METHOD FOR PREPARING GRID ALLOY OF LEAD BATTERY

Abstract

A method for preparing a grid alloy of a lead battery, comprising the following steps: (1) preparing an aluminum-lanthanum-cerium rare earth mother alloy by using a molten salt electrolysis method; (2) melting the aluminum-lanthanum-cerium rare earth mother alloy with sodium and partial lead and uniformly stirring same to prepare an intermediate alloy; and (3) melting the intermediate alloy with calcium, tin and remaining lead and uniformly stirring same to form a grid alloy of a lead battery.

Claims

1. A method for preparing a grid alloy of a lead battery, wherein components of the grid alloy of the lead battery are: tin 1.0-2.0 wt %, calcium 0.05-0.10 wt %, lanthanum 0.02-0.05 wt %, cerium 0.02-0.05 wt %, sodium 0.02-0.05 wt %, and aluminum 0.01-0.04 wt % with the balance being lead; wherein the preparation method comprises the following steps: (1) preparing an aluminum-lanthanum-cerium rare earth mother alloy by using a molten salt electrolysis method; (2) melting the aluminum-lanthanum-cerium rare earth mother alloy with sodium and partial lead and uniformly stirring same to prepare an intermediate alloy; (3) melting the intermediate alloy with calcium, tin and remaining lead and uniformly stirring same to prepare the grid alloy of the lead battery.

2. The preparation method of claim 1, wherein a method for preparing the aluminum-lanthanum-cerium rare earth mother alloy by using the molten salt electrolysis method comprises the following steps: (a) adding a mixture of lanthanum oxide, cerium oxide and aluminum oxide into an electrolyte system, wherein a mass ratio of the mixture to the electrolyte system is 1:50-1:10; (b) carrying out molten salt electrolysis eutectoid reaction to obtain the aluminum-lanthanum-cerium rare earth mother alloy.

3. The preparation method of claim 1, wherein the intermediate alloy is prepared by using a vacuum melting method, which is: putting lead into a vacuum melting furnace, melting, and then heating to 950-1000 C., adding aluminum-lanthanum-cerium rare earth mother alloy and sodium with stirring, stirring for another 20-40 minutes and then cooling, and casting an ingot at the temperature of 550-650 C.

4. The preparation method of claim 2, wherein components of the electrolyte system are: lanthanum fluoride 30-40 wt %, cerium fluoride 30-40 wt %, lithium fluoride 10-20 wt %, and barium fluoride 10-20 wt %.

5. The preparation method of claim 2, wherein an amount of each component in the mixture of lanthanum oxide, cerium oxide and aluminum oxide is lanthanum oxide 10-40 wt %, cerium oxide 10-40 wt % and aluminum oxide 30-80 wt %.

6. The preparation method of claim 2, wherein an electrolytic bath used for molten salt electrolysis is a graphite crucible with a graphite sheet as an anode, a molybdenum rod as a cathode, and a molybdenum crucible as an alloy receiver; the molten salt electrolysis is performed at an anode current density of 1.0-1.5 A/cm.sup.2, a cathode current density of 15-20 A/cm.sup.2, and an electrolysis temperature of 850-950 C.

7. The preparation method of claim 1, wherein components of the aluminum-lanthanum-cerium rare earth mother alloy are: aluminum 10-50 wt %, lanthanum 25-50 wt %, and cerium 25-50 wt %.

8. The preparation method of claim 1, wherein components of the intermediate alloy are: aluminum 1-4 wt %, lanthanum 2-5 wt %, cerium 2-5 wt %, and sodium 2-5 wt % with the balance being lead.

9. The preparation method of claim 1, wherein step (3) comprises putting the lead into a lead melting furnace, melting, and then heating to 620-670 C., adding the intermediate alloy with stirring, and stirring for another 10-15 minutes for uniform mixing; adding calcium with stirring, and stirring for another 10-15 minutes after the calcium is melted; adding tin with stirring, stirring for another 10-15 minutes after the tin is melted, and then cooling, and casting an ingot at the temperature of 550-600 C.

