CN115449726B - Process annealing method of La-Mg-Ni series hydrogen storage alloy - Google Patents
Process annealing method of La-Mg-Ni series hydrogen storage alloy Download PDFInfo
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Abstract
The invention discloses a process annealing method of La-Mg-Ni series hydrogen storage alloy, which is high in speed in a short timeThe programmed annealing process of warm annealing and low-temperature recrystallization annealing can improve and increase (La, mg) 2 Ni 7 The phase content and the volatilization of magnesium metal are inhibited, the aim of improving the alloy performance is achieved, and the problem that the performance of the La-Mg-Ni hydrogen storage alloy is greatly different from the theoretical value due to the deviation of the components of the La-Mg-Ni hydrogen storage alloy caused by the volatilization of magnesium metal because the existing annealing process usually adopts long-time low-temperature annealing.
Description
The technical field is as follows:
the invention relates to the technical field of hydrogen storage alloys, in particular to a process annealing method of La-Mg-Ni hydrogen storage alloys.
Background art:
compared with the commonly used AB5 type alloy, the La-Mg-Ni (Ni/(La + Mg) = 3-4) hydrogen storage alloy has the advantages of high capacity, easy activation, better dynamic performance and the like; meanwhile, the alloy is environment-friendly, has higher energy density, is an ideal MH-Ni battery cathode material, and is expected to replace a commercialized AB5 type hydrogen storage alloy.
Vacuum induction melting (intermediate frequency induction melting-melt rapid quenching method) has the advantages of simple operation, high actual production efficiency, high heating speed, easy automation control and the like, and is a main method for industrially preparing the La-Mg-Ni series hydrogen storage alloy. However, the hydrogen storage properties of the alloy are greatly diminished due to the segregation of certain constituents during cooling. Annealing heat treatment is the most common method used to improve the electrochemical cycling performance of alloys.
In the annealing process, two parameters of heating temperature and heat preservation time have important influence on the performance of the alloy after heat treatment, and the heat treatment at proper temperature and heat preservation time can greatly improve the comprehensive performance of the alloy. However, annealing treatment at too high a temperature or for too long a holding time results in coarse grains and serious volatilization of Mg, which results in deterioration of the properties of the La-Mg-Ni-based hydrogen occluding alloy. The discharge capacity of the La-Mg-Ni-based hydrogen storage alloy produced industrially is only 342mA · h/g, which is greatly different from the theoretical maximum capacity 410mA · h/g, and the cycle life thereof is also poor.
The main phase of the La-Mg-Ni based hydrogen occluding alloy should be (La, mg) 2 Ni 7 The phase, however, is cooled at a high rate, and the occupation ratio of other phases is high, which affects the alloy performance. According to the study on La-Mg-Ni-H system phase equilibrium and its hydrogen absorption and desorption dynamics mechanism (La, mg) 2 Ni 7 The crystallization temperature of the phase was 1138 ℃. The temperature is far higher than the melting point of magnesium (650 ℃), and magnesium metal is easy to volatilize during vacuum annealing, so that the performance of the alloy is influenced. Therefore, the annealing process usually adopts long-time low-temperature annealing, and the volatilization of magnesium metal causes the component deviation of the La-Mg-Ni series hydrogen storage alloy, so that the difference between the performance of the La-Mg-Ni series hydrogen storage alloy and the theoretical value is larger.
In order to improve the performance of La-Mg-Ni series hydrogen storage alloy, the (La, mg) content of the La-Mg-Ni series hydrogen storage alloy is increased 2 Ni 7 The content of the phase needs to improve the heat treatment process of the alloy.
The invention content is as follows:
the invention aims to provide a programmed annealing method of La-Mg-Ni hydrogen storage alloy, which solves the problem that the performance and the theoretical value of the La-Mg-Ni hydrogen storage alloy are greatly different due to the composition deviation of the La-Mg-Ni hydrogen storage alloy caused by the volatilization of magnesium metal because the conventional annealing process usually adopts long-time low-temperature annealing.
