Alkaline battery negative electrode material and preparation method thereof

Abstract

The invention discloses an alkaline battery negative electrode material and a preparation method thereof, and the preparation method comprises the following steps: S1, zinc powder pretreatment: after zinc powder is cleaned by supercritical carbon dioxide, boron-containing gas is introduced for gas-phase coating passivation; s2, preparation of a composite surfactant mother solution: preparing the composite surfactant mother solution composed of polyether modified siloxane and the like; s3, performing vacuum wet mixing on zinc paste: performing dry mixing and pre-wetting on zinc powder and a surfactant, and performing wet mixing on the zinc powder and a KOH electrolyte in a vacuum kettle to prepare the paste; s4, paste injection and compaction: injecting the zinc paste into a negative electrode cup of the zinc-manganese alkaline battery, and performing compaction molding; impurities on the surface of the zinc powder are removed through supercritical carbon dioxide treatment, and a nano passive film is formed in the atmosphere of triethyl borane or methyl borate, so that corrosion and hydrogen evolution reaction are effectively inhibited; the composite surfactant can improve the wetting and dispersing performance of the zinc powder, and is matched with vacuum stirring and nitrogen defoaming processes to reduce bubble residues and improve the compactness of the zinc paste, so that the capacity stability of the alkaline battery is improved.

Description

Technical Field

[0001] This invention relates to the field of alkaline battery anode materials, and more particularly to an alkaline battery anode material and its preparation method. Background Technology

[0002] Alkaline batteries are electrochemical energy storage devices that use alkaline electrolytes such as potassium hydroxide or sodium hydroxide as the conductive medium, manganese dioxide as the positive electrode active material, and metallic zinc as the negative electrode active material. They are widely used in electronics, industrial instruments, portable devices, and other fields. The negative electrode material of alkaline batteries is generally prepared by mixing granular zinc powder with a certain proportion of alkaline electrolyte and functional additives to form zinc paste. The density, dispersion uniformity, and electrochemical stability of the zinc paste affect the discharge performance and service life of alkaline batteries.

[0003] In existing technologies, the preparation of negative electrode zinc paste generally involves a wet stirring process, in which zinc powder, electrolyte, and additives are mixed to form a slurry and then injected into the negative electrode shell. However, air bubbles are generated during the stirring process. These residual air bubbles cannot be completely removed during paste injection, which can easily lead to uneven paste density, resulting in partial interruption of the conductive path or even the formation of void structures, affecting the performance of alkaline batteries. In addition, the presence of air bubbles can also easily lead to risks such as micro-leakage, bulging, or performance degradation inside the alkaline battery, thereby affecting the service life of the alkaline battery.

[0004] Therefore, existing technologies have shortcomings and need to be improved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an alkaline battery negative electrode material and its preparation method for improving the performance and extending the service life of alkaline batteries.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A method for preparing an alkaline battery negative electrode material includes the following steps:

[0008] S1. Zinc powder pretreatment: Select spherical zinc powder with a particle size of 30-60μm, place the zinc powder in a supercritical carbon dioxide reactor, and treat it under a pressure of 6.5-7.5MPa for 30-50min. Then, treat the zinc powder with 0.01-0.03wt% boron element in a gas phase plasma coating process to passivate and modify the zinc powder.

[0009] S2. Preparation of composite surfactant mother liquor: Polyether modified silicone oil defoamer, fluorocarbon surfactant and cationic wetting agent are mixed in a mass ratio of 4:2:1 to obtain an auxiliary agent mixture. The auxiliary agent mixture is dissolved in deionized water, wherein the mass ratio of the auxiliary agent mixture to deionized water is 100:1.

[0010] Then, the mixture is stirred with a magnetic stirrer for 20-30 minutes at a temperature of 23-28°C to fully disperse the additive mixture into a stable homogeneous liquid. Then, 1-2% ethanol is added as a co-solvent and stirred for 10-20 minutes to obtain the composite surfactant mother liquor.

[0011] S3. Vacuum wet-mixed zinc paste: The pretreated zinc powder and the composite surfactant mother liquor are dry premixed at a mass ratio of 100:1-2. The mixture is placed in a rotary mixer at room temperature and stirred at a speed of 80-120 rpm for 5-10 minutes to obtain pre-wetted zinc powder.

[0012] The pre-wetted zinc powder and KOH electrolyte were then placed in a vacuum stirring vessel and stirred to obtain zinc paste, wherein the volume ratio between the pre-wetted zinc powder and KOH electrolyte was 5:1.

[0013] S4. Load the zinc paste into the paste injection device and inject the zinc paste into the zinc-manganese alkaline battery negative electrode cup at a paste injection speed of 0.8-1.2 mL / s. After compaction, the alkaline battery negative electrode is obtained.

[0014] Using the above technical solution, in step S3, the stirring process of the vacuum stirred tank is as follows:

[0015] First, set the initial speed of the agitator to 300 rpm, start the jacket cooling water system, and maintain the temperature of the mixing vessel at 23-25℃;

[0016] Add KOH electrolyte, accounting for 8% of the total volume of the target zinc paste, to the vacuum stirred tank and stir for 5-7 minutes to form the initial liquid base layer; then add zinc powder and composite surfactant mother liquor evenly to the vacuum stirred tank through a screw propeller in three batches, with an interval of 2-3 minutes between each addition, and maintain stirring during the addition process;

[0017] After the addition is completed, switch the vacuum stirring tank system to the first-level vacuum state. At this time, the pressure inside the vacuum stirring tank drops to -0.08MPa. Maintain this pressure and continue stirring for 5-10 minutes.

[0018] Then, add KOH electrolyte accounting for 6% of the total volume of the target zinc paste to the vacuum stirring vessel, increase the stirring speed to 500-600 rpm, and simultaneously start the vacuum-atmospheric pressure cycle switching mode, switching between vacuum and atmospheric pressure every 3-5 minutes. After four cycles, stop stirring, turn off the vacuum system, and let it stand at atmospheric pressure for 6-8 minutes to allow the bubbles to rise and fall naturally.

