A negative electrode current collector Fe-Ni alloy foil and a method for preparing the same

Abstract

The application belongs to the technical field of Fe-Ni alloy foil, and particularly relates to a negative electrode current collector Fe-Ni alloy foil and a preparation method thereof. In the Fe-Ni alloy foil, the mass percentage of iron is 35-65%, the mass percentage of nickel is 35-65%, and the sum of the mass percentages of the two is greater than or equal to 99% and less than or equal to 100%. The application aims to solve the technical problems of poor mechanical properties of the Fe-Ni alloy foil in the prior art and poor controllability of Fe and Ni content in production, and provides an Fe-Ni alloy foil with excellent mechanical properties and controllable Fe and Ni content.

Description

Technical Field

[0001] This invention belongs to the field of Fe-Ni alloy foil, specifically a negative electrode current collector Fe-Ni alloy foil and its preparation method. Background Technology

[0002] Fe-Ni alloys are widely used due to their excellent magnetic properties and low coefficient of expansion. They can be used as core materials, magnetic shielding materials, magnetostrictive materials, magnetic storage materials, lead frame materials, and battery skeleton materials, and have become an important component of new materials and high technology. Furthermore, Fe-Ni alloy foils have superior mechanical properties compared to pure iron foils and pure nickel foils. Fe-Ni alloy foils are obtained by replacing some of the precious metal nickel with inexpensive iron. Their corrosion resistance is comparable to bright nickel, and their toughness is better than bright nickel, thus saving nickel resources and effectively reducing costs.

[0003] There is limited existing research on the electrodeposition preparation of Fe-Ni alloy foils, especially those involving high-mechanical-performance Fe-Ni alloy foils. Chinese invention patent publication CN108559915A discloses "An Fe-Ni alloy and its preparation method," with the prepared alloy foil exhibiting a tensile strength between 810 and 880 MPa. Chinese invention patent publication CN108166024A discloses "A process for preparing Fe-Ni alloy foil by electrodeposition," but with a small and narrow current density range of only 3.6-4.0 A / dm². 2 The difference from the production current is significant, and the tensile strength of the prepared alloy foil is less than 800MPa; Patent CN107805761B discloses "an iron-nickel alloy foil and its manufacturing method", in which the Fe-Ni alloy foil prepared has a narrow adjustable range of Fe-Ni content and a tensile strength between 1.0 and 1.5GPa.

[0004] It is evident that Fe-Ni alloys prepared by existing electrodeposition methods exhibit low tensile strength and poor controllability of Fe and Ni content in the plating solution. Regarding the low tensile strength, during battery fabrication, the current collector (Fe-Ni alloy foil) coated with active material undergoes processes such as flattening and winding. If the tensile strength and elongation are low, problems such as cracking, detachment from the active material, and reduced battery cycle life are likely to occur. Regarding the poor controllability, since Fe and Ni have different electrodeposition potentials, Fe is preferentially deposited. The preparation of Fe-Ni is a co-deposition process. If this is not controlled, it will result in less or no Ni deposition. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention aims to provide a negative electrode current collector Fe-Ni alloy foil and its preparation method. The present invention aims to solve the technical problems of poor mechanical properties of Fe-Ni alloy foil and poor controllability of Fe and Ni content in the production of the prior art, and to provide a Fe-Ni alloy foil with excellent mechanical properties and controllable Fe and Ni content.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A negative electrode current collector Fe-Ni alloy foil, wherein the mass percentage of iron in the Fe-Ni alloy foil is 35-65%, the mass percentage of nickel is 35-65%, and the sum of the mass percentages of the two is ≥99% and ≤100%, with the remainder being impurities.

[0008] Preferably, the thickness of the Fe-Ni alloy foil is 3-10 μm, and the thickness is measured with a micrometer. Compared with the prior art, the Fe-Ni alloy foil of the present invention is thinner. When the Fe-Ni alloy is applied to the negative electrode current collector, the thinner the thickness, the smaller its proportion in the battery. Under the condition of constant cell volume, the amount of active material can be increased, and the thickness of the slurry coating is increased. This directly promotes the improvement of the cell energy density. Therefore, the thinner the Fe-Ni alloy foil, the greater its effect on improving the energy density of the battery. The lowest thickness disclosed in the known patents is 5 μm. Moreover, when the thickness of the Fe-Ni alloy foil of the present invention is 3 μm, the mechanical properties are higher than those of the known patents proposed in the background art.

[0009] Preferably, the Fe-Ni alloy foil has a tensile strength greater than 1.5 GPa and an elongation greater than 5%.

[0010] This invention also protects the preparation method of the above-mentioned negative electrode current collector Fe-Ni alloy foil, which includes the following steps:

[0011] The electrodeposition method involves placing a cathode roller and an anode plate in a reaction tank containing an electrolyte, and then electrodepositing an Fe-Ni alloy foil onto the cathode roller. The electrolyte consists of the following components:

[0012] The main salts are FeSO4·7H2O at 55–120 g / L and NiSO4·6H2O at 105–315 g / L; further, FeSO4·7H2O at 60–110 g / L and NiSO4·6H2O at 110–300 g / L.

