Preparation method and application of an iron anode additive

Abstract

This invention discloses a method for preparing an iron anode additive and its application, belonging to the field of battery anode material preparation. This invention utilizes a high-temperature solid-state method or co-precipitation method to prepare Cu with a spinel structure. 1‑x Sn x Bi₂O₄ is used as a negative electrode additive in nickel-iron or iron-air batteries. This additive effectively improves the battery's specific capacity, reduces electrode expansion, decreases gas evolution, and extends battery life. In application, Cu... 1‑ x Sn x Bi2O4 structured powder additives are mixed with Fe3O4, the negative electrode active material, to serve as the negative electrode active material in iron-nickel batteries or iron-air batteries. During charging, it helps to increase the hydrogen evolution overpotential of the negative electrode material, thereby improving the charging efficiency of the battery. During discharging, it reduces passivation and prevents the increase of internal resistance, thus improving the discharge efficiency and discharge plateau of the battery.

Description

Technical Field

[0001] This invention belongs to the field of preparation technology of iron-nickel secondary battery and iron-air battery anode materials, specifically relating to a preparation method and application of an iron anode additive. Background Technology

[0002] Currently available square rechargeable batteries mainly include lead-acid batteries and lithium-ion batteries. Lead-acid batteries have low energy density, generally only reaching 30-35 Wh / kg, with a cycle life of around 300-350 cycles, requiring a long charging time. Furthermore, lead is a toxic heavy metal, and improper handling during production and recycling can cause serious environmental pollution, leading to restrictions on their production and use worldwide. Lithium-ion batteries, on the other hand, have relatively high energy density. However, they suffer from poor safety performance under high-capacity, high-voltage operating conditions, and face a series of problems, including difficulties in recycling spent lithium-ion batteries and resulting environmental pollution.

[0003] Nickel-hydrogen batteries, a type of alkaline secondary battery, use rare earth metals, resulting in high costs and hindering large-scale adoption. Nickel-zinc batteries offer high specific energy and power, but the zinc anode material is prone to zinc dendrite formation during use, shortening battery life and presenting challenges in manufacturing large-capacity batteries. Nickel-iron batteries (including rechargeable iron-air batteries) have long lifespans and are safe and environmentally friendly; however, the iron anode has a relatively positive potential (-0.877V), making it prone to hydrogen evolution during charging, leading to low charging efficiency and water loss due to hydrogen evolution. Current optimization efforts for nickel-iron and iron-air batteries primarily focus on the iron anode. The use of additives can address low-cost application strategies and is one of the simplest, most reliable, and most direct and effective methods. Summary of the Invention

[0004] This invention combines the characteristics of nickel-iron secondary batteries and rechargeable iron-air batteries, providing a method for preparing an iron anode additive that can effectively improve the hydrogen evolution overpotential of the battery's negative electrode and enhance charging efficiency. The battery anode additive prepared by this method utilizes the higher hydrogen evolution overpotential of tin and the more positive electrode potentials of bismuth and copper to suppress the hydrogen evolution reaction of the iron anode during charging. Simultaneously, tin and copper also improve the conductivity of the anode active material. The preparation process of this invention is simple, generates no solid waste or wastewater, and is environmentally friendly and safe.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preparing an iron anode additive, which uses a high-temperature solid-state method or a co-precipitation method to prepare a spinel structure (Cu) 1-x Sn x Bi2O4, when mixed with Fe3O4, is used as the negative electrode active material in nickel-iron batteries or rechargeable iron-air batteries.

[0006] Preferably, when using the solid-state method, trivalent metal oxides and divalent metal oxides are mixed in a certain proportion, and then the mixture is sintered in a high-temperature furnace at 450–950°C for 1–10 hours under an inert atmosphere or a reducing atmosphere. After pulverization and sieving, Cu is formed. 1-x Sn x Additives with a Bi2O4 structure.

