La-y-ni-based hydrogen storage alloy and method for producing the same

Abstract

The application belongs to the technical field of hydrogen storage materials, and relates to a La-Y-Ni series hydrogen storage alloy and a preparation method thereof, and a preparation method of a hydrogen storage alloy matrix, which comprises the following steps: (1) taking La, Ce, Y, Ni, Mn and Al raw materials according to a stoichiometric ratio to perform vacuum induction smelting, and after casting and cooling, a master alloy is obtained; (2) after the master alloy is ground into master alloy powder, the master alloy powder is ball milled with Mg2Ni powder under a protective gas; and (3) after the composite alloy powder is subjected to vacuum annealing treatment, the composite alloy powder is cooled in a furnace. The Ce element partially replaces the La, optimizes crystal defects and improves corrosion resistance; the in-situ generated Mg-containing nanophase and the Ce element synergistically act, significantly optimize the hydrogen storage capacity and cycle stability of the alloy, and greatly improve the electrochemical performance of the hydrogen storage alloy.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen storage materials technology, and relates to a La-Y-Ni hydrogen storage alloy and its preparation method. Background Technology

[0002] Hydrogen, with its high energy density, abundant sources, and zero-pollution combustion products, is considered an ideal energy carrier. Efficient, stable, and safe hydrogen storage materials and the hydrogen storage systems built upon them are crucial for hydrogen energy applications. Among numerous alternative hydrogen storage materials, hydrogen storage alloys, with their high hydrogen storage density, mild hydrogen absorption and desorption conditions, and good reversibility, have become one of the most practically valuable choices.

[0003] Current commercial and research hotspots for hydrogen storage alloys each have their own technical shortcomings: AB5-type rare-earth hydrogen storage alloys, already commercially available as nickel-metal hydride battery anodes, are easy to activate and have good high-current discharge capabilities, but their hydrogen storage capacity is difficult to further improve; Ti and Zr-based AB2-type Laves phase alloys have high discharge capacity, but suffer from activation difficulties and unsatisfactory kinetic performance; magnesium-based hydrogen storage alloys have significantly higher capacity than other types of alloys, but their operating temperature is relatively high and their hydrogen absorption and desorption rates are slow. In contrast, rare-earth-based superlattice hydrogen storage alloys, due to the presence of [AB5] and [A2B4] substructures stacked in different proportions in their crystal structure, combine the advantages of easy activation of AB5-type alloys and high capacity of AB2-type alloys. Their intrinsic hydrogen storage capacity can reach over 1.80 wt.%, significantly higher than commercially available AB5-type alloys. Moreover, their crystal structure is variable and highly tunable, possessing not only rich electrochemical hydrogen storage characteristics but also promising applications in solid-state hydrogen storage devices, making them a research focus in the field of hydrogen storage materials.

[0004] Typical rare-earth superlattice hydrogen storage alloy systems include La-Y-Ni and La-Mg-Ni systems. Among these, La-Y-Ni-based superlattice hydrogen storage alloys without Mg composition have become a research hotspot due to their excellent electrochemical performance, but their cycle stability still falls short of the stringent requirements of the energy market for high-performance nickel-metal hydride batteries. After Ce partially replaces La, due to Ce… 4+ / Ce 3+The redox stability of the redox couple can suppress oxidation corrosion on the alloy surface during charge and discharge, reducing the loss of active materials. Meanwhile, Ce's atomic radius (0.182 nm) is close to that of La (0.187 nm), meaning that substitution will not significantly damage the superlattice structure of the alloy. The slight decrease in discharge capacity can be compensated for by adding Mg, achieving synergistic optimization of capacity and cycle life. However, the addition of Mg in existing technologies still faces a core bottleneck. When directly involved in high-temperature melting, Mg's low melting point and high-temperature volatility can lead to uncontrolled composition and potential safety risks due to melt splashing, limiting its effective application in La-Y-Ni alloys. Therefore, developing a preparation technology that avoids the volatilization problem of Mg during high-temperature melting and simultaneously achieves synergistic doping of Mg and Ce is of great significance for overcoming the performance bottleneck of La-Y-Ni-based hydrogen storage alloys, promoting the development of nickel-metal hydride batteries towards high capacity and long lifespan, and supporting the large-scale application of the hydrogen energy industry. Summary of the Invention

[0005] The main objective of this invention is to overcome the shortcomings of existing La-Y-Ni-based hydrogen storage alloys, such as insufficient cycle stability, easy volatilization of Mg during high-temperature melting leading to uncontrolled alloy composition, and the safety hazard of dust explosion caused by directly introducing Mg powder during ball milling. This invention provides a Mg and Ce co-doped La-Y-Ni hydrogen storage alloy with excellent electrochemical performance and a safe and reliable preparation method with precise composition control. This allows the alloy to significantly improve cycle stability while maintaining high discharge capacity, meeting the stringent requirements for hydrogen storage materials in the industrial production of nickel-metal hydride batteries.

