Modified zinc powder, preparation method, negative electrode material and zinc battery

Abstract

The application belongs to the technical field of zinc batteries, and particularly relates to modified zinc powder, a preparation method, a negative electrode material and a zinc battery. The zinc powder is composed of zinc, indium, bismuth, oxygen elements and inevitable impurities; the content of zinc is 97.87-99.9wt%, the content of indium is 200-700ppm, the content of bismuth is 200-600ppm, and the oxygen content is 0.01-2.0wt% in terms of mass percentage; the surface of the modified zinc powder is treated by oxidation and then weak acid etching to form an oxidation layer with a surface relief structure. The scheme provided in the application can effectively inhibit the side reaction of the zinc negative electrode, can improve the cycle stability and capacity retention rate under high discharge depth, and can improve the electrode reaction kinetics performance under high load conditions, and is particularly suitable for zinc battery application scenarios with high discharge depth and ultra-thick electrodes.

Description

Technical Field

[0001] This application belongs to the field of zinc battery technology, specifically relating to a modified zinc powder, a preparation method, a negative electrode material, and a zinc battery. Background Technology

[0002] Rechargeable zinc batteries possess numerous advantages, including high safety, environmental friendliness, low cost, high power density, and a wide operating temperature range, making them highly promising for applications in energy storage, low-speed electric vehicles, and automotive starting power supplies. Taking an alkaline zinc-nickel battery as an example, the working principle of a zinc battery is explained: A zinc-nickel secondary battery consists of a nickel positive electrode, a zinc negative electrode, and an electrolyte. The positive electrode active material is Ni(OH) / NiOOH, the negative electrode active material is ZnO / Zn, and the electrolyte is a KOH solution saturated with ZnO. During charging, Ni(OH) loses electrons to become NiOOH, while ZnO gains electrons to become Zn. The discharge process involves the opposite reaction direction. The KOH aqueous solution in the electrolyte plays a crucial role in providing ion migration and charge transport during the charging and discharging reactions of the zinc-nickel battery.

[0003] In alkaline electrolytes, the zinc anode undergoes a solid-liquid-solid phase transition. First, during charging, zinc salts dissolved in the electrolyte are reduced and deposited on the surface of the zinc anode. In the later stages of charging, zinc dendrites easily form, leading to battery capacity decay and internal short circuits. Second, the zinc in the anode forms micro-cells with the cathode material in the alkaline electrolyte, causing corrosion and dissolution of the zinc anode, reducing its effective capacity, and triggering problems such as gas generation, leakage, and battery swelling. Finally, when the dissolved zinc oxide in the electrolyte reaches saturation, concentration polarization occurs, resulting in a higher zinc salt concentration at the bottom and a relatively lower concentration at the top. During discharge, the active material at the top of the electrode is more likely to participate in the reaction, causing the active material to deposit in the lower middle part of the electrode, ultimately leading to electrode deformation. These problems degrade the battery's cycle performance and power density, hindering the development and application of rechargeable zinc batteries.

[0004] To address the aforementioned issues, existing zinc anode materials generally employ doping modification techniques with alloying elements such as In, Bi, Al, and Ca to suppress gas evolution by increasing the hydrogen evolution overpotential. This can alleviate side reaction problems to some extent under conventional discharge depths and thin electrode scenarios. However, in practical applications with high discharge depths and ultra-thick electrodes, a dense zinc oxide passivation layer forms on the surface of the zinc anode material during charge and discharge, hindering further electrochemical reactions of the active materials. This leads to decreased electrode activity and power density decay. Optimizing the alloying element composition alone cannot simultaneously achieve both gas evolution suppression and kinetic performance under high loads, becoming a core bottleneck limiting the large-scale application of zinc batteries. Summary of the Invention

[0005] The purpose of this application is to solve some of the technical problems of the prior art and to provide a modified zinc powder. Through the oxide layer with a surface undulation structure, it can effectively suppress the side reactions of the zinc anode, improve the cycle stability and capacity retention rate under high discharge depth, and improve the electrode reaction kinetics performance under high load conditions. It is especially suitable for zinc battery application scenarios with high discharge depth and ultra-thick electrodes.

[0006] Another objective of this application is to provide a method for preparing the above-mentioned modified zinc powder, which has the advantages of simple process, controllable parameters, and easy large-scale production.

[0007] Another objective of this application is to provide a negative electrode material comprising the above-mentioned modified zinc powder, and a zinc battery using the negative electrode material.