[0013] The complexing agent, sodium citrate, is 3–10 g / L; further, sodium citrate is 3–8 g / L. The complexing agent can form a stable and uniform complex with metal ions, altering the properties and behavior of the metal ions, and in this invention, preventing Fe... 3+ Fe(OH)3 precipitate is formed;

[0014] The buffer is boric acid at a concentration of 6–40 g / L; further, boric acid at a concentration of 6–35 g / L; the buffer is used to adjust the pH balance of the plating solution.

[0015] Antioxidant ascorbic acid 3-15 g / L; further, ascorbic acid 3-10 g / L; antioxidants are used to prevent Fe 2+ Oxidized to Fe 3+ ;

[0016] The additives include two or more of the following: sodium saccharin (3-15 g / L), sodium dodecyl sulfate (0.1-2 g / L), sodium polydithiopropane sulfonate (0.5-2 ppm), collagen (0.5-5 ppm), hydroxyethyl cellulose (0.5-5 ppm), polyethylene glycol 2000 (0.5-5 ppm), HCl (3-24 ml / L), and NaCl (5-30 g / L). These additives are used to alter the cathode polarization, thereby changing the mechanical properties, microstructure, and appearance of the alloy foil.

[0017] Furthermore, two or more of the following are included: sodium saccharin 3–12 g / L, sodium dodecyl sulfate 0.1–1.5 g / L, collagen 0.5–3 ppm, hydroxyethyl cellulose 0.5–3 ppm, polyethylene glycol 2000 0.5–2 ppm, HCl 3–20 ml / L, and NaCl 5–25 g / L.

[0018] Preferably, the electrolyte is prepared according to the following steps:

[0019] After dissolving the buffer in heated pure water, the main salt, complexing agent, and antioxidant are added sequentially and stirred until dissolved. Finally, the additives are added, and the temperature is adjusted to 30–60°C. Temperature has little effect on the iron-nickel content, but excessively high temperatures affect foil formation and slightly lower performance indicators. Excessively low temperatures result in a more vigorous reaction, increased solution resistance, and higher electrical losses. The pH is adjusted to 1.9–2.9 to obtain the electrolyte. Furthermore, the solution preparation temperature is 40–55°C, and the solution pH is 2.0–2.7. Excessively high or low temperatures and pH affect the foil's appearance, mechanical properties, microstructure, and the Fe and Ni content of the coating.

[0020] Preferably, the pH is adjusted using a 5% sulfuric acid solution (by volume) or a 5% NaOH solution (by mass).

[0021] Preferably, the steps of the electrodeposition method are as follows:

[0022] The cathode roller, which has been polished and preheated with sandpaper, is placed in the electrolytic cell. The sandpaper used for polishing the cathode roller is 1000-1500#. The electroplating stirring speed and cathode current density are adjusted, and the electroplating time is controlled. Direct current is applied to perform electrodeposition of Fe-Ni alloy foil. After electrodeposition, the cathode roller is removed and washed twice with water, dried, and peeled off from the cathode to obtain Fe-Ni alloy foil.

[0023] Preferably, the electrodeposition parameters are: stirring speed 30–80 rpm; excessive stirring speed will result in a violent reaction, affecting foil formation; insufficient stirring speed will affect the iron-nickel content of the coating, reducing the Fe content and elongation (<5%); cathode current density 10–35 A / dm³. 2 The electroplating time is 70-150 seconds. The time affects the thickness of the Fe-Ni alloy foil. When the current is fixed, a shorter time results in a thinner foil, and a longer time results in a thicker foil.

[0024] Furthermore, the stirring speed is 30–70 rpm, and the cathode current density is 10–30 A / dm³. 2 Electroplating time is 70–140 seconds.

[0025] Preferably, the cathode roller for electrodeposition is a pure titanium roller, and the anode plate is a titanium-plated iridium anode plate. Both the cathode roller and the anode plate for electrodeposition are obtained after screening.

[0026] Preferably, the preheating temperature of the cathode roller is 30-60°C. After preheating, the cathode roller is placed in the electrolyte without lowering the electrolyte temperature. Furthermore, after preheating the cathode roller, no pinholes are generated in the resulting foil.

[0027] Furthermore, the cathode roller is preheated in pure water at a temperature of 40–55°C.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. The method of this invention produces an ultra-thin Fe-Ni alloy foil with good mechanical properties, a smooth surface morphology, and a thickness of 3-10 μm. The tensile strength of the Fe-Ni alloy foil is greater than 1.5 GPa, and the elongation is greater than 5%. During the battery manufacturing process, the current collector (Fe-Ni alloy foil) coated with active material needs to undergo processes such as flattening and winding. If the tensile strength and elongation are low, cracks are likely to occur and the foil may detach from the active material, thereby reducing the battery cycle life. The Fe-Ni alloy foil provided by this invention has excellent mechanical properties and overcomes the technical defects of existing current collectors.

[0030] 2. The Fe-Ni alloy foil prepared by this invention has an iron content of 35-65%, a nickel content of 35-65%, and an impurity content of less than 1%. The Fe and Ni contents in the alloy foil are highly controllable and can be adjusted according to the needs of the battery. Different contents result in different mechanical properties, which can be reasonably adjusted according to requirements.

