CN111118342B - A2B7 type RE-Sm-Ni series hydrogen storage alloy, negative electrode, battery and preparation method - Google Patents
A2B7 type RE-Sm-Ni series hydrogen storage alloy, negative electrode, battery and preparation method Download PDFInfo
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C19/00—Alloys based on nickel or cobalt
- C22C19/03—Alloys based on nickel or cobalt based on nickel
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- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/02—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working in inert or controlled atmosphere or vacuum
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- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
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Abstract
The invention discloses an A2B7 type RE-Sm-Ni hydrogen storage alloy, a negative electrode, a battery and a preparation method. The hydrogen storage alloy has the following composition: RExSmyNiz‑a‑b‑cMnaAlbMc. RE is selected from one or more elements of La, Ce, Pr, Nd, Y, Gd and Sc; m is selected from one or more elements of Cu, Fe, Co, Sn, V, W, Cr, Zn, Mo and Si; x, y, z, a, b and c represent mole fractions of the elements; x is the number of>0, y is more than or equal to 0.5, and x + y is 6; 22>z≥19；9≥a+b>0; c is more than or equal to 5 and more than or equal to 0; the hydrogen storage alloy does not contain Mg. The hydrogen storage alloy electrode of the present invention requires fewer cycles for complete activation.
Description
Technical Field
The invention relates to a hydrogen storage alloy, a negative electrode, a battery and a preparation method, in particular to a lithium-ion battery A2B7RE-Sm-Ni hydrogen storage alloy, negative electrode, battery and preparation methodThe method is carried out.
Background
The hydrogen storage technology is the key of the application of hydrogen energy to industrialization and scale production. The hydrogen storage alloy material is an important basis for the development of hydrogen storage technology. Among a series of developed hydrogen storage materials, the rare earth hydrogen storage material has excellent dynamic performance and stability, also has higher hydrogen storage capacity, and is widely applied to the aspect of solid hydrogen storage.
The rare earth hydrogen storage material is an important energy conversion material and can be used as a negative electrode material of a nickel-metal hydride (MH-Ni) secondary battery. With the rapid increase of the demand of new energy automobiles, smart grid energy storage and communication base station reserve power supplies on nickel-metal hydride batteries, the market demand of global hydrogen storage materials is rapidly increased, and higher requirements are provided for the comprehensive performance of rare earth hydrogen storage materials. The development of advanced rare earth hydrogen storage materials with excellent properties such as easy activation, high capacity, long life, wide temperature range, low cost and low self-discharge is urgent.
With conventional AB5Compared with hydrogen storage alloy, A of new generation superlattice structure2B7The hydrogen storage alloy has better electrochemical performance and larger hydrogen storage capacity. The existing commercialized superlattice RE-Mg-Ni rare earth hydrogen storage alloy contains volatile and easily-oxidized Mg, so that the composition is difficult to control in the preparation process, and the volatile fine magnesium powder is flammable and explosive, thereby becoming an important problem restricting the development and application of the hydrogen storage alloy.
U.S. patent application US5496424A discloses a hydrogen storage alloy having the following chemical composition: r1-xAx(Ni5-yBy)zR can be La, A can be Sm, B can be Al or Mn, x is 0-0.5, y is 0-1 (excluding 0), and z is 0.8-1.2. The above patent documents only provide a Sm containing hydrogen occluding alloy, La0.8Sm0.2Ni4.8Mn0.2. The lower ratio of Sm to La results in a higher number of cycles required for complete activation of the electrode.
Chinese patent application CN109585790A discloses a hydrogen storage alloy with a chemical composition of La(3.0～3.2) xCexZrySm(1-(4.0～4.2)x-y)NizCouMnvAlw(ii) a x, y, z, u, v and w are molar ratios, and x is more than or equal to 0.14 and less than or equal to 0.17; y is more than or equal to 0.02 and less than or equal to 0.03; z + u + v + w is more than or equal to 4.60 and less than or equal to 5.33; u is more than or equal to 0.10 and less than or equal to 0.20; v is more than or equal to 0.25 and less than or equal to 0.30; w is more than or equal to 0.30 and less than or equal to 0.40. The Sm atomic ratio is 25.6 to 42% of that of the A side. This can improve battery life. In the hydrogen storage alloy, the ratio of Sm to rare earth elements such as La and Ce is less than 1, so that the number of cycles required for complete activation of the electrode is large.