[0006] To achieve the above objectives, the specific technical solution is as follows: This invention provides a method for preparing a La-Y-Ni based hydrogen storage alloy, wherein the chemical formula of the hydrogen storage alloy matrix is ​​La. 1-x-y Ce x Y y Ni 3.25 Mn 0.15 Al 0.1 , 0.05≤x≤0.20, 0.40≤y≤0.80; the preparation method includes the following steps: (1) Weigh La, Ce, Y, Ni, Mn and Al raw materials according to stoichiometric ratio, perform vacuum induction melting, cast and cool to obtain master alloy; (2) After grinding the master alloy into master alloy powder, it is ball-milled with Mg2Ni powder under a protective gas to obtain composite alloy powder; (3) The composite alloy powder is subjected to vacuum annealing and then cooled in the furnace.

[0007] The hydrogen storage alloy preparation method provided by this invention adopts a three-step method of "vacuum induction melting - high-energy ball milling - vacuum annealing". First, a Ce-containing master alloy is prepared by vacuum induction melting to achieve uniform Ce doping. Then, the master alloy powder is mixed with Mg2Ni powder and mechanically alloyed by high-energy ball milling, so that Mg element reacts with the matrix in situ to generate one or more Mg-containing intermetallic compound nanophases. The Mg-containing nanophases preferentially precipitate at the matrix phase interface and grain boundary, and are nanoscale. Finally, the alloy structure is optimized by vacuum annealing.

[0008] This invention introduces Mg as the magnesium source using Mg₂Ni, avoiding the volatilization risk associated with direct Mg melting. Mechanical alloying is achieved through high-energy ball milling and annealing, which, together with Ce, enhances the alloy's electrochemical performance. Ce partially replaces La to optimize crystal defects and corrosion resistance. The two elements synergistically improve the alloy's capacity, cycle stability, and hydrogen absorption / desorption kinetics, making it suitable as a negative electrode active material for nickel-metal hydride batteries. Furthermore, the preparation process of this invention is safe and reliable with minimal compositional deviation. The resulting hydrogen storage alloy can be used as a negative electrode active material for nickel-metal hydride batteries, suitable for high-capacity, long-cycle-life power batteries, energy storage batteries, and portable electronic devices, demonstrating promising prospects for industrial application.

[0009] Furthermore, in step (1), the vacuum of the vacuum induction melting is ≤5×10⁻⁶. -3 Pa, maintain pressure of 0.10~0.15 MPa with protective gas, temperature of 1450~1600 ℃, and heat preservation time of 10~20 min.

[0010] The present invention employs the above-mentioned vacuum induction melting conditions, which is beneficial for completely eliminating air and impurity gases in the furnace, avoiding oxidation reactions during the raw material melting process, and the stable protective gas pressure can prevent molten splashing. The appropriate melting temperature and holding time can fully melt and uniformly mix the rare earth metals and transition metals, ensuring that Ce element achieves atomic-level uniform doping in the master alloy, while promoting the formation of a complete crystal nucleus structure in the alloy, laying the foundation for the subsequent construction of superlattice structures.

[0011] Further, in step (1), the purity of the La, Ce, Y, Ni, Mn and Al raw materials is ≥99.0%; preferably, the La and Ce raw materials are cleaned and degreased with anhydrous ethanol and dried; the La and Ce raw materials are stored in an oil-sealed container.

[0012] Furthermore, in step (1), the La, Ce, and Y raw materials are in excess by 4 wt.%, and the Al and Mn raw materials are in excess by 5 wt.%, in order to compensate for the element loss during the smelting process.

[0013] Further, in step (2), the ball-to-material ratio during ball milling is 40:1, the rotation speed is 300~500 r / min, and the ball milling time is 30~40 h; preferably, the ball milling procedure is: pause and cool down for 0.5-1 h every 1 h of ball milling, and clean the powder on the tank wall under an inert atmosphere every 5-10 h of ball milling.

