CN101332976A - A kind of preparation method of Li-Mg-N-H hydrogen storage material - Google Patents

Abstract

The invention discloses a preparation method of a Li-Mg-N-H hydrogen storage material. Put a mixture of Li nitride or amide and Mg, Mg nitride or amide into a stainless steel tank, and use mechanical mixing or mechanical ball milling to make it evenly mixed; put the evenly mixed mixture into a sintering furnace, Vacuumize the sintering furnace or pass in an inert gas, heat it to a temperature range of 250-350°C and keep it warm to obtain a Li-Mg-N-H hydrogen storage material; put the Li-Mg-N-H hydrogen storage material into a ball mill The tank is subjected to ball milling on a ball mill, and the particle size of the sample powder after ball milling is less than 100nm. The invention has simple operation, easy control and low cost. The Li-Mg-N-H prepared and processed by the present invention has high hydrogen storage capacity, low hydrogen absorption and desorption working temperature, fast speed and good reversibility, and is a hydrogen storage material with superior performance, which can be used for hydrogen storage and transport.

Description

A kind of preparation method of Li-Mg-N-H hydrogen storage material

technical field

The invention relates to a hydrogen storage material, in particular to a preparation method of a novel Li-Mg-N-H hydrogen storage material.

Background technique

Hydrogen is known as a green energy carrier in the 21st century due to its abundant resources, high combustion efficiency, and no pollution. The use of hydrogen storage materials to store and transport hydrogen is safe, efficient, and low in cost, so it has attracted much attention. Practical hydrogen storage materials must meet the requirements of high hydrogen storage density, fast hydrogen absorption and desorption, moderate working temperature, and high safety. For the vehicle-mounted hydrogen source system for fuel cells, the International Energy Association (IEA) puts forward the goals for hydrogen storage materials that the mass hydrogen storage density is greater than 5%, the volume hydrogen storage density is greater than 50kg H ₂ /m ³ , and the hydrogen discharge temperature Lower than 150°C, and the cycle life exceeds 1000 times. The existing metal hydride hydrogen storage materials are difficult to meet the needs of practical application due to low hydrogen storage density or high working temperature. Therefore, there is an urgent need to research and develop new high-performance hydrogen storage materials.

In recent years, the discovery of light metal nitrogen hydride hydrogen storage materials has created a new field of new high-capacity hydrogen storage materials [P.Chen, ZTXiong, JZLuo, JYLin, KLTan, Nature, 2002, 420:302.] The reversible storage of hydrogen is achieved through the breaking and rebuilding of NH bonds. The reversible hydrogen storage capacity of the developed Li-Mg-NH hydrogen storage system is as high as 5.5wt% [ZTXiong, GTWu, JJHu, P. Chen, Advanced Materials, 2004, 16: 1522; WF Luo, J. Alloys Compd., 2004, 381:284.], thus arousing widespread concern. However, the current Li-Mg-NH hydrogen storage system is prepared from Mg(NH ₂ ) ₂ and 2LiH or LiNH ₂ and MgH ₂ . The above synthesis method uses metal hydrides LiH and MgH ₂ as raw materials, resulting in relatively low material cost. high. In addition, the Li-Mg-NH hydrogen storage materials synthesized by the above method also have disadvantages such as high hydrogen desorption working temperature and poor cycle stability. It can be seen that in order to further improve the hydrogen storage performance of Li-Mg-NH and reduce its cost, it is imminent to develop new methods for preparing Li-Mg-NH hydrogen storage materials using low-cost raw materials.

Contents of the invention

The purpose of the present invention is to provide a preparation method of Li-Mg-N-H hydrogen storage material.

