Low-curl iron-nickel alloy foil suitable for all-solid-state batteries and preparation method thereof

Abstract

The present invention relates to the technical field of iron-nickel alloy foil preparation, and discloses a low-curl iron-nickel alloy foil suitable for all-solid-state batteries and a preparation method thereof. The preparation method comprises: separately placing an anode plate and a cathode roller in an electrolytic cell; adding an electrolyte solution to the electrolytic cell and applying an electric current to the electrolyte solution; depositing an iron-nickel alloy on the surface of the cathode roller, peeling off the iron-nickel alloy foil, subjecting the iron-nickel alloy foil to electrophoresis in an electrophoresis cell using a magnesium oxide electrophoresis solution to form a magnesium oxide coating on the iron-nickel alloy foil, cleaning the iron-nickel alloy foil with an acid solution, and then subjecting the iron-nickel alloy foil to an electrochemical fluorination treatment to form a fluoride layer on the magnesium oxide coating; and heat-treating the iron-nickel alloy foil in a heat treatment chamber at a temperature not exceeding 600°C, followed by cooling to obtain the iron-nickel alloy foil. The present invention can solve the curling problem and produce high-quality iron-nickel Invar iron-nickel alloy foil suitable for all-solid-state batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of iron-nickel alloy foil preparation, and more particularly 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. Solid electrolytes can be directly filled in this position to achieve 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 being less prone to combustion and explosion, no electrolyte leakage and drying up, 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. Therefore, technicians are investigating the use of iron-nickel Invar alloy foil as an alternative. However, existing Invar alloy foil often warps due to internal stress, making it difficult to achieve uniform coating of the active material on the negative electrode current collector, seriously impacting 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 in that the curling problem can be solved and high-quality iron-nickel invar iron-nickel alloy foil suitable for all-solid-state batteries can be provided.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a low-curl iron-nickel alloy foil suitable for all-solid-state batteries, comprising the following steps:

[0008] (1) The anode plate and the 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 the iron-nickel alloy foil is obtained by peeling;

[0009] The electrolyte solution comprises an iron salt solution, a nickel salt solution, an additive and pure water, wherein the additive consists of a stress relaxant, a pH stabilizer, an Fe reducing agent, a conductive additive and a wetting agent, and the electrolyte solution comprises: 10-100 g / L of an iron salt solution, 5-50 g / L of a nickel salt solution, 1.0-3.0 g / L of a stress relaxant, 15.0-30.0 g / L of a pH stabilizer, 0.1-3.0 g / L of an Fe reducing agent, 10.0-25.0 g / L of a conductive additive and 0.1-1.0 g / L of a wetting agent;

[0010] (2) electrophoretically treating the iron-nickel alloy foil with a magnesium oxide electrophoretic solution in an electrophoretic bath to form a magnesium oxide coating on the iron-nickel alloy foil, and then electrochemically fluorinating the iron-nickel alloy foil after cleaning with an acid solution to form a fluoride layer on the magnesium oxide coating;

[0011] (3) The iron-nickel alloy foil is subjected to heat treatment at a temperature not exceeding 600° C. in a heat treatment chamber, and then cooled to obtain the iron-nickel alloy foil.

[0012] Furthermore, the temperature of the electrolyte solution is 45-65° C., the applied current density is 6-10 A / dm 2 , the flow rate of the electrolyte solution is 20-40 m 3 / hr, and the pH of the electrolyte solution is adjusted by sulfuric acid and sodium carbonate, and the pH is 2.0-3.0.

[0013] Furthermore, in the electrolyte solution:

[0014] The iron salt is any one of ferric sulfate, ferric chloride or ferric carbonate;

[0015] The nickel salt is any one of nickel sulfate, nickel chloride, nickel hydroxide or nickel carbonate;

[0016] The stress reliever is any one of saccharin sodium, 1,4-butanediol, dibenzenesulfonimide, sodium propylenesulfonate or 2-propylheptanol;

[0017] The pH stabilizer is any one of boric acid, sodium borate or boron nitride;

[0018] The Fe reducing agent is any one of glucose, ascorbic acid, sodium gluconate or glycine;

[0019] The conductive additive is any one of sodium chloride, sodium sulfate, sodium carbonate or sodium citrate;

[0020] The wetting agent is any one of sodium succinate, sodium dodecylbenzenesulfonate or sodium isethionate.

[0021] Furthermore, in the electrolyte solution:

[0022] The iron salt is ferric sulfate, the nickel salt is nickel sulfate, the stress relaxer is saccharin sodium, the pH stabilizer is boric acid, the Fe reducing agent is ascorbic acid, the conductive additive is sodium chloride, and the wetting agent is sodium succinate. The iron sulfate content is 43.2 g / L, the nickel sulfate content is 18.6 g / L, the saccharin sodium 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.

[0023] Furthermore, during the electrophoresis of the iron-nickel alloy foil using magnesium oxide electrophoresis solution in the electrophoresis pool:

[0024] The magnesium oxide electrophoresis solution comprises 5-20 g / L magnesium oxide powder, 3-8 g / L isopropyl alcohol solution, 0.3-0.8 g / L dispersant and pure water;

[0025] The electrophoresis conditions are as follows: voltage 40-80 V, current density 5-15 mA / cm2, time 20-40 s, temperature 20-30°C;

[0026] After electrophoresis, the iron-nickel alloy foil is dried at 165-200° C. for 5-15 minutes.

[0027] Furthermore, the acid solution is a 10-12 wt% dilute hydrochloric acid solution or a dilute sulfuric acid solution.

[0028] Furthermore, the electrochemical fluorination treatment of the iron-nickel alloy foil is specifically performed as follows:

[0029] A three-electrode system was used, with iron-nickel alloy foil as the working electrode, Ag / AgCl as the reference electrode, and platinum sheet as the counter electrode. The electrolyte was 0.10-0.15 mol / L ammonium fluoride solution, pH = 4.0-4.2; electrolysis conditions were: voltage 2-5 V, current density 5-15 mA / cm2, temperature 15-25°C, and treatment time 10-30 s.

[0030] Furthermore, the heat treatment temperature is 400-600° C., the heat treatment time is 5-30 min, and vibration is applied after cooling, with a vibration frequency of 1000-5000 Hz, an amplitude of 0.05-0.2 mm, and a vibration time of 5-20 min.