[0014] The ball milling process conditions described above are advantageous for refining the master alloy powder through high-energy mechanical force and for fully combining the Mg2Ni powder with the matrix powder. The intermittent ball milling and cooling process can avoid powder agglomeration, oxidation, and abnormal grain growth caused by excessive temperature during ball milling. At the same time, cleaning the powder on the tank wall can ensure the uniformity of ball milling, ultimately providing conditions for high-energy ball milling to induce mechanical alloying and generate Mg-containing intermetallic compound nanophases.

[0015] Further, in step (2), the atomic ratio of the Mg2Ni powder to the master alloy powder is (0.1~0.2):1; preferably, the particle size of the master alloy powder is ≤200 mesh, and the particle size of the Mg2Ni powder is ≤200 mesh; more preferably, the purity of the Mg2Ni powder is ≥99.90%.

[0016] The above-mentioned addition range of the present invention can ensure the effective introduction of Mg element and its synergistic effect with Ce element, and avoid the alloy lattice distortion caused by excessive Mg2Ni or insufficient Mg2Ni, which would result in insignificant performance improvement.

[0017] Furthermore, in step (2), the loading process of the Mg2Ni powder and the master alloy powder is carried out in a glove box, and a protective gas is introduced after vacuuming.

[0018] Furthermore, in step (3), the vacuum annealing is performed with a vacuum level of ≤5×10⁻⁶. -3 Pa, the pressure is maintained at 0.08~0.12 MPa by purging with protective gas, the annealing temperature is 820~900 ℃, and the holding time is 5~7 h; preferably, the holding time is 820 ℃ for 7 h, 850 ℃ for 6 h, or 900 ℃ for 5 h.

[0019] The vacuum annealing process conditions described above are beneficial for eliminating lattice distortion and internal stress caused by high-energy ball milling, repairing crystal defects, and promoting the orderly stacking of [A2B4] and [AB5] substructures to form a complete superlattice structure. The appropriate annealing temperature and holding time can promote the full progress of the mechanical alloying reaction, stably generate Mg-containing intermetallic compound nanophases, and make the phase preferentially precipitate at the phase interface and grain boundary without abnormal growth. At the same time, it further improves the compatibility of Ce with the matrix and strengthens the synergistic effect of Ce and Mg-containing nanophases.

[0020] Furthermore, in step (3), the heating rate of the vacuum annealing is 4~6 ℃ / min.

[0021] The above-mentioned heating rate is beneficial to ensure uniform heating of the alloy powder, avoid abnormal local grain growth and powder sintering and agglomeration caused by excessively rapid heating, and gradually release the internal stress generated by ball milling, allowing the crystal structure to be reconstructed in an orderly manner, ensuring the uniformity and stability of the superlattice structure, and ultimately improving the electrochemical performance and cycle life of the hydrogen storage alloy.

[0022] Furthermore, the protective gas in steps (1) to (3) is an inert gas, preferably argon; more preferably argon with a purity ≥ 99.999%.

[0023] The present invention also provides a La-Y-Ni hydrogen storage alloy, which is prepared by the above-described method for preparing La-Y-Ni hydrogen storage alloy.

[0024] The electrochemical performance of the La-Y-Ni hydrogen storage alloy of this invention is significantly improved: the discharge capacity reaches 350~380 mAh / g, and the capacity retention rate is ≥78% after 500 charge-discharge cycles. Compared with La-Y-Ni-based alloys without Mg and Ce doping, the discharge capacity is increased by 20%~24.6%, and the cycle stability is improved by 18%~18.6%. The alloy has excellent activation performance; at 25℃ and a discharge current of 300 mA / g, the initial discharge capacity can reach more than 90% of the maximum discharge capacity. As a negative electrode active material for nickel-metal hydride batteries, it is suitable for high-capacity, long-cycle-life power batteries, energy storage batteries, and batteries for portable electronic devices, and has industrial application value.

[0025] Furthermore, the chemical formula of the matrix is ​​La. 0.1 Ce 0.1 Y 0.8 Ni 3.25 Mn 0.15 Al 0.1 La 0.1 Ce 0.2 Y 0.7 Ni 3.25 Mn 0.15 Al 0.1 La 0.2 Ce 0.2 Y 0.6 Ni 3.25 Mn 0.15 Al 0.1 One of them.

