MXPA99011009A - Hydrogen storage alloy - Google Patents

Abstract

A hydrogen storage alloy of the AB5-type, where the A component includes La and/or Nd and at least 0.4 mole%Pr, as well as batteries including the alloy, are disclosed.

Description

ALLOY OF HYDROGEN STORAGE DESCRIPTION OF THE INVENTION The invention relates to hydrogen storage alloys for use in rechargeable batteries. A battery typically includes one or more galvanic cells (for example, cells that produce a direct current of electricity) in a finished package. In each cell, two electrodes are separated by an electrode insulator, but they are joined by a path that carries ions. . The path or path that carries electrons from the battery is external; the way proceeds, through a driver, through a device where the work is done. The ion carrier path of the battery is internal and proceeds via an electrolyte. The electrodes are usually composed of dissimilar metals. The electrode where the electrolyte is decomposed to the reception of electrons, is the positive electrode, also called the cathode. The electrode where the metal enters into solution, releasing electrons, is called the negative electrode, or anode. He REF .: 32163 electrolyte is generally composed mainly of a ionizable salt dissolved in a solvent. The batteries can be rechargeable; such batteries are called "storage" or "secondary" batteries. The storage batteries can be recharged by passing current through the cells in the opposite direction of the current flow discharge. The chemical conditions of the battery are restored, and the cells are ready to be discharged again. It is understood that the primary batteries, on the one hand, are discharged to exhaustion only once, and then discarded. An example of a rechargeable battery is a metal oxide-hydrogen storage battery. The positive electrode of this battery includes a metal oxide, such as nickel oxide; the negative electrode includes a hydrogen storage alloy, and the electrolyte includes an alkaline solution. An example of an electrode reaction in a nickel-hydrogen oxide storage battery is as follows: Positive electrode: Download - > NiOOH + H20 + e "< - Ni (OH) 2 + OH" (1) charge Negative electrode: Download - > M-H + OH "< - M + H20 + e" (2) Load In the reaction equation (2), M represents a hydrogen storage alloy. Hydrogen storage alloys are capable of absorbing electrochemically and discharging large quantities of hydrogen. One type of hydrogen storage alloy is type AB5, which has a crystalline structure of the CaCus type. Components A and B of the AB5 type alloy are present in a molar composition of about 1: 5. Component A is generally composed of an alloy of ceric metals (mischmetal) (a mixture of rare earth elements, in general cerium (Ce), lanthanum (La), neodymium (Nd) and praseodymium (Pr), as well as zirconium (Zr), and component B is generally composed of nickel (Ni), together with two or more elements selected from cobalt (Co), manganese (Mn), aluminum (Al), copper (Cu), iron (Fe), or germanium (Ge). The subscripts, which indicate% mol of the elements that make up the component A, generally have a sum of 1, while the subscripts of the elements that make up the component B have a sum of 4. 75 to 5.50. It is desirable that the metal oxide-hydrogen storage batteries have characteristics such as high energy density, relatively high load retentions, relatively long cycle lives, and good discharge capabilities over a wide range of temperatures. The reaction of hydrogen discharge at the negative electrode, however, tends to be retarded with the decrease in temperature; the discharge capacities can therefore deteriorate at low temperatures. The low temperature performance of batteries can be improved, but the improved performance at low temperature is often accompanied by the loss of other desirable properties such as high temperature performance, capacity (the ability to store hydrogen) or cycle life . In general, the invention features a hydrogen storage alloy with a relatively high content of praseodymium (Pr). The hydrogen storage alloy, preferred is type AB5; the component of this alloy includes at least 0.4 mol% of Pr. The alloy also includes lanthanum (La) and / or neodymium (Nd). The alloy can be used to make batteries with good low temperature discharge capabilities, good room temperature properties, good charge retention, and uniform discharge capabilities over a wide range of discharge speeds. The invention also features an alkaline storage battery that includes a positive electrode, a negative electrode that includes a hydrogen storage alloy having a relatively high Pr content and including La and / or Nd, and an alkaline electrolyte. Other characteristics and advantages of the invention will be apparent from the description of the preferred embodiments thereof, and from the claims.

