A positive electrode active material for alkaline batteries and a method for producing the same

Abstract

This invention discloses a positive electrode active material for alkaline batteries, belonging to the field of battery material technology. The positive electrode material is made from the following raw materials in parts by weight: 100-120 parts modified manganese dioxide, 0.5-0.8 parts additives, 1-3 parts carbon nanotubes, 0.2-0.4 parts polyvinyl alcohol, and 3-5 parts positive electrode electrolyte. The modified manganese dioxide prepared by this invention has a flower-shaped layered three-dimensional structure, composed of many irregular thin sheets. This structure has high porosity and short diffusion length, providing an efficient transport path for zinc ions, allowing zinc ions to diffuse and migrate more easily within the material, thereby improving the charge / discharge rate and cycle performance of the battery. It can be used as a positive electrode material for alkaline batteries, and its application prospects are particularly broad in secondary zinc-manganese batteries.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to a positive electrode active material for alkaline batteries and its preparation method. Background Technology

[0002] With societal development, energy crises and environmental problems are becoming increasingly severe. Rechargeable batteries, as an emerging environmentally friendly energy storage device, are being widely used, from small portable electronic devices like mobile phones, computers, and digital cameras to large-scale electric vehicles and even large-scale energy storage grids. Against the backdrop of vigorous promotion of energy conservation and environmental protection, various types of batteries, such as lead-acid batteries and lithium-ion batteries, are developing rapidly, and these batteries occupy a large market share. Currently, the reversible capacity of lithium-ion rechargeable batteries can reach 200 mAh·g. -1 Energy density reaches 260Wh·kg -1 The cycle life exceeds 1000 cycles; lead-acid batteries are inexpensive, readily available, and easy to recycle, with a reversible capacity maintained at 100 mAh·g. -1 However, lithium-ion batteries are expensive, have limited lithium resources, and are relatively unsafe, while lead-acid batteries have low energy density, short lifespan, contain heavy metals, and are environmentally unfriendly. Therefore, it is particularly important to develop rechargeable batteries with high capacity, fast charging and discharging, good safety, abundant raw material resources, environmental friendliness, and strong adaptability.

[0003] Common alkaline rechargeable batteries include nickel-iron batteries, nickel-cadmium batteries, nickel-zinc batteries, nickel-metal hydride batteries, zinc-silver batteries, and zinc-manganese batteries. Among these, zinc-manganese rechargeable batteries typically use MnO2 as the positive electrode, Zn as the negative electrode, and KOH solution as the electrolyte. During discharge, the Zn negative electrode undergoes an oxidation reaction, releasing electrons into the external circuit. These electrons move to the MnO2 positive electrode, where a reduction reaction occurs. Inside the battery, ions move between the positive and negative electrodes with the help of the electrolyte. During charging, under the influence of an applied reverse current, the reactions at the positive and negative electrodes proceed in reverse, restoring the active materials at both electrodes to their initial state, and converting electrical energy into chemical energy. Zinc-manganese rechargeable batteries have advantages such as low self-discharge, no memory effect, simple structure, low energy consumption, and environmental friendliness. They not only improve resource utilization but also significantly reduce environmental pollution caused by battery waste. Manganese dioxide, as the positive electrode material, is inexpensive, environmentally friendly, has multiple variable valence states, and possesses strong ion storage performance, making it the most commonly used positive electrode material in traditional zinc-manganese batteries in recent years. Although manganese dioxide (MnO2) has many advantages as a cathode material for zinc-manganese batteries, it still has some problems: (1) The conductivity of MnO2 cathode is poor, which causes the electrochemical reaction to occur only on the electrode surface, greatly limiting the utilization rate of the electrode material; (2) Most MnO2 materials have unstable structures and are prone to conversion to other valence states. During charge and discharge, electrochemically inert Mn3O4 is generated and severe volume expansion occurs, resulting in poor reversibility of deep charge and discharge and unsatisfactory cycle performance. Therefore, further research is urgently needed to find low-cost, structurally stable, and cycle-friendly MnO2 cathode materials suitable for large-scale production to meet market demand. Summary of the Invention

[0004] The purpose of this invention is to provide a positive electrode active material for alkaline batteries, which improves the structural stability and conductivity of the positive electrode material MnO2, thereby further improving the electrochemical performance of the battery material.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] A positive electrode active material for alkaline batteries is made from the following raw materials in parts by weight: 100-120 parts modified manganese dioxide, 0.5-0.8 parts additives, 1-3 parts carbon nanotubes, 0.2-0.4 parts polyvinyl alcohol, and 3-5 parts positive electrode electrolyte.

