CN108520946B - Magnesium-iron hydride-graphite composite electrode material and preparation method and application thereof - Google Patents
Magnesium-iron hydride-graphite composite electrode material and preparation method and application thereof Download PDFInfo
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Abstract
The invention belongs to the field of electrode materials, and discloses a magnesium-iron hydride-graphite composite electrode material, and a preparation method and application thereof. Mixing magnesium powder and iron powder, carrying out ball milling in a hydrogen atmosphere, carrying out heat treatment at 400-500 ℃, and carrying out ball milling with graphite in the hydrogen atmosphere to obtain Mg2FeH6-a graphite composite material; mixing Mg2FeH6And uniformly mixing the graphite composite material, a conductive agent and a binder, coating the mixture on a copper foil to prepare an electrode plate, drying the electrode plate in vacuum, and preparing a metal oxide protective film on the surface of the electrode plate through magnetron sputtering to obtain the magnesium-iron hydride-graphite composite electrode material. The invention adopts a method of combining multiphase composite ball milling and magnetron sputtering, can improve the reversibility of the electrode and improve the cycle performance of the electrode.
Description
Technical Field
The invention belongs to the field of electrode materials, and particularly relates to a magnesium-iron hydride-graphite composite electrode material as well as a preparation method and application thereof.
Background
As a novel energy storage device, the lithium ion battery has the advantages of high voltage, high specific energy, low self-discharge, good cycle performance, no memory effect, environmental protection and the like, and is a high-efficiency secondary battery with the greatest development prospect and a chemical energy storage power source with the fastest development at present. With the development of strategic emerging industries such as information technology, power automobiles, aerospace and the like, higher requirements are put forward on the energy density and the safety performance of the lithium ion battery. However, due to the defects of low quality and volume specific capacity of the existing electrode materials, the commercialized lithium electronic battery cannot meet the application requirements in the fields. Therefore, the improvement of performance of new lithium ion batteries will be mainly dependent on the development of high specific capacity electrode material systems.
Magnesium has the advantages of rich raw materials, low price, light weight, small environmental pollution and the like, and compared with the commercialized graphite cathode, the magnesium hydride has higher storage capacity. Such as MgH2The negative electrode has 2038mAh g-1And the charge-discharge hysteresis effect of the magnesium hydride negative electrode is obviously lower than that of other compound conversion negative electrode materials. If the magnesium-based metal hydride cathode can be practically applied, the specific capacity and the energy density of the lithium ion battery system can be greatly improved. However, during lithium storage, the conversion reaction of the metal hydride with lithium ions produces a large volume change, making the hydride electrode completely ineffective after several charge-discharge cycles. In addition, the development of such batteries has been limited by the problem of the sensitivity of magnesium-based metal hydrides to water oxygen in the environment.
Aiming at the problems of poor cycle stability and poor conductivity of magnesium hydride cathode materials, the composite material of magnesium hydride and graphite or other metals is mainly prepared by a ball milling process at present. The nano composite structure formed by ball milling obviously promotes the conversion reaction of magnesium hydride and lithium ions, and can relieve the volume expansion effect to a certain extent and improve the cycle life. However, the reversibility of the magnesium hydride conversion reaction is still poor and the activity of the hydride substantially disappears after more than twenty cycles. On the one hand, this is related to the ease of forming a passivation layer on the magnesium surface to prevent the formation of magnesium hydride; on the other hand, the magnesium particles are agglomerated and grown in the circulation process, so that the active substances and the current collector lose contact.
Disclosure of Invention
Aiming at the defects and shortcomings of the prior art, the invention mainly aims to provide a preparation method of a magnesium-iron hydride-graphite composite electrode material.
The invention also aims to provide the magnesium-iron hydride-graphite composite electrode material prepared by the method.
The invention further aims to provide the application of the magnesium-iron hydride-graphite composite electrode material as a negative electrode of a lithium ion battery.