[0008] To achieve the above-mentioned objectives, this application adopts the following technical solution: The first aspect of this application provides a modified zinc powder, composed of zinc, indium, bismuth, oxygen, and unavoidable impurities; by mass percentage, the zinc content is 97.87~99.9 wt%, the indium content is 200~700 ppm, the bismuth content is 200~600 ppm, and the oxygen content is 0.01~2.0 wt%. The surface of the modified zinc powder is first oxidized and then etched with a weak acid to form an oxide layer with a surface undulation structure.

[0009] In some embodiments, the modified zinc powder has a particle size of 20-300 μm and the oxide layer has a thickness of 10-300 nm.

[0010] In some embodiments, the modified zinc powder has a particle size of 80-160 μm and the oxide layer has a thickness of 50-200 nm.

[0011] In some embodiments, the indium content is 300-600 ppm, the bismuth content is 300-500 ppm, and the oxygen content is 0.05-0.5 wt%.

[0012] A second aspect of this application provides a method for preparing modified zinc powder, comprising the following steps: (1) Zinc powder containing indium and bismuth was placed in a hydrogen peroxide solution and subjected to ultrasonic oxidation treatment; (2) Wash the zinc powder after oxidation treatment, and then place the zinc powder in a 0.01~2 mol / L weak acid solution. The stirring time is 5~60 min. (3) The zinc powder treated with weak acid was filtered, washed and dried to obtain the modified zinc powder.

[0013] In some embodiments, the hydrogen peroxide solution has a mass percentage concentration of 10-30 wt%, and the ultrasonic oxidation treatment takes 12-60 min.

[0014] In some embodiments, the weak acid is at least one of citric acid, sodium citrate, and potassium citrate.

[0015] A third aspect of this application provides a negative electrode material comprising the above-described modified zinc powder, or comprising modified zinc powder prepared by the above-described preparation method.

[0016] The fourth aspect of this application provides a zinc battery comprising the aforementioned negative electrode material.

[0017] Compared with the prior art, this application has the following beneficial effects: (1) By utilizing the oxide layer with surface undulations, this application can solve the problems of side reactions and activity decay under high load in the zinc anode: the surface oxide layer acts as a physical barrier, which can slow down the spontaneous reaction between zinc and electrolyte, and is beneficial to reducing side reactions such as corrosion and hydrogen evolution; while the surface undulations obtained by acid etching can increase the active specific surface area, optimize the ion transport path, and thus improve the reaction kinetics. The synergistic effect of the two ensures the excellent cycle stability of the battery at high discharge depth.

[0018] (2) The preparation method of this application adopts an irreversible two-step process of oxidation followed by weak acid etching. The process is simple, the parameters are controllable, no complex equipment is required, and large-scale production from gram level to ten kilogram level can be achieved. The production cost is low and the product consistency is good.

[0019] (3) The negative electrode material of this application has the effect of improving cycle life under discharge depth and reducing capacity decay rate. Under ultra-thick electrode, it can improve discharge specific capacity, which is significantly better than the performance level of existing ordinary commercial zinc powder. Attached Figure Description

[0020] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.

[0021] Figure 1 This is a comparison of SEM images of the modified zinc powder prepared in Example 1 of this application and commercial zinc powder; Figure 2 This is a SEM image of the modified zinc powder prepared in Example 1 of this application; Figure 3 Linear scanning voltammetry curves of the modified zinc powder prepared in Example 1 of this application and commercial zinc powder; Figure 4Tafel curves of the modified zinc powder prepared in Example 1 of this application and commercial zinc powder; Figure 5 This is a comparison chart of battery charge-discharge curves of the modified zinc powder prepared in Example 1 of this application and commercial zinc powder; Figure 6 Battery stability of the modified zinc powder prepared in Example 2 of this application and commercial zinc powder at 40% DOD; Figure 7 The stability of ultrathick electrodes prepared by the modified zinc powder in Example 3 of this application and commercial zinc powder; Figure 8 The stability of the modified zinc powder prepared in Example 4 of this application compared with commercial zinc powder at 60% DOD; Figure 9 SEM image of the zinc powder prepared for Comparative Example 1; Figure 10 SEM image of the zinc powder prepared for Comparative Example 2; Figure 11 SEM image of the zinc powder prepared for Comparative Example 3. Detailed Implementation

[0022] Preferred embodiments of the present application will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0023] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0024] Existing zinc anode materials generally employ doping modification techniques with alloying elements such as In, Bi, Al, and Ca to suppress gas evolution by increasing the hydrogen evolution overpotential. This can alleviate side reaction problems to some extent under conventional discharge depths and thin electrode scenarios. However, in practical applications with high discharge depths and ultra-thick electrodes, a dense zinc oxide passivation layer forms on the surface of the zinc anode material during charge and discharge, hindering further electrochemical reactions of the active materials. This leads to decreased electrode activity and power density decay. Optimizing the alloying element composition alone cannot simultaneously achieve both gas evolution suppression and kinetic performance under high loads, becoming a core bottleneck limiting the large-scale application of zinc batteries.

