Rare earth hydrogen storage alloy and method for producing the same

Abstract

The application discloses a rare earth hydrogen storage alloy and a preparation method thereof. The rare earth hydrogen storage alloy has a composition shown in formula (I): RE x R y Ni d‑a M a (I); wherein RE is selected from one or more rare earth elements except Y, Sm and Gd, R is selected from one or more of Y, Sm, Gd and Mg, and M is selected from one or more of Mn, Al, Fe, Co, Si, V, Cu, Sn, Ti, Zr, Cr, Zn and Mo; wherein 0.3<=x<=3, 2.5<=y<=5, 0.3<=a<=5 and 3<=d / (x+y)<=5.5; x, y, a and d-a respectively represent the mole fraction of each element; and the sphericity of the rare earth hydrogen storage alloy is greater than or equal to 90%. The rare earth hydrogen storage alloy has good cycle stability.

Description

Technical Field

[0001] This invention relates to a rare earth hydrogen storage alloy and its preparation method. Background Technology

[0002] Rare earth hydrogen storage materials are green functional materials that can reversibly store and release large amounts of hydrogen, playing an important role in the utilization of hydrogen energy. They can absorb and release large amounts of hydrogen under specific temperatures and pressures, and the hydrogen absorption and release reactions are fast and have excellent reversibility, making them important energy conversion materials.

[0003] CN116479287A discloses an A5B 19 A type La-Y-Ni hydrogen storage alloy, the chemical composition of which is La 5-x Y x Ni 19-y R y Wherein, 2.78≤x≤3.34, 0≤y≤1.5, and R is one or more of Mn, Al, Co, Zr, Cr, Sc, Ti, V, Nb, and Mo. The alloy is prepared as follows: the raw materials are melted and cast to obtain an alloy ingot; the alloy ingot is heat-treated to obtain a hydrogen storage alloy ingot. The hydrogen storage alloy ingot is crushed and ball-milled to obtain alloy powder. This hydrogen storage alloy is an irregularly shaped powder.

[0004] CN116065055A discloses a yttrium-nickel based hydrogen storage alloy with the chemical composition RE. x Y y Ni e Mn a Fe b Si c M d RE is selected from one or more of La, Ce, Pr, Nd, Sm, and Gd, and M is selected from one or more of Al, Co, Cu, Zn, and B. This hydrogen storage alloy exhibits low sphericity and poor cycle stability. Summary of the Invention

[0005] In view of this, one object of the present invention is to provide a rare earth hydrogen storage alloy with high sphericity and good cycle stability. Furthermore, the rare earth hydrogen storage alloy has a high hydrogen absorption capacity and a moderate plateau voltage. Even further, the rare earth hydrogen storage alloy has a high discharge capacity and a low activation cycle count. Another object of the present invention is to provide a method for preparing a rare earth hydrogen storage alloy, which can improve the sphericity of the rare earth hydrogen storage alloy.

[0006] The above objectives are achieved through the following technical solutions.

[0007] On the one hand, the present invention provides a rare earth hydrogen storage alloy having the composition shown in formula (I):

[0008] RE x R y Ni d-a M a (I);

[0009] Among them, RE is selected from one or more rare earth elements other than Y, Sm, and Gd, R is selected from one or more of Y, Sm, Gd, and Mg, and M is selected from one or more of Mn, Al, Fe, Co, Si, V, Cu, Sn, Ti, Zr, Cr, Zn, and Mo.

[0010] Where 0.3≤x≤3, 2.5≤y≤5, 0.3≤a≤5, 3≤d / (x+y)≤5.5; x, y, a, and da represent the molar fractions of each element;

[0011] The sphericity of the rare earth hydrogen storage alloy is ≥90%.

[0012] In the rare earth hydrogen storage alloy of the present invention, preferably, 14 ≤ da ≤ 34.

[0013] According to the rare earth hydrogen storage alloy of the present invention, preferably, RE must contain La, and the content of La is 0.2 to 2.5 molar parts.

[0014] According to the rare earth hydrogen storage alloy of the present invention, preferably, the RE also contains one or more of Pr, Ce, and Nd, and the content of elements other than La in the RE is 0.05 to 1 molar.

