Water supplementing type valve control lead storage battery positive electrode lead paste additive as well as preparation method and application of water supplementing type valve control lead storage battery positive electrode lead paste additive

Abstract

The invention provides a water replenishing type valve control lead storage battery positive electrode lead paste additive as well as a preparation method and application of the water replenishing type valve control lead storage battery positive electrode lead paste additive. The water supplementing type valve control lead storage battery positive electrode lead paste additive is a capsule with a core-shell structure, a shell layer is a polylactic acid-glycolic acid copolymer, and a core layer is polyethylene glycol. The capsule particles with the core-shell structure are added into the positive electrode active material, the fracture progress is controlled by utilizing the specific property of the wall material in electrochemical reaction, and water is continuously, stably and controllably released and supplemented into the battery through the sulfuric acid catalytic hydrolysis of the core material, so that the charging voltage rise is inhibited, the grid corrosion and the active material softening are slowed down, and the service life of the battery is prolonged.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lead storage batteries, and particularly relates to a positive lead paste additive for a water-supplementing valve-regulated lead storage battery and a preparation method and application thereof. BACKGROUND

[0002] Lead storage batteries are widely used in electric bicycles, automobile starting, energy storage and other fields due to low cost, high safety, mature technology and other advantages. However, the biggest problem of the traditional valve-regulated sealed lead storage battery in the charge-discharge cycle process is that the water in the electrolyte will be decomposed into hydrogen and oxygen due to the electrochemical reaction, resulting in water loss of the electrolyte. Especially in the later charging stage, the concentration of sulfuric acid is continuously increased, the voltage is also continuously increased, and the decomposition of water is more violent, which further aggravates the corrosion of the grid in the plate and the softening and falling of the active material due to the continuous impact of the gas, resulting in gradual capacity attenuation of the battery until the end of the service life. In order to compress the charging time and improve the charging efficiency, the long-term large-current constant-current charging method aggravates the premature termination of the battery life, and the quick charging gun provided on the market will also lead to the premature termination of the battery life if used for a long time. To solve the problem of water loss of the electrolyte during the use of the battery, the existing technology often adopts a sealed structure or adds a water supplementing device, but the sealed structure cannot completely avoid water loss due to the oxygen recombination efficiency and overpressure opening valve exhaust, and capacity attenuation will still occur during long-term use. The external water supplementing device is complex to operate and needs to be regularly maintained, and is not suitable for portable devices or specific scene use. In addition, some studies have also improved the performance of the battery by adding organic additives, but most of the additives are prone to side reactions with active materials or are quickly decomposed in an acidic environment, and cannot achieve long-term stable water supplementing effect.

[0003] Patent application No. CN105185948A discloses a lead-acid storage battery with automatic water supplementing function and a method for installing a lead-acid storage battery water supplementing reservoir. The lead-acid storage battery comprises a battery shell and a pole group. The water supplementing reservoir is inserted into the battery shell. The water supplementing reservoir comprises a bag made of porous acid-resistant flexible material. The bag contains a resin that becomes gel-like after absorbing water. The water supplementing reservoir uses one or more superabsorbent resins such as polyacrylamide, polyacrylate, starch, and cellulose to absorb a certain amount of water as a water supplementing source. A hydrophobic porous acid-resistant material such as PTFE, PP, and PE with a certain porosity and pore size is used to coat the outside of the water supplementing source to form a so-called water supplementing reservoir.

[0004] However, the patent application still has some deficiencies, which are as follows: (1) Difficulty in controlling the water replenishment rate: Although the patent application mentions that the porosity and pore size of the porous material determine the acid mist penetration rate, and in turn the water release rate of the water replenishment reservoir, it is not easy to accurately control the porosity and pore size to achieve a stable water replenishment rate that matches the battery life. In actual production, it may be difficult to ensure that the porosity and pore size of each water replenishment reservoir can reach the desired uniformity, which may result in differences in water replenishment rates among different batteries, affecting the consistency of the batteries and the performance of the entire battery group.

[0005] (2) Difficulty in achieving uniform water replenishment: Since the water replenishment reservoir is inserted from the outside of the shell into the battery and is stored in the upper part of the electrode group, the water released by the water replenishment reservoir gradually diffuses and penetrates from the upper part to the lower part of the positive and negative active materials, forming a concentration polarization, especially for liquid-starved valve-regulated batteries with a large aspect ratio of the electrode plate. For specific use conditions such as battery lying on one side, this water replenishment function cannot be achieved.

