Preparation method of zinc-based electrode material, zinc-based electrode and zinc-nickel secondary battery

Abstract

The invention relates to a preparation method of a zinc-based electrode material, and the preparation method comprises the following steps: stirring and dissolving a foaming agent, zinc nitrate and ammonium bismuth citrate in a deionized water solvent at room temperature, dropwise adding nitric acid to obtain a uniform solution, and drying the solution at the temperature of 80-120 DEG C to obtain a precursor; and reacting the precursor in a protective gas at the temperature of 450-600 DEG C to obtain the electrode material. The zinc-based electrode material prepared by the method has the electrochemical properties of high specific capacity, long cycle life and high magnification, the preparation process is simple and not tedious, the equipment requirement is low, the reaction condition is easy to control, the preparation period is short, and the method is suitable for industrialization.

Description

Technical Field

[0001] The present invention relates to the technical field of zinc-nickel secondary batteries, and in particular to a method for preparing a zinc-based electrode material, a zinc-based electrode and a zinc-nickel secondary battery. Background Art

[0002] As a type of aqueous battery, zinc-nickel secondary batteries have the advantages of high operating voltage, high energy density and specific power, low production cost and environmental friendliness. They are expected to replace lead-acid batteries or some lithium-ion batteries and be used as power or energy storage batteries.

[0003] However, the high solubility of zinc anode active materials and their discharge products in alkaline electrolytes can easily lead to dendrite formation, deformation, hydrogen evolution, and passivation during charge and discharge, resulting in a reduced battery cycle life and hindering the development of zinc-nickel secondary batteries. To improve the performance of zinc anodes, researchers have adopted a variety of approaches, including the use of additives, electrolyte improvements, and the development of new anode materials. In the development of new anode materials, surface modification, designing anode materials with specialized structures, and synthesizing nanoscale anode materials can effectively mitigate electrode deformation and inhibit dendrite formation and dissolution. Patent application CN201810759219A proposes the use of graphene / zinc oxide as a zinc anode active material, which improves the rate performance of zinc anode materials to a certain extent. Although these approaches have improved the cycle life of zinc-nickel secondary batteries to a certain extent, many of the developed zinc-based anode materials still cannot simultaneously meet the comprehensive electrochemical requirements of high specific capacity, long cycle life, and high rate capability. Furthermore, the preparation process involves tedious multi-step synthesis, demanding preparation conditions, and high costs, which hinder the further development of zinc-based anode materials. Developing new zinc anode materials remains an important means to solve the problems of current zinc anodes and promote the rapid development of zinc-nickel secondary batteries. Summary of the Invention

[0004] The purpose of the present invention is to provide a new method for preparing zinc-based electrode materials in response to the technical problems in the prior art of preparing zinc-based electrode materials, such as complicated preparation process, harsh preparation conditions or the inability of the prepared zinc-based electrode materials to simultaneously meet the comprehensive electrochemical properties of high specific capacity, long cycle life and high rate. The zinc-based electrode materials prepared by the method have electrochemical properties of high specific capacity, long cycle life and high rate, and the preparation process is simple and uncomplicated, the equipment requirements are low, the reaction conditions are easy to control, the preparation cycle is short, and the zinc-based electrode materials are suitable for industrialization and have high economic and social value.

[0005] The present invention provides a method for preparing a zinc-based electrode material, which comprises the following steps:

[0006] (1) Preparing a precursor: stirring and dissolving a foaming agent, zinc nitrate, and ammonium bismuth citrate in a solvent at room temperature, then dropping nitric acid to obtain a uniform solution, and drying the solution at a temperature range of 80° C. to 120° C. to obtain a precursor;

[0007] (2) Preparation of electrode material: reacting the precursor in a protective gas at a temperature range of 450° C. to 600° C. to obtain the electrode material.

[0008] In some embodiments, the foaming agent is one or more of polyvinyl pyrrolidone, glucose, fructose, and amino acid glucose.

[0009] In some embodiments, the mass ratio of zinc nitrate to foaming agent in step (1) is 20:1-5:1.