[0031] 3. This invention provides a method for preparing Fe-Ni alloy foil for battery negative electrode current collectors. The Fe-Ni alloy foil prepared by this method has strong corrosion resistance and high safety, and can be used as a battery negative electrode current collector. Attached Figure Description

[0032] Figure 1 The tensile strength and elongation of Fe-Ni alloy foils in Examples 1-3 and Comparative Example 1 of this invention are shown in the diagram.

[0033] Figure 2 This is a scanning electron microscope image of the Fe-Ni alloy foil from Example 1 of the present invention;

[0034] Figure 3 This is a scanning electron microscope image of the Fe-Ni alloy foil from Example 2 of the present invention;

[0035] Figure 4 This is a scanning electron microscope image of the Fe-Ni alloy foil from Example 3 of the present invention;

[0036] Figure 5 This is a scanning electron microscope image of the Fe-Ni alloy foil of Comparative Example 1 of the present invention;

[0037] Figure 6 This is a physical image of the Fe-Ni alloy foil of Comparative Example 2 of the present invention;

[0038] Figure 7 This is a scanning electron microscope image of the Fe-Ni alloy foil of Comparative Example 3 of the present invention;

[0039] Figure 8 This is a physical image of the Fe-Ni alloy foil of Comparative Example 4 of the present invention;

[0040] Figure 9 In the figure, (a) is a physical image of the Fe-Ni alloy foil of Comparative Example 5 of the present invention, and (b) is a scanning electron microscope image of the Fe-Ni alloy foil of Comparative Example 5 of the present invention.

[0041] Figure 10 This is a scanning electron microscope image of the Fe-Ni alloy foil of Comparative Example 6 of the present invention;

[0042] Figure 11 This is a scanning electron microscope image of the Fe-Ni alloy foil of Comparative Example 7 of the present invention;

[0043] Figure 12In the image, (a) is an electron microscope image of the Fe-Ni alloy foil, (b) is an EDS energy dispersive spectroscopy (EDS) image, and (b) is the energy dispersive spectroscopy (EDS) image of the area selected in (a).

[0044] Figure 13 The image shows a comparison of corrosion resistance performance. The left image is of copper foil, and the right image is of the Fe-Ni alloy foil of Example 1 of this invention. Detailed Implementation

[0045] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0046] This invention enables the preparation of alloy foils with controllable Fe and Ni contents by adjusting the electrolyte composition in the plating bath, namely the main salt concentration, additives, complexing agents, antioxidants, and buffers. Furthermore, it considers the Fe content... 2+ Easily oxidized to Fe 3+ The problem is that this invention enables Fe 2+ It exists stably in solution;

[0047] The Fe-Ni alloy foil of the present invention has excellent mechanical properties. In terms of mechanical properties, the present invention creatively uses additives and screens the amount of additives and the current density. Under the combined effect of additives and current density, Fe-Ni alloy foil with excellent mechanical properties is obtained.

[0048] The experimental conditions provided in this invention have all been screened and obtained. Research has shown that only when the mass percentage of iron is 35-65% and the mass percentage of nickel is 35-65% can a Fe-Ni alloy foil with a tensile strength greater than 1.5 GPa and an elongation greater than 5% be obtained, i.e., a Fe-Ni alloy foil with excellent mechanical properties be obtained. Comparative studies using examples show that Fe-Ni alloy foil with excellent mechanical properties cannot be obtained under conditions outside the scope of this application. The technical solution of this application is studied below using examples and comparative examples, as detailed below:

[0049] Example 1

[0050] A method for preparing a Fe-Ni alloy foil as a negative electrode current collector, wherein the alloy foil has the following mass percentages: 49.76% iron and 49.66% nickel, comprising the following steps:

[0051] (1) Solution preparation:

[0052] The weighed boric acid was dissolved in pure water at 40°C by stirring. Then, NiSO4·6H2O was added and dissolved by stirring, followed by sodium citrate and ascorbic acid and FeSO4·7H2O and dissolved by stirring. NaCl and sodium saccharin were then added and dissolved by stirring. Finally, the pH was adjusted to 2.0 with a 5% sulfuric acid solution to obtain the electrolyte.

[0053] The specific components of the electrolyte are: FeSO4·7H2O 85g / L, NiSO4·6H2O 275g / L, sodium citrate 3g / L, boric acid 8g / L, ascorbic acid 5g / L, sodium saccharin 3g / L, and NaCl 10g / L;

[0054] (2) Electrodeposition process:

[0055] Pour the electrolyte from step (1) into the electrolytic cell, using a titanium cathode roller as the cathode and a titanium-plated iridium anode plate as the anode. Place the cathode roller, which has been polished with 1200# sandpaper and preheated to 40°C, into the electrolytic cell as the cathode. Adjust the electroplating stirring speed to 40 rpm and the cathode current density to 25 A / dm³. 2 The electroplating time is 80 seconds. Direct current is applied to electrodeposit Fe-Ni alloy foil. After electrodeposition, the cathode roller is removed, and the foil undergoes two water washing, drying, and peeling processes to obtain the Fe-Ni alloy foil. Its microstructure is as follows: Figure 2 As shown, the thickness is 5μm.