The preparation method of Li-Mg-N-H hydrogen storage material comprises the following steps:

1) Under the condition of isolating the air, the mixture of the nitride or amide of Li and Mg, Mg nitride or amide is packed into a stainless steel tank with grinding balls;

2) By means of mechanical mixing or mechanical ball milling, the nitrides or amides of Li are uniformly mixed with the nitrides or amides of Mg and Mg, the weight ratio of the grinding ball and the sample is (10-100): 1, and the rotation speed is 30-550rpm, under vacuum, inert atmosphere, ammonia atmosphere or hydrogen atmosphere;

3) under the condition of isolating the air, the mixture of the nitride or amide of Li mixed uniformly and Mg, the nitride or amide of Mg is charged into the sintering furnace;

4) Vacuumize the sintering furnace, pass inert gas directly into the sintering furnace or pass inert gas after evacuating the sintering furnace, the pressure of the inert gas is 0.1-5atm, and the flow rate is 10-300mL/min;

5) heating the sintering furnace to a temperature range of 250-350° C., and holding time for 2-60 hours to obtain a Li-Mg-N-H hydrogen storage material;

6) Put the Li-Mg-N-H hydrogen storage material into a ball mill tank with balls in the air-isolated condition, and the ball-to-material ratio is (10-100):1;

7) Perform ball milling treatment on a ball mill, the ball milling time is 2-100h, the sample is protected in vacuum or inert atmosphere, and the particle size of the sample powder after ball milling is less than 100nm.

The composition of the mixture of Li nitride or amide and Mg, Mg nitride or amide is respectively Li ₃ N and Mg(NH ₂ ) ₂ , Li ₃ N and Mg, Li ₃ N and Mg ₃ N ₂ , LiNH ₂ and Mg, LiNH ₂ and Mg ₃ N ₂ , LiNH ₂ and Mg(NH ₂ ) ₂ , Li ₃ N, LiNH ₂ and Mg, Li ₃ N, LiNH ₂ and Mg ₃ N ₂ , Li ₃ N, LiNH ₂ and Mg(NH ₂ ) ₂ , Li ₃ N, Mg and Mg(NH ₂ ) ₂ , Li ₃ N, Mg and Mg ₃ N ₂ , LiNH ₂ , Mg and Mg(NH ₂ ) ₂ , LiNH ₂ , Mg and Mg ₃ N ₂ , LiNH ₂ , Mg ₃ N ₂ and Mg(NH ₂ ) ₂ , wherein the ratio of the mixture is such that the atomic ratio of Li to Mg is 1.9-2.5.

The nitrides or amides of Li and Mg, nitrides or amides of Mg are mechanically mixed or milled on an automatic mechanical powder mixer, a planetary ball mill or a vibration ball mill. The grinding balls used in the mechanical mixing or mechanical ball milling are stainless steel balls, zirconia balls or agate balls.

Li ₃ N _and Mg(NH ₂ ) ₂ , LiNH ₂ and Mg, LiNH ₂ and Mg ₃ N 2 , LiNH ₂ in the mixture of Li nitride or amide and Mg, Mg nitride or amide and Mg(NH ₂ ) ₂ , Li ₃ N, LiNH ₂ and Mg, Li ₃ N, LiNH ₂ and Mg 3 N ₂ , Li ₃ N, LiNH _{2 and} Mg(NH ₂ ) ₂ , Li ₃ N, Mg and Mg (NH ₂ ) ₂ , LiNH ₂ , Mg and Mg(NH ₂ ) ₂ , LiNH ₂ , Mg and Mg ₃ N ₂ , LiNH ₂ , Mg ₃ N ₂ and Mg(NH ₂ ) ₂ , use vacuum and inert atmosphere during ball milling , ammonia atmosphere or hydrogen atmosphere, the inert atmosphere is nitrogen atmosphere, argon atmosphere or helium atmosphere.

Li _{3 N} and Mg, Li ₃ N and Mg 3 N 2 , Li ₃ N, Mg and Mg ₃ N ₂ in _the mixture of Li nitride or amide and Mg, Mg nitride or amide, Ammonia or hydrogen atmosphere is used for ball milling;

The sintering furnace is a vacuum type, atmosphere type or vacuum atmosphere type sintering furnace, and the atmosphere type or vacuum atmosphere type sintering furnace is equipped with an inlet and outlet valve. The inert gas used for sintering is nitrogen, argon or helium.

The ball milling of the Li-Mg-N-H hydrogen storage material is carried out on a planetary ball mill or a vibration ball mill, and the speed of the planetary ball mill is 100-550rpm. The inert atmosphere for ball milling is nitrogen, argon or helium.