[0007] Preferably, the modified manganese dioxide is prepared by the following method: 100 ml of 0.5 mol / L manganese sulfate solution is prepared, 12.55 g of ammonium persulfate is added, and the mixture is magnetically stirred until homogeneous. Then, 50 ml of ethylene glycol and 5 mmol of sodium dodecylbenzenesulfonate are added, and the mixture is stirred at room temperature for 30-40 min. Then, 1 mmol of anhydrous copper acetate, 20 mg of urea, and 1 mmol of lithium nitrate are added, and the mixture is stirred for another 10 min. The mixture is then transferred to a microwave hydrothermal reactor, and the temperature is raised to 100 °C. The mixture is kept at this temperature for the reaction. After the reaction is completed, the mixture is cooled to room temperature, centrifuged, and the solid product is washed several times with anhydrous ethanol and deionized water. The precipitate is dried at 80 °C to obtain the modified flower-shaped manganese dioxide.

[0008] Preferably, the specific method for setting the heating rate is to raise the temperature to 100°C within 2 minutes.

[0009] Preferably, the heat preservation reaction time is 5 minutes.

[0010] Preferably, the additive is one of cerium oxide, indium oxide, and neodymium oxide.

[0011] Preferably, the carbon nanotubes are single-walled carbon nanotubes and / or multi-walled carbon nanotubes.

[0012] Preferably, the positive electrode electrolyte is a 35% (w / w) potassium hydroxide aqueous solution.

[0013] The present invention also provides a method for preparing the above-mentioned alkaline battery positive electrode active material, which includes the following steps:

[0014] (1) Preparation of modified manganese dioxide;

[0015] (2) Mix the modified manganese dioxide, additives, carbon nanotubes and polyvinyl alcohol evenly to obtain a mixed powder. Ball mill the mixed powder at a speed of 300-400 r / min for 4-6 hours and then add the positive electrode electrolyte. Mix evenly and vacuum to obtain the positive electrode material. Then, use a slurry mold to coat the material onto a titanium mesh that has been cleaned with alcohol. Dry the titanium mesh in an oven at 60°C for 12 hours and then take it out. Use a cutting machine to cut the titanium foil into positive electrode sheets for use.

[0016] The beneficial effects of this invention are as follows: The modified manganese dioxide prepared by this invention has a flower-shaped layered three-dimensional structure, which is composed of many irregular thin sheets. This structure has high porosity and short diffusion length, providing an efficient transport path for zinc ions, allowing zinc ions to diffuse and migrate more easily in the material, thereby improving the charge-discharge rate and cycle performance of the battery. Simultaneously, copper-lithium ion doping can significantly improve the conductivity of the manganese dioxide material, which helps improve the charge transport efficiency inside the battery, thereby reducing the internal resistance and improving the battery's output performance. The synergistic effect of copper and lithium ions can also improve the conductivity of manganese dioxide and the stability of the manganese dioxide tunnel structure, increase ion and electronic defects, change the effective reaction surface of MnO2, and enhance the electron and ion transport capabilities. It can also promote the kinetics of redox reactions on the material surface, thereby increasing battery capacity. Furthermore, it can better maintain structural integrity during charge-discharge, helping to extend battery life and cycle stability. Therefore, the electrode active material prepared by this invention can be used as a positive electrode material for alkaline batteries, especially showing great promise in secondary zinc-manganese batteries. Attached Figure Description

[0017] Figure 1 This is a SEM image showing the microstructure of the modified manganese dioxide prepared in this invention.