The invention is realized by the following technical scheme:
a process annealing method of a La-Mg-Ni based hydrogen storage alloy, comprising the steps of:
1) Heating La-Mg-Ni hydrogen storage alloy prepared by vacuum induction melting from room temperature to above 1138 ℃, and carrying out short-time high-temperature annealing at the temperature for 3-5 min;
2) Then cooling to 850-1000 deg.C and holding the temperature, carrying out recrystallization annealing for 80-100min, and then cooling to room temperature.
Preferably, the temperature is raised to be higher than 1138 ℃ within half an hour in the step 1), and the temperature is lowered to be 850-1000 ℃ within half an hour in the step 2).
More preferably, the temperature of the step 2) is reduced to 950 ℃ and kept, recrystallization annealing is carried out for 90min, and then the temperature is cooled to room temperature.
Preferably, ni/(La + Mg) =3 to 4 in the La-Mg-Ni-based hydrogen storage alloy. More preferably, the La-Mg-Ni based hydrogen occluding alloy is (LaSm) 0.86 Mg 0.14 (NiZrAl) 3.42 And (3) alloying.
Short time high temperature (above 1138 ℃) annealing for 3-5min can provide sufficient energy breakthrough (La, mg) 2 Ni 7 The nucleation energy barrier of the phase is beneficial to shortening the nucleation period. Cooling to 850-1000 deg.C, maintaining the temperature, performing recrystallization annealing for 90min, and performing low temperature annealing at a longer temperature to obtain (La, mg) 2 Ni 7 Grow to a suitable crystal size and avoid magnesium metal volatilization.
The invention has the following beneficial effects:
the invention can improve and improve (La, mg) by a program annealing process of short-time high-temperature annealing and low-temperature recrystallization annealing 2 Ni 7 The phase content and the volatilization of magnesium metal are inhibited, the aim of improving the alloy performance is achieved, and the problem that the performance of the La-Mg-Ni hydrogen storage alloy is greatly different from the theoretical value due to the deviation of the components of the La-Mg-Ni hydrogen storage alloy caused by the volatilization of magnesium metal because the existing annealing process usually adopts long-time low-temperature annealing.
Description of the drawings:
fig. 1 is a schematic diagram of the process annealing process of examples 1-4;
FIG. 2 is an XRD diffraction pattern of the alloys after annealing according to the procedures of examples 1-4;
FIG. 3 is the phase abundances of the phases of the alloys after annealing according to the procedures of examples 1 to 4;
FIG. 4 is an activation curve of the alloy after annealing according to the procedure of examples 1 to 4;
FIG. 5 is a graph of the electrochemical cycling of the alloys after annealing according to the procedures of examples 1-4.
The specific implementation mode is as follows:
the following is a further description of the invention and is not intended to be limiting.
Example 1:
La-Mg-Ni series hydrogen storage alloy (LaSm) prepared by vacuum induction melting of Dabowen GmbH of Sihui city 0.86 Mg 0.14 (NiZrAl) 3.42 And carrying out heat treatment on the alloy ingot. In order to avoid the volatilization of magnesium metal, the hydrogen storage alloy is put into a quartz tube for sealing by melting before heat treatment, the protective gas in the quartz tube is argon, and the pressure is 100mbar.
The La-Mg-Ni series hydrogen storage alloy program annealing process comprises the following steps:
1) Will (LaSm) 0.86 Mg 0.14 (NiZrAl) 3.42 The alloy is heated from room temperature to 1140 ℃ within half an hour and is annealed at 1140 ℃ for 5min to obtain (La, mg) 2 Ni 7 The nucleation of the phase provides enough energy, and the incubation period of the nucleation is shortened;
2) Cooling to (La, mg) within half an hour 2 Ni 7 Recrystallizing and annealing at a temperature below the crystallization temperature of 1000 deg.C for 90min to obtain (La, mg) 2 Ni 7 Growing to a proper crystal size and avoiding magnesium metal volatilization; then cooling to room temperature along with the furnace.
Examples 2 to 4:
reference example 1, except that the temperatures of the recrystallization anneals were different, is specifically referred to table 1:
table 1 procedure annealing process for examples 1-4
Example 5: performance testing
The products prepared in examples 1 to 4 were analyzed for phase, hydrogen storage properties, electrochemical properties, and the like.