The purpose of the invention is realized by the following technical scheme:
a preparation method of a magnesium-iron hydride-graphite composite electrode material comprises the following preparation steps:
(1) mixing magnesium powder and iron powder, and carrying out ball milling in a hydrogen atmosphere;
(2) heating the powder obtained in the step (1) to 400-500 ℃ in a hydrogen atmosphere for heat treatment to obtain Mg2FeH6Powder;
(3) mg obtained in the step (2)2FeH6Ball milling the powder and graphite in hydrogen atmosphere to obtain Mg2FeH6-a graphite composite material;
(4) mg obtained in the step (3)2FeH6The graphite composite material, a conductive agent and a binder are uniformly mixed and coated on a copper foil to prepare an electrode slice, and the electrode slice is dried in vacuum;
(5) and (4) preparing a metal oxide protective film on the surface of the electrode slice obtained in the step (4) through magnetron sputtering to obtain the magnesium-iron hydride-graphite composite electrode material.
Preferably, the purity of the magnesium powder and the iron powder in the step (1) is more than or equal to 99 percent; the mass ratio of the magnesium powder to the iron powder is (2.0-3.0): 1.
Preferably, the ball milling in the step (1) and the step (3) is carried out in a planetary ball mill, the ball-material ratio of the ball milling is (40-60): 1, the ball milling time is 10-20 h, and the ball milling rotating speed is 500 r/min.
Preferably, the pressure of the hydrogen atmosphere in the step (1) and the step (3) is 1-6 MPa.
Preferably, the pressure of the hydrogen atmosphere in the step (2) is 2-8 MPa; the time of the heat treatment is 20 h.
Preferably, the processes of sample loading, powder taking and electrode plate preparation are all carried out in an argon atmosphere glove box and are kept isolated from air.
Preferably, the added mass of graphite in step (3) is Mg2FeH610-50% of the composite material.
Preferably, the conductive agent in step (4) is selected from Super-P conductive agents, and the binder is selected from PVDF.
Preferably, the step (5) of preparing the metal oxide protective film by magnetron sputtering comprises the following steps: the electrode plate is placed in a magnetron sputtering cavity, a metal oxide target material is installed in the magnetron sputtering cavity, then the magnetron sputtering cavity is vacuumized to the background, argon is introduced to adjust the air pressure in the sputtering cavity, and a metal oxide protective film is prepared on the surface of the electrode plate through magnetron sputtering.
Preferably, the metal oxide in step (5) is TiO2(ii) a The magnetron sputtering conditions are as follows: background vacuum degree lower than 10-3Pa, the air pressure in the sputtering cavity is 0.4-1 Pa, the sputtering power is 100W, and the sputtering time is 10-60 min.
A magnesium-iron hydride-graphite composite electrode material is prepared by the method.
Preferably, the metal oxide protective film of the magnesium-iron hydride-graphite composite electrode material is a titanium oxide film, and the atomic ratio of titanium oxygen atoms in the titanium oxide film is 1 (1-1.6).
The magnesium-iron hydride-graphite composite electrode material is applied as a negative electrode of a lithium ion battery.
The principle of the invention is as follows: preparation of Mg by the invention2FeH6Composite negative electrode material with graphite, Mg2FeH6The conversion reaction is decomposed in situ to form Mg and Fe nano particles, the nano Mg particles have high electrochemical activity, and the Fe particles can effectively prevent the magnesium particles from agglomerating, enhance the conductivity of the hydride and promote the conversion reaction. The graphite can effectively relieve the volume expansion of the magnesium hydride conversion reaction. Furthermore, in Mg2FeH6The titanium oxide film is sputtered on the surface of the electrode plate made of the graphite composite material, so that the direct contact between the hydride material and the electrolyte is avoided, and the occurrence of side reactions is reducedAnd the method has a remarkable improvement effect on the cycle stability of the hydride cathode material.
The preparation method and the obtained product have the following advantages and beneficial effects:
(1) the invention provides a method for preparing Mg with higher yield by combining a reaction ball milling method and a heat treatment method2FeH6An economical process. Mg and Fe powder are traditionally used as raw materials to prepare Mg by simple methods such as powder sintering or reaction ball milling2FeH6The energy consumption is high, the synthesis yield is only about 65 percent generally, and the yield of the method can reach 95.4 percent.