[0026] Compared with the prior art, the present invention has the following significant advantages: This invention employs a synergistic design that partially replaces La with Ce and uses Mg2Ni as the magnesium source to mechanically alloy in situ generate a Mg-containing intermetallic compound nanophase. This approach maintains the integrity and order of the superlattice structure while optimizing crystal defects with Ce and suppressing alloy pulverization and structural decay through the Mg-containing nanophase. As a result, the electrochemical performance of the hydrogen storage alloy is significantly improved: the discharge capacity reaches 350~380 mAh / g, and the capacity retention rate after 500 charge-discharge cycles is ≥78%. Compared with La-Y-Ni-based alloys without Mg and Ce doping, the discharge capacity is increased by 20%~24.6%, and the cycle stability is improved by 18%~18.6%. The alloy exhibits excellent activation performance, and at 25℃ and a discharge current of 300 mA / g, the initial discharge capacity can reach more than 90% of the maximum discharge capacity.

[0027] This invention introduces Mg element by combining Mg2Ni powder with master alloy powder during the ball milling stage. This fundamentally avoids the volatilization loss and compositional loss caused by the low melting point and high saturated vapor pressure of Mg element when it is directly involved in high-temperature smelting, as well as the risk of dust explosion caused by directly introducing Mg powder through ball milling. This ensures that the deviation between the actual composition and the designed composition of the alloy is ≤±3.0wt.%, and the raw material utilization rate is increased to over 95%. This guarantees the precise control of the alloy composition and the efficient utilization of raw materials, improves the safety of the preparation process, and provides reliable technical support for large-scale production.

[0028] This invention achieves the control of the uniformity and stability of the superlattice structure by optimizing key process parameters such as temperature, holding time, and stirring parameters in vacuum induction melting, ball-to-material ratio, rotation speed, and time in ball milling, and temperature, heating rate, and holding time in vacuum annealing. The process has good repeatability and provides reliable technical support for large-scale industrial production.

[0029] The hydrogen storage alloy provided by this invention can be directly used as the negative electrode active material of nickel-metal hydride batteries, and is especially suitable for high-capacity, long-cycle-life power batteries, energy storage batteries and batteries for portable electronic devices, with significant prospects for industrial application. The high hydrogen storage capacity and excellent cycle stability of the alloy can improve the energy density and lifespan of nickel-metal hydride batteries and reduce battery usage costs. At the same time, as a clean and low-carbon energy source, the promotion and application of hydrogen energy helps to reduce fossil energy consumption and carbon emissions, which has important economic, social and environmental benefits and plays a positive supporting role in achieving the "dual carbon" goal. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a flowchart illustrating the preparation process of the La-Y-Ni hydrogen storage alloy of the present invention; Figure 2 The X-ray diffraction (XRD) pattern of the La-Y-Ni hydrogen storage alloy prepared in Example 1 of this invention; Figure 3 These are transmission electron microscopy (TEM) bright-field morphology images and high-resolution TEM images of nanoparticles of the La-Y-Ni hydrogen storage alloy prepared in Example 1 of this invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] Unless otherwise specified in the embodiments of the present invention, the techniques or conditions described in the literature in this field or the product instructions shall be followed; if the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be purchased through legitimate channels.

[0034] Example 1 This embodiment provides a La-Y-Ni based hydrogen storage alloy, the chemical formula of which is La. 0.1 Ce 0.1 Y 0.8 Ni 3.25 Mn 0.15 Al 0.1 The specific preparation method is as follows: Step 1: Vacuum induction melting of master alloy Weigh the raw materials according to atomic ratios: 14.18 g of La blocks (99.90%, 1~10 mm), 14.31 g of Ce blocks (99.90% purity, 1~10 mm), 72.64 g of Y particles (99.90% purity, 1~6 mm), 187.32 g of Ni strips (99.95% purity, 1~10 mm), 8.49 g of Mn particles (99.90% purity, 1~10 mm), and 2.78 g of Al particles (99.99% purity, 1~3 mm). To compensate for burn-off, La, Ce, and Y are in excess by 4 wt.%, and Al and Mn are in excess by 5 wt.%, for a total raw material mass of 300 g. Place the raw materials in a graphite crucible, put it into a vacuum induction melting furnace, and after closing the furnace, evacuate to 5×10⁻⁶. -3 Argon gas is introduced to 0.13 MPa after Pa; the melting power supply is started, the raw material in the furnace is heated to 1550 ℃ and held for 12 min, and stirring is kept uninterrupted during the holding period; after melting, it is poured into a copper mold and cooled to room temperature to obtain the master alloy ingot.