Chinese patent application CN101376941A discloses a hydrogen storage alloy with a chemical composition of LaaM1- aNixCuyFezCouMnvAlwM represents at least two kinds of rare earth metals except lanthanum, and can be Sm, a is 0.4-0.9, x is 2.5-3.6, y is 0.4-1.0, z is 0-0.2, u is 0-0.2 (excluding 0), v is 0.4-0.7, w is 0.2-0.4, and x + y + z + u + v + w is 4.8-5.3. The above patent documents only provide a Sm-containing hydrogen storage alloy La0.6Ce0.2Sm0.1Ni3.3Cu0.7Fe0.1Co0.1Mn0.6Al0.35. The ratio of Sm to rare earth elements such as La and Ce is still low, so that the number of cycles required for complete activation of the electrode is large.
Disclosure of Invention
Accordingly, it is an object of the present invention to provide a hydrogen occluding alloy which requires less cycles for complete activation of an electrode. Furthermore, the hydrogen storage alloy has excellent high-rate discharge performance and small self-discharge. Further, the maximum discharge capacity of the hydrogen occluding alloy of the present invention is large.
It is another object of the present invention to provide a method for producing the above hydrogen occluding alloy, which can obtain a hydrogen occluding alloy requiring less number of cycles for complete activation of an electrode.
It is still another object of the present invention to provide a hydrogen storage alloy negative electrode.
It is yet another object of the present invention to provide a battery.
In one aspect, the present invention provides a hydrogen storage alloy having a composition represented by formula (1):
RExSmyNiz-a-b-cMnaAlbMc (1)
wherein RE is selected from one or more elements of La, Ce, Pr, Nd, Y, Gd and Sc;
wherein M is selected from one or more elements of Cu, Fe, Co, Sn, V, W, Cr, Zn, Mo and Si;
wherein x, y, z, a, b and c represent the mole fraction of each element;
wherein x is greater than 0, y is greater than or equal to 0.5, and x + y is 6; 22> z is more than or equal to 19; 9 is more than or equal to a + b and is more than 0; c is more than or equal to 5 and more than or equal to 0;
wherein the hydrogen storage alloy does not contain Mg.
According to the hydrogen occluding alloy of the present invention, y/x is preferably 1 or more.
According to the hydrogen occluding alloy of the present invention, y/x is preferably 1.6 or more.
According to the hydrogen occluding alloy of the present invention, preferably, 3. gtoreq.x >0.1, 5.9> y. gtoreq.3.5.
According to the hydrogen occluding alloy of the present invention, preferably, 3. gtoreq.a.gtoreq.0, 3. gtoreq.b.gtoreq.0, and a and b are not 0 at the same time.
According to the hydrogen occluding alloy of the present invention, preferably, 5. gtoreq.a + b >0.
According to the hydrogen occluding alloy of the present invention, preferably, the hydrogen occluding alloy has a composition represented by one of the following formulas:
La2Sm4Ni19.4MnAl0.6；
La2Sm4Ni20MnAl0.6；
La2Sm4Ni20Mn；
La2Sm4Ni19.5Mn1.5；
La2Sm4Ni20Al；
La2Sm4Ni19.5Al1.5；
La2Sm4Ni19.5Mn0.5Al；
LaCeSm4Ni19MnAl；
Ml2Sm4Ni19MnAl；
La2Sm4Ni18.4MnAl0.6Cu；
La2Sm4Ni19.1Mn0.3Al0.6Fe；
La1.5Ce0.5Sm4Ni18.4Mn0.5Al0.6Co1.5；
wherein Ml represents lanthanum-rich mischmetal, containing 64 mol% of La, 25 mol% of Ce, 3 mol% of Pr and 8 mol% of Nd.
In another aspect, the present invention provides a method for preparing the above hydrogen storage alloy, comprising the steps of: placing metal raw materials into a vacuum melting furnace according to the sequence of the melting point from large to small and from the bottom to the upper part, placing rare earth elements at the uppermost part, and performing gas washing operation for 2-5 times by using inert gas; vacuumizing the vacuum melting furnace until the absolute vacuum degree is less than or equal to 50Pa, and filling inert gas until the relative vacuum degree is-0.01 to-0.1 MPa; heating a vacuum smelting furnace to 1200-1600 ℃, and stopping heating after the metal raw materials in the furnace are completely melted into molten metal; casting the molten metal to a cooling copper roller, and throwing the sheet into an alloy sheet with the thickness of 0.1-0.4 mm; placing the alloy sheet in an environment with the absolute vacuum degree of 0.0001-0.05 Pa and the protection of inert gas, and carrying out heat treatment for 16-48 h at the temperature of 850-1050 ℃ to obtain a hydrogen storage alloy; the overall composition of the metal feedstock satisfies formula (1).