[0006] (3) Ineffective water replenishment under exceptional conditions: According to the technical conditions described in the patent application, as long as the water replenishment reservoir is under acidic conditions, the water source can continuously release water into the battery. From the end of production to the use of the finished battery, there will be a storage period of varying lengths, during which water is released. This result not only leads to a decrease in battery capacity, but also enhances the concentration polarization caused by the difference in sulfuric acid concentration, exacerbating self-discharge of the battery. Therefore, this water release is not only ineffective, but also negative. Especially for batteries that have been stored for a long time due to reasons, the water in the water replenishment reservoir may be depleted prematurely or the battery may be over-replenished with water, severely affecting the normal use and performance of the battery, leading to premature failure of the battery.

[0007] Patent application CN118431589A discloses a valve-regulated lead-acid battery maintenance structure and a maintenance method thereof, which includes a battery tank and a battery cover. The battery cover is provided with a pressure relief button switch and a liquid replenishment valve. A liquid guide pipe is installed in the battery tank, one end of the liquid guide pipe is connected with the liquid replenishment valve, and the other end is connected with a liquid distributor. The inner wall of the battery tank is provided with a plurality of flow guide grooves, which are open grooves. The flow guide grooves are communicated with cavities. The liquid distributor is provided with a plurality of flow guide ports, which are located above the flow guide grooves. Every 3-4 months of use or every 90-120 times of charge and discharge, the accumulated gas in the battery is discharged by pressing the pressure relief button switch, and then deionized water is supplemented through the liquid replenishment valve.

[0008] However, the patent application still has deficiencies, which are as follows: (1) The water supplement operation lacks precise control: the patent specifies that the battery should be supplemented with deionized water through a liquid supplement valve every 3-4 months or after completing 90-120 charge-discharge cycles, and the water supplement amount is 3-20 ml / Ah. In actual situations, on the one hand, the water loss of the battery may differ greatly under different use environments and working conditions, and this fixed period and fixed water supplement amount may not accurately meet the actual water supplement needs of the battery. On the other hand, non-professional operation may lead to insufficient or excessive water supplement, which may have a potential negative impact on the performance and service life of the battery.

[0009] (2) The complex structure increases the failure rate: the maintenance structure includes a battery cover, a pressure relief button switch, a liquid supplement valve, a liquid guide pipe, a liquid guide pipe support, a liquid distributor, a flow guide groove, and a partition limiting baffle, and the structure is relatively complex. Some key components are also placed inside the battery. Once a component fails, such as a blocked liquid guide pipe or a malfunctioning liquid supplement valve, it may affect the maintenance effect and normal use of the entire battery.

[0010] (3) The flow guide groove may be blocked after long-term use: the flow guide groove on the inner wall of the battery tank is used to guide the flow of liquid. However, impurities in the electrolyte and softened and shed active materials may accumulate in the flow guide groove during long-term use of the battery, causing the flow guide groove to be blocked, affecting the normal flow and distribution of the liquid, and causing a large deviation in the water supplement amount of each cell in the battery, making it difficult to achieve consistent water supplement.

[0011] Therefore, it is of great practical significance to develop a stable, continuous, and controllable water supplement technology that can uniformly distribute and maintain good compatibility with the active material inside the battery, to stabilize the performance of valve-regulated sealed lead-acid batteries and improve the cycle life of the battery. SUMMARY

[0012] To solve the above technical problems in the prior art, the present application provides a water supplement type valve-controlled lead-acid battery positive lead paste additive and a preparation method and application thereof.

[0013] The present application provides a water supplement type valve-controlled lead-acid battery positive lead paste additive, which is a capsule with a core-shell structure, wherein the shell layer is polylactic acid-glycolic acid copolymer (PLGA), and the core layer is polyethylene glycol (PEG).