(2) The invention adopts a method of combining multiphase composite ball milling and magnetron sputtering, and the addition of graphite can obviously improve and effectively prevent the agglomeration of nano particles, improve the conductivity of the material and relieve the volume expansion of the material. The modified layer of surface titanium oxide can prevent the active material from directly contacting with the electrolyte, and the combination of the two can improve the reversibility of the electrode and improve the cycle performance of the electrode.
(3) The magnesium-iron hydride-graphite composite electrode material obtained by the invention can be used as a lithium ion battery cathode material, and has very high theoretical capacity (1456mAh g) compared with a graphite cathode applied commercially-1) It is important to meet the increasing capacity demand.
(4) The preparation process and equipment of the invention are simple and easy to implement, the required raw materials are easy to obtain, the technical process is simple, the reaction is controllable, the cost is low, and the industrialization and the marketization are facilitated.
Drawings
FIG. 1 shows Mg obtained after the heat treatment of step (2) of example 12FeH6XRD patterns of the powder (a), the electrode sheet (b) obtained in the step (4) and the magnesium-iron hydride-graphite composite electrode material (c) obtained in the step (5).
Fig. 2 is an energy spectrum diagram of the magnesium iron hydride-graphite composite electrode material obtained in example 1.
FIG. 3 is a graph showing the cycle performance of the magnesium-iron hydride-graphite composite electrode material obtained in examples 1 to 2 of the present invention.
FIG. 4 is a graph showing the cycle performance of the magnesium-iron hydride-graphite composite electrode material obtained in examples 3 to 5 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Example 1
(1) In a glove box with 0.1MPa of argon atmosphere, magnesium powder and iron powder (the purity is not lower than 99 wt.%) are loaded into a ball milling tank according to the mass ratio of 2.2:1, the ball milling tank is placed in a high-energy planetary ball mill (QM-3SP4), 6MPa of hydrogen is introduced, ball-material ratio is 40:1, ball milling rotation speed is 500 revolutions per minute, operation is carried out for 15 minutes and stopping for 15 minutes, and ball milling is carried out for 20 hours in the hydrogen atmosphere.
(2) After the ball milling is finished, powder is taken out in an argon atmosphere glove box, the powder is transferred into a high-pressure reaction kettle, 9MPa hydrogen is introduced, the temperature is increased to 450 ℃ at the heating rate of 5K/min, the temperature is kept for 20 hours, and Mg is obtained2FeH6And (3) powder.
(3) Mg obtained in the step (2)2FeH6Putting the powder and graphite into a ball milling tank according to the mass ratio of 9:1, putting the ball milling tank into a high-energy planetary ball mill (QM-3SP4), introducing 6MPa hydrogen, alternately performing ball milling for 15 minutes and stopping for 15 minutes at the ball-material ratio of 40:1 and the ball milling rotation speed of 500r/min, and performing ball milling for 10 hours in a hydrogen atmosphere to obtain Mg2FeH6-a graphite composite material.
(4) Mg obtained in the step (3)2FeH6The graphite composite material, a conductive agent (Super-P) and a binder (PVDF) are uniformly mixed according to the mass ratio of 8:1:1, coated on a copper foil to manufacture an electrode plate, and dried in vacuum.
(5) Placing the electrode slice obtained in the step (4) into a magnetron sputtering cavity, and installing TiO in the magnetron sputtering cavity2Target material, then making the vacuum degree of the cavity be 10-3And introducing argon with the purity of 99.99 percent, adjusting the air pressure in the sputtering cavity to be 0.5Pa, and sputtering for 15min at the sputtering power of 100W to obtain the magnesium-iron hydride-graphite composite electrode material.