[0035] Step 2: High-energy ball milling composite After removing the scrap from the master alloy ingot prepared in step 1, it was wire-cut into small pieces (5~10 mm), and then ground in a rod mill to a particle size ≤200 mesh to obtain master alloy powder. 10 g of master alloy powder and 0.35 g of Mg2Ni powder (purity 99.90%, ≤100 mesh) were weighed and loaded into the vacuum ball mill jar of a planetary ball mill. Hard alloy grinding balls were added, and the ball-to-material ratio was controlled at 40:1. The above loading process was carried out in a glove box. After vacuuming, argon gas was introduced for protection. The rotation speed was set to 450 r / min, and the ball milling was carried out for 40 h. The ball milling program was set as follows: pause for cooling for 0.5 h every 1 h of ball milling, and clean the powder on the jar wall under an inert atmosphere every 5 h of ball milling. After the ball milling was completed, composite alloy powder was obtained.

[0036] Step 3: Vacuum annealing The composite alloy powder was loaded into an alumina crucible, placed in a vacuum annealing furnace, and after the furnace was closed, a vacuum of 3×10⁻⁶ was drawn. - 3 Argon gas was introduced into the furnace to a pressure of 0.1 MPa; the heating rate was set to 5 °C / min, and the temperature was raised to 850 °C and held for 6 h; after the holding period, the heating was stopped, and the alloy powder was allowed to cool to room temperature with the furnace. The target hydrogen storage alloy was then obtained.

[0037] Example 2 This embodiment provides a La-Y-Ni based hydrogen storage alloy, the chemical formula of which is La. 0.1 Ce 0.1 Y 0.8 Ni 3.25 Mn 0.15 Al0.1 The preparation method is basically the same as in Example 1, except that the mass of Mg2Ni powder added during ball milling is 0.70 g. All other steps are the same as in Example 1, and will not be repeated here.

[0038] Example 3 This embodiment provides a La-Y-Ni based hydrogen storage alloy, the chemical formula of which is La. 0.1 Ce 0.2 Y 0.7 Ni 3.25 Mn 0.15 Al 0.1 The preparation method is basically the same as in Example 1, except that in step 1, when vacuum induction melting the master alloy, the raw materials weighed according to atomic ratio are changed to: 13.54 g of La block, 27.32 g of Ce block, 60.68 g of Y particles, 186.00 g of Ni strip, 8.04 g of Mn particles, and 2.63 g of Al particles. To compensate for burn-off, La, Ce, and Y are in excess by 4 wt.%, and Al and Mn are in excess by 5 wt.%, with a total raw material mass of 300 g. Other steps are the same as in Example 1, and will not be repeated here.

[0039] Example 4 This embodiment provides a La-Y-Ni based hydrogen storage alloy, the chemical formula of which is La. 0.2 Ce 0.2 Y 0.6 Ni 3.25 Mn 0.15 Al 0.1 The preparation method is basically the same as in Example 1, except that: in step 1, when vacuum induction melting of the master alloy, the raw materials weighed according to atomic ratio are changed to: 28.26 g of La blocks, 28.51 g of Ce blocks, 54.26 g of Y particles, 186.56 g of Ni strips, 8.46 g of Mn particles, and 2.77 g of Al particles. To compensate for burn-off, La, Ce, and Y are in excess by 4 wt.%, and Al and Mn are in excess by 5 wt.%, with a total raw material mass of 300 g; in step 2, when high-energy ball milling is performed, the amount of Mg2Ni added is changed to 0.70 g. The other steps are the same as in Example 1, and will not be repeated here.

[0040] Example 5 This embodiment provides a La-Y-Ni based hydrogen storage alloy, the chemical formula of which is La. 0.1 Ce 0.1 Y 0.8 Ni 3.25 Mn 0.15 Al 0.1 The specific preparation method is as follows: Step 1: Vacuum induction melting of master alloy The melting temperature was 1450 ℃, and the holding time was 20 min. The remaining operations were the same as in Example 1.

[0041] Step 2: High-energy ball milling composite The rotation speed was 300 r / min, the ball milling time was 30 h, the ball milling program was to pause for cooling for 1 h every 1 h of ball milling, and clean the tank wall every 10 h of ball milling. The rest of the operation was the same as in Example 1.