[0015] In the rare earth hydrogen storage alloy of the present invention, preferably, R must contain Y, and the content of Y is 2 to 4.5 molar parts.

[0016] In the rare earth hydrogen storage alloy of the present invention, preferably, M must contain Mn, and the content of Mn is 0.8 to 3 molar parts.

[0017] According to the rare earth hydrogen storage alloy of the present invention, preferably, M also contains one or more of Al, Fe, Co, Si, and V, and the content of elements other than Mn in M ​​is 0.05 to 2 moles.

[0018] According to the rare earth hydrogen storage alloy of the present invention, preferably, the rare earth hydrogen storage alloy has one of the following compositions:

[0019] La2Y4Ni 20.8 Mn 1.2 Al 0.8 ;

[0020] La 1.5 Pr 0.5 Y4Ni 20.8 Mn 1.2 Al0.8 ;

[0021] La 1.8 Ce 0.2 Y4Ni 20.8 Mn 1.2 Al 0.8 ;

[0022] La2Y4Ni 20.8 Mn2;

[0023] La 1.8 Ce 0.2 SmY3Ni 16.6 MnAl 0.4 ;

[0024] La 0.8 Mg 0.2 Y3Ni 18 Mn 1.2 Fe 0.8 ;

[0025] La 1.5 Nd 0.5 Y4Ni 19.8 MnCo 0.2 ;

[0026] La 1.5 Y 3.5 GdNi 30 Mn 1.2 Al 0.8 Co;

[0027] La2Mg 0.2 Y 3.8 Ni 21.2 MnSi 0.6 ;

[0028] La 1.8 Sm 0.6 Y 3.6 Ni 20.2 Mn 0.8 ;

[0029] La 1.3 Ce 0.5 Sm 0.4 Y 3.8 Ni 20 Mn 1.3 Co 0.7 ;

[0030] La 1.5 Pr 0.4 Mg 0.2 Y 3.9 Ni 22 MnAl 0.5 Fe0.5 ;

[0031] La 1.9 Gd 0.2 Y 3.9 Ni 21 Mn 1.6 V 0.2 .

[0032] Furthermore, the present invention provides a method for preparing the above-mentioned rare earth hydrogen storage alloy, comprising the following steps:

[0033] A superheated melt at 373–587 K, formed according to the composition of the rare earth hydrogen storage alloy, is injected into an atomizing nozzle with a diameter of 2–6 mm through a guide tube with a diameter of 6–18 mm. The superheated melt flows out of the atomizing nozzle and encounters an inert gas flow in the atomizing device, where it is atomized into droplets. The droplets solidify to obtain alloy powder. The pressure of the inert gas is 0.2–0.7 MPa higher than the pressure inside the atomizing device.

[0034] The alloy powder was heat-treated to obtain a rare earth hydrogen storage alloy.

[0035] According to the preparation method of the present invention, preferably, the inert gas is Ar gas, and the inert gas is used as a cooling medium to cool the droplets in the atomizing device; the heat treatment temperature is 800-1100℃, and the heat treatment time is 12-24h.

[0036] The rare-earth hydrogen storage alloy of the present invention has high sphericity and high capacity retention. This rare-earth hydrogen storage alloy exhibits high hydrogen storage capacity, moderate plateau voltage, high discharge capacity, and fewer activation cycles. Attached Figure Description

[0037] Figure 1 The image shows a SEM image of the rare earth hydrogen storage alloy obtained in Example 1. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0039] Rare Earth Hydrogen Storage Alloys

[0040] This invention provides a rare earth hydrogen storage alloy having the composition shown in formula (I): RE x R y Ni d-a M a (I).

[0041] The rare-earth hydrogen storage alloy of the present invention has a high sphericity. The sphericity is ≥90%; preferably, the sphericity is ≥95%. This can reduce stress concentration in the alloy during hydrogen absorption and desorption, and improve its resistance to pulverization and cycle stability.

[0042] The particle size range of the rare earth hydrogen storage alloy of the present invention is 25–80 micrometers; preferably 38–75 micrometers. The rare earth hydrogen storage alloy of the present invention has a uniform particle size distribution, which further improves the alloy's cycle stability, electrochemical performance, and hydrogen storage capacity.