Figure 1 is a sectional view of a cylindrical storage cell; Figure 2a is a perspective view of a rectangular storage cell; Figures 2b and 2c are sectional views of a rectangular storage cell; Figure 3 is a perspective view of the electrode assembly of a rectangular storage cell; and Figure 4 is a graph showing the capacity for various discharge rates for a hydrogen storage alloy. With reference to Figure 1, a cylindrical battery 10 includes a negative electrode 1, a positive electrode 2, and a separator 3. The electrodes and the separator are contained within a case or housing 4. The upper end of the case 4 is closed with a sealing plate 5 and an insulating annular gasket 6 which provide a gas-tight and fluid-tight seal. A positive guide 7 connects the positive electrode 2 to the sealing plate 5. The sealing plate 5 is provided with a safety valve 8 placed on the inner side of a positive terminal 9. The valve 8 is configured to act when the pressure internal battery exceeds a predetermined value. The main component of the negative electrode 1 is a hydrogen absorbing alloy of type AB5, which is formed by the fusion of the appropriate elements. The mixture of elements is melted in an order of induction under an argon atmosphere, then it is allowed to cool. The resulting alloy is pulverized by absorption and desorption of hydrogen, mechanical pulverization, jet mill, or other means known in the art to form a powder, which is screened to remove particles greater than 75 microns. The alloy can be used in a sprayed condition, as it is emptied. Alternatively, the alloy can be heat treated, and then pulverized. The heat treatment includes heating the alloy at 900 ° C to 1100 ° C for 1 to 12 hours, either under vacuum or under an argon atmosphere. The heat treatment helps to homogenize the elements. The negative electrode 1 may contain other ingredients as well. For example, the electrode may include a carbon of high surface area. The carbon catalyzes the conversion of 02, formed in the positive electrode, in H20, thus promoting the reduction of the pressure in the battery. The electrode may also include a binder such as polytetrafluoroethylene (PTFE), and thickeners, such as polyvinyl alcohol / sodium polyacrylate copolymer, and carboxymethylcellulose (CMC). The negative electrode 1 can be prepared as follows. The alloy is combined with the carbon, the binder, the thickeners, and water to form a paste. The paste is applied to a conductive core substrate, such as cold-rolled, nickel-plated, perforated, or expanded metal sheet. The material is then dried, rolled and die cut into pieces of the appropriate size. The positive electrode 2 can include any of a number of known materials in electrochemical techniques. For example, the positive electrode may include spherical nickel hydroxide, which may contain zinc and cobalt; cobalt monoxide; a binder, such as PTFE; thickeners such as CMC and sodium polyacrylate (SPA); and a paste stabilizer such as sodium borate. The positive electrode 2 can be prepared as follows. The ingredients are combined with water to produce a paste, which is then applied to a highly porous, synthesized, felt or foam substrate. The filled substrate is compacted, then pieces of appropriate size are cut from the substrate. A nickel tongue, which serves as a current collector, is then applied with ultrasonic welding. The separator 3 is a porous insulating film or a thin film; The film or sheet can be composed of a polyamide (such as nylon), polypropylene, polyethylene, polysulfone, or polyvinyl chloride (PVC). A preferred material is polypropylene. The separator is cut into pieces of a similar size to the electrodes, and is placed between the negative and positive electrodes to separate them electrically. The negative electrode 1, the positive electrode 2 and the separator 3 are wound or wound onto a Swiss roll and placed in a case 4 made of a metal such as nickel or nickel-plated steel, or a plastic material such as PVC, polypropylene, polysulfone, ABS, or polyamide. Case 4 is then filled with an electrolyte. The electrolyte can be any electrolyte known in the art. An example of an electrolyte is potassium hydroxide (KOH) with a concentration of 20 to 40% by weight, plus lithium hydroxide (LiOH) with a concentration of 0 to 10% by weight. The case 4 is then sealed with the sealing plate 5 and the insulating annular gasket 6. Examples of cylindrical batteries that can be prepared according to the present invention include batteries A, AA, AAA, 4 / 5A, 4 / 3A, sub-C and hemi-C. Alternatively, the battery can be rectangular in shape; an example of a rectangular battery is the prismatic cell described in U.S. Patent No. 4,977,043, which is incorporated by reference herein in its entirety. Reference is made to Figures 2a-2c, wherein a rectangular battery 11 includes a case 12, a lid body 13, a positive electrode terminal 14, a positive electrode 15, a separator 16 which surrounds the positive electrode 15, a negative U electrode 17, a negative electrode guide 18, a positive electrode guide 19, and a frame body or structure 20. Figure 3 shows an exploded view of the electrode assembly. As shown there, the positive electrodes 15 are sandwiched between the negative electrodes 17 in a U-shape. The lower part of the U includes a negative electrode guide 18. Negative and positive electrodes can be prepared as described above, or as described in U.S. Patent No. 4,977,043. An example of a rectangular battery that can be prepared according to the present invention is a battery used to power electric vehicles. Alternatively, a coil-type battery can be formed. To form this type of battery, the material forming the positive electrode is pressed to form "pellets." One or more of these pellets, surrounded by a separator, are placed inside a housing or housing. In the form of a powder, and an electrolyte are added to the case, the case is then sealed, other types of batteries known in the art can also be prepared.