[0019] Add 6% KOH electrolyte (by total volume of the target zinc paste) and 0.2-0.6 wt% hydroxypropyl methylcellulose (by total mass of the zinc paste). Stir the mixture in a vacuum mixer at 600-700 rpm for 5 minutes to obtain the zinc paste.

[0020] Using the above technical solution, the specific process flow for zinc powder passivation modification in step S1 is as follows:

[0021] Spherical zinc powder is evenly spread in a material frame with sieve holes, with a thickness not exceeding 3cm. Then, the material frame is pushed into the inner cavity of the supercritical carbon dioxide reactor. After closing the reactor door, the pressure is gradually increased to 6.5-7.5MPa, and the temperature is controlled at 35℃±1℃. The circulation pump is started to circulate liquid carbon dioxide in the reactor at a flow rate of 20-30L / min for 30-50min. Then, the pressure is reduced to atmospheric pressure.

[0022] Remove the zinc powder and air dry it in a drying room for 15-20 minutes. Then, place the air-dried zinc powder in a gas phase heat treatment chamber with an inert atmosphere protection function, and introduce a boron-containing gas containing 0.01-0.03 wt%, and introduce nitrogen or argon as a protective gas. The gas flow rate is controlled at 200-400 mL / min, and the temperature is controlled at 150-250℃. After reacting for 5-10 minutes, a nanoscale passivation film is formed on the surface of the zinc powder by boron, thereby completing the passivation modification treatment of the zinc powder surface.

[0023] Using the above technical solution, in step S2, the polyether-modified silicone oil defoamer is a polyether-modified siloxane, the fluorocarbon surfactant is a fluorocarbon carboxylate, and the cationic wetting agent is a quaternary ammonium salt surfactant.

[0024] Using the above technical solution, in step S3, after the zinc paste is prepared, the vacuum stirring vessel is switched to a secondary vacuum state. At this time, the pressure inside the vacuum stirring vessel drops to -0.095MPa, and then it is stirred at low speed for 1-2 minutes and then kept still.

[0025] Using the above technical solution, the zinc paste is subjected to a static degassing treatment before being loaded into the paste injection device. The specific process flow is as follows:

[0026] Zinc paste was placed in a settling degassing tank, and high-purity nitrogen gas was injected from the bottom at a flow rate of 0.1-0.3 L / min for 30-40 min. Then, a laser particle analyzer was used to sample and detect the residual amount of air bubbles in the zinc paste, ensuring that the bubble size D90 ≤ 20 μm and the density ≤ 5 bubbles / mm. 3 .

[0027] Using the above technical solution, the thickness of the nanoscale passivation film is 10-20 nm.

[0028] Using the above technical solution, the boron-containing gas is formed by heating and evaporating triethylborane or methyl borate.

[0029] Using the above technical solution, in step S4, the compaction density of zinc paste in the negative electrode cup of the zinc-manganese alkaline battery is 6.2-6.8 g / cm³. 3 .

[0030] This technical solution also provides an alkaline battery negative electrode material, which is prepared by any of the above-mentioned methods for preparing alkaline battery negative electrode materials.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] This invention employs supercritical carbon dioxide to permeate the surface of zinc powder, removing the oxide film and adsorbed impurities. Combined with a boron-containing atmosphere formed by triethylborane or methyl borate for low-temperature vapor-phase coating, a dense and stable nanoscale passivation film is formed on the zinc powder surface. This ensures unobstructed conductive paths while effectively inhibiting zinc powder corrosion and hydrogen evolution reactions, thereby improving the storage safety of alkaline batteries. Secondly, the composite surfactant mother liquor, through the synergistic effect of polyether-modified silicone oil defoamers, fluorocarbon surfactants, and cationic wetting agents, achieves efficient wetting and stable dispersion of zinc powder, improving the uniformity of zinc paste formation. Subsequently, combined with segmented speed-controlled stirring in a vacuum mixing vessel, batch feeding, and multi-round vacuum-atmospheric pressure switching degassing process, residual bubbles are effectively reduced, enhancing the density of the zinc paste. Finally, the particle size and density of bubbles are controlled through paste injection compaction and nitrogen degassing processes to form a compact zinc paste, improving the conductivity of alkaline batteries and the capacity stability during long-term storage and use. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., described below refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the technical features involved in the various embodiments of the invention can be combined with each other as long as they do not conflict with each other.

[0034] This invention provides a method for preparing an alkaline battery negative electrode material, comprising the following steps:

[0035] S1. Zinc Powder Pretreatment: Spherical zinc powder with a particle size of 30-60μm is selected. The zinc powder is placed in a supercritical carbon dioxide reactor and treated under a pressure of 6.5-7.5MPa for 30-50 minutes. Subsequently, the zinc powder is subjected to vapor-phase plasma coating treatment with 0.01-0.03wt% boron element to passivate and modify the zinc powder. In the preparation of alkaline battery negative electrode materials, if there are oxidized impurities on the surface of the zinc powder, it will adsorb moisture, which will easily aggravate the corrosion of zinc in the electrolyte and the hydrogen evolution reaction, thereby affecting the storage performance of the alkaline battery and easily leading to battery failure. Problems such as expansion and even leakage can be addressed by pretreating zinc powder in a supercritical carbon dioxide environment. This utilizes the strong permeability of supercritical carbon dioxide to effectively remove the oxide film, residual organic matter, and weakly adsorbed moisture from the zinc powder surface. Subsequent vapor-phase coating of the zinc powder with boron-containing gas allows trace amounts of boron to form a uniform and dense amorphous passivation film on the zinc powder surface. This passivation film effectively blocks the direct contact between zinc and OH- in the alkaline electrolyte, inhibiting its self-corrosion rate, while maintaining good electron and ion conduction pathways, thus preventing the coating layer from affecting the electrochemical reaction.

