A nano-thin film coated modified light metal hydride and a method for preparing the same

Abstract

This invention provides a method for preparing a nanofilm-coated modified light metal hydride, wherein the modified light metal hydride uses a light metal hydride as the core and a nanofilm as the surface modification layer. The light metal hydride is lithium hydride, aluminum hydride, magnesium hydride, or zirconium hydride. The nanofilm is an organic thin film or an inorganic-organic hybrid thin film. The nanofilm is deposited on the surface of the light metal hydride using molecular layer deposition (MLD). The mass of the nanofilm accounts for 0.1% to 5% of the total mass of the modified light metal hydride. The thickness of the nanofilm is 0.01 to 200 nm. The nanofilm of this invention can completely and uniformly cover the entire outer surface of the light metal hydride particles, with a thickness precisely adjustable within the nanometer range, and has minimal impact on the energy of the light metal hydride. The nanofilm prepared by this invention exhibits good shape retention, and the original morphology of the light metal hydride sample is not altered after coating.

Description

Technical Field

[0001] This invention belongs to the field of light metal hydride technology, and relates to the surface modification of light metal hydrides, specifically to a light metal hydride modified by nanofilm coating and its preparation method. Background Technology

[0002] Light metal hydrides are currently the most widely researched and promising class of solid-state hydrogen storage materials both domestically and internationally. Light metal hydride hydrogen storage materials typically refer to those with high hydrogen storage capacity, such as LiH (12.5%), AlH3 (10.08%), MgH2 (7.6%), and zirconium hydride (2.15%), and are mainly used in fuel cells and special energy power (solid propellants and high-energy explosives). In the field of fuel cells, the high hydrogen storage capacity of light metal hydrides far exceeds the mass and volumetric hydrogen storage capacities of 5.5% and 40 kg / m³ in on-board hydrogen storage systems. 3 The target requirements demonstrate the high application value of MgH2 as a hydrogen storage carrier in hydrogen fuel cells. In particular, MgH2 possesses the highest known mass hydrogen storage density among reversible hydride hydrogen storage materials, making it almost the only hydride capable of meeting the technical requirements for on-board hydrogen storage capacity. Although AlH3 exhibits poor reversibility in hydrogen absorption and desorption, it has significant application potential in special power systems such as portable power supplies for military and industrial use, and underwater vehicles. In the field of special energy power, using light metal hydrides as a high-energy fuel can significantly improve the work-capacity of solid propellants and the energy level of explosives.

[0003] Despite the promising applications of light metal hydrides in the aforementioned fields, these materials still face several insurmountable bottlenecks in their large-scale practical application. For example, light metal hydrides exhibit strong reducing properties, readily reacting with oxygen and moisture in the air, resulting in a significant reduction in hydrogen content. These materials typically require use in water- and oxygen-proof glove boxes, hindering large-scale industrial application. Furthermore, aluminum hydride itself suffers from poor chemical and thermal stability, readily decomposing and making it unsuitable for long-term storage and use. Surface modification of light metal hydrides through coating is an effective way to improve their thermal and water / oxygen stability.

[0004] Chinese invention patent ZL201710390777.7 discloses a method for in-situ polymerization coating and passivation of metal hydrides. This method uses a liquid-phase method to in-situ polymerize and coat BAMO-THF copolyether onto the surface of metal hydrides to improve their water and oxygen stability. Chinese invention patent application 201911266781.8 discloses a solvent-non-solvent method for coating metal hydrides. This method uses a solvent-non-solvent method to coat energetic binders such as poly(azide glycidyl ether) onto the surface of metal hydrides to improve their chemical stability. Chinese invention patent application 201510991738.3 discloses a method for in-situ polymerization coating modification of metal hydrides. This method uses an in-situ polymerization reaction to coat polydicyclopentadiene onto the surface of metal hydrides to form an isolation and protective layer, thereby improving their stability.

