AB5 TYPE-BASED HYDROGEN STORAGE ALLOYS, METHODS OF PREPARATION AND USES THEREOF

Abstract

This invention relates to metal hydrides for storing hydrogen, in particular AB5 based metal hydrides, methods of production and uses thereof.

Claims

1-14. (canceled)

15. A hydrogen storage alloy having an AB5 type crystal structure, its A site contains La, Ce and MI elements, and its B site contains Ni, Co and Fe elements, represented by the general Formula (I):
La.sub.xCe.sub.yMI(.sub.1-x-y)Ni.sub.aCo.sub.bFe.sub.cM.sub.d (I) in which x, y, a, b, c and d are molar ratios, where M1 is at least one element selected from Y, Ti, and Zr and M is selected from Cu and Mn; 0.15 ?x?0.95;0.05?y?0.85; 0?(1-x-y)?0.1; 3.8?a?4.2; 0.1?b?1.2; 0.01?c?0.3; 0?d?0.1; 4.8?(a+b+c+d) ?5.15.

16. The hydrogen storage alloy according to claim 15, wherein 0.15?x?0.45 and 0.55?y?0.85.

17. The hydrogen storage alloy according to claim 15, wherein 0.55?x?0.95 and 0.05?y?0.45.

18. The hydrogen storage alloy according to claim 15, wherein 0.9 ? x+y ? 1.

19. The hydrogen storage alloy according to claim 15 that is selected from the group consisting of: La.sub.0.6Ce.sub.0.3Ni.sub.4.2C0.sub.0.3Fe.sub.0.4Mn.sub.0.1 (Ia); La.sub.0.3Ce.sub.0.65Ti.sub.0.05Ni.sub.3.8C0.sub.0.2Fe.sub.1.0 (Ib); La.sub.0.15Ce.sub.0.85 Ni.sub.3.8Co.sub.0.95Fe.sub.0.05 (Ic); La.sub.0.45Ce.sub.0.45Ti.sub.0.05Zr.sub.0.05Ni.sub.4.2Co.sub.0.4Fe.sub.0.3Mn.sub.0.05 (Id); La.sub.0.6Ce.sub.0.39Y.sub.0.1Ni.sub.4.2Co.sub.0.1Fe.sub.0.3Cu.sub.0.05Mn.sub.0.05 (Ie); and La.sub.0.9Ce.sub.0.05Ti.sub.0.05Ni.sub.4.2Co.sub.0.5Fe.sub.0.3Cu.sub.0.1 (If).

20. The hydrogen storage alloy according to claim 15, wherein the hydrogen storage alloy has at 25? C. a hydrogen absorption plateau between 5-150 bar and a desorption plateau between 3-100 bar.

21. The hydrogen storage alloy according to claim 15, wherein the hydrogen storage alloy has at 25? C. a hydrogen storage capacity of about 1.4 to about 1.55 wt %.

22. A method for the preparation of hydrogen storage alloy having an AB5 type crystal structure rapid melt solidification by spinning roller quenching, wherein said method comprises the steps of: providing a melt of all the metal elements in a furnace under a controlled inert atmosphere at a pressure from about 30 KPa to about 70 KPa; casting the melt within said furnace onto a spinning roller rolling at a speed from about 1.5 to about 9 m/s where the melt rapidly solidifies and breaks into flakes when entering a cooling unit; leaving the flakes to further cool down to a temperature below 50? C.; filling the furnace with air and collecting the obtained flakes.

23. The method according to claim 22, wherein the spinning roller is rolling at a constant speed from about 1.5 to about 9 m/s.

24. The method according to claim 22, wherein the obtained alloy is subjected to a further temperature treatment at a temperature between about 850 and 1,150? C. for about 0.5 to about 72 h.

25. An alloy obtainable by a method according to claim 22.

26. A powder of an alloy according to claim 15, wherein the particle size of the alloy is from about 0.5 mm to about 3 mm.