[0043] RE is selected from one or more rare earth elements other than Y, Sm, and Gd. Preferably, RE is selected from one or more of La, Pr, Ce, and Nd. More preferably, RE must contain La. In some embodiments, RE is La.

[0044] x represents the molar number of RE. 0.3 ≤ x ≤ 3; preferably, 0.8 ≤ x ≤ 2.2. In some embodiments, 1.5 ≤ x ≤ 1.6. In other embodiments, 1.8 ≤ x ≤ 2.

[0045] The content of La can be 0.2 to 2.5 moles; preferably 0.8 to 2 moles. In some embodiments, the content of La is 1.3 to 1.5 moles.

[0046] RE may also contain one or more of Pr, Ce, and Nd. The content of elements other than La in RE is 0.05 to 1 mole. In some embodiments, it is 0.2 to 0.5 moles. In other embodiments, it is 0.3 to 0.4 moles.

[0047] R is selected from one or more of Y, Sm, Gd, and Mg. Preferably, R must contain Y. In some embodiments, R is Y. In other embodiments, R is Y and an element selected from Sm, Gd, and Mg.

[0048] y represents the molar number of R. 2.5 ≤ y ≤ 5; preferably, 3 ≤ y ≤ 4.5. In some embodiments, 4 ≤ y ≤ 4.2.

[0049] The content of Y can be 2 to 4.5 moles; preferably 3 to 4 moles. In some embodiments, the content of Y is 3.5 to 3.8 moles.

[0050] R may contain other elements besides Y. The content of other elements in R besides Y may be 0.05 to 2 parts by weight; preferably 0.1 to 1.5 parts by weight; more preferably 0.2 to 1 part by weight.

[0051] da represents the molar number of Ni. 14 ≤ da ≤ 34; preferably, 18 ≤ da ≤ 30. In some embodiments, 19 ≤ da ≤ 21.

[0052] M is selected from one or more of Mn, Al, Fe, Co, Si, V, Cu, Sn, Ti, Zr, Cr, Zn, and Mo. Preferably, M is selected from one or more of Mn, Al, Fe, Co, Si, and V. More preferably, M must contain Mn. In some embodiments, M is Mn. In other embodiments, M is Mn and one or more elements selected from Al, Fe, Co, Si, and V.

[0053] 'a' represents the molar number of M. 0.3 ≤ a ≤ 5; preferably, 0.8 ≤ a ≤ 3. In some embodiments, 1.4 ≤ a ≤ 2.

[0054] The Mn content can be 0.8 to 3 moles; preferably 1 to 2 moles. In some embodiments, the Mn content is 1.2 to 1.3 moles.

[0055] The content of elements other than Mn in M ​​can be 0.05 to 2 parts by weight. In some embodiments, it is 0.2 to 1.8 molar parts. In other embodiments, it is 0.7 to 0.8 molar parts.

[0056] 3 ≤ d / (x+y) ≤ 5.5. In some implementations, 3.5 ≤ d / (x+y) ≤ 3.8.

[0057] In some embodiments, the rare earth hydrogen storage alloy has one of the following compositions:

[0058] La2Y4Ni 20.8 Mn 1.2 Al 0.8 ;

[0059] La 1.5 Pr 0.5 Y4Ni 20.8 Mn 1.2 Al 0.8 ;

[0060] La 1.8 Ce 0.2 Y4Ni 20.8 Mn 1.2 Al 0.8 ;

[0061] La2Y4Ni 20.8 Mn2;

[0062] La 1.8 Ce 0.2 SmY3Ni 16.6 MnAl 0.4 ;

[0063] La 0.8 Mg 0.2 Y3Ni18 Mn 1.2 Fe 0.8 ;

[0064] La 1.5 Nd 0.5 Y4Ni 19.8 MnCo 0.2 ;

[0065] La 1.5 Y 3.5 GdNi 30 Mn 1.2 Al 0.8 Co;

[0066] La2Mg 0.2 Y 3.8 Ni 21.2 MnSi 0.6 ;

[0067] La 1.8 Sm 0.6 Y 3.6 Ni 20.2 Mn 0.8 ;

[0068] La 1.3 Ce 0.5 Sm 0.4 Y 3.8 Ni 20 Mn 1.3 Co 0.7 ;

[0069] La 1.5 Pr 0.4 Mg 0.2 Y 3.9 Ni 22 MnAl 0.5 Fe 0.5 ;

[0070] La 1.9 Gd 0.2 Y 3.9 Ni 21 Mn 1.6 V 0.2 .