In still another aspect, the present invention provides a hydrogen storage alloy negative electrode, comprising a current collector and a negative electrode material supported on the current collector; the negative electrode material comprises a negative electrode active substance and a conductive agent, wherein the negative electrode active substance is the hydrogen storage alloy.
In yet another aspect, the present invention provides a battery comprising a battery case, an electrode group, and an alkaline electrolyte; the electrode group and the alkaline electrolyte are sealed in the battery shell; the electrode group comprises a positive electrode, a negative electrode and a diaphragm, wherein the negative electrode is the hydrogen storage alloy negative electrode.
The invention relates to aThe proportion of rare earth elements such as Sm and La is improved, so that the cycle number required by the complete activation of the electrode is reduced. According to the preferred technical scheme of the invention, the high-rate discharge performance and the self-discharge performance are improved by adjusting the molar ratio of elements such as Sm, La, Ni and Mn. In A2B7In the superlattice structure, Sm has an effect of suppressing amorphization due to hydrogen. According to a preferred embodiment of the present invention, the maximum discharge capacity of the hydrogen occluding alloy of the present invention is improved.
Detailed Description
The present invention will be further described with reference to the following specific examples, but the scope of the present invention is not limited thereto.
In the present invention, the number of activation times of the hydrogen absorbing alloy indicates the number of cycles (N) required for complete activation of the hydrogen absorbing alloy electrode. The high-rate discharge capacity HRD of the hydrogen storage alloy is expressed by the percentage of the discharge capacity at the discharge current density of 300mA/g and the discharge capacity at the discharge current density of 60 mA/g. The self-discharge characteristic of the hydrogen storage alloy adopts the capacity retention rate SD of the hydrogen storage alloy electrode after being stored for 72 hours72To indicate.
In the present invention, the absolute vacuum degree indicates the actual pressure in the container. The relative vacuum represents the difference between the vessel pressure and 1 standard atmosphere. The inert gas includes nitrogen or argon, etc.
< Hydrogen occluding alloy >
The hydrogen occluding alloy of the present invention may also be referred to as a hydrogen occluding alloy. The hydrogen storage alloy has a composition represented by formula (1):
RExSmyNiz-a-b-cMnaAlbMc (1)。
the hydrogen occluding alloy of the present invention does not contain Mg, but may contain some inevitable impurities. The hydrogen occluding alloy of the present invention is preferably A2B7And (4) molding. When z is 21, it represents the stoichiometric ratio A2B7Molding; a non-stoichiometric ratio A when z ≠ 212B7And (4) molding.
RE is rare earth element. RE may be selected from one or more elements of La, Ce, Pr, Nd, Y, Gd, and Sc. Preferably, RE must contain La. More preferably, RE is selected from one or more elements of La, Ce, Pr, Nd and Y, but must contain La. Most preferably RE is selected from one or more elements of La, Ce, Pr and Nd, but must contain La. In certain embodiments, RE is La. In other embodiments, RE is La and Ce. In still other embodiments, RE is La, Ce, Pr, and Nd. La is 15 to 100 mol%, preferably 35 to 100 mol%, more preferably 50 to 100 mol%, for example 50 mol% or 100 mol% of the total mole of RE. x represents the mole fraction of RE, or represents the atomic proportion of RE. In the present invention, RE is an essential element, and x >0. Preferably, 3 ≧ x > 0.1. More preferably, 3 ≧ x > 1.
Sm is a rare earth element samarium. y represents a molar fraction of Sm, or an atomic ratio of Sm. In the present invention, Sm is an essential element and y is not less than 0.5. Preferably, 5.9> y.gtoreq.3.5. More preferably, 4 ≧ y ≧ 3.5.
In the invention, y/x is more than or equal to 1; preferably, y/x is greater than or equal to 1.6; more preferably, y/x.gtoreq.2.0; most preferably, 3.0. gtoreq.y/x. gtoreq.2.0. Controlling the molar ratio of RE to Sm within the above range is beneficial to reducing the number of cycles required for complete activation of the electrode. The prior art often teaches that the ratio of rare earth elements such as Sm and La is properly reduced to improve the charge-discharge kinetic performance of the electrode material. The present invention has surprisingly found that the number of cycles required for complete activation of the electrode can be reduced by substantially increasing the ratio of rare earth elements such as Sm to La. According to one embodiment of the present invention, y/x is 2.0. This can reduce the number of cycles required for complete activation of the electrode to one.