[0014] Invention principle: 1. Polyethylene glycol can be hydrolyzed to generate water in stages under the catalysis of sulfuric acid with a density of about 1.34 g / ml, and the main process includes: 1) Initial stage of end ether bond hydrolysis, which is the reaction start-up period (corresponding to the early stage of battery cycle, when the capsule wall material just breaks), mainly generating ethylene glycol. Each broken ether bond consumes one molecule of water and generates one molecule of ethylene glycol. No water is generated directly, but it lays the foundation for subsequent oxidation to generate water. 2) the continuous stage of the hydrolysis of the intermediate ether bond, which is the main reaction stage (corresponding to the middle stage of battery cycle), and 1 molecule of water is consumed and 1 molecule of ethylene glycol is generated for each broken ether bond, but the generation of oligomers increases the subsequent oxidation reaction sites; 3) the water supplement core stage of the oxidation of the oligomers to generate water: about 2 mol of water can be generated for each 1 mol of ethylene glycol, and the oxidation reaction is synchronized with the battery charging process (O2 generated by the positive electrode is the oxidizing agent), without the need for additional addition of oxidizing agent; the generated CO2 will not accumulate inside the battery and will be discharged through the battery exhaust valve; the oxidation reaction rate is basically matched with the PEG hydrolysis rate, ensuring the continuous supplement of water generated in the electrolyte.

[0015] 2, the working mechanism of the polylactic acid-glycolic acid copolymer is as follows: the degradation process of PLGA under the action of high potential of the positive electrode is the result of the attack of ·OH free radicals generated by high potential on ester bonds: when the positive electrode potential exceeds a certain threshold, water molecules are activated to generate ·OH, which initiates the chain scission of PLGA molecules through hydrogen abstraction reaction, and finally leads to the rupture of the wall material and the supplement of the core material to the inside of the battery. This process is synchronized with the change of the positive electrode potential during battery charging, and the electrode potential is greater than 2.20V, that is, when the battery is in the charging state and the charge reaches about 90% of the rated capacity of the battery, the wall material degradation process is more obvious.

[0016] Preferably, the polylactic acid-glycolic acid copolymer is obtained by copolymerization of lactic acid (LA) and glycolic acid (GA) with a molar ratio of 50:50-90:10, the higher the molar ratio, the slower the degradation rate of the wall material; the molecular weight of the polylactic acid-glycolic acid copolymer is 5Da-150,000Da, the larger the molecular weight, the longer the rupture time of the wall material; the molecular weight of the polyethylene glycol is 1000Da-4000Da, the smaller the molecular weight, the faster the hydrolysis rate of the polyethylene glycol, and the more concentrated the water supplement released to the inside of the battery; the esterification rate of the terminal hydroxyl group of the polyethylene glycol is 0-30%, which can adjust the hydrolysis rate to realize the continuous and effective release of water, and the specific principle is as follows: the esterification reaction of the terminal hydroxyl group is to convert part of the hydroxyl group to ester group, which results in that, on the one hand, the polarity of the ester group is much lower than that of the hydroxyl group, which cannot form stable hydrogen bonds with H + The degree of protonation of the adjacent ether bond is reduced by 30%-50%, the unprotonated ether bond is difficult to be attacked by water molecules, and the hydrolysis reaction rate is significantly reduced; on the other hand, the alkyl chain in the ester group has a space volume effect, which forms a "shielding layer" at the end of the PEG molecular chain, preventing H + from approaching the ether bond and inhibiting the nucleophilic collision of water molecules with the protonated ether bond, thereby inhibiting the hydrolysis rate from two aspects and realizing the continuous release of water. The hydrolysis rate is reduced by 30%-40% for every 10% increase in the esterification rate of the terminal hydroxyl group.

[0017] Further preferably, the esterification rate of the terminal hydroxyl group of the polyethylene glycol is 10%-30%.

[0018] Preferably, the mass ratio of the polylactic acid-glycolic acid copolymer and the polyethylene glycol is 0.13-0.21:1.

[0019] Further preferably, the mass ratio of the polylactic acid-glycolic acid copolymer and the polyethylene glycol is 0.16:1.

[0020] Preferably, the particle size of the capsule particles is 1-50 μm, and the particle size of the capsule particles matches the particle size of the positive active material, ensuring that the capsule particles are compatible with the active material and uniformly dispersed.