[0056] Example 2

[0057] A method for preparing a Fe-Ni alloy foil as a negative electrode current collector, wherein the alloy foil has the following mass percentages: 63.78% iron and 36.01% nickel, comprising the following steps:

[0058] (1) Solution preparation:

[0059] The weighed boric acid was dissolved in pure water at 50°C by stirring. Then, NiSO4·6H2O was added and dissolved by stirring, followed by sodium citrate and ascorbic acid and FeSO4·7H2O. HCl, sodium polydisulfide dipropane sulfonate, and sodium saccharin were then added and dissolved by stirring. Finally, the pH was adjusted to 2.7 with 5% sodium hydroxide to obtain the electrolyte.

[0060] The specific components of the electrolyte are: FeSO4·7H2O 100g / L, NiSO4·6H2O 305g / L, sodium citrate 5g / L, boric acid 25g / L, ascorbic acid 3g / L, sodium saccharin 8g / L, sodium polydisulfide dipropane sulfonate 0.5ppm, and HCl 10mL / L.

[0061] (2) Electrodeposition process:

[0062] Pour the electrolyte from step (1) into the electrolytic cell, using a titanium cathode roller as the cathode and a titanium-plated iridium anode plate as the anode. Place the cathode roller, which has been polished with 1200# sandpaper and preheated to 50°C, into the electrolytic cell as the cathode. Adjust the electroplating stirring speed to 60 rpm and the cathode current density to 30 A / dm³. 2 The electroplating time is 70 seconds. Direct current is applied to electrodeposit Fe-Ni alloy foil. After electrodeposition, the cathode roller is removed, and the foil undergoes two water washing, drying, and peeling processes to obtain the Fe-Ni alloy foil. Its microstructure is as follows: Figure 3 As shown, the thickness is 5μm.

[0063] Example 3

[0064] A method for preparing a Fe-Ni alloy foil as a negative electrode current collector, wherein the alloy foil has the following mass percentages: 35.45% iron and 64.24% nickel, and includes the following steps:

[0065] (1) Solution preparation:

[0066] Weighed boric acid was dissolved in pure water at 50°C by stirring. Then, NiSO4·6H2O was added and dissolved by stirring, followed by sodium citrate and ascorbic acid and FeSO4·7H2O. NaCl, sodium dodecyl sulfate, collagen, and sodium saccharin were then added and dissolved by stirring. Finally, the pH was adjusted to 2.4 with 5% (v / v) dilute sulfuric acid to obtain the electrolyte.

[0067] The specific components of the electrolyte are: FeSO4·7H2O 65g / L, NiSO4·6H2O 285g / L, sodium citrate 3g / L, boric acid 18g / L, ascorbic acid 5g / L, sodium saccharin 10g / L, sodium dodecyl sulfate 1g / L, collagen 2ppm, and NaCl 20g / L.

[0068] (2) Electrodeposition process:

[0069] Pour the electrolyte from step (1) into the electrolytic cell, using a titanium cathode roller as the cathode and a titanium-plated iridium anode plate as the anode. Place the cathode roller, which has been polished with 1200# sandpaper and preheated to 50°C, into the electrolytic cell as the cathode. Adjust the electroplating stirring speed to 30 rpm and the cathode current density to 30 A / dm³. 2 The electroplating time is 70 seconds. Direct current is applied to electrodeposit Fe-Ni alloy foil. After electrodeposition, the cathode roller is removed, and the foil undergoes two water washing, drying, and peeling processes to obtain the Fe-Ni alloy foil. Its microstructure is as follows: Figure 4 As shown, the thickness is 5μm.

[0070] Example 4

[0071] A method for preparing a Fe-Ni alloy foil as a negative electrode current collector, wherein the alloy foil has the following mass percentages: iron 38.21% and nickel 61.14%, and includes the following steps:

[0072] (1) Solution preparation:

[0073] The weighed boric acid was dissolved in pure water at 50°C by stirring. Then, NiSO4·6H2O was added and dissolved by stirring, followed by sodium citrate and ascorbic acid and FeSO4·7H2O. Hydroxyethyl cellulose and polyethylene glycol 2000 were then added and dissolved by stirring. Finally, the pH was adjusted to 2.9 with 5% (v / v) dilute sulfuric acid to obtain the electrolyte.

[0074] The specific components of the electrolyte are: FeSO4·7H2O 55g / L, NiSO4·6H2O 105g / L, sodium citrate 4g / L, boric acid 6g / L, ascorbic acid 4g / L, hydroxyethyl cellulose 0.5g / L, and polyethylene glycol 20005ppm;

[0075] (2) Electrodeposition process:

[0076] Pour the electrolyte from step (1) into the electrolytic cell, using a titanium cathode roller as the cathode and a titanium-plated iridium anode plate as the anode. Place the cathode roller, which has been polished with 1200# sandpaper and preheated to 50°C, into the electrolytic cell as the cathode. Adjust the electroplating stirring speed to 30 rpm and the cathode current density to 35 A / dm³. 2 The electroplating time is 100s. Direct current is applied to electrodeposit Fe-Ni alloy foil. After electrodeposition, the cathode roller is removed and subjected to two water washing, drying and peeling processes to obtain Fe-Ni alloy foil.

[0077] Example 5

[0078] A method for preparing a Fe-Ni alloy foil as a negative electrode current collector, wherein the alloy foil has the following mass percentages: 54.60% iron and 44.81% nickel, comprising the following steps:

[0079] (1) Solution preparation:

[0080] The weighed boric acid was dissolved in pure water at 50°C by stirring. Then, NiSO4·6H2O was added and dissolved by stirring, followed by sodium citrate and ascorbic acid and FeSO4·7H2O. Sodium dodecyl sulfate and sodium saccharin were then added and dissolved by stirring. Finally, the pH was adjusted to 1.9 with 5% dilute sulfuric acid to obtain the electrolyte.

