Group IIIA metal ion doped zinc oxide negative electrode material and preparation method and application thereof

Abstract

The invention discloses a group IIIA metal ion doped zinc oxide negative electrode material and a preparation method and application thereof, and belongs to the technical field of energy and materials.The preparation method comprises the steps that zinc oxide and a group IIIA metal compound are mixed, ground and calcined to obtain a precursor, fused salt and the precursor are mixed, and a mixed material is obtained; the metal-doped zinc oxide composite material is obtained after two-stage heating calcination and washing, and when the metal-doped zinc oxide composite material is used as a zinc-nickel battery negative electrode active material in an alkaline system, the metal-doped zinc oxide composite material shows relatively high specific discharge capacity, good cycling stability, relatively good crystallinity and a relatively good exposed crystal face; the method has the advantages of few process flows, low raw material cost, extremely short synthesis time, low energy consumption, environmental friendliness, safety, no toxicity and excellent performance, and is suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of energy and materials technology, specifically relating to a negative electrode material of zinc oxide doped with group IIIA metal ions, its preparation method and application. Background Technology

[0002] Due to increasing global energy demand, climate change, and the depletion of non-renewable energy sources, there is a need to develop more environmentally friendly energy sources, such as wind and solar power. However, renewable energy is intermittent and unstable, thus necessitating the development of high-performance, environmentally friendly, and economical energy storage devices. Pumped hydro storage projects currently hold a significant market share, but widespread adoption is not feasible. Therefore, the development of new energy storage technologies is required. Among various new energy storage technologies, lithium-ion batteries have dominated the commercial market for the past few decades due to their long cycle life and high energy density. However, they suffer from high cost and low safety. Therefore, there is a need to develop safer, more cost-effective alternative power sources.

[0003] Zn-Ni batteries have attracted widespread attention due to their high specific energy, stable discharge voltage, good low-temperature performance, and environmental friendliness. However, anode interface problems such as dendrite growth, hydrogen evolution, and interfacial side reactions lead to poor cycle stability of Zn-Ni batteries, severely limiting their further commercial applications.

[0004] Zinc oxide (ZnO) is used as the anode material in Zn-Ni batteries. It possesses a high theoretical specific capacity and a relatively stable structure, and is easy to prepare and modify. However, its practical application still faces some challenges, such as rapid capacity decay under high-rate charge-discharge conditions. Furthermore, ZnO has a band gap of 3.37 eV at room temperature, requiring high energy to transition from the valence band to the conduction band. The thermal energy at room temperature is insufficient to excite a large number of electrons to cross this band gap, resulting in few free electrons and poor conductivity. The resistivity of pure ZnO crystals can reach as high as 10⁻⁶ eV. 7 Ω·cm, almost an insulator.

[0005] To improve the conductivity of zinc oxide, it can be doped with metal ions. At room temperature, ZnO crystals exhibit n-type semiconductor properties. In n-type doping of ZnO, group IIIA elements such as Al, Ga, and In are typically chosen as the doping elements. While Ga possesses advantages such as high thermal stability and electrical conductivity, its high cost makes it unsuitable for large-scale production, and therefore it is not considered. Al is abundant in nature, has low production costs, high stability, and is easy to dope, making it a commonly chosen doping element. 3+ Ga 3+ In comparison, In 3+ The ionic radius of Zn 2+The ratio is closer to that of Al, Ga, and Zn; under high concentration doping, In has the highest carrier mobility among the three. At the same time, In has a large electronegativity and is less reactive than Al, Ga, and Zn, making it less likely to form oxides. This makes it more favorable for In to exist in the crystal lattice as a substitutional impurity, thus improving the conductivity of zinc oxide.