[0021] The application also provides a preparation method of the above-mentioned water-supplementing additive for positive lead paste of valve-regulated lead-acid battery, which comprises the following steps:

[0022] Preferably, the preparation method comprises the following steps: (1) dissolving the polylactic acid-glycolic acid copolymer in an organic solvent to prepare a solution with a mass concentration of 5%-8%, i.e. a wall material solution; mixing the polyethylene glycol and water uniformly according to a mass ratio of 2.5-3:1 to obtain a core material dispersion; dissolving the polyvinyl alcohol in water to prepare a solution with a mass concentration of 2%-3%, i.e. a stabilizer solution; (2) mixing the wall material solution (oil phase) obtained in step (1) and the core material dispersion (water phase) according to a mass ratio of 1.5-2:1, and then performing high-speed shearing emulsification to form a W / O primary emulsion (water-in-oil emulsion); (3) uniformly mixing the W / O primary emulsion obtained in step (2) and the stabilizer solution (water phase) obtained in step (1) according to a volume ratio of 1:5 to obtain a W / O / W multiple emulsion (water-in-oil-in-water multiple emulsion), removing the organic solvent and the polyvinyl alcohol in the W / O / W multiple emulsion, and drying to obtain the water-supplementing additive for positive lead paste of valve-regulated lead-acid battery.

[0023] The polyvinyl alcohol solution with a mass concentration of 2%-3% as the stabilizer can be adsorbed on the surface of the droplets during the emulsification process, reduce the interfacial tension, prevent the droplets from agglomerating, and ensure that the capsule particles have uniform morphology and consistent size.

[0024] Further preferably, in step (1), the polylactic acid-glycolic acid copolymer is dissolved in an organic solvent to prepare a solution with a mass concentration of 6%, i.e. a wall material solution; the polyethylene glycol and water are mixed uniformly according to a mass ratio of 3:1 to obtain a core material dispersion; and the polyvinyl alcohol is dissolved in water to prepare a solution with a mass concentration of 2%, i.e. a stabilizer solution. In step (2), the wall material solution (oil phase) obtained in step (1) and the core material dispersion (water phase) are mixed in a mass ratio of 2:1, and then subjected to high-speed shearing emulsification to form a W / O type primary emulsion (water-in-oil emulsion).

[0025] Further preferably, the organic solvent is dichloromethane, which has good solubility and a low boiling point (about 39°C), and is easy to remove by volatilization.

[0026] Further preferably, in step (2), the rotation speed of high-speed shearing is 10,000 r / min-12,000 r / min, and the high-speed shearing time is 10 min-15 min, which can break the core material dispersion into small droplets.

[0027] Further preferably, in step (3), the W / O / W type re-emulsion is stirred for 4-6 h under an inert gas atmosphere at a temperature of 35°C to volatilize the organic solvent, and then subjected to centrifugal separation and washed with water to remove the residual organic solvent and polyvinyl alcohol.

[0028] The application also provides a water-supplementing type positive paste for valve-regulated lead-acid batteries, which comprises lead powder and the above-mentioned water-supplementing type positive paste additive for valve-regulated lead-acid batteries, and the mass of the water-supplementing type positive paste additive for valve-regulated lead-acid batteries is 0.3%-0.7% of the mass of the lead powder.

[0029] The application also provides a water-supplementing type positive plate for valve-regulated lead-acid batteries, which comprises a positive grid and a positive paste coated on the positive grid, and the positive paste is the above-mentioned water-supplementing type positive paste for valve-regulated lead-acid batteries.

[0030] Compared with the prior art, the application has the following beneficial effects: 1. Controllable water supplementing and prolonged cycle life: The rupture time of the PLGA wall material can be accurately controlled by adjusting the LA / GA ratio and the molecular weight, and the hydrolysis rate of the PEG core material can be controlled by adjusting the molecular weight and the esterification rate, so that the wall material can be ruptured in a timely and controllable manner, and the core material can be continuously, stably and controllably supplemented with water. Experiments show that the cycle life of the lead-acid battery of the application is prolonged by 30%-50% compared with conventional batteries.

[0031] 2. Good compatibility and no influence on battery performance: PLGA and PEG are both compatible materials, and the degradation products in an acidic environment are water and CO2, without impurity ions such as Cl - , NO3 - , and no side reactions occur with positive active materials (PbO2) and negative active materials (Pb). During the use of the battery, no artificial disturbance or intervention is required.

[0032] 3. Good water retention capacity, suitable for long-term storage: When the positive electrode potential exceeds the threshold value of 2.20V (battery charge is about 90% or more), the added capsule particles will show obvious breakage. That is, when the positive electrode voltage is less than 2.20V, the breakage is reduced or even does not occur. This technical feature provides favorable conditions for battery transportation, storage or special long-term storage, and has a positive effect on extending the service life of the battery.