[0007] Preferably, when using the co-precipitation method, a trivalent metal salt solution and a divalent metal salt solution are mixed in a certain proportion, and then precipitated using an alkali as a precipitant. After filtration, washing, and drying, a precursor is formed. The precursor is then placed in a high-temperature furnace and sintered at 450–950°C for 1–10 hours under an inert atmosphere or a reducing atmosphere. The target product is then obtained by pulverizing and sieving.

[0008] Preferably, the trivalent metal oxide is Bi2O3, and the trivalent metal salt is one of Bi2(SO4)3, BiCl3, and Bi(NO3)3.

[0009] Preferably, the divalent metal oxide is CuO or SnO; the divalent metal salt is one of CuSO4, CuCl2, Cu(NO3)2 and one of SnSO4, SnCl2, Sn(NO3)2.

[0010] Preferably, x is 0.5; that is, Cu 1-x Sn x Bi2O4 is Cu 0.5 Sn 0.5 Bi2O4.

[0011] This invention also discloses Cu 1-x Sn x The application of Bi2O4 spinel-structured iron anode additives as additives in the anode active material of iron-nickel batteries or iron-air batteries. Specifically, Cu... 1-x Sn x Bi2O4 structured powder additives are mixed with Fe3O4, a negative electrode active material, in a mixer and then used as a negative electrode active material for iron-nickel batteries or iron-air batteries.

[0012] Preferably, Cu 1-x Sn x The mass percentage of Bi2O4 structured powder additives added to the negative electrode active material is 5-10 wt%.

[0013] Preferred, Cu 1-x Sn xA mixture of Bi2O4-structured powder additives and Fe3O4, the negative electrode active material, is further stirred with a binder to form a slurry, which is then coated onto a nickel-plated steel strip. After drying and rolling, it forms an electrode sheet. The binder is one or more of CMC, HPMC, PVA, and PTFE.

[0014] Compared with the prior art, the present invention has the following beneficial effects: the negative electrode additive Cu obtained by the present invention 1- x Sn x When Bi2O4 is used as the negative electrode in nickel-iron batteries or rechargeable iron-air batteries, compared with conventional batteries that use iron(III) oxide or iron powder alone as the negative electrode material, it can effectively improve the specific capacity of the battery, reduce electrode expansion, reduce gas evolution, and extend the battery's lifespan. This negative electrode additive helps to increase the hydrogen evolution overpotential of the negative electrode material during charging, thereby improving the battery's charging efficiency; during discharging, it weakens passivation and prevents the increase of internal resistance, thus improving the battery's discharge efficiency and discharge plateau. Attached Figure Description

[0015] Figure 1 It is Cu 0.5 Sn 0.5 Cyclic voltammetry of Bi2O4;

[0016] Figure 2 It contains Cu 0.5 Sn 0.5 A comparison of the discharge characteristics of a battery with a Bi2O4 anode and a conventional iron anode battery. Detailed Implementation

[0017] The following examples further illustrate the above-described content of the present invention, but it should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention.

[0018] Example 1

[0019] 2M Bi₂O₃, 0.5M CuO, and 0.5M SnO powders were mixed in a mixer for 1 hour. The mixture was then placed in a high-temperature furnace and sintered at 750°C for 2 hours under an inert or reducing atmosphere. After cooling to room temperature, the mixture was pulverized and sieved to form Cu. 0.5 Sn 0.5Bi2O4 structured powder additive. This additive was added to the iron-nickel battery negative electrode material iron(III) oxide at a ratio of 5-10 wt%, and stirred with one or more binders of CMC, HPMC, PVA, and PTFE to form a slurry. The slurry was then coated onto a nickel-plated steel strip, dried, and rolled to form an electrode sheet. This electrode sheet was then assembled with a nickel hydroxide positive electrode sheet to form a full cell. After formation in a 6M KOH solution, a charge-discharge test was conducted.