[0081] The specific components of the electrolyte are: FeSO4·7H2O 120g / L, NiSO4·6H2O 315g / L, sodium citrate 10g / L, boric acid 40g / L, ascorbic acid 15g / L, sodium saccharin 15g / L, and sodium dodecyl sulfate 2g / L.

[0082] (2) Electrodeposition process:

[0083] Pour the electrolyte from step (1) into the electrolytic cell, using a titanium cathode roller as the cathode and a titanium-plated iridium anode plate as the anode. Place the cathode roller, which has been polished with 1500# sandpaper and preheated to 50°C, into the electrolytic cell as the cathode. Adjust the electroplating stirring speed to 80 rpm and the cathode current density to 10 A / dm³. 2 The electroplating time is 150s. Direct current is applied to electrodeposit Fe-Ni alloy foil. After electrodeposition, the cathode roller is removed and subjected to two water washing, drying and peeling processes to obtain Fe-Ni alloy foil.

[0084] Comparative Example 1

[0085] A method for preparing a Fe-Ni alloy foil for a negative electrode current collector is disclosed. The comparative example follows the same steps as Example 1, except that FeSO4·7H2O is replaced from 85 g / L to 40 g / L, and NiSO4·6H2O is replaced from 275 g / L to 350 g / L. Specifically, the amount of FeSO4·7H2O in the main salt is reduced to below the lower limit, and the amount of NiSO4·6H2O is increased to above the upper limit. The resulting Fe-Ni alloy foil has the following mass percentages: 18.78% iron and 80.42% nickel. The method includes the following steps:

[0086] (1) Solution preparation:

[0087] The weighed boric acid was dissolved in pure water at 50°C by stirring. Then, NiSO4·6H2O was added and dissolved by stirring, followed by sodium citrate and then ascorbic acid and then FeSO4·7H2O and then sodium saccharin and then dissolved by stirring. Finally, the pH was adjusted to 2.0 with 5% dilute sulfuric acid to obtain the electrolyte.

[0088] The specific components of the electrolyte are: FeSO4·7H2O 40g / L, NiSO4·6H2O 350g / L, sodium citrate 3g / L, boric acid 8g / L, ascorbic acid 5g / L, sodium saccharin 3g / L, and NaCl 10g / L;

[0089] (2) Electrodeposition process:

[0090] Pour the electrolyte from step (1) into the electrolytic cell, using a titanium cathode roller as the cathode and a titanium-plated iridium anode plate as the anode. Place the cathode roller, which has been polished with 1200# sandpaper and preheated to 50°C, into the electrolytic cell as the cathode. Adjust the electroplating stirring speed to 40 rpm and the cathode current density to 25 A / dm³. 2 The electroplating time is 80s. Direct current is applied to electrodeposit Fe-Ni alloy foil. After electrodeposition, the cathode roller is removed and subjected to two water washing, drying and peeling processes to obtain Fe-Ni alloy foil with a thickness of 5μm.

[0091] Because the amount of FeSO4·7H2O in this comparative example is lower than the range of this application, while the amount of NiSO4·6H2O is higher than the range of this application, the Ni content of the Fe-Ni alloy foil is greater than 65%, and the iron content is less than 35%, and its microstructure is as follows. Figure 5 As shown, Figure 5 Electron microscopy revealed that the Fe-Ni alloy foil contained numerous nodular particles and had an uneven surface. The tensile strength of the obtained Fe-Ni alloy foil was 0.88 GPa and the elongation was 4.3%. At this point, the mechanical properties did not meet the requirements, with tensile strength <1.5 GPa and elongation <5%.

[0092] Comparative Example 2

[0093] A method for preparing a Fe-Ni alloy foil negative electrode current collector is disclosed. The preparation steps in this comparative example are the same as in Example 1, except that FeSO4·7H2O is replaced from 85 g / L to 150 g / L, and NiSO4·6H2O is replaced from 275 g / L to 95 g / L. In other words, the amount of FeSO4·7H2O in the main salt is replaced with a value higher than the upper limit, and the amount of NiSO4·6H2O is replaced with a value lower than the lower limit. The method includes the following steps:

[0094] (1) Solution preparation:

[0095] The weighed boric acid was dissolved in pure water at 50°C by stirring. Then, NiSO4·6H2O was added and dissolved by stirring, followed by sodium citrate and then ascorbic acid and then FeSO4·7H2O and then sodium saccharin and then dissolved by stirring. Finally, the pH was adjusted to 2.0 with 5% dilute sulfuric acid to obtain the electrolyte.

[0096] The specific components of the electrolyte are: FeSO4·7H2O 150g / L, NiSO4·6H2O 95g / L, sodium citrate 3g / L, boric acid 8g / L, ascorbic acid 5g / L, sodium saccharin 3g / L, and NaCl 10g / L;

[0097] (2) Electrodeposition process:

[0098] Pour the electrolyte from step (1) into the electrolytic cell, using a titanium cathode roller as the cathode and a titanium-plated iridium anode plate as the anode. Place the cathode roller, which has been polished with 1200# sandpaper and preheated to 50°C, into the electrolytic cell as the cathode. Adjust the electroplating stirring speed to 40 rpm and the cathode current density to 25 A / dm³. 2 The electroplating time is 80 seconds. Direct current is applied to electrodeposit Fe-Ni alloy foil. After electrodeposition, the cathode roller is removed and washed with water twice and dried.