[0071] Controlling the elemental composition and content of rare earth hydrogen storage alloys within the above-mentioned range helps to improve the sphericity and uniformity of particle size distribution, enhance cycle stability, and improve platform performance.

[0072] <Preparation Methods of Rare Earth Hydrogen Storage Alloys>

[0073] The method for preparing the rare earth hydrogen storage alloy of the present invention includes the following steps: (1) gas atomization quenching step; (2) heat treatment step. In some embodiments, a melting and forming step is also included.

[0074] Melting and forming step

[0075] The raw materials provided according to the composition of the rare earth hydrogen storage alloy are smelted to obtain an alloy liquid. The alloy liquid is then poured into a mold to obtain the master alloy.

[0076] Before using rare earth metal raw materials, the oxide layer on their surface can be removed.

[0077] The raw materials can be placed in an Al2O3 crucible. Preferably, the melting point of the raw materials gradually increases from the bottom to the top of the Al2O3 crucible.

[0078] Melting can be carried out in a medium-frequency vacuum melting furnace.

[0079] The smelting can be carried out under the protection of an inert gas. Examples of inert gases include, but are not limited to, nitrogen, helium, neon, argon, krypton, and xenon. According to one embodiment of the invention, the inert gas is argon.

[0080] The melting temperature can be 1200-1500℃; preferably 1300-1450℃; more preferably 1350-1400℃.

[0081] The smelting pressure can be 0.001 to 0.09 MPa; preferably 0.01 to 0.07 MPa; more preferably 0.03 to 0.05 MPa.

[0082] Gas atomization cold extraction step

[0083] Superheated melt is injected into an atomizing nozzle through a conduit; the superheated melt flows out of the atomizing nozzle and encounters an inert gas stream within the atomizing device, where it is atomized into droplets. The droplets solidify to obtain alloy powder. The inert gas serves as the cooling medium. During their flight within the atomizing device, the droplets rapidly solidify due to surface tension, forming alloy powder.

[0084] The alloy powder of the present invention is spherical. The particle size of the alloy powder ranges from 30 to 75 micrometers; preferably from 38 to 75 micrometers.

[0085] The superheating temperature of the superheated melt is 373–587 K; preferably 400–550 K; more preferably 450–500 K. This helps to form alloy powder with high sphericity and good uniformity.

[0086] The master alloy can be melted to form a superheated melt. The melting temperature can be 1200–1500℃; preferably 1300–1400℃.

[0087] Examples of inert gases include, but are not limited to, nitrogen, helium, neon, argon, krypton, and xenon. In some embodiments, argon is used as the inert gas. This helps to form alloy powders with high sphericity and good uniformity.

[0088] The diameter of the guide tube is 6–18 mm; preferably 10–15 mm; more preferably 12–13 mm. This helps to form alloy powder with high sphericity and good uniformity.

[0089] The diameter of the atomizing nozzle is 2–6 mm; preferably 3–5 mm; more preferably 4–4.5 mm. This helps to form alloy powder with high sphericity and good uniformity.

[0090] The inert gas pressure is 0.2–0.7 MPa higher than the pressure inside the atomizing device; preferably, the inert gas pressure is 0.4–0.6 MPa higher than the pressure inside the atomizing device. This helps to form alloy powder with high sphericity and good uniformity.

[0091] Heat treatment step

[0092] The alloy powder was heat-treated to obtain a rare earth hydrogen storage alloy.

[0093] The heat treatment temperature can be 800–1100℃; preferably 850–900℃.

[0094] The heat treatment time can be 12 to 24 hours; preferably 15 to 20 hours.

[0095] Heat treatment can be performed under an inert gas atmosphere. Examples of inert gases include, but are not limited to, nitrogen, helium, neon, argon, krypton, and xenon. In some embodiments, the inert gas is argon.