[0010] In some embodiments, the mass ratio of zinc nitrate to ammonium bismuth citrate in step (1) is 60:1-15:1.

[0011] In some embodiments, the protective gas in step (2) is one or more of nitrogen, helium, neon, and argon.

[0012] In some embodiments, the heating rate in step (2) is 2-6°C / min.

[0013] In some embodiments, the solvent in step (1) is deionized water.

[0014] The present invention also provides a zinc-based electrode, which is prepared from the zinc-based electrode material prepared by any of the preparation methods described above.

[0015] The present invention also provides a zinc-nickel secondary battery, which includes the above-mentioned zinc-based electrode.

[0016] Compared with the prior art, the preparation method of the zinc-based electrode material of the present invention has the following advantages:

[0017] 1. The method for preparing the zinc-based electrode material of the present invention involves the coordination reaction of zinc nitrate with the oxygen-containing functional groups of the foaming agent and ammonium bismuth citrate, and the organic bismuth salt is dispersed in the solution at the atomic and molecular levels, so that the specific surface area of the obtained composite material is significantly increased, and the generated bismuth and zinc oxide are uniformly dispersed in the carbon matrix, thereby having a better inhibitory effect on its volume change and dendrite growth during the electrochemical process.

[0018] 2. The conductive carbon layer obtained by the foaming of the foaming agent and the carbonization of ammonium bismuth citrate together constitutes a continuous conductive channel, which is beneficial to the transmission rate of electrons and provides structural support to suppress electrode deformation. Its large specific surface area enhances the solid-liquid contact area, enhances the charge transfer efficiency and the rate performance of the electrode material.

[0019] 3. The in-situ introduction of elemental bismuth further improves the conductivity and hydrogen evolution overpotential of the electrode material.

[0020] 4. By controlling the amount of foaming agent and ammonium bismuth citrate, the thickness and bismuth content of the carbon coating layer can be controlled, thereby controlling the electrochemical properties of the composite electrode material.

[0021] 5. The preparation method of the present invention has simple process, is environmentally friendly, and has a wide source of raw materials and is cheap.

[0022] 6. The composite electrode material of the present invention has a hierarchical porous structure, which is formed by the synergistic decomposition of nitrate and foaming agent. It has a larger specific surface area, more complete contact and infiltration with the electrolyte, and its cycle stability, charge and discharge performance and high rate performance are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the appearance morphology of ZnO@Bi2O3 prepared in Comparative Example 2 of the present invention;

[0024] Figure 2 XRD patterns of the composite negative electrode materials prepared in Comparative Examples 2 and 3 of the present invention;

[0025] Figure 3 This is a SEM image of a zinc-nickel secondary battery composite negative electrode material;

[0026] Figure 4 This is a mapping diagram of a zinc-nickel secondary battery composite negative electrode material;

[0027] Figure 5 This is a charge-discharge curve diagram obtained by testing a zinc-nickel secondary battery composite negative electrode material and a nickel hydroxide positive electrode in KOH electrolyte;

[0028] Figure 6 These are the results of cyclic charge and discharge experiments on a zinc-nickel experimental battery consisting of a zinc-nickel secondary battery composite negative electrode material and a nickel hydroxide positive electrode. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing a zinc-based composite electrode material, comprising the following steps:

[0030] First, a precursor is prepared: a foaming agent, zinc nitrate, and ammonium bismuth citrate are stirred and dissolved in deionized water at room temperature, and nitric acid is added dropwise to obtain a uniform solution. The solution is dried at a temperature range of 80°C to 120°C (inclusive), for example, 80°C, 90°C, 100°C, 110°C, and 120°C to obtain a precursor;

[0031] Then, the electrode material is prepared by reacting the precursor in a protective gas at a temperature range of 450°C-600°C (including the endpoint values), for example, 450°C, 500°C, 550°C, and 600°C, to obtain the electrode material.

[0032] The above-mentioned foaming agent can be one or more of polyvinyl pyrrolidone, glucose, fructose, and amino acid glucose. The mass ratio of zinc nitrate to the foaming agent is 20:1-5:1, the mass ratio of zinc nitrate to ammonium bismuth citrate is 60:1-15:1, and the protective gas is one or more of nitrogen, helium, neon, and argon.