[0005] The disadvantages of the methods disclosed above are that the coating process is completed in an organic liquid phase, the process is complex, and the product needs to be separated by means of filtration and solvent evaporation, requiring a large amount of manual operation. In addition, these methods lack precise control over the coating process, and the coating thickness is difficult to adjust precisely (the coating thickness is mostly on the micrometer scale, making it difficult to achieve nanoscale film coating). The integrity, uniformity, and density of the coating layer are poor, which easily leads to the loss of hydrogen content in the metal hydride. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a nanofilm-coated modified light metal hydride and its preparation method, thereby solving the technical problem that the coating film is difficult to achieve precise and controllable operation at the nanoscale in existing technologies, resulting in a significant impact of the coating film on the energy of the light metal hydride.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A nanofilm-coated modified light metal hydride, wherein the modified light metal hydride has a light metal hydride core and a nanofilm as a surface modification layer.

[0009] The light metal hydrides are lithium hydride (LiH), aluminum hydride (AlH3), magnesium hydride (MgH2), or zirconium hydride (ZrH2).

[0010] The nanofilm is an organic film or an inorganic-organic hybrid film.

[0011] The nanofilm was deposited on the surface of a light metal hydride using molecular layer deposition technology.

[0012] The present invention also has the following technical features:

[0013] Preferably, the organic film is a polyurea film, a polyamide film, a polyimide film, a polyurethane film, a polyethylene terephthalate film, or a polythiourea film.

[0014] Preferably, the inorganic-organic hybrid film is an alkoxyaluminum film, an alkoxyzinc film, an alkoxytitanium film, or an alkoxyzirconium film.

[0015] Specifically, the mass of the nanofilm accounts for 0.1% to 5% of the total mass of the modified light metal hydride.

[0016] Preferably, the mass of the nanofilm accounts for 1% to 3.3% of the total mass of the modified light metal hydride.

[0017] Specifically, the thickness of the nanofilm is 0.01–200 nm.

[0018] Preferably, the thickness of the nanofilm is 10–24 nm.

[0019] Preferably, the particle size of the light metal hydride is in the range of micrometers to nanometers.

[0020] This invention also protects a method for preparing nanofilm-coated modified light metal hydrides as described above, characterized in that the method is carried out according to the following steps:

[0021] Step 1: Load the light metal hydride into the reactor, then load the reactor into the reaction chamber of the molecular layer deposition system, cover the reaction chamber, and evacuate to control the pressure inside the reaction chamber at 1-1000 Pa. At the same time, heat the reaction chamber to keep the temperature between 30°C and 300°C, and the precursor temperature between room temperature and 200°C.

[0022] Step two involves initiating a molecular layer deposition reaction on the surface of a light metal hydride. A single molecular layer deposition reaction includes the following sub-steps:

[0023] Step 201: Inject the first reaction precursor into the reaction chamber to undergo a saturated chemisorption reaction with the surface groups of the light metal hydride for a time of t1.

[0024] Step 202: Inert carrier gas is introduced to remove excess first reaction precursor and reaction byproducts for time t2.

[0025] Step 203: Inject the second type of reaction precursor into the reaction chamber to undergo a surface exchange reaction with the first type of precursor groups adsorbed on the surface of the light metal hydride for a time of t3.

[0026] Step 204: Inert carrier gas is introduced to remove excess of the second reaction precursor and reaction byproducts for time t4.

[0027] Step 3 involves repeating the molecular layer deposition reaction multiple times, i.e., repeating step 2, to form modified light metal hydrides.

[0028] In step 201, the first reaction precursor is adipic acid chloride, terephthaloyl chloride, pyromellitic dianhydride, terephthalaldehyde, terephthalic diisocyanate, 1,4-butanediisocyanate, trimethylaluminum, dimethylzinc, titanium tetrachloride, or tetrabutoxyzirconium.