[0006] Currently, the main methods for synthesizing Al-doped zinc oxide include sol-gel method, hydrothermal synthesis method, and solvothermal synthesis method. The sol-gel method has the advantages of simple process and easy control of reaction process, but due to the poor sintering property between dry gel particles, there will be many defects if sintering into block material, and it is also difficult to sinter. Chen Guojun et al. synthesized Al-doped ZnO powder using sol-gel method and found that the crystal quality of ZnO is worse with the increase of Al doping concentration (CHEN KJ, FANG TH, HUNG F-, et al. The crystallization and physical properties of Al-doped ZnO nanoparticles [J]. Applied surface science, 2008,254(18): 5791-5.). The hydrothermal synthesis method has the advantages of high purity and good dispersibility of synthesized crystals and internal defects of crystals, but the hydrothermal synthesis method needs to be carried out at high temperature, so the requirements for autoclave are high. Compared with other methods, the nanocrystalline materials synthesized by solvothermal synthesis have more regular crystal orientation and higher purity. However, this method has poor safety performance, high equipment requirements, and is prone to environmental pollution. Lu Zhihui et al. synthesized Al-doped ZnO nanoparticles by solvothermal method followed by calcination in a hydrogen atmosphere. These uniformly dispersed, nearly spherical particles can be observed by transmission electron microscopy. With the increase of Al ion concentration, the diameter of the nanoparticles increases slightly. When the Al ion concentration increases to 10%, the Al-doped ZnO shows severe agglomeration and low crystallinity (LU Z, ZHOU J, WANG , et al. Synthesis of aluminum-doped ZnO nanocrystals with controllable morphology and enhanced electrical conductivity [J]. Journal of Materials Chemistry, 2011, 21(12):4161-7.).

[0007] Currently, the main methods for synthesizing In-doped zinc oxide include the sol-gel method and spray pyrolysis. The sol-gel method has the advantages of simple process and low cost, and can precisely control the doping concentration. However, it also has the disadvantage of high calcination temperature, which can easily lead to grain coarsening (Chen, KJ, et al. "Microstructures, optical and electrical properties of In-doped ZnO thin films prepared by sol–gel method."). Applied Surface Science 255.12 (2009): 6308-6312.). Spray pyrolysis is a simple process suitable for large-scale production, allowing for flexible adjustment of doping concentration. However, the uniformity of indium doping in spray pyrolysis is affected by the atomization effect, and strict substrate temperature control is required (Bae SY, Na CW, Kang JH, et al. Comparative structure and optical properties of Ga). - ,In,and Sn-doped ZnO nanowires synthesized viathermalevaporation[J].The Journal of Physical Chemistry B, 2005, 109(7):2526-2531.).

[0008] However, all of the above doping methods suffer from low effective occupancy rates. Summary of the Invention

[0009] This invention provides a negative electrode material of zinc oxide doped with group IIIA metal ions, its preparation method and application. The method achieves uniform doping of metal ions in zinc oxide through molten salt assisted method, which solves the problems of low effective occupancy, uneven doping and poor material performance in the prior art. The prepared negative electrode material is used in zinc-nickel batteries to significantly improve the cycle stability and rate performance of zinc-nickel batteries.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a negative electrode material of zinc oxide doped with group IIIA metal ions includes the following steps: (1) Zinc oxide is mixed with a compound containing Group IIIA metals in a certain proportion and then dry-milled. A small amount of ethanol is added, and the mixture is stirred and ground thoroughly at room temperature. After drying, the mixture is ground again until homogeneous to obtain a mixture. (2) Place the mixture in a muffle furnace and calcine it at 400℃-600℃ for 4-8 hours to obtain the precursor; (3) Mix the precursor and molten salt in a certain proportion, add ethanol and grind, dry and grind evenly, put into a crucible, and then put into a muffle furnace for calcination. (4) The calcined product is washed with deionized water and filtered until the residual molten salt is removed. The final product is obtained after vacuum drying.

[0011] In the steps described above, the compound containing Group IIIA metals is an aluminum- or indium-containing compound or element; the aluminum-containing compound is one of aluminum oxide, aluminum nitrate, or aluminum chloride, and the aluminum-containing element is aluminum powder; the indium-containing compound is one of indium oxide, indium nitrate, or indium acetate, and the indium-containing element is indium powder; the mass of the doped Group IIIA metal ions accounts for 0.1%-10% of the total mass of the final product (zinc oxide doped with metal ions).

[0012] The molten salt mentioned in step (3) is one or more of anhydrous strontium chloride, magnesium chloride, and calcium chloride, and its mass is 2-10 times that of the precursor.