[0033] 4. Mature process, easy to industrialize: The capsule particles are prepared by a mature emulsification-solvent evaporation method, which has low equipment cost. After industrialized quantitative production, the battery cost will also be significantly reduced. The preparation of positive and negative plates and the charging process of battery assembly are compatible with traditional lead-acid batteries, without the need to modify the existing production line. At the same time, the battery structure has not changed and is consistent with the traditional battery. Therefore, this technology has good application prospects. DETAILED DESCRIPTION

[0034] Example 1 1. Preparation of organic compound capsule particles: Step 1.1 Preparation of wall material solution: Dissolve polylactic acid-glycolic acid copolymer (PLGA, obtained by copolymerization of lactic acid and glycolic acid with a molar ratio of 90:10, molecular weight of 150,000 Da) in dichloromethane to prepare a PLGA solution with a mass concentration of 6%, and stir at a speed of 300 r / min and a temperature of 25°C until completely dissolved; Step 1.2 Preparation of core material dispersion: Mix polyethylene glycol (PEG, PEG molecular weight of 4000 Da, PEG terminal hydroxyl esterification rate of 30%) with deionized water at a mass ratio of 3:1, and stir at a speed of 500 r / min and a temperature of 30°C until a uniform dispersion is formed; Step 1.3 Preparation of stabilizer solution: Dissolve polyvinyl alcohol (PVA) with a molecular weight of 100,000 Da in deionized water to prepare a PVA solution with a mass concentration of 2%; Step 1.4 Primary emulsification: Slowly drop the core material dispersion into the wall material solution, with a mass ratio of core material to wall material solution of 1:2. Start the high-speed shearing emulsifier at a speed of 11000 r / min and a temperature of 25°C for 12 min to form a W / O type primary emulsion; Step 1.5 Re-emulsification: Slowly inject the W / O type primary emulsion into the stabilizer solution, with a volume ratio of primary emulsion to stabilizer solution of 1:5. Use a stirring paddle at a speed of 600 r / min and a temperature of 30°C for 35 min to form a W / O / W type re-emulsion; Step 1.6 solidification molding: the W / O / W type multiple emulsion is transferred into a three-necked flask with appropriate capacity, and the stirring is carried out at a rotation speed of 250 r / min and a temperature of 35°C, and the dichloromethane is volatilized by blowing nitrogen at a flow rate of 50 mL / min for 5 h; then the centrifugation is carried out at a rotation speed of 8000 r / min for 15 min, and the washing is carried out with deionized water for 3 times, and finally the drying is carried out in a vacuum drying box at a temperature of 40°C and a vacuum degree of -0.09 MPa for 8 h, so as to obtain the organic compound capsule particles, and the particle size of the capsule particles is 1 μm-50 μm.

[0035] 2. Preparation of positive plate The above-mentioned capsule particles 7 Kg (the mass of the capsule particles is 0.7% of the mass of the lead powder) are added into the conventional DZF positive plate component formula, and the 6-DZF-20 positive plate meeting the technical standard requirements is screened out after the processes of mixing, coating, plate solidification, drying, and screening. 3. Preparation of negative plate The 6-DZF-20 negative plate meeting the technical standard requirements is screened out after the processes of mixing, coating, plate solidification, drying, and screening according to the conventional DZF negative formula (in which the mass of the lead powder is 1T). 4. Assembly and charging of battery: the above-mentioned positive plate, negative plate, and standby specification AGM separator are sequentially stacked and wrapped to form a plate group, and the 6-DZF-20 semi-finished battery is assembled into a plastic shell, and the dilute sulfuric acid electrolyte is injected, and the charging and formation are carried out according to the conventional charging process, and the water-supplementing type valve-regulated sealed lead storage battery is obtained after sealing.

[0036] Example 2 The difference from Example 1 is that the molecular weight of PEG is 3000 Da, and the esterification rate of the terminal hydroxyl group of PEG is 20%.

[0037] Example 3 The difference from Example 1 is that the PLGA is obtained by copolymerization of lactic acid and hydroxyacetic acid with a molar ratio of 50:50, and the molecular weight is 50,000 Da; the molecular weight of PEG is 3000 Da, and the esterification rate of the terminal hydroxyl group of PEG is 20%.