10. The preparation method of claim 1, wherein the lead is electrolytic lead with lead content 99.994%.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0029] FIG. 1 is a flowchart of a method for preparing a grid alloy of a lead battery according to a specific embodiment of the present application.

[0030] FIG. 2 is a diagram showing results of metallographic examination of a grid alloy prepared in comparative example 1.

[0031] FIG. 3 is a diagram showing results of metallographic examination of a grid alloy prepared in comparative example 2.

[0032] FIG. 4 is a diagram showing results of metallographic examination of a grid alloy prepared in example 7.

[0033] FIG. 5 is a diagram showing results of metallographic examination of a grid which was prepared using the grid alloy prepared in the comparative example 1.

[0034] FIG. 6 is a diagram showing results of metallographic examination of a grid which was prepared using the grid alloy prepared in the comparative example 2.

[0035] FIG. 7 is a diagram showing results of metallographic examination of a grid which was prepared using the grid alloy prepared in the example 7.

[0036] FIG. 8 is a diagram showing results of battery cycle life detection in example 14.

DETAILED DESCRIPTION

[0037] The technical solutions of the present application are further described below through specific examples. Those who skilled in the art should understand that the examples described herein are merely used for a better understanding of the present application and should not be construed as specific limitations to the present application.

[0038] FIG. 1 is a flowchart of a method for preparing a grid alloy of a lead battery according to a specific embodiment of the present application. As shown in FIG. 1, an aluminum-lanthanum-cerium rare earth mother alloy was prepared, then an intermediate alloy was prepared by using the aluminum-lanthanum-cerium rare earth mother alloy, sodium and partial lead, and finally, the grid alloy of the lead battery was prepared by using the intermediate alloy, calcium, tin and remaining lead.

EXAMPLE 1

[0039] An aluminum-lanthanum-cerium rare earth mother alloy was prepared by using a molten salt electrolysis method.

[0040] The mass ratio of components in an electrolyte system was LaF.sub.3:CeF.sub.3:LiF:BaF.sub.2=40:40:10:10. The mass ratio of added raw materials was La.sub.2O.sub.3:CeO.sub.2:Al.sub.2O.sub.3=25:25:50. The molten salt electrolysis was carried out at the current strength of 2800 A, the anode current density of 1.0-1.2 A/cm.sup.2, the cathode current density of 15-18 A/cm.sup.2, and the electrolysis temperature of 880-910 C. The electrolyte mass in the electrolytic furnace was 100 kg. 5 kg raw materials were added, and 2.6 kg alloy was prepared. In the alloy, the content of lanthanum was 39.2%, and the content of cerium was 37.1%. The utilization rate of the metal lanthanum was 95.9%, and the utilization rate of the metal cerium was 95.1%. The components of the prepared aluminum-lanthanum-cerium rare earth mother alloy are shown in Table 1, where Fe, Si, C, Cu, Ag, Sb are impurities, which is the same in examples described below.

TABLE-US-00001 TABLE 1 Aluminum-lanthanum-cerium rare earth mother alloy component analysis results/wt % La Ce Al Fe Si C Cu Ag Sb 39.2 37.1 22.3 0.08 0.02 0.01 0.002 0.0004 0.001

EXAMPLE 2

[0041] An aluminum-lanthanum-cerium rare earth mother alloy was prepared by using the molten salt electrolysis method.

[0042] The mass ratio of components in an electrolyte system was LaF.sub.3:CeF.sub.3:LiF:BaF.sub.2=30:30:20:20. The mass ratio of added raw materials was La.sub.2O.sub.3:CeO.sub.2:Al.sub.2O.sub.3=40:30:30. The molten salt electrolysis was carried out at the current strength of 2700 A, the anode current density of 1.2-1.4 A/cm.sup.2, the cathode current density of 18-20 A/cm.sup.2, and the electrolysis temperature of 920-950 C. The electrolyte mass in the electrolytic furnace was 250 kg. 5 kg raw materials were added, and 3.2 kg alloy was prepared. In the alloy, the content of lanthanum was 49.8%, and the content of cerium was 36.2%. The utilization rate of the metal lanthanum was 92.2%, and the utilization rate of the metal cerium was 93.6%. The components of the prepared aluminum-lanthanum-cerium rare earth mother alloy are shown in Table 2.