[0031] In a second aspect, the present invention provides a low-curl iron-nickel alloy foil suitable for all-solid-state batteries, which is prepared by the above-mentioned method for preparing the low-curl iron-nickel alloy foil suitable for all-solid-state batteries.

[0032] Furthermore, the iron-nickel alloy foil has a thickness of 1 μm-10 μm and a curl of 2-5 mm.

[0033] The present invention has the following beneficial effects: The method for preparing low-curl iron-nickel alloy foil suitable for all-solid-state batteries successfully solves the existing problem of curling of nickel-iron-nickel alloy foil due to internal stress by adding a stress relaxant, pH stabilizer, Fe reducing agent, conductive additive, and wetting agent to the electrolyte. The prepared iron-nickel alloy foil has a thickness of 3-10 μm and excellent surface quality, with the S-side and M-side roughness controlled to Ra: less than 0.30 μm and Rz: less than 1.50 μm, respectively.

[0034] In the method of the present invention, the internal stress of the iron-nickel alloy foil is effectively reduced through the synergistic effect of additive adjustment, electrophoretic magnesium oxide coating, fluoride layer and heat treatment process. Both the magnesium oxide and fluoride layers 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 the corrosive medium and the alloy foil, thereby slowing down the corrosion rate of the alloy foil and increasing its service life. It can also improve the wear resistance of the surface of the iron-nickel alloy foil and further reduce the curling. After heat treatment, the iron-nickel alloy foil has a tensile strength of 1100-1400MPa and an elongation of 1.50%-3.50% at room temperature, and the curling does not exceed 5mm. Heat treatment makes the metal structure finer and effectively suppresses the curling phenomenon, solving the corrosion problem that may occur during use as a negative electrode current collector material for secondary batteries, while ensuring that the active material can be evenly coated, thereby ensuring high yield and high quality of the iron-nickel alloy foil.

[0035] The iron-nickel alloy foil produced by this process contains no copper, thus avoiding the corrosion problem of copper 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. Sulfide-based all-solid-state batteries produced using this process have superior specifications and stability compared to existing lithium-ion batteries, representing an innovative product that addresses key challenges in the future secondary battery industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Flow chart of the synthesis of iron-nickel alloy foil using electrolyte solution. DETAILED DESCRIPTION

[0037] The subject matter described herein will now be discussed with reference to example embodiments. It should be understood that these embodiments are discussed solely to enable those skilled in the art to better understand and implement the subject matter described herein, and that the functions and arrangements of the elements discussed may be varied without departing from the scope of this specification. Various examples may omit, substitute, or add various processes or components as needed. Furthermore, features described in some examples may be combined in other examples.

[0038] At least one embodiment of the present invention discloses a low curl iron-nickel alloy foil suitable for all-solid-state batteries and a method for preparing the same, comprising:

[0039] A method for preparing a low-curl iron-nickel alloy foil suitable for all-solid-state batteries is as follows:

[0040] (1) The anode plate and the cathode roller are separately placed 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. The iron-nickel alloy foil is then obtained by peeling. The iron content of 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.

[0041] See Figure 1 The invention involves preparing an iron-nickel alloy foil through an electrolytic deposition process and adding additives in specific proportions to effectively control the alloy's microstructure and surface morphology. The precise proportions of additives in the electrolyte solution are a key component of the invention, significantly reducing the curling of the iron-nickel alloy foil and improving its suitability for use in battery manufacturing.

[0042] (2) Electrophoresis of the iron-nickel alloy foil is performed in an electrophoretic bath using a magnesium oxide electrophoretic solution to form a magnesium oxide coating on the iron-nickel alloy foil. After cleaning with an acid solution, the iron-nickel alloy foil is electrochemically fluorinated to form a fluoride layer on the magnesium oxide coating.

[0043] A magnesium oxide coating is obtained on the iron-nickel alloy foil through an electrophoretic process, and then the iron-nickel alloy foil is fluorinated through electrochemistry. The magnesium oxide coating and the fluorinated layer have good chemical stability and corrosion resistance, so that a dense protective film is formed on the surface of the iron-nickel alloy foil, isolating the contact between the corrosive medium and the alloy foil, thereby slowing down the corrosion rate of the alloy foil, increasing its service life, improving the wear resistance of the iron-nickel alloy foil surface, and further reducing the curling.

[0044] (3) The iron-nickel alloy foil is subjected to heat treatment at a temperature not exceeding 600° C. in a heat treatment chamber, and then cooled to obtain the iron-nickel alloy foil.

[0045] 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, with a curl of no more than 5 mm. Heat treatment refines the metal structure and effectively suppresses curling, resolving potential corrosion issues during use as a negative electrode current collector material for secondary batteries. It also ensures uniform coating of the active material, thus guaranteeing high production and high quality of the iron-nickel alloy foil.

[0046] In another preferred embodiment of the present invention, the anode plate is composed of Ti+Ir, and the cathode roller is composed of Ti, wherein the cathode roller uses Ti. On the one hand, it has good corrosion resistance: titanium has very good corrosion resistance, is not easily corroded by electrolyte, can be used for a long time, and extends the service life; on the other hand, it has good conductivity: titanium has good conductivity, and as an electrode in the electrodeposition manufacturing process, it can efficiently transmit current.

[0047] The Ti+Ir used in the anode plate, on the one hand, has good corrosion resistance: like the cathode roller, titanium has very good corrosion resistance, will not be corroded by the electrolyte, and 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 plate is subjected to high voltage or reacts with the electrolyte, it has strong durability; at the same time, the Ti+Ir used has a good catalytic effect: iridium can promote the electrochemical reaction and can efficiently assist the electrochemical reaction in the electrolyte.

[0048] For these reasons, these materials play a crucial role in their interaction with the electrolyte solution, exhibiting exceptional corrosion resistance and electrochemical stability, making them stable and efficient electrode materials during the manufacturing process. Given the extreme chemical environment of the electrolyte, the durability and electrochemical properties provided by these materials are crucial for ensuring manufacturing efficiency and quality.

[0049] The electrolyte solution includes an iron salt solution, a nickel salt solution, additives, and pure water. The additives consist of a stress relaxant, a pH stabilizer, an iron reducing agent, a conductive additive, and a wetting agent. The electrolyte solution includes: 10-100g / L of iron salt solution, 5-50g / L of nickel salt solution, 1.0-3.0g / L of stress relaxant, 15.0-30.0g / L of pH stabilizer, 0.1-3.0g / L of iron reducing agent, 10.0-25.0g / L of conductive additive, and 0.1-1.0g / L of wetting agent. The iron and nickel salts have different effects on the alloy's deposition rate, grain size, and internal stress. By selecting the appropriate metal salt type, the alloy's microstructure and mechanical properties can be optimized.

