A method for treating an externalized negative electrode plate to prevent oxidation

Abstract

The present invention provides an oxidation-resistant externalized negative plate treatment method, wherein the negative plate after externalization is discharged and charged by a step-by-step current, so that a lead sulfate protective layer is generated on the surface of the negative plate without affecting the negative electrode capacity, and the oxidation of the negative plate during the drying process is prevented by combined immersion in a xylitol solution. The dry-load storage performance of the negative plate is also improved accordingly. The treatment method of the present invention is used to repeatedly discharge the negative plate with a large current shallowly, and the lead oxide content of the negative plate decreases after drying, and the dry-load capacity of the negative electrode is increased. The charging amount of the battery after acid addition can also be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of battery production, in particular to an oxidation-resistant externalized negative electrode plate processing method. Background Art

[0002] Battery plate manufacturing is divided into green plate manufacturing and cooked plate manufacturing. Currently, most companies use green plate assembly and charging to manufacture batteries. Compared with the green plate internalization process for battery manufacturing, the cooked plate manufacturing process has a relatively short production cycle and low power load requirements, and still occupies a certain market share.

[0003] When manufacturing cooked plates, the green plates must be chemically processed to convert the positive lead paste into active lead dioxide and the negative lead paste into spongy lead. Lead is highly active and easily reacts with oxygen to form lead oxide. Since the negative plates are exposed to the air after being washed and heated and dried under these conditions, this process easily reacts with oxygen to form lead oxide. Long-term storage makes the negative spongy lead lose its activity and cannot discharge electricity. Therefore, the sample preparation technology of the negative plate is particularly important in battery dissection analysis.

[0004] The patent application with publication number CN101388456A discloses a method for treating the formation plates of lead-acid batteries by discharging without washing, which includes the steps of preparing a treatment solution, discharging acid solution, adding a treatment solution, discharging, treating the negative plate, treating the positive plate, and preparing a treatment solution in a cycle. A method for treating the formation plates of lead-acid batteries by reverse charging without washing is also disclosed, which includes the steps of preparing a treatment solution, making a treatment tank, adding a treatment solution, inserting a negative plate, reverse charging, treating the negative plate, preparing a treatment solution in a cycle, and washing the positive plate. The invention uses a discharge or reverse charging method to treat the formation plates, and the required treatment effect can be achieved without washing. During the discharge process, the plate generates PbSO4 that adheres to the surface of the plate holes, which can play a protective role and prevent the negative plate from further oxidation, thereby improving the dry charge performance of the plate. That is, after formation, discharge at 30-50% of the formation current for 20-30 minutes, and then wash with sodium hydroxide and soak in boric acid solution to improve the above problems. However, when the above method is used for discharge, too much electricity is released, and more lead sulfate is generated at the negative electrode, which affects the capacity of the negative electrode, and the residues after washing with sodium hydroxide solution are impurities, which ultimately affect the battery performance. Some companies use anaerobic drying to improve oxidation during the drying process of the negative electrode, but the actual effect after treatment is not good. On the other hand, after the battery is assembled and acid is added, the lead oxide further reacts with sulfuric acid, making it difficult to add acid, and the battery must be charged with excessive electricity, which affects the company's benefits.

[0005] After the negative plate is formed, it is a light grey sponge-like lead with high porosity, large surface area, and extremely high activity, which is in a thermodynamically unstable state. Therefore, during the drying and storage process, it is very easy to react with oxygen in the air to generate PbO, which sometimes has a light yellow color. Severely oxidized negative plates affect the capacity and life of the battery.

[0006] In addition to adding antioxidants to the lead paste formula, the negative plate also needs post-formation treatment to prevent oxidation. There are generally two methods, one is to soak the negative plate in boric acid; the other is to soak it in xylitol. This is a method for producing dry-charged electrode plates, the purpose of which is to protect the activity of the lead in the negative plate from being oxidized to PbO during storage. Since boric acid has a low solubility at room temperature, it needs to be heated before use, generally at 50-65°C, with a concentration of about 5%, and an immersion time of 10-15 minutes. Heating makes the use of boric acid more troublesome. Xylitol is available in liquid form, with a content of 60%-80%; and in crystalline solid form, with a content of 96%. Xylitol is easily soluble in water, with a usage content of 2%-3% and a density of 10.2-1.03g / cm 3 The plate soaked in xylitol is dried at a temperature below 150°C.