In the present invention, x + y is 6. According to one embodiment of the invention, 3 ≧ x >0.1, 5.9> y ≧ 3.5, x + y ═ 6. According to another embodiment of the invention, 3 ≧ x >1, 4 ≧ y ≧ 3.5, x + y ═ 6.
Mn is a metal element manganese. a represents a molar fraction of Mn, or an atomic ratio of Mn. Al is a metal element aluminum. b represents a mole fraction of Al or an atomic ratio of Al. In the present invention, Mn and Al are optional elements, but must contain at least one. In the present invention, 9. gtoreq.a + b >0. Preferably, 3 ≧ a ≧ 0, 3 ≧ b ≧ 0, and a and b are not both 0. More preferably, 5 ≧ a + b >0, and a and b are not both 0.
M may be one or more elements selected from Cu, Fe, Co, Sn, V, W, Cr, Zn, Mo, Si. Preferably, M is selected from one or more elements of Cu, Fe, Co, Cr and Zn. More preferably, M is selected from one or more elements of Cu, Fe, Co. In certain embodiments, M is Cu. In other embodiments, M is Co. In still other embodiments, M is Fe.
c represents a mole fraction of M, or an atomic ratio of M. In the invention, M is an optional element, and c is more than or equal to 5 and more than or equal to 0. Preferably, 3. gtoreq.c.gtoreq.0. More preferably, 1.5. gtoreq.c.gtoreq.0.
Ni is a metal element nickel. z-a-b-c represents the mole fraction of Ni, or the atomic proportion of Ni. In the present invention, Ni is an essential element, 22> z.gtoreq.19. Preferably, 22> z ≧ 20. More preferably, 22> z ≧ 21. According to one embodiment of the invention, z is 21. Controlling the mole fraction of Ni in the above range is advantageous for reducing the number of cycles required for complete activation of the electrode.
In certain embodiments, x >0, y ≧ 0.5, and x + y ═ 6; 22> z is more than or equal to 19; 9 is more than or equal to a + b and is more than 0; c is more than or equal to 5 and more than or equal to 0. Preferably, 3 ≧ x >0.1, 5.9> y ≧ 3.5. More preferably, 3 ≧ x >1, 4 ≧ y ≧ 3.5. According to one embodiment of the invention, 22> z ≧ 19; a is more than or equal to 3 and more than or equal to 0, b is more than or equal to 3 and more than or equal to 0, and a and b are not 0 at the same time. According to another embodiment of the invention, 5 ≧ a + b >0. The invention improves the high-rate discharge performance and the self-discharge performance by adjusting the molar ratio of elements such as Sm, La, Ni and Mn. In addition, the maximum discharge capacity of the hydrogen occluding alloy of the present invention is improved.
In certain embodiments, 2.5. gtoreq.a + b. gtoreq.1.6, preferably 2.0. gtoreq.a + b. gtoreq.1.6. Thus, both high-rate discharge performance and self-discharge performance can be considered, and both the high-rate discharge performance and the self-discharge performance can be kept at a higher level.
In other embodiments, 2.0 ≧ a ≧ 1.0, and b ═ 0; preferably, 1.5 ≧ a ≧ 1.0, and b ≧ 0. Thus, both high-rate discharge performance and self-discharge performance can be considered, and both the high-rate discharge performance and the self-discharge performance can be kept at a higher level.
In yet other embodiments, 2.0 ≧ b ≧ 1.5, and a ═ 0; preferably, b is 1.8 ≧ 1.5, and a is 0. Thus, both high-rate discharge performance and self-discharge performance can be considered, and both the high-rate discharge performance and the self-discharge performance can be kept at a higher level.
Specific examples of the hydrogen occluding alloy of the present invention include, but are not limited to, alloys represented by one of the following formulas:
La2Sm4Ni19.4MnAl0.6；
La2Sm4Ni20MnAl0.6；
La2Sm4Ni20Mn；
La2Sm4Ni19.5Mn1.5；
La2Sm4Ni20Al；
La2Sm4Ni19.5Al1.5；
La2Sm4Ni19.5Mn0.5Al；
LaCeSm4Ni19MnAl；
Ml2Sm4Ni19MnAl；
La2Sm4Ni18.4MnAl0.6Cu；
La2Sm4Ni19.1Mn0.3Al0.6Fe；
La1.5Ce0.5Sm4Ni18.4Mn0.5Al0.6Co1.5；
wherein Ml represents lanthanum-rich mischmetal, containing 64 mol% of La, 25 mol% of Ce, 3 mol% of Pr and 8 mol% of Nd.