TABLE-US-00002 TABLE 2 Aluminum-lanthanum-cerium rare earth mother alloy component analysis results/wt % La Ce Al Fe Si C Cu Ag Sb 49.8 36.2 12.5 0.06 0.02 0.02 0.001 0.0003 0.001

EXAMPLE 3

[0043] An aluminum-lanthanum-cerium rare earth mother alloy was prepared by using the molten salt electrolysis method.

[0044] The mass ratio of components in an electrolyte system was LaF.sub.3:CeF.sub.3:LiF:BaF.sub.2=40:40:10:10. The mass ratio of added raw materials was La.sub.2O.sub.3:CeO.sub.2:Al.sub.2O.sub.3=15:15:70. The molten salt electrolysis was carried out at the current strength of 2600 A, the anode current density of 1.3-1.5 A/cm.sup.2, the cathode current density of 17-20 A/cm.sup.2, and the electrolysis temperature of 850-880 C. The electrolyte mass in the electrolytic furnace was 50 kg. 5 kg raw materials were added, and 2.1 kg alloy was prepared. In the alloy, the content of lanthanum was 28.4%, and the content of cerium was 27.3%. The utilization rate of the metal lanthanum was 90.1%, and the utilization rate of the metal cerium was 92.5%. The components of the prepared aluminum-lanthanum-cerium rare earth mother alloy are shown in Table 3.

TABLE-US-00003 TABLE 3 Aluminum-lanthanum-cerium rare earth mother alloy component analysis results/wt % La Ce Al Fe Si C Cu Ag Sb 28.1 27.3 43.1 0.07 0.01 0.02 0.002 0.0005 0.001

EXAMPLE 4

[0045] An intermediate alloy was prepared by using the aluminum-lanthanum-cerium rare earth mother alloy prepared in Example 1.

[0046] 25 kg pure lead was put into a vacuum smelting furnace. The lead was melted and then heated to 980 C. 2.5 kg rare earth mother alloy prepared in Example 1 and 1.0 kg metal sodium were added with stirring, and stirred for another 30 minutes, and then cooled. After dregs were fished out, ingot casting was carried out at 600 C., to obtain 28.2 kg alloy. In the alloy, the content of lanthanum was 3.38%, the content of cerium was 3.29%, the content of aluminum was 1.76% and the content of sodium was 3.44%. The components of the prepared intermediate alloy are shown in Table 4.

TABLE-US-00004 TABLE 4 Intermediate alloy component analysis results/wt % La Ce Al Na Fe Si C 3.38 3.29 1.76 3.44 0.008 0.002 0.001 Cu Ag Bi Zn Sb Pb 0.0002 0.0003 0.003 0.0003 0.0008 Remainder

EXAMPLE 5

[0047] An intermediate alloy was prepared by using the aluminum-lanthanum-cerium rare earth mother alloy prepared in Example 2.

[0048] 25 kg pure lead was put into a vacuum smelting furnace. The lead was melted and then heated to 1000 C. 3.0 kg rare earth mother alloy prepared in Example 2 and 1.5 kg metal sodium were added with stirring, and stirred for 30 another minutes, and then cooled. After dregs were fished out, ingot casting was carried out at 600 C., to obtain 29.2 alloy. In the alloy, the content of lanthanum was 4.96%, the content of cerium was 3.68%, the content of aluminum was 1.23% and the content of sodium was 4.88%. The components of the prepared intermediate alloy are shown in Table 5.

TABLE-US-00005 TABLE 5 Intermediate alloy component analysis results/wt % La Ce Al Na Fe Si C 4.96 3.68 1.23 4.88 0.006 0.002 0.002 Cu Ag Bi Zn Sb Pb 0.0003 0.0004 0.002 0.0003 0.0007 Remainder

EXAMPLE 6

[0049] An intermediate alloy was prepared by using the aluminum-lanthanum-cerium rare earth mother alloy prepared in Example 3.