The ball-to-material ratio of the Li-Mg-N-H hydrogen storage material is 60:1, the ball milling speed is 550 rpm, the ball milling time is 36 hours, and the particle size of the sample powder after ball milling is 10-100 nm.

With the Li-Mg-N-H hydrogen storage material prepared by the present invention, the hydrogen storage capacity is kept above 5wt%, the working temperature of hydrogen absorption and desorption is reduced by 30%, the speed of hydrogen absorption and desorption is significantly accelerated, and the cycle stability is significantly improved. The raw materials are abundant and easy to obtain, the cost is low, and the preparation process is simple to operate and easy to control, which is beneficial to the industrialization of the technology.

Description of drawings

Figure 1 is the X-ray diffraction spectrum of the Li-Mg-NH sample prepared by sintering Li ₃ N-Mg(NH ₂ ) ₂ as a raw material;

Figure 2 is the infrared spectrum of the Li-Mg-NH sample prepared from LiNH ₂ -Mg ₃ N ₂ -Mg(NH ₂ ) ₂ as raw material;

Figure 3 is the X-ray diffraction spectrum of the Li-Mg-NH sample prepared from LiNH ₂ -Mg ₃ N ₂ as raw material;

Figure 4 is the X-ray spectrum of the Li-Mg-NH sample prepared from Li ₃ N-Mg-Mg ₃ N ₂ as raw material;

Figure 5 is the infrared spectrum of the Li-Mg-NH sample prepared from Li ₃ N-LiNH ₂ -Mg(NH ₂ ) ₂ as the raw material;

Fig. 6 is the comparison diagram of the hydrogen absorption curve of the Li-Mg-N-H sample prepared by the present invention and the Li-Mg-N-H sample prepared by the traditional method;

Fig. 7 is the temperature-dependent dehydrogenation curve of the Li-Mg-N-H sample prepared by the present invention;

Fig. 8 is a comparison diagram of hydrogen desorption kinetics after one cycle of the Li-Mg-N-H sample prepared by the present invention and the Li-Mg-N-H sample prepared by the traditional method.

Detailed ways

Mix Li nitride (Li ₃ N) or amide (LiNH ₂ ) with Mg, Mg nitride (Mg ₃ N ₂ ) or amide (Mg(NH ₂ ) ₂ ) in a certain molar ratio to form Li ₃ N and Mg(NH ₂ ) ₂ , Li ₃ N and Mg, Li ₃ N and Mg ₃ N ₂ , LiNH ₂ and Mg, LiNH ₂ and Mg ₃ N ₂ , LiNH ₂ and Mg(NH ₂ ) ₂ , Li ₃ N , LiNH ₂ and Mg, Li ₃ N, LiNH ₂ and Mg ₃ N ₂ , Li ₃ N, LiNH ₂ and Mg(NH ₂ ) ₂ , Li ₃ N, Mg and Mg(NH ₂ ) ₂ , Li ₃ N, Mg and Mg ₃ N ₂ , LiNH ₂ , Mg and Mg(NH ₂ ) ₂ , a mixture of LiNH ₂ , Mg and Mg ₃ N ₂ , LiNH ₂ , Mg ₃ N ₂ and Mg(NH ₂ ) ₂ , and then the mixture was separately Mechanical mixing or mechanical ball milling is carried out under the corresponding atmosphere, and the ball-to-material ratio is (10-100):1. The uniformly mixed mixture is sintered in a vacuum or inert atmosphere to prepare a Li-Mg-NH hydrogen storage material, which is analyzed by X-ray diffraction and infrared spectroscopy. Under the protection of vacuum or inert atmosphere, the Li-Mg-NH samples prepared by sintering were subjected to mechanical ball milling treatment, and the structure and hydrogen absorption and desorption properties of the samples were tested. Since samples are more likely to react with oxygen and water, all sample weighing and sample transfer are carried out in a glove box filled with high-purity argon or nitrogen, and the content of oxygen and water in the glove box is less than 50ppm.

The X-ray diffraction data of the samples were collected on the Rikagu D/MAX-RA diffractometer in Japan, and the infrared spectrum characterization of the samples was carried out on the Bruker Vector 22 infrared tester.