[0029] In step 203, the second reaction precursor is ethylenediamine, 1,6-hexanediamine, p-phenylenediamine, 4,4'-diaminodiphenyl ether, 4-aminophenol, ethylene glycolamine, ethylene glycol, glycerol, or 1,4-phenylenediol.

[0030] In step two, the inert carrier gas is nitrogen, helium, or argon.

[0031] In step two, the times t1 and t3 are 3–2000 s, and t2 and t4 are 5–4000 s. Preferably, the times t1 and t3 are 5–100 s, and t2 and t4 are 10–120 s.

[0032] In step three, the number of cycles is 1 to 3000. Preferably, the number of cycles is 100 to 400.

[0033] Compared with the prior art, the present invention has the following technical effects:

[0034] (I) The nanofilm of the present invention can completely and uniformly cover the entire outer surface of the light metal hydride particles, and the thickness is precisely adjustable in the nanometer range. Depending on the thickness and density of the film, its content accounts for only 0.1% to 5% of the total mass of the system, and has little impact on the energy of the light metal hydride.

[0035] (II) The nanofilm prepared by this invention has good shape retention and will not change the original morphology of the light metal hydride sample after coating.

[0036] (III) The light metal hydrides coated and modified by the present invention have significantly improved surface hydrophobicity and stability.

[0037] (IV) The preparation method adopted in this invention has a high degree of automation, good repeatability of the preparation process, and simple post-processing. It can achieve surface treatment of samples in the range of grams to kilograms, and is easy to promote and apply in industry.

[0038] (V) The light metal hydrides deposited in this invention exhibit significantly improved surface hydrophobicity and enhanced water-oxygen stability. The modified light metal hydrides of this invention can be widely applied in fuel cells, special energy propulsion (solid propellants and high-energy explosives), and other fields. Attached Figure Description

[0039] Figure 1 XPS spectra of the original aluminum hydride sample and the aluminum hydride sample coated with a polyurea nanofilm for 200 cycles in Example 1.

[0040] Figure 2 The damp heat stability test results are shown for the original aluminum hydride sample and the aluminum hydride sample coated with a polyurea nanofilm for 200 cycles, as described in Exercise 1.

[0041] Figure 3 The images show the SEM spectra of the original aluminum hydride sample and the aluminum hydride sample coated with a polyurea nanofilm for 400 cycles in Example 2.

[0042] Figure 4 The images show the TEM spectra of the original aluminum hydride sample and the aluminum hydride sample coated with a polyurea nanofilm after 400 cycles in Example 2.

[0043] Figure 5 This is a schematic diagram showing the contact angles of the original aluminum hydride sample and the aluminum hydride sample coated with a polyurea nanofilm for 400 cycles in Example 2.

[0044] Figure 6 The images show the damp heat stability test results of the original aluminum hydride sample and the aluminum hydride sample coated with a polyurea nanofilm for 400 cycles in Example 2.

[0045] Figure 7 The images show the thermal stability test results of the original aluminum hydride sample and the aluminum hydride sample coated with a polyurea nanofilm for 400 cycles in Example 2.

[0046] Figure 8 The images show the damp heat stability test results of the original aluminum hydride sample and the aluminum hydride sample coated with alkoxyaluminum nanofilm for 100 cycles in Example 3.

[0047] Figure 9 This is a schematic diagram showing the contact angles of the original magnesium hydride sample and the magnesium hydride sample after being coated with a polyimide nanofilm for 150 cycles in Example 4.

[0048] Figure 10 The figures show the damp heat stability test results of the original magnesium hydride sample and the magnesium hydride sample after being coated with a polyimide nanofilm for 150 cycles in Example 4.

[0049] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0050] It should be noted that, unless otherwise specified, all materials and devices used in this invention are those known in the art.

[0051] In this invention, the molecular layer deposition system is a commonly used known molecular layer deposition system, and the reactor structure of the molecular layer deposition system is a fixed bed type, a rotating bed type, or a fluidized bed type. The mass of the light metal hydride charged in the reactor is 0.1 to 1000 grams.