[0018] Figure 2 The graphs show the electrochemical impedance spectroscopy results of different embodiments of the present invention.

[0019] Figure 3 The graph shows the cyclic voltammetry test results of the positive electrode active material in different embodiments of the present invention.

[0020] Figure 4 The graph shows the cycle performance of full cells assembled in different embodiments of the present invention at a 1C rate. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0022] Example 1

[0023] A positive electrode active material for alkaline batteries is made from the following raw materials in parts by weight: 120 parts modified manganese dioxide, 0.8 parts additives, 3 parts carbon nanotubes, 0.4 parts polyvinyl alcohol, and 5 parts positive electrode electrolyte.

[0024] The modified manganese dioxide was prepared by the following method: 100 ml of 0.5 mol / L manganese sulfate solution was prepared, 12.55 g of ammonium persulfate was added, and the mixture was magnetically stirred until homogeneous. Then, 50 ml of ethylene glycol and 5 mmol of sodium dodecylbenzenesulfonate were added, and the mixture was stirred at room temperature for 30-40 min. Then, 1 mmol of anhydrous copper acetate, 20 mg of urea, and 1 mmol of lithium nitrate were added, and the mixture was stirred for another 10 min. The mixture was then transferred to a microwave hydrothermal reactor and the temperature was raised to 100 °C within 2 min. The reactor was kept at this temperature for 5 min. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the solid product was washed several times with anhydrous ethanol and deionized water. The precipitate was dried at 80 °C to obtain the modified flower-shaped manganese dioxide.

[0025] The additive is cerium oxide.

[0026] The carbon nanotubes are single-walled carbon nanotubes.

[0027] The positive electrode electrolyte is a 35% (w / w) potassium hydroxide aqueous solution.

[0028] A method for preparing the above-mentioned alkaline battery positive electrode active material includes the following steps:

[0029] (1) Preparation of modified manganese dioxide;

[0030] (2) Mix the modified manganese dioxide, additives, carbon nanotubes and polyvinyl alcohol evenly to obtain a mixed powder. Ball mill the mixed powder at a speed of 300-400 r / min for 4-6 hours and then add the positive electrode electrolyte. Mix evenly and vacuum to obtain the positive electrode material. Then, use a slurry mold to coat the material onto a titanium mesh that has been cleaned with alcohol. Dry the titanium mesh in an oven at 60°C for 12 hours and then take it out. Use a cutting machine to cut the titanium foil into positive electrode sheets for use.

[0031] Example 2

[0032] A positive electrode active material for alkaline batteries is made from the following raw materials in parts by weight: 100 parts modified manganese dioxide, 0.5 parts additives, 1 part carbon nanotubes, 0.2 parts polyvinyl alcohol, and 3 parts positive electrode electrolyte.

[0033] The modified manganese dioxide was prepared by the following method: 100 ml of 0.5 mol / L manganese sulfate solution was prepared, 12.55 g of ammonium persulfate was added, and the mixture was magnetically stirred until homogeneous. Then, 50 ml of ethylene glycol and 5 mmol of sodium dodecylbenzenesulfonate were added, and the mixture was stirred at room temperature for 30-40 min. Then, 1 mmol of anhydrous copper acetate, 20 mg of urea, and 1 mmol of lithium nitrate were added, and the mixture was stirred for another 10 min. The mixture was then transferred to a microwave hydrothermal reactor and the temperature was raised to 100 °C within 2 min. The reactor was kept at this temperature for 5 min. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the solid product was washed several times with anhydrous ethanol and deionized water. The precipitate was dried at 80 °C to obtain the modified flower-shaped manganese dioxide.

[0034] The additive is indium oxide.

[0035] The carbon nanotubes are multi-walled carbon nanotubes.

[0036] The positive electrode electrolyte is a 35% (w / w) potassium hydroxide aqueous solution.