The hydrogen absorption and desorption behavior of the sample is carried out on the program temperature control desorption system, and the hydrogen absorption and desorption performance test is carried out on the gas state performance testing equipment. For the hydrogen release test, the reaction system was evacuated to 10 ^-2 atm before the test. For the hydrogen absorption test, the initial hydrogen pressure of the system is 80atm, and the hydrogen absorption and desorption process is heated from room temperature to the corresponding temperature at a heating rate of 2°C/min using the AI-708P programmable temperature controller. During the experiment, the hydrogen pressure of the reaction system, the program temperature and the temperature measured by the thermocouple were automatically recorded over time.

Example 1

In a glove box filled with Ar gas, Li ₃ N and Mg(NH ₂ ) ₂ , LiNH ₂ and Mg, LiNH ₂ and Mg(NH ₂ ) ₂ , LiNH ₂ , Mg and Mg(NH ₂ ) ₂ were respectively pressed by 2 : 3, 1.95: 1, 2: 1 and 2.5: 0.5: 0.5 molar ratio mixed, put into a sealable stainless steel tank, protected by argon, mechanically mixed on an automatic mechanical powder mixer, ball to material ratio 40:1 , speed 90rpm, mixing time 8h. Put the uniformly mixed mixture into the atmosphere type sintering furnace under the condition of isolating the air, protect it with nitrogen flow, nitrogen pressure 2atm, flow rate 100mL/min, sample sintering temperature 250℃, holding time 36h, sintering to prepare Li-Mg -NH hydrogen storage material. The molar ratios of the mixed samples and their mixing and sintering preparation conditions are listed in Table 1. The X-ray diffraction test of the samples prepared by sintering revealed that the samples presented a diffraction pattern of Li ₂ MgN ₂ H ₂ . FIG. 1 exemplarily shows the X-ray diffraction spectrum of a Li-Mg-NH sample prepared by sintering Li ₃ N-Mg(NH ₂ ) ₂ as a raw material. It can be seen from the figure that the diffraction peak of the sample is sharper and the half-peak width is smaller, indicating that its crystallinity is good.

Example 2

In a glove box filled with Ar gas, a mixture of LiNH ₂ and Mg(NH ₂ ) ₂ with a molar ratio of 2.05:1 was put into a ball mill jar with a switch valve, and after the ball mill jar was pre-evacuated, the Perform ball milling and mixing, the ball-to-material ratio is 55:1, the rotation speed is 550 rpm, and the ball milling time is 6 hours. Then, the mixture was placed in an atmosphere sintering furnace under the condition of isolating the air, protected by nitrogen flow, nitrogen pressure 1.6atm, flow rate 70mL/min, sample sintering temperature 280°C, holding time 30h, sintering to prepare Li-Mg-NH Hydrogen storage material. The mixed sintering preparation parameters of the samples are also listed in Table 1. The X-ray diffraction test of the samples prepared by sintering showed that the product mainly contained Li ₂ MgN ₂ H ₂ phase.

Example 3

In a glove box filled with nitrogen, put the mixture of LiNH ₂ and Mg ₃ N ₂ and Mg(NH ₂ ) ₂ with a molar ratio of 2:0.1:0.7 into a sealable stainless steel tank, use nitrogen protection, and mix the powder in an automatic machine Mechanical mixing is carried out on the machine, the ball-to-material ratio is 80:1, the rotation speed is 60 rpm, and the mixing time is 12 hours. Then transfer the homogeneous mixture to a vacuum sintering furnace without exposure to the air, using vacuum protection, the vacuum degree is 10 ^-2 -10 ^-6 atm, the sample sintering temperature is 300°C, and the holding time is 24h , Li-Mg-NH hydrogen storage material prepared by sintering. The mixing and sintering preparation conditions of the samples are also listed in Table 1. Infrared spectrum test was carried out on the sintered sample, and Fig. 2 shows the infrared spectrum of the Li-Mg-NH sample prepared with LiNH ₂ -Mg ₃ N ₂ -Mg(NH ₂ ) ₂ as raw material. It can be seen from the figure that in the wavenumber range of 2400-3600cm ^-1 , only one NH vibration can be detected around 3176cm ^-1 , which is a typical vibration absorption peak of imide Li ₂ MgN ₂ H ₂ .