[0099] Because the amount of FeSO4·7H2O in this comparative example exceeds the range of this application, while the amount of NiSO4·6H2O is lower than the range of this application, the Fe content of the Fe-Ni alloy foil is greater than 65% and the Ni content is less than 35%. At this point, foil cannot be formed and cannot be peeled off, rendering content determination meaningless. Therefore, content determination was not performed, and no mechanical property data are available. The results are as follows: Figure 6 As shown.

[0100] Comparative Example 3

[0101] A method for preparing a Fe-Ni alloy foil negative electrode current collector is the same as the preparation steps in Example 1, except that the current value is changed to be below the lower limit, i.e., the current is changed from 25 A / dm 2 Replace with 5A / dm 2 It includes the following steps:

[0102] (1) Solution preparation:

[0103] The weighed boric acid was dissolved in pure water at 40°C by stirring. Then, NiSO4·6H2O was added and dissolved by stirring, followed by sodium citrate and ascorbic acid and FeSO4·7H2O and dissolved by stirring. NaCl and sodium saccharin were then added and dissolved by stirring. Finally, the pH was adjusted to 2.0 with a 5% sulfuric acid solution to obtain the electrolyte.

[0104] The specific components of the electrolyte are: FeSO4·7H2O 85g / L, NiSO4·6H2O 275g / L, sodium citrate 3g / L, boric acid 8g / L, ascorbic acid 5g / L, sodium saccharin 3g / L, and NaCl 10g / L;

[0105] (2) Electrodeposition process:

[0106] Pour the electrolyte from step (1) into the electrolytic cell, using a titanium cathode roller as the cathode and a titanium-plated iridium anode plate as the anode. Place the cathode roller, which has been polished with 1200# sandpaper and preheated to 40°C, into the electrolytic cell as the cathode. Adjust the electroplating stirring speed to 40 rpm and the cathode current density to 5 A / dm³. 2The electroplating time is 80s. Direct current is applied to electrodeposit Fe-Ni alloy foil. After electrodeposition, the cathode roller is removed and subjected to two water washing, drying and peeling processes to obtain Fe-Ni alloy foil with a thickness of 5μm.

[0107] The results are as follows Figure 7 As shown, Figure 7 The results show that the Fe-Ni alloy foil has good foil formation, but the electron microscope shows obvious color difference and coarse nodular particles. The mechanical properties are poor, with tensile strength <1.5GPa and elongation <5%.

[0108] Comparative Example 4

[0109] A method for preparing a Fe-Ni alloy foil negative electrode current collector is the same as the preparation steps in Example 1, except that the current is changed to exceed the upper limit, i.e., the current is changed from 25 A / dm 2 Replace with 45A / dm 2 It includes the following steps:

[0110] (1) Solution preparation:

[0111] The weighed boric acid was dissolved in pure water at 40°C by stirring. Then, NiSO4·6H2O was added and dissolved by stirring, followed by sodium citrate and ascorbic acid and FeSO4·7H2O and dissolved by stirring. NaCl and sodium saccharin were then added and dissolved by stirring. Finally, the pH was adjusted to 2.0 with a 5% sulfuric acid solution to obtain the electrolyte.

[0112] The specific components of the electrolyte are: FeSO4·7H2O 85g / L, NiSO4·6H2O 275g / L, sodium citrate 3g / L, boric acid 8g / L, ascorbic acid 5g / L, sodium saccharin 3g / L, and NaCl 10g / L;

[0113] (2) Electrodeposition process:

[0114] Pour the electrolyte from step (1) into the electrolytic cell, using a titanium cathode roller as the cathode and a titanium-plated iridium anode plate as the anode. Place the cathode roller, which has been polished with 1200# sandpaper and preheated to 40°C, into the electrolytic cell as the cathode. Adjust the electroplating stirring speed to 40 rpm and the cathode current density to 45 A / dm³. 2 The electroplating time is 80s. Direct current is applied to electrodeposit Fe-Ni alloy foil. After electrodeposition, the cathode roller is removed and subjected to two water washing, drying and peeling processes to obtain Fe-Ni alloy foil with a thickness of 5μm.

[0115] The results are as follows Figure 8 As shown, Figure 8 The results show that when the current exceeds the upper limit, foil cannot be formed, and the structure becomes fragmented.

[0116] Comparative Example 5

[0117] A method for preparing a Fe-Ni alloy foil negative electrode current collector is the same as the preparation steps in Example 1, except that the amount of additives is controlled so that sodium saccharin is 1 g / L and NaCl is 4 g / L, that is, the amount of additives is less than the lower limit value. The method includes the following steps:

[0118] (1) Solution preparation:

[0119] The weighed boric acid was dissolved in pure water at 50°C by stirring. Then, NiSO4·6H2O was added and dissolved by stirring, followed by sodium citrate and then ascorbic acid and then FeSO4·7H2O and then sodium saccharin and then dissolved by stirring. Finally, the pH was adjusted to 2.0 with 5% dilute sulfuric acid to obtain the electrolyte.