This example is Mg obtained after the heat treatment of step (2)2FeH6XRD patterns of the powder (a), the electrode sheet (b) obtained in the step (4) and the magnesium-iron hydride-graphite composite electrode material (c) obtained in the step (5) are shown in figure 1. The energy spectrum of the magnesium iron hydride-graphite composite electrode material obtained in the step (5) is shown in fig. 2. From Mg2FeH6The diffraction peak of iron was substantially absent as seen in the powder XRD pattern, thereby indicating that the reaction had substantially completed and relatively pure Mg was obtained2FeH6. The XRD pattern of the electrode plate shows that Mg is contained in the electrode plate during the preparation process2FeH6And does not react with the conductive agent and the binder. No TiO is detected from the XRD pattern of the magnesium-iron hydride-graphite composite electrode material2However, the presence of Ti element was observed from the energy spectrum of FIG. 2, indicating that TiO was formed on the surface2An amorphous film.
The application performance test of the magnesium-iron hydride-graphite composite electrode material as the negative electrode of the lithium ion battery in the embodiment is as follows:
in an argon atmosphere glove box, metallic lithium is used as a counter electrode, and Ethylene Carbonate (EC) + dimethyl carbonate (DMC) +1MLiPF6And (4) assembling the electrolyte into a button cell for testing. The test conditions were: the charge-discharge current density is 100mA g-1The cutoff voltage of charge and discharge is 0.01V-3V (vs. Li)+/Li)。
The cycle performance obtained by the test is shown in FIG. 3, and pure Mg can be obtained from FIG. 32FeH6Only 38.2mAh g after 50 charge-discharge cycles-1The first reversible capacity of the mg-fe hydride-graphite composite electrode material prepared in this example is 432.7mAh g-1The discharge capacity after 100 cycles was kept at 189.0mAh g-1And the reversibility and the circulation stability of the material are obviously improved.
Example 2
(1) In a glove box with 0.1MPa of argon atmosphere, magnesium powder and iron powder (the purity is not lower than 99 wt.%) are loaded into a ball milling tank according to the mass ratio of 2.2:1, the ball milling tank is placed in a high-energy planetary ball mill (QM-3SP4), 6MPa of hydrogen is introduced, ball-material ratio is 40:1, ball milling rotation speed is 500 revolutions per minute, operation is carried out for 15 minutes and stopping for 15 minutes, and ball milling is carried out for 20 hours in the hydrogen atmosphere.
(2) After the ball milling is finished, powder is taken out in an argon atmosphere glove box, the powder is transferred into a high-pressure reaction kettle, 9MPa hydrogen is introduced, the temperature is increased to 450 ℃ at the heating rate of 5K/min, the temperature is kept for 20 hours, and Mg is obtained2FeH6And (3) powder.
(3) Mg obtained in the step (2)2FeH6Putting the powder and graphite into a ball-milling tank according to the mass ratio of 8.5:1.5, putting the ball-milling tank into a high-energy planetary ball mill (QM-3SP4), introducing 6MPa hydrogen, alternately performing operation for 15 minutes and stopping for 15 minutes at a ball-material ratio of 40:1 and a ball-milling rotating speed of 500 revolutions per minute, and performing ball milling for 10 hours in a hydrogen atmosphere to obtain Mg2FeH6-a graphite composite material.
(4) Mg obtained in the step (3)2FeH6The graphite composite material, a conductive agent (Super-P) and a binder (PVDF) are uniformly mixed according to the mass ratio of 8:1:1, coated on a copper foil to manufacture an electrode plate, and dried in vacuum.
(5) Placing the electrode slice obtained in the step (4) into a magnetron sputtering cavity, and installing TiO in the magnetron sputtering cavity2Target material, then making the vacuum degree of the cavity be 10-3And introducing argon with the purity of 99.99 percent, adjusting the air pressure in the sputtering cavity to be 0.5Pa, and sputtering for 15min at the sputtering power of 100W to obtain the magnesium-iron hydride-graphite composite electrode material.