[0050] 20 kg pure lead was put into a vacuum smelting furnace. The lead was melted and then heated to 950 C. 2.0 kg rare earth mother alloy prepared in Example 3 and 0.5 kg metal sodium were added with stirring, and stirred for another 30 minutes, and then cooled. After dregs were fished out, ingot casting was carried out at 600 C., to obtain 22.3 kg alloy. In the alloy, the content of lanthanum was 2.42%, the content of cerium was 2.38%, the content of aluminum was 3.66% and the content of sodium was 2.12%. The components of the prepared intermediate alloy are shown in Table 6.

TABLE-US-00006 TABLE 6 Intermediate alloy component analysis results/wt % La Ce Al Na Fe Si C 2.42 2.38 3.66 2.12 0.007 0.001 0.002 Cu Ag Bi Zn Sb Pb 0.0004 0.0005 0.002 0.0004 0.0007 Remainder

EXAMPLE 7

[0051] A finished product (working alloy) was prepared by using the intermediate alloy prepared in Example 4.

[0052] 1000 kg lead was put into a lead melting furnace, melted by heating, and then heated to 630-660 C. 10 kg intermediate alloy prepared in Example 4 was added with stirring, and stirred for another 15 minutes for uniform mixing. 0.6 kg calcium was added with stirring. Stirring continued for 15 minutes after the calcium was melted. 20 kg tin was added with stirring. Stirring continued for 15 minutes after the tin was melted. The temperature was reduced. After dregs were fished out, ingot casting was carried out at the temperature of 550 C., and to obtain a working alloy. The components of the prepared working alloy are shown in Table 7.

TABLE-US-00007 TABLE 7 Working alloy component analysis results/wt % Sn Ca La Ce Al Na Bi Cu 1.92 0.055 0.032 0.032 0.015 0.033 0.005 0.001 As Ag Zn Ni Sb Fe Cd Pb 0.001 0.005 0.0005 0.0002 0.001 0.0005 0.0002 Remainder

EXAMPLE 8

[0053] A finished product (working alloy) was prepared by using the intermediate alloy prepared in Example 5.

[0054] 1000 kg lead was put into a lead melting furnace, melted by heating, and then heated to 650-670 C. 10 kg intermediate alloy prepared in Example 5 was added with stirring, and stirred for another 15 minutes for uniform mixing. 0.8 kg calcium was added with stirring. Stirring continued for 15 minutes after the calcium was melted. 16 kg tin was added with stirring. Stirring continued for 15 minutes after the tin was melted. The temperature was reduced. After dregs were fished out, ingot casting was carried out at the temperature of 550 C., to obtain a working alloy. The components of the prepared working alloy are shown in Table 8.

TABLE-US-00008 TABLE 8 Working alloy component analysis results/wt % Sn Ca La Ce Al Na Bi Cu 1.53 0.073 0.048 0.036 0.011 0.046 0.005 0.001 As Ag Zn Ni Sb Fe Cd Pb 0.001 0.005 0.0005 0.0002 0.001 0.0005 0.0002 Remainder

EXAMPLE 9

[0055] A finished product (working alloy) was prepared by using the intermediate alloy prepared in Example 6.

[0056] 1000 kg lead was put into a lead melting furnace, melted by heating, and then heated to 620-650 C. 10 kg intermediate alloy prepared in Example 6 was added with stirring, and stirred for another 15 minutes for uniform mixing. 1.0 kg calcium was added with stirring. Stirring continued for 15 minutes after the calcium was melted. 12 kg tin was added with stirring. Stirring continued for 15 minutes after the tin was melted. The temperature was reduced. After dregs were fished out, ingot casting was carried out at the temperature of 550 C., to obtain a working alloy. The components of the prepared working alloy are shown in Table 9.