[0036] S2. Preparation of composite surfactant mother liquor: Polyether-modified silicone oil defoamer, fluorocarbon surfactant, and cationic wetting agent are mixed at a mass ratio of 4:2:1 to obtain an additive mixture. The additive mixture is dissolved in deionized water, wherein the mass ratio of the additive mixture to deionized water is 100:1. Then, the mixture is stirred with a magnetic stirrer for 20-30 minutes at a temperature of 23-28℃ to fully disperse the additive mixture into a stable homogeneous liquid. 1-2% (v / v) of ethanol is added as a co-solvent, and the mixture is stirred for 10-20 minutes to obtain the composite surfactant mother liquor. Polyether-modified silicone oil... Defoamers can spread and break bubbles at the gas-liquid interface, inhibiting foam stability. Fluorocarbon surfactants can enhance the penetration ability of liquids on the surface of solid particles through extremely low surface tension, while cationic wetting agents can enhance the directional adsorption performance of additives on the surface of zinc powder through electrostatic adsorption, thereby improving the dispersion efficiency of the powder. The additive mixture is dissolved in deionized water, and each component is uniformly dissolved by magnetic stirring to prevent the additive components from stratifying or agglomerating. Using 1-2% ethanol as a co-solvent can reduce the surface tension of the aqueous phase and increase the volatility of the composite surfactant mother liquor, which facilitates the subsequent drying and compaction processes of zinc paste.

[0037] S3. Vacuum wet-mixed zinc paste: Pre-treated zinc powder and composite surfactant mother liquor are dry-mixed at a mass ratio of 100:1-2. The mixture is then placed in a rotary mixer at room temperature and stirred at 80-120 rpm for 5-10 minutes to obtain pre-wetted zinc powder. Subsequently, the pre-wetted zinc powder and KOH electrolyte are placed in a vacuum mixing vessel and stirred to obtain zinc paste. The volume ratio between the pre-wetted zinc powder and KOH electrolyte is 5:1. Surface passivated zinc powder and composite surfactant mother liquor are dry-mixed at a certain ratio. By using a low-speed rotary mixer, the composite surfactant mother liquor is uniformly coated on the surface of the zinc powder, thereby forming a preliminary wetting and adsorption layer and improving the wetting rate of the zinc powder in the subsequent liquid phase.

[0038] S4. Load the zinc paste into the paste injection device and inject the zinc paste into the negative electrode cup of the zinc-manganese alkaline battery at a paste injection speed of 0.8-1.2 mL / s. After compaction, the negative electrode of the alkaline battery is obtained. The compaction operation of zinc paste can compress the micropores inside the zinc paste by controlling the compaction force, thereby reducing the gap between particles, releasing air bubbles, enhancing the contact interface between the active material and the conductor, and improving the electronic conduction efficiency and ion diffusion rate of the alkaline battery.

[0039] Furthermore, in step S3, the stirring process of the vacuum stirring vessel is as follows: First, the initial speed of the stirring paddle is set to 300 rpm, the jacket cooling water system is started, and the temperature of the stirring vessel is maintained at 23-25℃. KOH electrolyte, accounting for 8% of the total volume of the target zinc paste, is added to the vacuum stirring vessel, and stirring is performed for 5-7 minutes to form the initial liquid base layer. Subsequently, zinc powder and composite surfactant mother liquor are evenly added to the vacuum stirring vessel through a screw propeller in three batches, with an interval of 2-3 minutes between each addition. Stirring is maintained during the addition process. After the addition is completed, the vacuum stirring vessel system is switched to a first-level vacuum state, at which point the pressure inside the vacuum stirring vessel drops to -0.08 MPa. a. Maintain the pressure and continue stirring for 5-10 minutes. Then, add 6% KOH electrolyte (6% of the total volume of the target zinc paste) to the vacuum mixing vessel. Increase the stirring speed to 500-600 rpm and simultaneously start the vacuum-atmospheric pressure cycle switching mode, switching between vacuum and atmospheric pressure every 3-5 minutes. After four cycles, stop stirring, turn off the vacuum system, and let it stand at atmospheric pressure for 6-8 minutes to allow the bubbles to rise and escape naturally. Add 6% KOH electrolyte (6% of the total volume of the target zinc paste) and 0.2-0.6 wt% hydroxypropyl methylcellulose (0.2-0.6 wt% of the total mass of the zinc paste). Stir the vacuum mixing vessel again at 600-700 rpm for 5 minutes to obtain the zinc paste. In the initial stage of the vacuum stirred tank, the stirring speed is set to 300 rpm, and the tank temperature is maintained at 23-25℃ to ensure the liquid spreads smoothly within the tank, avoiding splashing of additives due to initial violent disturbance. Then, KOH electrolyte, accounting for 8% of the target zinc paste volume, is introduced to form an initial liquid base layer, ensuring uniform spreading of the liquid phase at the bottom of the tank and reducing localized agglomeration during subsequent zinc powder addition. Zinc powder and surfactant mother liquor are added to the stirred tank in three batches using a screw propeller, with each batch added 2-3 minutes apart. While maintaining stirring, a preliminary uniform paste precursor system is formed. The system is then depressurized to a primary vacuum state of -0.08 MPa, which induces dissolution in the solution through the pressure difference. Gases and bubbles are released outwards. Finally, 6% KOH electrolyte (by volume of zinc paste) is added, and the rotation speed is increased to 500-600 rpm to enhance the shear disturbance efficiency of the solid-liquid mixture. By alternating between vacuum and atmospheric pressure, and repeatedly adjusting the pressure in 3-5 minute cycles, residual bubbles are driven to migrate from the interior to the interface and float to the surface for release. The dynamic changes in the internal pressure of the bubbles cause them to burst. After the vacuum system is turned off, the mixture is allowed to stand for 6-8 minutes to further remove microbubbles through buoyancy, improving the density of the zinc paste. Finally, 6% KOH electrolyte and hydroxypropyl methylcellulose (by volume of the target zinc paste) are added to adjust the bonding properties. The mixture is then dispersed by high-speed stirring at 600-700 rpm for 5 minutes to obtain the zinc paste.