[0007] Currently, there is no report on the process of increasing the anti-oxidation performance of the negative plate by discharging and charging the negative plate in a step-by-step current manner after externalization. Summary of the invention

[0008] The present invention provides an anti-oxidation externalized negative plate treatment method, which discharges and charges the externalized negative plate through a step-by-step current, so that a lead sulfate protective layer is generated on the surface of the negative plate without affecting the negative electrode capacity, and the oxidation of the negative plate during the drying process is prevented by combined immersion in a xylitol solution. The dry charge storage performance of the negative plate is also improved accordingly.

[0009] The technical solution of the present invention is as follows:

[0010] A method for treating an externalized negative electrode plate to prevent oxidation, comprising the following steps:

[0011] (1) Insert the green plate into the formation tank for the first charge;

[0012] (2) After charging is completed, the plates are left in the formation tank for the first discharge and the second charge. The units of the discharge current and the charge current are both amperes. The values ​​of the discharge current and the charge current are calculated according to the following formula:

[0013] Discharge current value = (L×H)×M×N×X,

[0014] Where: L is the length of the plate in centimeters.

[0015] H is the width of the plate in centimeters.

[0016] M is the number of small plates contained in the large plate.

[0017] N is the number of large negative plates in the formation tank;

[0018] X represents the coefficient, and the value range of X is 0.01 to 0.02;

[0019] Charging current value = Y × discharging current value;

[0020] Where: Y represents the coefficient, and the value range of Y is 0.1~0.15;

[0021] Among them, the large plate pieces are cut into small plate pieces;

[0022] (3) discharging the negative electrode plate for a second time, charging it for a third time, and discharging it for a third time with the discharge current and charge current in step (2);

[0023] (4) After the plate is washed to neutrality in step (3), the positive plate is directly dried, and the negative plate is immersed in a xylitol aqueous solution, taken out and dried to obtain an oxidation-resistant externalized negative plate.

[0024] The formula in step (2) calculates the value of the charging current and the value of the discharging current, and the unit of the discharging current and the charging current is ampere.

[0025] The first charge time is generally within 24 hours, preferably 21±1 hours, and the charge amount is 7.5±0.1 times the plate capacity.

[0026] In step (1), during the charging process, the level of the chemical formed is higher than the upper edge of the green plate.

[0027] Preferably, in step (2), the first discharge time is 3-5 minutes, and the second charge time is 5 times the first discharge time.

[0028] Preferably, in step (3), the second discharge time is 60%±5% of the first discharge time.

[0029] Preferably, in step (3), the third charging time is 60%±5% of the second charging time.

[0030] Preferably, in step (3), the third discharge time is 30%±5% of the first discharge time.

[0031] Each time the negative electrode is discharged at a high current, a layer of lead sulfate is generated on the surface. Then, a small current is charged to reduce the lead sulfate on the inner side. Since the generated lead sulfate layer is shallow, the influence of the lead sulfate layer on the capacity is negligible.

[0032] Preferably, in step (4), the mass percentage concentration of the xylitol aqueous solution is 5%-7%.

[0033] Preferably, in step (4), the negative electrode plate is immersed in the xylitol aqueous solution and then allowed to stand for 10-15 minutes.

[0034] By adopting the treatment method of the present invention to repeatedly discharge the negative plate with a large current shallowly, the lead oxide content of the negative plate decreases after drying, and the negative electrode dry charge capacity increases, which can reduce the charging amount of the battery after acid addition.

[0035] The present invention adopts a large current stage discharge-charge-discharge-charge-discharge according to the surface area of ​​the battery, so that a lead sulfate protective layer is formed on the surface of the negative electrode, thereby improving the oxidation of the negative electrode lead during the drying process.

[0036] The present invention uses high current stages of discharge-charge-discharge-charge-discharge, and the total amount of electricity in each stage is gradually reduced, so as to prevent the negative electrode from generating excessive lead sulfate. Finally, the overall increase of lead sulfate is small, and the capacity of the negative electrode is not affected.