[0033] In addition, in the step of preparing the electrode material, the heating rate is 2-6°C / min, for example, 2°C / min, 4°C / min, 5°C / min, 6°C / min.

[0034] The preparation method of the composite electrode material of the present invention comprises the following steps: first, in an aqueous reaction solvent, zinc nitrate is subjected to a coordination reaction with oxygen-containing functional groups of a foaming agent and ammonium bismuth citrate, so that an organic bismuth salt is dispersed in the solution in an atomic and molecular state, thereby ensuring uniform dispersion of bismuth and zinc oxide obtained by subsequent annealing; and then drying is performed to obtain a gelled precursor; then, the precursor is pyrolyzed under annealing conditions, and a large amount of gas released by the pyrolysis of the foaming agent is utilized to significantly increase the specific surface area of the generated carbon skeleton, and the generated bismuth and zinc oxide are uniformly dispersed in the carbon matrix; simultaneously, a carbon-containing compound generated by the pyrolysis of the foaming agent and ammonium bismuth citrate is utilized to deposit a carbon layer on the surface of the bismuth and zinc oxide, thereby coating the bismuth and zinc oxide, thereby forming an in-situ carbon-coated bismuth-doped zinc-nickel secondary battery composite electrode material; the in-situ carbon-coated bismuth-doped zinc-nickel secondary battery composite negative electrode material of the present invention has a simple preparation process, low equipment requirements, easy-to-control reaction conditions, a short preparation cycle, is suitable for industrialization, and has high economic and social value.

[0035] The present invention will be further described below with reference to the embodiments.

[0036] Example 1:

[0037] (1) Preparation of precursor: 9.60 g of Zn(NO3)2·6H2O was weighed and added to 15 ml of deionized water to completely dissolve; 0.6 g of polyvinyl pyrrolidone was added to the above solution and stirred at room temperature until the polyvinyl pyrrolidone was dissolved; 0.1446 g of ammonium bismuth citrate was then added to the above liquid, placed in an ultrasonic machine at room temperature, 15 drops of nitric acid was added and stirred until dissolved, and the mixture was dried in a drying oven at 120°C to obtain a precursor;

[0038] (2) Preparation of composite electrode material: The precursor obtained in step (1) was placed in a box furnace, heated to 450°C at a heating rate of 2°C / min in a nitrogen atmosphere, and then annealed at 450°C for 2h to obtain ZnO@Bi@C.

[0039] Comparative Example 1

[0040] (1) Preparation of precursor: 9.60 g of Zn(NO3)2·6H2O was weighed and added to 15 ml of deionized water to completely dissolve; 0.6 g of polyvinyl pyrrolidone was added to the above solution and stirred at room temperature until the polyvinyl pyrrolidone was dissolved; 0.1446 g of ammonium bismuth citrate was then added to the above liquid, placed in an ultrasonic machine at room temperature, 15 drops of nitric acid was added and stirred until dissolved, and the mixture was dried in a drying oven at 120°C to obtain a precursor;

[0041] (2) Preparation of composite electrode material: The precursor obtained in step (1) without adding ammonium bismuth citrate was placed in a muffle furnace and heated to 450°C at a heating rate of 4°C / min, and then kept in the muffle furnace at 450°C for 2 hours to obtain ZnO.

[0042] Comparative Example 2

[0043] (1) Preparation of precursor: 9.60 g of Zn(NO3)2·6H2O was weighed and added to 15 ml of deionized water to completely dissolve; 0.6 g of polyvinyl pyrrolidone was added to the above solution and stirred at room temperature until the polyvinyl pyrrolidone was dissolved; 0.1446 g of ammonium bismuth citrate was then added to the above liquid, placed in an ultrasonic machine at room temperature, 15 drops of nitric acid were added and stirred until dissolved, and the mixture was dried in a drying oven at 120°C to obtain a precursor.

