron-nickel alloy foil as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode, the electrolyte solution is 0.10 mol / L ammonium fluoride solution, pH = 4.0; electrolysis conditions: voltage 3 V, current density 10 mA / cm2, temperature 20 °C, treatment time 10 s, to form a fluorinated layer with a thickness at the nanometer level; (3) The iron-nickel alloy foil is heat-treated at 400 °C for 30 min in the heat treatment chamber, cooled, placed on a vibrating table, and vibrated. The vibration frequency is 1000 Hz, the amplitude is 0.05 mm, and the vibration time is 10 min. After cooling, iron-nickel alloy foil is obtained.

[0093] This comparative example does not include a magnesium oxide coating compared with Example 5.

[0094] Comparative Example 8 (1) The anode plate and the cathode roller are separately arranged in the electrolytic cell. The electrolyte solution is added to the electrolytic cell, and an electric current is applied to the electrolyte solution. The temperature of the electrolyte solution is 62 ± 2 °C, the current density is 8 A / dm2, the flow rate of the electrolyte solution is 30 m3 / hr, and the pH value of the electrolyte solution is adjusted to 2.2 ± 0.5 with sulfuric acid and sodium carbonate. Iron-nickel alloy is deposited on the surface of the cathode roller, and iron-nickel alloy foil is obtained by stripping. Among them, in the electrolyte solution, the content of ferric sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, the content of sodium saccharin is 2.8 g / L, the content of boric acid is 30 g / L, the content of ascorbic acid is 2.9 g / L, the content of sodium chloride is 23.8 g / L, and the content of sodium succinate is 1.0 g / L.

[0095] (2) Electrophoresis of iron-nickel alloy foil using magnesium oxide electrophoresis solution in an electrophoresis cell: Electrophoresis solution: 5 g / L of magnesium oxide powder (purity 99%, particle size 0.8 μm) and isopropyl alcohol solution, adding 0.5 g / L of dispersant; Electrophoresis conditions: voltage 60 V, current density 10 mA / cm2, time 30 s, temperature 25 °C; forming a uniform magnesium oxide layer; Drying treatment: 10 min at 170 °C to form a magnesium oxide coating on the iron-nickel alloy foil, with a thickness ≤ 1.0 μm; (3) Heat-treat the iron-nickel alloy foil in a heat-treatment chamber at 400 °C for 30 min, cool it and then place it on a vibrating table to apply vibration. The vibration frequency is 1000 Hz, the amplitude is 0.05 mm, and the vibration time is 10 min. After cooling, the iron-nickel alloy foil is obtained.

[0096] This comparative example does not include a fluorinated layer compared with Example 5.

[0097] Comparative Example 9 (1) Separate the anode plate and the cathode roller in an electrolytic cell, add the electrolyte solution to the electrolytic cell, apply current to the electrolyte solution, the electrolyte solution temperature is 62 ± 2 °C, the current density is 8 A / dm2, the electrolyte solution flow rate is 30 m3 / hr, adjust the pH value of the electrolyte solution to be maintained at 2.2 ± 0.5 with sulfuric acid and sodium carbonate, deposit the iron-nickel alloy on the surface of the cathode roller, and obtain the iron-nickel alloy foil by peeling; Among them, in the electrolyte solution, the content of ferric sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, the content of saccharin sodium is 2.8 g / L, the content of boric acid is 30 g / L, the content of ascorbic acid is 2.9 g / L, the content of sodium chloride is 23.8 g / L, and the content of sodium succinate is 1.0 g / L.

[0098] (2) Heat-treat the iron-nickel alloy foil in a heat-treatment chamber at 400 °C for 30 min, cool it and then place it on a vibrating table to apply vibration. The vibration frequency is 1000 Hz, the amplitude is 0.05 mm, and the vibration time is 10 min. After cooling, the iron-nickel alloy foil is obtained.

[0099] This comparative example does not include a magnesium oxide coating and a fluorinated layer compared with Example 5.