[0050] Among them, the iron salt is any one of iron sulfate, iron chloride or iron carbonate, the nickel salt is any one of nickel sulfate, nickel chloride, nickel hydroxide or nickel carbonate, the stress relaxer is any one of saccharin sodium, 1,4-butanediol, diphenylsulfonimide, sodium propylene sulfonate 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 additive 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 hydroxyethyl sulfonate.

[0051] The pH of the electrolyte solution is adjusted using sulfuric acid and sodium carbonate, maintaining a pH range of 2.0-3.0. If the pH is below the optimal range of 2.0-3.0, sodium carbonate is used to raise the pH to the appropriate range. If the pH is above the optimal range, sulfuric acid is used to lower the pH to the appropriate range. The electrolyte solution temperature is 45-65°C, the applied current density is 6-10A / dm², and the electrolyte solution flow rate is 20-40m³ / hr. Optimizing the design of electrolyte solution temperature, current density, flow rate, and pH ensures a stable electrodeposition process and produces a uniform and dense alloy deposit. Precise pH control is crucial for preventing hydrogen evolution and metal hydroxide precipitation, thereby improving current efficiency and deposition quality.

[0052] In another preferred embodiment of the present invention, the electrophoresis of the iron-nickel alloy foil is performed using a magnesium oxide electrophoresis solution, specifically:

[0053] Place the iron-nickel alloy foil in an electrophoresis bath, and the magnesium oxide electrophoresis solution is composed of 5-20 g / L magnesium oxide powder, 3-8 g / L isopropyl alcohol solution, 0.3-0.8 g / L dispersant, and pure water.

[0054] Electrophoresis conditions: voltage 40-80 V, current density 5-15 mA / cm2, time 20-40 s, temperature 20-30 ° C;

[0055] After electrophoresis, the iron-nickel alloy foil is dried at 165-200°C for 5-15 minutes.

[0056] The iron-nickel alloy foil is subjected to electrochemical fluorination treatment, specifically:

[0057] A three-electrode system was used, with iron-nickel alloy foil as the working electrode, Ag / AgCl as the reference electrode, and platinum sheet as the counter electrode. The electrolyte was 0.10-0.15 mol / L ammonium fluoride solution, pH = 4.0-4.2; electrolysis conditions were: voltage 2-5 V, current density 5-15 mA / cm2, temperature 15-25°C, and treatment time 10-30 s.

[0058] In another preferred embodiment of the present invention, heat treatment is performed in a heat treatment chamber at a temperature of 400-600°C for a time of 5-30 minutes. After cooling, vibration is applied at a frequency of 1000-5000 Hz, an amplitude of 0.05-0.2 mm, and a time of 5-20 minutes. During the heat treatment process, if the temperature and time are lower than the above values, the internal stress may not be reduced. If the temperature and time 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 thermal energy, releases the internal stress generated during the deposition process, promotes grain growth and recrystallization, optimizes the microstructure of the alloy, and improves the mechanical properties and stability of the alloy, thereby effectively reducing the curling phenomenon of the iron-nickel alloy foil.

[0059] In summary, this invention successfully produces a low-curl iron-nickel alloy foil suitable for all-solid-state batteries by optimizing electrolytic deposition process parameters and additive formulations, synthesizing a magnesium oxide coating and a fluoride layer on the foil surface, and combining this with an appropriate heat treatment process. This iron-nickel alloy foil exhibits excellent mechanical properties, surface morphology, and dimensional stability, significantly improving the manufacturing efficiency and performance stability of all-solid-state batteries and possessing significant practical value.

[0060] The present application is further described in detail below in conjunction with the embodiments and comparative examples. It is necessary to point out here that the following specific embodiments are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technicians in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0061] 1. Description

[0062] 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 are commercially available products unless otherwise specified. The instruments used are conventional instruments known to those skilled in the art unless otherwise specified.

[0063] 2. Methods

[0064] 2.1 Effect of electrolyte solution additive adjustment on Fe-Ni alloy foil

[0065] Example 1

[0066] (1) The anode plate and the cathode roller are separately placed in an electrolytic cell, an electrolyte solution is added to the electrolytic cell, and a current is applied to the electrolyte solution. The electrolyte temperature is 62±2°C, the current density is 8A / dm2, and the electrolyte solution flow rate is 30m3 / hr. The pH value of the electrolyte solution is adjusted to 2.2±0.5 with sulfuric acid and sodium carbonate. An iron-nickel alloy is deposited on the surface of the cathode roller, and an iron-nickel alloy foil is obtained by peeling.

[0067] (2) Electrophoresis of the iron-nickel alloy foil using a magnesium oxide electrophoresis solution in an electrophoresis pool: electrophoresis solution: 5 g / L magnesium oxide powder (purity 99%, particle size range 0.5-1 μm) and isopropyl alcohol solution, with the addition of 0.5 g / L 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: 170 ° C for 10 min to form a magnesium oxide coating on the iron-nickel alloy foil with a thickness of ≤1.0 μm;

[0068] After cleaning with a 10wt% dilute hydrochloric acid solution, the iron-nickel alloy foil was electrochemically fluorinated 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 was a 0.10mol / L ammonium fluoride solution with a pH of 4.0. The electrolysis conditions were: voltage 3V, current density 10mA / cm2, temperature 20°C, and treatment time 10s, to form a fluorinated layer on the magnesium oxide coating with a thickness of nanometers.

[0069] (3) The iron-nickel alloy foil was heat treated at 400°C for 30 minutes in a heat treatment chamber. After cooling, it was placed on a vibration table and vibrated at a frequency of 1000 Hz, an amplitude of 0.05 mm, and a vibration time of 10 minutes. After cooling, the iron-nickel alloy foil was obtained.

[0070] In the electrolyte solution of this embodiment, the iron sulfate content is 43.2 g / L, the nickel sulfate content is 18.6 g / L, the saccharin sodium content is 1.1 g / L, the boric acid content is 15.5 g / L, the ascorbic acid content is 0.1 g / L, the sodium chloride content is 11.6 g / L, and the sodium succinate content is 0.2 g / L.

[0071] Example 2

[0072] This embodiment is applicable to a method for preparing a low-curl iron-nickel alloy foil for all-solid-state batteries. Except for the different addition amounts, the preparation method of the iron-nickel alloy foil is the same as that of Example 1.