Example 4

In a glove box filled with Ar gas, the mixture of LiNH ₂ and Mg ₃ N ₂ with a molar ratio of 6:1 was put into a sealable stainless steel tank, protected by argon, and mixed by ball milling on a vibrating ball mill. 50:1, mixing time 6h. Put the uniformly mixed mixture into the atmosphere sintering furnace under the condition of isolating the air, protect it with helium flow, the helium pressure is 0.2atm, the flow rate is 30mL/min, the sample sintering temperature is 315°C, and the holding time is 16h, sintering to prepare Li- Mg-NH hydrogen storage material. The X-ray diffraction test was carried out on the samples prepared by sintering, and Fig. 3 shows the X-ray pattern of the samples prepared by sintering. It can be seen from the figure that the sample presents a Li ₂ MgN ₂ H ₂ diffraction pattern with a mixed structure.

Example 5

In a glove box filled with Ar gas, the molar ratios of Li ₃ N and Mg, Li ₃ N and Mg ₃ N ₂ , LiNH _{2 and Mg, LiNH 2 and Mg 3} N ₂ , Li ₃ N, LiNH ₂ and Mg, Li ₃ N, Mg and Mg ₃ N ₂ , LiNH ₂ , Mg The mixture of Mg ₃ N 2 and Mg 3 N ₂ is put into a ball mill tank with on-off valve. After the ball mill tank is pre-evacuated, 8 atm of ammonia gas is filled, and the ball mill is mixed on a planetary ball mill. The ball-to-material ratio is 100:1, and the speed is 500rpm, ball milling time is 24h. Then, the evenly mixed mixture was placed in a vacuum atmosphere sintering furnace under the condition of isolating the air. Firstly, after pre-evacuation, it was protected by nitrogen flow. After 12 hours, Li-Mg-NH hydrogen storage material was prepared by sintering. The molar ratios of the mixed samples and their mixed sintering preparation parameters are listed in Table 1. The samples prepared by sintering were tested by X-ray diffraction. Fig. 4 shows the X-ray spectrum of the Li-Mg-NH sample prepared from Li ₃ N-Mg-Mg ₃ N ₂ as raw material. It can be found from the figure that the sample also exhibits the diffraction pattern of Li ₂ MgN ₂ H ₂ .

Example 6

In a glove box filled with Ar gas, massage Li ₃ N, LiNH ₂ and Mg ₃ N ₂ , Li ₃ N, LiNH ₂ and Mg(NH ₂ ) ₂ , Li ₃ N, Mg and Mg(NH ₂ ) ₂ respectively The ratio of 1:3:1, 1.2:3:1 and 2.05:1:2 is mixed, and the mixed sample is put into a ball mill tank with a switch valve. The ball mill tank is first pre-evacuated, and then filled with 30 atm of hydrogen protection. Ball milling and mixing were performed on a planetary ball mill with a ball-to-material ratio of 60:1, a rotational speed of 400 rpm, and a ball milling time of 36 hours. After the ball milling is completed, put the uniformly mixed mixture into the atmosphere sintering furnace under the condition of not exposing to the air, protected by argon flow, the argon pressure is 0.5atm, the flow rate is 40mL/min, the sample sintering temperature is 350°C, and the holding time is 6h, sintering to prepare Li-Mg-NH hydrogen storage material. The molar ratios of the mixed samples and their mixing and sintering parameters are listed in Table 1. The sintered samples were tested by infrared spectroscopy. Fig. 5 shows the infrared spectrum of the Li-Mg-NH sample prepared from Li ₃ N-LiNH ₂ -Mg(NH ₂ ) ₂ as raw material. It can be seen from the figure that an NH vibrational absorption peak around 3171cm ^-1 can be detected, which should be the characteristic vibrational absorption peak of imide Li ₂ Mg ₂ N ₂ H ₂ .