Phase analysis was tested using an X-ray diffractometer from Philips X' pert Pro. Examples 1-4 the prepared alloys were crushed to below 200 mesh and then tested under a 40KV Cu target with a scan angle of 20-90 deg. and a scan speed of 4 deg./min.
The charge and discharge performance and electrochemical test of the alloys prepared in examples 1-4 were performed in Ongzhou OptimusThe BS-9300 battery tester was tested with the princeton PARSTAT2273 electrochemical workstation. Weighing 0.2g (200 mesh sieve) of hydrogen storage alloy powder and 0.6g of hydroxyl nickel powder according to the mass ratio of 1
The alloy electrode sheet of (1).
The electrochemical charge and discharge performance test of the electrode plate is carried out in an open type double-electrode simulation battery system; wherein the negative electrode is an alloy electrode slice, and the positive electrode is a sintered nickel hydroxide/nickel oxyhydroxide electrode. The test process takes 6mol/L KOH +10g/L LiOH alkali solution as electrolyte, and the test temperature is constant temperature 25 ℃. The data is automatically recorded by a computer in the whole process of the electrochemical performance test. The maximum discharge capacity and the cycle performance of the alloy electrode are tested, the activation treatment of repeated charge and discharge is carried out on the alloy electrode, the activation and performance test system is shown in table 2, wherein the steps (a 1) and (a 2) are the activation process of the electrode slice, and the step (b) is the test process of the cycle performance of the alloy electrode.
TABLE 2 electrochemical test Charge/discharge regimes
Capacity retention ratio S after n cycles for cycle stability of alloy electrode n Represents:
wherein, C max 、C n The maximum discharge capacity of the alloy electrode at a constant current of 2C (640 mA/g) and the discharge capacity of the alloy electrode in the nth charge-discharge cycle are represented respectively. Definition of S n N value of about 80% is the cycle life of the alloy, S n Larger indicates longer cycle life of the alloy.
The original alloy was tested to consist of (La, mg) 2 Ni 7 Photo, (La, mg) 5 Ni 19 Phase and LaNi 5 The abundances of each phase are 32.6wt%, 38.3wt% and 29.1wt%. The maximum discharge capacity was 342 mA.h/g, and the cycle life was 260 times.
FIG. 2 is an XRD diffraction pattern of the products prepared in examples 1-4. As can be seen, after the process annealing, the alloy consists of the main phases (La, mg) 2 Ni 7 Photo, (La, mg) 5 Ni 19 Phase and LaNi 5 Phase composition. Analysis shows that the width of the diffraction peak of each phase is gradually narrowed along with the increase of the recrystallization annealing temperature, and the peak shape is sharper, which indicates that the lattice defects or lattice stress in the alloy are eliminated in the annealing process, namely the crystallinity and the uniformity of the components of the alloy are improved by heat treatment. Furthermore, a main phase (La, mg) 2 Ni 7 The diffraction peak positions of the phases gradually shifted to the right, indicating that the interplanar spacings decreased with increasing recrystallization annealing temperatures.
The phase abundances of the respective phases of the products prepared in examples 1 to 4 were calculated by the method of Rietveld refinement, and the results are shown in fig. 3. Alloys (La, mg) prepared in examples 1 to 4 2 Ni 7 The phase abundances are 60.1wt%, 68.7wt%, 58.6wt% and 54.5wt%, respectively, which are greatly improved compared to the phase abundance of the original alloy (32.6 wt%). Example 1 (La, mg) 2 Ni 7 The abundance of the phase was reduced by 8.6wt% compared to example 2, which is mainly due to the tendency of magnesium metal to volatilize during the higher temperature recrystallization annealing, resulting in (La, mg) 2 Ni 7 Phase decomposition into LaNi 5 Phase of simultaneous LaNi 5 And (La, mg) 2 Ni 7 Phase change to high temperature phase (La, mg) 5 Ni 19 And (4) phase.
FIG. 4 is an activation curve of alloy products prepared in examples 1 to 4. As can be seen from the graph, the maximum discharge capacities of the alloys of examples 1 to 4 were 334.6mA · h/g, 329.7mA · h/g, 319.4mA · h/g and 315.1mA · h/g, respectively, which were slightly lower than the maximum discharge capacity (342 mA · h/g) of the original alloy. In addition, the maximum discharge capacity can be achieved within 4 times of activation in the examples, which shows that the alloys prepared in examples 1 to 4 have good activation performance.