[0025] To address the aforementioned issues, this application proposes a modified zinc powder. Through an oxide layer with a surface undulation structure, it can effectively suppress side reactions of the zinc anode, improve cycle stability and capacity retention at high discharge depths, and enhance electrode reaction kinetics under high load conditions. It is particularly suitable for zinc battery applications with high discharge depths and ultra-thick electrodes.

[0026] Specifically, the modified zinc powder is composed of zinc, indium, bismuth, oxygen, and unavoidable impurities; by mass percentage, the zinc content is 97.87~99.99 wt%, the indium content is 200~700 ppm, the bismuth content is 200~600 ppm, and the oxygen content is 0.01~2.0 wt%. The surface of the modified zinc powder is first oxidized and then etched with a weak acid to form an oxide layer with a surface undulation structure.

[0027] In this embodiment, the main role of indium in the zinc anode material is to suppress dendrite growth and mitigate side reactions. First, indium has a high affinity for zinc atoms (adsorption energy higher than that of the zinc substrate), which lowers the nucleation barrier for zinc deposition, guiding uniform zinc ion deposition and thus suppressing dendrite formation. Simultaneously, indium has a high hydrogen evolution overpotential and good chemical inertness, effectively mitigating the corrosion reaction of zinc in the electrolyte, reducing dead zinc formation and hydrogen evolution. Furthermore, after modifying the zinc surface with an indium layer, a stable solid-liquid interface can be constructed, regulating the zinc ion flux distribution, improving electric field uniformity, and further enhancing cycle stability. Finally, indium can improve anodic dissolution activity and alter surface passivation behavior. Specifically, the indium content in the zinc powder is 200–700 ppm. If the indium content is below 200 ppm, the gas evolution suppression effect is insufficient; if it is above 700 ppm, it will significantly increase raw material costs and exacerbate surface roughening and dendrite tendency. In a preferred embodiment, the indium content is 300–600 ppm.

[0028] In this embodiment, the main functions of bismuth in the zinc anode material are to suppress dendrite growth, inhibit hydrogen evolution reaction, improve coulombic efficiency, and enhance cycle stability. Firstly, bismuth has low surface energy and good conductivity, allowing it to continuously float on the electrode surface during zinc deposition, limiting the lateral migration of zinc atoms, reducing the nucleation overpotential, and promoting dense, isotropic zinc deposition, thereby effectively suppressing dendrite formation. Simultaneously, the bismuth layer can form a Bi-Zn-Bi triangular coordination structure with zinc, enhancing the coordination of Zn... 2+The bismuth adsorbs and repels harmful species such as water molecules and sulfate ions, inhibiting hydrogen evolution reaction and corrosion. Furthermore, adding trace amounts of bismuth to zinc can form a solid solution; the lattice distortion of bismuth promotes the formation of a dense passivation film on the zinc surface, significantly improving charge transfer resistance, thus reducing hydrogen evolution and improving corrosion inhibition efficiency. In specific implementations, the bismuth content in the zinc powder is 200-600 ppm. If the bismuth content is below 200 ppm, the corrosion inhibition effect is not significant; above 600 ppm, localized alloy phase segregation is easily formed, leading to uneven reaction on the zinc surface. In a preferred embodiment, the bismuth content is 300-500 ppm.