[0073] In the electrolyte solution of this embodiment, the iron sulfate content is 43.2 g / L, the nickel sulfate content is 18.6 g / L, the saccharin sodium content is 1.6 g / L, the boric acid content is 19 g / L, the ascorbic acid content is 0.7 g / L, the sodium chloride content is 14.4 g / L, and the sodium succinate content is 0.4 g / L.

[0074] Example 3

[0075] This embodiment is applicable to a method for preparing a low-curl iron-nickel alloy foil for all-solid-state batteries. Except for the different addition amounts, the preparation method of the iron-nickel alloy foil is the same as that of Example 1.

[0076] In the electrolyte solution of this embodiment, the iron sulfate content is 43.2 g / L, the nickel sulfate content is 18.6 g / L, the saccharin sodium content is 2.0 g / L, the boric acid content is 22.5 g / L, the ascorbic acid content is 1.5 g / L, the sodium chloride content is 17.5 g / L, and the sodium succinate content is 0.6 g / L.

[0077] Example 4

[0078] This embodiment is applicable to a method for preparing a low-curl iron-nickel alloy foil for all-solid-state batteries. Except for the different addition amounts, the preparation method of the iron-nickel alloy foil is the same as that of Example 1.

[0079] In the electrolyte solution of this embodiment, the iron sulfate content is 43.2 g / L, the nickel sulfate content is 18.6 g / L, the saccharin sodium content is 2.5 g / L, the boric acid content is 26 g / L, the ascorbic acid content is 2.1 g / L, the sodium chloride content is 20.7 g / L, and the sodium succinate content is 0.8 g / L.

[0080] Example 5

[0081] This embodiment is applicable to a method for preparing a low-curl iron-nickel alloy foil for all-solid-state batteries. Except for the different addition amounts, the preparation method of the iron-nickel alloy foil is the same as that of Example 1.

[0082] In the electrolyte solution of this embodiment, the iron sulfate content is 43.2 g / L, the nickel sulfate content is 18.6 g / L, the saccharin sodium 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.

[0083] Example 6

[0084] A method for preparing low-curl iron-nickel alloy foil suitable for all-solid-state batteries, wherein the electrolyte temperature is 45±2°C, the current density is 10A / dm2, the electrolyte solution flow rate is 30m3 / 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.

[0085] In the electrolyte solution of this embodiment, the ferric chloride content is 58 g / L, the nickel chloride content is 33.6 g / L, the diphenylsulfonimide 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.

[0086] The rest is the same as in Example 1.

[0087] Example 7

[0088] This embodiment is applicable to the preparation method of low-curl iron-nickel alloy foil for all-solid-state batteries. The electrolyte temperature is 62±2°C, the current density is 6A / dm2, the electrolyte solution flow rate is 30m3 / hr, and the pH value of the electrolyte solution is adjusted with sulfuric acid and sodium carbonate to maintain at 2.2±0.5.

[0089] In the electrolyte solution of this embodiment, the iron 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.

[0090] The rest is the same as in Example 1.

[0091] Example 8

[0092] A method for preparing low-curl iron-nickel alloy foil suitable for all-solid-state batteries, wherein the electrolyte temperature is 50±2°C, the current density is 8A / dm2, the electrolyte solution flow rate is 40m3 / hr, and the pH value of the electrolyte solution is adjusted with sulfuric acid and sodium carbonate to maintain within the range of 2.5±0.5;

[0093] In the electrolyte solution of this embodiment, the iron carbonate content is 61.7 g / L, the nickel hydroxide content is 6.1 g / L, the sodium propylene sulfonate 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 hydroxyethyl sulfonate content is 1 g / L.

[0094] The rest is the same as in Example 1.

[0095] Comparative Example 1

[0096] This comparative example is applicable to a method for preparing a low-curl iron-nickel alloy foil for all-solid-state batteries. Except for the different addition amounts, the preparation method of the iron-nickel alloy foil is the same as that of Example 1.

[0097] In the electrolyte solution of this comparative example, the content of iron sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, the content of boric acid is 15.4 g / L, the content of ascorbic acid is 0.1 g / L, the content of sodium chloride is 11.7 g / L, and the content of sodium succinate is 1.0 g / L.

[0098] Comparative Example 2

[0099] This comparative example is applicable to a method for preparing a low-curl iron-nickel alloy foil for all-solid-state batteries. Except for the different addition amounts, the preparation method of the iron-nickel alloy foil is the same as that of Example 1.

[0100] In the electrolyte solution of this comparative example, the content of iron sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 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 0.5 g / L.

[0101] Comparative Example 3

[0102] This comparative example is applicable to a method for preparing a low-curl iron-nickel alloy foil for all-solid-state batteries. Except for the different addition amounts, the preparation method of the iron-nickel alloy foil is the same as that of Example 1.

[0103] In the electrolyte solution of this comparative example, the content of iron sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, the content of saccharin sodium is 2.0 g / L, the content of boric acid is 22.7 g / L, the content of ascorbic acid is 1.6 g / L, and the content of sodium chloride is 17.6 g / L.

[0104] Comparative Example 4

[0105] This comparative example is applicable to a method for preparing a low-curl iron-nickel alloy foil for all-solid-state batteries. Except for the different addition amounts, the preparation method of the iron-nickel alloy foil is the same as that of Example 1.

[0106] In the electrolyte solution of this comparative example, the content of iron sulfate is 43.2 g / L, the content of nickel sulfate is 18.6 g / L, the content of saccharin sodium is 0.5 g / L, the content of boric acid is 7.8 g / L, the content of ascorbic acid is 0.05 g / L, the content of sodium chloride is 5.0 g / L, and the content of sodium succinate is 0.05 g / L.

[0107] Comparative Example 5

[0108] This comparative example is applicable to a method for preparing an iron-nickel alloy foil for an all-solid-state battery. Except for the different additive composition, other preparation conditions are the same as those in Example 8.

[0109] The electrolyte solution in this comparative example contained 61.7 g / L of iron carbonate, 6.1 g / L of nickel hydroxide, 30 g / L of boron nitride, 3 g / L of sodium gluconate, and 25 g / L of sodium carbonate. This comparative example omitted the addition of sodium propylene sulfonate as a stress relaxant and sodium isethionate as a wetting agent, resulting in a curl exceeding 5 mm and a significant reduction in tensile strength.