[0037] A method for preparing the above-mentioned alkaline battery positive electrode active material includes the following steps:

[0038] (1) Preparation of modified manganese dioxide;

[0039] (2) Mix the modified manganese dioxide, additives, carbon nanotubes and polyvinyl alcohol evenly to obtain a mixed powder. Ball mill the mixed powder at a speed of 300-400 r / min for 4-6 hours and then add the positive electrode electrolyte. Mix evenly and vacuum to obtain the positive electrode material. Then, use a slurry mold to coat the material onto a titanium mesh that has been cleaned with alcohol. Dry the titanium mesh in an oven at 60°C for 12 hours and then take it out. Use a cutting machine to cut the titanium foil into positive electrode sheets for use.

[0040] Example 3

[0041] A positive electrode active material for alkaline batteries is made from the following raw materials in parts by weight: 110 parts modified manganese dioxide, 0.7 parts additives, 2 parts carbon nanotubes, 0.3 parts polyvinyl alcohol, and 4 parts positive electrode electrolyte.

[0042] The modified manganese dioxide was prepared by the following method: 100 ml of 0.5 mol / L manganese sulfate solution was prepared, 12.55 g of ammonium persulfate was added, and the mixture was magnetically stirred until homogeneous. Then, 50 ml of ethylene glycol and 5 mmol of sodium dodecylbenzenesulfonate were added, and the mixture was stirred at room temperature for 30-40 min. Then, 1 mmol of anhydrous copper acetate, 20 mg of urea, and 1 mmol of lithium nitrate were added, and the mixture was stirred for another 10 min. The mixture was then transferred to a microwave hydrothermal reactor and the temperature was raised to 100 °C within 2 min. The reactor was kept at this temperature for 5 min. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the solid product was washed several times with anhydrous ethanol and deionized water. The precipitate was dried at 80 °C to obtain the modified flower-shaped manganese dioxide.

[0043] The additive is neodymium oxide.

[0044] The carbon nanotubes are single-walled carbon nanotubes.

[0045] The positive electrode electrolyte is a 35% (w / w) potassium hydroxide aqueous solution.

[0046] A method for preparing the above-mentioned alkaline battery positive electrode active material includes the following steps:

[0047] (1) Preparation of modified manganese dioxide;

[0048] (2) Mix the modified manganese dioxide, additives, carbon nanotubes and polyvinyl alcohol evenly to obtain a mixed powder. Ball mill the mixed powder at a speed of 300-400 r / min for 4-6 hours and then add the positive electrode electrolyte. Mix evenly and vacuum to obtain the positive electrode material. Then, use a slurry mold to coat the material onto a titanium mesh that has been cleaned with alcohol. Dry the titanium mesh in an oven at 60°C for 12 hours and then take it out. Use a cutting machine to cut the titanium foil into positive electrode sheets for use.

[0049] Example 4

[0050] A positive electrode active material for alkaline batteries is made from the following raw materials in parts by weight: 110 parts modified manganese dioxide, 0.6 parts additives, 2 parts carbon nanotubes, 0.3 parts polyvinyl alcohol, and 5 parts positive electrode electrolyte.

[0051] The modified manganese dioxide was prepared by the following method: 100 ml of 0.5 mol / L manganese sulfate solution was prepared, 12.55 g of ammonium persulfate was added, and the mixture was magnetically stirred until homogeneous. Then, 50 ml of ethylene glycol and 5 mmol of sodium dodecylbenzenesulfonate were added, and the mixture was stirred at room temperature for 30-40 min. Then, 1 mmol of anhydrous copper acetate, 20 mg of urea, and 1 mmol of lithium nitrate were added, and the mixture was stirred for another 10 min. The mixture was then transferred to a microwave hydrothermal reactor and the temperature was raised to 100 °C within 2 min. The reactor was kept at this temperature for 5 min. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the solid product was washed several times with anhydrous ethanol and deionized water. The precipitate was dried at 80 °C to obtain the modified flower-shaped manganese dioxide.

[0052] The additive is one of indium oxide.

[0053] The carbon nanotubes are single-walled carbon nanotubes.