According to a preferred embodiment of the present invention, the hydrogen occluding alloy of the present invention has a composition represented by one of the following formulas:
La2Sm4Ni19.4MnAl0.6；
La2Sm4Ni20Mn；
La2Sm4Ni19.5Mn1.5；
La2Sm4Ni19.5Al1.5；
La2Sm4Ni19.5Mn0.5Al；
LaCeSm4Ni19MnAl；
Ml2Sm4Ni19MnAl；
La1.5Ce0.5Sm4Ni18.4Mn0.5Al0.6Co1.5。
< preparation method >
The preparation method of the hydrogen storage alloy comprises a high-temperature smelting casting method, a high-temperature smelting-rapid quenching method, a mechanical alloying method, a powder sintering method, a high-temperature smelting-gas atomization method, a reduction diffusion method, a displacement diffusion method, a combustion synthesis method, a self-propagating high-temperature synthesis method and a chemical method. The texture and properties can be improved by heat treatment.
In order to better improve the performance of the hydrogen storage alloy, metal raw materials are smelted and flapped to form an alloy sheet, and then the alloy sheet is subjected to heat treatment to obtain the hydrogen storage alloy. The integral composition of the metal raw material satisfies RExSmyNiz-a-b-cMnaAlbMc。
According to one embodiment of the present invention, a hydrogen storage alloy is prepared by the steps of: placing the metal raw materials into a vacuum melting furnace from bottom to top according to the sequence that the melting point is from large to small, but the rare earth metal is placed at the top (such as the top of a crucible of the vacuum melting furnace), and performing gas washing operation for 2-5 times by using inert gas; vacuumizing the vacuum melting furnace until the absolute vacuum degree is less than or equal to 50Pa, and filling inert gas until the relative vacuum degree is-0.01 to-0.1 MPa; heating a vacuum smelting furnace to 1200-1600 ℃, and stopping heating (about 10-60 min is needed) after the metal raw materials in the furnace are completely melted into molten metal; casting the molten metal to a cooling copper roller, and throwing the sheet into an alloy sheet with the thickness of 0.1-0.4 mm; placing the alloy sheet in an inert gas atmosphere with the absolute vacuum degree of 0.0001-0.05 PaAnd (3) performing heat treatment for 16-48 h at 850-1050 ℃ in a protected environment to obtain the hydrogen storage alloy. The whole composition of the metal raw material meets RExSmyNiz-a-b-cMnaAlbMc. The elements and their mole fractions are as described above and will not be described in detail here.
According to another embodiment of the present invention, a hydrogen occluding alloy is prepared by the steps of: placing metal raw materials into a vacuum smelting furnace according to the sequence that the melting point is from large to small and from the bottom to the upper part, and performing gas washing operation for 2-5 times by using inert gas when the rare earth element is at the uppermost part; vacuumizing the vacuum melting furnace until the absolute vacuum degree is less than or equal to 50Pa, and filling inert gas until the relative vacuum degree is-0.01 to-0.1 MPa; heating a vacuum smelting furnace to 1200-1600 ℃, and stopping heating (about 10-60 min is needed) after the metal raw materials in the furnace are completely melted into molten metal; casting the molten metal in a grinding tool to form an alloy ingot with the thickness of 5-25 mm, for example 15 mm; and (3) placing the alloy ingot in an environment with the absolute vacuum degree of 0.0001-0.05 Pa and the protection of inert gas, and carrying out heat treatment for 16-48 h at the temperature of 850-1050 ℃ to obtain the hydrogen storage alloy. The whole composition of the metal raw material meets RExSmyNiz-a-b-cMnaAlbMc. The elements and their mole fractions are as described above and will not be described in detail here.
In the present invention, the inert gas may be high-purity nitrogen or high-purity argon, preferably argon. Vacuumizing the vacuum melting furnace until the absolute vacuum degree is less than or equal to 50 Pa; preferably, the absolute vacuum degree is less than or equal to 20 Pa; more preferably, the absolute vacuum is 10Pa or less. Inert gas is filled into the vacuum smelting furnace until the relative vacuum degree is-0.01 to-0.1 MPa; preferably-0.02 to-0.08 MPa; more preferably-0.03 to-0.06 MPa.
In the invention, the vacuum melting furnace is heated to 1200-1600 ℃, preferably 1300-1500 ℃, and more preferably 1350-1500 ℃. And stopping heating after the metal raw materials in the furnace are completely melted, wherein the heating time is about 10-60 min, preferably 15-50 min, and more preferably 15-20 min. Such smelting conditions are advantageous in reducing the number of cycles required for complete activation of the electrode.
