Preparation method and application of iron negative electrode additive

Abstract

The invention discloses a preparation method and application of an iron negative electrode additive, and belongs to the field of preparation of battery negative electrode materials, and a material of Cu1-xSnxBi2O4 with a spinel structure is prepared by utilizing a high-temperature solid-phase method or a coprecipitation method and is used as a negative electrode additive of an iron-nickel battery or an iron-air battery. The negative electrode additive can effectively improve the specific capacity of the battery, reduce the electrode expansion, reduce the gas evolution amount and prolong the service life of the battery. During application, the powder additive with the Cu1-xSnxBi2O4 structure is mixed with a negative electrode active substance Fe3O4 to serve as the negative electrode active substance of an iron-nickel battery or an iron-air battery; the hydrogen evolution overpotential of the negative electrode material can be improved during charging, so that the charging efficiency of the battery is improved; and during discharging, the passivation phenomenon is weakened, and the internal resistance is prevented from being increased, so that the discharging efficiency and the discharging platform of the battery are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of negative electrode materials for iron-nickel secondary batteries and iron-air batteries, and particularly relates to a preparation method and application of an iron negative electrode additive. Background Art

[0002] Currently available square secondary batteries mainly include lead-acid batteries and lithium-ion batteries. Among them, lead-acid batteries have a low specific energy, generally only reaching 30-35 Wh / Kg, with a cycle life of about 300-350 times, requiring a long charging time. At the same time, lead is a toxic heavy metal, and improper handling during the production process and recycling process will cause serious environmental pollution, and its production and use have been restricted by countries around the world. Lithium-ion batteries have a relatively high specific energy, but lithium-ion batteries have poor safety performance in high-capacity and high-voltage usage environments, and at the same time face a series of problems such as difficulties in recycling waste lithium-ion batteries and environmental pollution.

[0003] The hydrogen-nickel battery in alkaline secondary batteries uses precious metals such as rare earths, with a high usage cost and difficulty in large-scale popularization; the zinc-nickel secondary battery has a relatively high specific energy and specific power, but the zinc negative electrode material is prone to zinc dendrites during use, resulting in a shortened service life of the zinc-nickel secondary battery, and there are also problems such as difficulties in manufacturing large-capacity batteries. Iron-nickel secondary batteries (including rechargeable iron-air batteries) have a long service life, are safe and environmentally friendly, but the iron negative electrode potential is relatively positive (-0.877V), and hydrogen is easily precipitated during charging, resulting in problems such as low charging efficiency and easy hydrogen evolution and water loss; currently, most of the main optimization work on iron-nickel batteries and iron-air batteries focuses on the iron negative electrode. The use of additives can solve the application strategy of low cost and is also one of the simplest, reliable, most direct and effective means. Summary of the Invention

[0004] Combining the characteristics of iron-nickel secondary batteries and rechargeable iron-air batteries, the present invention provides a preparation method of an iron negative electrode additive that can effectively improve the hydrogen evolution overpotential of the battery negative electrode and the charging efficiency. The battery negative electrode additive prepared by this method uses the relatively high hydrogen evolution overpotential of tin and bismuth and copper with relatively positive electrode potentials to inhibit the hydrogen evolution reaction of the iron negative electrode during charging. At the same time, tin and copper can also improve the conductivity of the negative electrode active material. The preparation process of the present invention is simple, without the generation of solid waste and wastewater, and is environmentally friendly and safe.

[0005] The present invention adopts the following technical solution to solve the above technical problems. A preparation method of an iron negative electrode additive prepares a material with a spinel structure (Cu 1-x Sn x Bi2O4) by a high-temperature solid-phase method or a co-precipitation method, and after mixing with Fe3O4, it is used as the negative electrode active material of an iron-nickel battery or a rechargeable iron-air battery.

[0006] Preferably, when the solid-phase method is adopted, a trivalent metal oxide and a divalent metal oxide are mixed in a certain proportion, and then the mixture is sintered in a high-temperature furnace under an inert atmosphere or a reducing atmosphere-containing condition at a temperature of 450 to 950 °C for 1 to 10 h, and after being pulverized and sieved, Cu 1-x Sn x additive with a Bi2O4 structure is formed.