27. A method of storing hydrogen comprising contacting a hydrogen storage alloy according to claim 15 or a powder thereof with hydrogen.

28. A hydrogen storage system comprising an alloy according to claim 15 or a powder thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention will now be described with reference to the accompanying drawings, which by way of example illustrate embodiments of the present invention and in which:

[0026] FIG. 1 represents pressure-composition-temperature (PCT) isotherms of a metal hydride. A: schematic graphical representations of typical metal hydrides useful for hydrogen storage (https://www.ctcms.nist.gov/hydrogen_storage/research_pct.html); B: pcT curve of the material described in CN102828069; C: pcT curve of the material described in CN106854715.

[0027] FIG. 2 represents pressure-composition-temperature (PCT) isotherms of a metal hydride according to the invention. A: as described in Example 2; B: as described in Example 2.

[0028] FIG. 3 represents pressure-composition-temperature (PCT) isotherms of a metal hydride according to the invention compared to low-pressure AB5 alloys used in Ni-MH batteries as described in Example 3 at 30? C. (A&B) and 40? C. (C&D). A: Alloy similar to example 1 of U.S. Pat. No. 5,817,222 (La.sub.0.25Ce.sub.0.5Pr.sub.0.05Nd.sub.0.2Ni.sub.3.39Al.sub.0.19Co.sub.0.92 Mn.sub.0.48Fe.sub.0.02); B: and an alloy of the invention with a similar La content (0.25) (La.sub.0.25Ce.sub.0.7Ti.sub.0.05Ni.sub.4.0Co.sub.0.8Fe.sub.0.2); C: an alloy with a similar composition of Example 2 of JP 2001200324 (La0.8Ce0.12Pr0.04Nd0.04Ni4.15 Co0.4Mn0.35A10.3Fe 0.02Mg.sub.0.3) and D: an alloy of the invention with a similar La content (0.8) (La0.8Ce0.18Zr0.2Ni4.0Co0.8Fe0.1Cu0.1).

[0029] FIG. 4 is a schematic representation of a method of preparation of an alloy of the invention by rapid melt solidification by spinning roller quenching.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0030] According to a particular aspect, is provided a hydrogen storage alloy having an AB5 type crystal structure of Formula (I) in which b, c, d, Ml and M are as described above and wherein 0.15?x ?0.45 and 0.55?y?0.85 (Alloy (Ia)).

[0031] According to another particular aspect, is provided a hydrogen storage alloy having an AB5 type crystal structure of Formula (I) in which b, c, d, M1 and M are as described above and wherein 0.55?x?0.95 and 0.05?y? 0.45 (Alloy (Ib)).

[0032] According to a particular aspect, is provided a hydrogen storage alloy having an AB5 type crystal structure of Formula (I), wherein 0.9?x+y?1.

[0033] According to a particular aspect, is provided a hydrogen storage alloy according to the invention selected from the following group:

[0034] La.sub.0.6Ce.sub.0.3Ni.sub.4.2C0.sub.0.3Fe.sub.0.4Mn.sub.0.1 (Ia);

[0035] La.sub.0.3Ce.sub.0.65Ti.sub.0.05Ni.sub.3.8C0.sub.0.2Fe.sub.1.0 (Ib);

[0036] La.sub.0.15Ce.sub.0.85 Ni.sub.3.8Co.sub.0.95Fe.sub.0.05 (Ic);

[0037] La.sub.0.45Ce.sub.0.45Ti.sub.0.05Zr.sub.0.05Ni.sub.4.2Co.sub.0.4Fe.sub.0.3Mn.sub.0.05 (Id);

[0038] La.sub.0.6Ce.sub.0.39Y.sub.0.1Ni.sub.4.2Co.sub.0.1Fe.sub.0.3Cu.sub.0.05Mn.sub.0.05 (Ie); and

[0039] La.sub.0.9Ce.sub.0.05Ti.sub.0.05Ni.sub.4.2Co.sub.0.5Fe.sub.0.3Cu.sub.0.1 (If).