[0052] The characterization instruments and equipment used in this invention include X-ray photoelectron spectroscopy (Thermo Scientific K-Alpha XPS), scanning electron microscope (FEIQuanta 600FEG SEM), field emission transmission electron microscope (FEITecnai G2 F20S-TWIN), contact angle tester, constant temperature test chamber, and PCT curve tester.

[0053] In this invention, the number-average molecular weight of the polymers selected for the organic thin film varies with the number of deposition cycles in the molecular layer deposition process, and the preferred value of the number-average molecular weight is a number-average molecular weight in the range of 200 to 400 deposition cycles.

[0054] The number average molecular weight of polyurea is 2,000 to 180,000, with a preferred value of 80,000.

[0055] The number average molecular weight of the polyamide is 2,000 to 90,000, with a preferred value of 45,000.

[0056] The number average molecular weight of polyimide is 2800 to 120000, with a preferred value of 60000.

[0057] The number average molecular weight of polyurethane is 2200 to 220000, with a preferred value of 85000.

[0058] The number average molecular weight of polyethylene terephthalate is 2,000 to 100,000, with a preferred value of 40,000.

[0059] The number average molecular weight of polythiourea is 2,500 to 200,000, with a preferred value of 100,000.

[0060] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0061] Example 1:

[0062] This embodiment provides a nanofilm-coated modified light metal hydride and its preparation method, which is carried out according to the following steps:

[0063] Step 1: Load 1 gram of aluminum hydride sample into a fixed-bed reactor, then load the reactor into the reaction chamber of the molecular layer deposition system, cover the reaction chamber, and evacuate to control the pressure inside the reaction chamber at 100 Pa. At the same time, heat the reaction chamber to a temperature of 75°C, while the precursor p-phenylenediamine is at 50°C and ethylenediamine is at 30°C.

[0064] Step two involves initiating a molecular layer deposition reaction on the surface of the aluminum hydride sample. A single molecular layer deposition reaction includes the following sub-steps:

[0065] Step 201: Inject the first reaction precursor, terephthalic diisocyanate, into the reaction chamber to undergo a saturated chemisorption reaction with the surface groups of aluminum hydride for 5 seconds.

[0066] Step 202: Inert carrier gas nitrogen is introduced to remove excess first reaction precursor and reaction byproducts for 10 seconds.

[0067] Step 203: Inject the second reaction precursor, ethylenediamine, into the reaction chamber to undergo a surface exchange reaction with the first precursor groups adsorbed on the surface of aluminum hydride for 5 seconds.

[0068] Step 204: Inert carrier gas nitrogen is introduced to remove excess second reaction precursor and reaction byproducts for 10 seconds.

[0069] Step 3 involves 200 cycles of molecular layer deposition reaction, which is to repeat step 2 200 times to form modified aluminum hydride with aluminum hydride as the core and a polyurea film of about 12 nanometers as the surface modification layer, wherein the mass ratio of the coating film is 1.52%.

[0070] Figure 1 XPS test results showed that after 200 cycles of polyurea nanofilm coating, the Al signal on the surface of aluminum hydride completely disappeared and the N signal was significantly enhanced, indicating that the polyurea nanofilm of only about 12 nm achieved complete and uniform coating of the aluminum hydride sample.

[0071] Figure 2 The results of the damp heat stability test showed that under extreme temperature and humidity conditions of 35℃ and 95% humidity, compared with the uncoated aluminum trihydride original sample, the aluminum trihydride sample coated with polyurea nanofilm had a moisture absorption weight gain rate of only 3.6% after 15 days of storage, which was much smaller than the 11.1% of the original sample. This further illustrates the excellent water and oxygen barrier properties of polyurea nanofilm.