[0110] Comparative Example 6

[0111] This comparative example is applicable to the preparation method of iron-nickel alloy foil for all-solid-state batteries. Except for the different additive contents, other preparation conditions are the same as those in Example 8.

[0112] The electrolyte solution in this comparative example contained 61.7 g / L of iron carbonate, 6.1 g / L of nickel hydroxide, 0.5 g / L of sodium propylene sulfonate, 10 g / L of boron nitride, 0.05 g / L of sodium gluconate, 5 g / L of sodium carbonate, and 0.05 g / L of sodium isethionate. The additive contents in this comparative example were all below the standard values, resulting in increased surface roughness and a curl exceeding 7 mm in the resulting iron-nickel alloy foil.

[0113] Effect verification: The performance indicators of the iron-nickel alloy foils obtained in Examples 1-8 and Comparative Examples 1-5 were tested, and the results are shown in Table 1.

[0114] Table 1: Performance indicators of the iron-nickel alloy foils obtained in Examples 1-8 and Comparative Examples 1-6

[0115]

[0116] Note: The above detection methods and instruments are conventional techniques.

[0117] By comparing the experimental data of Examples 1-8 and Comparative Examples 1-6 in the table, the following detailed conclusions can be drawn:

[0118] Example 1: Using a current density of 8 A / dm², an iron-nickel alloy foil with a tensile strength of 1155 MPa, an elongation of 3.20%, and a curl of 5 mm was obtained with S-plane roughnesses of 0.29 μm / Rz of 1.45 μm and M-plane roughnesses of 0.30 μm / Rz of 1.48 μm, respectively. This example demonstrates that the method of the present invention can produce low-curl iron-nickel alloy foil with excellent surface quality and mechanical properties.

[0119] Example 2: Using a current density of 8 A / dm², the S-plane roughnesses were Ra: 0.26 μm / Rz: 1.41 μm, and the M-plane roughnesses were Ra: 0.27 μm / Rz: 1.43 μm, respectively. An iron-nickel alloy foil with a tensile strength of 1219 MPa, an elongation of 2.81%, and a curl of 4 mm was obtained. Compared to Example 1, the tensile strength was improved and the curl was reduced.

[0120] Example 3: Using a current density of 8 A / dm², the S- and M-surface roughnesses were Ra: 0.25 μm / Rz: 1.39 μm and Ra: 0.25 μm / Rz: 1.41 μm, respectively. An iron-nickel alloy foil with a tensile strength of 1282 MPa, an elongation of 2.36%, and a curl of 3 mm was obtained. The surface roughness was further reduced, the tensile strength continued to increase, and the curl was further improved.

[0121] Example 4: Using a current density of 8 A / dm², the S- and M-surface roughnesses were Ra: 0.20 μm / Rz: 1.33 μm and Ra: 0.22 μm / Rz: 1.37 μm, respectively. An iron-nickel alloy foil with a tensile strength of 1344 MPa, an elongation of 1.98%, and a curl of 3 mm was obtained. The surface quality was significantly improved, and the tensile strength reached a high level.

[0122] Example 5: Using a current density of 8 A / dm², the S- and M-surface roughnesses were Ra: 0.18 μm / Rz: 1.31 μm and Ra: 0.19 μm / Rz: 1.32 μm, respectively. An iron-nickel alloy foil with a tensile strength of 1381 MPa, an elongation of 1.56%, and a curl of 2 mm was obtained. Of all the examples, this foil achieved the best surface quality, the highest tensile strength, and the lowest curl, but exhibited a slight decrease in elongation.

[0123] Example 6: Using a current density of 10 A / dm², the S- and M-surface roughnesses were Ra: 0.27 μm / Rz: 1.38 μm and Ra: 0.29 μm / Rz: 1.43 μm, respectively. An iron-nickel alloy foil having a tensile strength of 1210 MPa, an elongation of 3.2%, and a curl of 3 mm was obtained. This demonstrates that the method of the present invention can still achieve excellent performance at higher current densities.

[0124] Example 7: Using a current density of 6 A / dm², the roughnesses of the S- and M-surfaces were Ra: 0.26 μm / Rz: 1.41 μm and Ra: 0.28 μm / Rz: 1.42 μm, respectively. An iron-nickel alloy foil having a tensile strength of 1340 MPa, an elongation of 3.0%, and a curl of 3 mm was obtained. This demonstrates that the method of the present invention is also effective at lower current densities.

[0125] Example 8: Using a current density of 8 A / dm², the S-plane roughness was Ra: 0.26 μm / Rz: 1.39 μm, and the M-plane roughness was Ra: 0.29 μm / Rz: 1.44 μm. An iron-nickel alloy foil with a tensile strength of 1298 MPa, an elongation of 3.1%, and a curl of 2 mm was obtained. This demonstrates the stability and repeatability of the method of the present invention.

[0126] Comparative Example 1: Using a current density of 8 A / dm², the S- and M-surface roughnesses were Ra:1.09 μm / Rz:2.22 μm and Ra:1.30 μm / Rz:2.29 μm, respectively. An iron-nickel alloy foil with a tensile strength of 691 MPa, an elongation of 4.66%, and a curl of 20 mm was obtained. This surface roughness far exceeded the standard, significantly reduced tensile strength, and exhibited severe curling, making it unsuitable for use as a current collector in all-solid-state batteries.

[0127] Comparative Example 2: Using a current density of 8 A / dm², the S- and M-surface roughnesses were Ra: 0.98 μm / Rz: 2.09 μm and Ra: 1.08 μm / Rz: 2.11 μm, respectively. The resulting iron-nickel alloy foil had a tensile strength of 843 MPa, an elongation of 4.01%, and a curl of 17 mm. While this performance was slightly better than that of Comparative Example 1, it was still significantly lower than that of the example.

[0128] Comparative Example 3: Using a current density of 8 A / dm², the S- and M-surface roughnesses were Ra: 0.78 μm / Rz: 1.97 μm and Ra: 0.99 μm / Rz: 2.04 μm, respectively. The resulting iron-nickel alloy foil had a tensile strength of 983 MPa, an elongation of 3.98%, and a curl of 10 mm. While the tensile strength improved, the curl was still excessive.

[0129] Comparative Example 4: Using a current density of 8 A / dm², the S- and M-surface roughnesses were Ra: 0.64 μm / Rz: 1.81 μm and Ra: 0.84 μm / Rz: 1.85 μm, respectively. The resulting iron-nickel alloy foil had a tensile strength of 778 MPa, an elongation of 4.31%, and a curl of 16 mm. However, the tensile strength was lower than that of Comparative Example 3, and the curl was still severe.