[0054] The positive electrode electrolyte is a 35% (w / w) potassium hydroxide aqueous solution.

[0055] A method for preparing the above-mentioned alkaline battery positive electrode active material includes the following steps:

[0056] (1) Preparation of modified manganese dioxide;

[0057] (2) Mix the modified manganese dioxide, additives, carbon nanotubes and polyvinyl alcohol evenly to obtain a mixed powder. Ball mill the mixed powder at a speed of 300-400 r / min for 4-6 hours and then add the positive electrode electrolyte. Mix evenly and vacuum to obtain the positive electrode material. Then, use a slurry mold to coat the material onto a titanium mesh that has been cleaned with alcohol. Dry the titanium mesh in an oven at 60°C for 12 hours and then take it out. Use a cutting machine to cut the titanium foil into positive electrode sheets for use.

[0058] Example 5

[0059] A positive electrode active material for alkaline batteries is made from the following raw materials in parts by weight: 120 parts modified manganese dioxide, 0.8 parts additives, 1 part carbon nanotubes, 0.2 parts polyvinyl alcohol, and 4 parts positive electrode electrolyte.

[0060] The modified manganese dioxide was prepared by the following method: 100 ml of 0.5 mol / L manganese sulfate solution was prepared, 12.55 g of ammonium persulfate was added, and the mixture was magnetically stirred until homogeneous. Then, 50 ml of ethylene glycol and 5 mmol of sodium dodecylbenzenesulfonate were added, and the mixture was stirred at room temperature for 30-40 min. Then, 1 mmol of anhydrous copper acetate, 20 mg of urea, and 1 mmol of lithium nitrate were added, and the mixture was stirred for another 10 min. The mixture was then transferred to a microwave hydrothermal reactor and the temperature was raised to 100 °C within 2 min. The reactor was kept at this temperature for 5 min. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the solid product was washed several times with anhydrous ethanol and deionized water. The precipitate was dried at 80 °C to obtain the modified flower-shaped manganese dioxide.

[0061] The additive is neodymium oxide.

[0062] The carbon nanotubes are single-walled carbon nanotubes.

[0063] The positive electrode electrolyte is a 35% (w / w) potassium hydroxide aqueous solution.

[0064] A method for preparing the above-mentioned alkaline battery positive electrode active material includes the following steps:

[0065] (1) Preparation of modified manganese dioxide;

[0066] (2) Mix the modified manganese dioxide, additives, carbon nanotubes and polyvinyl alcohol evenly to obtain a mixed powder. Ball mill the mixed powder at a speed of 300-400 r / min for 4-6 hours and then add the positive electrode electrolyte. Mix evenly and vacuum to obtain the positive electrode material. Then, use a slurry mold to coat the material onto a titanium mesh that has been cleaned with alcohol. Dry the titanium mesh in an oven at 60°C for 12 hours and then take it out. Use a cutting machine to cut the titanium foil into positive electrode sheets for use.

[0067] Comparative Example 1

[0068] A positive electrode active material for alkaline batteries is made from the following raw materials in parts by weight: 120 parts modified manganese dioxide, 0.8 parts additives, 1 part carbon nanotubes, 0.2 parts polyvinyl alcohol, and 4 parts positive electrode electrolyte.

[0069] The modified manganese dioxide was prepared by the following method: 100 ml of 0.5 mol / L manganese sulfate solution was prepared, 12.55 g of ammonium persulfate was added, and the mixture was magnetically stirred until homogeneous. Then, 50 ml of ethylene glycol and 5 mmol of sodium dodecylbenzenesulfonate were added, and the mixture was stirred at room temperature for 30-40 min. Then, 20 mg of urea and 1 mmol of lithium nitrate were added, and the mixture was stirred for another 10 min. The mixture was then transferred to a microwave hydrothermal reactor and the temperature was raised to 100 °C within 2 min. The reactor was kept at this temperature for 5 min. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the solid product was washed several times with anhydrous ethanol and deionized water. The precipitate was dried at 80 °C to obtain the modified flower-shaped manganese dioxide.