[0072] Example 2:

[0073] This embodiment provides a nanofilm-coated modified light metal hydride and its preparation method, the specific steps of which are as follows:

[0074] Step 1: Load 10 grams of aluminum hydride sample into a rotating bed reactor, then load the reactor into the reaction chamber of the molecular layer deposition system, cover the reaction chamber, and evacuate to control the pressure inside the reaction chamber at 80 Pa. At the same time, heat the reaction chamber to a temperature of 75°C, while the precursor p-phenylenedicyanate is at 50°C and ethylenediamine is at 30°C.

[0075] Step two involves initiating a molecular layer deposition reaction on the surface of the aluminum hydride sample. A single molecular layer deposition reaction includes the following sub-steps:

[0076] Step 201: The first reaction precursor, terephthalic diisocyanate, is injected into the reaction chamber to undergo a saturated chemisorption reaction with the surface groups of aluminum hydride for 20 seconds.

[0077] Step 202: Inert carrier gas argon is introduced to remove excess first reaction precursor and reaction byproducts for 30 seconds.

[0078] Step 203: Inject the second reaction precursor, ethylenediamine, into the reaction chamber to undergo a surface exchange reaction with the first precursor groups adsorbed on the aluminum hydride surface for 20 seconds.

[0079] Step 204: Inert carrier gas argon is introduced to remove excess second reaction precursor and reaction byproducts for 30 seconds.

[0080] Step 3 involves 400 cycles of molecular layer deposition reaction, which is to repeat step 2 400 times to form modified aluminum hydride with aluminum hydride as the core and a polyurea film of about 24 nanometers as the surface modification layer, wherein the mass ratio of the coating film is 2.98%.

[0081] Figure 3 SEM results showed that the morphology of aluminum hydride particles coated with polyurea nanofilms for 400 cycles remained intact and was basically consistent with that of untreated aluminum hydride particles. This indicates that polyurea nanofilms can grow uniformly on the surface of aluminum hydride samples, and the nanoscale coating layer does not change the original morphology of the aluminum hydride particles.

[0082] Figure 4 TEM results showed that the thickness of the polyurea nanofilm coated on the aluminum hydride surface was approximately 24 nm, and the average growth rate of the coating on the aluminum hydride surface was 0.06 nm / cycle.

[0083] Figure 5 The contact angle test results show that the surface hydrophobicity of the polyurea-coated aluminum hydride sample is significantly improved, with the contact angle increasing from 32° to 113°.

[0084] Figure 6The results of the damp heat stability test showed that under extreme temperature and humidity conditions of 35℃ and 95% humidity, compared with the uncoated aluminum trihydride original sample, the aluminum trihydride sample coated with polyurea nanofilm had a moisture absorption weight gain rate of only 2.74% after 15 days of storage, which was much smaller than the 11.1% of the original sample. This further illustrates the excellent water and oxygen barrier properties of polyurea nanofilm.

[0085] Figure 7 The thermal stability characterization experiment was carried out under vacuum conditions at 100℃. As shown in the figure, within the same time period, the hydrogen release pressure of the aluminum hydride sample coated with polyurea nanofilm was significantly lower than that of the original sample, indicating that the thermal stability of the sample modified by polyurea nanofilm coating was significantly higher than that of the original aluminum hydride sample.

[0086] Example 3:

[0087] This embodiment provides a nanofilm-coated modified light metal hydride and its preparation method, the specific steps of which are as follows:

[0088] Step 1: Load 500g of aluminum hydride sample into a rotating bed reactor, then load the reactor into the reaction chamber of the molecular layer deposition system, cover the reaction chamber, and evacuate to control the pressure inside the reaction chamber at 133Pa. At the same time, heat the reaction chamber to maintain the temperature at 70℃, while the precursors trimethylaluminum and ethylene glycol are maintained at 25℃.

[0089] Step two involves initiating a molecular layer deposition reaction on the surface of the aluminum hydride sample. A single molecular layer deposition reaction includes the following sub-steps:

[0090] Step 201: The first reaction precursor, trimethylaluminum, is injected into the reaction chamber to undergo a saturated chemisorption reaction with the surface groups of aluminum hydride for 90 seconds.