[0120] The specific components of the electrolyte are: FeSO4·7H2O 85g / L, NiSO4·6H2O 275g / L, sodium citrate 3g / L, boric acid 8g / L, ascorbic acid 5g / L, sodium saccharin 1g / L, and NaCl 4g / L.

[0121] (2) Electrodeposition process:

[0122] Pour the electrolyte from step (1) into the electrolytic cell, using a titanium cathode roller as the cathode and a titanium-plated iridium anode plate as the anode. Place the cathode roller, which has been polished with 1200# sandpaper and preheated to 50°C, into the electrolytic cell as the cathode. Adjust the electroplating stirring speed to 40 rpm and the cathode current density to 25 A / dm³. 2 The electroplating time is 80s. Direct current is applied to electrodeposit Fe-Ni alloy foil. After electrodeposition, the cathode roller is removed and subjected to two water washing, drying and peeling processes to obtain Fe-Ni alloy foil with a thickness of 5μm.

[0123] like Figure 9 As shown, when the amount of additive is small, the foil-forming properties are poor. Electron microscopy was performed on selected foil-forming areas, and the results showed that there were many large nodular particles on the surface, making it uneven. At this time, the Fe content was 20.86% and the Ni content was 78.88%. It can be seen that even though the amounts of FeSO4·7H2O and NiSO4·6H2O are within the range of this application, the Fe and Ni contents in the Fe-Ni alloy foil cannot reach the required range due to the reduction in the amount of additive.

[0124] Comparative Example 6

[0125] A method for preparing a Fe-Ni alloy foil negative electrode current collector, which involves changing the pH to 1.5 (i.e., lowering the pH value below the lower limit), includes the following steps:

[0126] (1) Solution preparation:

[0127] The weighed boric acid was dissolved in pure water at 50°C by stirring. Then, NiSO4·6H2O was added and dissolved by stirring, followed by sodium citrate and then ascorbic acid and then FeSO4·7H2O and then sodium saccharin and then dissolved by stirring. Finally, the pH was adjusted to 1.5 with 5% (v / v) dilute sulfuric acid to obtain the electrolyte.

[0128] The specific components of the electrolyte are: FeSO4·7H2O 110g / L, NiSO4·6H2O 300g / L, sodium citrate 3g / L, boric acid 20g / L, ascorbic acid 5g / L, sodium saccharin 8g / L, and NaCl 10g / L.

[0129] (2) Electrodeposition process:

[0130] Pour the electrolyte from step (1) into the electrolytic cell, using a titanium cathode roller as the cathode and a titanium-plated iridium anode plate as the anode. Place the cathode roller, which has been polished with 1200# sandpaper and preheated to 50°C, into the electrolytic cell as the cathode. Adjust the electroplating stirring speed to 30 rpm and the cathode current density to 30 A / dm³. 2 The electroplating time is 70s. Direct current is applied to electrodeposit Fe-Ni alloy foil. After electrodeposition, the cathode roller is removed and subjected to two water washing, drying and peeling processes to obtain Fe-Ni alloy foil with a thickness of 5μm.

[0131] The resulting Fe-Ni alloy foil has an Fe content greater than 65%, a Ni content less than 35%, a tensile strength <1.5 GPa, an elongation <5%, and a thickness of 5 μm. Figure 10 Electron microscopy revealed numerous nodular particles and an uneven foil surface. Furthermore, if the additive in the solution is sodium saccharin, it will precipitate and deposit on the anode plate, thereby reducing the current efficiency.

[0132] Comparative Example 7

[0133] A method for preparing a Fe-Ni alloy foil negative electrode current collector is the same as that for Comparative Example 6, except that the pH is changed to 3.0, i.e., the pH value is higher than the upper limit, and includes the following steps:

[0134] (1) Solution preparation:

[0135] The weighed boric acid was dissolved in pure water at 50°C by stirring. Then, NiSO4·6H2O was added and dissolved by stirring, followed by sodium citrate and then ascorbic acid and then FeSO4·7H2O and then sodium saccharin and then dissolved by stirring. Finally, the pH was adjusted to 3 with 5% dilute sulfuric acid to obtain the electrolyte.

[0136] The specific components of the electrolyte are: FeSO4·7H2O 110g / L, NiSO4·6H2O 300g / L, sodium citrate 3g / L, boric acid 20g / L, ascorbic acid 5g / L, sodium saccharin 8g / L, and NaCl 10g / L.

[0137] (2) Electrodeposition process:

[0138] Pour the electrolyte from step (1) into the electrolytic cell, using a titanium cathode roller as the cathode and a titanium-plated iridium anode plate as the anode. Place the cathode roller, which has been polished with 1200# sandpaper and preheated to 50°C, into the electrolytic cell as the cathode. Adjust the electroplating stirring speed to 30 rpm and the cathode current density to 30 A / dm³. 2 The electroplating time is 70s. Direct current is applied to electrodeposit Fe-Ni alloy foil. After electrodeposition, the cathode roller is removed and subjected to two water washing, drying and peeling processes to obtain Fe-Ni alloy foil with a thickness of 5μm.