In the invention, molten metal is cast to a cooling copper roller, and the sheet is thrown into an alloy sheet with the thickness of 0.1-0.4 mm, preferably 0.15-0.35 mm, and more preferably 0.2-0.3 mm. And then placing the alloy sheet in an environment with the absolute vacuum degree of 0.0001-0.05 Pa and the protection of inert gas, and carrying out heat treatment for 16-48 h at the temperature of 850-1050 ℃ to obtain the hydrogen storage alloy. The absolute vacuum degree of the heat treatment may be 0.0001 to 0.05Pa, preferably 0.001 to 0.03Pa, and more preferably 0.01 to 0.02 Pa. The heat treatment temperature may be 850 to 1050 ℃, preferably 850 to 1000 ℃, and more preferably 850 to 900 ℃. The heat treatment time can be 16-48 h, preferably 16-36 h, and more preferably 20-25 h. Such heat treatment conditions are advantageous to reduce the number of cycles required for complete activation of the electrode.
< Hydrogen-absorbing alloy negative electrode >
The hydrogen storage alloy negative electrode comprises a current collector and a negative electrode material loaded on the current collector; the negative electrode material comprises a negative electrode active substance and a conductive agent, wherein the negative electrode active substance is the hydrogen storage alloy, and the chemical composition of the negative electrode active substance is RExSmyNiz-a-b-cMnaAlbMc. The elements and their mole fractions are as described above and will not be described in detail here.
The current collector of the present invention may employ metallic copper or nickel, etc., preferably nickel foam. The conductive agent can be nickel powder, acetylene black or graphite; preferably nickel powder; more preferably carbonyl nickel powder. The hydrogen occluding alloy is used in the form of powder. The particle size of the hydrogen storage alloy powder is 200-500 meshes, preferably 200-350 meshes, and more preferably 200-300 meshes. The ratio of the hydrogen storage alloy powder to the conductive agent can be 1: 3-8, preferably 1: 3-6, and more preferably 1: 3-5.
According to one embodiment of the present invention, a hydrogen storage alloy is crushed into alloy powder of 200 to 300 mesh; mixing the alloy powder and the carbonyl nickel powder in a mass ratio of 1: 3-5, and preparing an electrode slice with the diameter of 15-25 mm under 10-25 MPa (for example, 12 MPa); the electrode sheet is placed between two pieces of foamed nickel, and a nickel band serving as a tab is sandwiched therebetween, and a hydrogen storage alloy negative electrode (MH electrode) is manufactured under 10 to 25MPa (for example, 12MPa) again. And the close contact between the electrode plate and the nickel screen is ensured by spot welding around the electrode plate.
According to one embodiment of the present invention, a hydrogen storage alloy is mechanically crushed into 200 mesh alloy powder; mixing the alloy powder and the carbonyl nickel powder in a mass ratio of 1: 4, and preparing into an electrode slice with the diameter of 15mm under 12 MPa; the electrode sheet was placed between two pieces of foamed nickel while sandwiching a nickel tape as a tab, and the hydrogen storage alloy negative electrode (MH electrode) was produced again at 12 MPa. And the close contact between the electrode plate and the nickel screen is ensured by spot welding around the electrode plate.
< Battery >
The battery of the present invention is a nickel-hydrogen secondary battery. The battery comprises a battery shell, an electrode group and an alkaline electrolyte; the electrode group and the alkaline electrolyte are sealed in the battery shell; the electrode group comprises a positive electrode, a negative electrode and a diaphragm, wherein the negative electrode is the hydrogen storage alloy negative electrode.
The nickel-hydrogen secondary battery may be constructed in a sealed type structure. The battery case may be made of a material conventional in the art. The alkaline electrolyte of the nickel-hydrogen secondary battery may be an aqueous KOH solution, preferably an aqueous KOH solution with a small amount of LiOH added. The diaphragm can be porous vinylon non-woven fabric, nylon non-woven fabric, polyethylene fiber film and the like. The positive electrode can be nickel hydroxide, e.g., sintered Ni (OH) with excess capacity2a/NiOOH electrode.
Example 1
According to the formulation of Table 1, the metallic starting materials were placed in a vacuum melting furnace in the order of melting point from large to small and from bottom to top, but the rare earth metals were placed in the uppermost part of the crucible of the vacuum melting furnace, and the purging operation was performed 5 times with argon gas. And vacuumizing the vacuum melting furnace until the absolute vacuum degree is less than or equal to 5Pa, and filling argon until the relative vacuum degree is-0.05 MPa. The vacuum smelting furnace is heated to 1300 ℃, and the heating is stopped after the metal raw materials in the furnace are completely melted into molten metal, which takes about 20 min. And casting the molten metal to a cooling copper roller, and throwing the sheet into an alloy sheet with the thickness of 0.2 mm. And (3) placing the alloy sheet in an environment with the absolute vacuum degree of 0.01Pa and the protection of argon, and carrying out heat treatment at 850 ℃ for 20h to obtain the hydrogen storage alloy.