[0029] In this embodiment, oxygen mainly exists in the form of zinc oxide within the oxide layer on the surface of the zinc powder. The oxygen content can be controlled by adjusting the mass percentage concentration of the hydrogen peroxide solution and the ultrasonic oxidation treatment time. In some embodiments, the proportion of spherical particles in the zinc powder is not less than 70%. The spherical morphology can increase the packing density of the zinc powder, reduce the difficulty of electrode processing, and at the same time reduce the surface tip effect and inhibit dendrite growth. Therefore, this application selects zinc powder with a particle size in the range of 20~300μm. When the particle size is less than 20μm, the specific surface area of ​​the zinc powder is too large, the number of side reaction active sites increases, and the gas evolution will increase; when the particle size is greater than 300μm, the reaction kinetics performance is insufficient, and the polarization phenomenon is severe at high magnification. Through the above technical solution, this application can form an oxide layer with a surface undulation structure on the surface of zinc powder. In specific implementation, the oxide layer thickness can be controlled to be 10~300nm, preferably 50~200nm. If the thickness is less than 10 nm, a continuous passivation protective film cannot be formed, and the effect of suppressing side reactions is limited; when the thickness is greater than 300 nm, the electron and ion transport impedance increases significantly, and the electrode activity decreases.

[0030] In this embodiment, unavoidable impurities mainly refer to trace amounts of metallic impurities such as Fe, Pb, and Cd carried in the raw zinc powder, and their total content is usually less than 0.01 wt%.

[0031] This application also proposes a method for preparing modified zinc powder, which employs a two-step irreversible process of oxidation followed by acid etching, including the following steps: (1) Disperse spherical zinc powder containing indium and bismuth in an oxidizing medium for oxidation treatment to form a uniform oxide layer on the surface of the zinc powder.

[0032] Furthermore, the oxidizing medium includes, but is not limited to, hydrogen peroxide solution, oxygen, air, and other oxidants that can oxidize the zinc surface to form an oxide layer of controllable thickness. In this application, hydrogen peroxide solution is preferred because its reaction conditions are mild, the oxidation rate is controllable, and the reaction products are only water and zinc oxide, without the introduction of impurities. Moreover, the required equipment is simple and the investment in fixed facilities is low.

[0033] When hydrogen peroxide solution is used as the oxidation medium, its mass percentage concentration is 10-30 wt%, the ultrasonic oxidation treatment time is 12-60 min, and the ultrasonic power can be set to 100-500 W with a frequency of 40 kHz. Ultrasonic-assisted treatment during the oxidation process ensures sufficient contact between the oxidant and the zinc powder surface, avoiding uneven local oxidation. Simultaneously, the cavitation effect of ultrasound can regulate the density of the oxide layer, providing a basis for subsequent acid etching to form an oxide layer with surface undulations. Hydrogen peroxide concentration is positively correlated with the oxidation rate. When the concentration is below 10 wt%, the oxidation rate is too slow, requiring an excessively long treatment time to achieve the target oxide layer thickness. When the concentration is above 30 wt%, the oxidation reaction is violent, making it difficult to precisely control the oxide layer thickness and easily leading to localized over-oxidation. Furthermore, the stability of the hydrogen peroxide solution itself is highly uncertain, making it difficult to control the actual concentration during subsequent ultrasonic oxidation. Correspondingly, oxidation time is negatively correlated with hydrogen peroxide concentration. When using high-concentration hydrogen peroxide, the treatment time can be appropriately shortened, while when using low-concentration hydrogen peroxide, the treatment time needs to be appropriately extended to achieve precise control of the oxide layer thickness.

[0034] (2) Wash the zinc powder after oxidation treatment, and then place the zinc powder in a 0.01~2 mol / L weak acid solution and stir for 5~60 min.

[0035] Furthermore, the weak acid is selected from any one or more combinations of citric acid, sodium citrate, and potassium citrate. All of the above weak acids can undergo mild complexation or oxidation reactions with zinc oxide, which can achieve controllable etching of the oxide layer. At the same time, the reaction rate with the zinc substrate is extremely slow, which can avoid excessive corrosion of the zinc substrate and ensure the yield of zinc powder.

[0036] Specifically, citric acid and citrates react with zinc oxide to form soluble zinc citrate complexes, which are easily and completely removed by water washing, leaving no impurities on the zinc powder surface and avoiding adverse effects on subsequent battery performance. Simultaneously, citric acid / citrates have mild acidity and a stable reaction rate, resulting in a uniform micro-nano textured surface on the oxide layer after etching, suitable for applications requiring high rate performance. Furthermore, sodium citrate and potassium citrate are buffered weak acids with minimal pH fluctuations, offering higher process stability and suitability for large-scale production. In practice, if the weak acid concentration is below 0.01 mol / L or the processing time is less than 3 minutes, the etching effect is insufficient, making it difficult to form a surface textured structure. If the weak acid concentration is above 2 mol / L or the processing time is longer than 150 minutes, over-etching can lead to complete dissolution of the oxide layer, losing its passivation protection and causing minor corrosion of the zinc substrate, reducing zinc powder yield. The preferred weak acid treatment time in this application is 5-60 minutes, and the stirring speed is 200-500 rpm. During the etching process, stirring enhances mass transfer, ensuring uniform etching rate in all areas of the zinc powder surface and avoiding local over-etching or under-etching.