Table 1 Molar ratios of different mixtures and mixing and sintering preparation conditions

samples The molar ratio of Hybrid mixed protective atmosphere Ball material ratio Speed (rev/min) Mixing time (hours) Sintering protective atmosphere Sintering temperature (Celsius) Sintering time (hours) Li ₃ N-Mg(NH ₂ ) ₂ 2:3 mechanical mixing Ar 40:1 90 8 N ₂ 250 36 Li ₃ N-Mg 2:3.02 Planetary ball mill NH ₃ 100:1 500 twenty four N ₂ 320 12 Li ₃ N-Mg ₃ N ₂ 2.2:1 Planetary ball mill NH ₃ 100:1 500 twenty four N ₂ 320 12 LiNH ₂ -Mg 1.95:1 mechanical mixing Ar 40:1 90 8 N ₂ 250 36 LiNH ₂ -Mg 2.1:1 Planetary ball mill NH ₃ 100:1 500 twenty four N ₂ 320 12 LiNH ₂ -Mg ₃ N ₂ 6:1 Vibration ball mill Ar 50:1 6 He 315 16 LiNH ₂ -Mg ₃ N ₂ 6.05:1 Planetary ball mill NH ₃ 100:1 500 twenty four N ₂ 320 12 LiNH ₂ -Mg(NH ₂ ) ₂ 2:1 mechanical mixing Ar 40:1 90 8 N ₂ 250 36 LiNH ₂ -Mg(NH ₂ ) ₂ 2.05:1 Planetary ball mill vacuum 55:1 550 6 N ₂ 280 30 Li ₃ N-LiNH ₂ -Mg 1:1:2 Planetary ball mill NH ₃ 100:1 500 twenty four N ₂ 320 12 Li ₃ N-LiNH ₂ -Mg ₃ N ₂ 1:3:1 Planetary ball mill H ₂ 60:1 400 36 Ar 350 6 Li ₃ N-LiNH ₂ -Mg(NH ₂ ) ₂ 1.2:3:1 Planetary ball mill H ₂ 60:1 400 36 Ar 350 6 Li ₃ N-Mg-Mg(NH ₂ ) ₂ 2.05:1:2 Planetary ball mill H ₂ 60:1 400 36 Ar 350 6 Li ₃ N-Mg-Mg ₃ N ₂ 2.2:1:2 Planetary ball mill NH ₃ 100:1 500 twenty four N ₂ 320 12 LiNH ₂ -Mg-Mg(NH ₂ ) ₂ 2.5:0.5:0.5 mechanical mixing Ar 40:1 90 8 N ₂ 250 36 LiNH ₂ -Mg-Mg ₃ N ₂ 2:0.4:0.2 Planetary ball mill NH ₃ 100:1 500 twenty four N ₂ 320 12 LiNH ₂ -Mg ₃ N ₂ -Mg(NH ₂ ) ₂ 2:0.1:0.7 mechanical mixing N ₂ 80:1 60 12 vacuum 300 twenty four

Example 7

In a glove box filled with argon, the Li-Mg-N-H hydrogen storage material prepared in Example 1 was put into a ball mill jar, and the sample was ball milled with a vibrating ball mill under the protection of argon. The weight ratio of the sample to the grinding ball is 40:1, and the ball milling time is 6-36h. The hydrogen absorption properties of the samples after ball milling were tested, and the results are listed in Table 2. It can be seen from the table that after ball milling, the samples can absorb hydrogen within the range of 50-150°C, and the hydrogen absorption exceeds 5wt%, which reflects that they have good hydrogen absorption performance.

Table 2 Hydrogen storage properties of some Li-Mg-N-H samples prepared by sintering after ball milling

samples Milling time Hydrogen absorption start temperature (Celsius) Hydrogen absorption (weight percent) Li ₃ N-Mg(NH ₂ ) ₂ 6 150 5.1 LiNH ₂ -Mg 12 130 5.2 LiNH ₂ -Mg(NH ₂ ) ₂ 18 90 5.3 LiNH ₂ -Mg-Mg(NH ₂ ) ₂ 36 50 5.3

Example 8

In a glove box filled with nitrogen, put the Li-Mg-N-H hydrogen storage materials prepared in Example 2, Example 3 and Example 4 into a ball mill jar, and the samples were milled using a vibrating ball mill under the protection of nitrogen. deal with. The weight ratio of sample to balls was 60:1. The hydrogen absorption performance of the samples after ball milling was tested.