[0013] In step (3), the calcination is divided into two stages. First, the temperature is raised to 700℃-900℃ at a rate of 2℃-10℃ per minute and held for 4-6 hours. Then, the temperature is raised to 1000℃-1150℃ at a rate of 1℃-5℃ per minute and held for 10-12 hours.

[0014] The negative electrode material of zinc oxide doped with group IIIA metal ions prepared by the above method is composed of zinc oxide and a compound containing group IIIA metals. The group IIIA metal ions occupy the positions of zinc ions in the zinc oxide lattice, forming substitutional doping or filling the interstitial spaces of the lattice to form interstitial doping.

[0015] The prepared zinc oxide anode material doped with group IIIA metal ions can be used as an anode active material in zinc-nickel batteries.

[0016] Beneficial Effects: This invention provides a negative electrode material of zinc oxide doped with Group IIIA metal ions, its preparation method, and its application. The method involves molten salt-assisted calcination of zinc oxide doped with Group IIIA metal ions. Calcining zinc oxide with aluminum-containing or indium-containing compound precursors in a molten salt environment induces minute deformations in the zinc oxide lattice. These deformations alter the band gap of zinc oxide, thus affecting its electrochemical properties. In the high-temperature molten salt environment, the diffusion rate of reactant ions is faster than in the solid state, allowing them to migrate, collide, and react rapidly, thereby shortening the reaction time and improving the reaction rate and completeness. Furthermore, in the molten salt medium, the metal ion source is fully dispersed and dissolved, and the metal ions can be uniformly distributed in the reaction system. Based on these principles, the introduced metal ions, under the action of molten salt, can effectively occupy the positions of zinc ions in the zinc oxide lattice, forming substitutional doping, or fill the lattice interstices, forming interstitial doping. This alters the electronic structure of ZnO, improves its conductivity, and exhibits higher discharge specific capacity and good cycle stability. The modified ZnO possesses both excellent conductivity and prevents Zn from being absorbed by the metal. 2+ The dissolution in an alkaline environment greatly alleviates the dissolution of the zinc anode, thus providing strong support for the development and application of nickel-zinc battery systems in a liquid-rich environment. Moreover, this invention has the advantages of fewer process steps, lower raw material costs, extremely short synthesis time, low energy consumption, environmental friendliness, safety and non-toxicity, and excellent performance, making it suitable for large-scale production. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the molten salt-assisted method for Al / ZnO composite materials in an embodiment of the present invention; Figure 2 The X-ray diffraction patterns of (a) Al / ZnO and (b) In / ZnO composite materials in the embodiments of the present invention are shown. Figure 3 These are SEM images of (a) Al / ZnO and (b) In / ZnO composite materials in the embodiments of the present invention; Figure 4 Cyclic stability diagrams of zinc-nickel batteries composed of composite materials from (a) Example 1 and Comparative Example 1, and (b) Example 2 and Comparative Example 2. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments: Because commercial zinc oxide has a large crystal size and many impurities, it is not conducive to doping. The zinc oxide used below was synthesized in the laboratory using the oxalic acid coprecipitation method. The synthesis steps are as follows: zinc sulfate is dissolved in water and stirred in an oil bath at 80°C for one hour. Then, oxalic acid solution is slowly added dropwise to a round-bottom flask containing the solution using a peristaltic pump. After ten hours of reaction, the resulting precursor is collected by centrifugation, dried, and calcined in a muffle furnace to obtain ZnO. Example 1

[0019] like Figure 1 As shown, the preparation method of aluminum-doped zinc oxide negative electrode material includes the following steps: 1g of zinc oxide and 0.057g of aluminum oxide were mixed and dry-ground. A small amount of ethanol was added, and the mixture was stirred and ground thoroughly at room temperature. After drying, it was ground again until homogeneous to obtain a mixture. The mixture was placed in a muffle furnace and calcined at 400℃ for four hours to obtain a precursor. The above precursor was mixed with anhydrous strontium chloride at a mass ratio of 1:2, ethanol was added, and the mixture was ground. After drying, it was ground until homogeneous and placed in a crucible, which was then placed in a muffle furnace. The temperature was first increased to 900℃ at a rate of 2℃ per minute and held for 4 hours. Then, the temperature was increased to 1150℃ at a rate of 1℃ per minute and held for 10 hours for calcination. The calcined product was washed with deionized water and filtered until residual molten salt was removed. The final product was obtained after vacuum drying.