FIG. 5 is an electrochemical cycling curve for the alloys prepared in examples 1-4. It can be seen that the cycle life of the alloys prepared in examples 1-4 were 438, 507, 407, and 331, respectively, which were much higher than the cycle life of the original alloy (260).
Table 3 shows (La, mg) of the alloys prepared in examples 1 to 4 2 Ni 7 Phase abundance and electrochemical performance. (La, mg) 2 Ni 7 The phase abundance is positively correlated with the cycle stability thereof, (La, mg) 2 Ni 7 The higher the phase abundance, the longer its cycle life.
TABLE 3 (La, mg) of the alloys prepared in examples 1 to 4 2 Ni 7 Phase abundance and electrochemical performance
In view of the electrochemical properties of the alloys prepared in examples 1 to 4, example 2, which was subjected to heat treatment of high temperature annealing (1140 ℃, 5 min) + recrystallization annealing (950 ℃, 90 min), was effective in increasing the content of (La, mg) 2 Ni 7 The alloy greatly prolongs the cycle life while keeping higher discharge capacity, and has optimal comprehensive electrochemical performance.
Claims (4)
1. A process annealing method of La-Mg-Ni based hydrogen occluding alloy, characterized by comprising the steps of:
1) Heating La-Mg-Ni series hydrogen storage alloy prepared by vacuum induction melting from room temperature to 1138-1140 ℃, and carrying out short-time high-temperature annealing for 3-5min at the temperature; la-Mg-Ni based hydrogen occluding alloy (LaSm) 0.86 Mg 0.14 (NiZrAl) 3.42 Alloying;
2) Then cooling to 850-1000 deg.C and holding the temperature, carrying out recrystallization annealing for 90min, and then cooling to room temperature.
2. The method for program annealing La-Mg-Ni based hydrogen occluding alloy according to claim 1, wherein in the step 1), the temperature is raised to 1140 ℃ within half an hour.
3. The process annealing method of La-Mg-Ni based hydrogen occluding alloy according to claim 1, wherein in the step 2), the temperature is lowered to 850-1000 ℃ for half an hour.
4. The process annealing method of La-Mg-Ni-based hydrogen storage alloy according to claim 1, wherein step 2) is carried out by cooling to 950 ℃ for half an hour and holding the temperature, carrying out recrystallization annealing for 90min, and then cooling to room temperature.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101994030A (en) * | 2009-08-10 | 2011-03-30 | 北京有色金属研究总院 | Low-cost high-performance AB5 type hydrogen storage alloy and preparation method thereof |
| JP2013199703A (en) * | 2012-02-20 | 2013-10-03 | Gs Yuasa Corp | Hydrogen storage alloy, electrode, nickel-hydrogen storage battery and method for producing hydrogen storage alloy |
| CN108893656A (en) * | 2018-05-30 | 2018-11-27 | 安泰科技股份有限公司 | La-Mg-Ni system A2B7Type hydrogen storage alloy and preparation method thereof |
| CN111636012A (en) * | 2020-05-20 | 2020-09-08 | 有研工程技术研究院有限公司 | La-Mg-Ni series hydrogen storage material and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101994030A (en) * | 2009-08-10 | 2011-03-30 | 北京有色金属研究总院 | Low-cost high-performance AB5 type hydrogen storage alloy and preparation method thereof |
| JP2013199703A (en) * | 2012-02-20 | 2013-10-03 | Gs Yuasa Corp | Hydrogen storage alloy, electrode, nickel-hydrogen storage battery and method for producing hydrogen storage alloy |
| CN108893656A (en) * | 2018-05-30 | 2018-11-27 | 安泰科技股份有限公司 | La-Mg-Ni system A2B7Type hydrogen storage alloy and preparation method thereof |
| CN111636012A (en) * | 2020-05-20 | 2020-09-08 | 有研工程技术研究院有限公司 | La-Mg-Ni series hydrogen storage material and preparation method thereof |
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