The maximum hydrogen storage capacity of the obtained hydrogen storage alloy under normal conditions can reach more than 1.36 wt%. The open cell made of the hydrogen storage alloy can complete activation after the first cycle of circulation, and has excellent high-rate discharge performance and less self-discharge.
Example 2
According to the formulation of Table 1, the metallic starting materials were placed in a vacuum melting furnace in the order of melting point from large to small and from bottom to top, but the rare earth metals were placed in the uppermost part of the crucible of the vacuum melting furnace, and the purging operation was performed 5 times with argon gas. And vacuumizing the vacuum melting furnace until the absolute vacuum degree is less than or equal to 5Pa, and filling argon until the relative vacuum degree is-0.05 MPa. The vacuum melting furnace is heated to 1300 ℃, and the heating is stopped after the metal raw materials in the furnace are completely melted, which takes about 20 min. And casting the molten metal to a cooling copper roller, and throwing the sheet into an alloy sheet with the thickness of 0.2 mm. And (3) placing the alloy sheet in an environment with the absolute vacuum degree of 0.01Pa and the protection of argon, and carrying out heat treatment for 16h at 950 ℃ to obtain the hydrogen storage alloy.
Examples 3 to 13
A hydrogen occluding alloy was prepared according to the formulation of Table 1 by the method of example 1.
Comparative example 1
A hydrogen occluding alloy was prepared by the method of example 1 using the formulation of example 20 of CN 101376941A.
Comparative example 2
A hydrogen occluding alloy was prepared by the method of example 1 using the formulation of example 1 of CN 109585790A.
Examples
The preparation method of the hydrogen storage alloy negative electrode is described as follows: and mechanically crushing the hydrogen storage alloy into alloy powder of 200-300 meshes. Mixing the alloy powder and the carbonyl nickel powder in a mass ratio of 1: 4, and preparing the mixture into an electrode slice with the diameter of 15mm under the pressure of 12 MPa. The electrode sheet was placed between two pieces of nickel foam, and a nickel tape as a tab was sandwiched, and a hydrogen storage alloy negative electrode (MH electrode) was produced at 12 MPa. And the close contact between the electrode plate and the nickel screen is ensured by spot welding around the electrode plate.
The preparation method of the electrode is described as follows: measuringThe negative electrode in the open three-electrode system for testing electrochemical performance is MH electrode, and the positive electrode adopts sintered Ni (OH) with excessive capacity2The NiOOH electrode, the reference electrode is Hg/HgO, and the electrolyte is 6 mol.L- 1KOH solution. The assembled battery was left for 24h and electrochemical performance was measured by a constant current method using a LAND cell tester. The test environment temperature was 303K. The charging current density is 60mA g-1The charging time was 7.5 hours, and the discharge current density was usually 60mA · g-1(unless otherwise stated), the discharge cut-off potential was 0.5V, and the charge/discharge pause time was 15 min.
TABLE 1
Remarking: n is the number of times of circulation required for complete activation of the alloy electrode; cmaxIs the maximum discharge capacity of the alloy electrode; HRD is the rate discharge performance expressed as the percentage of the discharge capacity at 300mA/g to the discharge capacity at 60 mA/g; SD72The capacity retention rate (self-discharge characteristic) after 72 hours of storage was obtained. Ml represents lanthanum rich misch metal containing 64 mol% La, 25 mol% Ce, 3 mol% Pr, 8 mol% Nd.
The present invention is not limited to the above-described embodiments, and any variations, modifications, and substitutions which may occur to those skilled in the art may be made without departing from the spirit of the invention.
Claims (9)
1. A hydrogen storage alloy, characterized in that it has a composition represented by formula (1):
RExSmyNiz-a-b-cMnaAlbMc (1)
wherein RE is selected from one or more elements of La, Ce, Pr, Nd, Gd and Sc;
wherein M is selected from one or more elements of Cu, Fe, Co, Sn, V, W, Cr, Zn, Mo and Si;
wherein x, y, z, a, b and c represent the mole fraction of each element;
wherein x is greater than 0, 5.9 is greater than y and is not less than 3.5, y/x is not less than 1.6, and x + y is 6; 22> z is more than or equal to 19; 2.5 is more than or equal to a + b and is more than 0; c is more than or equal to 3 and more than or equal to 0;
wherein the hydrogen storage alloy does not contain Mg.