[0037] (3) The zinc powder treated with weak acid was filtered, washed and dried to obtain the modified zinc powder.

[0038] Furthermore, the washing process involves multiple rinses with deionized water until the pH of the filtrate is neutral, preventing residual acid from causing self-corrosion of the zinc powder during storage.

[0039] Furthermore, vacuum drying is employed, with the drying temperature controlled at 60~80℃ to avoid changes in the oxide layer structure caused by high temperatures, while also preventing excessive oxidation of the zinc powder surface.

[0040] This application also provides a zinc battery comprising the aforementioned negative electrode material containing modified zinc powder; the zinc battery may be an aqueous zinc battery or a non-aqueous zinc battery, and may be adapted to use alkaline, acidic, neutral or organic electrolytes.

[0041] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0043] The high-purity commercial zinc powder used in the embodiments and comparative examples of this application has a purity of 99.99%. The nominal purity of 99.99% means that the total content of useful elements such as zinc, indium, and bismuth is not less than 99.99%, and the content of unavoidable impurities is less than 0.01%.

[0044] Example 1 The modified zinc powder in this embodiment is prepared according to the following steps: (1) Take 20g of high-purity commercial zinc powder with an indium content of 500ppm, a bismuth content of 400ppm, and a D90 of 40μm and disperse it in a 20wt% H2O2 solution. Perform ultrasonic treatment for 20min to carry out oxidation treatment and form an oxide layer on the surface of the zinc powder. (2) Wash the oxidized zinc powder with deionized water three times, then place it in 0.1M citric acid solution and stir for 30 minutes to etch part of the oxide layer; (3) After filtration, wash with deionized water three times and vacuum dry at 60°C for 12 hours to obtain modified zinc powder.

[0045] (4) Zinc powder performance test: The modified zinc powder prepared in this embodiment, as well as commercial zinc powder containing indium and bismuth of the same specifications, were subjected to scanning electron microscopy (SEM), linear scanning voltammetry (LSV), Tafel curve analysis, and oxygen content testing. The SEM results are shown below. Figure 1 and Figure 2 As shown, the LSV test results are as follows: Figure 3The Tafel test results can be found here. Figure 4 The results of the oxygen content test are shown in Table 1. Figure 1 This is a SEM image of the modified zinc powder prepared in Example 1 of this application. Figure 2 This is a comparison of SEM images of the modified zinc powder prepared in Example 1 of this application and commercial zinc powder. Figure 1 and Figure 2 In the left image, commercial zinc powder treated with oxidation and weak acid etching has irregularly arranged small spheres distributed on its surface. Figure 2 Commercial zinc powder (right image) has a smooth and flat surface with no obvious small ball structure. Figure 3 This indicates that, at the same current density, the hydrogen evolution potential of the modified zinc powder (black curve) is significantly negative compared to that of commercial zinc powder (red curve). For example, at a current density of -120 mA / cm², the hydrogen evolution potential is significantly higher. 2 At that time, the modified zinc powder was about -2.0V, which is 50mV negatively shifted from the hydrogen evolution potential of commercial zinc powder. This indicates that the oxide layer with undulating surface structure can increase the overpotential of hydrogen evolution reaction and play a role in inhibiting hydrogen evolution side reactions. Figure 4 The results show that the corrosion current density of modified zinc powder (black curve) is significantly lower than that of commercial zinc powder (red curve), indicating that the introduction of the undulating oxide layer can effectively reduce the self-corrosion rate of zinc anode material, significantly alleviate the corrosion problem of zinc electrode in alkaline electrolyte, and improve the storage stability and cycle life of anode.