[0091] Step 202: Inert carrier gas argon is introduced to remove excess first reaction precursor and reaction byproducts for 120 seconds.

[0092] Step 203: Inject the second reaction precursor, ethylene glycol, into the reaction chamber to undergo a surface exchange reaction with the first precursor groups adsorbed on the aluminum hydride surface for 100 seconds.

[0093] Step 204: Inert carrier gas argon is introduced to remove excess second reaction precursor and reaction byproducts for 120 seconds.

[0094] Step 3 involves 100 cycles of molecular layer deposition reaction, which is to repeat step 2 100 times to form modified aluminum hydride with aluminum hydride as the core and an approximately 11-nanometer alkoxy aluminum film as the surface modification layer, wherein the coating film accounts for 3.3% of the total mass.

[0095] Figure 8 The results of the damp heat stability test showed that under extreme temperature and humidity conditions of 35℃ and 95% humidity, compared with the uncoated aluminum trihydride original sample, the aluminum hydride sample coated with alkoxy aluminum nanofilm had a moisture absorption weight gain rate of only 3.44% after 15 days of storage, which was much smaller than the 11.1% of the original sample. This further illustrates the excellent water and oxygen barrier properties of alkoxy aluminum nanofilm.

[0096] Example 4:

[0097] This embodiment provides a nanofilm-coated modified light metal hydride and its preparation method, the specific steps of which are as follows:

[0098] Step 1: Load 10 grams of magnesium hydride sample into a fluidized bed reactor, then load the reactor into the reaction chamber of the molecular layer deposition system, cover the reaction chamber, and evacuate to control the pressure inside the reaction chamber at 500 Pa. At the same time, heat the reaction chamber to maintain the temperature at 160 °C, the precursor pyromellitic dianhydride at 150 °C, and ethylenediamine at 25 °C.

[0099] Step two involves initiating a molecular layer deposition reaction on the surface of the magnesium hydride sample. A single molecular layer deposition reaction includes the following sub-steps:

[0100] Step 201: The first reaction precursor, pyromellitic dianhydride, is injected into the reaction chamber to undergo a saturated chemisorption reaction with the surface groups of magnesium hydride for 60 seconds.

[0101] Step 202: Inert carrier gas argon is introduced to remove excess first reaction precursor and reaction byproducts for 80 seconds.

[0102] Step 203: Inject the second reaction precursor, ethylenediamine, into the reaction chamber to undergo a surface exchange reaction with the first precursor groups adsorbed on the magnesium hydride surface for 50 seconds.

[0103] Step 204: Inert carrier gas argon is introduced to remove excess second reaction precursor and reaction byproducts for 80 seconds.

[0104] Step 3 involves 150 cycles of molecular layer deposition reaction, which is to repeat step 2 150 times to form modified magnesium hydride with aluminum hydride as the core and a 10-nanometer polyimide (PI) film as the surface modification layer, wherein the mass ratio of the coating film is 1%.

[0105] Figure 9 The contact angle test results show that the surface hydrophobicity of the magnesium hydride sample modified by polyimide coating is significantly improved, with the contact angle jumping from 30° to 95°.

[0106] Figure 10The results of the damp heat stability test showed that, under the temperature and humidity conditions of 30℃ and 80% humidity, compared with the uncoated original magnesium hydride sample, the PI nanofilm-coated magnesium hydride sample had a moisture absorption weight gain rate of only 3.7% after 8 days of storage, which was much smaller than the 58% of the original sample. This further illustrates the excellent water and oxygen barrier properties of the PI nanofilm.

[0107] The above embodiments further illustrate the purpose, technical solution, and advantages of the present invention in detail. It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0108] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0109] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content invented by this disclosure.