[0040] In the present invention, the hydrogen storage alloy has at 25? C. a hydrogen absorption plateau between 5-150 bar and a desorption plateau between 3-100 bar.

[0041] In the present invention, the hydrogen storage alloy has at 25? C. a hydrogen storage capacity of about 1.4 to about 1.55 wt % (typically from about 1.45 to 1.50 wt %).

[0042] A hydrogen storage according to the invention can be prepared by typical methods used for AB5 alloys such as described in CN1602366.

[0043] Typically, for batches up to 300 kg, raw materials of each required metal elements are placed in a water-cooled copper crucible in an Arc melting furnace and the furnace is put under vacuum (e.g. 5*10.sup.?3 Pa (PABS)) and then filled with a controlled atmosphere (e.g. Ar, >99.99%) under a pressure from about 30 KPa to about 70 KPa (e.g. 50 kPa (PABS)). The raw materials are melted and kept at a melting temperature for about 5 to 10 min and then the melted mixture is let solidified. The solidified alloy (ingot) is turned upside down and melted again and the operation is repeated few times (e.g. 2 to 6 times, such as 3 times) in order to achieve an homogeneous composition of the resulting alloy. Once the last cycle is over and the temperature of the solidified alloy is below 50? C., the furnace is put in communication with air and the ingot alloy is collected.

[0044] For batches from 3 to about 1'000 kg, a method for the preparation of hydrogen storage alloy having an AB5 type crystal structure by rapid melt solidification by spinning roller quenching as described herein is advantageously used. In particular, compared with Arc-melting processes, the alloy prepared by this method has a more homogenous composition, stable crystal structure, less phases other than AB5 structure and lower crystal strain (thus with a smaller hysteresis and more flat plateau pressure). The alloy does need to undergo heat-treatment process before usage, while maintain a long cycle life. This method is also suitable for large scale production and remarkably reduces production cost.

[0045] According to a particular embodiment, the metal elements are melted in a furnace initially purged and put under vacuum (e.g. 5*10.sup.31 3 Pa (PABS)) and then filled with a controlled inert atmosphere (e.g. Argon or He>99.99%)) at a pressure from about 30 KPa to about 70 KPa (e.g. 50 kPa (PABS)).

[0046] According to a further particular embodiment, the metal elements are melted in a Al.sub.2O.sub.3-based crucible placed in the furnace.

[0047] According to a further particular embodiment, after all the metals are melted, the temperature is reduced to a temperature between about 1'350 and 1'450? C. and hold for about 5 to 10 min.

[0048] Referring to FIG. 3, the metal mixture is melted in a crucible 1 (e.g. heated by an induction coil 2) placed in the furnace in said controlled atmosphere and then casted onto a spinning roller 3 (e.g. copper roller) rolling at a speed where the melt rapidly solidifies and breaks into flakes 4 when entering into a cooling unit (e.g. water-cooled collector).

[0049] According to a further particular embodiment, the melted mixture is casted onto a spinning roller (e.g. copper roller) rolling at a constant speed from about 1.5 to about 9 m/s where the melt rapidly solidifies and breaks into flakes. The thickness of the flakes will depend on the roller speed, the lower the speed, the thicker the flakes. According to a particular aspect, the thickness of the flakes typically ranges from 0.1-0.6 mm.

[0050] According to a further particular embodiment, the flakes are left to cool down in the furnace at a temperature in a water-cooled chamber.