Comparative Example 1

In a glove box filled with nitrogen, Mg(NH ₂ ) ₂ and LiH were mixed at a molar ratio of 1:2, and put into a ball mill jar. Under the protection of nitrogen, the samples were milled with a vibrating ball mill. The weight ratio of sample to balls was 60:1. After ball milling, the samples were dehydrogenated first, and then their hydrogen absorption performance was tested.

FIG. 6 shows the hydrogen absorption curves of Li-Mg-N-H prepared according to Example 8 and Comparative Example 1 respectively. It can be seen from the figure that the hydrogen absorption capacity of Li-Mg-N-H prepared by the present invention can reach 5.0wt%, the hydrogen absorption start temperature is only 50°C, and the hydrogen absorption temperature is significantly lowered.

Example 9

In a glove box filled with argon, put the Li-Mg-N-H hydrogen storage material prepared in Example 5 into a ball mill tank, and perform ball milling on a planetary ball mill. The sample is protected by argon, and the ball-to-material ratio is 100. : 1, the rotating speed is 400rpm. After ball milling, the samples first absorb hydrogen at low temperature, and then test their hydrogen desorption performance. Figure 7 shows the hydrogen desorption behavior of the sample with increasing temperature. It can be seen from the figure that the initial hydrogen desorption temperature of the sample is around 120°C, and the total hydrogen desorption amount can reach 5.0wt%.

Example 10

In a glove box filled with argon, put the Li-Mg-N-H hydrogen storage material prepared in Example 6 into a ball mill jar with a switch valve, then vacuumize the ball mill jar, and perform ball milling on a planetary ball mill , the ball-to-material ratio is 80:1, and the rotational speed is 550rpm. After ball milling, the samples first absorb hydrogen at low temperature, and then test their hydrogen desorption kinetics.

Comparative example 2

In a glove box filled with argon, mix Mg(NH ₂ ) ₂ and LiH at a molar ratio of 1:2, put them into a ball mill tank with a switch valve, and then vacuumize the ball mill tank, and on a planetary ball mill Ball milling was carried out with a ball-to-material ratio of 80:1 and a rotational speed of 550 rpm. After ball milling, the sample was subjected to a hydrogen desorption and hydrogen absorption cycle first, and then the hydrogen desorption kinetics of the sample after hydrogen absorption was tested.

Figure 8 shows the comparison curves of hydrogen desorption kinetics of the samples prepared in Example 10 and Comparative Example 2. It can be seen from the figure that the hydrogen desorption kinetics of the Li-Mg-N-H hydrogen storage material prepared by the present invention is significantly improved compared with the sample in Comparative Example 2 during the cycle.

Claims (10)

1. the preparation method of a Li-Mg-N-H hydrogen storage material is characterized in that comprising the steps:

1) under the condition of secluding air, the mixture of the nitride of the nitride of Li or amides and Mg, Mg or amides packed into is placed with the stainless cylinder of steel of abrading-ball;

2) mode of employing mechanically mixing or mechanical ball milling, make the nitride of Li or nitride or the amides uniform mixing of amides and Mg, Mg, the weight ratio of abrading-ball and sample is (10-100): 1, and rotating speed is 30-550rpm, carries out under vacuum, inert atmosphere, ammonia atmosphere or nitrogen atmosphere;

3) under the condition of secluding air, the mixture of the nitride of the nitride of the Li that mixes or amides and Mg, Mg or amides is packed in the sintering oven;

4) sintering oven is vacuumized, directly feeds rare gas element or sintering oven is vacuumized back feeding rare gas element in sintering oven, inert gas pressure is 0.1-5atm, and flow velocity is 10-300mL/min;

5) sintering oven is heated to 250-350 ℃ temperature range, soaking time is 2-60h, obtains the Li-Mg-N-H hydrogen storage material;

6) under the condition of secluding air, the Li-Mg-N-H hydrogen storage material packed into is placed with the ball grinder of abrading-ball, and ratio of grinding media to material is (10-100): 1;

7) carry out ball-milling processing on ball mill, the ball milling time is 2-100h, and sample is in vacuum or inert atmosphere protection, and the particle diameter of sample powder is less than 100nm behind the ball milling.