[0070] The additive is neodymium oxide.

[0071] The carbon nanotubes are single-walled carbon nanotubes.

[0072] The positive electrode electrolyte is a 35% (w / w) potassium hydroxide aqueous solution.

[0073] A method for preparing the above-mentioned alkaline battery positive electrode active material includes the following steps:

[0074] (1) Preparation of modified manganese dioxide;

[0075] (2) Mix the modified manganese dioxide, additives, carbon nanotubes and polyvinyl alcohol evenly to obtain a mixed powder. Ball mill the mixed powder at a speed of 300-400 r / min for 4-6 hours and then add the positive electrode electrolyte. Mix evenly and vacuum to obtain the positive electrode material. Then, use a slurry mold to coat the material onto a titanium mesh that has been cleaned with alcohol. Dry the titanium mesh in an oven at 60°C for 12 hours and then take it out. Use a cutting machine to cut the titanium foil into positive electrode sheets for use.

[0076] Except for the absence of anhydrous copper acetate in the preparation method of modified manganese dioxide, the raw materials and preparation methods in this comparative example are the same as in Example 5.

[0077] Comparative Example 2

[0078] Except for the absence of lithium nitrate in the preparation method of modified manganese dioxide, the raw materials and preparation methods in this comparative example are the same as in Example 5.

[0079] Comparative Example 3

[0080] Except for the absence of anhydrous copper acetate and lithium nitrate in the preparation method of the modified manganese dioxide, the other raw materials and preparation methods in this comparative example are the same as in Example 5.

[0081] Comparative Example 4

[0082] A positive electrode active material for alkaline batteries is made from the following raw materials in parts by weight: 120 parts manganese dioxide, 0.8 parts additives, 1 part carbon nanotubes, 0.2 parts polyvinyl alcohol, and 4 parts positive electrode electrolyte.

[0083] The manganese dioxide used in this comparative example was a commercially available raw material. All other raw materials were the same as in Example 5.

[0084] A method for preparing a positive electrode active material for alkaline batteries includes the following steps: manganese dioxide, additives, carbon nanotubes, and polyvinyl alcohol are mixed evenly to obtain a mixed powder. The mixed powder is ball-milled at a speed of 300-400 r / min for 4-6 hours, and then a positive electrode electrolyte is added. The mixture is mixed evenly and vacuumed to obtain the positive electrode material. The material is then coated onto a titanium mesh that has been cleaned with alcohol using a slurry mold. The titanium mesh is dried in an oven at 60°C for 12 hours and then removed. The titanium foil is then cut into positive electrode sheets using a cutting machine for use.

[0085] Performance testing

[0086] The microstructure of the modified manganese dioxide positive electrode active material obtained in Example 5 was analyzed using scanning electron microscopy, as follows: Figure 1 As shown. The modified manganese dioxide prepared in Example 5 has a flower-like layered three-dimensional structure, which is composed of many irregular thin sheets with a diameter of 2-3 μm. This structure has high porosity and short diffusion length, providing an efficient transport path for zinc ions, allowing zinc ions to diffuse and migrate more easily in the material, thereby improving the charge-discharge rate and cycle performance of the battery.

[0087] Using the positive electrode obtained in Example 5 of this invention as the positive electrode, a zinc sheet as the negative electrode, and a 35% potassium hydroxide aqueous solution as the electrolyte, a full cell was assembled and tested.

[0088] The positive electrode active materials for alkaline batteries prepared in Example 5 and Comparative Examples 1-4 were selected, and their AC impedance was tested using an electrochemical analyzer. The electrochemical impedance test parameters were as follows: test frequency range: 0.1 × 10⁻⁶. -6 ~1×10 6 Hz. EIS spectrum and corresponding fitting circuit as follows Figure 2 As shown in the fitted circuit diagram, Rs and Rct are the electrolyte resistance and charge transfer resistance, respectively; CPE1 is a constant phase angle element related to the interface resistance; and W0 is a Warburg resistor element. Rct reflects the ease or difficulty of charge transfer at the electrode / electrolyte interface. Figure 2It can be seen that the impedance Rct of the positive electrode material prepared in Example 5 of the present invention is significantly lower than that of Comparative Examples 1-4. This indicates that the introduction of copper-lithium bimetal and the synergistic effect of composite materials such as carbon nanotubes in the electrode material prepared by the present invention further enhance the conductivity of the material, and the material has good electrochemical performance.