[0051] The alloy of the invention could be used directly from the obtained flakes or can undergo a heat-treatment under the melting temperature of the alloy, when needed. The heat treatment is applied to further reduce the hysteresis and improve the cycle performance. Typically, a heat treatment is carried out in a furnace under vacuum (e.g. 9*10.sup.?2 Pa (PABS)), wherein the temperature is raised up to about 200? C. and hold to this temperature for about 20 min. Before further increasing the temperature of the furnace, it is filled with an inert atmosphere (e.g. pure Argon (>99.99%)) at a pressure from about 30 KPa to about 70 KPa (e.g. to the pressure of 50 KPa (PABS)). The temperature of the furnace is then increased to a temperature between about 850 and 1150?? C. which is hold for about 0.5 to about 72 h. The temperature-treated alloy is then cooled down at a rate of about 5 to about 20 K/min. Once the temperature of the alloy is below 60? C., the furnace is put in communication with air and the alloy is collected.

[0052] According to a further embodiment, is provided a method for the preparation of hydrogen storage alloy having an AB5 type crystal structure by rapid melt solidification by spinning roller quenching, wherein said method further comprises a heat treatment step.

[0053] The alloy according to the invention (heat-treated or not) can be used in the form of a powder. In particular, the obtained alloys are then crunched into a powder by mechanical or jet milling under the inert gas (e.g. N.sub.2 or Ar, Ar preferred). Typically, the particle size of the alloy could be from about 0.5 mm to about 3 mm depending on the hydrogen storage system it will be used for.

[0054] The alloy powder can be then stored as a powder under vacuum or inert gas (e.g. N.sub.2 or Ar, Ar preferred).

[0055] Alloys powder can be then used in hydrogen storage system as described in Bellosta von Colbe et al., 2019, supra.

[0056] Examples illustrating the invention will be described hereinafter in a more detailed manner and by reference to the embodiments represented in the Figures.

EXAMPLES

Example 1: Preparation of Alloys According to the Invention

Example 1a): Preparation with Arc Melting Furnace

[0057] An alloy of the invention, in particular of formula La.sub.0.6Ce.sub.0.3Ni.sub.4.2Co.sub.0.3Fe.sub.0.4Mn.sub.0.1 (Ia) was prepared.

[0058] The required amounts of the metals according to the formula were prepared for a total weight of 1 kg and placed in a water-cooled Cu crucible in an Arc melting furnace. The furnace was evacuated until the vacuum reached 5*10.sup.?3 Pa (PABS). Then, the furnace was filled with pure Argon (>99.99%) to a pressure of 50 KPa (PABS). The power was then increased until the raw materials started to melt. All the metals were melted and the power was held for 5 min. The melting was then stopped, waiting until the solidification of the alloy. The alloy was turned upside down, melted again, repeating this step 3 times in order to make the composition of the alloy more homogeneous. It was then waited until the temperature of the flake dropped below 50? C. Finally, the furnace was refilled with air and the alloy was taken out as an ingot.

[0059] After the melting, the as-prepared alloy was placed in the heat-treatment furnace. The furnace was evacuated until the vacuum reached 9*10.sup.?2 Pa (PABS). The temperature was then increased to 200? C. and held for 30 min. The furnace was then filled with pure Argon (>99.99%) to a pressure of 50 KPa (PABS). The temperature was then increased to 800? C. and held for 36 hours. The ally was then cooled down at a speed of 5 K/min., waiting until the temperature of the alloy dropped below 60? C. Finally, the furnace was refilled with air to atmosphere pressure and the alloy taken out of the furnace.

Example 1b: Preparation with Induction Melting Furnace

[0060] An alloy of the invention, in particular of formula La.sub.0.3Ce.sub.0.65Ti.sub.0.05Ni.sub.3.8Co.sub.0.2Fe.sub.1.0 (Ib) was prepared.

[0061] The required amount of the metals was weighted according to the formula Ib in a total weight of 750 kg and placed in a Al.sub.2O.sub.3-based crucible in an industrial induction melting furnace. The furnace was evacuated until the vacuum reached 5*10.sup.?3 Pa (PABS), then filled with Helium (>99.99%) to the pressure of 50 KPa (PABS). The metals were heated up to 1450? C. and been melt. After all metals are melted, the temperature was reduced to 1350? C. and hold for 10 min. The melt was cast onto a spinning Cu roller, the speed of which was set to be 5 m/s, the thickness of the flake is around 0.1 mm. The solidified flake will be led to a water-cooled chamber for further cool down. The furnace was refilled with air and the flake was taken out when the temperature of the flake drop below 50? C. The alloy could be used without further treatment.