EXAMPLES Example 1 _ An alloy having formula Lao.15Ceo.15Pro.7Ni3.7Coo.7Mno.1Alo.5 was prepared by melting lanthanum, cerium, praseodymium, nickel, cobalt, manganese and aluminum in the proportions required to obtain approximately 2 kg of the desired composition. The molten charge was charged into a magnesia crucible installed in an induction furnace. The atmosphere inside the furnace chamber was evacuated to obtain a vacuum state less than or equal to 0.02 torr. Immediately before the melting, the furnace chamber was filled with argon at a pressure of 780 to 790 torr, which was maintained during the "melting" operation, the molten charge was maintained at 1400 ° C for one minute, and then emptied in a copper block and allowed to cool to <50 ° C. The resulting alloy was pulverized by absorption and desorption of hydrogen The resulting powder was sieved to remove particles larger than 75 micrometers Test cells were prepared as follows. A pellet comprising 1 gram of nickel powder and 0.35 g of the alloy was compacted under a load of 3.5 tons in a 12.7 mm diameter die The compacted pellet was wrapped in cold-rolled steel sheet, nickel-plated, perforated, 60 micrometer thick, to which a nickel tongue was attached The wrapped pellet and a positive electrode, or counter electrode, of sintered Ni (OH) 2, was immersed in 150 cubic centimeters of electrolyte De-aerated aqueous KOH 5.5N + 2.0N NaOH 0.5N LiOH. The cells were conditioned at room temperature with six charge / discharge cycles consisting of a charge of 50 mA for 2.7 hours, followed by a discharge of 45 mA. The cells were discharged at -0.6V versus a reference electrode of Hg / HgO. The capacity was then determined at 25 ° C, 0 ° C, -10 ° C, and -20 ° C at discharge speeds of C / 2 (45 mA), C / 3 (30 mA), and c / s ( 20 mA) The results are presented in Table 1.

TABLE 1 Discharge capacities in mA * hr / g at a cut of -0.6V versus Hg / HgO As illustrated in Table 1, the cells showed high discharge capacities over a wide range of temperatures. The tested cells were then connected to the cell recycling equipment and loaded with 50 mA for 2.7 hours. The charge cycle was followed by a 10 minute rest cycle, without current flow. The cells were discharged at the speeds of C / 2, C73 and C / 5. Instead of measuring the discharge against a reference electrode, the discharge was terminated when the cell voltage reached 1.0 volts. The results are shown in Table 4, "which illustrates that the cells show relatively uniform discharge capacities in a high range of discharge velocities.The alloy described above showed a discharge capacity of 16 mA-hr / ga C / 2 compared to C / 5.

Example 2 An alloy having the formula La0.3Ceo was prepared. ? sPr0.55Ni3.7Coo.7Mno. ? Al0.5 • The test cells containing this alloy were prepared and tested as described above. A test cell that included this alloy had a discharge capacity of 273 mA "hr / g at a temperature of -20 ° C and at a discharge velocity of C / 3.

Example 3 An alloy having the formula La0 was prepared. ? sCe0. ? sPr0.63Nd0.07Zr0.00eNi3.7Co0.7Mn0.1AI0.5 • The test cells containing this alloy were prepared and tested as described above. A test cell including this alloy had a discharge capacity of 262 mA »hr / g at a temperature of -20 ° C and at a discharge velocity of C / 3.

Example 4 An alloy was prepared having the formula Lao.15Ceo.3Pro.55NÍ3.7Coo.7Mno.1Alo.5 • The test cells containing this alloy were prepared and tested as described above. A test cell including this alloy had a discharge capacity of 231 mA 'r / g at a temperature of -20 ° C and at a discharge velocity of C / 3.