2. A hydrogen occluding alloy as recited in claim 1, wherein y/x is 2.0 or more.
3. A hydrogen occluding alloy as recited in claim 1, wherein 3.0. gtoreq.y/x.gtoreq.2.0.
4. A hydrogen occluding alloy as recited in claim 1, wherein 3. gtoreq.x >0.1 and 4. gtoreq.y.gtoreq.3.5.
5. A hydrogen occluding alloy as recited in any one of claims 1 to 4, wherein 2.0. gtoreq.a + b. gtoreq.1.6.
6. The hydrogen storage alloy of claim 1, wherein the hydrogen storage alloy has a composition represented by one of the following formulas:
La2Sm4Ni19.4MnAl0.6；
La2Sm4Ni20MnAl0.6；
La2Sm4Ni20Mn；
La2Sm4Ni19.5Mn1.5；
La2Sm4Ni20Al；
La2Sm4Ni19.5Al1.5；
La2Sm4Ni19.5Mn0.5Al；
LaCeSm4Ni19MnAl；
Ml2Sm4Ni19MnAl；
La2Sm4Ni18.4MnAl0.6Cu；
La2Sm4Ni19.1Mn0.3Al0.6Fe；
La1.5Ce0.5Sm4Ni18.4Mn0.5Al0.6Co1.5；
wherein Ml represents lanthanum-rich mischmetal, containing 64 mol% of La, 25 mol% of Ce, 3 mol% of Pr and 8 mol% of Nd.
7. The method for producing a hydrogen occluding alloy as recited in any one of claims 1 to 6, wherein: placing metal raw materials into a vacuum melting furnace from large to small melting points and from bottom to upper part, placing rare earth metal at the uppermost part, and performing gas washing operation for 2-5 times by using inert gas; vacuumizing the vacuum melting furnace until the absolute vacuum degree is less than or equal to 50Pa, and filling inert gas until the relative vacuum degree is-0.01 to-0.1 MPa; heating a vacuum smelting furnace to 1200-1600 ℃, and stopping heating after the metal raw materials in the furnace are completely melted into molten metal; casting the molten metal to a cooling copper roller, and throwing the sheet into an alloy sheet with the thickness of 0.1-0.4 mm; placing the alloy sheet in an environment with the absolute vacuum degree of 0.0001-0.05 Pa and the protection of inert gas, and carrying out heat treatment for 16-48 h at the temperature of 850-1050 ℃ to obtain a hydrogen storage alloy; the overall composition of the metal feedstock satisfies formula (1).
8. The hydrogen storage alloy negative electrode is characterized by comprising a current collector and a negative electrode material loaded on the current collector; the negative electrode material comprises a negative electrode active material and a conductive agent, wherein the negative electrode active material is the hydrogen storage alloy as claimed in any one of claims 1 to 6.
9. A battery, comprising a battery case, an electrode group and an alkaline electrolyte; the electrode group and the alkaline electrolyte are sealed in the battery shell; the electrode group comprises a positive electrode, a negative electrode and a separator, and the negative electrode is the hydrogen storage alloy negative electrode according to claim 8.
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| CN103103380A (en) * | 2013-01-30 | 2013-05-15 | 广州有色金属研究院 | Samarium-containing praseodymium and neodymium-free hydrogen storage alloy for nickel-hydrogen power battery |
| CN104518204A (en) * | 2014-08-28 | 2015-04-15 | 包头稀土研究院 | Rare earth-yttrium-nickel family hydrogen storage alloy, and secondary battery containing hydrogen storage alloy |
| CN110714139A (en) * | 2018-07-13 | 2020-01-21 | 有研工程技术研究院有限公司 | Rare earth-nickel-based hydrogen storage alloy material and preparation method thereof |
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| CN103103380A (en) * | 2013-01-30 | 2013-05-15 | 广州有色金属研究院 | Samarium-containing praseodymium and neodymium-free hydrogen storage alloy for nickel-hydrogen power battery |
| CN104518204A (en) * | 2014-08-28 | 2015-04-15 | 包头稀土研究院 | Rare earth-yttrium-nickel family hydrogen storage alloy, and secondary battery containing hydrogen storage alloy |
| CN110714139A (en) * | 2018-07-13 | 2020-01-21 | 有研工程技术研究院有限公司 | Rare earth-nickel-based hydrogen storage alloy material and preparation method thereof |
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