[0100] Comparative Example 10 (1) Separate the anode plate and the cathode roller in an electrolytic cell, add the electrolyte solution to the electrolytic cell, apply current to the electrolyte solution, the electrolyte solution temperature is 62 ± 2 °C, the current density is 8 A / dm2, the electrolyte solution flow rate is 30 m3 / hr, adjust the pH value of the electrolyte solution to be maintained at 2.2 ± 0.5 with sulfuric acid and sodium carbonate, deposit the iron-nickel alloy on the surface of the cathode roller, and obtain the iron-nickel alloy foil by peeling; (2) Electrophoresis of the iron-nickel alloy foil using a magnesium oxide electrophoresis solution in an electrophoresis cell: Electrophoresis solution: 5 g / L of magnesium oxide powder (purity 99%, particle size 0.8 μm) and isopropyl alcohol solution, adding 0.5 g / L of dispersant; Electrophoresis conditions: voltage 60 V, current density 10 mA / cm2, time 30 s, temperature 25 °C; Form a uniform magnesium oxide layer; Drying treatment: 10 min at 170 °C to form a magnesium oxide coating on the iron-nickel alloy foil, with a thickness ≤ 1.0 μm; After cleaning with a 10 wt% dilute hydrochloric acid solution, the iron-nickel alloy foil is subjected to electrochemical fluorination treatment: Using the iron-nickel alloy foil as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode, the electrolyte is a 0.10 mol / L ammonium fluoride solution, pH = 4.0; Electrolysis conditions: voltage 3 V, current density 10 mA / cm2, temperature 20 °C, treatment time 10 s to form a fluorinated layer on the magnesium oxide coating, with a thickness at the nanometer level; The obtained iron-nickel alloy foil.

[0101] This comparative example did not go through the heat treatment step compared with Example 5.

[0102] Effect verification: Detect the performance indicators of the iron-nickel alloy foil obtained in Comparative Examples 7 - 10, and the results are shown in Table 2.

[0103] Table 2: Performance indicators of the iron-nickel alloy foil obtained in Comparative Examples 7 - 10

[0104] Note: The above detection methods and instruments are all conventional technologies.

[0105] By comparing the experimental data of Comparative Examples 7 - 10 in the table, the following detailed conclusions can be drawn: Comparative Example 7: There is no magnesium oxide coating on this titanium-nickel alloy foil, and the surface roughness of the S side and the M side are Ra: 0.56 μm / Rz: 1.64 μm and Ra: 0.76 μm / Rz: 1.81 μm respectively, obtaining an iron-nickel alloy foil with a tensile strength of 994 MPa, an elongation of 2.45%, and a curl of 10 mm. The tensile strength is low and the curl is high.

[0106] Comparative Example 8: There is no fluorinated layer on this titanium-nickel alloy foil, and the surface roughness of the S side and the M side are Ra: 0.84 μm / Rz: 1.87 μm and Ra: 0.78 μm / Rz: 2.02 μm respectively, obtaining an iron-nickel alloy foil with a tensile strength of 1287 MPa, an elongation of 2.13%, and a curl of 8 mm. The tensile strength is relatively high and the curl is high.

[0107] Comparative Example 9: There is no magnesium oxide coating and fluorination layer on the titanium-nickel alloy foil. The surface roughness of the S surface and the M surface are Ra: 0.95 μm / Rz: 2.01 μm and Ra: 1.01 μm / Rz: 2.02 μm respectively, and a nickel-iron alloy foil with a tensile strength of 1160 MPa, an elongation of 3.26%, and a curl of 15 mm is obtained. The tensile strength is low and the curl is high.

[0108] Comparative Example 10: The titanium-nickel alloy foil has a magnesium oxide coating and a fluorination layer, but has not been heat-treated. The surface roughness of the S surface and the M surface are Ra: 0.26 μm / Rz: 1.48 μm and Ra: 0.22 μm / Rz: 1.44 μm respectively, and a nickel-iron alloy foil with a tensile strength of 1103 MPa, an elongation of 1.81%, and a curl of 5 mm is obtained. The tensile strength is low and the curl is reduced.