Example 5 An alloy having the formula La0 was prepared. ? sPr0.85Ni3.7Coo.7Mno. ? Al0.5 • The test cells containing this alloy were prepared and tested as described above. A test cell that included this alloy had a discharge capacity of "245 mA" hr / g at a temperature of -20 ° C and at a discharge speed of C / 3. 6 An alloy was prepared having the formula Lao.3Pro.7Ni3.7Coo.7Mn0.?Al0.5 • The test cells containing this alloy were prepared and tested as described above. A test cell including this alloy had a discharge capacity of 263 mA * hr / g at a temperature of -20 ° C and at a discharge velocity of C / 3.

Example 7 An alloy having the formula La0.3Ce0.3P 0. < Ni3.7Coo.7Mno.1Alo.5 • The test cells containing this alloy were prepared and tested as described above. A test cell including this alloy had a discharge capacity of 203 mA "hr / g at a temperature of -20 ° C and at a discharge velocity of C / 3.

Example 8 An alloy was prepared having the formula Lao.?Ce0.?Pr0.BNi3.7C?o.7Mn0.1AI0.5 • The test cells containing this alloy were prepared and tested as described above. A test cell including this alloy had a discharge capacity of 258 mA * hr / g at a temperature of -20 ° C and at a discharge velocity of C / 3.

Example 9 An alloy having the formula La0.4? Ce0.03P 0.4Ndo.09 Í4 was prepared. osCoo. Mn0.44AI0.34, using the procedure described above.

Example 10 A 4 / 5A battery of the type shown in Figure 1 was prepared, using the procedure described above. The main component of the negative electrode 1 was a hydrogen storage alloy having the formula Lao.15Ceo.15Pro.7Ni3.7Coo.7Mno.1Alo.5- The alloy was pulverized by absorption and desorption of hydrogen, and then sieved. The electrode also included (relative to the amount of the hydrogen storage alloy, by weight): 0.7% carbon of high surface area; 2.0% PTFE; 0.29% -of copolymer of polyvinyl alcohol / sodium polyacrylate; and 0.12% CMC. The substrate used was cold rolled steel sheet, nickel plated, perforated. The main component of positive electrode 2 was nickel hydroxide, which included 5.0% zinc and 0.75% cobalt. The electrode also included (in relation to the amount of nickel hydroxide, by weight): 0.5% PTFE; 0.13% CMC; 0.18% of SPA; 5.0% cobalt oxide; and 0.1% sodium borate. The substrate used was a porous nickel material. The electrolyte included KOH 5.5N + NaOH 2. ON + LiOH 0.5N, and separator 3 was polypropylene.

Example 11 A 4 / 5A battery of the type shown in Figure 1 was prepared, using the general procedure described above. The main component of the negative electrode 1 was a hydrogen storage alloy having the formula ao.3 eo.15Pro.55Ni5.7Coo.7Mno.1Alo.5- The alloy was pulverized by absorption and desorption of hydrogen, and then sieved . The electrode also included (in relation to the amount of the hydrogen storage alloy, by weight): 0.7% carbon of high surface area; 2.0% PTFE; 0.29% polyvinyl alcohol / sodium polyacrylate copolymer; and 0.12% CMC. The substrate used was cold rolled steel sheet, nickel plated, perforated. The main component of positive electrode 2 was nickel hydroxide, which included 5.0% zinc and 0.75% cobalt. The electrode also included (in relation to the amount of nickel hydroxide, by weight): 0.5% PTFE; 0.13% CMC; 0.18% of SPA; 5.0% cobalt oxide; and 0.1% sodium borate. The substrate used was a porous nickel material. The electrolyte included KOH 5.5N + NaOH 2. ON + LiOH 0.5N, and separator 3 was polypropylene. Other embodiments are within the claims.

It is noted that, in relation to this date, the best method known by the applicant to carry out the aforementioned invention is the conventional one for the manufacture of the objects to which it relates.

Claims (35)

CLAIMS Having described the invention as above, the content is claimed as property - in the following claims:

1. A hydrogen storage alloy of type AB5, characterized in that component A comprises La and at least 0.4 mole% of Pr.

2. The hydrogen storage alloy according to claim 1, characterized in that the component B of the alloy comprises Mn.

3. The hydrogen storage alloy according to claim 1, characterized in that the component B of the alloy comprises 0.01 to 0.6 mol% of Al.

4. The hydrogen storage alloy according to claim 1, characterized in that the component A of the alloy further comprises 0.01 to 0.3 mol% of Nd.

5. The hydrogen storage alloy according to claim 1, characterized in that the component A of the alloy further comprises 0.001 to 0.1 mol% of Zr.