[0020] The XRD pattern of the prepared aluminum-doped zinc oxide composite material is as follows: Figure 2 As shown in (a), the aluminum-doped zinc oxide prepared by the molten salt-assisted method showed characteristic peaks, indicating that aluminum ions were doped into the zinc oxide structure.

[0021] Figure 3 (a) is a SEM image of the aluminum-doped zinc oxide composite material, showing the crystal morphology of the aluminum-doped zinc oxide after molten salt assisted calcination. It exhibits a regular polyhedral block structure with clear edges and planes. The surface is relatively dense and smooth, with only a small number of fine particles attached, indicating that the crystal growth is relatively complete and the crystallinity is high. This shows that Al doping promotes the directional growth of ZnO along specific crystal planes, forming a regular polyhedral block structure. Example 2

[0022] The preparation method of indium-doped zinc oxide anode material includes the following steps: 1g of zinc oxide and 0.0136g of indium oxide were mixed and dry-ground. A small amount of ethanol was added, and the mixture was stirred and ground thoroughly at room temperature. After drying, it was ground again until homogeneous to obtain a mixture. The mixture was placed in a muffle furnace and calcined at 400℃ for four hours to obtain a precursor. The above precursor was mixed with anhydrous strontium chloride at a mass ratio of 1:2, ethanol was added, and the mixture was ground. After drying, it was ground until homogeneous and placed in a crucible, which was then placed in a muffle furnace. The temperature was first increased to 900℃ at a rate of 2℃ per minute and held for 4 hours. Then, the temperature was increased to 1150℃ at a rate of 1℃ per minute and held for 10 hours for calcination. The calcined product was washed with deionized water and filtered until residual molten salt was removed. The final product was obtained after vacuum drying.

[0023] The XRD pattern of the prepared indium-doped zinc oxide composite material is as follows: Figure 2 As shown in (b), the indium-doped zinc oxide prepared by the molten salt-assisted method showed characteristic peaks, indicating that indium ions were doped into the zinc oxide structure.

[0024] Figure 3 (b) is a SEM of the indium-doped zinc oxide composite material, showing the crystal morphology of the indium-doped zinc oxide after molten salt assisted calcination. It exhibits a spherical particle structure with no obvious edges and a rounded overall morphology. It belongs to the aggregated state of spherical or ellipsoidal particles with a relatively dense surface. However, there are a few gaps between the spherical particles. Some particles have fine protrusions or small particles attached to their surface, indicating that the doping of In may change the crystal plane energy of ZnO, making it tend to grow isotropically and eventually form spherical particles.

[0025] Comparative Example 1 1g of zinc oxide and 0.057g of aluminum oxide were mixed and dry-ground. A small amount of ethanol was added, and the mixture was stirred and ground thoroughly at room temperature. After drying, it was ground again until homogeneous to obtain a mixture. The mixture was placed in a muffle furnace and calcined at 400℃ for four hours to obtain a precursor. The precursor was placed in a crucible and then placed in a muffle furnace. The temperature was first increased to 900℃ at a rate of 2℃ per minute and held for 4 hours. Then, the temperature was increased to 1150℃ at a rate of 1℃ per minute and held for 10 hours for calcination. After vacuum drying, the final product was obtained.

[0026] Without adding molten salt, and with other conditions the same as in Example 1, the resulting product exhibited severe particle agglomeration.

[0027] Figure 4(a) shows the cycling stability of zinc-nickel batteries assembled with the products of Example 1, Comparative Example 1, and commercial zinc oxide as negative electrode materials and Ni(OH)2 as positive electrode at 1C rate under alkaline conditions. The zinc-nickel battery assembled with the products of Comparative Example 1 and commercial zinc oxide as negative electrode materials could not cycle stably, indicating that Example 1 successfully incorporated aluminum into zinc oxide through the molten salt-assisted method, thereby improving its conductivity and thus its cycling stability.