[0139] like Figure 11 The electron micrograph shows that there are many nodular particles and the foil surface is uneven. At this time, the mechanical properties do not meet the requirements, with tensile strength <1.5GPa and elongation <5%.

[0140] This invention employs an electrodeposition method to prepare Fe-Ni alloy foil, using a sulfate system as the electrolyte, a titanium cathode roller as the cathode, and a titanium-plated iridium anode plate as the anode. The Fe-Ni alloy foil is prepared in an electrolytic cell under the action of direct current. The tensile strength and elongation of the prepared Fe-Ni alloy foil are measured using a Shimadzu universal tensile testing machine, and the surface morphology and elemental content of the Fe-Ni alloy foil are measured using a Hitachi scanning electron microscope and a Bruker X-ray energy dispersive spectrometer.

[0141] Comparison of mechanical properties of Examples 1-3 and Comparative Example 1 Figure 1 As shown, via Figure 1 It can be seen that the tensile strength of the Fe-Ni alloy foils obtained in Examples 1-3 is not much different, and the tensile strength is greater than 1.5 GPa and the elongation is greater than 5%, which are all better than Comparative Example 1. It can be seen that the amount of main salt in the electrolyte has a great influence on the mass percentage of Fe-Ni alloy foil, and thus affects the mechanical properties of Fe-Ni alloy foil.

[0142] Figure 2-4 The results show that the Fe-Ni alloy foil in the example has a smoother and more even microstructure, without the coarse crystalline particles found in the control example.

[0143] The Fe-Ni alloy foil prepared by this invention has an iron mass percentage of 35-65%, a nickel mass percentage of 30-65%, and an impurity content of less than 1%. The obtained Fe-Ni alloy foil is then subjected to the following process... Figure 12The EDS energy dispersive spectroscopy analysis yielded the data shown in Table 1:

[0144] Table 1. Relative elemental content of Fe-Ni alloy foil

[0145] Al Ka 8.74 0.999 .473 wt.% .104 Fe Ka 745.80 45.845 44.860 wt.% .437 Ni Ka 558.88 53.156 54.667 wt.% .620 100.000 100.000 wt.% total

[0146] This invention also included a comparative study of corrosion resistance experiments. The Fe-Ni alloy foil prepared in Example 1 of this invention was compared with the copper foil used in battery current collectors. Corrosion tests were conducted in acidic solutions with pH = 2 and Cl... - =120g / L, Cl is controlled by NaCl - Concentration, pH is adjusted by sulfuric acid; such as Figure 13 As shown, the results indicate that the Fe-Ni alloy foil is more stable, basically does not dissolve, and its appearance remains largely unchanged after immersion for 24 hours.

[0147] Those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims and their equivalents, this invention is also intended to include these modifications and variations.

Claims

1. A Fe-Ni alloy foil for negative electrode current collector, characterized in that, In the Fe-Ni alloy foil, the mass percentage of iron is 35-65%, the mass percentage of nickel is 35-65%, and the sum of the mass percentages of the two is ≥99% and ≤100%; the thickness of the Fe-Ni alloy foil is 5-10μm, and the tensile strength of the Fe-Ni alloy foil is greater than 1.5GPa, and the elongation is greater than 5%; The Fe-Ni alloy foil for the negative electrode current collector is prepared according to the following steps: The electrodeposition method involves placing a cathode roller and an anode plate in a reaction tank containing an electrolyte, and then electrodepositing an Fe-Ni alloy foil onto the cathode roller. The electrolyte consists of the following components: The main salts FeSO4·7H2O have a concentration of 55~120 g / L and NiSO4·6H2O has a concentration of 105~315 g / L. Complexing agent: sodium citrate 3~10g / L; Buffer boric acid 6~40g / L; Antioxidant ascorbic acid 3~15g / L; The additives include two or more of the following: sodium saccharin 3~15g / L, sodium dodecyl sulfate 0.1~2g / L, sodium polydithiopropane sulfonate 0.5~2ppm, collagen 0.5~5ppm, hydroxyethyl cellulose 0.5~5ppm, polyethylene glycol 2000 0.5~5ppm, HCl 3~24ml / L, and NaCl 5~30g / L. The electrolyte is prepared according to the following steps: after dissolving the buffer in heated pure water by stirring, the main salt, complexing agent, and antioxidant are added in sequence by stirring and dissolving. Finally, the additives are added, and the temperature is adjusted to 30~60℃ and the pH to 1.9~2.9 to obtain the electrolyte. The steps of the electrodeposition method are as follows: A preheated and polished cathode roller is placed in an electrolytic cell, and a direct current is applied to electrodeposit Fe-Ni alloy foil. After electrodeposition, the Fe-Ni alloy foil is peeled off from the cathode. The preheating temperature of the cathode roller is 30~60℃, and the electrodeposition parameters are: stirring speed 30~80rpm, cathode current density 10~35A / dm³. 2 Electroplating time is 70~150s.

2. The Fe-Ni alloy foil for the negative electrode current collector according to claim 1, characterized in that, The cathode roller for electrodeposition is a pure titanium roller, and the anode plate is a titanium-plated iridium anode plate.

3. The Fe-Ni alloy foil for the negative electrode current collector according to claim 1, characterized in that, Adjust the pH using a 5% sulfuric acid solution (volume fraction) or a 5% NaOH solution (mass fraction).

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