TABLE-US-00009 TABLE 9 Working alloy component analysis results/wt % Sn Ca La Ce Al Na Bi Cu 1.13 0.092 0.022 0.021 0.036 0.021 0.005 0.001 As Ag Zn Ni Sb Fe Cd Pb 0.001 0.005 0.0005 0.0002 0.001 0.0005 0.0002 Remainder

COMPARATIVE EXAMPLE 1

[0057] Method for preparing a common lead-calcium-tin alloy

[0058] A certain amount of pure lead was put into a lead melting furnace. The lead was melted and then heated to 580-600 C. After dregs were fished out, the melted lead was stirred at a high speed. A calcium-aluminum mother alloy (Ca/Al: 75:25 in weight) whose weight was equivalent to 0.13% of the pure lead was added, and stirred for another 15 minutes. Pure tin whose weight was equivalent to 1.5% of the pure lead was added, and continuously stirred for 15 minutes. Then the temperature was reduced. After dregs were fished out, ingot casting was carried out at the temperature of 550 C., to obtain a lead-calcium-tin alloy. The alloy components are shown in Table 10.

TABLE-US-00010 TABLE 10 Common lead-calcium-tin alloy component analysis results/wt % Sn Ca Al Bi Cu As Ag Zn Ni Sb Fe Cd Pb 1.216 0.074 0.022 0.003 0.001 0.001 0.005 0.0005 0.0002 0.001 0.0005 0.0002 Remainder

COMPARATIVE EXAMPLE 2

[0059] Method for preparing a lead rare earth alloy by directly adding rare earth elements

[0060] A certain amount of pure lead was put into a lead melting furnace. The lead was melted and then heated to 880-900 C. After dregs were fished out, the melted lead was stirred at a high speed. Pure lanthanum whose weight was equivalent to 0.04% of the pure lead and pure cerium whose weight was equivalent to 0.04% of the pure lead were added, and stirred at a high speed for 10 minutes. Stirring continued and the temperature was reduced to 560-580 C. Metal sodium whose weight was equivalent to 0.06% of the pure lead was added, and stirred at a high speed for 10 minutes. A calcium-aluminum mother alloy (Ca/Al: 75:25 in weight) whose weight was equivalent to 0.13% of the pure lead was added and stirred for another 15 minutes. Pure tin whose weight was equivalent to 1.5% of the pure lead was added and stirred for another 15 minutes. Then the temperature was reduced. After dregs were fished out, ingot casting was carried out at the temperature of 550 C., to obtain a lead rare earth alloy. The alloy components are shown in Table 11.

TABLE-US-00011 TABLE 11 Component analysis results of the lead rare earth alloy prepared by directly adding rare earth elements/wt % Sn Ca La Ce Al Na Bi Cu 1.223 0.076 0.026 0.027 0.025 0.032 0.004 0.001 As Ag Zn Ni Sb Fe Cd Pb 0.001 0.005 0.0005 0.0002 0.001 0.0005 0.0002 Remainder

EXAMPLE 10

[0061] Metallographic Examination:

[0062] The lead alloy was made into a sample with the diameter of 10 mm and the length of 20 mm. The sample was ground by a metallographic grinder. In the grinding process, the rotation speed of the grinding disc was controlled to be 800 r/min, and water was used as a lubricating agent and cooling liquid. 300# and 600# metallographic abrasive papers were used for carrying out rough grinding, and then 1500# and 2000# abrasive papers were used for carrying out fine grinding. The ground sample was polished by using a polymer synthetic fabric. After polishing, the sample was washed with water for a secondary cleaning, corroded by using a mixed solution of analytically pure acetic acid and hydrogen peroxide (the volume ratio was 1:3), soaked and washed in absolute ethyl alcohol, and blown dry by using an electric blower. The texture structure of the surface of the alloy was observed under a metallographic microscope.