[0046] Table 1: Performance Test Table of Example 1 and Commercial Zinc Powder

[0047] (5) Battery samples and testing: The modified zinc powder prepared in this embodiment was mixed with conductive carbon black and binder at a mass ratio of 8:1:1, and then rolled into a film and pressed onto a tin-plated copper current collector to prepare a negative electrode sheet. Using NiOOH as the positive electrode, a 6 mol / L KOH and 0.1 mol / L LiOH aqueous solution containing saturated ZnO as the electrolyte, and a glass fiber membrane as the separator, a coin-type alkaline zinc-nickel battery was assembled. Electrochemical performance tests were conducted, and the test results are as follows: Figure 5 As shown. Figure 5 The figures show a comparison of discharge curves of batteries assembled with modified zinc powder prepared in Example 1 and commercial zinc powder at different cycle numbers; the left figure shows the discharge curve of the control battery with commercial zinc powder, and the right figure shows the discharge curve of the battery prepared with modified zinc powder in Example 1 of this application. The horizontal axis represents the specific discharge capacity of the battery, and the vertical axis represents the operating voltage of the battery. Figure 5It can be seen that the discharge specific capacity of commercial zinc powder batteries has decayed to 275 mAh / g after 50 cycles, and the discharge plateau voltage has dropped significantly. However, the battery using the modified zinc powder of Example 1 of this application still maintains a discharge specific capacity of over 440 mAh / g after 50 cycles, with a stable discharge plateau and a capacity retention rate that is significantly better than that of the commercial zinc powder control battery. This proves that the modified zinc powder of this application can effectively improve the capacity performance and voltage stability under high cycle counts.

[0048] Example 2 The modified zinc powder in this embodiment is prepared according to the following steps: (1) Take 20g of high-purity commercial zinc powder with an indium content of 500ppm, a bismuth content of 400ppm, and a D90 of 75μm and disperse it in a 10wt% H2O2 solution. Then, perform an oxidation treatment by ultrasonic treatment for 30min. (2) Wash the oxidized zinc powder three times with deionized water, and then place it in a 0.15M citric acid solution and stir for 20 minutes. (3) Filter, wash and vacuum dry to obtain modified zinc powder.

[0049] The modified zinc powder prepared in this embodiment was assembled into an alkaline zinc-nickel battery according to the electrode preparation method in Example 1. The electrode active material loading was 53 mg / cm³. 2 Cyclic performance was tested using a 0.5C current density at 40% depth of discharge (DOD, corresponding to a discharge specific capacity of 330 mAh / g). The test results are as follows: Figure 6 As shown. Figure 6 This graph compares the cycle performance of batteries assembled with the modified zinc powder of Example 2 and commercial zinc powder containing indium and bismuth of the same specification at 40% depth of discharge. The horizontal axis represents the number of cycles, and the vertical axis represents the specific capacity of discharge. The test conditions were: electrode loading of approximately 53 mg / cm³. 2 The test current was 0.5C, the electrolyte was a lean electrolyte system, and the depth of discharge was controlled at 40% (corresponding to 330 mAh / g).

[0050] Depend on Figure 6 As can be seen, after the first 5 activation cycles, the battery enters the stable cycling stage. The battery using Example 2 maintains a stable discharge specific capacity of over 320 mAh / g after 80 cycles, and a capacity retention rate of 89% after 120 cycles. In contrast, the control battery using commercial zinc powder experiences rapid capacity decay after 30 cycles, with a discharge specific capacity of only 230 mAh / g and a capacity retention rate of only 70% after 120 cycles. These results demonstrate that the modified zinc powder of this application can significantly improve the cycle stability of the battery under a high depth of discharge condition of 40%, effectively alleviating the problem of rapid capacity decay caused by high depth of charge and discharge.

[0051] Example 3 The modified zinc powder in this embodiment is prepared according to the following steps: (1) Take 20g of high-purity commercial zinc powder with an indium content of 500ppm, a bismuth content of 400ppm, and a D90 of 125μm and disperse it in a 20wt% H2O2 solution. Then, perform an oxidation treatment by ultrasonic treatment for 30min. (2) Wash the oxidized zinc powder three times with deionized water, and then place it in a 0.2M citric acid solution and stir for 30 minutes. (3) Filter, wash and vacuum dry to obtain modified zinc powder.

[0052] The modified zinc powder obtained in this embodiment was used to prepare a negative electrode sheet according to the electrode preparation method in Example 1. After assembling it into an alkaline zinc-nickel battery, the cycle performance was tested under the condition of 0.3C current density and 30% depth of discharge (DOD, corresponding to a discharge specific capacity of 247 mAh / g). The test results are as follows. Figure 7 As shown. Figure 7 This is a comparison graph showing the cycling performance of the modified zinc powder prepared in Example 3 and commercial zinc powder containing indium and bismuth of the same specification assembled into an ultra-thick electrode. The horizontal axis represents the number of cycles, and the vertical axis represents the discharge specific capacity. The test conditions were: electrode active material loading of approximately 150 mg / cm³. 2 The test current was 0.3C, and the depth of discharge was controlled at 30% (corresponding to 247 mAh / g).