[0130] Comparative Example 5: Using a current density of 8 A / dm², the S- and M-surface roughnesses were Ra: 0.70 μm / Rz: 1.85 μm and Ra: 0.75 μm / Rz: 1.90 μm, respectively. An iron-nickel alloy foil with a tensile strength of 720 MPa, an elongation of 4.25%, and a curl of 15 mm was obtained. The low tensile strength and high curl did not meet the requirements.

[0131] Comparative Example 6: Using a current density of 8 A / dm², the S- and M-surface roughnesses were Ra: 0.45 μm / Rz: 1.65 μm and Ra: 0.48 μm / Rz: 1.70 μm, respectively. An iron-nickel alloy foil with a tensile strength of 1050 MPa, an elongation of 3.85%, and a curl of 8 mm was obtained. While this performance is close, it still does not meet the low curl requirement.

[0132] Comprehensive analysis shows that the method of the present invention successfully prepares iron-nickel alloy foil with low surface roughness (Ra<0.30μm, Rz<1.50μm), high tensile strength (1155-1381MPa), and small curl (≤5mm) by precisely controlling the type and amount of additives. These properties are crucial to the performance of the negative electrode collector of all-solid-state batteries. In particular, the low curling property can ensure uniform coating of the active material and improve battery production efficiency and quality.

[0133] By comparing the experimental data of Examples 1-8 with Comparative Examples 1-6, the following conclusions can be drawn:

[0134] In Examples 1-8, the tensile strength of the iron-nickel alloy foils were all in the range of 1155-1381 MPa, which was significantly higher than the 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.

[0135] The elongation of Examples 1-8 is between 1.56% and 3.20%, which is lower than 3.74% to 4.66% of Comparative Examples 1-6, indicating that the iron-nickel alloy foil prepared by the method of the present invention has appropriate ductility while maintaining high strength properties.

[0136] The most significant difference is the degree of curling. Examples 1-8 all have curling within the range of 2-5 mm, while Comparative Examples 1-6 have curling between 7-20 mm. This demonstrates that the iron-nickel alloy foil prepared by the method of the present invention has a significantly low curling characteristic, which is crucial for the manufacturing process of all-solid-state batteries.

[0137] In Comparative Examples 1-6, since the type or amount of additives does not meet the requirements of the present invention, the performance of the iron-nickel alloy foil is reduced, especially the curling is significantly increased, which affects the uniform coating of the active material in the subsequent battery manufacturing process.

[0138] Examples 6-8 show that under different current density conditions (6-10 A / dm2), as long as the appropriate additive ratio is maintained, iron-nickel alloy foil with low curl can be obtained, proving that the method of the present invention has good process adaptability.

[0139] In summary, the type and amount of additives used in the present invention are crucial and form the core of the invention. Only within these ranges can the excellent properties of the resulting iron-nickel alloy foil be guaranteed. As shown in Tables 1 and 2, the iron-nickel alloy foils prepared by adding the five additives in Examples 1-8 exhibited tensile strengths of 1100-1400 MPa at room temperature and elongations of 1.5-3.5% at room temperature after heat treatment. Furthermore, curling was confirmed to be below 5 mm.

[0140] 2.2 Effects of coating adjustment and heat treatment on Fe-Ni alloy foil

[0141] Comparative Example 7

[0142] (1) An anode plate and a cathode roller are separately placed in an electrolytic cell, an electrolyte solution is added to the electrolytic cell, and an electric current is applied to the electrolyte solution. The electrolyte temperature is 62±2°C, the current density is 8A / dm2, the electrolyte solution flow rate is 30m3 / hr, and the pH value of the electrolyte solution is adjusted to 2.2±0.5 with sulfuric acid and sodium carbonate. An iron-nickel alloy is deposited on the surface of the cathode roller, and an iron-nickel alloy foil is obtained by peeling. The electrolyte solution contains 43.2 g / L of iron sulfate, 18.6 g / L of nickel sulfate, 2.8 g / L of sodium saccharin, 30 g / L of boric acid, 2.9 g / L of ascorbic acid, 23.8 g / L of sodium chloride, and 1.0 g / L of sodium succinate.

[0143] (2) After cleaning the iron-nickel alloy foil with a 10 wt% dilute hydrochloric acid solution, the iron-nickel alloy foil was subjected to an electrochemical fluorination treatment: the iron-nickel alloy foil was used as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode. The electrolyte was a 0.10 mol / L ammonium fluoride solution with a pH of 4.0. The electrolysis conditions were: voltage 3 V, current density 10 mA / cm2, temperature 20 °C, and treatment time 10 s. A fluorinated layer was formed with a thickness of nanometers.

[0144] (3) The iron-nickel alloy foil was heat treated at 400°C for 30 minutes in a heat treatment chamber. After cooling, it was placed on a vibration table and vibrated at a frequency of 1000 Hz, an amplitude of 0.05 mm, and a vibration time of 10 minutes. After cooling, the iron-nickel alloy foil was obtained.

[0145] This comparative example, compared to Example 5, does not include a magnesium oxide coating.

[0146] Comparative Example 8

[0147] (1) An anode plate and a cathode roller are separately placed in an electrolytic cell, an electrolyte solution is added to the electrolytic cell, and an electric current is applied to the electrolyte solution. The electrolyte temperature is 62±2°C, the current density is 8A / dm2, the electrolyte solution flow rate is 30m3 / hr, and the pH value of the electrolyte solution is adjusted to 2.2±0.5 with sulfuric acid and sodium carbonate. An iron-nickel alloy is deposited on the surface of the cathode roller, and an iron-nickel alloy foil is obtained by peeling. The electrolyte solution contains 43.2 g / L of iron sulfate, 18.6 g / L of nickel sulfate, 2.8 g / L of sodium saccharin, 30 g / L of boric acid, 2.9 g / L of ascorbic acid, 23.8 g / L of sodium chloride, and 1.0 g / L of sodium succinate.