[0020] Example 2

[0021] BiCl3, CuCl, and SnCl were dissolved in deionized water in a molar ratio of 2:0.5:0.5. The mixture was reacted with NaOH or NaCO3 as a precipitant for 1 hour under stirring at room temperature. After filtration, washing, and drying, a precursor was formed. This precursor was then sintered in a high-temperature furnace at 750°C for 1.5 hours under an inert or reducing atmosphere. After cooling to room temperature, the precursor was pulverized and sieved to form CuCl2. 0.5 Sn 0.5 Bi2O4 structured powder additive. This additive was added to the iron-nickel battery negative electrode material iron(III) oxide at a ratio of 5-10 wt%, and stirred with one or more binders of CMC, HPMC, PVA, and PTFE to form a slurry. The slurry was then coated onto a nickel-plated steel strip, dried, and rolled to form an electrode sheet. This electrode sheet was then assembled with a nickel hydroxide positive electrode sheet to form a full cell. After formation in a 6M KOH solution, a charge-discharge test was conducted.

[0022] Figure 1 The Cu prepared in Example 1 is shown. 0.5 Sn 0.5 The cyclic voltammogram of Bi2O4 shows that the material prepared in Example 2 has the same cyclic voltammogram as that in Example 1, indicating that the preparation method does not affect the performance of the product. Figure 2 This illustrates Cu prepared in Example 1. 0.5 Sn 0.5 A comparison of the discharge curves of a battery with Bi2O4 additive and a conventional iron anode battery. By comparing the charge-discharge curves, it is shown that the anode additive prepared in this invention, when used in the anode material of an iron-nickel battery, effectively reduces the charging voltage, increases the specific capacity, improves the formation rate and discharge plateau, and reduces gas evolution compared to conventional iron anode materials.

[0023] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing an iron anode additive, characterized in that, Cu with a spinel structure was prepared using a high-temperature solid-state method or a co-precipitation method. 1-x Sn x Bi2O4 is used as an additive for iron anodes, where 0 < x < 1.

2. The method for preparing an iron anode additive according to claim 1, characterized in that, The specific process is as follows: trivalent metal oxide and divalent metal oxide are mixed in a certain proportion, and then the mixture is sintered in a high-temperature furnace at a temperature of 450-950℃ for 1-10 hours under an inert atmosphere or a reducing atmosphere. The target product is obtained after pulverization.

3. The method for preparing an iron anode additive according to claim 1, characterized in that, The specific process is as follows: a trivalent metal salt solution and a divalent metal salt solution are mixed in a certain proportion, and then precipitated with an alkali as a precipitant. After filtration, washing and drying, a precursor is formed. The precursor is then placed in a high-temperature furnace and sintered at 450-950℃ for 1-10 hours under an inert atmosphere or a reducing atmosphere. The target product is then obtained by crushing and sieving.

4. A method for preparing an iron anode additive according to claim 2 or 3, characterized in that, The trivalent metal oxide is Bi2O3; the trivalent metal salt is one of Bi2(SO4)3, BiCl3, and Bi(NO3)3.

5. A method for preparing an iron anode additive according to claim 2 or 3, characterized in that, The divalent metal oxides are CuO and SnO; the divalent metal salts are one or more of CuSO4, CuCl2, Cu(NO3)2, SnSO4, SnCl2, and Sn(NO3)2.

6. The method for preparing an iron anode additive according to claim 1, characterized in that, The iron anode additive has a spinel structure Cu 0.5 Sn 0.5 Bi2O4.

7. The application of the iron anode additive prepared by the method of claim 1 or 6 as an additive for the anode active material of iron-nickel batteries or iron-air batteries.

8. The application according to claim 7, characterized in that, Cu 1-x Sn x Bi2O4 structured powder additives are mixed with Fe3O4, a negative electrode active material, and used as a negative electrode active material for iron-nickel batteries or iron-air batteries.

9. The application according to claim 8, characterized in that, Cu 1-x Sn x The mass percentage of Bi2O4 structured powder additives added to the negative electrode active material is 5-10 wt%.

10. The application according to claim 8, characterized in that, Cu 1-x Sn x A mixture of Bi2O4-structured powder additives and Fe3O4, a negative electrode active material, is further stirred with a binder to form a slurry, which is then coated onto a nickel-plated steel strip. After drying and rolling, it forms an electrode sheet.

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