[0040] Furthermore, in step S1, the specific process flow for zinc powder passivation modification is as follows: Spherical zinc powder is evenly spread in a material frame with sieve holes, with a thickness not exceeding 3 cm. The material frame is then pushed into the inner cavity of a supercritical carbon dioxide reactor. After closing the reactor door, the pressure is gradually increased to 6.5-7.5 MPa, and the temperature is controlled at 35℃±1℃. The circulation pump is started, and liquid carbon dioxide is circulated in the reactor at a flow rate of 20-30 L / min for 30-50 min. The pressure is then reduced to atmospheric pressure. Remove the zinc powder and air dry it in a drying room for 15-20 minutes. Then, place the air-dried zinc powder in a gas phase heat treatment chamber with an inert atmosphere protection function, and introduce a boron-containing gas containing 0.01-0.03 wt%, and introduce nitrogen or argon as a protective gas. The gas flow rate is controlled at 200-400 mL / min, and the temperature is controlled at 150-250℃. After reacting for 5-10 minutes, a nanoscale passivation film is formed on the surface of the zinc powder by boron, thereby completing the passivation modification treatment of the zinc powder surface. Spherical zinc powder is evenly spread in a sieve-filled frame, with a thickness not exceeding 3 cm. This allows carbon dioxide to fully penetrate the zinc powder layer during supercritical treatment, preventing localized dead zones. The frame is then pushed into the reactor and the pressure is slowly increased to 6.5-7.5 MPa, while the temperature is maintained at 35℃±1℃. This allows carbon dioxide to exhibit liquid-like solubility and gas-like permeability under critical conditions, circulating within the reactor at a flow rate of 20-30 L / min. This effectively removes residual trace amounts of moisture and oxide impurities from the zinc powder surface, providing a clean active surface. After the zinc powder is air-dried, it is then introduced into a reactor with an inert gas... The atmosphere-protected gas-phase heat treatment chamber introduces boron-containing gas (0.01-0.03 wt%), supplemented by nitrogen or argon as a protective gas. The gas flow rate is controlled at 200-400 mL / min, and the chamber temperature is maintained between 150-250℃. This causes the boron-containing molecules to dissociate and activate in the heating environment, forming a uniform nanoscale passivation film on the zinc powder surface. The thickness of the nanoscale passivation film is 10-20 nm. This nanoscale passivation film not only inhibits the corrosion of the zinc surface by hydroxide ions under alkaline conditions, reducing the hydrogen evolution rate and the risk of electrochemical corrosion, but also maintains good surface electronic conductivity.

[0041] Furthermore, in step S2, the polyether-modified silicone oil defoamer is a polyether-modified siloxane, the fluorocarbon surfactant is a fluorocarbonate, and the cationic wetting agent is a quaternary ammonium salt surfactant. The main chain of the polyether-modified siloxane is a hydrophobic polysiloxane skeleton, with hydrophilic polyether segments introduced into the side chains, possessing both excellent surface spreadability and liquid-phase compatibility. It can rapidly migrate to the gas-liquid interface during stirring, disrupting the stability of the bubble film and reducing foam persistence, thus achieving rapid foam suppression and defoaming. The CF bond structure of the fluorocarbonate is highly hydrophobic, which can effectively reduce the total interfacial energy of the paste system, thereby enhancing the dispersibility of the additive on the zinc powder surface and in the liquid, and improving wetting efficiency. The quaternary ammonium salt surfactant can quickly anchor to the zinc powder surface through electrostatic adsorption, thereby promoting the wetting affinity between the zinc powder surface and the liquid phase interface.

[0042] Furthermore, in step S3, after the zinc paste is prepared, the vacuum stirring vessel is switched to a secondary vacuum state. At this time, the pressure inside the vacuum stirring vessel drops to -0.095MPa. After stirring at low speed for 1-2 minutes, it is kept still. With this setting, the migration rate of bubbles can be increased through the effect of air-pressure differential to defoam.

[0043] Furthermore, before loading the zinc paste into the injection device, the zinc paste undergoes a static degassing treatment. The specific process is as follows: the zinc paste is placed in a static degassing tank, and high-purity nitrogen gas is injected from the bottom at a flow rate of 0.1-0.3 L / min for 30-40 minutes. Then, a laser particle analyzer is used to sample and detect the residual amount of air bubbles in the zinc paste, ensuring that the bubble particle size D90 ≤ 20 μm and the density ≤ 5 bubbles / mm. 3 The zinc paste was transferred to a settling degassing tank, and high-purity nitrogen gas was introduced from the bottom at a low flow rate. This gently disturbed the paste through the slowly rising airflow, causing small air bubbles to detach, aggregate, and slowly rise. It also prevented air from re-introducing into the paste. No stirring was required throughout the process; degassing was achieved slowly through the airflow. Finally, a laser particle analyzer was used to sample and test the bubbles, ensuring that the bubble diameter (D90) was controlled below 20 μm and the density was no higher than 5 bubbles / mm. 3 This avoids problems such as battery swelling or performance fluctuations caused by air bubbles.

[0044] Furthermore, the boron-containing gas is formed by heating and evaporating triethylborane or methyl borate. Triethylborane has a low boiling point and moderate decomposition temperature, and can release boron-containing active groups when heated to above room temperature; while methyl borate can continuously release gaseous boron sources that can participate in the reaction when heated in the medium temperature range, and avoids oxidation side reactions under the protection of inert atmospheres such as nitrogen or argon. By controlling the temperature of the evaporation of triethylborane or methyl borate, a stable and controllable boron-containing atmosphere environment can be constructed without introducing highly corrosive components, thereby forming a dense and uniform passivation film on the surface of zinc powder particles.