Claims

1. A method for preparing a nanosheet-coated modified light metal hydride, characterized by, The modified light metal hydride has a light metal hydride core and a nanofilm as a surface modification layer; The light metal hydride is lithium hydride, aluminum hydride, magnesium hydride or zirconium hydride; The nanofilm is an organic film or an inorganic-organic hybrid film; The nanofilm was deposited on the surface of a light metal hydride using molecular layer deposition technology; This method is performed according to the following steps: Step 1: Load the light metal hydride into the reactor, then load the reactor into the reaction chamber of the molecular layer deposition system, cover the reaction chamber, and evacuate to control the pressure in the reaction chamber at 1-1000 Pa. At the same time, heat the reaction chamber to keep the temperature at 30℃-300℃ and the precursor temperature at room temperature-200℃. Step two: Initiate a molecular layer deposition reaction on the surface of the light metal hydride. A single molecular layer deposition reaction includes the following sub-steps: Step 201: Inject the first reaction precursor into the reaction chamber to undergo a saturated chemisorption reaction with the surface groups of the light metal hydride for a time of t1. Step 202: Inert carrier gas is introduced to remove excess first reaction precursor and reaction byproducts for time t2; Step 203: Inject the second type of reaction precursor into the reaction chamber to undergo a surface exchange reaction with the first type of precursor groups adsorbed on the surface of the light metal hydride for a time of t3. Step 204: Inert carrier gas is introduced to remove excess of the second reaction precursor and reaction byproducts for time t4. Step 3: Repeat the molecular layer deposition reaction multiple times, that is, repeat step 2 to form modified light metal hydrides.

2. The method of claim 1, wherein the nanocoating is applied by a process selected from the group consisting of: physical vapor deposition, chemical vapor deposition, atomic layer deposition, and combinations thereof. The organic film is a polyurea film, a polyamide film, a polyimide film, a polyurethane film, a polyethylene terephthalate film, or a polythiourea film; The inorganic-organic hybrid film is an alkoxyaluminum film, an alkoxyzinc film, an alkoxytitanium film, or an alkoxyzirconium film.

3. The method of claim 1, wherein the nanocoating is applied by a process selected from the group consisting of: physical vapor deposition, chemical vapor deposition, atomic layer deposition, and combinations thereof. The mass of the nanofilm accounts for 0.1% to 5% of the total mass of the modified light metal hydride.

4. The method for preparing nanofilm-coated modified light metal hydrides as described in claim 1, characterized in that, The mass of the nanofilm accounts for 1% to 3.3% of the total mass of the modified light metal hydride.

5. The method for preparing nanofilm-coated modified light metal hydrides as described in claim 1, characterized in that, The thickness of the nanofilm is 0.01–200 nm.

6. The method for preparing nanofilm-coated modified light metal hydrides as described in claim 3, characterized in that, The thickness of the nanofilm is 10–24 nm.

7. The method for preparing nanofilm-coated modified light metal hydrides as described in claim 1, characterized in that, The particle size of the light metal hydride is in the range of micrometers to nanometers.

8. The method for preparing nanofilm-coated modified light metal hydrides as described in claim 1, characterized in that, In step 201, the first reaction precursor is adipic acid chloride, terephthaloyl chloride, pyromellitic dianhydride, terephthalaldehyde, terephthalic diisocyanate, 1,4-butanediisocyanate, trimethylaluminum, dimethylzinc, titanium tetrachloride, or tetrabutoxyzirconium. In step 203, the second reaction precursor is ethylenediamine, 1,6-hexanediamine, p-phenylenediamine, 4,4'-diaminodiphenyl ether, 4-aminophenol, ethylene glycolamine, ethylene glycol, glycerol, or 1,4-phenylenediol.

9. The method for preparing nanofilm-coated modified light metal hydrides as described in claim 1, characterized in that, In step two, the inert carrier gas is nitrogen, helium, or argon. In step two, the time intervals t1 and t3 are 3–2000 s, and t2 and t4 are 5–4000 s. In step three, the number of cycles is 1-3000.

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