[0109] From the experimental data of Comparative Examples 7-10, the following conclusions can be drawn: The surface roughness of the nickel-iron alloy foil in Comparative Example 7 has increased compared with that in Example 5, the tensile strength has decreased, the elongation has increased, and the curl has increased. It is speculated that the reason is that the magnesium oxide coating can fill some microscopic pits and scratches and other defects on the surface of the alloy foil, thereby reducing the surface roughness. Since the protection of magnesium oxide is lost during the fluorination treatment, the titanium-nickel alloy foil is damaged during the fluorination treatment, resulting in a significant decrease in the tensile strength and a decrease in hardness at the same time, so that the curl increases.

[0110] The surface roughness of the nickel-iron alloy foil in Comparative Example 8 has increased significantly compared with that in Example 5, the tensile strength has decreased slightly, the elongation has increased, and the curl has increased. It is speculated that the reason is that the fluorination layer selectively corrodes the microscopic protrusions on the surface of the titanium-nickel alloy foil, making the surface smoother, thereby reducing the roughness. In addition, the fluorination layer will be evenly deposited on the surface of the alloy foil during the formation process, filling some small pits and gaps, which also helps to reduce the surface roughness. However, the fluorination layer generally has a high hardness and poor toughness, so the elongation will be reduced.

[0111] The surface roughness, elongation, and curl of the nickel-iron alloy foil in Comparative Example 9 have all increased significantly compared with those in Example 5, and the tensile strength has been significantly reduced.

[0112] The surface roughness, elongation, and curl of the iron-nickel alloy foil in Comparative Example 10 are slightly higher than those in Example 5, but the tensile strength is significantly reduced. It is speculated that after heat treatment of the titanium-nickel alloy foil, magnesium oxide coating, and fluorinated layer, the combination of the magnesium oxide coating and fluorinated layer with the titanium-nickel alloy foil becomes closer, the interfacial bonding force is enhanced, enabling the coating to more effectively transfer stress and better share the tensile load borne by the alloy foil, thereby increasing the tensile strength. At the same time, the internal structure of the alloy foil may be optimized during the heat treatment process, such as the grain size becoming more uniform, which also helps to increase the strength. During the heat treatment process, the particles in the magnesium oxide coating and fluorinated layer may agglomerate and recrystallize, making the coating surface denser and flatter. At the same time, some microscopic defects on the surface of the alloy foil may be repaired during the heat treatment process, thereby reducing the roughness.

[0113] In summary, by the solution proposed in the present invention, a magnesium oxide coating and a fluorinated layer are compounded on the iron-nickel alloy foil, which has the advantages of increasing hardness and tensile strength, while also reducing surface roughness and low curl. Therefore, during the production process of the negative electrode material with the active substance coated on the negative electrode current collector, the active substance can be evenly coated for normal production, playing a role in increasing the production volume. The preparation method of the low-curl iron-nickel alloy foil and the composition ratio of the low-curl iron-nickel alloy foil cooperate with each other to jointly achieve an iron-nickel alloy foil material with low curl, high stability, and excellent electrochemical performance.

[0114] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for preparing a low-curling iron-nickel alloy foil applicable to all-solid-state batteries, characterized in that, It includes the following steps: (1) The anode plate and the cathode roller are separately arranged in the electrolytic cell. An electrolyte solution is added to the electrolytic cell, and an electric current is applied to the electrolyte solution to deposit iron-nickel alloy on the surface of the cathode roller, and then the iron-nickel alloy foil is obtained by stripping; Among them, the electrolyte solution includes iron salt solution, nickel salt solution, additives and pure water. The additives are composed of a stress reliever, a pH stabilizer, an Fe reducing agent, a conductive aid and a wetting agent. The electrolyte solution contains: 10-100 g / L of iron salt solution, 5-50 g / L of nickel salt solution, 1.0-3.0 g / L of stress reliever, 15.0-30.0 g / L of pH stabilizer, 0.1-3.0 g / L of Fe reducing agent, 10.0-25.0 g / L of conductive aid and 0.1-1.0 g / L of wetting agent; (2) Electrophoresis is carried out on the iron-nickel alloy foil with magnesium oxide electrophoresis solution in the electrophoresis tank to form a magnesium oxide coating on the iron-nickel alloy foil. After cleaning with an acid solution, the iron-nickel alloy foil is then subjected to electrochemical fluorination treatment to form a fluorinated layer on the magnesium oxide coating; (3) The iron-nickel alloy foil is heat-treated in a heat treatment chamber at a temperature not exceeding 600 °C, and the iron-nickel alloy foil is obtained after cooling.