The application performance test of the magnesium-iron hydride-graphite composite electrode material as the negative electrode of the lithium ion battery in the embodiment is as follows:
in an argon atmosphere glove box, metallic lithium is used as a counter electrode, and Ethylene Carbonate (EC) + dimethyl carbonate (DMC) +1MLiPF6And (4) assembling the electrolyte into a button cell for testing. The test conditions were: the charge-discharge current density is 100mA g-1The cutoff voltage of charge and discharge is 0.01V-3V (vs. Li)+/Li)。
The obtained cycle performance graph is shown in fig. 3, and the first reversible capacity of the magnesium-iron hydride-graphite composite electrode material prepared in the embodiment is 597.5mAh g-1And retention of discharge capacity after 100 cyclesAt 341.0mAhg-1And the reversibility and the circulation stability of the material are obviously improved.
Example 3
(1) In a glove box with 0.1MPa of argon atmosphere, magnesium powder and iron powder (the purity is not lower than 99 wt.%) are loaded into a ball milling tank according to the mass ratio of 2.2:1, the ball milling tank is placed in a high-energy planetary ball mill (QM-3SP4), 6MPa of hydrogen is introduced, ball-material ratio is 40:1, ball milling rotation speed is 500 revolutions per minute, operation is carried out for 15 minutes and stopping for 15 minutes, and ball milling is carried out for 20 hours in the hydrogen atmosphere.
(2) After the ball milling is finished, powder is taken out in an argon atmosphere glove box, the powder is transferred into a high-pressure reaction kettle, 9MPa hydrogen is introduced, the temperature is increased to 450 ℃ at the heating rate of 5K/min, the temperature is kept for 20 hours, and Mg is obtained2FeH6And (3) powder.
(3) Mg obtained in the step (2)2FeH6Putting the powder and graphite into a ball milling tank according to the mass ratio of 8:2, putting the ball milling tank into a high-energy planetary ball mill (QM-3SP4), introducing 6MPa hydrogen, alternately performing ball milling for 15 minutes and stopping for 15 minutes at the ball-material ratio of 40:1 and the ball milling rotation speed of 500r/min, and performing ball milling for 10 hours in a hydrogen atmosphere to obtain Mg2FeH6-a graphite composite material.
(4) Mg obtained in the step (3)2FeH6Uniformly mixing the graphite composite material, a conductive agent (Super-P) and a binder (PVDF) according to a mass ratio of 8:1:1, coating the mixture on a copper foil to prepare an electrode plate, and performing vacuum drying;
(5) placing the electrode slice obtained in the step (4) into a magnetron sputtering cavity, and installing TiO in the magnetron sputtering cavity2Target material, then making the vacuum degree of the cavity be 10-3And introducing argon with the purity of 99.99 percent, adjusting the air pressure in the sputtering cavity to be 0.5Pa, and sputtering for 15min at the sputtering power of 100W to obtain the magnesium-iron hydride-graphite composite electrode material.
The application performance test of the magnesium-iron hydride-graphite composite electrode material as the negative electrode of the lithium ion battery in the embodiment is as follows:
in an argon atmosphere glove box, metallic lithium is used as a counter electrode, and Ethylene Carbonate (EC) + dimethyl carbonate (DMC) +1MLiPF6And (4) assembling the electrolyte into a button cell for testing. The test conditions were: the charge-discharge current density is 100mA g-1The cutoff voltage of charge and discharge is 0.01V-3V (vs. Li)+/Li)。
The obtained cycle performance graph is shown in fig. 4, and the first reversible capacity of the magnesium-iron hydride-graphite composite electrode material prepared in the embodiment is 515.6mAh g-1And the discharge capacity after 100 cycles is kept at 411.8mAhg-1And the reversibility and the circulation stability of the material are obviously improved.
Example 4
(1) In a glove box with 0.1MPa of argon atmosphere, filling magnesium powder and iron powder (the purity is not lower than 99 wt.%) into a ball milling tank according to the mass ratio of 2.2:1, placing the ball milling tank into a high-energy planetary ball mill (QM-3SP4), introducing 6MPa of hydrogen, alternately performing ball milling at the ball-material ratio of 40:1 and the ball milling rotation speed of 500 revolutions per minute for 15 minutes and stopping 15 minutes, and performing ball milling for 20 hours in the hydrogen atmosphere;
(2) after the ball milling is finished, powder is taken out in an argon atmosphere glove box, the powder is transferred into a high-pressure reaction kettle, 9MPa hydrogen is introduced, the temperature is increased to 450 ℃ at the heating rate of 5K/min, the temperature is kept for 20 hours, and Mg is obtained2FeH6And (3) powder.