[0044] (2) Preparation of composite electrode material: The precursor obtained in step (1) was placed in a muffle furnace and heated to 450°C at a heating rate of 2°C / min, and then kept in the muffle furnace at 450°C for 2h to obtain ZnO@Bi2O3 (such as Figure 1 shown).

[0045] Test example

[0046] The composite materials obtained in Comparative Example 2 and Comparative Example 3 were subjected to XRD diffraction test to obtain XRD patterns, as shown in FIG. Figure 2 As shown in the figure, it can be seen that the sample fired in the muffle furnace at 450℃ is ZnO@Bi2O3, and the sample fired in the nitrogen atmosphere at 450℃ is ZnO@Bi@C, indicating that at a slightly higher temperature, Bi2O3 is carbon-thermally reduced to form bismuth. The prepared ZnO@Bi2O3 composite material and ZnO@Bi@C composite material were subjected to high-magnification SEM scanning ( Figure 3 ) It can be seen from the observation that the ZnO nanoparticles are uniform in size (50-80nm), the ZnO nanoparticles are evenly embedded in the flocculent carbon layer, and the Bi element is evenly distributed ( Figure 4 ), which inhibits hydrogen evolution and is beneficial to the cycle stability under high rate charge and discharge conditions.

[0047] The obtained ZnO, ZnO@Bi@C composite materials, and ZnO@Bi2O3 composite materials were respectively used with nickel hydroxide positive electrode in KOH electrolyte to make pouch batteries, and their charge and discharge performance was tested using a test system. At a current density of 1C, the results are as follows. Figure 5 As shown in the figure, ZnO@Bi@C has the best performance, with a capacity close to 760mAh / g, followed by ZnO@Bi2O3, with a capacity close to 500mAh / g, and ZnO has the worst performance. This shows that the carbon layer coating isolates the direct contact between ZnO and the electrolyte, and the synergistic effect of bismuth doping suppresses the occurrence of unnecessary side reactions, thereby improving the capacity and cycle stability of the electrode material. At a current density of 5C, the current was charged and discharged at 20% of the actual capacity for 230 cycles. The results are as follows Figure 6 As shown in the figure, under extreme high current charge and discharge conditions, the composite electrode material can still maintain good stability and its performance decays slowly.

[0048] In some embodiments, the present invention further provides a zinc-based electrode, which is prepared from a zinc-based electrode material prepared by any of the above preparation methods.

[0049] In some other embodiments, the present invention further provides a zinc-nickel secondary battery comprising the above-mentioned zinc-based electrode.

[0050] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a zinc-based electrode material, characterized in that: The following steps are involved: (1) Preparing a precursor: stirring and dissolving a foaming agent, zinc nitrate, and ammonium bismuth citrate in a solvent at room temperature, then dropping nitric acid to obtain a uniform solution, and drying the solution at a temperature range of 80° C. to 120° C. to obtain a precursor; (2) Preparation of electrode material: reacting the precursor in a protective gas at a temperature range of 450° C. to 600° C. to obtain the electrode material.

2. The preparation method according to claim 1, characterized in that The foaming agent is one or more of polyvinyl pyrrolidone, glucose, fructose, and amino acid glucose.

3. The preparation method according to claim 1, characterized in that The mass ratio of the zinc nitrate to the foaming agent in step (1) is 20:1-5:

1.

4. The preparation method according to claim 1, characterized in that The mass ratio of zinc nitrate to ammonium bismuth citrate in step (1) is 60:1-15:

1.

5. The preparation method according to claim 1, characterized in that The protective gas described in step (2) is one or more of nitrogen, helium, neon and argon.

6. The preparation method according to claim 1, characterized in that The heating rate in step (2) is 2-6°C / min.

7. The preparation method according to claim 1, characterized in that The solvent described in step (1) is deionized water.

8. A zinc-based electrode, characterized in that The zinc-based electrode is prepared from the zinc-based electrode material prepared by the preparation method according to any one of claims 1 to 7.

9. A zinc-nickel secondary battery, characterized in that: The zinc-nickel secondary battery comprises the zinc-based electrode according to claim 7.

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