[0053] Depend on Figure 7 As can be seen, after the first 10 low-current activation stages, the ultra-thick electrode using the modified zinc powder of this application maintained a discharge specific capacity of over 220 mAh / g after cycling stabilization, with no significant capacity decay after 150 cycles. In contrast, the control electrode using commercial zinc powder experienced a rapid capacity drop after 100 cycles, and the discharge specific capacity fell below 100 mAh / g after 120 cycles. These results demonstrate that the modified zinc powder of this application can effectively solve the problems of insufficient utilization of active materials and cycle decay under ultra-thick electrode conditions, significantly improving the capacity utilization and cycle stability of high-load electrodes.

[0054] Example 4 The modified zinc powder in this embodiment is prepared according to the following steps: (1) Take 100g of high-purity commercial zinc powder with an indium content of 500ppm, a bismuth content of 400ppm, and a D90 of 175μm and disperse it in a 20wt% H2O2 solution. Then, perform an oxidation treatment by ultrasonic treatment for 30min. (2) Wash the oxidized zinc powder three times with deionized water, and then place it in a 0.2M citric acid solution and stir for 40 minutes. (3) Centrifuge, filter, wash and vacuum dry to obtain modified zinc powder.

[0055] The modified zinc powder prepared in this embodiment was assembled into an alkaline zinc-nickel battery according to the electrode preparation method in Example 1. Long-cycle performance was tested under the following conditions: rich electrolyte (electrolyte filling amount is 2-3 times the total pore volume of the electrode and separator, with excess free electrolyte); and at 60% depth of discharge (DOD). The test results are as follows: Figure 8 As shown. Figure 8 This graph compares the long-cycle performance of batteries assembled with the modified zinc powder prepared in Example 4 and commercial zinc powder containing indium and bismuth of the same specifications at 60% depth of discharge. The horizontal axis represents the number of cycles, and the vertical axis represents the specific capacity of discharge. The test conditions were: electrode active material loading of 60 mg / cm³. 2 It adopts a rich electrolyte system and controls the depth of discharge to 60%.

[0056] Depend on Figure 8 As can be seen, the battery using the modified zinc powder of this application maintains a stable discharge specific capacity of over 460 mAh / g after 700 cycles at an ultra-high depth of discharge (DOD) of 60%, with no significant capacity decay. In contrast, the control battery using commercial zinc powder exhibits drastic capacity fluctuations after 200 cycles and complete capacity decay after 450 cycles. These results demonstrate that the modified zinc powder of this application can significantly improve cycle stability at ultra-high depths of discharge, overcoming the technical bottleneck of traditional zinc anodes' inability to achieve long-term cycling under high DOD conditions above 60%.

[0057] Example 5 The modified zinc powder in this embodiment is prepared according to the following steps: (1) Take 100g of high-purity commercial zinc powder with an indium content of 500ppm, a bismuth content of 400ppm, and a D90 of 175μm and disperse it in a 20wt% H2O2 solution. Then, perform an oxidation treatment by ultrasonic treatment for 30min. (2) Wash the oxidized zinc powder three times with deionized water, and then place it in a 0.2M sodium citrate solution and stir for 40 minutes. (3) Filter, wash, and vacuum dry at 60°C to obtain modified zinc powder.

[0058] Example 6 The modified zinc powder in this embodiment is prepared according to the following steps: (1) Take 500g of high-purity commercial zinc powder with an indium content of 500ppm, a bismuth content of 400ppm, and a D90 of 125μm and disperse it in a 20wt% H2O2 solution. Then, perform an oxidation treatment by ultrasonic treatment for 45min. (2) Wash the oxidized zinc powder three times with deionized water, and then place it in a 0.2M sodium citrate solution and stir for 60 min. (3) Filter, wash, and vacuum dry at 60°C to obtain modified zinc powder.

[0059] Example 7 The modified zinc powder in this embodiment is prepared according to the following steps: (1) Take 1000g of high-purity commercial zinc powder with an indium content of 500ppm, a bismuth content of 400ppm, and a D90 of 125μm and disperse it in a 30wt% H2O2 solution. Then, perform an oxidation treatment by ultrasonic treatment for 45min. (2) Wash the oxidized zinc powder three times with deionized water, and then place it in a 0.2M potassium persulfate solution and stir for 60 min. (3) Filter, wash, and vacuum dry at 60°C to obtain modified zinc powder.