[0096] The heat treatment can be carried out at a relative vacuum of -0.01 to -0.06 MPa; preferably, the heat treatment is carried out at a relative vacuum of -0.03 to -0.04 MPa.

[0097] Heat treatment can be carried out in a quartz tube.

[0098] The heating rate from the initial temperature to 500°C can be 3–7°C / min; preferably 4–6°C / min.

[0099] The heating rate from 500℃ to 800℃ can be 6 to 10℃ / min; preferably 7 to 9℃ / min.

[0100] The heating rate from 800℃ to 1000℃ can be 3 to 7℃ / min; preferably 4 to 6℃ / min.

[0101] When the temperature is above 1000℃, the heating rate can be 0.3~3℃ / min; preferably 0.5~2℃ / min.

[0102] Such heat treatment conditions help maintain the morphology of the alloy powder.

[0103] The testing method is described below:

[0104] Sphericity: The morphology of rare earth hydrogen storage alloys was tested by scanning electron microscopy to understand the morphological characteristics of rare earth hydrogen storage alloys at different magnifications and positions; the total number of particles and the number of complete particles in the scanning electron microscopy image were quickly divided using Image-Pro-Plus software, and the equivalent diameter of the perimeter and area of ​​the complete particles was calculated. The sphericity of each complete particle was obtained according to formula (1), and the average value was calculated to obtain the sphericity of the rare earth hydrogen storage alloy.

[0105] Q = d1 / d a (1)

[0106] Where Q represents sphericity; d1 represents the perimeter-equivalent diameter of the particle; d a This represents the area equivalent diameter of the particle.

[0107] Activation cycles, maximum discharge capacity, and cycle stability: Rare earth hydrogen storage alloy with a particle size of 200-270 mesh was mixed uniformly with carbonyl nickel at a mass ratio of 1:4, and then an electrode sheet with a diameter of 15 mm was formed under a pressure of 20 MPa. The electrode sheet was placed between two sheets of foamed nickel, and then pressed under a pressure of 10 MPa. Nickel strips were spot-welded as tabs to obtain the working electrode.

[0108] An open-type three-electrode system was adopted, with the negative electrode as the working electrode, the positive electrode as a sintered Ni(OH)2 / NiOOH electrode with excess capacity, the reference electrode as Hg / HgO, and the electrolyte as a 6 mol / L KOH solution. The assembled battery was left to stand for 24 hours before testing.

[0109] The electrochemical performance of the alloy electrode was determined using a LAND battery tester with a constant current method at an ambient temperature of 303 K.

[0110] Activation and discharge capacity test: charging current density is 60 mA·g –1 The charging time is 7.5 hours, and the discharge current density is 60 mA·g. –1 The discharge cutoff potential is 0.6V (relative to the reference electrode), and the charging and discharging interval is 10min.

[0111] Cyclic stability test: charging current density of 300 mA·g –1 The charging time is 1.2 hours, and the discharge current density is 300 mA·g. –1The discharge cutoff potential is 0.6V (relative to the reference electrode), and the charge / discharge interval is 10 minutes. Under these parameters, 500 cycles are performed. The ratio of the discharge capacity at the 500th cycle to the maximum discharge capacity during the cycle is the capacity retention rate after 500 cycles.

[0112] Maximum hydrogen absorption capacity and plateau pressure: The rare earth hydrogen storage alloy was heated to 573 K, evacuated, and held for 30 min to obtain the activated hydrogen storage alloy. The activated hydrogen storage alloy was subjected to a Sieverts apparatus at a temperature of 318 K and a pressure of 4 MPa to obtain the PCT curve, thereby obtaining the maximum hydrogen absorption capacity and plateau pressure.

[0113] Examples 1-13

[0114] The raw materials were prepared according to the composition of the rare earth hydrogen storage alloy shown in Table 1. After removing the oxide layer from the surface of the rare earth metal, the raw materials were placed in an Al2O3 crucible. The melting point of the raw materials gradually increased from the bottom to the top of the Al2O3 crucible. The Al2O3 crucible containing the raw materials was melted in a medium-frequency vacuum melting furnace under Ar gas protection at a pressure of 0.05 MPa and a temperature of 1350 °C to obtain a liquid alloy. The liquid alloy was then cast into a mold to obtain the master alloy.