2. The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries according to claim 1, characterized in that The temperature of the electrolyte solution is 45-65 °C, the applied current density is 6-10 A / dm2, the flow rate of the electrolyte solution is 20-40 m3 / hr, and the pH of the electrolyte solution is adjusted by sulfuric acid and sodium carbonate, pH = 2.0-3.

0.

3. The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries according to claim 1, characterized in that, In the electrolyte solution: The iron salt is any one of ferric sulfate, ferric chloride or ferric carbonate; The nickel salt is any one of nickel sulfate, nickel chloride, nickel hydroxide or nickel carbonate; The stress reliever is any one of sodium saccharin, 1,4-butanediol, diphenylsulfonylimide, sodium allylsulfonate or 2-propylheptanol; The pH stabilizer is any one of boric acid, sodium borate or boron nitride; The Fe reducing agent is any one of glucose, ascorbic acid, sodium gluconate or glycine; The conductive aid is any one of sodium chloride, sodium sulfate, sodium carbonate or sodium citrate; The wetting agent is any one of sodium succinate, sodium dodecylbenzenesulfonate or sodium hydroxyethylsulfonate.

4. The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries according to claim 3, characterized in that In the electrolyte solution: The iron salt is ferric sulfate, the nickel salt is nickel sulfate, the stress reliever is sodium saccharin, the pH stabilizer is boric acid, the Fe reducing agent is ascorbic acid, the conductive aid is sodium chloride, and the wetting agent is sodium succinate. Among them, the content of ferric sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, the content of sodium saccharin is 2.8 g / L, the content of boric acid is 30 g / L, the content of ascorbic acid is 2.9 g / L, the content of sodium chloride is 23.8 g / L, and the content of sodium succinate is 1.0 g / L.

5. The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries according to claim 1, characterized in that During the process of electrophoresis of the iron-nickel alloy foil with magnesium oxide electrophoresis solution in the electrophoresis tank: The magnesium oxide electrophoresis solution includes 5-20 g / L of magnesium oxide powder, 3-8 g / L of isopropyl alcohol solution, 0.3-0.8 g / L of dispersant and pure water; The conditions for electrophoresis are as follows: voltage 40 - 80 V, current density 5 - 15 mA / cm2, time 20 - 40 s, temperature 20 - 30 °C; After electrophoresis, the iron-nickel alloy foil is dried at 165 - 200 °C for 5 - 15 min.

6. The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries according to claim 1, characterized in that The acid solution is a 10 - 12 wt% dilute hydrochloric acid solution or dilute sulfuric acid solution.

7. The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries according to claim 1, wherein, The electrochemical fluorination treatment of the iron-nickel alloy foil is specifically as follows: A three-electrode system is adopted, using the iron-nickel alloy foil as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode. The electrolyte is a 0.10 - 0.15 mol / L ammonium fluoride solution with a pH of 4.0 - 4.2; electrolysis conditions: voltage 2 - 5 V, current density 5 - 15 mA / cm2, temperature 15 - 25 °C, treatment time 10 - 30 s.

8. The preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries according to claim 1, characterized in that, The heat treatment temperature is 400 - 600 °C, the heat treatment time is 5 - 30 min. After cooling, vibration is applied with a vibration frequency of 1000 - 5000 Hz, an amplitude of 0.05 - 0.2 mm, and a vibration time of 5 - 20 min.

9. Low-curling iron-nickel alloy foil applicable to all-solid-state batteries, characterized in that, It is obtained by the preparation method of the low-curling iron-nickel alloy foil applicable to all-solid-state batteries according to any one of claims 1 - 8.

10. The low-curling iron-nickel alloy foil applicable to all-solid-state batteries according to claim 9, wherein The thickness of the iron-nickel alloy foil is 1 μm - 10 μm, and the curl is 2 - 5 mm.

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