(3) Mg obtained in the step (2)2FeH6Putting the powder and graphite into a ball milling tank according to the mass ratio of 8:2, putting the ball milling tank into a high-energy planetary ball mill (QM-3SP4), introducing 6MPa hydrogen, alternately performing ball milling for 15 minutes and stopping for 15 minutes at the ball-material ratio of 40:1 and the ball milling rotation speed of 500r/min, and performing ball milling for 10 hours in a hydrogen atmosphere to obtain Mg2FeH6-a graphite composite material.
(4) Mg obtained in the step (3)2FeH6Uniformly mixing the graphite composite material, a conductive agent (Super-P) and a binder (PVDF) according to a mass ratio of 8:1:1, coating the mixture on a copper foil to prepare an electrode plate, and performing vacuum drying;
(5) placing the electrode slice obtained in the step (4) into a magnetron sputtering cavity, and installing TiO in the magnetron sputtering cavity2Target material, then making the vacuum degree of the cavity be 10-3Pa above, introducing argon with the purity of 99.99 percent, and adjusting a sputtering cavityThe internal gas pressure is 0.5Pa, and the magnesium-iron hydride-graphite composite electrode material is obtained by sputtering for 30min with the sputtering power of 100W.
The application performance test of the magnesium-iron hydride-graphite composite electrode material as the negative electrode of the lithium ion battery in the embodiment is as follows:
in an argon atmosphere glove box, metallic lithium is used as a counter electrode, and Ethylene Carbonate (EC) + dimethyl carbonate (DMC) +1MLiPF6And (4) assembling the electrolyte into a button cell for testing. The test conditions were: the charge-discharge current density is 100mA g-1The cutoff voltage of charge and discharge is 0.01V-3V (vs. Li)+/Li)。
The obtained cycle performance graph is shown in figure 4, and the first reversible capacity of the composite material prepared in the embodiment is 515.9mAh g-1The discharge capacity after 100 cycles was maintained at 392.7mAh g-1And the reversibility and the circulation stability of the material are obviously improved.
Example 5
(1) In a glove box with 0.1MPa of argon atmosphere, filling magnesium powder and iron powder (the purity is not lower than 99 wt.%) into a ball milling tank according to the mass ratio of 2.2:1, placing the ball milling tank into a high-energy planetary ball mill (QM-3SP4), introducing 6MPa of hydrogen, alternately performing ball milling at the ball-material ratio of 40:1 and the ball milling rotation speed of 500 revolutions per minute for 15 minutes and stopping 15 minutes, and performing ball milling for 20 hours in the hydrogen atmosphere;
(2) after the ball milling is finished, powder is taken out in an argon atmosphere glove box, the powder is transferred into a high-pressure reaction kettle, 9MPa hydrogen is introduced, the temperature is increased to 450 ℃ at the heating rate of 5K/min, the temperature is kept for 20 hours, and Mg is obtained2FeH6And (3) powder.
(3) Mg obtained in the step (2)2FeH6Putting the powder and graphite into a ball milling tank according to the mass ratio of 8:2, putting the ball milling tank into a high-energy planetary ball mill (QM-3SP4), introducing 6MPa hydrogen, alternately performing ball milling for 15 minutes and stopping for 15 minutes at the ball-material ratio of 40:1 and the ball milling rotation speed of 500r/min, and performing ball milling for 10 hours in a hydrogen atmosphere to obtain Mg2FeH6-a graphite composite material.
(4) Mg obtained in the step (3)2FeH6Graphite composite and conductive agent (Super)-P) and a binder (PVDF) are uniformly mixed according to the mass ratio of 8:1:1 and coated on a copper foil to prepare an electrode slice, and the electrode slice is dried in vacuum;
(5) placing the electrode slice obtained in the step (4) into a magnetron sputtering cavity, and installing TiO in the magnetron sputtering cavity2Target material, then making the vacuum degree of the cavity be 10-3And introducing argon with the purity of 99.99 percent, adjusting the air pressure in the sputtering cavity to be 0.5Pa, and sputtering for 60min at the sputtering power of 100W to obtain the magnesium-iron hydride-graphite composite electrode material.