[0060] Example 8 The modified zinc powder in this embodiment is prepared according to the following steps: (1) Take 2 kg of high-purity commercial zinc powder with an indium content of 500 ppm, a bismuth content of 400 ppm, and a D90 of 125 μm and disperse it in a 30 wt% H2O2 solution. Then, perform an oxidation treatment by ultrasonic treatment for 60 min. (2) Wash the oxidized zinc powder three times with deionized water, and then place it in a 0.2M citric acid solution and stir for 60 minutes. (3) Centrifuge, filter, wash, and vacuum dry at 60°C to obtain modified zinc powder prepared on a large scale.

[0061] Comparative Example 1 Using the same raw materials and oxidation process as in Example 2, but without subsequent weak acid treatment, zinc powder was obtained directly after oxidation and drying. The morphology of the obtained zinc powder was characterized using a scanning electron microscope (SEM). Figure 9 The SEM image of the zinc powder prepared for Comparative Example 1, which has undergone only oxidation treatment, shows that its surface is smooth and without surface undulations, which is significantly different from the surface morphology of the modified zinc powder in Example 1 of this application.

[0062] Comparative Example 2 Comparative Example 2 used the same raw materials as Example 1, without pre-oxidation treatment, and was directly etched in 0.1M citric acid for 30 min. The resulting zinc powder was characterized by scanning electron microscopy (SEM), and the results are as follows. Figure 10 As shown, Figure 10 The SEM image of the zinc powder prepared for Comparative Example 2 with only acid etching shows that there are a large number of irregular pits on its surface, which is significantly different from the surface morphology of the modified zinc powder in Example 1 of this application.

[0063] Comparative Example 3 The same raw materials and process parameters as in Example 1 were used, but weak acid etching was performed first, followed by oxidation. The resulting zinc powder was characterized using a scanning electron microscope (SEM), and the results are as follows: Figure 11 As shown, Figure 11 The SEM image of the zinc powder prepared by acid etching followed by oxidation in Comparative Example 3 shows a significant difference in surface morphology compared to the modified zinc powder in Example 1 of this application.

[0064] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A modified zinc powder, characterized in that, It is composed of zinc, indium, bismuth, oxygen, and unavoidable impurities; by mass percentage, the zinc content is 97.87~99.9 wt%, the indium content is 200~700 ppm, the bismuth content is 200~600 ppm, and the oxygen content is 0.01~2.0 wt%. The surface of the modified zinc powder is first oxidized and then etched with a weak acid to form an oxide layer with a surface undulation structure.

2. The modified zinc powder according to claim 1, characterized in that, The modified zinc powder has a particle size of 20~300μm, and the oxide layer has a thickness of 10~300nm.

3. The modified zinc powder according to claim 2, characterized in that, The modified zinc powder has a particle size of 80~160μm, and the oxide layer has a thickness of 50~200nm.

4. The modified zinc powder according to claim 3, characterized in that, The indium content is 300~600ppm, the bismuth content is 300~500ppm, and the oxygen content is 0.05~0.5wt%.

5. A method for preparing modified zinc powder, characterized in that, The method for preparing the modified zinc powder according to any one of claims 1 to 4 comprises the following steps: (1) Zinc powder containing indium and bismuth was placed in a hydrogen peroxide solution and subjected to ultrasonic oxidation treatment; (2) Wash the zinc powder after oxidation treatment, and then place the zinc powder in a 0.01~2 mol / L weak acid solution. The stirring time is 5~60 min. (3) The zinc powder treated with weak acid was filtered, washed and dried to obtain the modified zinc powder.

6. The preparation method according to claim 5, characterized in that, The hydrogen peroxide solution has a mass percentage concentration of 10-30 wt%, and the ultrasonic oxidation treatment takes 12-60 min.

7. The preparation method according to claim 5, characterized in that, The weak acid is selected from at least one of citric acid, sodium citrate, and potassium citrate.

8. A negative electrode material, characterized in that, It includes the modified zinc powder according to any one of claims 1 to 4, or the modified zinc powder prepared by the preparation method according to any one of claims 5 to 7.

9. A zinc battery, characterized in that, Includes the negative electrode material as described in claim 8.

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