[0007] Preferably, when the co-precipitation method is adopted, a trivalent metal salt solution and a divalent metal salt solution are mixed in a certain proportion, and then an alkali is used as a precipitating agent for precipitation. After filtration, washing, and drying, a precursor is formed. Then the precursor is placed in a high-temperature furnace and sintered at a temperature of 450 to 950 °C for 1 to 10 h under an inert atmosphere or a reducing atmosphere-containing condition, and after being pulverized and sieved, the target product is obtained.

[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, SnO; the divalent metal salt is one of CuSO4, CuCl2, Cu(NO3)2 and one of SnSO4, SnCl2, Sn(NO3)2.

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

[0011] The present invention also discloses the application of the Cu 1-x Sn x additive of the Bi2O4 spinel structure for the negative electrode of an iron negative electrode as an additive for the negative electrode active material of an iron-nickel battery or an iron-air battery. Specifically, after the powder additive with a Cu 1-x Sn x Bi2O4 structure is mixed with the negative electrode active material Fe3O4 in a mixer, it is used as the negative electrode active material of an iron-nickel battery or an iron-air battery.

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

[0013] Preferably, Cu 1-x Sn xA mixture of a powder additive with a Bi2O4 structure and a negative electrode active material Fe3O4 is further stirred with a binder into a slurry and then coated on a nickel-plated steel strip. After drying and rolling, an electrode sheet is formed. 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 prepared by the present invention 1- x Sn x After Bi2O4 is used in the negative electrode of an iron-nickel battery or a rechargeable iron-air battery, compared with using only iron oxide or iron powder as the negative electrode material in a conventional battery, it can effectively improve the specific capacity of the battery, reduce electrode swelling, reduce the gas evolution amount, and extend the service life of the battery. This negative electrode additive helps to increase the hydrogen evolution overpotential of the negative electrode material during charging, thereby improving the charging efficiency of the battery; during discharging, it weakens the passivation phenomenon and prevents the increase of internal resistance, thus improving the discharging efficiency and discharging platform of the battery. Description of the Drawings

[0015] Figure 1 is the cyclic voltammogram of Cu 0.5 Sn 0.5 Bi2O4;

[0016] Figure 2 is the discharge comparison diagram of a battery composed of a negative electrode containing Cu 0.5 Sn 0.5 Bi2O4 and a common iron negative electrode battery. Detailed Embodiments

[0017] The above content of the present invention will be further described in detail below through examples, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples. Any technology implemented based on the above content of the present invention belongs to the scope of the present invention.

[0018] Example 1

[0019] 2M of Bi2O3, 0.5M of CuO, and 0.5M of SnO powder materials are stirred and mixed in a mixer for 1 h. The mixture is placed in a high-temperature furnace and sintered at a temperature of 750 °C for 2 h under an inert atmosphere or a condition with a reducing atmosphere. After cooling to room temperature, it is pulverized and sieved to form Cu 0.5 Sn 0.5Powder additive with Bi2O4 structure. This additive is added to the negative electrode material Fe3O4 of the iron-nickel battery at a ratio of 5-10 wt%, and stirred with one or more of the binders CMC, HPMC, PVA, and PTFE into a slurry, then coated on a nickel-plated steel strip. After drying and rolling, an electrode sheet is formed, which is assembled with a nickel hydroxide positive electrode sheet into a full battery and subjected to charge and discharge tests after formation in a 6M KOH solution.