6. The hydrogen storage alloy according to claim 1, characterized in that the component B of the alloy comprises Cu.

7. The hydrogen storage alloy according to claim 1, characterized in that component B of the alloy comprises Fe.

8. A hydrogen storage alloy of the type AB5, characterized in that the component A of the alloy comprises Nd and at least 0.4 mol% of Pr.

9. The hydrogen storage alloy according to claim 8, characterized in that the component B of the alloy comprises Mn.

10. The hydrogen storage alloy according to claim 8, characterized in that the component B of the alloy comprises 0.1 to 0.6 mol% of Al.

11. The hydrogen storage alloy according to claim 8, characterized in that the component A of the alloy further comprises 0.01 to 0.5 mol% of La.

12. The hydrogen storage alloy according to claim 8, characterized in that the component A of the alloy further comprises 0.001 to 0.1 mol% of Zr.

13. The hydrogen storage alloy according to claim 8, characterized in that the component B of the alloy comprises Cu.

14. The hydrogen storage alloy according to claim 8, characterized in that component B of the alloy comprises Fe.

15. A hydrogen storage alloy of type AB5, characterized in the alloy because it comprises: 0.01 to 0.5 mol% of La; 0 to 0.4% mol of Ce; 0 to 0.3% mol of Nd; 0.4 to 1.0% mol of Pr; 1.0 to 5.0% mol of Ni; 0.1 to 1.0% mol of Co; 0.01 to 0.5% mol of Mn; and 0.01 to 0.6% mol of Al.

16. A hydrogen storage alloy of type AB5, characterized by the alloy because it comprises: 0.01 to 0.3 mol% of La; 0 to 0.2 mol% of Ce; 0 to 0.1% mol of Nd; 0.4 to 0.8% mol of Pr; 1.0 to 4.0% mol of Ni; 0.1 to 0.8% mol of Co; 0.01 to 0.2% mol 'of Mn; and 0.01 to 0.6% mol of Al.

17. A hydrogen storage alloy of type AB5-, the alloy. is characterized because it has the formula Lao.i5Ce0.i5 o.7NÍ3.7C? O.7Mn0.? Alo.5.

18. A hydrogen storage alloy of type AB5, the alloy is characterized because it has the formula La0.3Ceo.i5P 0.55NÍ3.7Co0.7Mn0.1AI0.5 -

19. A hydrogen storage alloy of type AB5, the alloy is characterized because it has the formula Lao.1sCeo.15Ndo.07Pro.63Zro.ooeNi3.7Coo.7Mno.1Al0.5 •

20. An alkaline storage battery, characterized in that it comprises a positive electrode; a negative electrode comprising a hydrogen storage alloy of the type AB5, wherein the component A of the alloy comprises La and at least 0.4 mole% of Pr; and an alkaline electrolyte. twenty-one'.

The battery according to claim 20, characterized in that the component B of the hydrogen storage alloy comprises Mn.

22. The battery according to claim 20, characterized in that the component B of the hydrogen storage alloy comprises 0.1 to 0.6 mol% of Al.

23. The battery according to claim 20, characterized in that the component A of the hydrogen storage alloy further comprises 0.01 to 0.3 mol% of Nd.

24. The battery according to claim 20, characterized in that the component B of the hydrogen storage alloy comprises Cu.

25. The battery according to claim 20, characterized in that component B of the hydrogen storage alloy comprises Fe.

26. The battery according to claim 20, characterized in that the positive electrode comprises a metal oxide.

27. The battery according to claim 20, characterized in that the positive electrode comprises a nickel oxide.

28. An alkaline storage battery, characterized in that it comprises a positive electrode; a negative electrode comprising a hydrogen storage alloy of the type AB5, wherein the component A of the alloy comprises Nd and at least 0.4 mol% of Pr; and an alkaline electrolyte.

29. The battery according to claim 28, characterized in that the component ^ B of the hydrogen storage alloy comprises Mn.

30. The battery according to claim 28, characterized in that the component B of the hydrogen storage alloy comprises 0.1 to 0.6 mol% of Al.

31. The battery according to claim 28, characterized in that the component B of the hydrogen storage alloy further comprises 0.01 to 0.5 mol% of La.

32. The battery according to claim 28, characterized in that the component B of the hydrogen storage alloy comprises Cu.

33. The battery according to claim 28, characterized in that component B of the hydrogen storage alloy comprises Fe.

34. The battery according to claim 28, characterized in that the positive electrode comprises a metal oxide.

35. The battery according to claim 28, characterized in that the positive electrode comprises a nickel oxide.