[0045] Furthermore, in step S4, the compaction density of the zinc paste in the negative electrode cup of the zinc-manganese alkaline battery is 6.2-6.8 g / cm3. This setting ensures sufficient zinc active material content per unit volume, thereby improving the discharge capacity and energy density of the alkaline battery. At the same time, it also ensures sufficient contact between particles, reduces internal resistance, and enhances electron conductivity. It should be noted that if the density is too low, voids may easily form inside the zinc paste, leading to interruption of the conductive path and battery capacity decay. Conversely, if the compaction is excessive, excessive mechanical stress between zinc powder particles may occur, affecting the stability of the electrode structure and causing volume expansion during long-term use, thus affecting the service life of the alkaline battery.

[0046] Example 1

[0047] Example 1 of this invention provides a method for preparing an alkaline battery negative electrode material, comprising the following steps:

[0048] S1. Zinc powder pretreatment: Spherical zinc powder with a particle size of 30μm was selected. The zinc powder was placed in a supercritical carbon dioxide reactor and treated for 30 minutes under a pressure of 7.5MPa. Then, the zinc powder was subjected to gas phase plasma coating treatment with 0.03wt% boron element to passivate and modify the zinc powder.

[0049] The specific process flow for zinc powder passivation modification is as follows: Spherical zinc powder is evenly spread in a material frame with sieve holes, with a thickness not exceeding 3 cm. The material frame is then pushed into the inner cavity of a supercritical carbon dioxide reactor. After closing the reactor door, the pressure is gradually increased to 7.5 MPa, and the temperature is controlled at 35℃±1℃. A circulation pump is started, and liquid carbon dioxide is circulated in the reactor at a flow rate of 30 L / min for 30 min. The pressure is then reduced to atmospheric pressure, and the zinc powder is removed and placed in a drying chamber for 20 min. The dried zinc powder is then placed in a gas-phase heat treatment chamber with an inert atmosphere protection function. A boron-containing gas containing 0.03 wt% (formed by heating and evaporating triethylborane) is introduced, along with nitrogen as a protective gas. The gas flow rate is controlled at 200 mL / min, and the temperature is controlled at 250℃. After reacting for 5 min, a nanoscale passivation film is formed on the surface of the zinc powder, thus completing the passivation modification treatment of the zinc powder surface. The thickness of the nanoscale passivation film is 10 nm.

[0050] S2. Preparation of composite surfactant mother liquor: Polyether modified silicone oil defoamer, fluorocarbon surfactant and cationic wetting agent are mixed in a mass ratio of 4:2:1 to obtain an additive mixture. The additive mixture is dissolved in deionized water, wherein the mass ratio of additive mixture to deionized water is 100:1. Then, the mixture is stirred for 30 minutes with a magnetic stirrer at a stirring temperature of 28°C to fully disperse the additive mixture into a stable homogeneous liquid. Then, 2% ethanol is added as a co-solvent and stirred for 20 minutes to obtain the composite surfactant mother liquor.

[0051] Among them, the polyether-modified silicone oil defoamer is a polyether-modified siloxane, the fluorocarbon surfactant is a fluorocarbon carboxylate, and the cationic wetting agent is a quaternary ammonium salt surfactant.

[0052] S3, Vacuum wet-mixed zinc paste: The pretreated zinc powder and the composite surfactant mother liquor are dry premixed at a mass ratio of 100:1. The mixture is placed in a rotary mixer at room temperature and stirred at 120 rpm for 10 minutes to obtain pre-wetted zinc powder. Then, the pre-wetted zinc powder and KOH electrolyte are placed in a vacuum mixing tank and stirred to obtain zinc paste. The volume ratio between the pre-wetted zinc powder and KOH electrolyte is 5:1.

[0053] The stirring process in the vacuum stirred tank is as follows: First, the initial speed of the stirring paddle is set to 300 rpm, the jacket cooling water system is started, and the temperature of the stirred tank is maintained at 25℃. KOH electrolyte, accounting for 8% of the total volume of the target zinc paste, is added to the vacuum stirred tank, and stirred for 7 minutes to form the initial liquid base layer. Then, zinc powder and composite surfactant mother liquor are evenly added to the vacuum stirred tank through a screw propeller in three batches, each 3 minutes apart, with stirring maintained during the addition process. After the addition is completed, the vacuum stirred tank system is switched to a first-level vacuum state, at which point the pressure inside the vacuum stirred tank drops to -0.08 MPa. This pressure is maintained, and stirring continues for 10 minutes. Then, KOH electrolyte, accounting for 8% of the total volume of the target zinc paste, is added to the vacuum stirred tank. Add 6% KOH electrolyte to the total volume of the target zinc paste, increase the stirring speed to 600 rpm, and simultaneously start the vacuum-atmospheric pressure cycle switching mode, switching between vacuum and atmospheric pressure every 3 minutes. After four cycles, stop stirring, turn off the vacuum system, and let it stand at atmospheric pressure for 8 minutes to allow the bubbles to rise and fall naturally. Add 6% KOH electrolyte and 0.6 wt% hydroxypropyl methylcellulose to the total volume of the target zinc paste. Stir the mixture in the vacuum mixer at 700 rpm for 5 minutes to obtain the zinc paste. After obtaining the zinc paste, switch the vacuum mixer to a secondary vacuum state, at which point the pressure inside the vacuum mixer drops to -0.095 MPa. Stir at low speed for 2 minutes and then let it stand.

[0054] S4. The zinc paste is loaded into the filling device and injected into the zinc-manganese alkaline battery negative electrode cup at a filling rate of 1.2 mL / s. After compaction, the alkaline battery negative electrode is obtained. The compacted density of the zinc paste in the zinc-manganese alkaline battery negative electrode cup is 6.8 g / cm³. 3 ;

[0055] Before loading the zinc paste into the injection device, the zinc paste undergoes a static degassing treatment. The specific process is as follows: the zinc paste is placed in a static degassing tank, and high-purity nitrogen gas is injected from the bottom at a flow rate of 0.3 L / min for 40 minutes. Then, a laser particle analyzer is used to sample and detect the residual amount of air bubbles in the zinc paste, ensuring that the bubble particle size D90 ≤ 20 μm and the density ≤ 5 bubbles / mm. 3 .