[0089] Cyclic voltammetry (CV) curves were tested using a CHI 660E electrochemical workstation at a scan rate of 1 mV·s. -1 The voltage range is 0.8–2.0V. The results are as follows: Figure 3 As shown, from Figure 3 It can be seen that the positive electrode active material prepared in Example 5 of this invention has the highest peak value in the cyclic voltammetry test, indicating that the battery assembled using the positive electrode sheet prepared by this invention has a higher capacity. This is because the manganese dioxide material doped with copper-lithium bimetallic ions has higher activity and conductivity, and the stability of the obtained three-dimensional flower-shaped layered MnO2 structure is also further improved.

[0090] The zinc-manganese battery was subjected to charge / discharge and cycle stability tests using a CT2001 battery testing system at 1C. The results are as follows: Figure 4 As shown, the positive electrode active material prepared in Example 5 of the present invention has good cycle performance. Under 1C conditions, the initial discharge specific capacity can reach 363mAh / g, and the capacity retention rate is more than 80% after 500 cycles. In contrast, the comparative examples 1-4 show more severe degradation. This indicates that the positive electrode material prepared in the present invention has good cycle performance and extends the battery life.

[0091] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A positive electrode active material for alkaline batteries, characterized in that, It is made from the following raw materials in parts by weight: 100-120 parts modified manganese dioxide, 0.5-0.8 parts additives, 1-3 parts carbon nanotubes, 0.2-0.4 parts polyvinyl alcohol, and 3-5 parts positive electrode electrolyte; The modified manganese dioxide was prepared by the following method: 100 ml of 0.5 mol / L manganese sulfate solution was prepared, 12.55 g of ammonium persulfate was added, and the mixture was magnetically stirred until homogeneous. Then, 50 ml of ethylene glycol and 5 mmol of sodium dodecylbenzenesulfonate were added, and the mixture was stirred at room temperature for 30-40 min. Then, 1 mmol of anhydrous copper acetate, 20 mg of urea, and 1 mmol of lithium nitrate were added, and the mixture was stirred for another 10 min. The mixture was then transferred to a microwave hydrothermal reactor, and the heating rate was set to raise the temperature to 100 °C within 2 min. The temperature was maintained for 5 min, and after the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the solid product was washed several times with anhydrous ethanol and deionized water. The precipitate was dried at 80 °C to obtain the modified flower-shaped manganese dioxide.

2. The positive electrode active material for alkaline batteries according to claim 1, characterized in that, The additive is one of cerium oxide, indium oxide, and neodymium oxide.

3. The positive electrode active material for alkaline batteries according to claim 1, characterized in that, The carbon nanotubes are single-walled carbon nanotubes and / or multi-walled carbon nanotubes.

4. The positive electrode active material for alkaline batteries according to claim 1, characterized in that, The positive electrode electrolyte is a 35% (w / w) potassium hydroxide aqueous solution.

5. A method for preparing a positive electrode active material for an alkaline battery according to any one of claims 1-4, characterized in that, It includes the following steps: (1) Preparation of modified manganese dioxide; (2) Mix the modified manganese dioxide, additives, carbon nanotubes and polyvinyl alcohol evenly to obtain a mixed powder. Ball mill the mixed powder at a speed of 300-400 r / min for 4-6 hours and then add the positive electrode electrolyte. Mix evenly and vacuum to obtain the positive electrode material. Then, use a slurry mold to coat the material onto the titanium mesh that has been cleaned with alcohol. Dry the titanium mesh in an oven at 60°C for 12 hours and then take it out. Use a cutting machine to cut the titanium foil into positive electrode sheets for use.

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