[0037] The invention reduces the negative electrode lead oxide after immersing in a xylitol solution and drying, improves the electrical performance of the assembled battery after acid addition, and maintains stable electrical performance of the assembled acid-added battery after the pole plates are stored. DETAILED DESCRIPTION

[0038] Example 1

[0039] The large pieces of 6-DZF-20 plates are 4-pieces, the size of the small pieces is 6.6×13.8cm, and the capacity of the large pieces is 20Ah. Insert the positive electrode plate 25 large pieces and the negative electrode plate 26 large pieces into the formation tank alternately and charge continuously at 180A for 21 hours (the time is generally within 24 hours, 21±1 hours is appropriate, and the charge amount is 7.5±0.1 times the capacity of the plate.). After charging, the plate is left in the formation tank without being taken out and discharged at 142A for 3 minutes, then charged at 17.8A for 15 minutes; then discharged at 142A for 1.8 minutes, charged at 17.8A for 9 minutes; finally discharged at 142A for 0.9 minutes.

[0040] Take out the plate, wash it in running water until it is neutral, then dry the positive plate directly, and evenly immerse the negative plate in a 5% xylitol aqueous solution, and let it stand for 12.5 minutes. Take out the plate and quickly transfer it to a drying kiln to dry it at 110°C to obtain the desired negative plate.

[0041] Comparative Example 1

[0042] The large pieces of 6-DZF-20 plates are 4-pieces, the size of the small pieces is 6.6×13.8cm, and the capacity of the large pieces is 20Ah. Insert the positive and negative large pieces of 25 large pieces of plates and 26 large pieces of plates alternately into the formation tank and charge continuously at 180A for 21 hours. After charging, take out the plates, put them in running water to clean them until they are neutral, then take out the positive and negative plates to the drying kiln and dry them at 110℃ to obtain the plates, and take out the negative plates to the oxygen-free dryer to dry them to obtain the plates.

[0043] Comparative Example 2

[0044] The large pieces of 6-DZF-20 plates are 4-pieces, the size of the small pieces is 6.6×13.8cm, and the capacity of the large pieces is 20Ah. Insert 25 large pieces of positive plates and 26 large pieces of negative plates into the formation tank alternately, and charge continuously at 180A for 21 hours. After charging, take out the plates, put them in running water to clean them until they are neutral, then dry the positive plates directly, and evenly disperse the negative plates and immerse them in a saturated boric acid solution, and let them stand for 12.5 minutes. Take out the plates and quickly transfer them to a drying kiln to dry them at 110°C to obtain the required negative plates.

[0045] Comparative Example 3

[0046] The large pieces of 6-DZF-20 plates are 4-pieces, the size of the small pieces is 6.6×13.8cm, and the capacity of the large pieces is 20Ah. Insert 25 large pieces of positive plates and 26 large pieces of negative plates into the formation tank alternately and charge continuously at 180A for 21 hours. After charging, discharge at 90A for 20 minutes. Then put the plates into running water to clean until neutral, then directly dry the positive plates, and evenly disperse the negative plates and immerse them in a saturated boric acid solution and let them stand for 12.5 minutes. Take out the plates and quickly transfer them to a drying kiln to dry at 110°C to obtain the required negative plates.

[0047] Example 2

[0048] The large pieces of 6-DZF-12 plates are 9-pieces, the size of the small pieces is 4.5×7.4cm, and the capacity of the large pieces is 15.43Ah. 25 large pieces of positive plates and 26 large pieces of negative plates are inserted into the formation tank alternately and charged continuously at 146.6A for 20 hours. After charging, the plates are left in the formation tank without being taken out and discharged at 78A for 4 minutes, then charged at 7.8A for 20 minutes; then discharged at 78A for 2.4 minutes, charged at 7.8A for 12 minutes; and finally discharged at 78A for 1.2 minutes.

[0049] Take out the plate, wash it in running water until it is neutral, then dry the positive plate directly, and immerse the negative plate in a 6% xylitol aqueous solution evenly, and let it stand for 15 minutes. Take out the plate and quickly transfer it to a drying kiln to dry it at 110°C to obtain the desired negative plate.