[0056] Example 2

[0057] Example 2 of this invention provides a method for preparing an alkaline battery negative electrode material, comprising the following steps:

[0058] S1. Zinc powder pretreatment: Spherical zinc powder with a particle size of 60μm was selected. The zinc powder was placed in a supercritical carbon dioxide reactor and treated under a pressure of 6.5MPa for 50min. Then, the zinc powder was subjected to gas phase plasma coating treatment with 0.01wt% boron element to passivate and modify the zinc powder.

[0059] The specific process flow for zinc powder passivation modification is as follows: Spherical zinc powder is evenly spread in a material frame with sieve holes, with a thickness not exceeding 3 cm. The material frame is then pushed into the inner cavity of a supercritical carbon dioxide reactor. After closing the reactor door, the pressure is gradually increased to 6.5 MPa, and the temperature is controlled at 35℃±1℃. A circulation pump is started, and liquid carbon dioxide is circulated in the reactor at a flow rate of 20 L / min for 50 min. The pressure is then reduced to atmospheric pressure, and the zinc powder is removed and placed in a drying chamber for 20 min. The dried zinc powder is then placed in a gas-phase heat treatment chamber with an inert atmosphere protection function. A boron-containing gas containing 0.01 wt% (formed by evaporating methyl borate upon heating) is introduced, along with argon gas as a protective gas. The gas flow rate is controlled at 400 mL / min, and the temperature is controlled at 150℃. After reacting for 5 min, a nanoscale passivation film is formed on the surface of the zinc powder, thus completing the passivation modification treatment of the zinc powder surface. The thickness of the nanoscale passivation film is 20 nm.

[0060] S2. Preparation of composite surfactant mother liquor: Polyether modified silicone oil defoamer, fluorocarbon surfactant and cationic wetting agent are mixed in a mass ratio of 4:2:1 to obtain an additive mixture. The additive mixture is dissolved in deionized water, wherein the mass ratio of additive mixture to deionized water is 100:1. Then, the mixture is stirred for 30 minutes with a magnetic stirrer at a stirring temperature of 23°C to fully disperse the additive mixture into a stable homogeneous liquid. Then, 1% ethanol is added as a co-solvent and stirred for 10 minutes to obtain the composite surfactant mother liquor.

[0061] Among them, the polyether-modified silicone oil defoamer is a polyether-modified siloxane, the fluorocarbon surfactant is a fluorocarbon carboxylate, and the cationic wetting agent is a quaternary ammonium salt surfactant.

[0062] S3, Vacuum wet-mixed zinc paste: The pretreated zinc powder and the composite surfactant mother liquor are dry premixed at a mass ratio of 100:2. The mixture is placed in a rotary mixer at room temperature and stirred at 80 rpm for 10 minutes to obtain pre-wetted zinc powder. Then, the pre-wetted zinc powder and KOH electrolyte are placed in a vacuum mixing tank and stirred to obtain zinc paste. The volume ratio between the pre-wetted zinc powder and KOH electrolyte is 5:1.

[0063] The stirring process in the vacuum stirred tank is as follows: First, the initial speed of the stirring paddle is set to 300 rpm, the jacket cooling water system is started, and the temperature of the stirred tank is maintained at 23℃. KOH electrolyte, accounting for 8% of the total volume of the target zinc paste, is added to the vacuum stirred tank, and stirring is carried out for 5 minutes to form the initial liquid base layer. Then, zinc powder and composite surfactant mother liquor are evenly added to the vacuum stirred tank through a screw propeller in three batches, each 2 minutes apart, with stirring maintained during the addition process. After the addition is completed, the vacuum stirred tank system is switched to a first-level vacuum state, at which point the pressure inside the vacuum stirred tank drops to -0.08M. Pa, maintain this pressure and continue stirring for 5 minutes; then add KOH electrolyte accounting for 6% of the total volume of the target zinc paste to the vacuum stirring vessel, increase the stirring speed to 500 rpm, and simultaneously start the vacuum-atmospheric pressure cycle switching mode, switching between vacuum and atmospheric pressure every 5 minutes, and after four cycles, stop stirring, turn off the vacuum system, and let it stand at atmospheric pressure for 6 minutes to allow the bubbles to rise and fall naturally; add KOH electrolyte accounting for 6% of the total volume of the target zinc paste and hydroxypropyl methylcellulose accounting for 0.2 wt% of the total mass of the zinc paste, and stir the vacuum stirring vessel again at 600 rpm for 5 minutes to obtain the zinc paste;

[0064] After the zinc paste is prepared, the vacuum mixing vessel is switched to a secondary vacuum state. At this time, the pressure inside the vacuum mixing vessel drops to -0.095MPa. After stirring at low speed for 2 minutes, it is kept still.

[0065] S4. The zinc paste is loaded into the injection device and injected into the zinc-manganese alkaline battery negative electrode cup at an injection rate of 0.8 mL / s. After compaction, the alkaline battery negative electrode is obtained. The compacted density of the zinc paste in the zinc-manganese alkaline battery negative electrode cup is 6.2 g / cm³. 3 ;

[0066] Before loading the zinc paste into the injection device, the zinc paste undergoes a static degassing treatment. The specific process is as follows: the zinc paste is placed in a static degassing tank, and high-purity nitrogen gas is injected from the bottom at a flow rate of 0.1 L / min for 30 minutes. Then, a laser particle analyzer is used to sample and detect the residual amount of air bubbles in the zinc paste, ensuring that the bubble particle size D90 ≤ 20 μm and the density ≤ 5 bubbles / mm. 3 .

[0067] Comparative Example 1

[0068] The difference between the alkaline battery negative electrode material and its preparation method in Comparative Example 1 and Example 1 is that in step S1, the zinc powder is not treated with supercritical carbon dioxide, and ordinary zinc powder is used.