[0028] Comparative Example 2 1g of zinc oxide and 0.0136g of indium oxide were mixed and dry-ground. A small amount of ethanol was added, and the mixture was stirred and ground thoroughly at room temperature. After drying, it was ground again until homogeneous to obtain a mixture. The mixture was placed in a muffle furnace and calcined at 400℃ for four hours to obtain a precursor. The precursor was placed in a crucible and then placed in a muffle furnace. The temperature was first increased to 900℃ at a rate of 2℃ per minute and held for 4 hours. Then, the temperature was increased to 1150℃ at a rate of 1℃ per minute and held for 10 hours for calcination. After vacuum drying, the final product was obtained.

[0029] Without adding molten salt, and with other conditions the same as in Example 2, the resulting product exhibited severe particle agglomeration.

[0030] Figure 4 (b) shows the cycling stability of zinc-nickel batteries assembled with the products of Example 2 and Comparative Example 2 and commercial zinc oxide as negative electrode materials and Ni(OH)2 as positive electrode under alkaline conditions at a 2C rate. The zinc-nickel battery assembled with the products of Comparative Example 2 and commercial zinc oxide as negative electrode materials could not cycle stably, indicating that Example 2 successfully doped indium into zinc oxide through the molten salt-assisted method, thereby improving its conductivity and thus improving its cycling stability.

[0031] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a negative electrode material of zinc oxide doped with Group IIIA metal ions, characterized in that, Includes the following steps: (1) Zinc oxide is mixed with a compound containing Group IIIA metals in a certain proportion and then ground evenly to obtain a mixture; (2) The mixture was calcined to obtain the precursor; (3) Mix the precursor and molten salt in a certain proportion, grind them evenly, and then calcine them; (4) The final product is obtained by removing the residual molten salt from the calcined product.

2. The method for preparing the negative electrode material of group IIIA metal ion-doped zinc oxide according to claim 1, characterized in that, The mass of the doped Group IIIA metal ions accounts for 0.1%-10% of the total mass of the final product.

3. The method for preparing the negative electrode material of group IIIA metal ion-doped zinc oxide according to claim 1 or 2, characterized in that, The compound containing Group IIIA metals is an aluminum- or indium-containing compound or element.

4. The method for preparing the negative electrode material of group IIIA metal ion-doped zinc oxide according to claim 3, characterized in that, The aluminum-containing compound is one of aluminum oxide, aluminum nitrate, and aluminum chloride, and the aluminum-containing element is aluminum powder; the indium-containing compound is one of indium oxide, indium nitrate, and indium acetate, and the indium-containing element is indium powder.

5. The method for preparing the negative electrode material of group IIIA metal ion-doped zinc oxide according to claim 1, characterized in that, The mass of the molten salt is 2-10 times that of the precursor.

6. The method for preparing the negative electrode material of group IIIA metal ion-doped zinc oxide according to claim 1 or 5, characterized in that, The molten salt is one or more of anhydrous strontium chloride, magnesium chloride, and calcium chloride.

7. The method for preparing the negative electrode material of group IIIA metal ion-doped zinc oxide according to claim 1, characterized in that, In step (2), calcination is carried out at 400℃-600℃ for 4-8 hours.

8. The method for preparing the negative electrode material of group IIIA metal ion-doped zinc oxide according to claim 1, characterized in that, In step (3), the calcination is divided into two stages: first, the temperature is raised to 700℃-900℃ at a rate of 2℃-10℃ per minute and held for 4-6 hours; then, the temperature is raised to 1000℃-1150℃ at a rate of 1℃-5℃ per minute and held for 10-12 hours.

9. The negative electrode material of zinc oxide doped with Group IIIA metal ions prepared by the method according to any one of claims 1-8, characterized in that, The negative electrode material is composed of zinc oxide and a compound containing Group IIIA metals. The Group IIIA metal ions occupy the positions of zinc ions in the zinc oxide lattice, forming substitutional doping or filling the interstitial spaces to form interstitial doping.

10. The application of the negative electrode material of zinc oxide doped with Group IIIA metal ions as described in claim 9, characterized in that, The zinc oxide anode material doped with group IIIA metal ions is used as an anode active material in zinc-nickel batteries.

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