[0042] Step 3: Vacuum annealing Set the heating rate to 4 ℃ / min, heat to 820 ℃ and hold for 7 h; the rest of the operation is the same as in Example 1.

[0043] Example 6 This embodiment provides a La-Y-Ni based hydrogen storage alloy, the chemical formula of which is La. 0.2 Ce 0.2 Y 0.6 Ni 3.25 Mn 0.15 Al 0.1 The specific preparation method is as follows: Step 1: Vacuum induction melting of master alloy The raw materials were weighed according to the atomic ratio: 28.26 g La blocks, 28.51 g Ce blocks, 54.26 g Y particles, 186.56 g Ni strips, 8.46 g Mn particles, and 2.77 g Al particles. To compensate for burn-off, La, Ce, and Y were in excess by 4 wt.%, and Al and Mn were in excess by 5 wt.%, for a total raw material mass of 300 g. The melting temperature was 1600 ℃, and the holding time was 10 min. The remaining operations were the same as in Example 1.

[0044] Step 2: High-energy ball milling composite The ball milling process was carried out at a speed of 500 r / min for 35 h. The ball milling program was as follows: pause and cool down for 0.8 h every 1 h of ball milling, and clean the powder from the tank wall under an inert atmosphere every 8 h of ball milling. The amount of Mg2Ni powder added was 0.7 g. The remaining operations were the same as in Example 1.

[0045] Step 3: Vacuum annealing The heating rate was 6 ℃ / min, and the temperature was raised to 900 ℃ and then held for 5 h. The rest of the operation was the same as in Example 1.

[0046] Comparative Example 1 This comparative example provides a La-Y-Ni based hydrogen storage alloy, with the chemical formula La. 0.2 Y 0.8 Ni 3.25 Al 0.1 Mn 0.15 (Without adding Ce and Mg elements), the specific preparation method is as follows: The raw materials were weighed according to atomic ratios as follows: 28.43 g of La blocks (99.90%, 1~10 mm), 72.89 g of Y particles (99.90% purity, 1~6 mm), 187.39 g of Ni strips (99.95% purity, 1~10 mm), 8.52 g of Mn particles (99.90% purity, 1~10 mm), and 2.79 g of Al particles (99.99% purity, 1~3 mm). To compensate for burn-off, La and Y were added in excess by 4 wt.%, and Al and Mn in excess by 5 wt.%, for a total raw material mass of 300 g. The raw materials were placed in a graphite crucible and then placed in a vacuum induction melting furnace, and the vacuum was evacuated to 5×10⁻⁶. -3 Argon gas was introduced to a pressure of 0.13 MPa after Pa; the temperature was raised to 1550 ℃ and held for 12 min, with continuous stirring during the holding period; after melting, it was poured into a copper mold and cooled to room temperature to obtain a master alloy ingot. The master alloy ingot was crushed and ground to a particle size ≤200 mesh.

[0047] Comparative Example 2 This comparative example provides a La-Y-Ni based hydrogen storage alloy, with the chemical formula La. 0.1 Ce 0.1 Y 0.8 Ni 3.25 Al 0.1 Mn 0.15 (Without adding Mg element), the specific preparation method is as follows: The raw materials were weighed according to the atomic ratio as follows: 14.18 g of La blocks (99.90%, 1~10 mm), 14.31 g of Ce blocks (99.90% purity, 1~10 mm), 72.64 g of Y particles (99.90% purity, 1~6 mm), 187.32 g of Ni strips (99.95% purity, 1~10 mm), 8.49 g of Mn particles (99.90% purity, 1~10 mm), and 2.78 g of Al particles (99.99% purity, 1~3 mm). To compensate for burn-off, La, Ce, and Y were added in excess by 4 wt.%, and Al and Mn in excess by 5 wt.%, for a total raw material mass of 300 g. The raw materials were placed in a graphite crucible and then placed in a vacuum induction melting furnace, and the vacuum was evacuated to 5×10⁻⁶. -3 Argon gas was introduced to a pressure of 0.13 MPa after Pa; the temperature was raised to 1550 ℃ and held for 12 min, with continuous stirring during the holding period; after melting, it was poured into a copper mold and cooled to room temperature to obtain a master alloy ingot. The master alloy ingot was crushed and ground to a particle size ≤200 mesh.