[0050] Comparative Example 4

[0051] The large pieces of 6-DZF-12 plates are 9-pieces, the size of the small pieces is 4.5×7.4cm, and the capacity of the large pieces is 15.43Ah. 25 large pieces of positive plates and 26 large pieces of negative plates are inserted into the formation tank alternately, and charged continuously at 146.6A for 20 hours. After charging, take out the plates, put them in running water to clean them until they are neutral, then take out the positive plates and dry them in a drying kiln at 110℃ to obtain the plates, and take out the negative plates and dry them in an oxygen-free dryer to obtain the plates.

[0052] Comparative Example 5

[0053] The large pieces of 6-DZF-12 plates are 9-pieces, the size of the small pieces is 4.5×7.4cm, and the capacity of the large pieces is 15.43Ah. Insert 25 large pieces of positive plates and 26 large pieces of negative plates into the formation tank alternately, and charge continuously at 146.6A for 20 hours. After charging, take out the plates, put them in running water to clean them until they are neutral, then dry the positive plates directly, and evenly disperse the negative plates and immerse them in a saturated boric acid solution, and let them stand for 15 minutes. Take out the plates and quickly transfer them to a drying kiln to dry them at 110°C to obtain the required negative plates.

[0054] Comparative Example 6

[0055] The large pieces of 6-DZF-12 plates are 9-pieces, the size of the small pieces is 4.5×7.4cm, and the capacity of the large pieces is 15.43Ah. Insert 25 large pieces of positive plates and 26 large pieces of negative plates into the formation tank alternately, and charge continuously at 146.6A180A for 20 hours. After charging, discharge at 90A for 20 minutes. Then put the plates into running water to clean until neutral, then directly dry the positive plates, and evenly disperse the negative plates and immerse them in a saturated boric acid solution, and let them stand for 15 minutes. Take out the plates and quickly transfer them to a drying kiln to dry at 110°C to obtain the required negative plates.

[0056] Example 3

[0057] The large 6-FM-17 plates are 4-pieces, the small size is 6.6×12.2cm, and the capacity of the large plates is 17Ah. 25 large positive plates and 26 large negative plates are inserted into the formation tank alternately and charged continuously at 148.7A for 22 hours. After charging, the plates are left in the formation tank without being taken out and discharged at 167A for 5 minutes, then charged at 25A for 25 minutes; then discharged at 167A for 3 minutes, charged at 25A for 15 minutes; finally discharged at 167A for 1.5 minutes.

[0058] Take out the plate, wash it in running water until it is neutral, then dry the positive plate directly, and immerse the negative plate in a 6% xylitol aqueous solution evenly, and let it stand for 10 minutes. Take out the plate and quickly transfer it to a drying kiln to dry it at 110°C to obtain the desired negative plate.

[0059] Comparative Example 7

[0060] The large pieces of 6-FM-17 plates are 4-pieces, the size of the small pieces is 6.6×12.2cm, and the capacity of the large pieces is 17Ah. Insert 25 large pieces of positive plates and 26 large pieces of negative plates alternately into the formation tank and charge continuously at 148.7 for 22 hours. After charging, take out the plates, put them in running water to clean them until they are neutral, then take out the positive plates and dry them in a drying kiln at 110℃ to obtain the plates, and take out the negative plates and dry them in an oxygen-free dryer to obtain the plates.

[0061] Comparative Example 8:

[0062] The large pieces of 6-FM-17 plates are 4-pieces, the size of the small pieces is 6.6×12.2cm, and the capacity of the large pieces is 17Ah. Insert 25 large pieces of positive plates and 26 large pieces of negative plates into the formation tank alternately and charge continuously at 148.7 for 22 hours. After charging, take out the plates, put them in running water to clean them until they are neutral, then dry the positive plates directly, and evenly disperse the negative plates and immerse them in a saturated boric acid solution and let them stand for 10 minutes. Take out the plates and quickly transfer them to a drying kiln to dry them at 110°C to obtain the required negative plates.

[0063] Comparative Example 9:

[0064] The large pieces of 6-FM-17 plates are 4-pieces, the size of the small pieces is 6.6×12.2cm, and the capacity of the large pieces is 17Ah. Insert 25 large pieces of positive plates and 26 large pieces of negative plates into the formation tank alternately and charge continuously at 148.7 for 22 hours. After charging, discharge at 90A for 20 minutes. Then put the plates into running water to clean until neutral, then directly dry the positive plates, and evenly disperse the negative plates and immerse them in a saturated boric acid solution and let them stand for 10 minutes. Take out the plates and quickly transfer them to a drying kiln to dry at 110°C to obtain the required negative plates.