[0069] Comparative Example 2

[0070] The difference between the alkaline battery negative electrode material and its preparation method in Comparative Example 2 and Example 1 is that in step S1, nitrogen heat treatment is used instead of boron-containing gas coating.

[0071] Comparative Example 3

[0072] The difference between the alkaline battery negative electrode material and its preparation method in Comparative Example 3 and Example 1 is that in step S2, only polyether-modified siloxane is used as the surfactant mother liquor.

[0073] Comparative Example 4

[0074] The difference between the alkaline battery negative electrode material and its preparation method in Comparative Example 4 and Example 1 is that in step S3, the KOH electrolyte is added all at once during the vacuum wet mixing process, instead of being added in stages.

[0075] Comparative Example 5

[0076] The difference between the alkaline battery negative electrode material and its preparation method in Comparative Example 5 and Example 1 is that in step S3, the vacuum-atmospheric pressure alternation mode is not activated, and vacuum stirring is used alone.

[0077] Comparative Example 6

[0078] The difference between the alkaline battery negative electrode material and its preparation method in Comparative Example 6 and Example 1 is that nitrogen degassing is not performed before paste filling in step S4.

[0079] Comparative Example 7

[0080] The difference between the alkaline battery negative electrode material and its preparation method in Comparative Example 7 and Example 1 is that in step S4, the compaction density of the paste is 4.9 g / cm³. 3 .

[0081] The following experiments were conducted on the alkaline batteries prepared in Examples 1-2 and Comparative Examples 1-7 to verify or understand their performance.

[0082]

[0083] Table 1 Comparison of Alkaline Battery Performance Test Data

[0084] As shown in Table 1 above, in the alkaline batteries prepared in Examples 1 and 2, the present invention uses supercritical carbon dioxide to permeate the zinc powder surface, which can remove the oxide film and adsorbed impurities on the zinc powder surface. Combined with a boron-containing atmosphere formed by triethylborane or methyl borate for low-temperature vapor-phase coating, a dense and stable nanoscale passivation film can be formed on the zinc powder surface. This effectively inhibits zinc powder corrosion and hydrogen evolution reaction while ensuring the smooth conduction path, thereby improving the storage safety of the alkaline battery. Secondly, the composite surfactant mother liquor is modified with polyether. The synergistic effect of silicone oil defoamers, fluorocarbon surfactants, and cationic wetting agents enables efficient wetting and stable dispersion of zinc powder, thereby improving the uniformity of zinc paste formation. Subsequently, combined with segmented speed-controlled stirring, batch feeding, and multi-round vacuum-atmospheric pressure switching defoaming process in a vacuum mixing vessel, residual bubbles can be effectively reduced, enhancing the density of the zinc paste. Finally, the particle size and density of bubbles are controlled through paste injection compaction and nitrogen defoaming processes to form a compact zinc paste, improving the conductivity of alkaline batteries and the capacity stability during long-term storage and use.

[0085] In Comparative Example 1, instead of supercritical carbon dioxide treatment, ordinary zinc powder was used, leaving residual oxidized impurities and adsorbed moisture on the surface of the zinc powder. These impurities are prone to self-corrosion and hydrogen evolution in an alkaline environment, increasing the risk of battery expansion during storage and discharge, reducing performance, and causing a significant decrease in capacity.

[0086] In Comparative Example 2, the zinc powder was not subjected to boron-containing vapor phase coating treatment, resulting in a lack of a stable passivation protective layer on the surface of the zinc powder. This made it prone to severe corrosion reactions in alkaline electrolytes, accelerating hydrogen evolution. Furthermore, the lack of a passivation film prevented the improvement of interfacial conductivity, leading to reduced electrochemical activity and shortened lifespan of the alkaline battery.

[0087] In Comparative Example 3, no composite surfactant mother liquor was added, resulting in poor wettability and dispersion performance of zinc powder surface, easy agglomeration between powder particles, and poor penetration and coating of liquid phase, which affected the mixing uniformity of zinc paste, formed discontinuous conductive path, and caused increased internal resistance and uneven paste injection.

[0088] In Comparative Example 4, a vacuum environment was not created during the stirring process. Air was easily entrained during mixing and was difficult to expel, resulting in a large number of micro air bubbles remaining in the zinc paste, forming pore interface defects. This not only reduced the effective reaction area of ​​the electrode but also affected the structural stability of the electrode.

[0089] In Comparative Example 5, although vacuum treatment was carried out during the stirring process, the mode of alternating between vacuum and atmospheric pressure was not adopted, which resulted in insufficient driving force for the release of bubbles, slow migration process, and difficulty in effective removal, leading to foam inclusion and accumulation of micro-defects, thereby affecting the density and conductivity of zinc paste.

[0090] In Comparative Example 6, the absence of hydroxypropyl methylcellulose caused the zinc paste to easily separate during mixing and injection, resulting in a loose structure and insufficient adhesion, which affected the injection quality and made it prone to structural expansion during long-term use.

[0091] In Comparative Example 7, the lack of nitrogen degassing treatment before paste application resulted in residual air bubbles inside the zinc paste not being released in time. This made it difficult to completely expel the gas during the subsequent compaction process, leaving hidden pores and thus affecting the capacity retention of the alkaline battery during long-term use.