[0038] Example 4 The difference from Example 1 is that the PLGA is obtained by copolymerization of lactic acid and hydroxyacetic acid with a molar ratio of 70:30, and the molecular weight is 100,000 Da.

[0039] Example 5 The difference from Example 1 is that the PLGA is obtained by copolymerization of lactic acid and hydroxyacetic acid with a molar ratio of 70:30, and the molecular weight is 100,000 Da; the molecular weight of PEG is 1000 Da, and the esterification rate of the terminal hydroxyl group of PEG is 10%.

[0040] Example 6 The difference from Example 1 is that 5 Kg of the capsule particles (0.5% of the mass of the lead powder) are added to the components of the conventional DZF positive plate formula during the preparation of the positive plate.

[0041] Example 7 The difference from Example 1 is that 3 Kg of the capsule particles (0.3% of the mass of the lead powder) are added to the components of the conventional DZF positive plate formula during the preparation of the positive plate.

[0042] Example 8 The difference from Example 1 is that the battery is left to stand at room temperature for 3 months after the assembly and charging of the rechargeable valve-regulated lead-acid battery.

[0043] Comparative Example 1 The difference from Example 1 is that no organic compound capsule particles are added during the preparation of the positive plate.

[0044] Example 9 1. Organic compound capsule particles: The same as in Example 1.

[0045] 2. Preparation of the positive plate: 5 Kg of the capsule particles (0.5% of the mass of the lead powder) are added to the components of the conventional EVF positive plate formula, and the 6-EVF-100 positive plates that meet the technical standard requirements are selected after pasting, sheeting, curing and drying of the plates; 3. Preparation of the negative plate: The 6-EVF-100 negative plates that meet the technical standard requirements are selected after pasting, sheeting, curing and drying of the plates according to the conventional EVF negative formula (wherein the mass of the lead powder is 1T); 4. Assembly and charging of the battery: the above positive plates, negative plates and AGM separators of the standby specification are sequentially stacked and wrapped to form a plate group, which is assembled into a 6-EVF-100 semi-finished battery in a plastic shell, and is injected with dilute sulfuric acid electrolyte, and is charged and formed according to the conventional charging process, and the rechargeable valve-regulated lead-acid battery is obtained after sealing.

[0046] Example 10 The difference from Example 9 is that 3 Kg of the capsule particles (0.3% of the mass of the lead powder) are added to the components of the conventional EVF positive plate formula during the preparation of the positive plate.

[0047] Example 11 The difference from Example 9 is that 7 Kg of the capsule particles (0.7% of the mass of the lead powder) are added to the components of the conventional EVF positive plate formula during the preparation of the positive plate.

[0048] Example 12 The difference from Example 9 is that 7 kg of capsule particles (0.7% of the lead powder mass) were added to the conventional EVF positive electrode plate composition during the preparation of the positive electrode plate; after the battery was assembled and charged to obtain a water-filled valve-regulated sealed lead-acid battery, the battery was left to stand at room temperature for 3 months.

[0049] Comparative Example 2 The difference from Example 9 is that no organic compound capsule particles are added during the preparation of the positive electrode plate.

[0050] Test Example 1 According to Examples 1-12 and Comparative Examples 1-2, each example was tested twice in parallel to prepare two batteries, named 1# and 2#. The cycle life of these batteries was tested, and the voltage value after standing for 48 hours during the cycle, the voltage difference per 100 cycles, and the water loss rate of the batteries were measured. The test results are shown in Table 1-2.

[0051] Table 1 Table 2 Based on the analysis of the test results, the following conclusions can be drawn: 1. Battery cycle life evaluation 1) The impact of adding capsule particles on battery life: The cycle life of batteries with capsule particles is higher than that of conventional batteries without capsule particles. Specifically, the longest cycle life of batteries with capsule particles is about 50% higher than that of conventional batteries, indicating that adding capsule particles helps extend battery cycle life. 2) Effect of different capsule particle addition ratios on battery cycle life: The cycle life of the battery with capsule particle mass of 0.5% of the lead powder mass (Example 6) > The cycle life of the battery with capsule particle mass of 0.7% of the lead powder mass (Example 1) > The cycle life of the battery with capsule particle mass of 0.3% of the lead powder mass (Example 7). The same conclusion was reached in comparison with Examples 9-11. The main reason may be that if the addition ratio of capsule particles is too low, the water replenishment is insufficient. If the addition ratio is too high, while providing sufficient water replenishment to the battery, it will also reduce the strength between active materials and the strength between active materials and the conductor grid, which will have a negative impact on battery life.