[0148] (2) Electrophoresis of the iron-nickel alloy foil using magnesium oxide electrophoresis solution in an electrophoresis pool: electrophoresis solution: magnesium oxide powder (purity 99%, particle size 0.8 μm) 5 g / L and isopropyl alcohol solution, with the addition of dispersant 0.5 g / L; electrophoresis conditions: voltage 60 V, current density 10 mA / cm2, time 30 s, temperature 25 ° C; forming a uniform magnesium oxide layer; drying treatment: 170 ° C for 10 min to form a magnesium oxide coating on the iron-nickel alloy foil with a thickness of ≤ 1.0 μm;

[0149] (3) The iron-nickel alloy foil was heat treated at 400°C for 30 minutes in a heat treatment chamber. After cooling, it was placed on a vibration table and vibrated at a frequency of 1000 Hz, an amplitude of 0.05 mm, and a vibration time of 10 minutes. After cooling, the iron-nickel alloy foil was obtained.

[0150] This comparative example, compared to Example 5, does not include a fluorinated layer.

[0151] Comparative Example 9

[0152] (1) An anode plate and a cathode roller are separately placed in an electrolytic cell, an electrolyte solution is added to the electrolytic cell, and an electric current is applied to the electrolyte solution. The electrolyte temperature is 62±2°C, the current density is 8A / dm2, the electrolyte solution flow rate is 30m3 / hr, and the pH value of the electrolyte solution is adjusted to 2.2±0.5 with sulfuric acid and sodium carbonate. An iron-nickel alloy is deposited on the surface of the cathode roller, and an iron-nickel alloy foil is obtained by peeling. The electrolyte solution contains 43.2 g / L of iron sulfate, 18.6 g / L of nickel sulfate, 2.8 g / L of sodium saccharin, 30 g / L of boric acid, 2.9 g / L of ascorbic acid, 23.8 g / L of sodium chloride, and 1.0 g / L of sodium succinate.

[0153] (2) The iron-nickel alloy foil was heat treated at 400°C for 30 minutes in a heat treatment chamber. After cooling, it was placed on a vibration table and vibrated at a frequency of 1000 Hz, an amplitude of 0.05 mm, and a vibration time of 10 minutes. After cooling, the iron-nickel alloy foil was obtained.

[0154] This comparative example does not include the magnesium oxide coating and the fluorinated layer as in Example 5.

[0155] Comparative Example 10

[0156] (1) The anode plate and the cathode roller are separately placed in an electrolytic cell, an electrolyte solution is added to the electrolytic cell, and a current is applied to the electrolyte solution. The electrolyte temperature is 62±2°C, the current density is 8A / dm2, and the electrolyte solution flow rate is 30m3 / hr. The pH value of the electrolyte solution is adjusted to 2.2±0.5 with sulfuric acid and sodium carbonate. An iron-nickel alloy is deposited on the surface of the cathode roller, and an iron-nickel alloy foil is obtained by peeling.

[0157] (2) Electrophoresis of the iron-nickel alloy foil using magnesium oxide electrophoresis solution in an electrophoresis pool: electrophoresis solution: magnesium oxide powder (purity 99%, particle size 0.8 μm) 5 g / L and isopropyl alcohol solution, with the addition of dispersant 0.5 g / L; electrophoresis conditions: voltage 60 V, current density 10 mA / cm2, time 30 s, temperature 25 ° C; forming a uniform magnesium oxide layer; drying treatment: 170 ° C for 10 min to form a magnesium oxide coating on the iron-nickel alloy foil with a thickness of ≤ 1.0 μm;

[0158] After cleaning with a 10wt% dilute hydrochloric acid solution, the iron-nickel alloy foil was subjected to an electrochemical fluorination treatment: the iron-nickel alloy foil was used as a working electrode, Ag / AgCl was used as a reference electrode, and a platinum sheet was used as a counter electrode. The electrolyte was a 0.10mol / L ammonium fluoride solution with a pH of 4.0. The electrolysis conditions were as follows: voltage 3V, current density 10mA / cm2, temperature 20°C, and treatment time 10s to form a fluoride layer on the magnesium oxide coating with a thickness of nanometer level. The obtained iron-nickel alloy foil was obtained.

[0159] Compared with Example 5, this comparative example does not undergo the heat treatment step.

[0160] Effect verification: The performance indicators of the iron-nickel alloy foils obtained in Comparative Examples 7-10 were tested, and the results are shown in Table 2.

[0161] Table 2: Performance indicators of the iron-nickel alloy foils obtained in Comparative Examples 7-10

[0162]

[0163] Note: The above detection methods and instruments are conventional techniques.

[0164] By comparing the experimental data of Comparative Examples 7-10 in the table, the following detailed conclusions can be drawn:

[0165] Comparative Example 7: This titanium-nickel alloy foil was free of magnesium oxide coating. The roughness of the S-side and M-side surfaces were Ra: 0.56 μm / Rz: 1.64 μm and Ra: 0.76 μm / Rz: 1.81 μm, respectively. The resulting iron-nickel alloy foil had a tensile strength of 994 MPa, an elongation of 2.45%, and a curl of 10 mm. The tensile strength was low, and the curl was high.

[0166] Comparative Example 8: This titanium-nickel alloy foil had no fluorinated layer. The roughness of the S-side and M-side surfaces were Ra: 0.84 μm / Rz: 1.87 μm and Ra: 0.78 μm / Rz: 2.02 μm, respectively. The resulting iron-nickel alloy foil had a tensile strength of 1287 MPa, an elongation of 2.13%, and a curl of 8 mm. This foil exhibited high tensile strength and high curl.

[0167] Comparative Example 9: This titanium-nickel alloy foil had no magnesium oxide coating or fluoride layer. The roughness of the S-surface and M-surface were Ra: 0.95 μm / Rz: 2.01 μm and Ra: 1.01 μm / Rz: 2.02 μm, respectively. The resulting iron-nickel alloy foil had a tensile strength of 1160 MPa, an elongation of 3.26%, and a curl of 15 mm. The tensile strength was low, and the curl was high.

[0168] Comparative Example 10: This titanium-nickel alloy foil had a magnesium oxide coating and a fluoride layer but was not heat-treated. The roughness of the S-plane and M-plane were Ra: 0.26 μm / Rz: 1.48 μm and Ra: 0.22 μm / Rz: 1.44 μm, respectively. The resulting iron-nickel alloy foil had a tensile strength of 1103 MPa, an elongation of 1.81%, and a curl of 5 mm. The tensile strength was low, and the curl was reduced.

[0169] Based on the experimental data of Examples 7-10, the following conclusions can be drawn:

[0170] The surface roughness of the iron-nickel alloy foil in Comparative Example 7 is increased compared with that in Example 5, the tensile strength is decreased, the elongation is increased, and the curl is increased. It is speculated that the reason is that the magnesium oxide coating can fill some defects such as microscopic pits and scratches 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 tensile strength and a decrease in hardness, which increases the curl.