2. the preparation method of a kind of Li-Mg-N-H hydrogen storage material according to claim 1 is characterized in that the nitride of described Li or the nitride of amides and Mg, Mg or the mixture composition of amides divide other to be Li ₃N and Mg (NH ₂) ₂, Li ₃N and Mg, Li ₃N and Mg ₃N ₂, LiNH ₂And Mg, LiNH ₂And Mg ₃N ₂, LiNH ₂And Mg (NH ₂) ₂, Li ₃N, LiNH ₂And Mg, Li ₃N, LiNH ₂And Mg ₃N ₂, Li ₃N, LiNH ₂And Mg (NH ₂) ₂, Li ₃N, Mg and Mg (NH ₂) ₂, Li ₃N, Mg and Mg ₃N ₂, LiNH ₂, Mg and Mg (NH ₂) ₂, LiNH ₂, Mg and Mg ₃N ₂, LiNH ₂, Mg ₃N ₂And Mg (NH ₂) ₂, wherein the ratio of mixture makes that the atomic ratio of Li and Mg is 1.9～2.5.

3. the preparation method of a kind of Li-Mg-N-H hydrogen storage material according to claim 1 is characterized in that the nitride of described Li or nitride or the amides of amides and Mg, Mg carry out mechanically mixing or mechanical ball milling on automation mixed powder machine, planetary ball mill or oscillatory type ball mill.

4. the preparation method of a kind of Li-Mg-N-H hydrogen storage material according to claim 3 is characterized in that the abrading-ball that described mechanically mixing or mechanical ball milling adopt is Stainless Steel Ball, zirconia ball or agate ball.

5. the preparation method of a kind of Li-Mg-N-H hydrogen storage material according to claim 1 is characterized in that the Li in the mixture of the nitride of the nitride of described Li or amides and Mg, Mg or amides ₃N and Mg (NH ₂) ₂, LiNH ₂And Mg, LiNH ₂And Mg ₃N ₂, LiNH ₂And Mg (NH ₂) ₂, Li ₃N, LiNH ₂And Mg, Li ₃N, LiNH ₂And Mg ₃N ₂, Li ₃N, LiNH ₂And Mg (NH ₂) ₂, Li ₃N, Mg and Mg (NH ₂) ₂, LiNH ₂, Mg and Mg (NH ₂) ₂, LiNH ₂, Mg and Mg ₃N ₂, LiNH ₂, Mg ₃N ₂And Mg (NH ₂) ₂, adopting vacuum, inert atmosphere, ammonia atmosphere or nitrogen atmosphere during ball milling, described inert atmosphere is nitrogen atmosphere, argon atmospher or helium-atmosphere.

6. the preparation method of a kind of Li-Mg-N-H hydrogen storage material according to claim 1 is characterized in that the Li in the mixture of the nitride of the nitride of described Li or amides and Mg, Mg or amides ₃N and Mg, Li ₃N and Mg ₃N ₂, Li ₃N, Mg and Mg ₃N ₂, adopt ammonia atmosphere or nitrogen atmosphere during ball milling;

7. the preparation method of a kind of Li-Mg-N-H hydrogen storage material according to claim 1 is characterized in that described sintering oven is vacuum type, atmosphere formula or vacuum atmosphere formula sintering oven, and atmosphere formula or vacuum atmosphere formula sintering oven are equipped with the air valve door.The used rare gas element of sintering is nitrogen, argon gas or helium.

8. the preparation method of a kind of Li-Mg-N-H hydrogen storage material according to claim 1, the ball milling that it is characterized in that described Li-Mg-N-H hydrogen storage material carries out on planetary ball mill or oscillatory type ball mill, and the rotating speed of planetary ball mill is 100-550rpm.

9. the preparation method of a kind of Li-Mg-N-H hydrogen storage material according to claim 1 is characterized in that described ball milling inert atmosphere is nitrogen, argon gas or helium.

10. the preparation method of a kind of Li-Mg-N-H hydrogen storage material according to claim 1, the ratio of grinding media to material that it is characterized in that described Li-Mg-N-H hydrogen storage material is 60: 1, rotational speed of ball-mill is 550rpm, and the ball milling time is 36h, and the particle diameter of sample powder is 10-100nm behind the ball milling.

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