[0052] 3) The influence of different capsule particle parameters on the cycle life of the battery: under the condition of adding the same mass ratio, the cycle life of the battery of Example 2 > the cycle life of the battery of Example 4 > the cycle life of the battery of Example 1 > the cycle life of the battery of Example 5 > the cycle life of the battery of Example 3, indicating that the wall material PLGA and the core material PEG have a significant influence on the cycle life of the battery, and the overall trend is that the higher the LA / GA ratio in the wall material PLGA and the larger the molecular weight, the larger the molecular weight of the core material PEG and the higher the esterification rate of the terminal hydroxyl group, the longer the cycle life of the battery, and vice versa, the cycle life of the battery is shortened.

[0053] 4) The influence of adding capsule particles and long-term standing on the cycle life of the battery: comparing Example 8 and Example 1, it can be found that under the condition of the same capsule particle parameters and the same addition ratio, the cycle life data of the battery standing for 3 months is basically close to that of the battery without standing, indicating that during the standing of the battery, the wall material PLGA in the capsule particles is not significantly damaged, and maintains good water locking capacity, providing sufficient conditions for water replenishment in the later cycle process.

[0054] 2, Voltage rise amplitude evaluation at the end of battery cycle 1) The influence of adding capsule particles on the voltage rise amplitude during the cycle process: the single voltage rise amplitude of the battery with added capsule particles (i.e. the single voltage rise value in Table 1) is significantly lower than that of the conventional battery (Comparative Examples 1-2), indicating that the conventional battery without added capsule particles has a large increase in sulfuric acid concentration during the cycle process, that is, more water loss, accompanied by increased voltage, accelerated corrosion of the grid, and accelerated softening of the active material due to gas evolution, resulting in premature termination of the cycle life of the battery. The battery with added capsule particles delays (or inhibits) the increase in sulfuric acid concentration during the cycle process due to the hydrolysis of the capsule particles, delays the softening time of the active material and the corrosion of the grid, thereby prolonging the cycle life of the battery. 2) The influence of different addition ratios on the voltage rise amplitude during the cycle process: the voltage rise amplitude of the battery with 0.5% capsule particles by mass of lead powder < the voltage rise amplitude of the battery with 0.7% or 0.3% capsule particles by mass of lead powder (the difference in voltage rise amplitude between the battery with 0.7% capsule particles by mass of lead powder and the battery with 0.3% capsule particles by mass of lead powder is not obvious), indicating that a suitable addition ratio helps to inhibit the voltage rise, slow down the corrosion of the grid and the evolution of gas, and helps to prolong the cycle life of the battery.

[0055] 3) Effect of adding capsule particles and long time standing on the voltage rise during cycling: Comparing Example 8 and Example 1 or comparing Comparative Example 11 and Example 12, it can be found that under the condition of same parameters of capsule particles and same adding proportion, the voltage rise of the battery standing for 3 months is obviously higher than that of the battery without standing, which is mainly caused by the deviation of the lower initial voltage value (0th voltage value in Table 1) of the battery due to the self-discharge during long time standing, not by the battery cycling, if the 100th voltage value in Table 1 is taken as the basis, the voltage rise of the two kinds of batteries has little difference. It shows that the wall material keeps well during the standing of the battery, and the capsule particles are not obviously damaged.

[0056] 3) Evaluation of the water loss rate at the end of battery cycling 1) Effect of adding capsule particles on the water loss rate during cycling: the water loss rate of the battery with added capsule particles is obviously lower than that of the conventional battery without added capsule particles, which shows that adding capsule particles helps to reduce the electrolysis (consumption) of water during the cycling of the battery, and prolongs the cycle life of the battery. 2) Effect of different adding proportions on the water loss rate during cycling: the cycle life of the battery with 0.5% capsule particles by weight of lead powder < the cycle life of the battery with 0.7% capsule particles by weight of lead powder < the cycle life of the battery with 0.3% capsule particles by weight of lead powder, which shows that the appropriate adding proportion of capsule particles helps to reduce the water loss during the cycling of the battery, and prolongs the cycle life.