The application performance test of the magnesium-iron hydride-graphite composite electrode material as the negative electrode of the lithium ion battery in the embodiment is as follows:
in an argon atmosphere glove box, metallic lithium is used as a counter electrode, and Ethylene Carbonate (EC) + dimethyl carbonate (DMC) +1MLiPF6And (4) assembling the electrolyte into a button cell for testing. The test conditions were: the charge-discharge current density is 100mA g-1The cutoff voltage of charge and discharge is 0.01V-3V (vs. Li)+/Li)。
The cycle performance obtained by the test is shown in figure 4, and the first reversible capacity of the composite material prepared in the example is 463.9mAh g-1The discharge capacity after 100 cycles was maintained at 367.8mAh g-1And the reversibility and the circulation stability of the material are obviously improved.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (9)
1. The preparation method of the magnesium-iron hydride-graphite composite electrode material is characterized by comprising the following preparation steps:
(1) mixing magnesium powder and iron powder, and carrying out ball milling in a hydrogen atmosphere;
(2) heating the powder obtained in the step (1) to 400-500 ℃ in a hydrogen atmosphere for heat treatment to obtain Mg2FeH6Powder;
(3) mg obtained in the step (2)2FeH6Ball milling the powder and graphite in hydrogen atmosphere to obtain Mg2FeH6-a graphite composite material;
(4) mg obtained in the step (3)2FeH6The graphite composite material, a conductive agent and a binder are uniformly mixed and coated on a copper foil to prepare an electrode slice, and the electrode slice is dried in vacuum;
(5) and (4) preparing a metal oxide protective film on the surface of the electrode slice obtained in the step (4) through magnetron sputtering to obtain the magnesium-iron hydride-graphite composite electrode material.
2. The method for preparing the magnesium-iron hydride-graphite composite electrode material according to claim 1, wherein the method comprises the following steps: the purity of the magnesium powder and the iron powder in the step (1) is more than or equal to 99 percent; the mass ratio of the magnesium powder to the iron powder is (2.0-3.0): 1.
3. The method for preparing the magnesium-iron hydride-graphite composite electrode material according to claim 1, wherein the method comprises the following steps: and (3) performing ball milling in a planetary ball mill in the steps (1) and (3), wherein the ball-material ratio of the ball milling is (40-60): 1, the ball milling time is 10-20 h, and the ball milling rotating speed is 500 r/min.
4. The method for preparing the magnesium-iron hydride-graphite composite electrode material according to claim 1, wherein the method comprises the following steps: the pressure of the hydrogen atmosphere in the step (1) and the step (3) is 1-6 MPa; and (3) in the step (2), the pressure of the hydrogen atmosphere is 2-8 MPa.
5. The method for preparing the magnesium-iron hydride-graphite composite electrode material according to claim 1, wherein the method comprises the following steps: the graphite in the step (3) is added with Mg2FeH610% -50% of the graphite composite material.
6. The method for preparing the magnesium-iron hydride-graphite composite electrode material according to claim 1, wherein the method comprises the following steps: in the step (4), the conductive agent is selected from a Super-P conductive agent, and the binder is selected from PVDF.
7. The method for preparing the magnesium-iron hydride-graphite composite electrode material according to claim 1, wherein the method comprises the following steps: in the step (5), the metal oxide is TiO2(ii) a The magnetron sputtering conditions are as follows: background vacuum degree lower than 10-3Pa, the air pressure in the sputtering cavity is 0.4-1 Pa, the sputtering power is 100W, and the sputtering time is 10-60 min.
8. A magnesium-iron hydride-graphite composite electrode material is characterized in that: prepared by the method of any one of claims 1 to 7.
9. Use of a magnesium iron hydride-graphite composite electrode material as claimed in claim 8 as a negative electrode for a lithium ion battery.
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