[0115] The master alloy is melted at 1300°C to form a superheated melt at 473K. The superheated melt can be placed in a tundish to maintain its temperature.

[0116] Superheated melt is injected through a 12mm diameter boron nitride guide tube into a 4.2mm diameter atomizing nozzle. Ar gas is used as the cooling medium, and the pressure of the introduced Ar gas is 0.5MPa higher than the pressure inside the atomizing tower. The superheated melt flows out of the atomizing nozzle and encounters the Ar gas flow inside the atomizing tower, where it is atomized into droplets. During their flight, the droplets are subjected to surface tension and solidify inside the atomizing tower to form alloy powder. The resulting alloy powder is spherical, with a particle size ranging from 38 to 75μm.

[0117] Alloy powder was placed in a quartz tube, which was then evacuated to 0.01–0.001 Pa. Ar gas was then introduced to achieve a relative vacuum of -0.03–-0.04 MPa within the quartz tube. The tube was then heat-treated at 875 °C for 16 h to obtain the rare-earth hydrogen storage alloy. The heating rates from the initial temperature to the heat treatment temperature were as follows: 5 °C / min from the initial temperature to 500 °C; 8 °C / min from 500 °C to 800 °C; and 5 °C / min from 800 °C to 900 °C. The particle size range of the obtained rare-earth hydrogen storage alloy was 38–75 micrometers.

[0118] Table 1

[0119]

[0120] Note: Under the hydrogen absorption / desorption plateau pressure, X / Y indicates that the rare earth hydrogen storage alloy has two hydrogen absorption / desorption plateau pressures, namely X and Y.

[0121] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A rare earth hydrogen storage alloy, characterized in that, The rare earth hydrogen storage alloy has one of the following compositions: La2Y4Ni 20.8 Mn 1.2 Al 0.8 ; The 1.5 Pr 0.5 Y4Ni 20.8 Mn 1.2 Al 0.8 ; La 1.8 Ce 0.2 Y4Ni 20.8 Mn 1.2 Al 0.8 ; La2Y4Ni 20.8 Mn2; Let 1.8 Ce 0.2 SmY3Ni 16.6 MnAl 0.4 ; La 0.8 Mg 0.2 Y3Ni 18 Mn 1.2 Fe 0.8 ; The 1.5 Nd 0.5 Y4Ni 19.8 MnCo 0.2 ; La 1.5 Y 3.5 GdNi 30 Mn 1.2 Al 0.8 Co; La2Mg 0.2 Yes 3.8 In 21.2 MnSi 0.6 ; La 1.8 Sm 0.6 Y 3.6 Ni 20.2 Mn 0.8 ; La 1.3 Ce 0.5 Sm 0.4 Y 3.8 Ni 20 Mn 1.3 What 0.7 ; The 1.5 Pr 0.4 Mg 0.2 AND 3.9 Neither 22 MnAl 0.5 Faith 0.5 ; The 1.9 Gd 0.2 AND 3.9 Neither 21 Mn 1.6 V 0.2 ; The sphericity of the rare earth hydrogen storage alloy is ≥90%.

2. The method for preparing rare earth hydrogen storage alloy according to claim 1, characterized in that, Includes the following steps: A superheated melt at 373–587 K, formed according to the composition of the rare earth hydrogen storage alloy, is injected into an atomizing nozzle with a diameter of 2–6 mm through a guide tube with a diameter of 6–18 mm. The superheated melt flows out of the atomizing nozzle and encounters an inert gas flow in the atomizing device, where it is atomized into droplets. The droplets solidify to obtain alloy powder. The pressure of the inert gas is 0.2–0.7 MPa higher than the pressure inside the atomizing device. The alloy powder was heat-treated to obtain a rare earth hydrogen storage alloy.

3. The preparation method according to claim 2, characterized in that, The inert gas is Ar, which is used as a cooling medium to cool the droplets in the atomizing device; the heat treatment temperature is 800-1100℃, and the heat treatment time is 12-24h.

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