[0020] Example 2

[0021] BiCl3, CuCl, and SnCl are dissolved in deionized water according to a molar ratio of 2:0.5:0.5. Under the condition of stirring at room temperature, NaOH or NaCO3 is used as a precipitating agent for reaction for 1 h. After filtration, washing, and drying, a precursor is formed. It is placed in a high-temperature furnace and sintered at a temperature of 750 °C for 1.5 h under an inert atmosphere or an atmosphere doped with a reducing atmosphere. After cooling to room temperature, it is pulverized and sieved to form Cu 0.5 Sn 0.5 Powder additive with Bi2O4 structure. This additive is added to the negative electrode material Fe3O4 of the iron-nickel battery at a ratio of 5-10 wt%, and stirred with one or more of the binders CMC, HPMC, PVA, and PTFE into a slurry, then coated on a nickel-plated steel strip. After drying and rolling, an electrode sheet is formed, which is assembled with a nickel hydroxide positive electrode sheet into a full battery and subjected to charge and discharge tests after formation in a 6M KOH solution.

[0022] Figure 1 The cyclic voltammogram of Cu 0.5 Sn 0.5 Bi2O4 prepared in Example 1 is shown. It should be noted that the cyclic voltammogram of the material prepared in Example 2 is the same as that in Example 1, indicating that the preparation method does not affect the performance of the product. Figure 2 Schematically shows the discharge comparison diagram of the battery composed of the Cu 0.5 Sn 0.5 Bi2O4 additive prepared in Example 1 and a common iron negative electrode battery. Through the comparison of the charge and discharge curves, after the negative electrode additive prepared by the present invention is used in the negative electrode material of the iron-nickel battery, compared with the conventional iron negative electrode material, the charging voltage is effectively reduced, the gram capacity is increased, the formation speed and the discharge platform are improved, and the gas evolution amount is reduced.

[0023] The above shows and describes the basic principles, main features, and advantages of the present invention. Without departing from the spirit and scope of the present invention, the present invention has various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A preparation method of an iron negative electrode additive, characterized in that, Prepare a material with a spinel structure of Cu 1-x Sn x Bi2O4 as an additive for the iron negative electrode, where 0 < x < 1.

2. The preparation method of an iron negative electrode additive according to claim 1, wherein, The specific process is as follows: Mix a trivalent metal oxide and a divalent metal oxide in a certain proportion, and then sinter the mixture in a high-temperature furnace under an inert atmosphere or a reducing atmosphere at a temperature of 450-950 °C for 1-10 h. After pulverization, the target product is obtained.

3. The preparation method of an iron negative electrode additive according to claim 1, characterized in that, The specific process is as follows: Mix a trivalent metal salt solution and a divalent metal salt solution in a certain proportion, and use an alkali as a precipitant for precipitation. After filtration, washing, and drying, a precursor is formed. Then, the precursor is placed in a high-temperature furnace and sintered at a temperature of 450-950 °C for 1-10 h under an inert atmosphere or a reducing atmosphere. After pulverization and sieving, the target product is obtained.

4. The preparation method of an iron negative electrode 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. The preparation method of an iron negative electrode additive according to claim 2 or 3, characterized in that, The divalent metal oxide is CuO or SnO; the divalent metal salt is one or several of CuSO4, CuCl2, Cu(NO3)2, SnSO4, SnCl2, and Sn(NO3)2.

6. The preparation method of an iron negative electrode additive according to claim 1, characterized in that, The iron negative electrode additive has a spinel structure Cu 0.5 Sn 0.5 Bi2O4.

7. Application of the iron negative electrode additive prepared by the method according to claim 1 or 6 as an additive for the negative electrode active material of an iron-nickel battery or an iron-air battery.

8. The application according to claim 7, wherein Mix Cu 1-x Sn x After mixing the powder additive with the Bi2O4 structure and the negative electrode active material Fe3O4, it is used as the negative electrode active material of a nickel-iron battery or an iron-air battery.

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

10. The application according to claim 8, characterized in that Mix the powder additive with the Bi2O4 structure and the negative electrode active material Fe3O4, and further stir it with a binder to form a slurry, which is then coated on a nickel-plated steel strip and dried and rolled to form an electrode sheet. 1-x Sn x A mixture of a powder additive with a Bi2O4 structure and the negative electrode active material Fe3O4 is further stirred with a binder to form a slurry, which is then coated on a nickel-plated steel strip and dried and rolled to form an electrode sheet.

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