[0048] Comparative Example 3 This comparative example provides a La-Y-Ni based hydrogen storage alloy, with the chemical formula La. 0.1 Ce 0.1 Y 0.8 Ni 3.25 Al0.1 Mn 0.15 Mg 0.20 The preparation method uses a traditional process, where Ce and Mg are added together through melting, i.e., Mg is added directly through melting, without using the Mg2Ni form. The specific preparation method is as follows: The raw materials were weighed according to atomic ratios as follows: 14.01 g of La blocks (99.90%, 1~10 mm), 14.14 g of Ce blocks (99.90% purity, 1~10 mm), 70.77 g of Y particles (99.90% purity, 1~6 mm), 185.07 g of Ni strips (99.95% purity, 1~10 mm), 8.39 g of Mn particles (99.90% purity, 1~10 mm), 2.75 g of Al particles (99.99% purity, 1~3 mm), and 4.72 g of Mg particles (99.99% purity, 1~3 mm). To compensate for burn-off, La, Y, and Ce were added in excess by 4 wt.%, and Al and Mn in excess by 5 wt.%, for a total raw material mass of 300 g. The raw materials were placed in a graphite crucible and then placed in a vacuum induction melting furnace, and the vacuum was evacuated to 5×10⁻⁶. -3 Argon gas is introduced to a pressure of 0.13 MPa after Pa; the temperature is raised to 1550 ℃ and held for 12 min, with continuous stirring during the holding period; after melting, it is poured into a copper mold and cooled to room temperature to obtain a master alloy ingot. The master alloy ingot is crushed and ground to a particle size ≤200 mesh.

[0049] Comparative Example 4 This comparative example provides a La-Y-Ni based hydrogen storage alloy, employing the alloy chemical formula La of this invention. 0.1 Ce 0.1 Y 0.8 Ni 3.25 Mn 0.15 Al 0.1 The specific preparation method is as follows: Step 1: Vacuum induction melting of the master alloy, following exactly the steps in Example 1, to obtain the same master alloy ingot.

[0050] Step 2: Ball milling compounding The master alloy ingot was ground to a particle size ≤200 mesh. 10 g of master alloy powder and 0.35 g of Mg2Ni powder were weighed, loaded into a ball mill jar, and the ball-to-material ratio was controlled at 20:1. The rotation speed was set at 200 r / min, and the ball milling was carried out for 20 h without any intermittent cooling or jar wall cleaning steps. The composite alloy powder was obtained by ball milling directly until the time was up.

[0051] Step 3: Vacuum annealing The composite alloy powder was placed in a vacuum annealing furnace and evacuated to a vacuum level of 1×10⁻⁶. -2Argon gas was introduced to a pressure of 0.05 MPa; the heating rate was set to 10 °C / min, and the temperature was raised to 700 °C and held for 3 h. After the holding period, the furnace was cooled to obtain the comparative alloy.

[0052] Performance testing and results analysis (1) Crystal structure detection (XRD and TEM) The XRD pattern of the alloy in Example 1 showed that the main phase was an A2B7 type superlattice, with a small amount of AB3 and AB5 type impurities. After high-energy ball milling, new phase diffraction characteristics appeared, and the main phase still maintained the A2B7 type superlattice structure. TEM results showed that the alloy generated Mg-containing intermetallic compound nanophases in situ at the phase interface and grain boundary through mechanical alloying. The phase size was 20~50 nm, and there was no obvious agglomeration.

[0053] (2) Electrochemical performance testing (25℃, 300mA / g), the test results are shown in Table 1: Table 1. Results of Electrochemical Performance Testing

[0054] As can be seen from the data in Table 1, the hydrogen storage alloys prepared in Examples 1-6 of this invention exhibit excellent electrochemical performance: the discharge capacity can reach 350-380 mAh / g, and the capacity retention rate after 500 charge-discharge cycles is ≥78%. Compared with the La-Y-Ni based alloys without Mg and Ce doping, the discharge capacity is increased by 20%-24.6%, and the cycle stability is increased by 18%-18.6%. The alloys also exhibit excellent activation performance, and at 25℃ and a discharge current of 300 mA / g, the initial discharge capacity can reach more than 90% of the maximum discharge capacity.

[0055] (3) Component and safety testing (ICP-OES): The pretreatment method for ICP-OES is microwave digestion, and the digestion solution is aqua regia.

[0056] The elemental composition deviation of Examples 1-6 is ≤ ±2.9 wt.%, the raw material utilization rate is ≥95.3%, and there are no safety issues such as Mg volatilization, melt splashing, or dust explosion during the preparation process.