[0057] 3) Effect of adding capsule particles and long time standing on the water loss rate during cycling: comparing Example 8 and Example 1, it can be found that under the condition of same parameters of capsule particles and same adding proportion, the water loss rate data of the battery standing for 3 months is basically similar to that of the battery without standing, which shows that the wall material PLGA in the capsule particles keeps good water locking ability without being obviously damaged during the standing of the battery.

Claims

1. A water-replenishing type valve-regulated lead-acid battery positive electrode lead paste additive, characterized in that, It is a core-shell capsule, wherein the shell is a polylactic acid-glycolic acid copolymer and the core is polyethylene glycol.

2. The water-replenishing type valve-regulated lead-acid battery positive electrode lead paste additive according to claim 1, characterized in that, The polylactic acid-glycolic acid copolymer is obtained by copolymerizing lactic acid and glycolic acid in a molar ratio of 50:50-90:10, and the molecular weight of the polylactic acid-glycolic acid copolymer is 5 Da-150,000 Da; the molecular weight of the polyethylene glycol is 1,000 Da-4,000 Da, and the esterification rate of the terminal hydroxyl groups of the polyethylene glycol is 0-30%.

3. The water-replenishing type valve-regulated lead-acid battery positive electrode lead paste additive according to claim 1, characterized in that, The mass ratio of the polylactic acid-glycolic acid copolymer to polyethylene glycol is 0.13-0.21:

1.

4. The water-replenishing type valve-regulated lead-acid battery positive electrode lead paste additive according to claim 1, characterized in that, The particle size of the capsule particles is 1μm-50μm.

5. The method for preparing the water-replenishing valve-regulated lead-acid battery positive electrode lead paste additive according to any one of claims 1-4, characterized in that, The preparation method involves using polylactic acid-hydroxyacetic acid copolymer and polyethylene glycol to form a core-shell structured capsule through an emulsification-solvent evaporation method, thereby obtaining the water-replenishing valve-regulated lead-acid battery positive electrode lead paste additive.

6. The method for preparing the water-replenishing valve-regulated lead-acid battery positive electrode lead paste additive according to claim 5, characterized in that, The preparation method includes the following steps: (1) Dissolve polylactic acid-glycolic acid copolymer in an organic solvent to prepare a solution with a mass concentration of 5%-8%, i.e., wall material solution; mix polyethylene glycol and water at a mass ratio of 2.5-3:1 to obtain core material dispersion; dissolve polyvinyl alcohol in water to prepare a solution with a mass concentration of 2%-3%, i.e., stabilizer solution; (2) The wall material solution and core material dispersion obtained in step (1) are mixed at a mass ratio of 1.5-2:1, and then subjected to high-speed shear emulsification to form a W / O type primary emulsion; (3) The W / O type primary emulsion obtained in step (2) and the stabilizer solution obtained in step (1) are mixed uniformly at a volume ratio of 1:5 to obtain a W / O / W type double emulsion. The organic solvent and polyvinyl alcohol in the W / O / W type double emulsion are removed and dried to obtain the water-replenishing valve-regulated lead-acid battery positive electrode lead paste additive.

7. The method for preparing the water-replenishing type valve-regulated lead-acid battery positive electrode lead paste additive according to claim 6, characterized in that, The organic solvent is dichloromethane.

8. The method for preparing the lead paste additive for the positive electrode of a water-replenishing valve-regulated lead-acid battery according to claim 6, characterized in that, In step (2), the rotation speed of the high-speed shearing is 10000r / min-12000r / min, and the high-speed shearing time is 10min-15min.

9. A type of water-replenishing valve-regulated lead-acid battery positive electrode lead paste, characterized in that, It includes lead powder and the water-replenishing valve-regulated lead-acid battery positive electrode lead paste additive as described in any one of claims 1-4, wherein the mass of the water-replenishing valve-regulated lead-acid battery positive electrode lead paste additive is 0.3%-0.7% of the mass of lead powder.

10. A water-replenishing type valve-regulated lead-acid battery positive plate, comprising a positive plate grid and positive lead paste coated on the positive plate grid, characterized in that, The positive electrode paste is the water-replenishing valve-regulated lead-acid battery positive electrode paste as described in claim 9.

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