[0065] Test Example 1

[0066] Ten negative plates prepared in Example 1 and Comparative Examples 1-3 were taken respectively, and the data of lead oxide and lead sulfate of the negative plates were measured and shown in Table 1-4.

[0067] Table 1: Content of lead oxide and lead sulfate in the negative plate prepared in Example 1 (%)

[0068]

[0069] Table 2: Content of lead oxide and lead sulfate in the negative electrode plate prepared in Comparative Example 1 (%)

[0070]

[0071] Table 3: Content of lead oxide and lead sulfate in the negative electrode plate prepared in Comparative Example 2 (%)

[0072]

[0073] Table 4: Content of lead oxide and lead sulfate in the negative electrode plate prepared in Comparative Example 3 (%)

[0074]

[0075]

[0076] The plates prepared in Example 1 and Comparative Examples 1-3 were assembled into a single cell with 2 negative plates and 3 positive plates of the same gram weight in a 6-DZF-20 battery (one less negative plate, in this case the positive electrode capacity is excessive), and 4 batteries were prepared. After the battery was acidified, it was directly discharged at 7.5A without supplementary electricity, and the measured data were shown in Table 5:

[0077] Table 5: Battery 7.5A discharge time

[0078]

[0079] The plates prepared in Example 1 and Comparative Examples 1-3 were stored at 25 degrees for three months. Two negative plates and three positive plates of the same weight were assembled into a single cell in a 6-DZF-20 battery. Four batteries were prepared in each case. After the battery was acidified, it was directly discharged at 7.5A without additional charge. The measured data are shown in Table 6:

[0080] Table 6: Battery 7.5A discharge time

[0081]

[0082] The above data show that the lead oxide content of the negative plate prepared in the embodiment is the lowest and the lead sulfate content in the plate is not greatly affected by the treatment method of the present invention, and the dry charge performance of the negative plate is the best. The negative electrode capacity of the negative plate changes little after storage, and the performance is better than the plates prepared by other processes.

Claims

1. A method for treating an externalized negative electrode plate to prevent oxidation, characterized in that: The following steps are involved: (1) Insert the green plate into the formation tank for the first charge; The first charge time is within 24 hours, and the charge amount is 7.5±0.1 times the capacity of the green plate; (2) After charging is completed, the plates are left in the formation tank for the first discharge and the second charge. The units of the discharge current and the charge current are both amperes. The values ​​of the discharge current and the charge current are calculated according to the following formula: Discharge current value = (L×H)×M×N×X, Where: L is the length of the plate in centimeters. H is the width of the plate in centimeters. M is the number of small plates contained in the large plate. N is the number of large negative plates in the formation tank; X represents the coefficient, and the value range of X is 0.01 to 0.02; Charging current value = Y × discharging current value; Where: Y represents the coefficient, and the value range of Y is 0.1~0.15; Among them, the large plate pieces are cut into small plate pieces; The first discharge time is 3-5 minutes, and the second charge time is 5 times the first discharge time; (3) discharging the electrode plate for a second time, charging it for a third time, and discharging it for a third time with the discharge current and charge current in step (2); The second discharge time is 60% ± 5% of the first discharge time; the third charge time is 60% ± 5% of the second charge time; the third discharge time is 30% ± 5% of the first discharge time; (4) After the plate is washed to neutrality in step (3), the positive plate is directly dried, and the negative plate is immersed in a xylitol aqueous solution, taken out and dried to obtain an oxidation-resistant externalized negative plate.

2. The processing method according to claim 1, characterized in that: In step (1), during the first charging process, the level of the formed liquid is higher than the upper edge of the green plate.

3. The processing method according to claim 1, characterized in that: In step (4), the mass percentage concentration of the xylitol aqueous solution is 5%-7%.

4. The processing method according to claim 1, characterized in that: In step (4), the negative electrode plate is immersed in the xylitol aqueous solution and allowed to stand for 10-15 minutes.

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