[0063] The alloys prepared in Comparative example 1, Comparative example 2 and Example 7 were detected. The detection results are respectively shown in FIGS. 2, 3 and 4. It can be seen that the common lead-calcium alloy (prepared in Comparative example 1) had coarse crystal grains of more than 200 m and obvious segregation; the common lead rare earth alloy (prepared in Comparative example 2) had slightly fine crystal grains but irregular crystal boundaries, and also had black speck-shaped or butterfly-shaped impurities or segregation points; the lead rare earth alloy prepared in Example 7 had finer crystal grains of about 10 regular grain boundaries and less segregation.

EXAMPLE 11

[0064] The grid alloys prepared in Comparative example 1, Comparative example 2 and Example 7 were respectively cast into grids. Metallographic structures of these grids were detected. The detection results are respectively shown in FIGS. 5, 6 and 7. It can be seen from metallography of the grids that the grid cast by the common lead-calcium-tin alloy (prepared in Comparative example 1) had large crystal grains, irregular crystal boundaries, and multiple intermetallic compounds were precipitated; the grid cast by the common lead rare earth alloy (prepared in Comparative example 2) had fine crystal grains but very uneven sizes, and irregular crystal boundaries, and a certain amount of intermetallic compounds were precipitated; the grid caste by the lead rare earth alloy prepared in Example 7 had fine and uniformly distributed crystal grains, regular grain boundaries and fewer impurities.

EXAMPLE 12

[0065] The alloys prepared in Example 7, Comparative example 1 and Comparative example 2 were respectively cast into grids. A constant current corrosion test was carried out by introducing 50 mA current into 1.28 g/mL sulfuric acid solution. In the test process, the corrosion area was 5 cm.sup.2, and the corrosion duration was 20 days. The weight loss data of the sample after corrosion was tested to calculate the average corrosion weight loss per day, so as to measure the corrosion resistance of the alloy sample. The lower the average corrosion weight loss per day is, the stronger the corrosion resistance of the alloy is. The results are shown in Table 12. It can be seen that the grid alloy prepared by the preparation method of the present application has better corrosion resistance.

TABLE-US-00012 TABLE 12 Corrosion resistance detection results Before After Weight Corrosion Alloy corrosion/g corrosion/g loss/mg speed mg/d Comparative 48.6565 48.0138 642.70 30.60 example 1 Comparative 48.0112 47.4646 546.60 26.03 example 2 Example 7 47.9411 47.6292 311.90 14.85

EXAMPLE 13

[0066] The alloys prepared in Example 7, Comparative example 1 and Comparative example 2 were respectively cast into grids. The grids were produced into a polar plate respectively, and a battery was assembled to perform a cycle test. A charge-discharge cycle with 100% depth of discharge (100% DoD) was performed. The battery was dissected after 200 cycles were completed. The size variation of the grid was measured to measure the creep resistance of the alloy. The smaller the size variation is, the stronger the creep resistance of the alloy is. The results are shown in Table 13. It can be seen that the grid alloy prepared by the preparation method of the present application has better creep resistance.

TABLE-US-00013 TABLE 13 Creep resistance detection results Initial Height after Height Height Alloy height/mm cycles/mm increase/mm change rate Comparative 136.12 137.58 1.46 1.07% example 1 Comparative 136.15 137.46 1.31 0.96% example 2 Example 7 136.13 136.76 0.63 0.46%

EXAMPLE 14

[0067] The alloys prepared in Example 7, Comparative example 1 and Comparative example 2 were respectively cast into grids. The grids were produced into a polar plate respectively, and a battery was assembled to perform a cycle test. A charge-discharge cycle with 100% DoD was performed. The test was terminated when the discharge capacity of the battery was lower than 96 minutes three successive times, and the battery was determined to be invalid. The number of cycles completed before the battery was invalid was counted and recorded as the cycle life of the battery. The results are shown in FIG. 8. The cycle life of the battery produced by the grid alloy (prepared in Example 7) by the preparation method of the present application reached 491 times, the cycle life of the battery produced by the common alloy prepared in Comparative example 1 was 292 times, and the cycle life of the battery produced by the common lead rare earth alloy prepared in Comparative example 2 was 368 times, which indicates that the cycle life of the battery can be greatly prolonged by the grid alloy prepared by the preparation method of the present application.