Example 1c: Hydrogen Storage Performance of the as-prepared Alloys

[0062] Further alloys of the invention provided as illustrative examples are provided in Table 1 below together with their Hydrogen storage performances.

TABLE-US-00001 TABLE 1 Hydrogen Storage A Side (molar ratio) B Side (molar ratio) Pressure La Ce Y Ti Zr Ni Co Fe Cu Mn AB (atm) Ic 0.15 0.85 0 0 0 3.8 0.95 0.05 0 0 4.8 54 Id 0.45 0.45 0 0.05 0.05 4.2 0.4 0.3 0 0.05 5 10.5 Ie 0.6 0.39 0.1 0 0 4.2 0.1 0.3 0.05 0.05 5 5.6 If 0.9 0.05 0 0.05 0 4.2 0.5 0.3 0.1 0 5.1 2.5

Example 2: Hydrogen Storage Capacity of Alloys of the Invention

[0063] The H.sub.2 storage performance of the alloy prepared under Example 1 has been tested as follows. 3g of alloy ingot/flake was broken into powder (size<100mesh) and loaded into a stainless cylindrical sample chamber. The alloy was charged with constant 5 MPa of hydrogen pressure for 2 hours. After that the sample was evacuated for 30 min. The charging-evacuation step was repeated at least 3 times, in order to fully activate the alloy.

[0064] A fully-automatic, and computer-controlled volumetric apparatus (known as Sievert's apparatus, or PCT apparatus) will be used to measure the amount of hydrogen absorbed by the alloy at 25? C. in water bath.

[0065] As can be seen under FIG. 2, the alloys of the invention have a much higher and wider desorption plateau than conventional AB5 alloys, in particular those used for NiMH batteries at room temperature. The H.sub.2 charging pressure is also advantageously higher. Similar comparison has been carried out at higher temperatures, namely 30? C. and 40? C. between the alloy prepared under Example 1 and AB5 alloys used for NiMH batteries described in U.S. Pat. No. 5,817,222 (FIGS. 3A & B) and JP 2001200324 (FIGS. 3C & D).

[0066] As can be seen on FIG. 3, comparing an alloy similar to example of U.S. Pat. No. 5,817,222 (La0.25 Ce.sub.0.5Pr.sub.0.05Nd.sub.0.2Ni.sub.3.39Al.sub.0.19Co.sub.0.92Mn.sub.0.48Fe.sub.0.02) (A) and an alloy of the invention with a similar La content (0.25) (La.sub.0.25Ce.sub.0.7Ti.sub.0.05Ni.sub.4.0Co.sub.0.8Fe.sub.0.2) (B), the alloy plateau pressure of the alloy of the invention is usually above 1 atm with a typical pressure above 2atm, while the hydrogen pressure storage of the comparative alloys is below 0.3 atm. This is also confirmed when comparing an alloy with a similar composition of Example 2 of JP 2001200324 (La.sub.0.8Ce.sub.0.12Pr.sub.0.04Nd.sub.0.04Ni.sub.4.15Co.sub.0.4Mn.sub.0.35Al.sub.0.3Fe.sub.0.02Mg.sub.0.3) (C) and an alloy of the invention with a similar La content (0.8) (La.sub.0.8Ce.sub.0.18Zr.sub.0.2Ni.sub.4.0Co.sub.0.&Fe.sub.0.1Cu.sub.0.1) (D).

[0067] Therefore, those data support that the AB5 type alloys according to the invention present an improved performance at high H.sub.2 pressure than the known alloys and have reduced production costs due to the absence of Pr and Nd.