[0171] The surface roughness of the iron-nickel alloy foil in Comparative Example 8 was significantly increased compared to that in Example 5, while its tensile strength decreased slightly, its elongation increased, and its curl increased. This is presumably because the fluoride layer selectively corrodes the microscopic protrusions on the surface of the titanium-nickel alloy foil, smoothing the surface and reducing roughness. Furthermore, the fluoride layer deposits evenly on the foil surface during formation, filling tiny pits and crevices and also helping to reduce surface roughness. However, the fluoride layer is generally harder and less tough, thus reducing elongation.

[0172] The surface roughness, elongation, and curl of the iron-nickel alloy foil in Comparative Example 9 were significantly increased compared to those in Example 5, while the tensile strength was significantly decreased.

[0173] 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 greatly reduced. It is speculated that the reason is that after the titanium-nickel alloy foil, magnesium oxide coating, and fluoride layer are heat-treated, the magnesium oxide coating, fluoride layer, and titanium-nickel alloy foil are more tightly bonded, and the interfacial bonding force is enhanced, so that the coating can more effectively transfer stress and better share the tensile load borne by the alloy foil, thereby improving 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 is more uniform, which also helps to improve the strength. During the heat treatment process, the particles in the magnesium oxide coating and the fluoride layer may agglomerate and recrystallize, making the coating surface denser and smoother. 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.

[0174] In summary, the scheme proposed in the present invention composites a magnesium oxide coating and a fluoride layer on an iron-nickel alloy foil, which has the advantages of increasing hardness and tensile strength, while also reducing surface roughness and low curling. Therefore, in the production process of negative electrode materials in which active materials are coated on negative electrode current collectors, the active materials can be evenly coated normally, thereby increasing production volume. The low-curl iron-nickel alloy foil preparation method and the low-curl iron-nickel alloy foil component ratio cooperate with each other to jointly realize an iron-nickel alloy foil material with low curling, high stability, and excellent electrochemical properties.

[0175] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A method for preparing a low-curl iron-nickel alloy foil suitable for all-solid-state batteries, characterized in that: The following steps are involved: (1) The anode plate and the 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 the iron-nickel alloy foil is obtained by peeling; The electrolyte solution comprises 10-100 g / L of an iron salt solution, 5-50 g / L of a nickel salt solution, additives, and pure water, wherein the additives comprise 1.0-3.0 g / L of a stress relaxant, 15.0-30.0 g / L of a pH stabilizer, 0.1-3.0 g / L of an Fe reducing agent, 10.0-25.0 g / L of a conductive additive, and 0.1-1.0 g / L of a wetting agent. The stress reliever is any one of saccharin sodium, 1,4-butanediol, dibenzenesulfonimide, sodium propylenesulfonate or 2-propylheptanol; The pH stabilizer is one of boric acid, sodium borate or boron nitride; The Fe reducing agent is one of glucose, ascorbic acid, sodium gluconate or glycine; The conductive additive is one of sodium chloride, sodium sulfate, sodium carbonate or sodium citrate; The wetting agent is one of sodium succinate, sodium dodecylbenzenesulfonate or sodium isethionate; (2) electrophoretically treating the iron-nickel alloy foil with a magnesium oxide electrophoretic solution in an electrophoretic bath to form a magnesium oxide coating on the iron-nickel alloy foil, and then electrochemically fluorinating the iron-nickel alloy foil after cleaning with an acid solution to form a fluoride layer on the magnesium oxide coating; (3) heat treating the iron-nickel alloy foil in a heat treatment chamber at a temperature not exceeding 600° C., and cooling the foil to obtain the iron-nickel alloy foil; The iron-nickel alloy foil has a thickness of 1 μm-10 μm and a curl of 2-5 mm.

2. The method for preparing a low curl iron-nickel alloy foil suitable for all-solid-state batteries according to claim 1, characterized in that: The temperature of the electrolyte solution is 45-65°C, and the applied current density is 6-10A / dm 2 The flow rate of the electrolyte solution is 20-40m 3 / hr, the pH of the electrolyte solution is adjusted by sulfuric acid and sodium carbonate, and the pH is 2.0-3.

0.

3. The method for preparing a low curl iron-nickel alloy foil suitable for all-solid-state batteries according to claim 1, characterized in that: 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 or nickel carbonate.

4. The method for preparing a low curl iron-nickel alloy foil suitable for 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 relaxer is saccharin sodium, the pH stabilizer is boric acid, the Fe reducing agent is ascorbic acid, the conductive additive is sodium chloride, and the wetting agent is sodium succinate. The iron sulfate content is 43.2 g / L, the nickel sulfate content is 18.6 g / L, the saccharin sodium 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.

5. The method for preparing a low curl iron-nickel alloy foil suitable for all-solid-state batteries according to claim 1, characterized in that: During the electrophoresis of the iron-nickel alloy foil using magnesium oxide electrophoresis solution in the electrophoresis pool: The magnesium oxide electrophoresis solution comprises 5-20 g / L magnesium oxide powder, 3-8 g / L isopropyl alcohol solution, 0.3-0.8 g / L dispersant and pure water; The electrophoresis conditions 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 minutes.

6. The method for preparing a low curl iron-nickel alloy foil suitable for all-solid-state batteries according to claim 1, characterized in that: The acid solution is a 10-12 wt% dilute hydrochloric acid solution or a dilute sulfuric acid solution.

7. The method for preparing a low curl iron-nickel alloy foil suitable for all-solid-state batteries according to claim 1, characterized in that: The iron-nickel alloy foil is subjected to an electrochemical fluorination treatment, specifically: A three-electrode system was used, with iron-nickel alloy foil as the working electrode, Ag / AgCl as the reference electrode, and platinum sheet as the counter electrode. The electrolyte was 0.10-0.15 mol / L ammonium fluoride solution, pH = 4.0-4.2; electrolysis conditions were: voltage 2-5 V, current density 5-15 mA / cm², temperature 15-25°C, and treatment time 10-30 s.

8. The method for preparing a low curl iron-nickel alloy foil suitable for 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 minutes, and 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 minutes.

9. Low curl iron-nickel alloy foil suitable for all-solid-state batteries, characterized in that: The low-curl iron-nickel alloy foil suitable for all-solid-state batteries is prepared by the preparation method of any one of claims 1-8.

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