[0092] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an alkaline battery negative electrode material, characterized in that, Includes the following steps: S1. Zinc powder pretreatment: Select spherical zinc powder with a particle size of 30-60μm, place the zinc powder in a supercritical carbon dioxide reactor, and treat it under a pressure of 6.5-7.5MPa for 30-50min. Then, treat the zinc powder with 0.01-0.03wt% boron element in a gas phase plasma coating process to passivate and modify the zinc powder. S2. Preparation of composite surfactant mother liquor: Polyether modified silicone oil defoamer, fluorocarbon surfactant and cationic wetting agent are mixed in a mass ratio of 4:2:1 to obtain an auxiliary agent mixture. The auxiliary agent mixture is dissolved in deionized water, wherein the mass ratio of the auxiliary agent mixture to deionized water is 100:

1. Then, the mixture is stirred with a magnetic stirrer for 20-30 minutes at a temperature of 23-28°C to fully disperse the additive mixture into a stable homogeneous liquid. Then, 1-2% ethanol is added as a co-solvent and stirred for 10-20 minutes to obtain the composite surfactant mother liquor. S3. Vacuum wet-mixed zinc paste: The pretreated zinc powder and the composite surfactant mother liquor are dry premixed at a mass ratio of 100:1-2. The mixture is placed in a rotary mixer at room temperature and stirred at a speed of 80-120 rpm for 5-10 minutes to obtain pre-wetted zinc powder. The pre-wetted zinc powder and KOH electrolyte were then placed in a vacuum stirring vessel and stirred to obtain zinc paste, wherein the volume ratio between the pre-wetted zinc powder and KOH electrolyte was 5:

1. S4. Load the zinc paste into the paste injection device and inject the zinc paste into the zinc-manganese alkaline battery negative electrode cup at a paste injection speed of 0.8-1.2 mL / s. After compaction, the alkaline battery negative electrode is obtained.

2. The method for preparing the alkaline battery negative electrode material according to claim 1, characterized in that, In step S3, the stirring process in the vacuum stirred tank is as follows: First, set the initial speed of the agitator to 300 rpm, start the jacket cooling water system, and maintain the temperature of the agitator at 23-25℃; Add KOH electrolyte, accounting for 8% of the total volume of the target zinc paste, to the vacuum stirred tank and stir for 5-7 minutes to form the initial liquid base layer; then add zinc powder and composite surfactant mother liquor evenly to the vacuum stirred tank through a screw propeller in three batches, with an interval of 2-3 minutes between each addition, and maintain stirring during the addition process; After the addition is completed, switch the vacuum stirring tank system to the first-level vacuum state. At this time, the pressure inside the vacuum stirring tank drops to -0.08MPa. Maintain this pressure and continue stirring for 5-10 minutes. Then, add KOH electrolyte accounting for 6% of the total volume of the target zinc paste to the vacuum stirring vessel, increase the stirring speed to 500-600 rpm, and simultaneously start the vacuum-atmospheric pressure cycle switching mode, switching between vacuum and atmospheric pressure every 3-5 minutes. After four cycles, stop stirring, turn off the vacuum system, and let it stand at atmospheric pressure for 6-8 minutes to allow the bubbles to rise and fall naturally. Add 6% KOH electrolyte (by total volume of the target zinc paste) and 0.2-0.6 wt% hydroxypropyl methylcellulose (by total mass of the zinc paste). Stir the mixture in a vacuum mixer at 600-700 rpm for 5 minutes to obtain the zinc paste.

3. The method for preparing the alkaline battery negative electrode material according to claim 1, characterized in that, In step S1, the specific process flow for zinc powder passivation modification is as follows: Spherical zinc powder is evenly spread in a material frame with sieve holes, with a thickness not exceeding 3cm. Then, the material frame is pushed into the inner cavity of the supercritical carbon dioxide reactor. After closing the reactor door, the pressure is gradually increased to 6.5-7.5MPa, and the temperature is controlled at 35℃±1℃. The circulation pump is started to circulate liquid carbon dioxide in the reactor at a flow rate of 20-30L / min for 30-50min. Then, the pressure is reduced to atmospheric pressure. Remove the zinc powder and air dry it in a drying room for 15-20 minutes. Then, place the air-dried zinc powder in a gas phase heat treatment chamber with an inert atmosphere protection function, and introduce a boron-containing gas containing 0.01-0.03 wt%, and introduce nitrogen or argon as a protective gas. The gas flow rate is controlled at 200-400 mL / min, and the temperature is controlled at 150-250℃. After reacting for 5-10 minutes, a nanoscale passivation film is formed on the surface of the zinc powder by boron, thereby completing the passivation modification treatment of the zinc powder surface.

4. The method for preparing the alkaline battery negative electrode material according to claim 1, characterized in that, In step S2, the polyether-modified silicone oil defoamer is a polyether-modified siloxane, the fluorocarbon surfactant is a fluorocarbon carboxylate, and the cationic wetting agent is a quaternary ammonium salt surfactant.

5. The method for preparing the alkaline battery negative electrode material according to claim 2, characterized in that, In step S3, after the zinc paste is prepared, the vacuum stirring vessel is switched to a secondary vacuum state. At this time, the pressure inside the vacuum stirring vessel drops to -0.095MPa. After stirring at low speed for 1-2 minutes, it is kept still.

6. The method for preparing the alkaline battery negative electrode material according to claim 5, characterized in that, Before loading the zinc paste into the injection device, the zinc paste is subjected to a static degassing treatment. The specific process is as follows: Zinc paste was placed in a settling degassing tank, and high-purity nitrogen gas was injected from the bottom at a flow rate of 0.1-0.3 L / min for 30-40 min. Then, a laser particle analyzer was used to sample and detect the residual amount of air bubbles in the zinc paste, ensuring that the bubble size D90 ≤ 20 μm and the density ≤ 5 bubbles / mm. 3 .

7. The method for preparing the alkaline battery negative electrode material according to claim 3, characterized in that, The thickness of the nanoscale passivation film is 10-20 nm.

8. The method for preparing the alkaline battery negative electrode material according to claim 3, characterized in that, The boron-containing gas is formed by heating and evaporating triethylborane or methyl borate.

9. The method for preparing the alkaline battery negative electrode material according to claim 1, characterized in that, In step S4, the compaction density of zinc paste in the negative electrode cup of the zinc-manganese alkaline battery is 6.2-6.8 g / cm³. 3 .

10. An alkaline battery negative electrode material, characterized in that, It is prepared by the method for preparing alkaline battery negative electrode material according to any one of claims 1-9.

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