[0057] In Comparative Example 3, due to the direct high-temperature smelting of Mg, the Mg composition deviation reached -6.5 wt.% ± 1.2 wt.%, the raw material utilization rate was less than 85%, and slight melt splashing occurred during the smelting process.

[0058] Comparative Example 4 showed slight oxidation of the powder due to uninterrupted cooling during ball milling, resulting in a raw material utilization rate of only 88% and a composition deviation of ±3.5 wt.%.

[0059] The above test results show that the hydrogen storage alloy prepared by this invention is significantly superior to the existing technology in terms of crystal structure integrity, electrochemical performance, composition controllability and preparation safety, and has the value for large-scale industrial application.

[0060] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a La-Y-Ni based hydrogen storage alloy, characterized in that, The general chemical formula of the hydrogen storage alloy matrix is ​​La. 1-x-y Ce x Y y Ni 3.25 Mn 0.15 Al 0.1 , 0.05≤x≤0.20, 0.40≤y≤0.80; The preparation method includes the following steps: (1) Weigh La, Ce, Y, Ni, Mn and Al raw materials according to stoichiometric ratio, perform vacuum induction melting, cast and cool to obtain master alloy; (2) After grinding the master alloy into master alloy powder, it is ball-milled with Mg2Ni powder under a protective gas to obtain composite alloy powder; (3) The composite alloy powder is subjected to vacuum annealing and then cooled in the furnace.

2. The method for preparing the La-Y-Ni hydrogen storage alloy according to claim 1, characterized in that, In step (1), the vacuum of the vacuum induction melting is ≤5×10 -3 Pa, maintain the pressure at 0.10~0.15 MPa with protective gas, the temperature at 1450~1600 ℃, and the holding time at 10~20 min.

3. The method for preparing La-Y-Ni hydrogen storage alloy according to claim 1 or 2, characterized in that, In step (1), the purity of the La, Ce, Y, Ni, Mn and Al raw materials is ≥99.0%; preferably, the La and Ce raw materials are cleaned and degreased with anhydrous ethanol and dried; more preferably, the La, Ce and Y raw materials are in excess by 4 wt.% and the Al and Mn raw materials are in excess by 5 wt.%.

4. The method for preparing the La-Y-Ni hydrogen storage alloy according to claim 3, characterized in that, In step (2), the ball-to-material ratio during ball milling is 30~40:1, the rotation speed is 300~500 r / min, and the ball milling time is 30~40 h; preferably, the ball milling procedure is as follows: pause and cool down for 0.5~1 h every 1 h of ball milling, and clean the powder on the tank wall under an inert atmosphere every 5~10 h of ball milling.

5. The method for preparing the La-Y-Ni hydrogen storage alloy according to claim 4, characterized in that, In step (2), the atomic ratio of the Mg2Ni powder to the master alloy powder is (0.1~0.2):

1.

6. The method for preparing the La-Y-Ni hydrogen storage alloy according to claim 5, characterized in that, In step (2), the particle size of the master alloy powder is ≤200 mesh, and the particle size of the Mg2Ni powder is ≤200 mesh; preferably, the purity of the Mg2Ni powder is ≥99.90%.

7. The method for preparing La-Y-Ni hydrogen storage alloy according to claim 5 or 6, characterized in that, In step (3), the vacuum annealing is performed with a vacuum level of ≤5×10⁻⁶. -3 Pa, the pressure is maintained at 0.08~0.12 MPa by purging with protective gas, the annealing temperature is 820~900 ℃, and the holding time is 5~7 h; preferably, the holding time is 820 ℃ for 7 h, 850 ℃ for 6 h, or 900 ℃ for 5 h.

8. The method for preparing the La-Y-Ni hydrogen storage alloy according to claim 7, characterized in that, In step (3), the heating rate of the vacuum annealing is 4~6 ℃ / min.

9. A La-Y-Ni based hydrogen storage alloy, characterized in that, It is prepared by the method for preparing La-Y-Ni hydrogen storage alloy according to any one of claims 1-8.

10. The La-Y-Ni hydrogen storage alloy according to claim 9, characterized in that, The chemical formula of the matrix is ​​La. 0.1 Ce 0.1 Y 0.8 Ni 3.25 Mn 0.15 Al 0.1 La 0.1 Ce 0.2 Y 0.7 Ni 3.25 Mn 0.15 Al 0.1 La 0.2 Ce 0.2 Y 0.6 Ni 3.25 Mn 0.15 Al 0.1 One of them.

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